I/Q compensation of frequency dependent response mismatch in a pair of analog low-pass filters
First Claim
1. A method for determining a gain error estimate and a delay error estimate in a pair of filters comprising:
- a) applying a test signal to an input of both filters;
b) measuring an output signal at the output of each filter;
c) determining the gain error at a first frequency and a phase error at a second frequency; and
d) determining the delay error estimate using the determined phase error, wherein the delay error estimate is constant with frequency.
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Accused Products
Abstract
Frequency dependent I/Q imbalance in real I/Q filter pairs compensation may be performed using a simple compensation module, placed in the receiver/transmitter chain, with a gain adjustment coefficient and a delay adjustment coefficient. The gain adjustment coefficient may be determined by amplitude measurements conducted at a selected frequency near the center of the band-pass region of the filters. The delay adjustment coefficient may be determined by phase measurements conducted at a selected frequency near the edge of the band-pass region of the filters. Statistical analysis may be used to determine types of real filters that are better suited for the compensation method and to select the test frequencies that should be used.
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Citations
58 Claims
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1. A method for determining a gain error estimate and a delay error estimate in a pair of filters comprising:
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a) applying a test signal to an input of both filters;
b) measuring an output signal at the output of each filter;
c) determining the gain error at a first frequency and a phase error at a second frequency; and
d) determining the delay error estimate using the determined phase error, wherein the delay error estimate is constant with frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. Apparatus for use in determining a gain error estimate and a delay error estimate in a pair of filters comprising:
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a) a signal generator for applying a test signal to an input of each of the filters;
b) means for measuring an output signal at the output of each of the filters;
c) means for determining the gain error at a first frequency and a phase error at a second frequency; and
d) a means for determining the delay error estimate using the determined phase error, wherein the delay error estimate is constant with frequency. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 58)
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56. Apparatus for use in compensating I/Q imbalance in a low pass filter pair in at least one of a receiver, a transmitter, and a transceiver, using a delay error and a gain error determined using a test system including:
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a generator for applying a test signal to the inputs of the low path filter pair;
means for measuring an output signal at the output of each filter in the low pass filter pair;
means for determining the gain error at a first frequency and a phase error at a second frequency; and
means for determining the delay error estimate using the determined phase error, wherein the delay error estimate is constant with frequency, said apparatus comprising;
a) means for compensating for the determined delay error using an implementation of a delay function, wherein, the delay function is substantially constant with frequency; and
b) means for compensating the determined gain error using an implementation of a gain function, wherein the gain function is substantially constant with frequency. - View Dependent Claims (57)
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Specification