Considerations in the Design of a Radar Intermediate-Frequency Amplifier

The intermediate-frequency amplifier of a microwave radar receiver is commonly required to provide approximately 100 decibels amplification in a bandwidth of 1 to 10 megacycles, centered at frequencies in the 30- and 60-megacycle regions. Meeting such requirements involves the use of five to ten amplifier stages of the highest efficiency that can be suited to production methods. In addition, the noise figure of the radar intermediate-frequency amplifier is a significant contributor to the over-all radar receiver noise figure, and must therefore be maintained at an absolute minimum. By examining a particular intermediate-frequency-amplifier design (one providing an over-all bandwidth of 10 megacycles centered at 60 or 100 megacycles), this paper discusses qualitatively the theoretical problems involved in such a design and gives data of practical importance to the engineer attempting to build a similar amplifier. Measured characteristics of approximately fifty amplifiers are summarized to illustrate the end results achieved.