CORRELATION TYPE PHASE DETECTOR
First Claim
1. Apparatus for determining the phase angles of each of a plurality of signals relative to predetermined phase angles of reference waves having the same frequencies as the signals, said plural signals being frequency multiplexed on a common line and each having a different frequency, said frequencies all being an integral multiple of a further frequency, comprising means responsive to the frequency multiplexed signals on the common line and the reference waves for deriving product signals indicative of sin ( omega it + phi 1) sin omega it and sin ( omega it + phi i) cos omega it for each of the frequencies, where:
- omega i 2 pi fi, fi is selectively each of the frequencies, t time, and phi i phase angle between the reference wave and the signal for each of the frequencies fi, integration means responsive to each of the product signals, means for activating the integration means for the same time period for each product signal, said period being an integral multiple of the period of the further frequency, whereby the integration means derives, at the end of each activation period, first and second signals respectively indicative of sin phi and cos phi for each of the frequencies, and computer means responsive to the first and second signals for each of the frequencies for deriving an indication of phi for each of the frequencies.
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Abstract
The phase angles of each of a plurality of frequency multiplexed signals derived on a common lead and having predetermined frequencies are determined relative to predetermined phase angles of reference waves having the same frequencies as the signals. Correlator means responds to the plural signals and reference waves to derive signals indicative of the orthogonal cross correlations of one reference wave with the signal for each frequency. The correlator means includes integration means that is activated for the same time period for each cross correlation of each frequency. The activating period is an integral multiple of the reciprocal of a frequency that is a common factor of the predetermined frequencies. The integration means thereby derives, at the end of each activation period, first and second signals respectively indicative of sin phi and cos phi for each of the frequencies. A computer means responds to the first and second signals for each of the frequencies to derive an indication of phi for each of the frequencies.
22 Citations
10 Claims
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1. Apparatus for determining the phase angles of each of a plurality of signals relative to predetermined phase angles of reference waves having the same frequencies as the signals, said plural signals being frequency multiplexed on a common line and each having a different frequency, said frequencies all being an integral multiple of a further frequency, comprising means responsive to the frequency multiplexed signals on the common line and the reference waves for deriving product signals indicative of sin ( omega it + phi 1) sin omega it and sin ( omega it + phi i) cos omega it for each of the frequencies, where:
- omega i 2 pi fi, fi is selectively each of the frequencies, t time, and phi i phase angle between the reference wave and the signal for each of the frequencies fi, integration means responsive to each of the product signals, means for activating the integration means for the same time period for each product signal, said period being an integral multiple of the period of the further frequency, whereby the integration means derives, at the end of each activation period, first and second signals respectively indicative of sin phi and cos phi for each of the frequencies, and computer means responsive to the first and second signals for each of the frequencies for deriving an indication of phi for each of the frequencies.
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2. Apparatus for determining the phase angles of each of a plurality of signals relative to predetermined phase angles of reference waves having the same frequencies as the signals, said plural signals being frequency multiplexed on a common line and each having a different frequency, said frequencies all being an integral multiple of a further frequency, comprising meas responsive to the frequency multiplexed signals on the common line and the reference waves for deriving signals indicative of orthogonal cross correlations of the reference wave with the signal for each of said frequencies, said means including integration means for both of said cross correlations, means for activating the integration means for the same time period for each cross correlation of each frequency, said period being an integral multiple of the period of the further frequency, whereby the integration means derives, at the end of each activation period, first and second signals respectively indicative of sin phi and cos phi for each of the frequencies, and computer means responsive to the first and second signals for each of the frequencies for deriving an indication of phi for each of the frequencies.
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3. The apparatus of claim 2 wherein the means for deriving the cross correlations for each frequency includes:
- means for sampling the multiplexed signal four equispaced times during each cycle of the reference wave for the frequency, a pair of integration means, switch means for coupling two different alternate samples of the signal to each of the integration means during each of said cycles, one of said samples being coupled to the integration means with reversed phase relative to the signal and the other sample having the same phase as the signal.
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4. The apparatus of claim 2 wherein the means for deriving the cross correlations for each frequency includes:
- first and second mixer means respectively responsive to the reference wave at phases 0* and 90* and the multiplexed signal for deriving a pair of output signals, said integration means including first and second integratoRs respectively responsive to the output signals derived by the first and second mixers.
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5. Apparatus for determining the phase angle of a frequency multiplexed input signal relative to the phase angle of a frequency multiplexed reference wave having the same frequency as the input signal comprising means responsive to the frequency multiplexed input signal and reference wave for deriving orthogonal cross correlations of the reference wave and the input signal, said means including integration means for each of the cross correlations, a source of timing signals having constant frequency and phase for activating the integration means for a period that is an integral multiple of one cycle of the reference wave frequency, whereby the integration means derives at the end of each activation period first and second signals respectively indicative of sin phi and cos phi , and computer means responsive to the first and second signals for deriving an indication of phi .
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6. The apparatus of claim 5 wherein the means for deriving cross correlation signals includes:
- means for sampling the input signal four equispaced times during each cycle thereof, switch means for coupling two different alternate samples of teh signal to each of the integration means during each of said cycles, one of said samples being coupled to the integration means with reversed phase relative to the signal and the other sample having the same phase as the signal.
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7. The apparatus of claim 5 wherein the means for deriving the cross correlations includes:
- first and second mixer means respectively responsive to the reference wave at phases 0* and 90* and the multiplexed signal for deriving a pair of output signals, said integration means including first and second integrators respectively responsive to the output signals derived by the first and second mixers.
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8. In an apparatus for measuring the phase angle of an input signal relative to the phase angle of a reference wave having the same frequency as the input signal, means for sampling the input signal four equispaced times during each cycle thereof, first and second integration means, switch means for coupling two different alternate samples of the signal to each of the integration means during each of said cycles, one of said samples being coupled to the integration means with reversed phase relative to the signal and the other sample having the same phase as the signal, and means for activating the integration means for a period that is an integral multiple of the period of one cycle of the reference wave.
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9. The apparatus of claim 8 wherein the means for sampling comprises an analog to digital converter, and each of the integration means includes an accumulator register.
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10. The apparatus of claim 8 wherein the switch means comprises a pair of cascaded double pole single throw switches.
Specification