Abstract: An AM receiver incorporates an antenna, a transistor, a current source, and a power supply. The antenna is connected to a gate electrode of the transistor and through a link to a signal earth. In operation, the antenna receives radiation and generates a corresponding input signal which propagates to the gate electrode. The transistor is operable to process the input signal in two steps, namely to reflectively amplify the input signal to generate a correspondingly reflectively amplified input signal at the gate electrode in a first step, and amplitude demodulate the amplified input signal in a second step. The transistor is operable in a non-linear region of its current/voltage characteristic whereas it simultaneously provides reflective amplification and signal demodulation, namely the two steps occur simultaneously.

Abstract: An AM receiver incorporates an antenna, a transistor, a current source, and a power supply. The antenna is connected to a gate electrode of the transistor and through a link to a signal earth. In operation, the antenna receives radiation and generates a corresponding input signal which propagates to the gate electrode. The transistor is operable to process the input signal in two steps, namely to reflectively amplify the input signal to generate a correspondingly reflectively amplified input signal at the gate electrode in a first step, and amplitude demodulate the amplified input signal in a second step. The transistor is operable in a non-linear region of its current/voltage characteristic whereas it simultaneously provides reflective amplification and signal demodulation, namely the two steps occur simultaneously.

Abstract: A modulator circuit comprises a negative impedance amplifier which is operable such that a signal applied to the amplifier is reflected and amplified. Switching circuitry is provided for switching the impedance of the amplifier between two reflecting states such that the reflected and amplified signal is phase modulated. The impedances of the negative impedance amplifier are selected such that the phase of the reflected and amplified signal switches by substantially 180°. Preferably, the impedances of the negative impedance amplifier in the two reflecting states are selected such that the reflection gain of the amplifier in the two reflecting states is substantially the same such that the reflected and amplified signal is a binary phase shift keyed.

Abstract: A multimode transceiver circuit comprises a four port coupler of a type which splits a signal applied to one port between two of the other ports. The split signals are phase shifted by a known amount. A first port of the coupler is for receiving a signal and for outputting a signal therefrom. A controllable oscillator is connected to a second port of the coupler and switchable impedances (Schottky diodes) are connected to the remaining ports. A controller is provided for controlling the operation of the oscillator and the impedances to determine the mode of operation of the circuit. In one mode of operation, the oscillator is inoperative and at least one of the impedances is switched to operate as a non-linear impedance such that the circuit detects amplitude-modulation of the signal applied to the first port.