An optical receiver has a pre-amplifier stage comprising an FET-FET cascode circuit. For coherent detection, an electrical local oscillator signal is applied to the gate of one of the FETs, the frequency of which is chosen to provide either homodyne demodulation, or a second IF signal. For direct detection the cascode consists of a dualgate FET, which is also the preferred form of cascode for coherent detection.

A phasing receiver includes a quadrature mixing arrangement for frequency converting an input or high IF information signal to a pair of quadrature related low IF signals. The low IF signals are applied to a polyphase filter which functions as a low pass and adjacent channel rejection filter. One or more elements effecting a fine adjustment of relative phase away from quadrature and/or relative amplitude away from equality of the low IF signals are incorporated in information or oscillator signa...

A receiver including an rf amplifier(14) having an input, an output and a gain control input(38), for deriving a gain control signal. A gain control (36) responsive to the gain control signal. The gain control (36) comprises at least 2 parallel arranged bias currents (40,42,44), at least one(42 or 44) of the 2 bias current means including switching means(SW1 or SW2) responsive to a control voltage varying by a predetermined amount relative to a reference voltage(V.sub.ref1 or V.sub.ref2) for act...

A plurality of M receivers are utilized to receive a plurality of N channels from various incoming multiplexed data signals, N.gtoreq.M, where each incoming data signal arrives on a separate wavelength and comprises several channels. Each of the M receivers, in sequence, receives a separate one of the N channels, thereby M of the N channels. The process then repeats for the next M channels, in the same sequence as the first M channels. The repetitions continue until all N channels are received.

An optical receiver incorporating a voltage dependant impedance arranged to shunt excess AC photodetector signal away from the receiver amplifier in response to light level.

A line scanning circuit for an electrostatically deflected cathode ray tube uses two integrator circuits having single transistor amplifiers for complementary conductivity types with capacitive feedback to provide balanced sawtooth drive waveforms. The charges on the capacitors are reset by pulses at line frequency and the forward sweeps of the sawteeth are produced by current flowing from the input of one integrator to the input of the other integrator. A variable resistor in the current path p...

A radio receiver comprising signal receiving means(10), means(12) for adjusting the amplitude of a signal received by said signal receiving means, a signal transmission system(32) coupled to said means for adjusting the signal amplitude, an agc feedback loop(38,42,40) coupled between an output of the signal transmission system and a control input of the signal amplitude adjusting means, the agc feedback loop comprising means for producing a multiple switched agc signal.

An optical receiver includes a reverse biassed photodiode whose output is coupled to a transimpedance amplifier. A load impedance for the photodiode comprises a forward biassed semiconductor diode, enabling the photodiode to be biassed using a low voltage supply. A signal compressing arrangement can be provided between the transimpedance amplifier output and the semiconductor diode on the side thereof remote from the photodiode. The transimpedance amplifier can have a capacitive transimpedance e...

A transmitter/receiver adapted for contemporaneous operation in the transmit and receive mode utilizing a single carrier frequency whereby single frequency duplex operation is achieved.

A television receiver equipped for the display of data transmitted during the line flyback period and also for the display of data transmitted over the telephone via a modem is provided with circuitry for detecting the absence of the normal television synchronizing signals and for providing internal synchronizing to enable the continuance of the display of data.