Measuring the I/Q impairments of a receiver
AssigneeNational Instruments Corporation
InventorsStephen L. Dark, Christopher J. Behnke
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Abstract
Systems and methods for measuring transmitter and/or receiver I/Q impairments are disclosed, including iterative methods for measuring transmitter I/Q impairments using shared local oscillators, iterative methods for measuring transmitter I/Q impairments using intentionally-offset local oscillators, and methods for measuring receiver I/Q impairments. Also disclosed are methods for computing I/Q impairments from a sampled complex signal, methods for computing DC properties of a signal path between the transmitter and receiver, and methods for transforming I/Q impairments through a linear system.
Claims20
A computer-implemented method for determining I/Q impairments of a receiver, the method comprising:
- directing that an input signal be supplied to the receiver, wherein the input signal includes an isolated tone at displacement frequency f and includes a void interval around displacement frequency −f, wherein the receiver is configured to demodulate the input signal in order to obtain a sampled complex signal, wherein displacement frequencies f and −f are displacements relative to a local oscillator frequency of the receiver;
- computing the I/Q impairments of the receiver at frequency f based on the sampled complex signal;
- repeating said directing and said computing for values of the frequency f spanning a specified frequency band;
- storing the I/Q impairments of the receiver for said values of the frequency f in a memory.
A computer system for determining I/Q impairments of a receiver, the computer system comprising:
- a processor;
- and
- memory storing program instructions, wherein the program instructions, when executed by the processor, cause the processor to:
- direct that an input signal be supplied to the receiver, wherein the input signal includes an isolated tone at displacement frequency f and includes a void interval around displacement frequency −f, wherein the receiver is configured to demodulate the input signal in order to obtain a sampled complex signal, wherein displacement frequencies f and −f are displacements relative to a local oscillator frequency of the receiver;
- compute the I/Q impairments of the receiver at frequency f based on the sampled complex signal;
- repeat said directing and said computing for values of the frequency f spanning a specified frequency band;
- and
- store the I/Q impairments of the receiver for said values of the frequency f in a memory.
A non-transitory computer-accessible memory medium for determining I/Q impairments of a receiver, wherein the memory medium stores program instructions, wherein the program instructions, when executed by a computer system, cause the computer system to:
- direct that an input signal be supplied to the receiver, wherein the input signal includes an isolated tone at displacement frequency f and includes a void interval around displacement frequency −f, wherein the receiver is configured to demodulate the input signal in order to obtain a sampled complex signal, wherein displacement frequencies f and −f are displacements relative to a local oscillator frequency of the receiver;
- compute the I/Q impairments of the receiver at frequency f based on the sampled complex signal;
- repeat said directing and said computing for values of the frequency f spanning a specified frequency band;
- store the I/Q impairments of the receiver for said values of the frequency f in a memory.
Dependencies are inferred from the claim text.