Frequency response of a microwave notch filter in presence of two interfering tones

Abstract

The frequency response of a microwave notch filter using a pair of magic tees has been studied theoretically as well as experimentally in this paper. This notch filter designed at 10.5 GHz eliminates the first interfering tone. When the second interference appears at the input of this notch filter the response is modified and its fails to remove the first interference because the null point of the response gets shifted upwards under the action of the second interference. The dc shift of the minimum of the response has been calculated and measured when the second interference is 520 MHz below the first interference. The theory and experiment gives a reasonable fit.