Circuit technique in frequency-modulated microwave links

The paper describes the circuit problems in wide-band microwave communication links and is illustrated by reference to the development of links operating at frequencies around 4 000 Mc/s for 180-channel telephony and for television. Modulating and demodulating circuits with very linear characteristics, and i.f. amplifiers with uniform time-delay are described, together with the necessary techniques required to assess their performances. The optimum design for a broad-band low-noise i.f. amplifier is shown to consist of cascaded earthed-grid triodes. Automatic-frequency-control systems, the special video problems of television, and high-level intermediate-frequency/microwave mixers are described.