Autocalibrating interferometer
First Claim
1. An autocalibration subsystem for a direction-finding interferometer, said interferometer having first and second antennas, first and second signal channels, and a primary comparator for comparing signals according to a predetermined characteristic, said first signal channel being adapted for transmitting the output of said first antenna to said primary comparator, said second signal channel being adapted for transmitting the output of said second antenna to said primary comparator, said subsystem comprising:
- first and second reversing switches, each reversing switch means having an input port, an output port, a third port and a fourth port;
a signal source for providing a calibrate signal to the input port of each of said reversing switches;
a secondary comparator for comparing two signals according to said predetermined characteristic, said secondary comparator having first and second inputs, said first input of said secondary comparator being adapted for receiving a signal from said output port of said first reversing switch, said second input of said secondary comparator being adapted for receiving a signal from said output port of said second reversing switch, said secondary comparator being adapted for detecting the phase difference of signals received at its first and second inputs;
first and second couplers located adjacent respective said antennas, each coupler having first and second inputs and an output, each said coupler output serving as an input to the respective said signal channel, each said first input of each said coupler being electrically connected to the output of the respective said antenna, each said second input of each said coupler being electrically connected to said third port and said fourth port of the respective said reversing switch so that a signal path exists between respective third and fourth ports; and
controller means for alternately providing first and second concurrent switch conditions in said reversing switches so that in said first condition each said input port is electrically connected to the respective said third port and each said output port is electrically connected to the respective said fourth port, and so that in said second condition each said input port is electrically connected to the respective said fourth port and each said output port is electrically connected to the respective said third port.
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Accused Products
Abstract
A direction-finding interferometer (100) includes a novel autocalibration subsystem using bi-directional transmissions at a common frequency. The interferometer determines direction using a primary phase comparator (15) to assess the phase differences in signals transmitted by signal channels (13) from multiple antennas (11). The signal channels may include RF amplifiers (17), mixers (19) coupled to a local oscillator (23), IF amplifiers (21), and transmission lines.
The autocalibration subsystem employs a frequency synthesizer (25) as a calibration signal source. The calibration signal path is directed between reversing switches (40) and couplers (33) in alternating directions via transmission lines (57 and 59). In either direction, the calibration is split so that part of the signals are coupled into the signal channels, and the remaining part is directed to a secondary phase comparator (131). The outputs of the primary and secondary comparators provide the data necessary for autocalibration.
Other embodiments provide for a secondary comparator operating at a frequency range similar to that of the primary comparator. Gain autocalibration is also described.
22 Citations
12 Claims
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1. An autocalibration subsystem for a direction-finding interferometer, said interferometer having first and second antennas, first and second signal channels, and a primary comparator for comparing signals according to a predetermined characteristic, said first signal channel being adapted for transmitting the output of said first antenna to said primary comparator, said second signal channel being adapted for transmitting the output of said second antenna to said primary comparator, said subsystem comprising:
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first and second reversing switches, each reversing switch means having an input port, an output port, a third port and a fourth port; a signal source for providing a calibrate signal to the input port of each of said reversing switches; a secondary comparator for comparing two signals according to said predetermined characteristic, said secondary comparator having first and second inputs, said first input of said secondary comparator being adapted for receiving a signal from said output port of said first reversing switch, said second input of said secondary comparator being adapted for receiving a signal from said output port of said second reversing switch, said secondary comparator being adapted for detecting the phase difference of signals received at its first and second inputs; first and second couplers located adjacent respective said antennas, each coupler having first and second inputs and an output, each said coupler output serving as an input to the respective said signal channel, each said first input of each said coupler being electrically connected to the output of the respective said antenna, each said second input of each said coupler being electrically connected to said third port and said fourth port of the respective said reversing switch so that a signal path exists between respective third and fourth ports; and controller means for alternately providing first and second concurrent switch conditions in said reversing switches so that in said first condition each said input port is electrically connected to the respective said third port and each said output port is electrically connected to the respective said fourth port, and so that in said second condition each said input port is electrically connected to the respective said fourth port and each said output port is electrically connected to the respective said third port. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An autocalibration subsystem for a direction-finding interferometer, said interferometer having first and second antennas, first and second signal channels, and a primary comparator, said first signal channel being adapted for transmitting the output of said first antenna to said primary comparator, said second signal channel being adapted for transmitting the output of said second antenna to said comparator, said subsystem comprising:
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first and second reversing switches, each reversing switch means having an input port, an output port, a third port and a fourth port; a signal source for providing a calibrate signal to the input ports of said reversing switches; controller means for alternately providing first and second concurrent switch conditions in said reversing switches, in said first condition each said input port is electrically connected to the respective said third port and each said output port is electrically connected to the respective said fourth port, in said second condition each said input port is electrically connected to the respective said fourth port and each said output port is electrically connected to the respective said third port; first and second couplers located adjacent respective said antennas, each coupler having first and second inputs and an output, each said coupler output serving as an input to the respective said signal channel, each said first input of each said coupler being electrically connected to the output of the respective said antenna, each said second input of each said coupler being electrically connected to said third port and said fourth port of the respective said reversing switch so that a signal path exists between respective third and fourth ports; first and second transform means for transforming a signal received so as to be within the operational range of said secondary comparator; a second comparator having first and second inputs, said first input of said secondary comparator being adapted for receiving a signal from said first transform means, said second input of said secondary comparator being adapted for receiving a signal from second transform means, said second comparator being adapted for detecting the phase difference of signals received at its first and second inputs; and means for alternating between two switch conditions so that in said first condition the output of said first reversing switch is directed to said first transform means and the output of said second reversing switch is directed to said second transform means, and so that in said second condition the output of said first reversing switch is directed to said second transform means and the output of said second reversing switch is directed to said first transform means so that relative phase shifts introduced by the respective said transform means can be measured.
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9. An autocalibration subsystem for a direction-finding interferometer, said interferometer having first and second antennas, first and second signal channels, and a primary comparator for comparing signals according to a predetermined characteristic, said first signal channel being adapted for transmitting the output of said first antenna to said primary comparator, said second signal channel being adapted for transmitting the output of said second antenna to said primary comparator, said subsystem comprising:
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first and second reversing switches, each reversing switch means having an input port, and output port, a third port and a fourth port; a signal source for providing a calibrate signal to the input port of each of said reversing switches; a secondary comparator for comparing two signals according to said predetermined characteristic, said secondary comparator having first and second inputs, said first input of said secondary comparator being adapted for receiving a signal from said output port of said first reversing switch, said second input of said secondary comparator being adapted for receiving a signal from said output port of said second reversing switch, said secondary comparator being adapted for detecting the phase difference of signals received at its first and second inputs; first and second couplers located adjacent respective said antennas, each coupler having first and second inputs and an output, each said coupler output serving as an input to the respective said signal channel, each said first input of each said coupler being electrically connected to the output of the respective said antenna, each said second input of each said coupler being electrically connected to said third port and said fourth port of the respective reversing switch so that a signal path exists between respective third and fourth ports; controller means for alternately providing first and second concurrent switch conditions in said reversing switches so that in said first condition each said input port is electrically connected to the respective said third port and each said output port is electrically connected to the respective said fourth port, and so that in said second condition each said input port is electrically connected to the respective fourth port and each said output is electrically connected to the respective third port; and first and second transform means for transforming the signal from the output port of the respective reversing switch so as to be within the operational range of said secondary comparator, each said transform means being electrically located between the respective said reversing switch and the respective input of said secondary comparator; and means for replacing the signals from said output ports with a common signal so that relative shifts in the predetermined signal characteristic introduced by the respective transform means can be measured.
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10. An autocalibration subsystem for a direction-finding interferometer, said interferometer having first and second antennas, first and second signal channels, and a primary comparator for comparing signals according to a predetermined characteristic, said first signal channel being adapted for transmitting the output of said first antenna to said primary comparator, said second signal channel being adapted for transmitting the output of said second antenna to said primary comparator, said subsystem comprising:
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first and second reversing switches, each of the reversing switches means having an input port, and output port, a third port and a fourth port; a signal source for providing a calibrate signal to the input port of each of said reversing switches; a secondary comparator for comparing two signals according to said predetermined characteristic, said secondary comparator having first and second inputs, said first input of said secondary comparator being adapted for receiving a signal from said output port of said first reversing switch, said second input of said secondary comparator being adapted for receiving a signal from said output port of said second reversing switch, said secondary comparator being adapted for detecting the phase difference of signal received at its first and second inputs; first and second couplers located adjacent respective said antennas, each coupler having first and second inputs and an output, each said coupler output serving as an input to the respective said signal channel, each said first input of each said coupler being electrically connected to the output of the respective said antenna, each said second input of each said coupler being electrically connected to said third port and said fourth port of the respective reversing switch so that a signal path exists between respective third and fourth ports; controller means for alternately providing first and second concurrent switch conditions in said reversing switches so that in said first condition each said input port is electrically connected to the respective said third port and each said output port is electrically connected to the respective said fourth port, and so that in said second condition each said input port is electrically connected to the respective fourth port and each said output is electrically connected to the respective third port; and first and second signal transform means, said first signal transform means being electrically connected to said first input of said secondary comparator, said second signal transform means being electrically connected to said second input of said secondary comparator, each signal transform mean having an input for receiving an output from one of said reversing switches; and means for commutating the outputs of said reversing switches between the inputs to said first and second signal transform means. - View Dependent Claims (11, 12)
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Specification