Abstract: A single sideband modulator provides a means of translating low frequency baseband signals directly to radio frequency in a single stage. Such modulators, providing suppressed carrier and one or two of the sidebands, facilitates the transmission of intelligence with significantly increased gain over AM transmission. Control signals are continuously generated to keep the local oscillator breakthrough and image sidebands down to an insignificantly low level. This is achieved by monitoring amplitude of the RF output of the single sideband modulator, and comparing this with the baseband signals. By adjusting the d.c. offsets at the baseband inputs to the balanced modulators, carrier breakthrough is cancelled. By adjusting the relative phases of the baseband signals, deviations from the 90.degree. split are compensated. By changing the amplitude of one of the baseband signals, the level of one of the RF paths is adjusted to achieve amplitude balance.

Abstract: An upper and lower side-band generator comprised of a combination of combinational logic circuits. In a preferred embodiment the invention utilizes a substantially square wave sync output associated with carrier and modulator signal generators. A lower side-band signal is generated by synchronizing the transitions of a modulator signal with the transitions of a carrier signal, mixing the synchronized signal with the carrier signal, and filtering the resulting mixed signal. An upper side band signal is generated by synchronizing the carrier and modulator signals, delaying the resulting synchronized signal, and mixing the delayed, synchronized signal and the carrier signal.

Abstract: A system of transmission with amplitude modulation for the transmission of signals of all types, analog and/or digital, requiring high performance characteristics with respect to the noise induced by the transmission channel, comprising, at transmission, means for the suppressed carrier amplitude modulation of a useful signal and means for the amplitude modulation, in phase quadrature with said modulated useful signal, of a service signal, making it possible, at reception, to remove the ambiguity on the polarity of the demodulated useful signal. Thus it enables the transmission of signals in suppressed carrier modulation mode, hence with a good signal-to-noise ratio, without losing the polarity of the signal. The transmitters and receivers according to the invention also enable the transmission and reception of the signals modulated in SCAM, VSBAM or VSBSCAM modes.

Abstract: A digital amplitude modulation apparatus for amplitude-modulating a digital carrier having a frequency fc by a digital modulating wave associated with a sampling frequency fs1, at a sampling frequency fs2, wherein the conditions m.times.fs1=fs2, and fc=n/4.times. fs2 are satisfied, where m is a positive integer (2, 4, 6, . . . ) and n is a positive integer (1, 3, 5, . . . ). A fold distortion relative to an original digital amplitude modulated wave is not generated even if a fold component elimination filter is not used.

Abstract: Phase or frequency modulators which utilize phase generators rather than se shifters to produce low frequency input voltages to single side band modulators. Two phase generators are used to supply the two low frequency input ports of a single side band modulator of the 90.degree. phase shift/side band cancellation type, with the voltage dividers of one phase generator being adjusted so that its output is displaced 90.degree. in phase from the output of the other phase generator.

Abstract: In an SSB modulation/demodulation apparatus having a band-pass filter having a plurality of switchable bandwidths for restricting a signal transmission bandwidth, and a Hilbert converter constructed of a network having a pass band over all frequency ranges, the Hilbert converter is a digital Hilbert converter arranged to be set with switchable Hilbert conversion coefficients.

Abstract: An SSB generator in which a digitized analogue signal is processed in accordance with Weaver's method. The baseband I and Q signals are interpolated at a sampling frequency f.sub.s in respective first interpolators (30, 32). The interpolated signals are frequency up-converted to an output SSB carrier frequency Nf.sub.s by applying said signals to respective second interpolators (38, 40) in which the signals are sampled at 4Nf.sub.s. The samples at the outputs of the second interpolators (38, 40) are applied to a multiplexer (42) which provides a digitized version of the SSB signal which is converted to an analogue signal and filtered.

Abstract: The SSB modulator according to the present invention is comprised of a driving voltage generator, a diode, a bias supply circuit, an impedance transformation circuit and an input/output terminal. The SSB modulator is arranged such that the impedance of the diode is changed by changing the driving voltage impressed across the diode, resulting in the mismatching of the impedance, which leads to generation of a reflected wave. Therefore, by changing the amplitude and the phase of the above-obtained reflected wave, SSB modulation is effected. Accordingly, the SSB modulator of the present invention, requiring no particular side band filter, is compact in size, light in weight and low in manufacturing cost, with a simple structure of the circuit.