Passband reflectometer
First Claim
1. An apparatus comprising:
- a passband transmitter configured to generate a drive signal based on a bit sequence;
an interface configured to convert the drive signal into a probe signal, apply the probe signal to a channel under test, and receive a response signal corresponding to the probe signal back from said channel;
a passband receiver configured to receive, from the interface, an input signal corresponding to the response signal and to convert said input signal into a receiver-baseband signal; and
a high-pass filter coupled between the interface and the passband receiver, wherein;
the probe signal is spectrally limited to a spectral band located at frequencies higher than a first threshold frequency, wherein the first threshold frequency is a nonzero frequency;
the apparatus is configured to characterize an impulse response of the channel under test based on the bit sequence and the receiver-baseband signal; and
the high-pass filter has a cut-off frequency that is lower than or about the same as the first threshold frequency.
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Accused Products
Abstract
A time-domain (TD) reflectometer that is designed to operate based on probe and response signals that are substantially fully spectrally confined to a designated frequency passband. In one embodiment, the TD reflectometer uses a passband transmitter to generate the probe signal based on a pseudo-random bit sequence and a passband receiver to demodulate the response signal. The TD reflectometer determines the impulse response of a channel under test based on cross-correlation of the transmitter and receiver baseband signals. In various embodiments, the TD reflectometer can be designed to operate in an acoustic-frequency range, a radio-frequency range, or an optical-frequency range. Due to its passband configuration, the TD reflectometer is advantageously capable of determining impulse responses without disrupting the operation and/or interfering with normal functions of the tested channel.
51 Citations
21 Claims
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1. An apparatus comprising:
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a passband transmitter configured to generate a drive signal based on a bit sequence; an interface configured to convert the drive signal into a probe signal, apply the probe signal to a channel under test, and receive a response signal corresponding to the probe signal back from said channel; a passband receiver configured to receive, from the interface, an input signal corresponding to the response signal and to convert said input signal into a receiver-baseband signal; and a high-pass filter coupled between the interface and the passband receiver, wherein; the probe signal is spectrally limited to a spectral band located at frequencies higher than a first threshold frequency, wherein the first threshold frequency is a nonzero frequency; the apparatus is configured to characterize an impulse response of the channel under test based on the bit sequence and the receiver-baseband signal; and the high-pass filter has a cut-off frequency that is lower than or about the same as the first threshold frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of characterizing an impulse response, the method comprising:
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generating a drive signal based on a bit sequence using a passband transmitter; converting the drive signal into a probe signal using an interface, wherein the probe signal is spectrally limited to a spectral band located at frequencies higher than a first threshold frequency, wherein the first threshold frequency is a nonzero frequency; applying the probe signal to a channel under test using the interface; receiving a response signal corresponding to the probe signal back from said channel, wherein the interface is configured to receive said response signal; generating a receiver-baseband signal based on the response signal using a passband receiver; and characterizing an impulse response of the channel based on the bit sequence and the receiver-baseband signal; and wherein the step of generating the drive signal using the passband transmitter comprises; converting the bit sequence into a corresponding sequence of constellation symbols; and converting the sequence of constellation symbols into a transmitter-baseband signal, wherein; the drive signal is generated based on the transmitter-baseband signal; and the impulse response is determined based on a correlation between the receiver-baseband signal and the transmitter-baseband signal. - View Dependent Claims (14, 15, 16, 17, 18)
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19. An apparatus comprising:
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a passband transmitter configured to generate a drive signal based on a bit sequence; an interface configured to convert the drive signal into a probe signal, apply the probe signal to a channel under test, and receive a response signal corresponding to the probe signal back from said channel; and a passband receiver configured to receive, from the interface, an input signal corresponding to the response signal and to convert said input signal into a receiver-baseband signal, wherein; the probe signal is spectrally limited to a spectral band located at frequencies higher than a first threshold frequency, wherein the first threshold frequency is a nonzero frequency; the apparatus is configured to characterize an impulse response of the channel under test based on the bit sequence and the receiver-baseband signal; and the passband transmitter comprises; a coder module configured to convert the bit sequence into a corresponding sequence of constellation symbols; and a transmit filter configured to convert the sequence of constellation symbols into a transmitter-baseband signal; the passband transmitter is configured to generate the drive signal based on the transmitter-baseband signal; and the apparatus is configured to determine the impulse response based on a correlation between the receiver-baseband signal and the transmitter-baseband signal.
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20. An apparatus comprising:
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a passband transmitter configured to generate a drive signal based on a bit sequence; an interface configured to convert the drive signal into a probe signal, apply the probe signal to a channel under test, and receive a response signal corresponding to the probe signal back from said channel; and a passband receiver configured to receive, from the interface, an input signal corresponding to the response signal and to convert said input signal into a receiver-baseband signal, wherein; the probe signal is spectrally limited to a spectral band located at frequencies higher than a first threshold frequency, wherein the first threshold frequency is a nonzero frequency; the apparatus is configured to characterize an impulse response of the channel under test based on the bit sequence and the receiver-baseband signal; and the passband receiver comprises; a receive filter configured to correct the input signal for filtering effects of the interface; and a demodulator configured to down-convert the corrected input signal to generate the receiver-baseband signal.
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21. An apparatus comprising:
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a passband transmitter configured to generate a drive signal based on a bit sequence; an interface configured to convert the drive signal into a probe signal, apply the probe signal to a channel under test, and receive a response signal corresponding to the probe signal back from said channel; and a passband receiver configured to receive, from the interface, an input signal corresponding to the response signal and to convert said input signal into a receiver-baseband signal, wherein; the probe signal is spectrally limited to a spectral band located at frequencies higher than a first threshold frequency, wherein the first threshold frequency is a nonzero frequency; the apparatus is configured to characterize an impulse response of the channel under test based on the bit sequence and the receiver-baseband signal; the interface is designed to be coupled to a human vocal tract; and the apparatus is an acoustic reflectometer.
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Specification