Same Frequency Repeater Amplification

Abstract

The gain of a same-frequency amplifier, used in microwave relay links and in transponders and repeaters, becomes limited because of the inherent coupling of the amplifier output into its input, which leads to a self- oscillation when the gain exceeds the output-input isolation factor. If this oscillation-causing coupled singal is cancelled by a counter signal at the amplifier input, the amplifier gain can be arbitrarily increased without risking an oscillation. In this paper a method is described for adaptively synthesizing the exact counter signal needed to cancel the coupled signal, even when no a priori knowledge on the characteristics of the amplifier isolation or of the signal to be amplified, are available. The concept of adaptive control needed for this purpose, along with the principal components required for the control and test results, illustrating the effectiveness of the approach, are described herein.

Indexing terms:

• Microwave amplification
• Adaptive decoupling