Discrete fourier transform direction finding apparatus
First Claim
1. A circuit for finding the direction of an RF signal received on two antennae separated by a known distance "d" comprising:
- an RF signal receiver coupled to each antenna for receiving the antenna signals and generating orthogonal I and Q baseband signal outputsa CCD Chirp-Z Discrete Fourier transform circuit coupled to each receiver for receiving, sampling and separating said I and Q baseband signals into components by frequency and amplitude,a control circuit coupled to said CCD Chirp-Z Discrete Fourier transform circuit for controlling the sampling rate at which the I and Q signal components are sampled and separated to adjust frequency resolution, andmeans coupled to the CCD Chirp-Z Discrete Fourier transform circuit for utilizing the sampled and separated baseband I and Q signal components to obtain the direction of propagation of the RF signal.
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Abstract
A discrete fourier transform direction finding apparatus for performing a direction finding function on signals received through two antennae separated by a known distance. The outputs of the respective antennae are connected to first and second receiver channels which convert the received signals down to baseband and provide orthogonal I and Q channel outputs. A common local oscillator is used to maintain phase coherency between the channels and AGC signals are provided to maintain identical delays in the receiver RF paths. The processed signals from each receiver channel are than fed into a respective charge coupled device Chirp-Z transform (discrete fourier transform) circuit to produce real and imaginary components of the received signals. These signals are then converted to digital form and are used by subsequent circuitry to determine the angle of arrival of the received signal.
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Citations
8 Claims
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1. A circuit for finding the direction of an RF signal received on two antennae separated by a known distance "d" comprising:
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an RF signal receiver coupled to each antenna for receiving the antenna signals and generating orthogonal I and Q baseband signal outputs a CCD Chirp-Z Discrete Fourier transform circuit coupled to each receiver for receiving, sampling and separating said I and Q baseband signals into components by frequency and amplitude, a control circuit coupled to said CCD Chirp-Z Discrete Fourier transform circuit for controlling the sampling rate at which the I and Q signal components are sampled and separated to adjust frequency resolution, and means coupled to the CCD Chirp-Z Discrete Fourier transform circuit for utilizing the sampled and separated baseband I and Q signal components to obtain the direction of propagation of the RF signal. - View Dependent Claims (2, 3)
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4. A circuit for finding the direction of an RF signal received on two antennae separated by known distance comprising:
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an RF signal receiver coupled to each antenna for receiving the antenna signals and generating orthogonal I and Q baseband signal outputs; a means for sampling said orthogonal I and Q baseband signal outputs; means for varying the sampling rate of said means for sampling; means, including a CCD Chirp-Z Discrete Fourier transform circuit, coupled to said means for sampling, for generating real and imaginary coefficients of the Discrete Fourier transform of said sampled baseband signal; and means coupled to said transform circuit for utilizing said real and imaginary coefficients to obtain the direction of propagation of the RF signal.
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5. A method of finding the direction of an RF signal received on two antennae separated by a known distance "d" comprising the steps of:
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providing orthogonal I and Q baseband signal outputs from an RF receiver coupled to each antenna, sampling and separating the I and Q baseband signals into components by frequency and amplitude using a CCD Chip-Z Discrete Fourier transform circuit, controlling the sampling rate at which the CCD Chirp-Z Discrete Fourier transform circuit generates the separated I and Q signal components to adjust frequency resolution, and calculating the direction in which the RF signal is propagated utilizing the sampled and separated baseband I and Q signal components. - View Dependent Claims (6, 7, 8)
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Specification