Method and apparatus for controlling a biphase modulation to improve autocorrelation in pseudorandom noise coded systems
First Claim
1. A method for improving autocorrelation and enhancing out of range rejection (ORR) in a pseudorandom noise (PN) coded system that uses biphase modulation by controlling a parameter associated with a biphase modulator, comprising the steps of:
- phase modulating a carrier signal with a binary PN code sequence thereby generating a biphase modulated signal;
obtaining a measure of power of a center spectral component of said biphase modulated signal;
comparing said power measured in said center spectral component with a reference power;
generating a control signal in response to said comparison for use in adjusting a parameter of said biphase modulator thereby achieving a desired power spectrum for said biphase modulated signal for improving autocorrelation of the PN coded system.
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Abstract
This invention relates to a method and apparatus for controlling a biphase modulator (602, 702) to improve autocorrelation in pseudorandom noise coded systems. The biphase modulator modulates a carrier frequency with one of two phase states responsive to a pseudorandom noise (PN) binary code sequence. The spectrum (610, 710) at the output of the biphase modulator comprises a plurality of spectral lines separated by the code repetition frequency, including a center spectral line (611, 711) and at least one adjacent spectral line (612-615, 712-717). The magnitude of the center spectral line is measured and compared to a reference to produce a control signal which is responsive to the magnitude of the center spectral line. This control signal is supplied to the biphase modulator for maintaining a predetermined magnitude of the center spectral line thereby achieving a desired spectrum output and improving autocorrelation of the system.
16 Citations
19 Claims
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1. A method for improving autocorrelation and enhancing out of range rejection (ORR) in a pseudorandom noise (PN) coded system that uses biphase modulation by controlling a parameter associated with a biphase modulator, comprising the steps of:
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phase modulating a carrier signal with a binary PN code sequence thereby generating a biphase modulated signal; obtaining a measure of power of a center spectral component of said biphase modulated signal; comparing said power measured in said center spectral component with a reference power; generating a control signal in response to said comparison for use in adjusting a parameter of said biphase modulator thereby achieving a desired power spectrum for said biphase modulated signal for improving autocorrelation of the PN coded system. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A pseudorandom noise (PN) coded system utilizing a biphase modulator for improving autocorrelation and for enhancing out of range rejection of the system by controlling a parameter associated with the biphase modulator, comprising:
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a biphase modulator for generating a phase modulated signal comprised of a carrier frequency signal modulated with a PN code sequence; means, coupled to said biphase modulator, for measuring power of a center spectral component of said phase modulated signal; means for comparing said center spectral component with a reference power signal; and means, responsive to said means for comparing, for generating a control signal for adjusting a parameter of said biphase modulator thereby achieving a desired power spectrum of said phase modulated signal and improving autocorrelation of the PN coded system. - View Dependent Claims (8, 9, 10, 11)
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12. A control loop for improving autocorrelation in pseudorandom noise (PN) coded system, comprising:
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a biphase modulator for generating a phase modulated signal comprised of a carrier frequency signal modulated with a PN code sequence; and a control signal generator, responsive to said phase modulated signal, for measuring a magnitude of a center spectral component of said phase modulated signal and for supplying an adjustable control signal to said biphase modulator for maintaining a predetermined magnitude of said center spectral component and for improving autocorrelation of the PN coded system. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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Specification