Method and apparatus for sampling in-phase and quadrature components
AssigneeMassachusetts Institute of Technology
InventorCharles M. Rader
Life of this patent
Estimating the term…
Abstract
In-phase and quadrature components of a waveform are generated by sampling the waveform at a rate of four times the center frequency of the frequency band for which components are generated. The samples are digitized and applied to a digital 90.degree. all-pass phase-splitting network. Each pair of output samples is generated as a function of input samples delayed by an even number of time instants through a first all-pass branch and delayed by an odd number of time instants through a second all-pass branch. A common network may form both branches by switching coefficients of a multiplier and alternating the output between in-phase and quadrature samples. The waveform may be shifted from a higher freqeuncy by a mixer and may be filtered prior to sampling.
Claims26
Electronic apparatus for providing, as pairs of output samples, samples of in-phase and quadrature components of a waveform comprising:
- sampling means for generating samples by sampling the waveform at equally spaced time instants;
- digitizing means for digitizing each of the samples;
- and
- a digital phase-splitting network having the digitized samples as an input, each pair of output samples being generated such that one component of the pair is a function of only input samples delayed by an even number of time instants and the other component is a function of only input samples delayed by an odd number of time instants.
Electronic apparatus for providing pairs of samples of in-phase and quadrature components of a waveform comprising:
- sampling means for generating samples by sampling the waveform at equally spaced time instants;
- digitizing means for digitizing each of the samples;
- and
- a digital all pass filter having the digitized samples as an input, the two component samples of each pair of in-phase and quadrature component samples being alternately generated from alternate input samples.
Electronic apparatus for providing samples of in-phase and quadrature components of a waveform having a band of frequency components confined substantially to a frequency range of f.sub.min to f.sub.max having a center frequency f.sub.o comprising:
- sampling means for generating samples by sampling the waveform at equally spaced time instants spaced by times 1/(4f.sub.o);
- digitizing means for digitizing each of the samples;
- and
- a digital 90.degree. phase-splitting network having the digitized samples as an input and comprising first and second digital all-pass filter branches having respective outputs, the phase difference of which approximates 90.degree. for the band of frequencies f.sub.min to f.sub.max, the z-transform poles of each all-pass filter branch being symmetric about the imaginary axis of the z-plane and one all-pass filter branch having a pole at zero.
Electronic apparatus for providing samples of in-phase and quadrature components of a waveform comprising:
- sampling means for generating samples by sampling the waveform at equally spaced time instants;
- digitizing means for digitizing each of the samples;
- and
- a digital phase-splitting network having the digitized samples as an input and comprising first and second digital all-pass filter branches having respective outputs, the z-transform transfer functions of the all-pass filter branches being in the forms ##EQU13##
Electronic apparatus for providing samples of in-phase and quadrature components of a waveform comprising:
- sampling means for generating samples by sampling the waveforms at equally spaced time instants;
- digitizing means for digitizing each of the samples;
- and
- a digital all-pass network having the digitized samples as an input and comprising a first delay for delaying each input sample two time instants, a first summer having the output of the first delay as one input for alternately generating in-phase and quadrature components of sample pairs, a second delay for delaying each output of the first summer two time instants, a second summer for summing each input sample with the output of the second delay, a multiplier for generating the product of the output of the second summer and a multiplying coefficient, the product providing a second input to the first summer, and means for alternating the multiplying coefficient of the multiplier with generation of in-phase and quadrature components.
A method of providing, as pairs of output samples, in-phase and quadrature components of a waveform, the method comprising:
- sampling the waveform at equally spaced time instants to generate a set of even samples spaced from an initial time by an even number of time instants and a set of odd samples spaced from said initial time by an odd number of time instants;
- digitizing each of the samples;
- and
- generating said pairs of output samples in a digital phase-splitting network such that one component of each pair is generated from only even samples and the other component is generated from only odd samples.
A method of providing pairs of samples of in-phase and quadrature components of a waveform comprising:
- sampling the waveform;
- digitizing each of the samples;
- and
- alternately generating the two component samples of each pair of in-phase and quadrature component samples from alternate input samples in a digital all-pass filter.
A method of providing samples of in-phase and quadrature components of a waveform having a band of frequency components confined substantially to a frequency range of f.sub.min to f.sub.max having a center frequency f.sub.o comprising:
- sampling the waveform at equally spaced time instants spaced by times 1/(4f.sub.o);
- digitizing each of the samples;
- and
- generating in-phase and quadrature components in a digital 90.degree. phase-splitting network having the digitized samples as an input and comprising first and second digital all-pass filter branches having respective outputs, the phase difference of which approximates 90.degree. for the band of frequencies f.sub.min to f.sub.max' the z-transform poles of each all-pass filter branch being symmetric about the imaginary axis of the z-plane and one all-pass filter branch having a pole at zero.
A method of providing samples of in-phase and quadrature components of a waveform comprising:
- sampling the waveform at equally spaced time instants;
- digitizing each of the samples;
- and
- generating in-phase and quadrature components in a digital phase-splitting network having the digitized samples as an input and comprising first and second digital all-pass filter branches having respective outputs, the z-transform transfer functions of the all-pass filter branches being in the forms ##EQU14##
A method of providing samples of in-phase and quadrature components of a waveform comprising:
- sampling the waveform at equally spaced time instants;
- digitizing each of the samples;
- and
- delaying each input sample two time instants, summing the delayed input sample with a product for alternately generating in-phase and quadrature components of sample pairs, delaying each in-phase and quadrature component two time instants, summing each input sample with the delayed in-phase and quadrature components to generate a second summed output, and multiplying the second summed output with a multiplying coefficient to generate the aforementioned product, the multiplying coefficient being alternated with generation of in-phase and quadrature components.
Dependencies are inferred from the claim text.