Antenna coupling amplifier and converter system

An amplifier and down converter system for coupling an antenna output to a receiver, comprising:

• a low-noise receiving amplifier circuit for amplifying the antenna signal above background noise, comprising at least one microwave frequency amplifier having an input for receiving the microwave signal and an output for providing an amplified microwave output signal, and an automatic feedback means connected across the input and output of the amplifier to reverse bias the amplifier into an optimum operating range, said feedback means comprising a low frequency response transistor having an emitter, a collector and a base, the transistor emitter being connected to the amplifier output and the transistor collector being connected to the amplifier input, and power supply means for providing a bias voltage to the transistor base;
• and
• a separate down converter circuit connected to the output of the amplifier circuit, the down converter circuit comprising means for splitting the input signal into two parts 90 degrees out of phase with one another, tunable local oscillator means for providing an adjustable microwave frequency signal, means for splitting the adjustable microwave frequency into two parts 90 degrees out of phase with one another, means for combining each part of the input signal with a respective part of the adjusted microwave frequency signal, means for recombining each part of the mixed signal so as to reject image signals, and means for connecting the resultant signal to a receiver.