Digital adaptive transversal filter for spread spectrum receivers
First Claim
1. A digital adaptive transversal filter for processing a composite analog input signal comprising multiple direct-sequence spread-spectrum signals, additive thermal noise, and additive multiple narrowband interferers, and for providing a digital output signal to carrier/code removal means, said adaptive transversal filter comprisingautomatic gain control means for compensating for power excursions in said analog input signal, and for generating a power-regulated analog signal which is linearly related to the received signal,analog-to-digital converter means for converting said power-regulated analog signal to a multi-bit digital input signal,digital finite impulse response filter means, being responsive to said digital input signal and using a set of variable digital weight coefficients for generating a digital output signal containing said multiple spread-spectrum signals, additive noise, and a reduced amount of narrowband interference,digital weight generator means responsive to the digital input and digital output signals for updating said digital weight coefficients, andreset generator means for periodically resetting said digital weight coefficients to zero initial values.
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Abstract
A digital adaptive transversal filter includes an interface circuit for regulating and digitizing analog input signals, which comprise of multiple spread-spectrum signals, additive thermal noise and additive multiple narrowband interferers, to provide multi-bit digital input signals. A digital finite impulse response filter having a set of variable digital weight coefficients responds to the multi-bit digital input signals to generate digital output signals which contain a reduced amount of narrowband interference. A digital weight generator responds to the digital input and digital output signals for updating the digital weight coefficients, and a reset generator periodically resets the digital weight coefficients to zero initial values.
In a preferred embodiment an 8-tap, 8-bit digital adaptive transversal filter operating at 22 MHz was implemented with discrete components and a processing gain of 30 dB was demonstrated.
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Citations
6 Claims
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1. A digital adaptive transversal filter for processing a composite analog input signal comprising multiple direct-sequence spread-spectrum signals, additive thermal noise, and additive multiple narrowband interferers, and for providing a digital output signal to carrier/code removal means, said adaptive transversal filter comprising
automatic gain control means for compensating for power excursions in said analog input signal, and for generating a power-regulated analog signal which is linearly related to the received signal, analog-to-digital converter means for converting said power-regulated analog signal to a multi-bit digital input signal, digital finite impulse response filter means, being responsive to said digital input signal and using a set of variable digital weight coefficients for generating a digital output signal containing said multiple spread-spectrum signals, additive noise, and a reduced amount of narrowband interference, digital weight generator means responsive to the digital input and digital output signals for updating said digital weight coefficients, and reset generator means for periodically resetting said digital weight coefficients to zero initial values.
Specification