Back to results
US 6,191,648 B1Granted
Switched-capacitor cosine filter circuit
AssigneeNational Semiconductor Corporation
InventorLaurence Douglas Lewicki
Life of this patent
Estimating the term…
Abstract
A switched-capacitor cosine filter circuit includes a differential amplifier and a switched-capacitor circuit. A set of control signals cause the switched-capacitor circuit to selectively couple the inputs and output of the differential amplifier thereby producing a switched input signal for the differential amplifier. During alternating states of the control signals, the switched-capacitor cosine filter circuit samples the input signal as a noninverting and inverting integrator circuit.
Claims22
An apparatus including a switched-capacitor cosine filter circuit, comprising:
- inverse and noninverse signal input terminals for conveying inverse and noninverse phases of a differential input signal, respectively;
- a differential amplifier with first and second input terminals and at least one output terminal that in response to first and second input signals provide at least one output signal, respectively;
- a switched-capacitor feedback circuit, coupled between said at least one output terminal and at least one of said first and second input terminals, that in response to a plurality of control signals capacitively couples each one of said at least one output terminal individually to a respective one of said at least one of said first and second input terminals;
- and
- a switched-capacitor input circuit, coupled between said inverse and noninverse signal input terminals and said at least one of said first and second input terminals, that in response to a first portion of said plurality of control signals alternately capacitively couples said inverse and noninverse signal input terminals and said at least one of said first and second input terminals;
- wherein
- during a first state of said plurality of control signals, said switched-capacitor cosine filter circuit samples said inverse and noninverse differential input signal phases as a noninverting integrator circuit, and
- during a second state of said plurality of control signals, said switched-capacitor cosine filter circuit samples said inverse and noninverse differential input signal phases as an inverting integrator circuit.
5 more elements
An apparatus including a switch-capacitor cosine filter circuit, comprising:
- a switched-capacitor circuit that in response to a plurality of control signals receives and capacitively couples an input signal and an output signal to provide a switched input signal alternately corresponding to one of said capacitively coupled input and output signals;
- and
- a differential amplifier, coupled to said switched-capacitor circuit, that following reception of said switched input signal provides said output signal;
- wherein
- during a first state of said plurality of control signals, said switched-capacitor cosine filter circuit samples said input signal as a noninverting integrator circuit, and
- during a second state of said plurality of control signals, said switched-capacitor cosine filter circuit samples said input signal as an inverting integrator circuit.
3 more elements
A method which includes switching a plurality of capacitors to cosine filter a signal, comprising the steps of:
- conveying via inverse and noninverse signal input terminals a differential input signal with inverse and noninverse input signal phases, respectively;
- receiving first and second input signals with first and second input terminals, respectively;
- differentially amplifying said first and second input signals at said first and second input terminals and generating at least one output signal at at least one output terminal;
- receiving a plurality of control signals;
- capacitively coupling each one of said at least one output terminal individually to a respective one of said at least one of said first and second input terminals in response to said plurality of control signals;
- and
- alternately capacitively coupling said inverse and noninverse signal input terminals and said at least one of said first and second input terminals in response to a portion of said plurality of control signals;
- wherein
- during a first state of said plurality of control signals, said inverse and noninverse differential input signal phases are sampled as part of a noninverting signal integration, and
- during a second state of said plurality of control signals, said inverse and noninverse differential input signal phases are sampled as part of an inverting signal integration.
7 more elements
A method which includes switching a plurality of capacitors to cosine filter a signal, comprising the steps of:
- receiving an input signal;
- receiving a plurality of control signals;
- capacitively coupling said input signal and an output signal in response to said plurality of control signals and generating a switched input signal;
- and
- receiving said switched input signal and generating said output signal with a differential amplifier;
- wherein
- during a first state of said plurality of control signals, said input signal is sampled as part of a noninverting signal integration, and
- during a second state of said plurality of control signals, said input signal is sampled as part of an inverting signal integration.
5 more elements
Dependencies are inferred from the claim text.