Notch filter
First Claim
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1. An improved notch filter for rejecting a predetermined band of signal frequencies from an input signal comprising:
- a. a quadrature coupler having first, second, third, and fourth terminals, said first terminal being a signal input terminal and said fourth terminal being an output terminal,b. a first tuned surface acoustic wave device coupled to said second one of said terminals for receiving said input signal with 0°
phase shift, said first tuned device having primarily reactive characteristics at signal frequencies higher or lower than the notch region and primarily resistive characteristics across said notch region, andc. a second tuned surface acoustic wave device coupled to a third one of said terminals for receiving said input signal with a 90°
phase shift, said second tuned device having primarily reactive characteristics at signal frequencies higher or lower than the notch region and primarily resistive characteristics across said notch region, such that no output signal is present on said fourth terminal across said notch region but is present in the band pass region.
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Abstract
A notch filter which utilizes a quadrature coupler with the input signal on one of its four terminals, a first tuned surface acoustic wave device coupled to a second on of the terminals for receiving the input signal at 0° phase shift, a second tuned surface acoustic wave device coupled to a third one of the terminals for receiving the input signal with a 90° phase shift and the fourth terminal being utilized as the output signal terminal.
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Citations
12 Claims
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1. An improved notch filter for rejecting a predetermined band of signal frequencies from an input signal comprising:
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a. a quadrature coupler having first, second, third, and fourth terminals, said first terminal being a signal input terminal and said fourth terminal being an output terminal, b. a first tuned surface acoustic wave device coupled to said second one of said terminals for receiving said input signal with 0°
phase shift, said first tuned device having primarily reactive characteristics at signal frequencies higher or lower than the notch region and primarily resistive characteristics across said notch region, andc. a second tuned surface acoustic wave device coupled to a third one of said terminals for receiving said input signal with a 90°
phase shift, said second tuned device having primarily reactive characteristics at signal frequencies higher or lower than the notch region and primarily resistive characteristics across said notch region, such that no output signal is present on said fourth terminal across said notch region but is present in the band pass region. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of forming an improved notch filter for rejecting a predetermined band of signal frequencies from an input signal comprising the steps of:
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a. forming a quadrature coupler having first, second, third and fourth terminals, said first terminal being a signal input terminal and said fourth terminal being an output terminal, b. coupling a first tuned surface acoustic wave device to said second one of said terminals for receiving said input signal with a 0°
degree phase shift, said first tuned device having primarily reactive characteristics at said signal frequencies higher or lower than the notch region and primarily resistive characteristics across said notch region, andc. coupling a second tuned surface acoustic wave device to a third one of said terminals for receiving said input signal with a 90°
phase shift, said second tuned device having primarily reactive characteristics at signal frequencies higher or lower than the notch region and primarily resistive characteristics across said notch region such that no output signal is present on said fourth terminal across said notch region but is present in the band pass region. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification