Abstract: A single-sideband generator comprising a 90-degree phase shifter to which a modulating signal is applied, a modulator, and a switching circuit for alternately switching the delayed and nondelayed modulating signals to the modulator at a rate corresponding to the frequency of a carrier. A frequency divider is provided for halving the frequency of the carrier and applying its output to the modulator to cause it to modulate the divider output with the output of the switching circuit. In a preferred embodiment, the modulator comprises a balanced modulator.

Abstract: A system for transmitting television signals on a radio link. The system includes a transmitter having a modulator for modulating a carrier signal to produce a vestigial sideband amplitude modulated signal for transmission. The modulator includes a first converter for converting the frequency of video signals to an intermediate frequency and a second converter for converting the intermediate frequency of the video signals to a radio frequency. The system further includes a receiver having a demodulator for demodulating a received vestigial sideband amplitude modulated signal. The modulator includes a Nyquist filter connected between the first and second converters, and the demodulator includes a filter having a rectangular characteristic for processing the signal to be demodulated.

Abstract: A transmitter for single-sideband broadcast transmission which operates in accordance with the principle of combined amplitude and phase modulation generating a single-sideband signal and splitting this signal into an amplitude-modulated component applied to an amplitude-modulated path and a phase-modulated component applied to a phase-modulated path. An amplitude-modulation path is a D.C. voltage-coupled signal path from an envelope-curve detector to a radio-frequency amplifier (2). This results in direct floating-carrier modulation in a radio frequency amplifier in which the amplitude-modulated and phase-modulated components are amplified and recombined.

Abstract: A trigonometric transform function generator provides a signal which is either the sine or cosine function of an inputted information signal. The function generator can be used in an FM system or in a new system of transform modulation, wherein the transform functions are used to derive the original information signal.

Abstract: A compressed single side band communication system and method in which the audio signal is compressed prior to pre-emphasis and thereafter summed with a pilot tone for further compression prior to transmission. Initially, only the pilot tone is transmitted at full rated power to aid in acquisition of the signal by the receiver. Thereafter, the transmitter ALC is disabled and the pilot tone is attenuated. The receiver adjusts the frequency characteristics of the pilot tone filter and phase lock loop filter in the detector as a function of lock-on. The delay after loss of lock-on in reverting to wide band pilot tone and wideband loop filters is varied as a function of signal strength. The pilot tone may be modulated for tone coded squelch. The modulating source is located in the return end of the phase lock loop filter. A unique filter is provided to insure acquisition of the pilot tone.

Abstract: A method of predistortion alignment of a single sideband transmission system in which the receiver becomes a part of the signal path which is predistorted, to providing improved overall intermodulation distortion. A convenient method of performing the alignment under field conditions is disclosed.

Abstract: A transmitted signal includes a pilot signal at a given frequency and an information signal occupying a different band of frequencies. A noise reduction system for a signal receiver detects modulation on the pilot signal and generates a signal having a frequency that varies in response to the detected modulation. The system includes an apparatus for combining the received signal with the generated signal to produce a signal at another frequency with reduced frequency noise.

Abstract: A method for measuring oscillator spillover noise produced by a single sideband microwave radio is provided. A white noise signal filtered by a narrow notch filter having a bandwidth on the order of the spillover bandwidth is applied as a modulating input. The white noise signal filtered by wide notch filter is also applied as a modulating input. After demodulation, noise measurements are made in the narrow and wide notches. Because the wide notch contains practically no oscillator spillover noise near its center, the noise measured there can be subtracted from that measured in the narrow notch to provide a figure for the oscillator spillover noise. Idle noise can be subtracted from the wide notch noise value to provide a measure of intermodulation distortion.

Abstract: A compressed single side band communication system and method in which the audio signal is compressed prior to pre-emphasis and thereafter summed with a pilot tone for further compression prior to transmission. Initally, only the pilot tone is transmitted at full rated power to aid in acquisition of the signal by the receiver. Thereafter, the transmitter ALC is disabled and the pilot tone is attenuated. The receiver adjusts the frequency characteristics of the pilot tone filter and phase lock loop filter in the detector as a function of lock-on. The delay after loss of lock-on in reverting to wide band pilot tone and wideband loop filters is varied as a function of signal strength. The pilot tone may be modulated for tone coded squelch. The modulating source is located in the return end of the phase lock loop filter. A unique filter is provided to insure acquisition of the pilot tone.

Abstract: A single carrier is amplitude-modulated by a signal which is a transform (as the sine function) of the audio signal, and one set of sidebands is removed. In a receiver, the signal can be recovered by first deriving the Hilbert transform of the sine transform, and multiplying it by the signum of the derivative of the original audio signal to obtain the cosine transform. The sine and cosine transforms are then decoded to obtain the original audio signal.

Abstract: The present invention relates to a frequency-hopped single sideband (SSB) mobile radio system implemented by hopping the carrier frequency of an input signal (s(t)) every .tau. seconds. The hopping is controlled by a carrier-frequency-hopped sequence (f.sub.i (t)) generated by a carrier-frequency-hopping generator (16,24). When employed in a frequency-hopped SSB transmitter (10), the carrier sequence functions to modulate the input signal, "hopping" it to a different carrier frequency every .tau. seconds. The carrier-frequency-hopped SSB receiver (20) employs the identical carrier sequence as used by the transmitter to demodulate the transmitted carrier-frequency-hopped SSB signal, thereby recovering the original single sideband signal (s(t)). By frequency hopping the carrier signal of an SSB signal, the present invention mitigates the effects of co-channel interference and frequency selective fading inherent in prior art SSB cellular mobile radio systems.

Abstract: 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.

Abstract: Single sideband modulation system. A first single sideband of radio frequency is generated with first audio modulation on the lower side of an assigned frequency, the first single sideband bandwidth being equal to the highest frequency of said first audio modulation. A second single sideband of radio frequency is generated with second audio modulation on the upper side of the assigned frequency, the second single sideband bandwidth being equal to the highest frequency of said second audio modulation. A first stereo channel is modulated on the lower sideband frequency. A second stereo channel is modulated on the upper sideband frequency. The stereo channels are combined whereby a receiver tuned to the assigned non-transmitted carrier frequency will receive both stereo channels.

Abstract: A system for single sideband modulation, and a method implemented by the system. The system includes a double sideband, suppressed carrier modulator and a phase locked loop circuit receiving the output of the modulator and tuned to lock to one of the sidebands of the modulator output. The phase locked loop circuit produces an output having a constant amplitude, but otherwise tracking the signal contained in the one sideband. The output of the phase locked loop is processed by an amplifier having a controllable gain. Open and closed loop circuits are provided for deriving the amplitude of the signal contained in the one sideband. The latter amplitude is imparted to the output of the phase locked loop by using the signal amplitude to control the gain of the amplifier.

Abstract: A directional radio system with single sideband operation for the transmission of a carrier frequency modulated single sideband signal in the intermediate frequency plane. In the transmitter, the intermediate frequency signal which contains the base band is provided with at least two pilot signals of different frequency and in the receiver a tuning criterion for the mixing oscillator of the receiver is derived from the frequency spacing of the received pilot signals and from the frequency shift of the received pilot signals produced by transmission of same over the radio links.