Digital range computer systems for air navigation systems such as tacan

• US 3,969,616 A
• Filed: 06/29/1965
• Issued: 07/13/1976
• Est. Priority Date: 06/29/1965
• Status: Expired due to Term

• Current Assignee: GDE Systems, Inc. (The O'Gara Group, Inc.)
• Original Assignee: General Dynamics Corporation
• Inventors: Mimken, Frederick J.
• Primary Examiner(s): Morrison, Malcolm A.
• Assistant Examiner(s): Wise, Edward J.
• Application Number:
  US04/467,897
• Time in Patent Office: 4,032 Days
• Field of Search: 235/151.32, 343/7.3, 324/68, 328/109
• US Class Current: 701/218
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 13/70 for range tracking only
• CPC Class Codes: G01S 13/785 Distance Measuring Equipment [DME] systems

Abstract

A digital range computer which may be incorporated in a Tacan air navigation set is described. The computer includes a calculation unit which calculates the range from information as to the elapsed time between interrogation and reply signals. The signals are inputed to the calculation unit via the input control and range gate control unit. Another control unit is operated by the calculation unit and generates synthetic reply signals on the basis of the calculations previously made. The synthetic reply signals are used in the control unit so as to maintain the calculation unit operational on a continual basis, notwithstanding the absence of reply signals. The synthetic reply signals are also utilized by an acquisition control unit in order to condition the system, either in a search or tracking mode of operation.

Claims

1. A computer system for calculating the range between two stations which are in radio communication with each other, said system comprising:

a. calculation means for producing an output having a value corresponding to the elapsed time between the transmission of a signal from a first of said stations to a second of said stations and the reception of a signal transmitted from said second station to said first station in reply to said first station transmitted signal,

b. control means for supplying information to said calculation means respecting time of the occurrence of said first station transmitted signal and the time of reception of said reply signal, and

c. means operated by said calculation means when said calculation means output equals an expected value for operating said control means to supply information simulating the information respecting the reception of reply signals to said claculation means whereby to maintain the operation of said calculation means on a continuing basis notwithstanding that said reply signals are missing.

2. A computer system for calculating the range between two stations which are in radio communication with each other, a first of said stations transmitting successive signals to each of which the second of said stations transmits a reply signal, said system comprising

a. calculation means at said first station for producing an output having a value corresponding to the elapsed time between the transmission of a signal from said first station and the reception of said reply signal,

b. control means for supplying information to said claculation means respecting the times of the occurrence of each said successive first station transmitted signal and the reception of each said reply signal in response thereto,

c. means operated by said calculation means when said calculation means output corresponds in value to the elapsed time between a preceding signal from said first station and the reception of a reply signal in response thereto for supplying information to said control means respecting the time of occurrence of said last-named output, and

d. means included in said control means for supplying said last-named information to said claculation means in the event that a succeeding reply signal is not received.

3. A computer system for calculating the range between two stations which are in radio communication with each other, comprising

a. means for calculating said range on the basis of the time interval between the time of occurrence of a signal transmitted from a first of said stations to a second of said stations and the time of reception of a signal transmitted from said second station to said first station,

b. control means operative upon transmission of said signals from said first station and upon reception of said signals from said second station for initiating and terminating operation of said calculating means,

c. means operated by said calculation means when said calculation is not terminated within an interval of time related to the time interval between the time of transmission of said signals from said first station and the expected time of reception of said signals from said second station for terminating the operation of said calculating means, and

d. means operated by said calculating means for indicating the range calculations.

4. A computer for calculating the range between a first station and a second station which are in radio communication with each other and which cyclically transmit interrogation and reply signals, said computer comprising

a. means for calculating the range between said first station and said second station on the basis of the time interval between the time of transmission of said interrogation signal and the time of reception of said reply signal during each said cycle,

b. means responsive to said interrogation signal for operating said calculating means to initiate the range calculation,

c. means responsive to said reply signal for operating said calculating means to terminate said calculation,

d. means operated by said calculating means for terminating said calculation when said calculating means is operatively processing said range calculation a time interval after occurrence of said interrogation signal at least substantially equal to the time interval between the time of occurrence of said interrogation signal and the time of occurrence of said reply signal during a preceding one of said cycles, and

e. means included in said calculating means and operated by said reply signal for indicating said range calculation.

5. A computer system for computing the range between a first station and a second station which are in radio communication with each other and which repeatedly transmit interrogation signals and reply signals during successive cycles of operation, said computer system comprising

a. a calculation unit for calculating the range between said first station and said second station on the basis of the time interval between the time of occurrence of said interrogation signal and the time of reception of said reply signal and for storing such range calculation,

b. an input control unit responsive to said interrogation signal for initiating the operation of said calculation unit upon occurrence of each of said interrogation signals,

c. a range gate control unit responsive to the calculation stored in said calculation unit during a pre-existing cycle of operation thereof for supplying information to said input control unit as to the time interval after transmission of a succeeding interrogation signal, during which said input control unit is enabled to terminate operation of said calculation unit in response to a succeeding reply signal,

d. a missing reply signal control unit operated by said calculation unit for supplying additional information to said input control unit so as to terminate the operation of said calculation unit when said reply signal does not occur during said time interval within which said control unit is enabled, and

e. an acquisition control unit operated by said missing reply signal control unit and by said range gate control unit for conditioning said calculation unit to read out the range calculation made during each said cycle, so long as the number of reply signals which are received during said time interval in successive ones of said cycles exceed by a predetermined number the number of reply signals which are missing within said interval.

6. A digital computer system for calculating the range between two stations which are in radio communication with each other and which cyclically transmit interrogation and reply signals, said system comprising

a. calculation means for producing a digital output having a value corresponding to the elapsed time between the time of occurrence of an interrogation signal transmitted from a first of said stations to the second of said stations and the time of reception of a reply signal transmitted from said second station to said first station during each of said cycles and for storing said output during the next cycle, and

b. control means responsive to said stored output, said reply signals and said interrogation signals for supplying information to said calculation means respecting the times of occurrence of said interrogation signals and the expected and actual times of occurrence of said reply signals, said control means includinglogic means coupled to said stored digital output for providing a signal corresponding to a missing reply signal at said expected time of occurrence, and

means for supplying to said calculating means said information respecting the time of occcurrence of said missing reply signal when said reply signal does not actually occur.

7. A system for computing the range between two stations which are in radio communication with each other, one of which stations repetitively transmits an interrogation signal and reviews a reply signal, said interrogation and reply signals being successively transmitted or received upon successive dwells while said stations are in radio communication, said system comprising

a. a calculation unit for calculating said ranging on the basis of the time interval between transmission and reception of said interrogation and reply signals during each of said dwells,

b. a first control unit operated by said calculation unit for producing a synthethic reply signal at the expected time of occurrence of a reply signal on each of said dwells, and

c. an input control unit operated by said reply signal, said synthetic reply signal and said interrogation signal for controlling said calculation unit to vary said range calculation on the basis of the average of the difference between the time of occurrence of said synthetic reply signal and said reply signal over a predetermined number of dwells.

8. A system for computing the range between two stations which are in radio communication with each other, one of which stations repetitively transmits an interrogation signal and reviews a reply signal, said interrogation and reply signals being successively transmitted or received upon successive dwells while said stations are in radio communication, said system comprising

a. a calculation unit for calculating said ranging on the basis of the time interval between transmission and reception of said interrogation and reply signals during each of said dwells,

b. a first control unit operated by said calculation unit for producing a synthetic reply signal at the expected time of occurrence of a reply signal on each of said dwells, and

c. an acquistion control unit responsive to said synthetic reply signals and to said reply signals for enabling readout of said calculation by said calculation unit when said reply signals exceed said synthetic reply signals by a predetermined number.

9. A system for computing the range between two stations which are in radio communication with each other, one of which stations repetitively transmits an interrogation pulse and reviews a reply pulse, said interrogation and reply pulses being successively transmitted or received upon successive dwells while said stations are in radio communication, said system comprising

a. a calculation unit comprisinga source of clock pulses,

first and second counters responsive to said clock signals which respectively count said signals incrementally and decrementally,gates coupling said counters for transferring the count registered in said first counter to said second counter when enabled, and

b. a missing reply signal control unit for providing a synthetic reply pulse when said second counter is decremented to a zero count, and

c. an input control unit responsive to said reply pulse, said interrogation pulse and said synthetic reply pulse for controlling the interval of time during which said clock pulses are transferred to said counters and for enabling said gates at the end of each of said dwells.

10. The invention as set forth in claim 9, wherein said calculation unit includes means for reading out the count registered in said first counter when enabled and also including an acquisition control unit comprising a counter having means for incrementing and decrementing the count registered therein, means for applying said reply pulses to said counter for incrementing said count registered therein in response to said reply pulses, means for decrementing said count registered therein in response to said synthetic reply pulses, and means responsive to the storage in said counter of a predetermined number of counts for enabling said readout means.

11. The invention as set forth in claim 10, including a range gate control unit for transmitting said reply pulses to said input control unit when enabled means operated by said second counter for enabling said range gate control unit when said second counter is decremented to register a predetermined number of counts, means included in said range gate control unit for inhibiting said control unit in response to said synthetic reply pulse, and means for preventing inhibition of said range gate control unit when said counter in said acquisition control unit has a zero count stored therein.

12. The invention as set forth in claim 10, including a range gate control unit for transmitting said reply pulses to said input control unit when enabled, means operated by said second counter for providing a plurality of output pulses each respectively when said down counter is decremented to a different number of counts, a synthetic reply pulse counter responsive to said synthethic reply pulses for counting said synthetic reply pulses, means coupled to said synthetic reply pulse counter for transmitting different ones of said plurality reply pulses to said range gate control unit for enabling said reply pulse control unit when different counts are stored in said synthetic reply pulse counter, means responsive to a reply pulse transmitted by said range gate control unit, for resetting said synthetic reply pulse counter, and means in said reply pulse control unit responsive to a synthetic reply pulse for inhibiting said reply pulse control unit.

13. The invention as set forth in claim 9, wherein said calculation unit includes a storage register, and wherein said calculation unit also includes transfer gates for reading out the count stored in said first counter into said storage register at the end of each dwell, a lost signal counter coupled to said first counter for resetting said storage register when said first counter has reached a predetermined number of counts and a plurality of successive dwells.

14. A system for calculating the range between craft which are in radio communication with each other, one of which repetitively transmits interrogation pulses and the other of which transmits reply pulses in response thereto, said reply pulses and interrogation pulses occurring in successive dwells, said computer comprising

a. a calculation unit includingan up counter which counts incrementally pulses applied thereto,

a down counter which counts decrementally pulses applied thereto,gate means for transferring the count registered in said up counter to said down counter,

b. a source of clock pulses repetitive at intervals corresponding to increments of said range,

c. means coupled to said down counter for producing a filler pulse when said counter is decremented to a certain count,

d. an input control unit includinggate means for transmitting said clock pulses to both said up counter and down counter when enabled,

time error detector means responsive to said filler pulses and said reply pulses for providing an output corresponding to the sense and magnitude of the difference of the time of occurrence of said reply pulses and said filler pulses,means for enabling said gate means upon occurrence of each of said interrogation pulses and inhibiting said gate means upon occurrence of each of said filler pulses, andvariable delay means coupled at least to said enabling means for said up counter gate means controlled by said output for controlling the times of operation of said enabling means,

e. means responsive to said filler pulses for enabling said calculation unit gate means upon occurrence thereof.

15. The invention as set for the in claim 14, wherein said input control unit includes integrating means responsive to said output for integrating said output over a predetermined number of dwells.