Patent ID: 6636128
Filing Date: 2003-10-21
Classification: H03H

Abstract:
A notch filter comprising:a reciprocal passive phase-shift network having a first port and a second port, a frequency-selective directional coupling network having a third port, a fourth port, a fifth port, and a sixth port, the third port of the frequency-selective coupling network being receptive to an input signal, the fourth port of the frequency-selective coupling network being capable of producing an output signal, the fifth port of the frequency-selective coupling network being connected to the first port of the reciprocal passive phase-shift network, the sixth port of the frequency-selective coupling network being connected to the second port of the reciprocal passive phase-shift network, the frequency-selective directional coupling network allowing essentially no signal to flow from the third port of the frequency-selective directional coupling network to the sixth port of the frequency-selective directional coupling network through the frequency-selective directional coupling network, wherein upon receiving a first input signal having a frequency within a predetermined frequency band, a first portion of the first input signal passes from the third port of the frequency-selective directional coupling network to the fifth port of the frequency-selective directional coupling network, from the fifth port of the frequency-selective directional coupling network to the sixth port of the frequency-selective directional coupling network through the reciprocal passive phase-shift network, and from the sixth port of the frequency-selective directional coupling network to the fourth port of the frequency-selective directional coupling network; and a second portion of the first input signal passes from the third port of the frequency-selective directional coupling network to the fourth port of the frequency-selective directional coupling network through the frequency-selective directional coupling network, resulting in cancellation of the first portion of the first input signal with the second portion of the first input signal at the fourth port of the frequency-selective directional coupling network, and wherein upon receiving a second input signal having a frequency outside the predetermined frequency band, essentially all of the second input signal passes from the third port to the fifth port, from the fifth port to the sixth port through the reciprocal passive phase-shift network, and from the sixth port to the fourth port.