Tests for non-linear distortion using digital signal processing
First Claim
1. A test system for measuring a non-linear distortion created by a reference test signal transported on a signal path comprising:
- a transmitter for transmitting the reference test signal;
a receiver, for receiving an impaired reference test signal, wherein the impaired reference test signal comprises the reference test signal as impaired while passing between the transmitter and receiver through the signal path;
a digital signal processor connected to an output of the receiver to receive the impaired reference test signal from the receiver, the digital signal processor;
storing a copy of the reference test signal;
computing an impulse response of the signal path using the copy of the reference test signal and the impaired reference test signal;
calculating the energy in the impulse response during time periods of the impulse response that contain primarily non-linear distortion energy.
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Accused Products
Abstract
A system for determining a composite signal level at which a signal path begins to generate non-linear distortion. A uses a reference test signal, which is preferably a short-duration burst of repeatable broadband energy, that is passed through the signal path and received on a digital signal acquisition unit. An impaired received reference test signal is comprised of is formed from the transmitted reference test signal, linear distortion components, and non-linear distortion components. The impaired received reference test signal is digitally processed to reveal the non-linear distortion components. The impaired received reference test signal may be processed with a stored reference test signal to find a time-domain impulse response from which the uncorrelated distortion energy can be measured. Alternately, a reference test signal, such as an orthogonal frequency division multiplex (OFDM) reference signal with spectral holes, can be processed in the frequency domain to find the non-linear distortion energy that enters the spectral holes. Alternately, a transfer function of a signal path, showing an output voltage as a function of an input voltage, can be generated from a two-burst waveform comprised of a clipping high-level sinewave and non-clipping low-level sinewave. As the reference test signals are elevated in level, the magnitude of the non-linear distortion products can typically be observed to increase.
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Citations
78 Claims
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1. A test system for measuring a non-linear distortion created by a reference test signal transported on a signal path comprising:
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a transmitter for transmitting the reference test signal;
a receiver, for receiving an impaired reference test signal, wherein the impaired reference test signal comprises the reference test signal as impaired while passing between the transmitter and receiver through the signal path;
a digital signal processor connected to an output of the receiver to receive the impaired reference test signal from the receiver, the digital signal processor;
storing a copy of the reference test signal;
computing an impulse response of the signal path using the copy of the reference test signal and the impaired reference test signal;
calculating the energy in the impulse response during time periods of the impulse response that contain primarily non-linear distortion energy. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A test system for measuring a non-linear distortion created by a signal path comprising:
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a transmitter for transmitting a reference test signal wherein the reference test signal comprises an OFDM reference test signal having at least one spectral hole;
a signal path;
a receiver for receiving an impaired reference test signal comprising the reference test signal as impaired while passing between the transmitter and receiver through the signal path;
a digital signal processor connected to an output of the receiver for measuring a total amount of energy within the impaired reference test signal and for measuring an amount of energy within the at least one spectral hole;
wherein the non-linear distortion energy is determined from the energy contained within the at least one spectral hole. - View Dependent Claims (13)
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14. A test system for determining a transfer function of a signal path comprising:
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a transmitter for transmitting a two-burst waveform comprised of a low-level sinewave part and a high-level sinewave part;
a signal path;
a receiver for receiving the two-burst waveform as impaired while passing between the transmitter and receiver through the signal path; and
a digital signal processor connected to an output of the receiver for determining a non-linear transfer function of the signal path by plotting the time samples of the low-level sinewave on a first axis and delayed time samples of the high-level sinewave on a second axis. - View Dependent Claims (15, 16, 17, 18)
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19. A system for measuring a non-linear distortion created by a signal path, the system comprising:
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a receiver configured to receive an impaired reference test signal, wherein the impaired reference test signal comprises a reference test signal as impaired while traversing a signal path; and
a digital signal processor connected to receive the impaired reference test signal, wherein the digital signal processor is configured to;
compute an impulse response of the signal path using a copy of the reference test signal and the impaired reference test signal; and
calculate the energy in the impulse response during time periods of the impulse response that contain primarily non-linear distortion energy. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A system for measuring a non-linear distortion created by a signal path comprising:
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a receiver for receiving an impaired reference test signal comprising a reference test signal as impaired while traversing a signal path, wherein the reference test signal comprises an OFDM reference test signal having at least one spectral hole; and
a digital signal processor configured to determine the non-linear distortion created by the signal path from energy contained within the at least one spectral hole. - View Dependent Claims (32, 33)
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34. A system for determining a transfer function of a signal path comprising:
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a receiver for receiving a two-burst waveform as impaired while traversing a signal path, wherein the two-burst waveform comprises a low-level sinewave part and a high-level sinewave part; and
a digital signal processor configured to determine a non-linear transfer function of the signal path by plotting the time samples of the low-level sinewave on a first axis and delayed time samples of the high-level sinewave on a second axis. - View Dependent Claims (35, 36, 37, 38, 39)
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40. A method for measuring non-linear distortion created by a signal path, the method comprising:
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receiving an impaired reference test signal, wherein the impaired reference test signal comprises a reference test signal as impaired while traversing a signal path;
computing an impulse response of the signal path using a copy of the reference test signal and the impaired reference test signal; and
calculating the energy in the impulse response during time periods of the impulse response that contain primarily non-linear distortion energy. - View Dependent Claims (41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51)
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52. A method for measuring non-linear distortion created by a signal path, the method comprising:
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receiving an impaired reference test signal comprising a reference test signal as impaired while traversing a signal path, wherein the reference test signal comprises an OFDM reference test signal having at least one spectral hole;
determining the non-linear distortion created by the signal path from energy contained within the at least one spectral hole. - View Dependent Claims (53, 54)
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55. A method for determining a transfer function of a signal path comprising:
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receiving a two-burst waveform as impaired while traversing a signal path, wherein the two-burst waveform comprises a low-level sinewave part and a high-level sinewave part; and
determining a non-linear transfer function of the signal path by plotting the time samples of the low-level sinewave on a first axis and delayed time samples of the high-level sinewave on a second axis. - View Dependent Claims (56, 57, 58, 59, 60)
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61. A device for measuring non-linear distortion created by a signal path, the device comprising:
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receiving circuitry configured to receive an impaired reference test signal, wherein the impaired reference test signal comprises a reference test signal as impaired while traversing a signal path; and
signal processing circuitry connected to receive the impaired reference test signal, wherein the signal processing circuitry is configured to;
compute an impulse response of the signal path using;
a copy of the reference test signal and the impaired reference test signal; and
calculate the energy in the impulse response during time periods of the impulse response that contain primarily non-linear distortion energy. - View Dependent Claims (62, 63, 64, 65, 66, 67, 68, 69, 70, 71)
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72. A device for measuring non-linear distortion created by a signal path, the device comprising:
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receiving circuitry configured to receive an impaired reference test signal comprising a reference test signal as impaired while traversing a signal path, wherein the reference test signal comprises an OFDM reference test signal having at least one spectral hole; and
signal processing circuitry configured to determine non-linear distortion created by the signal path from energy contained within the at least one spectral hole. - View Dependent Claims (73)
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74. A device for determining a transfer function of a signal path, the device comprising:
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receiving circuitry configured to receive a two-burst waveform as impaired while traversing a signal path, wherein the two-burst waveform comprises a low-level sinewave part and a high-level sinewave part; and
signal processing circuitry configured to determine a non-linear transfer function of the signal path by plotting the time samples of the low-level sinewave on a first axis and delayed time samples of the high-level sinewave on a second axis. - View Dependent Claims (75, 76, 77, 78)
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Specification