Automatic phase and gain balance controller for a baseband processor
First Claim
1. An automatic gain and phase balance controller for nulling phase and amplitude imbalance which may be present between the in-phase and quadrature signal generation channels of a baseband processor, said controller comprising:
- means for generating a pilot signal;
means for conducting said pilot signal to said in-phase and quadrature signal generation channels of said baseband processor, said channels being governed by said pilot signal to generate composite in-phase and quadrature signals including phase and amplitude error signals representative of the imbalance between said in-phase and quadrature signal generation channels;
means for sensing and isolating said phase and amplitude error signals from said composite in-phase and quadrature signals; and
feedback circuit means governed by said isolated amplitude and phase error signals to correct for the imbalance between the in-phase and quadrature channels by adjusting amplitude and phase parameters associated with the signal generation of said channels.
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Abstract
An automatic phase and gain balance controller is incorporated in a typical baseband processor of a MTI radar system employing doppler processing techniques to effect balancing adjustments in the in-phase (I) and quadrature (Q) signal generation channels for substantially eliminating spurious image frequency component formations which may result from any unbalance therein. More specifically, the automatic controller provides two substantially non-interactive servo control loops to maintain balance between the I and Q signal generation channels by performing balancing adjustments on two adjustment parameters, namely phase and amplitude. Phase and amplitude imbalance errors between the I and Q channel are obtained in response to a pilot signal which is injected into the baseband processor of the MTI radar receiver, perferably during the dead times of the interpulse periods of pulsed reception. Accordingly these phase and amplitude imbalance errors are sensed and separately isolated by the automatic controller and each sensed error is used to control the servo control loop respectively associated therewith.
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Citations
22 Claims
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1. An automatic gain and phase balance controller for nulling phase and amplitude imbalance which may be present between the in-phase and quadrature signal generation channels of a baseband processor, said controller comprising:
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means for generating a pilot signal; means for conducting said pilot signal to said in-phase and quadrature signal generation channels of said baseband processor, said channels being governed by said pilot signal to generate composite in-phase and quadrature signals including phase and amplitude error signals representative of the imbalance between said in-phase and quadrature signal generation channels; means for sensing and isolating said phase and amplitude error signals from said composite in-phase and quadrature signals; and feedback circuit means governed by said isolated amplitude and phase error signals to correct for the imbalance between the in-phase and quadrature channels by adjusting amplitude and phase parameters associated with the signal generation of said channels. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A radar system which transmits radar signal pulses spaced apart by periods of time within which radar echo signals are received for processing thereby, said radar system employing a baseband processor comprised of two mixer channels for generating analog in-phase and quadrature signal components of the incoming radar echo signals with respect to the phase of a master oscillator signal, said in-phase and quadrature signals being representative of modulation frequency components of the radar echo signals, said one channel mixing the in-coming signal with a signal derived from the master oscillator signal and in phase therewith and said other channel mixing the in-coming signal with a signal derived from the master oscillator and shifted by 90°
- with respect thereto using a phase shifter, said mixer channels becoming phase and amplitude unbalanced in adjustment in the course of performance thereof causing imbalance phase and amplitude errors which render spurious image frequency components which are representative of false radar echo signals, said radar system comprising;
a pilot signal generator governed by a signal derived from the master oscillator signal and a pilot clock signal to generate a pilot signal; a switching means operative to conduct one of the in-coming radar echo signal and the pilot signal to the mixer channels; means for sensing and isolating the phase and amplitude imbalance errors from the in-phase and quadrature signal components generated from the pilot signal; feedback circuit means governed by said isolated phase and amplitude imbalance errors to correct for the unbalance in phase and amplitude adjustment between the mixer channels, thereby substantially eliminating the spurious image frequency components which are representative of false radar echo signals. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
- with respect thereto using a phase shifter, said mixer channels becoming phase and amplitude unbalanced in adjustment in the course of performance thereof causing imbalance phase and amplitude errors which render spurious image frequency components which are representative of false radar echo signals, said radar system comprising;
Specification