Design Considerations for a Low-Noise Wideband IF Pre-amplifier for Radar Receivers

Abstract

This paper describes a transistorized IF pre-amplifier which was primarily designed to be used in conjunction with a radar receiver. The pre-amplifier has an excellent low-noise performance over the range from 20 MHz to 130 MHz. The advantage of this amplifier is its low noise figure and wide bandwidth. This amplifier consists of a common emitter followed by a common base transistor amplifier. The combination is entirely non-critical and provides low noise figure and high gain with good stability. Noise figures averaging 2 dB in the frequency band 20 MHz to 130 MHz have been achieved. The amplifier has an overall dynamic range of about 80 dB before the distortion becomes significant. The maximum input signal voltage at this distortion is—7 dBm. The amplifier provides a minimum gain of 22 dB with 50-ohm source and load impedances.

Design considerations for the input stage and conditions necessary to minimize noise figure are discussed. A method for calculating noise figure of the amplifier is also given.

Indexing Terms:

• Low-Noise Amplifiers
• If Pre-amplifiers