Real-time error-suppression method and apparatus therefor
First Claim
1. A signal measurement method incorporating real-time. error suppression, said method comprising:
- establishing a frequency band, all frequencies of which are within ten percent of a center frequency thereof;
acquiring a first signal at a first frequency within said frequency band;
obtaining a second signal at a second frequency within said frequency band, said second frequency being offset from said first frequency;
combining said first and second signals to produce a third signal;
propagating said third signal over a signal path capable of inducing errors into said third signal to produce a fourth signal;
separating said fourth signal into a fifth signal and a sixth signal;
comparing said sixth signal against said second signal to determine a correction factor; and
applying said correction factor to said fifth signal to extract a replica of said first signal therefrom.
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Abstract
A thorough error suppression signal measurement system (20) having a transmitter (300) for propagating a transmission signal to a first probe 100, through a device under test (26), and into a second probe (200), and for propagating reference signals to the probes (100,200). The probes (100,200) extract normalization signals from the reference signals, exchange specific ones of the normalization signals, and combine the normalization signals with data signals derived from the transmission signal to form receiver signals. The probes (100,200) propagate the receiver signals to a receiver (400), where the signals are gain-ranged, digitized, normalized, and compensated for phase-noise.
55 Citations
46 Claims
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1. A signal measurement method incorporating real-time. error suppression, said method comprising:
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establishing a frequency band, all frequencies of which are within ten percent of a center frequency thereof;
acquiring a first signal at a first frequency within said frequency band;
obtaining a second signal at a second frequency within said frequency band, said second frequency being offset from said first frequency;
combining said first and second signals to produce a third signal;
propagating said third signal over a signal path capable of inducing errors into said third signal to produce a fourth signal;
separating said fourth signal into a fifth signal and a sixth signal;
comparing said sixth signal against said second signal to determine a correction factor; and
applying said correction factor to said fifth signal to extract a replica of said first signal therefrom. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
said method additionally comprises, prior to said separating activity, converting said analog fourth signal to a digital seventh signal; and
said separating, comparing, and applying activities are executed digitally within a digital processor in response to said digital seventh signal.
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5. A signal measurement method as claimed in claim 1 wherein said signal path is a first signal path and said correction factor is a first correction factor, said method additionally comprising:
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acquiring a seventh signal at a third frequency within said frequency band, said third frequency being offset from said first and second frequencies;
obtaining an eighth signal at a. fourth frequency within said frequency band, said fourth frequency being offset from said first, second, and third frequencies;
combining said seventh and eighth signals to produce a ninth signal;
propagating said ninth signal over a second signal path capable of inducing errors into said ninth signal to produce a tenth signal;
separating said tenth signal into an eleventh signal and a twelfth signal;
comparing said twelfth signal against said eighth signal to determine a second correction factor; and
applying said second correction factor to said eleventh signal to extract a replica of said seventh signal therefrom.
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6. A signal measurement method as claimed in claim 1 wherein:
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said method additionally comprises providing a seventh signal having a third frequency within said frequency band, said third frequency being offset from said first and second frequencies;
said acquiring activity comprises extracting an eighth signal at substantially said third frequency from said seventh signal;
said method additionally comprises providing a ninth signal having a fourth frequency, said fourth frequency being substantially a difference between said first and third frequencies; and
said acquiring activity additionally comprises mixing said eighth and ninth signals to produce said first signal.
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7. A signal measurement method as claimed in claim 1 wherein:
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said method additionally comprises providing a seventh signal at a third frequency within said frequency band, said third frequency being offset from said first and second frequencies;
said method additionally comprises providing an eighth signal at a fourth frequency within said frequency band, said fourth frequency being offset from said first, second, and third frequencies;
said method additionally comprises providing a ninth signal at a fifth frequency, said fifth frequency being offset from said first frequency substantially by said third frequency;
said method additionally comprises providing a tenth signal at a sixth frequency, said sixth frequency being offset from said second frequency substantially by said fourth frequency;
said acquiring activity comprises extracting an eleventh signal from said seventh signal, said eleventh signal being at substantially said third frequency;
said acquiring activity additionally comprises mixing said eleventh and ninth signals to produce said first signal;
said obtaining activity comprises extracting a twelfth signal from said eighth signal, said twelfth signal being at substantially said fourth frequency; and
said obtaining activity additionally comprises mixing said twelfth and tenth signals to produce said second signal.
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8. A signal measurement method as claimed in claim 7 wherein said fourth signal is an analog signal, said method additionally comprising:
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generating said ninth signal in a first local oscillator;
generating said tenth signal in a second local oscillator;
summing said ninth and tenth signals to produce a thirteenth signal, wherein said thirteenth signal is an analog signal;
converting, prior to said separating step, said analog fourth and thirteenth signals to a digital fourteenth signal and a digital fifteenth signal, respectively; and
submitting said fourteenth and fifteenth signals to a digital processor, wherein said fifteenth signal enables said separating activity to separate said fourteenth signal into said fifth and sixth signals.
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9. A signal measurement method as claimed in claim 1 wherein said signal path is a first signal path, said method additionally comprising:
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providing a seventh signal at a third frequency;
deriving said first signal from said seventh signal;
deriving said second signal from said seventh signal;
deriving an eighth signal from said seventh signal;
deriving a ninth signal from said seventh signal;
combining said eighth and ninth signals to produce a tenth signal;
propagating said tenth signal over a second signal path capable of inducing errors into said tenth signal to produce an eleventh signal;
normalizing said fourth and eleventh signals relative to each other to produce a twelfth signal and a thirteenth signal, respectively; and
compensating said twelfth and thirteenth signals for errors relative to said seventh signal.
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10. A signal measurement method claimed in claim 9 wherein said fourth and eleventh signals are analog signals, and wherein:
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said method additionally comprises, prior to said normalizing activity, converting said analog fourth and eleventh signals to a digital twelfth signal and a digital thirteenth signal, respectively; and
said normalizing and compensating activities are executed digitally within a digital processor in response to said digital twelfth and thirteenth signals.
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11. A signal measurement method as claimed in claim 1 additionally comprising:
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providing a seventh signal at a first amplitude;
injecting an eighth signal at a second amplitude into a first port of a device-under-test, said eighth signal being derived from said seventh signal;
extracting a ninth signal from a second port of said device-under-test, wherein said ninth signal is responsive to said eighth signal and a transfer function of said device-under-test;
deriving said first signal at a third amplitude from said eighth signal;
deriving a tenth signal at a fourth amplitude from said ninth signal; and
adjusting said third and fourth amplitudes to be within a predetermined amplitude ratio of each other.
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12. A signal measurement method as claimed in claim 11 additionally comprising adjusting said first amplitude so that said second amplitude is at a predetermined amplitude at said first port of said device-under-test.
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13. A signal measurement method as claimed in claim 1 additionally comprising:
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providing a seventh signal;
deriving said first signal from said seventh signal;
deriving an eighth signal from said seventh signal;
analyzing said eighth signal to determine the presence of phase noise within said seventh signal; and
compensating, when said analyzing activity determines said phase noise is present within said seventh signal, said phase noise within said third signal in response to said phase noise within said seventh signal.
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14. A signal measurement method as claimed in claim 1 additionally comprising:
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coupling a first probe to a first port of a device-under-test;
coupling a second probe to a second port of said device-under-test;
propagating a seventh signal from said first probe into said first port of said device-under-test;
propagating an eighth signal from said second port of said device-under-test into said second probe, said eighth signal being responsive to said seventh signal and a transfer function of said device-under-test;
deriving, within said first probe, said first signal from said seventh signal;
deriving, within said first probe, a ninth signal from said seventh signal;
deriving, within said second probe, a tenth signal from said eighth signal;
deriving, within said second probe, an eleventh signal from said eighth signal;
reciprocally propagating said ninth and eleventh signals from said first and second probes to said second and first probes, respectively, over a common signal path;
combining, within said first probe, said first and eleventh signals to produce said third signal;
combining, within said second probe, said tenth and ninth signals to produce a twelfth signal;
propagating said tenth signal over a second signal path capable of inducing errors into said tenth signal to produce an eleventh signal; and
normalizing said fourth and eleventh signals relative to each other to produce a twelfth signal and a thirteenth signal, respectively.
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15. A signal measurement method as claimed in claim 14 wherein:
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said method additionally comprises interposing a reciprocal amplification circuit into said common signal path between said first and second probes;
said reciprocally propagating activity comprises;
propagating said ninth signal from said first probe to a first i/o port of said reciprocal amplification circuit;
amplifying said ninth signal within said reciprocal amplification circuit to produce a fourteenth signal;
propagating said fourteenth signal from a second i/o port of said reciprocal amplification circuit to said second probe;
propagating said eleventh signal from said second probe to said second i/o port of said reciprocal amplification circuit;
amplifying said eleventh signal within said reciprocal amplification circuit to produce a fifteenth signal;
propagating said fifteenth signal from said first i/o port of said reciprocal amplification circuit to said first probe; and
said first-and-eleventh and tenth-and-ninth signal combining activities also combine said first and fifteenth signals and said tenth and fourteenth signals, respectively.
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16. A signal measurement method as claimed in claim 1 wherein said signal path is a first signal path, and wherein:
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said method additionally comprises providing a seventh signal at a third frequency and having a predetermined phase;
said method additionally comprises propagating said seventh signal over a second signal path, wherein said second signal path is a bidirectional signal path;
said method additionally comprises deriving an eighth signal from said seventh signal;
said first-and-second signal combining activity combines said first, second, and eighth signals to produce said third signal;
said method additionally comprises producing a ninth signal at a fourth frequency from said seventh signal;
said method additionally comprises propagating said ninth signal over said second signal path;
said method additionally comprises determining a phase of said ninth signal relative to said predetermined phase; and
said method additionally comprises analyzing said second-signal phase to establish a phase reference for said third signal.
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17. A signal measurement method as claimed in claim 1 wherein said signal path is a first signal path, said method additionally comprising:
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providing a seventh signal at a third frequency and having a predetermined phase;
propagating said seventh signal in a first direction over a second signal path, said second signal path being a bidirectional signal path;
producing an eighth signal at a fourth frequency from said seventh signal;
propagating said eighth signal in a second direction over said second signal path, said second direction being opposite said first direction;
determining a phase of said eighth signal relative to said predetermined phase; and
analyzing said eighth-signal phase to establish a phase of said first signal.
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18. A signal measurement system incorporating real-time error suppression, said system comprising:
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a signal source configured to generate a first signal at a first frequency, said first frequency being a frequency within a frequency band, all frequencies of which are within ten percent of a center frequency thereof;
a first mixer coupled to said signal source and configured to offset said first signal to produce a second signal at a second frequency within said frequency band;
a second mixer coupled to said signal source and configured to offset said first signal to produce a third signal at a third frequency within said frequency band;
a combiner coupled to said first and second mixers and configured to combine said second and third signals to produce a fourth signal;
a propagation medium coupled to said combiner and configured to propagate said fourth signal over a signal path to produce a fifth signal;
a processor coupled to said propagation medium and configured to extract a replica of said second signal from said fifth signal. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
said system additionally comprises an analog-to-digital converter coupled to said propagation medium and configured to convert said fifth signal into a sixth signal, said sixth signal being a digital signal; and
said processor is coupled to said analog-to-digital converter and configured to separate said sixth signal into a seventh signal and an eighth signal, compare said eighth signal against said third signal to determine a correction factor, and apply said correction factor to said seventh signal to extract said replica of said second signal therefrom.
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20. A signal measurement system as claimed in claim 18 wherein said combiner is a first combiner, said propagation medium is a first propagation medium, and said signal path is a first signal path, and wherein:
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said system additionally comprises a third mixer coupled to said signal source and configured to offset said first signal to produce a sixth signal at a fourth frequency within said frequency band;
said system additionally comprises a fourth mixer coupled to said signal source and configured to offset said first signal to produce a seventh signal at a fifth frequency within said frequency band;
said system additionally comprises a second combiner coupled to said third and fourth mixers and configured to combine said sixth and seventh signals to produce an eighth signal;
said system additionally comprises a second propagation medium coupled to said second combiner and configured to propagate said eighth signal over a second signal path to produce a ninth signal;
said processor is additionally configured to extract said sixth signal from said ninth signal.
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21. A signal measurement system as claimed in claim 18 wherein:
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said system additionally comprises a coupler coupled to said signal source, coupled to said first mixer, and configured to extract a sixth signal at substantially said first frequency from said first signal;
said system additionally comprises an oscillator coupled to said first mixer and configured to generate a seventh signal at a fourth frequency; and
said first mixer is configured to mix said sixth and seventh signals to produce said second signal, wherein said second frequency is one of a sum and a difference of said first frequency and said fourth frequency.
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22. A signal measurement system as claimed in claim 21 wherein said oscillator is a first oscillator, and wherein:
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said system additionally comprises a splitter coupled to said signal source, coupled to said second mixer, and configured to extract an eighth signal at substantially said first frequency from said first signal;
said system additionally comprises a second oscillator coupled to said second mixer and configured to generate a ninth signal at a fifth frequency; and
said second mixer is configured to mix said eighth and ninth signals to produce said third signal, wherein said third frequency is one of a sum and a difference of said first frequency and said fifth frequency.
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23. A signal measurement system as claimed in claim 22 additionally comprising:
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a summer coupled to said first and second oscillators and configured to sum said seventh and ninth signals to produce a tenth signal, said tenth signal being an analog signal;
an analog-to-digital converter coupled to said summer and configured to convert said tenth signal to an eleventh signal, said eleventh signal being a digital signal; and
said processor is additionally configured to utilize said eleventh signal to extract said replica of said second signal from said fifth signal.
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24. A signal measurement system as claimed in claim 18 wherein said combiner is a first combiner and said signal path is a first signal path, wherein:
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said system additionally comprises a third mixer coupled to said signal source and configured to offset said first signal to produce a sixth signal at a fourth frequency within said frequency band;
said system additionally comprises a fourth mixer coupled to said signal source and configured to offset said first signal to produce a seventh signal at a fifth frequency within said frequency band;
said system additionally comprises a second combiner coupled to said third and fourth mixers and configured to combine said sixth and seventh signals to produce an eighth signal;
said propagation medium is additionally configured to propagate said eighth signal over a second signal path to produce a ninth signal; and
said processor is additionally configured to normalize said fifth and ninth signals relative to each other, and to compensate said fifth and ninth signals for errors relative to said first signal.
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25. A signal measurement system as claimed in claim 24 wherein:
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said fifth and ninth signals are analog signals;
said system additionally comprises a first analog-to-digital converter coupled to said propagation medium and configured to convert said fifth signal into a tenth signal, said tenth signal being a digital signal;
said system additionally comprises a second analog-to-digital converter coupled to said propagation medium and configured to convert said ninth signal into an eleventh signal, said eleventh signal being a digital signal; and
said processor is configured to normalize said tenth and eleventh signals relative to each other, and to compensate said tenth and eleventh signals for errors relative to said first signal.
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26. A signal measurement system as claimed in claim 18 wherein:
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said signal source generates said first signal at a first amplitude;
said system additionally comprises a device-under-test having a first port and a second port;
said system additionally comprises an input circuit coupled to said signal source, coupled to said device-under-test, configured to derive a sixth signal from said first signal, and configured to inject said sixth signal at a second amplitude into said first port;
said system additionally comprises an output circuit coupled to said device-under-test and configured to extract a seventh signal from said second port, wherein said seventh signal is responsive to said sixth signal and a transfer function of said device-under test;
said first mixer is coupled to said input circuit and configured to offset said sixth signal to produce said second signal at a third amplitude;
said system additionally comprises a third mixer coupled to said output circuit and configured to offset said seventh signal to produce an eighth signal at a fourth amplitude;
said system additionally comprises a first amplifier coupled to said first mixer configured to amplify said second signal and having a first gain controlled by said processor;
said system additionally comprises a second amplifier coupled to said third mixer and configured to amplify said eighth signal and having a second gain controlled by said processor; and
said processor is additionally configured to control said first and second gains so that said third and fourth amplitudes are within a predetermined amplitude ratio of each other.
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27. A signal measurement system as claimed in claim 26 additionally comprising a source-control circuit coupled to said signal source and configured to establish said first amplitude for said first signal, wherein said second amplitude is a predetermined amplitude, and wherein said processor is additionally configured to adjust said first amplitude so that said ninth signal is at said predetermined amplitude at said first port of said device-under-test.
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28. A signal measurement system as claimed in claim 18 wherein:
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said system additionally comprises a third mixer coupled to said signal source and configured to offset said first signal to produce a sixth signal; and
said processor is additionally configured to analyze said sixth signal to detect the presence of phase noise within said first signal, and to compensate said fifth signal in response to said phase noise within said first signal.
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29. A signal measurement system as claimed in claim 18 wherein said propagation medium is a first propagation medium and said signal path is a first signal path, and wherein:
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said system additionally comprises a first probe for coupling to a first port of a device-under-test;
said system additionally comprises a second probe for coupling to a second port of said device-under-test;
said system additionally comprises a third mixer coupled to said signal source and configured to offset said first signal to produce a sixth signal;
said system additionally comprises a fourth mixer coupled to said signal source through said device-under-test and configured to offset said first signal to produce a seventh signal;
said system additionally comprises a fifth mixer coupled to said signal source through said device-under-test and configured to offset said first signal to produce an eighth signal; and
said system additionally comprises a second propagation medium coupled between said first and second probes and configured to propagate said sixth and eighth signals from said first and second probes to said second and first probes, respectively, over a second signal path.
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30. A signal measurement system as claimed in claim 29 wherein said combiner is a first combiner, and wherein:
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said first combiner is configured to combine said second, third, and sixth signals to produce said fourth signal; and
said system additionally comprises a second combiner coupled to said fourth mixer and configured to combine said seventh and eighth signals to produce a ninth signal.
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31. A signal measurement system as claimed in claim 29 additionally comprising a reciprocal amplification circuit interposed into said second signal path between said first and second probes.
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32. A signal measurement method incorporating real-time error suppression through signal normalization, said method comprising:
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a) providing a first signal at a first frequency;
b) deriving a second signal at a second frequency from said first signal;
c) deriving a third signal at a third frequency from said first signal;
d) combining said second and third signals to produce a fourth signal;
e) deriving a fifth signal at a fourth frequency from said first signal;
f) deriving a sixth signal at a fifth frequency from said first signal;
g) combining said fifth and sixth signals to produce a seventh signal;
h) propagating said fourth and seventh signals through a first signal path and a second signal path, respectively, in a propagation medium;
i) normalizing said fourth and seventh signals relative to each other to produce an eighth signal and a ninth signal, respectively; and
j) compensating said eighth and ninth signals for errors relative to said first signal. - View Dependent Claims (33, 34, 35)
providing an analysis unit;
coupling a probe to said analysis unit;
deriving, within said analysis unit, a tenth signal from said first signal;
propagating said tenth signal from said analysis unit to said probe via a third signal path, wherein said third signal path is a bidirectional signal path;
deriving, within said probe, an eleventh signal from said tenth signal;
propagating said eleventh signal from said probe to said analysis unit via said third signal path; and
determining, within said analysis unit, a phase of said eleventh signal relative to said predetermined phase.
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34. A method as claimed in claim 32 additionally comprising:
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deriving a tenth signal from said first signal;
analyzing said tenth signal to determine the presence of phase noise within said first signal; and
canceling, when said analyzing activity determines said phase noise is present within said first signal, said phase noise within one of said fourth and seventh signals in response to said phase noise within said first signal.
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35. A method as claimed in claim 32 additionally comprising:
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coupling a device-under-test between a first probe and a second probe;
propagating said first signal from said first probe to said second probe through said device-under-test;
deriving, within said first probe, a tenth signal from said first signal;
deriving, within said second probe, an eleventh signal from said first signal;
deriving, within said second probe, a twelfth signal from said first signal;
reciprocally propagating said tenth and twelfth signals from said first and second probes to said second and first probes, respectively, over a common signal path;
combining, within said first probe, said second and twelfth signals; and
combining, within said second probe, said eleventh and tenth signals.
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36. A method for signal measurement through a device-under-test, said method comprising:
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a) providing a first signal at a first amplitude;
b) injecting a second signal at a second amplitude into a first port of said device-under-test, said second signal being derived from said first signal;
c) extracting a third signal from a second port of said device-under-test, wherein said third signal is responsive to said second signal and a transfer function of said device-under-test;
d) deriving a fourth signal at a third amplitude from said second signal;
e) deriving a fifth signal at a fourth amplitude from said second signal;
f) deriving a sixth signal at a fifth amplitude from said third signal;
g) deriving a seventh signal at a sixth amplitude from said third signal; and
h) adjusting each of said third, fourth, fifth, and sixth amplitudes to be within a predetermined amplitude ratio of each other. - View Dependent Claims (37, 38, 39)
providing an analysis unit;
coupling a probe to said analysis unit;
providing, within said analysis unit, an eighth signal having a predetermined phase;
propagating said eighth signal from said analysis unit to said probe via a bidirectional signal path;
producing, within said probe, a ninth signal from said eighth signal;
propagating said ninth signal from said probe to said analysis unit via said bidirectional signal path;
determining a phase of said ninth signal relative to said predetermined phase; and
analyzing said ninth-signal phase to establish a phase reference for said fourth signal.
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38. A method as claimed in claim 36 additionally comprising adjusting said first amplitude so that said second amplitude is a predetermined amplitude at said first port of said device-under-test.
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39. A method as claimed in claim 36 additionally comprising:
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coupling a first probe to said first port of a device-under-test;
coupling a second probe to said second port of said device-under-test;
deriving an eighth signal from said third signal in said second probe;
deriving a ninth signal from said first signal in said first probe;
deriving a tenth signal from said first signal in said second probe;
reciprocally propagating said ninth and tenth signals from said first and second probes to said second and first probes, respectively, over a common signal path;
incorporating said tenth signal into said fourth signal; and
incorporating said ninth signal into said eighth signal.
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40. An apparatus incorporating real-time error suppression with improved accuracy in the measurement of a test signal through a device-under-test, said apparatus comprising:
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an analysis unit;
a first probe coupled to said analysis unit and to a first port of said device-under-test;
a second probe coupled to said analysis unit and to a second port of said device-under-test; and
a trans-probe channel coupled between said first and second probes, wherein said trans-probe channel is configured to propagate a first link signal from said first probe to said second probe and propagate a second link signal from said second probe to said first probe. - View Dependent Claims (41, 42, 43, 44, 45, 46)
said analysis unit comprises a signal source coupled to said first and second probes and configured to generate a first signal;
said first probe comprises;
an input circuit coupled to said signal source, and configured to extract a second signal from said first signal and to propagate said second signal from said first probe into said first port;
a first mixer coupled to said input circuit and configured to produce a fourth signal from said second signal;
a second mixer coupled to said signal source and configured to produce said fifth signal from said first signal; and
a first combiner coupled to said first mixer and configured to combine said fourth signal and said seventh signal to produce an eighth signal;
said second probe comprises;
an output circuit configured to obtain a third signal from said second port, said third signal being responsive to said second signal and a transfer function of said device-under-test;
a third mixer coupled to said output circuit and configured to produce a sixth signal from said third signal;
a fourth mixer coupled to said signal source and configured to produce said seventh signal from said first signal; and
a second combiner coupled to said third mixer and configured to combine said sixth signal and said fifth signal to produce a ninth signal; and
said trans-probe channel is configured to reciprocally propagate said fifth and seventh signals from said first and second probes to said second and first probes, respectively, over a common signal path.
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42. An apparatus as claimed in claim 41 wherein:
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said first signal is at a first frequency;
said second signal is at substantially said first frequency;
said third signal is at substantially said first frequency;
said fourth signal is at a second frequency;
said fifth signal is at a third frequency;
said sixth signal is at a fourth frequency;
said seventh signal is at a fifth frequency; and
said first, second, third, fourth, and fifth frequencies are different frequencies within a frequency band, each frequency of which is within ten percent of a center frequency thereof.
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43. An apparatus as claimed in claim 41 wherein:
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said first probe additionally comprises;
a coupler coupled to said input circuit and configured to extract a tenth signal from said second signal;
an oscillator configured to provide an eleventh signal; and
a fifth mixer coupled to said coupler and said oscillator and configured to mix said tenth and eleventh signals to generate said fourth signal; and
said second probe additionally comprises;
a coupler coupled to said output circuit and configured to extract a twelfth signal from said third signal;
an oscillator configured to provide a thirteenth signal; and
said third mixer couples to said coupler and said oscillator and is configured to mix said twelfth and thirteenth signals to generate said sixth signal.
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44. An apparatus as claimed in claim 41 wherein said trans-probe channel is a first channel and said common signal path is a first signal path, wherein:
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a second channel is coupled between said analysis unit and said first probe and configured to propagate said first signal from said analysis unit to said first probe. over a second signal path within said second channel; and
a third channel is coupled between said analysis unit and said second probe and configured to propagate said first signal from said analysis unit to said second probe over a third signal path within said third channel.
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45. An apparatus as claimed in claim 40 wherein said trans-probe channel comprises:
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a common signal path between said first probe and said second probe; and
a reciprocal amplification circuit interposed within said common signal path, configured to amplify said first link signal as said first link signal is propagated from said first probe to said second probe over said common signal path, and configured to amplify said second link signal as said second link signal is propagated from said second probe to said first probe over said common signal path.
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46. An apparatus as claimed in claim 45 wherein said reciprocal amplification circuit comprises:
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a first signal-routing device coupled between said first and second probes and interposed within said common signal path so as to divide said common signal path into a first portion and a second portion thereof;
a second signal-routing device coupled to said first signal-routing device; and
an amplifier coupled to said second signal routing device.
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Specification