| 序号 | 专利名 | 申请号 | 申请日 | 公开（公告）号 | 公开（公告）日 | 发明人 |
|---|---|---|---|---|---|---|
| 41 | Technique for performing amplitude modulation without cheating side-bands | US955534 | 1997-10-22 | US6167241A | 2000-12-26 | Barry Thornton |
| A technique for amplitude modulating a carrier without producing side-bands is disclosed. In a preferred embodiment, a signal carrier is directly modulated and no energy side-bands are produced. This is accomplished by amplitude quantizing the data or information to be transmitted at the carrier rate or frequency and then resetting the amplitude of the carrier during one of the two 0-crossing times for each cycle of the carrier. | ||||||
| 42 | Method and apparatus for improving AM compatible digital broadcast analog fidelity | US671252 | 1996-06-27 | US5859876A | 1999-01-12 | Mark J. Dapper; Michael J. Geile; Barry Walter Carlin |
| A digital signal transmission system is provided which minimizes the AM signal envelope distortion caused by multiple digitally modulated carriers in the same band as the AM signal. The system transmits an amplitude modulated signal. Digital carriers for the digital signal are placed both above and below the frequency of the analog AM carrier. Certain digital carriers that are above the frequency of the analog AM carrier have an associated digital carrier that is at an equal frequency offset below the analog AM carrier. The data and modulation placed on the upper digital carrier and its counterpart are such that the signal resulting from their addition has no component that is in-phase with the analog AM carrier. The signal envelope is predistorted to counteract the distortion added by the digital carriers. | ||||||
| 43 | DC offset reduction in a transmitter | US735629 | 1996-10-23 | US5793817A | 1998-08-11 | John F. Wilson |
| A transmitter comprising at least first and second phase related signal paths, respective frequency up-converters, a combiner for combining the output of the respective frequency up-converters and for supplying the combined signal to a power amplifier. A feedback loop is provided which has a coupler for deriving a portion of the power amplifier output signal and supplying it to first and second phase related feedback paths. Each of the feedback paths comprises frequency down-converters. The dc offset is measured at the respective inputs of the frequency up-converters when the feedback around the linearization loop is reduced to zero without altering the dc offsets produced at the outputs of the frequency down-converters. Subtractors subtract the measured dc offsets from the feedback loop error signals. | ||||||
| 44 | Quadrature modular with adaptive suppression of carrier leakage | US174923 | 1993-12-29 | US5396196A | 1995-03-07 | James R. Blodgett |
| A carrier leakage suppression circuit is disclosed which adaptively suppresses carrier leakage in a signal processing device which modulates a carrier signal with an in-phase baseband signal and a quadrature baseband signal to generate a radio frequency (RF) output signal. The carrier leakage suppression circuit operates by imparting a first signature to the in-phase baseband signal and a second signature to the quadrature baseband signal prior to modulation of the carrier signal. In-phase and quadrature carrier leakage components in the RF output signal are isolated and measured by respectively correlating the RF output signal with the first and second signatures. An in-phase offset and a quadrature offset are generated as a function of the measurement of the in-phase and quadrature carrier leakage components. The in-phase baseband signal is combined with the in-phase offset and the quadrature baseband signal is combined with the quadrature offset to thereby suppress carrier leakage. | ||||||
| 45 | Special vestigial sideband signal for use in communication systems | US574388 | 1984-01-27 | US4660222A | 1987-04-21 | Stephen F. Smith |
| Several forms of a novel amplitude-modulated (AM) signal format are disclosed. Circuits of several types for generating the desired special vestigial-sideband (SVSB) AM waveforms are discussed. The principal form of the SVSB modulation provides for a reduction in transmitted signal bandwidth compared with standard double-sideband techniques plus very linear amplitude characteristics with simple synchronous detectors. Circuits according to the invention may also include means for dynamically varying signal bandwidth to accommodate special applications. | ||||||
| 46 | Suppressed carrier communications system | US427497 | 1982-09-29 | US4424593A | 1984-01-03 | Leonard R. Kahn |
| A radio transmission system of the suppressed carrier type incorporating means for correcting frequency errors. The transmission circuit can include the usual components which first produce a carrier wave, an upper sideband, and a lower sideband. The carrier wave and one of the sidebands are eliminated and only the desired sideband is radiated. The transmitter also incorporates a highly selective circuit which substantially reduces the amplitude of all audio frequencies below about 350 hertz. This frequency characteristic is used as a frequency reference to regenerate the carrier wave in the receiving system. Since low frequencies of 350 hertz are not present in voice waves at all instances, a storage circuit is employed to store a control voltage during the absence of low frequency sounds which would have the identifying frequency step. | ||||||
| 47 | Regulated suppressed carrier modulation system | US920048 | 1978-06-28 | US4243955A | 1981-01-06 | Sam M. Daniel; Kenneth M. Peterson |
| A method and apparatus for suppressing carrier leakage components in a system for modulating a carrier with a selected signal wherein the carrier and a quadrature component of the carrier are weighted and summed with the modulated carrier to produce a component substantially equal and opposite in phase to the leakage component so that the summing substantially cancels or suppresses the leakage component. | ||||||
| 48 | Carrier control system for suppressed carrier modulators | US768131 | 1977-02-14 | US4207525A | 1980-06-10 | Robert J. Martel; Walter Ewanus |
| A suppressed carrier radio signaling system is described in which there is a servo loop utilizing balanced circuit techniques and using the carrier as the reference, in which a phase detector (or coherent demodulator) constantly senses the phase difference between the carrier source and the carrier component in the output signal to derive an error signal which is used to vary the amount of the carrier component toward zero. | ||||||
| 49 | Adding frequency-modulated electrical signals | US3651410D | 1969-10-08 | US3651410A | 1972-03-21 | DAVIES ROBIN EVAN |
| Apparatus for generating an output signal the frequency of which is equal to the sum of the frequencies of two frequency-modulated input signals without demodulating the input signals is used in averaging two frequency-modulated signals and consists of a balanced mixer, and a band-pass filter and an amplitude limiter connected in series to the output of the mixer. The mixer consists of two transformers, two full-wave rectifiers and a differential amplifier connected to generate from two input signals A and B a signal A+B - A-B .
|
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| 50 | Double sideband suppressed carrier amplitude modulator | US80427559 | 1959-04-06 | US3026489A | 1962-03-20 | NATHAN GOLD |
| 51 | Regulator for carrier signal insertion circuit | US85531459 | 1959-11-25 | US2965857A | 1960-12-20 | BETTIN ROGER R; HERZOG WILLIAM E |
| 52 | Suppressed carrier modulator | US57216756 | 1956-03-16 | US2883625A | 1959-04-21 | SPARKS JR EARL C |
| 53 | Carrier suppressed modulator | US47504454 | 1954-12-14 | US2844798A | 1958-07-22 | SQUIRES WILLIAM K |
| 54 | Electric circuit | US15545450 | 1950-04-12 | US2561048A | 1951-07-17 | JAN BROUWER ALBERT |
| 55 | Modulator arrangement for carrier wave telegraphy and telephony | US63509845 | 1945-12-14 | US2443754A | 1948-06-22 | VALE KEITH R |
| 56 | Modulated oscillator | US39167641 | 1941-05-03 | US2298460A | 1942-10-13 | BOGHOSIAN WILLIAM H; HINSHAW FOSTER A; OCH HENRY G |
| 57 | High frequency transmission system | US20282638 | 1938-04-19 | US2283575A | 1942-05-19 | ROBERTS WALTER VAN B |
| 58 | Modulator | US19501138 | 1938-03-10 | US2201016A | 1940-05-14 | LINDLEY USSELMAN GEORGE |
| 59 | Oscillation generating and modulating device | US13914837 | 1937-04-27 | US2161406A | 1939-06-06 | CHARRIER GEORGE M |
| 60 | Signaling system | US6060736 | 1936-01-24 | US2108117A | 1938-02-15 | HENRI GARDERE; PAUL PAGES ANDRE |
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