The HP 200A , first built in 1938, was the first product made by Hewlett-Packard and was manufactured in David Packard 's garage in Palo Alto, California .
121-467: It was a low-distortion audio oscillator used for testing sound equipment. It used the Wien bridge oscillator circuit, that had been the subject of Bill Hewlett 's masters thesis. It was also the first such commercial oscillator to use a simple light bulb as the temperature-dependent resistor in its feedback network. The light bulb was an inexpensive and effective automatic gain control that not only kept
242-430: A feedback loop ; an amplifier A {\displaystyle A} and an electronic filter β ( j ω ) {\displaystyle \beta (j\omega )} . The filter's purpose is to limit the frequencies that can pass through the loop so the circuit only oscillates at the desired frequency. Since the filter and wires in the circuit have resistance they consume energy and
363-610: A magnitude and an angle, the above equation actually consists of two conditions: Equations (1) and (2) are called the Barkhausen stability criterion . It is a necessary but not a sufficient criterion for oscillation, so there are some circuits which satisfy these equations that will not oscillate. An equivalent condition often used instead of the Barkhausen condition is that the circuit's closed loop transfer function (the circuit's complex impedance at its output) have
484-444: A square , sawtooth or triangle wave . It consists of an energy-storing element (a capacitor or, more rarely, an inductor ) and a nonlinear switching device (a latch , Schmitt trigger , or negative resistance element) connected in a feedback loop . The switching device periodically charges the storage element with energy and when its voltage or current reaches a threshold discharges it again, thus causing abrupt changes in
605-430: A triangle wave , powered by a direct current (DC) source. Oscillators are found in many electronic devices, such as radio receivers , television sets , radio and television broadcast transmitters , computers , computer peripherals , cellphones , radar , and many other devices. Oscillators are often characterized by the frequency of their output signal: There are two general types of electronic oscillators:
726-458: A trimmer capacitor in series or parallel with the crystal. The Barkhausen criterion above, eqs. (1) and (2), merely gives the frequencies at which steady-state oscillation is possible, but says nothing about the amplitude of the oscillation, whether the amplitude is stable, or whether the circuit will start oscillating when the power is turned on. For a practical oscillator two additional requirements are necessary: A typical rule of thumb
847-400: A basic mobile phone, which is only capable of voice calling and text messaging. Feature phones and basic mobile phones tend to use a proprietary, custom-designed software and user interface . By contrast, smartphones generally use a mobile operating system that often shares common traits across devices. The critical advantage that modern cellular networks have over predecessor systems is
968-434: A customer unit could use. A cellular network mobile phone system gets its name from dividing the service area into many small cells, each with a base station with (for example) a useful range on the order of a kilometer (mile). These systems have dozens or hundreds of possible channels allocated to them. When a subscriber is using a given channel for a telephone connection, that frequency is unavailable for other customers in
1089-406: A dynamo, what would now be called a parametric oscillator . The arc oscillator was rediscovered and popularized by William Duddell in 1900. Duddell, a student at London Technical College, was investigating the hissing arc effect. He attached an LC circuit (tuned circuit) to the electrodes of an arc lamp, and the negative resistance of the arc excited oscillation in the tuned circuit. Some of
1210-447: A feedback oscillator circuit will oscillate, the feedback loop is thought of as broken at some point (see diagrams) to give an input and output port (for accuracy, the output port must be terminated with an impedance equal to the input port). A sine wave is applied to the input v i ( t ) = V i e j ω t {\displaystyle v_{i}(t)=V_{i}e^{j\omega t}} and
1331-418: A few sets of radio channels (frequencies). Once these few channels were in use by customers, no further customers could be served until another user vacated a channel. It would be impractical to give every customer a unique channel since there would not be enough bandwidth allocated to the mobile service. As well, technical limitations such as antenna efficiency and receiver design limit the range of frequencies
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#17327834449611452-506: A fixed-location phone ( landline phone ). The radio frequency link establishes a connection to the switching systems of a mobile phone operator , which provides access to the public switched telephone network (PSTN). Modern mobile telephone services use a cellular network architecture, and therefore mobile telephones are called cellphones (or "cell phones") in North America. In addition to telephony , digital mobile phones support
1573-401: A gain of 1+R f /R b and with a high input impedance. R 1 , R 2 , C 1 and C 2 form a bandpass filter which is connected to provide positive feedback at the frequency of oscillation. R b self heats and increases the negative feedback which reduces the amplifier gain until the point is reached that there is just enough gain to sustain sinusoidal oscillation without over driving
1694-401: A given phase change Δ ϕ {\displaystyle \Delta \phi } depends on the slope of the loop phase curve at ω 0 {\displaystyle \omega _{0}} , which is determined by the Q {\displaystyle Q} RC oscillators have the equivalent of a very low Q {\displaystyle Q} , so
1815-523: A mobile device, such as a smartphone. The term "app" is a shortening of the term "software application". A common data application on mobile phones is Short Message Service (SMS) text messaging. The first SMS message was sent from a computer to a mobile phone in 1992 in the UK while the first person-to-person SMS from phone to phone was sent in Finland in 1993. The first mobile news service, delivered via SMS,
1936-546: A nonlinear electronic oscillator model, the Van der Pol oscillator , was done by Balthasar van der Pol in 1927. He originated the term "relaxation oscillation" and was first to distinguish between linear and relaxation oscillators. He showed that the stability of the oscillations ( limit cycles ) in actual oscillators was due to the nonlinearity of the amplifying device. Further advances in mathematical analysis of oscillation were made by Hendrik Wade Bode and Harry Nyquist in
2057-401: A number of distinguishing features. The International Telecommunication Union measures those with Internet connection, which it calls Active Mobile-Broadband subscriptions (which includes tablets, etc.). In the developed world, smartphones have now overtaken the usage of earlier mobile systems. However, in the developing world, they account for around 50% of mobile telephony . Feature phone
2178-406: A pair of poles on the imaginary axis . In general, the phase shift of the feedback network increases with increasing frequency so there are only a few discrete frequencies (often only one) which satisfy the second equation. If the amplifier gain A {\displaystyle A} is high enough that the loop gain is unity (or greater, see Startup section) at one of these frequencies,
2299-501: A problem due to the design of the phone, the quality of the cellular network and compression algorithms used in long-distance calls . Audio quality can be improved using a VoIP application over WiFi . Cellphones have small speakers so that the user can use a speakerphone feature and talk to a person on the phone without holding it to their ear. The small speakers can also be used to listen to digital audio files of music or speech or watch videos with an audio component, without holding
2420-474: A protracted legal battle over the rights to the "regenerative" oscillator circuit which has been called "the most complicated patent litigation in the history of radio". De Forest ultimately won before the Supreme Court in 1934 on technical grounds, but most sources regard Armstrong's claim as the stronger one. The first and most widely used relaxation oscillator circuit, the astable multivibrator ,
2541-407: A resistance that increases with temperature as the current through them increases. As the amplitude of the signal current through them increases during oscillator startup, the increasing resistance of these devices reduces the loop gain. The essential characteristic of all these circuits is that the nonlinear gain-control circuit must have a long time constant , much longer than a single period of
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#17327834449612662-542: A ring of active delay stages, such as inverters . Generally the ring has an odd number of inverting stages, so that there is no single stable state for the internal ring voltages. Instead, a single transition propagates endlessly around the ring. Some of the more common relaxation oscillator circuits are listed below: An oscillator can be designed so that the oscillation frequency can be varied over some range by an input voltage or current. These voltage controlled oscillators are widely used in phase-locked loops , in which
2783-560: A role in the invention of the oscillator. In the summer of 1912, Edwin Armstrong observed oscillations in audion radio receiver circuits and went on to use positive feedback in his invention of the regenerative receiver . Austrian Alexander Meissner independently discovered positive feedback and invented oscillators in March 1913. Irving Langmuir at General Electric observed feedback in 1913. Fritz Lowenstein may have preceded
2904-464: A single hand, since most thumbs cannot reach the entire screen surface; they may need to be shifted around in the hand, held in one hand and manipulated by the other, or used in place with both hands. Due to design advances, some modern smartphones with large screen sizes and "edge-to-edge" designs have compact builds that improve their ergonomics, while the shift to taller aspect ratios have resulted in phones that have larger screen sizes whilst maintaining
3025-517: A single platform. There are a huge variety of apps, including video games , music products and business tools. Up until that point, smartphone application distribution depended on third-party sources providing applications for multiple platforms, such as GetJar , Handango , Handmark , and PocketGear . Following the success of the App Store, other smartphone manufacturers launched application stores, such as Google's Android Market (later renamed to
3146-429: A small microchip called a Subscriber Identity Module or SIM card , in order to function. The SIM card is approximately the size of a small postage stamp and is usually placed underneath the battery in the rear of the unit. The SIM securely stores the service-subscriber key (IMSI) and the K i used to identify and authenticate the user of the mobile phone. The SIM card allows users to change phones by simply removing
3267-485: A small change in frequency. Therefore, the circuit's oscillation frequency is very close to the natural resonant frequency of the tuned circuit , and doesn't depend much on other components in the circuit. The quartz crystal resonators used in crystal oscillators have even higher Q {\displaystyle Q} (10 to 10 ) and their frequency is very stable and independent of other circuit components. The frequency of RC and LC oscillators can be tuned over
3388-471: A telephone service area, which is divided up into 'cells'. Each cell uses a different set of frequencies from neighboring cells, and will typically be covered by three towers placed at different locations. The cell towers are usually interconnected to each other and the phone network and the internet by wired connections. Due to bandwidth limitations each cell will have a maximum number of cell phones it can handle at once. The cells are therefore sized depending on
3509-431: A ubiquitous audio generator in engineering laboratories worldwide from the 1950s to the 1990s. William R. Hewlett 's Wien bridge oscillator can be considered as a combination of a differential amplifier and a Wien bridge , connected in a positive feedback loop between the amplifier output and differential inputs. At the oscillating frequency, the bridge is almost balanced and has very small transfer ratio. The loop gain
3630-652: A variety of other services , such as text messaging , multimedia messaging , email , Internet access (via LTE , 5G NR or Wi-Fi ), short-range wireless communications ( infrared , Bluetooth ), satellite access ( navigation , messaging connectivity ), business applications, payments (via NFC ), multimedia playback and streaming ( radio , television ), digital photography , and video games . Mobile phones offering only basic capabilities are known as feature phones ( slang : "dumbphones" ); mobile phones that offer greatly advanced computing capabilities are referred to as smartphones . The first handheld mobile phone
3751-469: A very thin carbon microphone". Early predecessors of cellular phones included analog radio communications from ships and trains. The race to create truly portable telephone devices began after World War II, with developments taking place in many countries. The advances in mobile telephony have been traced in successive "generations", starting with the early zeroth-generation ( 0G ) services, such as Bell System 's Mobile Telephone Service and its successor,
HP 200A - Misplaced Pages Continue
3872-411: A vibrating quartz crystal . Crystal oscillators are ubiquitous in modern electronics, being the source for the clock signal in computers and digital watches, as well as a source for the signals generated in radio transmitters and receivers. As a crystal oscillator's “native” output waveform is sinusoidal , a signal-conditioning circuit may be used to convert the output to other waveform types, such as
3993-425: A wide range by using variable components in the filter. A microwave cavity can be tuned mechanically by moving one of the walls. In contrast, a quartz crystal is a mechanical resonator whose resonant frequency is mainly determined by its dimensions, so a crystal oscillator's frequency is only adjustable over a very narrow range, a tiny fraction of one percent. It's frequency can be changed slightly by using
4114-498: Is "almost" an oscillator; it can store energy in the form of electronic oscillations if excited, but because it has electrical resistance and other losses the oscillations are damped and decay to zero. The negative resistance of the active device cancels the (positive) internal loss resistance in the resonator, in effect creating a resonator circuit with no damping, which generates spontaneous continuous oscillations at its resonant frequency . The negative-resistance oscillator model
4235-414: Is a product of the very high amplifier gain and the very low bridge ratio. In Hewlett's circuit, the amplifier is implemented by two vacuum tubes. The amplifier's inverting input is the cathode of tube V 1 and the non-inverting input is the control grid of tube V 2 . To simplify analysis, all the components other than R 1 , R 2 , C 1 and C 2 can be modeled as a non-inverting amplifier with
4356-412: Is a term typically used as a retronym to describe mobile phones which are limited in capabilities in contrast to a modern smartphone . Feature phones typically provide voice calling and text messaging functionality, in addition to basic multimedia and Internet capabilities, and other services offered by the user's wireless service provider . A feature phone has additional functions over and above
4477-513: Is being used or not) using a technique known as multilateration to calculate the differences in time for a signal to travel from the mobile phone to each of several cell towers near the owner of the phone. The movements of a mobile phone user can be tracked by their service provider and, if desired, by law enforcement agencies and their governments. Both the SIM card and the handset can be tracked. China has proposed using this technology to track
4598-431: Is not limited to one-port devices like diodes; feedback oscillator circuits with two-port amplifying devices such as transistors and tubes also have negative resistance. At high frequencies, three terminal devices such as transistors and FETs are also used in negative resistance oscillators. At high frequencies these devices do not need a feedback loop, but with certain loads applied to one port can become unstable at
4719-400: Is often used in the feedback loop that provides a 'slow' gain reduction with amplitude. This stabilizes the loop gain at an amplitude below the saturation level of the amplifier, so it does not saturate and "clip" the sine wave. Resistor-diode networks and FETs are often used for the nonlinear element. An older design uses a thermistor or an ordinary incandescent light bulb ; both provide
4840-409: Is to make the small signal loop gain at the oscillation frequency 2 or 3. When the power is turned on, oscillation is started by the power turn-on transient or random electronic noise present in the circuit. Noise guarantees that the circuit will not remain "balanced" precisely at its unstable DC equilibrium point ( Q point ) indefinitely. Due to the narrow passband of the filter, the response of
4961-468: The 5G NR (5G New Radio) standard. 5G can be implemented in low-band, mid-band or high-band millimeter-wave, with download speeds that can achieve gigabit-per-second (Gbit/s) range, aiming for a network latency of 1 ms. This near-real-time responsiveness and improved overall data performance are crucial for applications like online gaming , augmented and virtual reality , autonomous vehicles , IoT, and critical communication services. Smartphones have
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5082-648: The Improved Mobile Telephone Service . These 0G systems were not cellular , supported a few simultaneous calls, and were very expensive. The first handheld cellular mobile phone was demonstrated by John F. Mitchell and Martin Cooper of Motorola in 1973, using a handset weighing 2 kilograms (4.4 lb). The first commercial automated cellular network ( 1G ) analog was launched in Japan by Nippon Telegraph and Telephone in 1979. This
5203-888: The Philippines . A pilot project in Bali was launched in 2011 by the International Finance Corporation and an Indonesian bank, Bank Mandiri . Mobile payments were first trialled in Finland in 1998 when two Coca-Cola vending machines in Espoo were enabled to work with SMS payments. Eventually, the idea spread and in 1999, the Philippines launched the country's first commercial mobile payments systems with mobile operators Globe and Smart . Some mobile phones can make mobile payments via direct mobile billing schemes, or through contactless payments if
5324-649: The WCDMA standard. This was followed by 3.5G or 3G+ enhancements based on the high-speed packet access (HSPA) family, allowing UMTS networks to have higher data transfer speeds and capacity. 3G is able to provide mobile broadband access of several Mbit/s to smartphones and mobile modems in laptop computers. This ensures it can be applied to mobile Internet access, VoIP , video calls, and sending large e-mail messages, as well as watching videos, typically in standard-definition quality. By 2009, it had become clear that, at some point, 3G networks would be overwhelmed by
5445-450: The internet of things (IoT), fixed wireless access , and multimedia streaming (including music, video, radio , and television ). Deployment of fifth-generation ( 5G ) cellular networks commenced worldwide in 2019. The term "5G" was originally used in research papers and projects to denote the next major phase in mobile telecommunication standards beyond the 4G / IMT-Advanced standards. The 3GPP defines 5G as any system that adheres to
5566-403: The linear or harmonic oscillator , and the nonlinear or relaxation oscillator . The two types are fundamentally different in how oscillation is produced, as well as in the characteristic type of output signal that is generated. The most-common linear oscillator in use is the crystal oscillator , in which the output frequency is controlled by a piezo-electric resonator consisting of
5687-414: The microwave range and above, since at these frequencies feedback oscillators perform poorly due to excessive phase shift in the feedback path. In negative-resistance oscillators, a resonant circuit, such as an LC circuit , crystal , or cavity resonator , is connected across a device with negative differential resistance , and a DC bias voltage is applied to supply energy. A resonant circuit by itself
5808-599: The screen . Depending on the device's type and design, the screen fills most or nearly all of the space on a device's front surface. Many smartphone displays have an aspect ratio of 16:9 , but taller aspect ratios became more common in 2017. Screen sizes are often measured in diagonal inches or millimeters ; feature phones generally have screen sizes below 90 millimetres (3.5 in). Phones with screens larger than 130 millimetres (5.2 in) are often called " phablets ." Smartphones with screens over 115 millimetres (4.5 in) in size are commonly difficult to use with only
5929-464: The square wave typically utilized in computer clock circuits. Linear or harmonic oscillators generate a sinusoidal (or nearly-sinusoidal) signal. There are two types: The most common form of linear oscillator is an electronic amplifier such as a transistor or operational amplifier connected in a feedback loop with its output fed back into its input through a frequency selective electronic filter to provide positive feedback . When
6050-449: The tank circuit in LC oscillators will cause the oscillation frequency to change, so for a constant frequency these components must have stable values. How stable the oscillator's frequency is to other changes in the circuit, such as changes in values of other components, gain of the amplifier, the load impedance, or the supply voltage, is mainly dependent on the Q factor ("quality factor") of
6171-415: The 1930s. In 1969 Kaneyuki Kurokawa derived necessary and sufficient conditions for oscillation in negative-resistance circuits, which form the basis of modern microwave oscillator design. Mobile phone A mobile phone or cell phone is a portable telephone that can make and receive calls over a radio frequency link while the user is moving within a telephone service area, as opposed to
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#17327834449616292-528: The 19th century. The current through an arc light is unstable due to its negative resistance , and often breaks into spontaneous oscillations, causing the arc to make hissing, humming or howling sounds which had been noticed by Humphry Davy in 1821, Benjamin Silliman in 1822, Auguste Arthur de la Rive in 1846, and David Edward Hughes in 1878. Ernst Lecher in 1888 showed that the current through an electric arc could be oscillatory. An oscillator
6413-535: The Barkhausen criterion, at which point the amplitude levels off and steady state operation is achieved, with the output a slightly distorted sine wave with peak amplitude determined by the supply voltage. This is a stable equilibrium; if the amplitude of the sine wave increases for some reason, increased clipping of the output causes the loop gain | A β ( j ω 0 ) | {\displaystyle |A\beta (j\omega _{0})|} to drop below one temporarily, reducing
6534-520: The DC voltage across the varactor changes its capacitance , which changes the resonant frequency of the tuned circuit. Voltage controlled relaxation oscillators can be constructed by charging and discharging the energy storage capacitor with a voltage controlled current source . Increasing the input voltage increases the rate of charging the capacitor, decreasing the time between switching events. A feedback oscillator circuit consists of two parts connected in
6655-595: The GSM was used by over 5 billion people in over 220 countries. The GSM (2G) has evolved into 3G, 4G and 5G. The standardization body for GSM started at the CEPT Working Group GSM (Group Special Mobile) in 1982 under the umbrella of CEPT. In 1988, ETSI was established, and all CEPT standardization activities were transferred to ETSI. Working Group GSM became Technical Committee GSM. In 1991, it became Technical Committee SMG (Special Mobile Group) when ETSI tasked
6776-493: The Google Play Store), RIM's BlackBerry App World , or Android-related app stores like Aptoide , Cafe Bazaar , F-Droid , GetJar , and Opera Mobile Store . In February 2014, 93% of mobile developers were targeting smartphones first for mobile app development. As of 2022, the top five manufacturers worldwide were Samsung (21%), Apple (16%), Xiaomi (13%), Oppo (10%), and Vivo (9%). From 1983 to 1998, Motorola
6897-714: The SIM card from one mobile phone and inserting it into another mobile phone or broadband telephony device, provided that this is not prevented by a SIM lock . The first SIM card was made in 1991 by Munich smart card maker Giesecke & Devrient for the Finnish wireless network operator Radiolinja . A hybrid mobile phone can hold up to four SIM cards, with a phone having a different device identifier for each SIM Card. SIM and R-UIM cards may be mixed together to allow both GSM and CDMA networks to be accessed. From 2010 onwards, such phones became popular in emerging markets, and this
7018-421: The UK, the total number of mobile phones overtook the number of houses in 1999. Today, mobile phones are globally ubiquitous, and in almost half the world's countries, over 90% of the population owns at least one. A handheld mobile radio telephone service was envisioned in the early stages of radio engineering. In 1917, Finnish inventor Eric Tigerstedt filed a patent for a "pocket-size folding telephone with
7139-578: The ability to transfer cash payments by secure SMS text message. Kenya's M-PESA mobile banking service, for example, allows customers of the mobile phone operator Safaricom to hold cash balances which are recorded on their SIM cards. Cash can be deposited or withdrawn from M-PESA accounts at Safaricom retail outlets located throughout the country and can be transferred electronically from person to person and used to pay bills to companies. Branchless banking has also been successful in South Africa and
7260-550: The abnormally high traffic. Capacity was further increased when phone companies implemented digital networks. With digital, one frequency can host multiple simultaneous calls. Additionally, short-range Wi-Fi infrastructure is often used by smartphones as much as possible as it offloads traffic from cell networks on to local area networks. The common components found on all mobile phones are: Low-end mobile phones are often referred to as feature phones and offer basic telephony. Handsets with more advanced computing ability through
7381-674: The active device can no longer be considered a 'pure gain', and it will contribute some phase shift to the loop. An alternate mathematical stability test sometimes used instead of the Barkhausen criterion is the Nyquist stability criterion . This has a wider applicability than the Barkhausen, so it can identify some of the circuits which pass the Barkhausen criterion but do not oscillate. Temperature changes, other environmental changes, aging, and manufacturing tolerances will cause component values to "drift" away from their designed values. Changes in frequency determining components such as
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#17327834449617502-497: The active device itself, such as the interelectrode capacitance between output and input, make the device unstable. The input impedance of the active device falls with frequency, so it may load the feedback network. As a result, stable feedback oscillators are difficult to build for frequencies above 500 MHz, and negative resistance oscillators are usually used for frequencies above this. The first practical oscillators were based on electric arcs , which were used for lighting in
7623-399: The amplifier. If R 1 = R 2 and C 1 = C 2 then at equilibrium R f /R b = 2 and the amplifier gain is 3. When the circuit is first energized, the lamp is cold and the gain of the circuit is greater than 3 which ensures start up. The dc bias current of vacuum tube V1 also flows through the lamp. This does not change the principles of the circuit's operation, but it does reduce
7744-407: The amplifying device, the transistor , vacuum tube or op-amp . The maximum voltage swing of the amplifier's output is limited by the DC voltage provided by its power supply. Another possibility is that the output may be limited by the amplifier slew rate . As the amplitude of the output nears the power supply voltage rails, the amplifier begins to saturate on the peaks (top and bottom) of
7865-433: The amplifying device, the amplifier will act as a pure gain A {\displaystyle A} , but if the oscillation frequency ω 0 {\displaystyle \omega _{0}} is near the amplifier's cutoff frequency ω C {\displaystyle \omega _{C}} , within 0.1 ω C {\displaystyle 0.1\omega _{C}} ,
7986-497: The amplitude and phase of the sine wave after going through the loop v o = V o e j ( ω t + ϕ ) {\displaystyle v_{o}=V_{o}e^{j(\omega t+\phi )}} is calculated Since in the complete circuit v o {\displaystyle v_{o}} is connected to v i {\displaystyle v_{i}} , for oscillations to exist The ratio of output to input of
8107-519: The amplitude becomes large enough that the amplifier becomes nonlinear , generating harmonic distortion, technically the frequency domain analysis used in normal amplifier circuits is no longer applicable, so the "gain" of the circuit is undefined. However the filter attenuates the harmonic components produced by the nonlinearity of the amplifier, so the fundamental frequency component sin ω 0 t {\displaystyle \sin \omega _{0}t} mainly determines
8228-401: The amplitude of the output at equilibrium because the bias current provides part of the heating of the lamp. This electronics-related article is a stub . You can help Misplaced Pages by expanding it . Audio oscillator An electronic oscillator is an electronic circuit that produces a periodic, oscillating or alternating current (AC) signal, usually a sine wave , square wave or
8349-467: The amplitude of the signal drops as it passes through the filter. The amplifier is needed to increase the amplitude of the signal to compensate for the energy lost in the other parts of the circuit, so the loop will oscillate, as well as supply energy to the load attached to the output. To determine the frequency(s) ω 0 = 2 π f 0 {\displaystyle \omega _{0}\;=\;2\pi f_{0}} at which
8470-961: The benefits of different calling plans. For example, a particular plan might provide for cheaper local calls, long-distance calls, international calls, or roaming. The mobile phone has been used in a variety of diverse contexts in society. For example: In 1998, one of the first examples of distributing and selling media content through the mobile phone was the sale of ringtones by Radiolinja in Finland. Soon afterwards, other media content appeared, such as news, video games, jokes, horoscopes, TV content and advertising. Most early content for mobile phones tended to be copies of legacy media , such as banner advertisements or TV news highlight video clips. Recently, unique content for mobile phones has been emerging, from ringtones and ringback tones to mobisodes , video content that has been produced exclusively for mobile phones. In many countries, mobile phones are used to provide mobile banking services, which may include
8591-469: The call, from detecting the presence of a handset in a service area, temporary assignment of a channel to a handset making a call, interface with the land-line side of the network to connect to other subscribers, and collection of billing information for the service. The automation systems can control the "hand off" of a customer handset moving between one cell and another so that a call in progress continues without interruption, changing channels if required. In
8712-400: The circuit to a noise pulse will be sinusoidal, it will excite a small sine wave of voltage in the loop. Since for small signals the loop gain is greater than one, the amplitude of the sine wave increases exponentially. During startup, while the amplitude of the oscillation is small, the circuit is approximately linear , so the analysis used in the Barkhausen criterion is applicable. When
8833-410: The circuit will oscillate at that frequency. Many amplifiers such as common-emitter transistor circuits are "inverting", meaning that their output voltage decreases when their input increases. In these the amplifier provides 180° phase shift , so the circuit will oscillate at the frequency at which the feedback network provides the other 180° phase shift. At frequencies well below the poles of
8954-399: The clock rate (generally given in multiples of hertz ) but also the memory hierarchy also greatly affects overall performance. Because of these problems, the performance of mobile phone CPUs is often more appropriately given by scores derived from various standardized tests to measure the real effective performance in commonly used applications. One of the main characteristics of phones is
9075-407: The committee with UMTS (3G). In addition to transmitting voice over digital signals, the 2G network introduced data services for mobile, starting with SMS text messages, then expanding to Multimedia Messaging Service (MMS), and mobile internet with a theoretical maximum transfer speed of 384 kbit/s (48 kB/s). In 2001, the third-generation ( 3G ) was launched in Japan by NTT DoCoMo on
9196-421: The components. Since at high frequencies the tank circuit has very small capacitance and inductance, parasitic capacitance and parasitic inductance of component leads and PCB traces become significant. These may create unwanted feedback paths between the output and input of the active device, creating instability and oscillations at unwanted frequencies ( parasitic oscillation ). Parasitic feedback paths inside
9317-435: The concept of frequency reuse allowing many simultaneous telephone conversations in a given service area. This allows efficient use of the limited radio spectrum allocated to mobile services, and lets thousands of subscribers converse at the same time within a given geographic area. Former systems would cover a service area with one or two powerful base stations with a range of up to tens of kilometers' (miles), using only
9438-490: The detailed shape of the output waveform, electronic circuit simulation computer programs like SPICE are used. A typical design procedure for oscillator circuits is to use linear techniques such as the Barkhausen stability criterion or Nyquist stability criterion to design the circuit, use a rule of thumb to choose the loop gain, then simulate the circuit on computer to make sure it starts up reliably and to determine
9559-415: The earliest mobile phone systems by contrast, all control was done manually; the customer would search for an unoccupied channel and speak to a mobile operator to request connection of a call to a landline number or another mobile. At the termination of the call the mobile operator would manually record the billing information. Mobile phones communicate with cell towers that are placed to give coverage across
9680-496: The end of 2009. In 2014, there were more than seven billion mobile phone subscribers worldwide, a number that is expected to keep growing. Mobile phones are used for a variety of purposes, such as keeping in touch with family members, for conducting business, and in order to have access to a telephone in the event of an emergency. Some people carry more than one mobile phone for different purposes, such as for business and personal use. Multiple SIM cards may be used to take advantage of
9801-567: The energy was radiated as sound waves by the arc, producing a musical tone. Duddell demonstrated his oscillator before the London Institute of Electrical Engineers by sequentially connecting different tuned circuits across the arc to play the national anthem " God Save the Queen ". Duddell's "singing arc" did not generate frequencies above the audio range. In 1902 Danish physicists Valdemar Poulsen and P. O. Pederson were able to increase
9922-531: The ergonomics associated with smaller 16:9 displays. Liquid-crystal displays are the most common; others are IPS , LED , OLED , and AMOLED displays. Some displays are integrated with pressure-sensitive digitizers, such as those developed by Wacom and Samsung , and Apple's " 3D Touch " system. In sound, smartphones and feature phones vary little. Some audio-quality enhancing features, such as Voice over LTE and HD Voice , have appeared and are often available on newer smartphones. Sound quality can remain
10043-420: The expected usage density, and may be much smaller in cities. In that case much lower transmitter powers are used to avoid broadcasting beyond the cell. In order to handle the high traffic, multiple towers can be set up in the same area (using different frequencies). This can be done permanently or temporarily such as at special events or in disasters. Cell phone companies will bring a truck with equipment to host
10164-431: The feedback filter. Since the amplitude of the output is constant due to the nonlinearity of the amplifier (see Startup section below), changes in component values cause changes in the phase shift ϕ = ∠ A β ( j ω ) {\displaystyle \phi \;=\;\angle A\beta (j\omega )} of the feedback loop. Since oscillation can only occur at frequencies where
10285-441: The feedback loop: In addition to the feedback oscillators described above, which use two-port amplifying active elements such as transistors and operational amplifiers, linear oscillators can also be built using one-port (two terminal) devices with negative resistance , such as magnetron tubes, tunnel diodes , IMPATT diodes and Gunn diodes . Negative-resistance oscillators are usually used at high frequencies in
10406-486: The first quarter of 2016, the top smartphone developers worldwide were Samsung , Apple and Huawei ; smartphone sales represented 78 percent of total mobile phone sales. For feature phones as of 2016 , the top-selling brands were Samsung, Nokia and Alcatel . Mobile phones are considered an important human invention as they have been one of the most widely used and sold pieces of consumer technology. The growth in popularity has been rapid in some places, for example, in
10527-606: The frequency produced into the radio range by operating the arc in a hydrogen atmosphere with a magnetic field, inventing the Poulsen arc radio transmitter , the first continuous wave radio transmitter, which was used through the 1920s. The vacuum-tube feedback oscillator was invented around 1912, when it was discovered that feedback ("regeneration") in the recently invented audion (triode) vacuum tube could produce oscillations. At least six researchers independently made this discovery, although not all of them can be said to have
10648-599: The growth of bandwidth-intensive applications, such as streaming media . Consequently, the industry began looking to data-optimized fourth-generation ( 4G ) technologies, with the promise of speed improvements up to tenfold over existing 3G technologies. The first publicly available LTE service was launched in Scandinavia by TeliaSonera in 2009. In the 2010s, 4G technology has found diverse applications across various sectors, showcasing its versatility in delivering high-speed wireless communication, such as mobile broadband,
10769-632: The influence of European companies had significantly decreased due to fierce competition from American and Asian companies, to where most technical innovation had shifted. Apple and Google, both of the United States, also came to dominate mobile phone software. The world's largest individual mobile operator by number of subscribers is China Mobile , which has over 902 million mobile phone subscribers as of June 2018 . Over 50 mobile operators have over ten million subscribers each, and over 150 mobile operators had at least one million subscribers by
10890-414: The local cell and in the adjacent cells. However, cells further away can re-use that channel without interference as the subscriber's handset is too far away to be detected. The transmitter power of each base station is coordinated to efficiently service its own cell, but not to interfere with the cells further away. Automation embedded in the customer's handset and in the base stations control all phases of
11011-422: The loop gain (this is the " harmonic balance " analysis technique for nonlinear circuits). The sine wave cannot grow indefinitely; in all real oscillators some nonlinear process in the circuit limits its amplitude, reducing the gain as the amplitude increases, resulting in stable operation at some constant amplitude. In most oscillators this nonlinearity is simply the saturation (limiting or clipping ) of
11132-430: The loop, v o v i = A β ( j ω ) {\displaystyle {v_{o} \over v_{i}}=A\beta (j\omega )} , is called the loop gain . So the condition for oscillation is that the loop gain must be one Since A β ( j ω ) {\displaystyle A\beta (j\omega )} is a complex number with two parts,
11253-557: The narrow bandwidth of the crystal removes the harmonics from the output, producing a 'pure' sinusoidal wave with almost no distortion even with large loop gains. Since oscillators depend on nonlinearity for their operation, the usual linear frequency domain circuit analysis techniques used for amplifiers based on the Laplace transform , such as root locus and gain and phase plots ( Bode plots ), cannot capture their full behavior. To determine startup and transient behavior and calculate
11374-419: The nonlinear aspects of operation such as harmonic distortion. Component values are tweaked until the simulation results are satisfactory. The distorted oscillations of real-world (nonlinear) oscillators are called limit cycles and are studied in nonlinear control theory . In applications where a 'pure' very low distortion sine wave is needed, such as precision signal generators , a nonlinear component
11495-470: The oscillation. Therefore, over a single cycle they act as virtually linear elements, and so introduce very little distortion. The operation of these circuits is somewhat analogous to an automatic gain control (AGC) circuit in a radio receiver. The Wein bridge oscillator is a widely used circuit in which this type of gain stabilization is used. At high frequencies it becomes difficult to physically implement feedback oscillators because of shortcomings of
11616-449: The oscillator output amplitude constant, but it also kept the oscillator's loop gain near unity. The latter is a key technique for achieving a low distortion oscillator. Earlier, Larned Meacham had used light bulbs in bridge circuits to stabilize and linearize oscillators in 1938. The product code was chosen to give the impression that HP was an established company. A variation, the HP 200B,
11737-430: The oscillator's frequency can be locked to the frequency of another oscillator. These are ubiquitous in modern communications circuits, used in filters , modulators , demodulators , and forming the basis of frequency synthesizer circuits which are used to tune radios and televisions. Radio frequency VCOs are usually made by adding a varactor diode to the tuned circuit or resonator in an oscillator circuit. Changing
11858-426: The other port and show negative resistance due to internal feedback. The negative resistance port is connected to a tuned circuit or resonant cavity, causing them to oscillate. High-frequency oscillators in general are designed using negative-resistance techniques. Some of the many harmonic oscillator circuits are listed below: A nonlinear or relaxation oscillator produces a non-sinusoidal output, such as
11979-418: The others with a crude oscillator in late 1911. In Britain, H. J. Round patented amplifying and oscillating circuits in 1913. In August 1912, Lee De Forest , the inventor of the audion, had also observed oscillations in his amplifiers, but he didn't understand the significance and tried to eliminate it until he read Armstrong's patents in 1914, which he promptly challenged. Armstrong and De Forest fought
12100-480: The output of the amplifier can no longer increase with increasing input, further increases in amplitude cause the equivalent gain of the amplifier and thus the loop gain to decrease. The amplitude of the sine wave, and the resulting clipping, continues to grow until the loop gain is reduced to unity, | A β ( j ω 0 ) | = 1 {\displaystyle |A\beta (j\omega _{0})|\;=\;1\,} , satisfying
12221-520: The output waveform. Although in the past negative resistance devices like the unijunction transistor , thyratron tube or neon lamp were used, today relaxation oscillators are mainly built with integrated circuits like the 555 timer IC . Square-wave relaxation oscillators are used to provide the clock signal for sequential logic circuits such as timers and counters , although crystal oscillators are often preferred for their greater stability. Triangle-wave or sawtooth oscillators are used in
12342-409: The phase changes very slowly with frequency, therefore a given phase change will cause a large change in the frequency. In contrast, LC oscillators have tank circuits with high Q {\displaystyle Q} (~10 ). This means the phase shift of the feedback network increases rapidly with frequency near the resonant frequency of the tank circuit. So a large change in phase causes only
12463-463: The phase shift is a multiple of 360°, ϕ = 360 n ∘ {\displaystyle \phi \;=\;360n^{\circ }} , shifts in component values cause the oscillation frequency ω 0 {\displaystyle \omega _{0}} to change to bring the loop phase back to 360n°. The amount of frequency change Δ ω {\displaystyle \Delta \omega } caused by
12584-399: The phone and the point of sale support near field communication (NFC). Enabling contactless payments through NFC-equipped mobile phones requires the co-operation of manufacturers, network operators, and retail merchants. Mobile phones are commonly used to collect location data. While the phone is turned on, the geographical location of a mobile phone can be determined easily (whether it
12705-567: The phone close to the ear. The average phone battery lasts two–three years at best. Many of the wireless devices use a Lithium-Ion (Li-Ion) battery, which charges 500–2500 times, depending on how users take care of the battery and the charging techniques used. It is only natural for these rechargeable batteries to chemically age, which is why the performance of the battery when used for a year or two will begin to deteriorate. Battery life can be extended by draining it regularly, not overcharging it, and keeping it away from heat. Mobile phones require
12826-401: The power supply to the amplifier is switched on initially, electronic noise in the circuit provides a non-zero signal to get oscillations started. The noise travels around the loop and is amplified and filtered until very quickly it converges on a sine wave at a single frequency. Feedback oscillator circuits can be classified according to the type of frequency selective filter they use in
12947-552: The second-generation ( 2G ) digital cellular technology was launched in Finland by Radiolinja on the GSM standard. This sparked competition in the sector as the new operators challenged the incumbent 1G network operators. The GSM standard is a European initiative expressed at the CEPT ("Conférence Européenne des Postes et Telecommunications", European Postal and Telecommunications conference). The Franco-German R&D cooperation demonstrated
13068-411: The sine wave's amplitude back to its unity-gain value. Similarly if the amplitude of the wave decreases, the decreased clipping will cause the loop gain to increase above one, increasing the amplitude. The amount of harmonic distortion in the output is dependent on how much excess loop gain the circuit has: An exception to the above are high Q oscillator circuits such as crystal oscillators ;
13189-409: The sine wave, flattening or " clipping " the peaks. To achieve the maximum amplitude sine wave output from the circuit, the amplifier should be biased midway between its clipping levels. For example, an op amp should be biased midway between the two supply voltage rails. A common-emitter transistor amplifier's collector voltage should be biased midway between cutoff and saturation levels. Since
13310-401: The technical feasibility, and in 1987, a Memorandum of Understanding was signed between 13 European countries that agreed to launch a commercial service by 1991. The first version of the GSM standard had 6,000 pages. The IEEE and RSE awarded Thomas Haug and Philippe Dupuis the 2018 James Clerk Maxwell medal for their contributions to the first digital mobile telephone standard. In 2018,
13431-553: The timebase circuits that generate the horizontal deflection signals for cathode-ray tubes in analogue oscilloscopes and television sets. They are also used in voltage-controlled oscillators (VCOs), inverters and switching power supplies , dual-slope analog to digital converters (ADCs), and in function generators to generate square and triangle waves for testing equipment. In general, relaxation oscillators are used at lower frequencies and have poorer frequency stability than linear oscillators. Ring oscillators are built of
13552-614: The tube. The first of these was the Barkhausen–Kurz oscillator (1920), the first tube to produce power in the UHF range. The most important and widely used were the klystron (R. and S. Varian, 1937) and the cavity magnetron (J. Randall and H. Boot, 1940). Mathematical conditions for feedback oscillations, now called the Barkhausen criterion , were derived by Heinrich Georg Barkhausen in 1921. He also showed that all linear oscillators must have negative resistance. The first analysis of
13673-699: The use of native software applications are known as smartphones . The first GSM phones and many feature phones had NOR flash memory, from which processor instructions could be executed directly in an execute in place architecture and allowed for short boot times. With smartphones, NAND flash memory was adopted as it has larger storage capacities and lower costs, but causes longer boot times because instructions cannot be executed from it directly, and must be copied to RAM memory first before execution. Mobile phones have central processing units (CPUs), similar to those in computers, but optimised to operate in low power environments. Mobile CPU performance depends not only on
13794-412: Was attributed to the desire to obtain the lowest calling costs. When the removal of a SIM card is detected by the operating system, it may deny further operation until a reboot. Feature phones have basic software platforms. Smartphones have advanced software platforms. Android OS has been the best-selling OS worldwide on smartphones since 2011. A mobile app is a computer program designed to run on
13915-406: Was built by Elihu Thomson in 1892 by placing an LC tuned circuit in parallel with an electric arc and included a magnetic blowout. Independently, in the same year, George Francis FitzGerald realized that if the damping resistance in a resonant circuit could be made zero or negative, the circuit would produce oscillations, and, unsuccessfully, tried to build a negative resistance oscillator with
14036-544: Was customized for Walt Disney , which bought eight units for use in the production of Fantasia . The circuit diagram is shown in Hewlett's 1939 patent. Through the 1940s and into the 1950s, the subsequent versions of the 200A covered different and wider frequency ranges. The latest version was the 200CD. It covered from the subaudio 5 Hz to the low end (Long Wave) of the AM radio band at 600 kilohertz. The 200CD became
14157-587: Was demonstrated by Martin Cooper of Motorola in New York City on 3 April 1973, using a handset weighing c. 2 kilograms (4.4 lbs). In 1979, Nippon Telegraph and Telephone (NTT) launched the world's first cellular network in Japan. In 1983, the DynaTAC 8000x was the first commercially available handheld mobile phone. From 1983 to 2014, worldwide mobile phone subscriptions grew to over seven billion; enough to provide one for every person on Earth. In
14278-555: Was followed in 1981 by the simultaneous launch of the Nordic Mobile Telephone (NMT) system in Denmark, Finland, Norway, and Sweden. Several other countries then followed in the early to mid-1980s. These first-generation ( 1G ) systems could support far more simultaneous calls but still used analog cellular technology. In 1983, the DynaTAC 8000x was the first commercially available handheld mobile phone. In 1991,
14399-646: Was invented in 1917 by French engineers Henri Abraham and Eugene Bloch. They called their cross-coupled, dual-vacuum-tube circuit a multivibrateur , because the square-wave signal it produced was rich in harmonics , compared to the sinusoidal signal of other vacuum-tube oscillators. Vacuum-tube feedback oscillators became the basis of radio transmission by 1920. However, the triode vacuum tube oscillator performed poorly above 300 MHz because of interelectrode capacitance. To reach higher frequencies, new "transit time" (velocity modulation) vacuum tubes were developed, in which electrons traveled in "bunches" through
14520-455: Was launched in Finland in 2000, and subsequently many organizations provided "on-demand" and "instant" news services by SMS. Multimedia Messaging Service (MMS) was introduced in March 2002. The introduction of Apple's App Store for the iPhone and iPod Touch in July 2008 popularized manufacturer-hosted online distribution for third-party applications (software and computer programs) focused on
14641-508: Was market leader in mobile phones. Nokia was the market leader in mobile phones from 1998 to 2012. In Q1 2012, Samsung surpassed Nokia, selling 93.5 million units as against Nokia's 82.7 million units. Samsung has retained its top position since then. Aside from Motorola, European brands such as Nokia, Siemens and Ericsson once held large sway over the global mobile phone market, and many new technologies were pioneered in Europe. By 2010,
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