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24-455: Using circuitry developed by Motorola , C-QUAM uses quadrature amplitude modulation (QAM) to encode the stereo separation signal . This extra signal is then stripped down in such a way that it is compatible with the envelope detector of older receivers, hence the name C-QUAM for Compatible. A 25 Hz pilot tone is added to trigger receivers ; unlike its counterpart in FM radio , this carrier

48-694: A digital circuit , or a mixed-signal circuit (a combination of analog circuits and digital circuits). The most widely used semiconductor device in electronic circuits is the MOSFET (metal–oxide–semiconductor field-effect transistor ). Analog electronic circuits are those in which current or voltage may vary continuously with time to correspond to the information being represented. The basic components of analog circuits are wires, resistors, capacitors, inductors, diodes , and transistors . Analog circuits are very commonly represented in schematic diagrams , in which wires are shown as lines, and each component has

72-411: A field-effect transistor can be modeled as a current source from the source to the drain, with the current controlled by the gate-source voltage. When the circuit size is comparable to a wavelength of the relevant signal frequency, a more sophisticated approach must be used, the distributed-element model . Wires are treated as transmission lines, with nominally constant characteristic impedance , and

96-543: A consequence, extremely complex digital circuits, with billions of logic elements integrated on a single silicon chip, can be fabricated at low cost. Such digital integrated circuits are ubiquitous in modern electronic devices, such as calculators, mobile phone handsets, and computers. As digital circuits become more complex, issues of time delay, logic races , power dissipation, non-ideal switching, on-chip and inter-chip loading, and leakage currents, become limitations to circuit density, speed and performance. Digital circuitry

120-669: A dual IF bandwidth setup, for an extended audio frequency response over mono receivers. Providing for a full, rich stereo sound is simply not possible with digital audio encoding. The down side of analog broadcasting is the amount of unwanted noise. Introduction to the Motorola C-QUAM AM Stereo System [1] Circuitry An electronic circuit is composed of individual electronic components , such as resistors , transistors , capacitors , inductors and diodes , connected by conductive wires or traces through which electric current can flow. It

144-429: A receiver, analog circuitry is used to amplify and frequency-convert signals so that they reach a suitable state to be converted into digital values, after which further signal processing can be performed in the digital domain. In electronics , prototyping means building an actual circuit to a theoretical design to verify that it works, and to provide a physical platform for debugging it if it does not. The prototype

168-483: A unique symbol. Analog circuit analysis employs Kirchhoff's circuit laws : all the currents at a node (a place where wires meet), and the voltage around a closed loop of wires is 0. Wires are usually treated as ideal zero-voltage interconnections; any resistance or reactance is captured by explicitly adding a parasitic element, such as a discrete resistor or inductor. Active components such as transistors are often treated as controlled current or voltage sources: for example,

192-481: Is a type of electrical circuit. For a circuit to be referred to as electronic , rather than electrical , generally at least one active component must be present. The combination of components and wires allows various simple and complex operations to be performed: signals can be amplified, computations can be performed, and data can be moved from one place to another. Circuits can be constructed of discrete components connected by individual pieces of wire, but today it

216-449: Is known as static random-access memory (SRAM). Memory based on the storage of charge in a capacitor, dynamic random-access memory (DRAM), is also widely used.) The design process for digital circuits is fundamentally different from the process for analog circuits. Each logic gate regenerates the binary signal, so the designer need not account for distortion, gain control, offset voltages, and other concerns faced in an analog design. As

240-495: Is much more common to create interconnections by photolithographic techniques on a laminated substrate (a printed circuit board or PCB) and solder the components to these interconnections to create a finished circuit. In an integrated circuit or IC, the components and interconnections are formed on the same substrate, typically a semiconductor such as doped silicon or (less commonly) gallium arsenide . An electronic circuit can usually be categorized as an analog circuit ,

264-664: Is not amplitude modulated, it is phase modulated, and is made up of both a L+R input and a L-R input. To recover the 'stereo' audio signals, a synchronous detector extracts the L-R audio from the phase modulated quadrature portion of the signal created in stage 2. The L+R audio can be extracted from either the AM (stage 1) or the PM (stage 2) modulation component. From there, the audio can be readily de-multiplexed (de-muxed) back to 'stereo', a.k.a. Left and Right channels. For additional information, see

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288-451: Is not necessary for the reconstruction of the original audio sources. The C-QUAM signal is composed of two distinct modulation stages: a conventional AM version and a compatible quadrature PM version. Stage 1 provides the transmitter with a summed L+R mono audio input. This input is precisely the same as conventional AM-Mono transmission methods and ensures 100% compatibility with conventional 'envelope detector' receivers. Stage 2 provides

312-450: Is often constructed using techniques such as wire wrapping or using a breadboard , stripboard or perfboard , with the result being a circuit that is electrically identical to the design but not physically identical to the final product. Open-source tools like Fritzing exist to document electronic prototypes (especially the breadboard-based ones) and move toward physical production. Prototyping platforms such as Arduino also simplify

336-665: Is used to create general purpose computing chips, such as microprocessors , and custom-designed logic circuits, known as application-specific integrated circuit (ASICs). Field-programmable gate arrays (FPGAs), chips with logic circuitry whose configuration can be modified after fabrication, are also widely used in prototyping and development. Mixed-signal or hybrid circuits contain elements of both analog and digital circuits. Examples include comparators , timers , phase-locked loops , analog-to-digital converters , and digital-to-analog converters . Most modern radio and communications circuitry uses mixed signal circuits. For example, in

360-520: The impedances at the start and end determine transmitted and reflected waves on the line. Circuits designed according to this approach are distributed-element circuits . Such considerations typically become important for circuit boards at frequencies above a GHz; integrated circuits are smaller and can be treated as lumped elements for frequencies less than 10GHz or so. In digital electronic circuits , electric signals take on discrete values, to represent logical and numeric values. These values represent

384-1011: The ionosphere ), an effect known as selective fading , very unpleasant effects result; hence, the C-QUAM system is not often if ever used for shortwave broadcasting, nor by stations which receive a great deal of skywave interference. As of March 2014, there are still a number of AM radio stations in North America broadcasting in C-QUAM stereo. Among those stations are WXYG /540: Sauk Rapids, MN; CFCB /570: Corner Brook, NL; CFCO /630: Chatham, Ontario (covering SW Ontario, Eastern Michigan and Northern Ohio); WNMB /900: North Myrtle Beach, South Carolina ; WBLQ /1230: Westerly , Rhode Island ; WIRY /1340: Plattsburgh, New York; WAXB /850: Ridgefield, Connecticut and WYLD-AM /940: New Orleans, Louisiana. In addition to FCC-Licensed C-QUAM AM broadcast stations, low-powered (<100 mW) Part 15 C-QUAM stereo transmitters are available for sale for use in

408-537: The AM band, but with significant digital artifact and aliasing due to substantial codec inadequacy. In addition, C-QUAM patents have expired. iBiquity still controls IBOC intellectual property through patents, through licensing fees for both the use of the technology, and any modifications to be made, even if the broadcaster in question has purchased the equipment outright and made costly modifications to their transmitter plant in order to implement it. Very few AM radio stations that broadcast with IBOC HD Radio during

432-553: The United States. In Rome, Italy, there is Broadcastitalia on 1485 kHz. Also see: While C-QUAM is an accepted international standard for AM Radio broadcasting, it is incompatible with the IBOC (In-band on-channel) "HD" (Hybrid Digital) radio system, so a broadcaster must choose what system they will use. The IBOC system allows transmission of an audio frequency range extending to approximately 15 kHz, 2-ch Stereo on

456-447: The attached PDF: "Introduction to the Motorola C-QUAM AM Stereo System". C-QUAM is not perfect, however, in large part because pre- AMAX it exhibited platform motion , with the audio "center" rocking back and forth as if changing the balance knob. This effect is potentially bothersome, especially in a moving vehicle where the received signal changes rapidly, and occupants (particularly the driver) would be more prone to its effects (this

480-434: The day switch to C-QUAM AM Stereo during nighttime operation to reduce sideband digital (hash) interference and to provide long-range stereo reception. A number of HD radio tuners have the limited ability to decode C-Quam stereo transmissions, (typically with lower bandwidth), and as a result, reduced audio quality than what could be expected from a specifically designed AMAX/C-QUAM only tuner. C-QUAM AM Stereo transmissions have

504-820: The information that is being processed. In the vast majority of cases, binary encoding is used: one voltage (typically the more positive value) represents a binary '1' and another voltage (usually a value near the ground potential, 0 V) represents a binary '0'. Digital circuits make extensive use of transistors , interconnected to create logic gates that provide the functions of Boolean logic : AND, NAND, OR, NOR, XOR and combinations thereof. Transistors interconnected so as to provide positive feedback are used as latches and flip flops, circuits that have two or more metastable states, and remain in one of these states until changed by an external input. Digital circuits therefore can provide logic and memory, enabling them to perform arbitrary computational functions. (Memory based on flip-flops

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528-465: The same range as AM Monural transmission, a key benefit. Whereas many stations in the late 2000s changed from C-QUAM to HD Radio, in the 2010s the trend reversed with many HD Radio stations shutting off their digital equipment. However, few of these stations returned to C-QUAM broadcasts. There has been a move to bring back C-QUAM in the last few years, due to the poor sound quality of digital audio encoding at low bit rates. Where AM stereo receivers use

552-414: The stereo multiplexed (muxed) audio input and replaces the conventional crystal oscillator stage of otherwise AM-Mono transmitters. So as to not create interference with 'envelope detector' receivers, the stage 2 signal takes the multiplexed (muxed) audio signals and phase modulates both, using a divide-by-4 Johnson counter and two balanced modulators operating 90 degrees out of phase with each other. Stage 2

576-409: Was an effect that happened primarily with skywave signals. Groundwave or local coverage usually did not suffer from this issue). This has been alleviated in subsequent revisions. Also, since some stereo information is contained in the sidebands , adjacent channel interference can cause problems. Finally, when only part of a sideband is attenuated (as often happens to skywave signals reflecting off

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