 Clock signal extracting circuit |
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| Method and apparatus for a low voltage high current bi-directional termination voltage regulator |
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| Automatic gain control circuit for a modem receiver |
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| All-digital method and apparatus for demodulating an analog signal |
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| Test circuit of multiplex equipment |
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Low probability of interception relative position determination system
| Details |
Inventors: Wagner, Kenneth M.; Stahley, William; Van Cleave, James R.;
Assignee: NavCom Defence Electronics, Inc. (El Monte, CA)
Primary Examiner: Swann; Tod
Assistant Examiner:
Attorney, Agent or Firm: Cushman, Darby & Cushman
A radio system for determining the range and bearing of mobile equipment, such as an aircraft, relative to reference equipment such as an aircraft carrier, with low probability of interception (LPI). The aircraft remains equipped with high power range and bearing determination equipment, such as TACAN equipment. Reference equipment transmits a LPI beacon, such as a pseudo noise code spread spectrum signal through a rotating beam antenna to amplitude modulate the beacon as a function of antenna orientation. The PN code is inverted as the antenna passes through a reference bearing. Mobile LPI equipment determines bearing and generates a high power signal, such as an emulated TACAN beacon signal. High power range and bearing equipment extracts bearing information from the emulated signal and display it. Range can be determined in a cooperative mode. Mobile LPI equipment transmits a LPI interrogation signal. Reference LPI equipment returns a LPI reply signal. Mobile LPI equipment determines range from the delay time, and generates a high power reply signal from which the high power range and bearing position determination means can extract and display range information. |
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DETAILED DESCRIPTION The relative radio navigation system of the present invention provides add-on LPI position and range determination.
It determines range and bearing to/from a mobile apparatus, such as an aircraft, to a reference apparatus, such as an aircraft carrier with spread spectrum techniques having a low probability of interception (LPI).
The preferred embodiment retains the airborne elements of the TACAN range and bearing determination system by inserting an add-on LPI unit on both the airborne TACAN equipment and the mobile or fixed TACAN beacon.
Reference apparatus (such as on an aircraft carrier) generates a LPI beacon signal, such as a PN coded spread spectrum signal, through a rotating beam antenna and modulates the beacon signal with beam orientation information.
The airborne-side add-on LPI unit receives the LPI beacon signal, and generates a signal emulating a shipboard TACAN transponder beacon signal.
The airborne TACAN equipment receives the emulated beacon signal from the airborne LPI unit on the aircraft, computes range and bearing, and drives displays for the pilot.
When a pilot selects a channel designated as an LPI channel, the airborne TACAN unit generates a high power interrogation signal.
The airborne add-on LPI unit measures the frequency and determines that it is designated an LPI channel.
The add-on LPI unit isolates the TACAN unit from the antenna and transmits a LPI interrogation signal.
Reference apparatus on the beacon (e.
g.
carrier) responds with its own LPI reply signal from which the airborne LPI unit can determine position.
The airborne LPI unit determines position by processing the LPI beacon signal and generates a signal emulating a shipboard TACAN reply.
The airborne TACAN equipment receives the emulated reply and displays position to the pilot.
The interrogation signal can be a PN coded spread spectrum signal, and the reply can be the same PN code sequence synchronized to the interrogation signal.
The airborne LPI unit can determine range from the phase delay between the interrogation and reply sequences and bearing from coded bearing data imbedded in the LPI beacon signal
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Multiplexer-related 
