Networks

As described in the first article of this issue, all selectivity required by the microwave transmitter and microwave receiver of the T D - 3 radio system is provided by passive networks. 1 The general plan followed in the design and development of these networks was to: (i) Determine, from the system requirements, the preliminary in band and out of band loss requirements for the microwave networks. (ii) Design microwave networks meeting the loss requirements with a minimum of amplitude distortion and with only broad-shape types of amplitude variation over the passband. The return loss requirement of the networks was generally specified as 30 dB minimum. (in) Calculate and measure the in-band loss distortions of the microwave networks to set preliminary requirements for the IF equalization networks. (iv) Develop a preliminary design of IF equalizer meeting these preliminary requirements in order to perform system tests to establish that the network characteristics were satisfactory. (v) Construct and measure characteristics of a substantial number of models of the microwave networks which introduce distortions. These results were used to specify the actual requirements of the IF equalizing networks. (vi) Redesign the IF equalizing networks to compensate for the nominal distortions introduced by the microwave networks. 1397