Hybrid amplitude/phase comparison direction finding system
First Claim
1. A system for measuring an angular position of an aircraft with respect to a reference ground location, comprising:
- a pair of antennas disposed at said ground location with each antenna of said pair having an antenna beam pointing in a different direction from the other and independently receiving electromagnetic energy propagating from the aircraft'"'"'s position;
an electronic memory having stored calibration data corresponding to premeasured amplitude and phase radiation patterns of said antennas, as a function of frequency and angle from a common reference plane;
receiving means, coupled to said antenna pair, for converting said electromagnetic energy independently received by said antennas to a lower frequency, and for detecting the frequency of said propagating electromagnetic energy to provide a measured frequency value;
means coupled to said receiving means, for comparing the amplitude and phase of said electromagnetic energy independently received by said antennas wherein a relative amplitude value and a relative phase value are provided; and
processing means, coupled to said receiving means, said means for comparing, and to said memory, for determining the angular position of said aircraft from said measured frequency value, said relative amplitude value, said relative phase value and said calibration data.
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Accused Products
Abstract
A hybrid amplitude/phase comparison direction finding system for aircraft, employing a unique calibration system to compensate for tolerance variations in the antennas. The calibration system utilizes a programmable read only memory (PROM) for each antenna pair, wherein calibration data from pre-measured antenna patterns of the associated antennas are stored. The calibration data preferably includes measured relative amplitude (electromagnetic field strength) and phase data, as a function of frequency and angle from a common reference plane, for the associated antenna pair. This calibration data is stored in a PROM which is preferably disposed within an assembly which includes the antenna pair. A system processor can then retrieve the calibration data during system operation, whereupon angle of arrival measurements can be performed with improved accuracy.
72 Citations
20 Claims
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1. A system for measuring an angular position of an aircraft with respect to a reference ground location, comprising:
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a pair of antennas disposed at said ground location with each antenna of said pair having an antenna beam pointing in a different direction from the other and independently receiving electromagnetic energy propagating from the aircraft'"'"'s position; an electronic memory having stored calibration data corresponding to premeasured amplitude and phase radiation patterns of said antennas, as a function of frequency and angle from a common reference plane; receiving means, coupled to said antenna pair, for converting said electromagnetic energy independently received by said antennas to a lower frequency, and for detecting the frequency of said propagating electromagnetic energy to provide a measured frequency value; means coupled to said receiving means, for comparing the amplitude and phase of said electromagnetic energy independently received by said antennas wherein a relative amplitude value and a relative phase value are provided; and processing means, coupled to said receiving means, said means for comparing, and to said memory, for determining the angular position of said aircraft from said measured frequency value, said relative amplitude value, said relative phase value and said calibration data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 16)
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13. A system for measuring an angular direction of incoming electromagnetic energy, comprising:
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an antenna assembly including at least two antennas for independently receiving the incoming electromagnetic energy, and an electronic memory having stored calibration data indicative of pre-measured radiation pattern characteristics of said antennas; means coupled to said antennas for providing a frequency measurement of the incoming electromagnetic energy; means coupled to said antennas for providing comparison parameters indicative of a difference between the electromagnetic energy independently received by said antennas, wherein said comparison parameters include a relative phase value and a relative amplitude value of the electromagnetic energy independently received by said antennas; processing means, separate from said antenna assembly and coupled to said electronic memory, for retrieving said calibration data and determining said angular direction from said comparison parameters, said frequency measurement and said calibration data. - View Dependent Claims (14, 15)
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17. A method of measuring an angular direction of incoming electromagnetic energy, comprising:
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providing at least two antennas disposed in a fixed relationship to one another; measuring radiation patterns of said antennas, said radiation patterns including both phase patterns and amplitude patterns as a function of frequency and angle from a common reference plane of said antennas; storing data indicative of said radiation patterns in an electronic memory; independently receiving said incoming electromagnetic energy with each of said antennas; detecting the frequency of the electromagnetic energy independently received by said antennas; comparing the phase of the electromagnetic energy independently received by said two antennas to provide a relative phase value; comparing the amplitude of the electromagnetic energy independently received by said two antennas to provide a relative amplitude value; determining said angular direction from said frequency detected, said relative phase value, said relative amplitude value and said data in said electronic memory. - View Dependent Claims (18, 19, 20)
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Specification