RADIO RECEIVING APPARATUS FOR LOCATING A PLURALITY OF TARGET TRANSMITTERS

• US 3,766,560 A
• Filed: 02/11/1972
• Issued: 10/16/1973
• Est. Priority Date: 02/11/1972
• Status: Expired due to Term

• Current Assignee: Alvin E. Culbertson, David E. Thomas, Donald E. Drake, Jack L. Monroe, Kenneth F. Bornhorst
• Original Assignee: Alvin E. Culbertson, David E. Thomas, Donald E. Drake, Jack L. Monroe, Kenneth F. Bornhorst
• Inventors: Culbertson, Alvin E., Bornhorst, Kenneth F., Monroe, Jack L., Thomas, David E., Drake, Donald E.
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/225,519
• Time in Patent Office: 613 Days
• Field of Search: 343/118
• US Class Current: 342/428
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence

Abstract

Apparatus combining a UHF radio receiver with digital circuitry for processing and displaying signals indicating the location of one or more remotely located target radio transmitters, which apparatus includes a signal storing bearing indicator device operated in synchronism with a continuously rotating receiver antenna, and which apparatus also includes a refined AGC system and a target verifying correlation system for improving reliability of the information presented to an operator.

Claims

1. Radio receiver and display apparatus for indicating signal receptions from and relative bearing location of a plurality of remotely located radio frequency signal emitting transmitters and for providing audio signal reception from said remotely located transmitters, said apparatus comprising:

substantially unidirectional antenna array having a continuously rotating field pattern capable of selectively receiving radio frequency signals in sequence from multiple directions of azimuth around the locus of said apparatus and capable of converting said received signals into antenna electrical signals;

selectively tunable superhetrodyne circuitry means including plural radio frequency amplifier stages coupled with first signal processing means for converting said antenna electrical signals into a radio frequency carrier strength indicating signal and also coupled with second signal processing means for converting said antenna electrical signals into a detected modulation envelope signal;

audio signal processing circuit means connected with said second signal processing means in said superhetrodyne circuitry means for generating from said detected modulation envelope signal an audible audio signal indicative of any audio frequency modulation imposed on the signal currently received from one of said remotely located transmitters;

gated automatic gain control circuit means connected with said selectively tunable superhetrodyne circuitry means for generating and storing during preliminary revolutions of said unidirectional antenna array field pattern a D.C. gain controlling signal correlated with the magnitude of said carrier strength indicating signal existing during reception of selected radio frequency signals by said apparatus and for applying said D.C. gain controlling signal to at least one of said plural radio frequency amplifier stages as a gain decreasing signal;

signal peak detecting means connected with said first signal processing means in said tunable superhetrodyne circuitry means for generating, during antenna field pattern revolutions other than said preliminary revolutions, binary pulse signals each timed in substantial coincidence with a peak value of said radio frequency carrier strength indicating signal, whereby each of said binary pulse signals identifies a maximum degree of alignment of said unidirectional antenna array field pattern with one of said remotely located transmitters;

signal storage and display means connected with said signal peak detecting means for accumulating said binary pulse signals during at least one revolution of said antenna array field pattern and for displaying to an operator a spatially oriented visual pattern representing said accumulated pulse signals.

2. Radio receiver and display apparatus as in claim 1 which also includes:

electrically controllable tuning means for changing the operating frequency of said selectively tunable superhetrodyne circuitry means and electrical control circuit means for coordinating revolutions of said substantially unidirectional antenna field pattern with changes of operating frequency of said selectively tunable superhetrodyne circuitry means and for identifying in said gated automatic gain control means said preliminary revolutions of said unidirectional antenna array field pattern.

3. Radio receiver and display apparatus as in claim 1 wherein said signal storage and display means also includes signal correlating means connected with said signal storage and display means and with said signal peak detecting means for presenting stored signals from said signal storage and display means in time coincidence with subsequent antenna field pattern revolution real-time binary pulse signals from said signal peak detecting means and for re-storing a correlated signal for each time a stored signal and a subsequent antenna fiEld pattern revolution real time binary pulse signal occur in time coincidence.

4. Radio receiver and display apparatus as in claim 1 wherein said signal storage and display means includes digital memory means limited to storing the binary pulse signals generated during one revolution of said unidirectional antenna array field pattern.

5. Radio receiver and display apparatus as in claim 1 wherein said apparatus includes the combination of a substantially unidirectional antenna array having a directivity pattern incorporating one major frontal response lobe and at least one weaker minor response lobe angularly displaced from said major frontal lobe along with adjustable threshold circuitry means in said signal peak detecting means for amplitude distinguishing signals received via said major frontal lobe from signals received via said angularly displaced minor lobe.

6. Radio receiver and display apparatus as in claim 1 wherein said audio signal processing circuit means also includes fast automatic gain control circuit means for at least partially smoothing amplitude variations imposed upon the audio frequency component of signal received through said continuously rotating substantially unidirectional antenna array field pattern.

7. Radio receiver and display apparatus as in claim 1 wherein said gated automatic gain control circuit means also includes electrical circuit means for limiting the rate of increase of said generated and stored D.C. gain controlling signal during at least an early portion of said preliminary revolutions of said continuously rotating substantially unidirectional antenna array, field pattern, whereby signal received from a nearby transmitter is precluded from generating an excessively large overshoot in said D.C. gain controlling signal during said preliminary revolutions of said unidirectional antenna array field pattern while said receiver apparatus is operating in a high gain condition.

8. Radio receiver and display apparatus as in claim 1 wherein said first signal processing means in said selectively tunable superhetrodyne circuitry means also includes low pass electrical wave filter means for rejecting frequency components of said carrier strength indicating signal that are substantially higher in frequency than components generated when said continuously rotating substantially unidirectional antenna array field pattern sucessively aligns with two radio frequency signal emitting transmitters angularly separated by the minimum resolution capability of said continuously rotating substantially unidirectional antenna array field pattern.

9. Radio receiver and display apparatus as in claim 8 wherein said electrical wave filter means includes means for attenuating frequency components generated by multibladed aircraft propelling device interference with the signal path between said remotely located radio frequency signal emitting transmitter and said continuously rotating substantially unidirectional antenna array.

10. Radio receiver and display apparatus as in claim 1 wherein said continuously rotating substantially unidirectional antenna array and said selectively tunable superhetrodyne circuitry means are selected to operate in the ultra high frequency band of frequencies;

and said gated automatic gain control circuit means includes means for generating during the first two of four consecutive revolutions of said antenna array field pattern a D.C. gain controlling signal amplitude correlated with the peak magnitude of said carrier strength indicating signal while receiving radio frequency signals on one frequency.

11. Radio receiver and display apparatus as in claim 1 wherein said substantially unidirectional antenna array has a directivity pattern incorporating a major frontal response lobe having a beam width near 60* when measured at the 3db down points.

12. Radio receiver and display apparatus as in claim 1 wherein said apparatus includes means for connecting said gated automatic gain control means with a sufficient number of said radio frequency amplifier stages to limit the signal variation at said signal peak detecting means of said apparatus to a value near 6db during an input signal variation of 100db.

13. A method for providing an aircraft with both homing guidance information and audio frequency communication information from a remotely located source of radio frequency energy so that said aircraft may be guided thereto comprising the steps of:

sequentially scanning with a directive antenna array the space surrounding said aircraft for signals originating at said remotely located source of radio frequency energy;

thereby converting said signals into antenna electrical signals having a modulation component imposed by the scanning of said directive antenna array;

extracting from said antenna electrical signal an analog electrical signal corresponding to the antenna modulation component of said antenna electrical signals, said extracting involving amplifying and detecting said antenna electrical signals in radio receiver apparatus;

generating from said analog electrical signal a digital pulse signal timed substantially at the peak of said analog electrical signal, said act of generating including the acts of differentiating said analog electrical signal and initiating said digital pulse signal at the zero crossing point of the differentiated signal;

displaying against a background representing the incrementally divided scanning field of said directive antenna and the vector heading of said aircraft, a visual pattern representing time elapsed between antenna scan start and the occurrence of said digital pulse, whereby the operator of said aircraft is presented with a visual indication of the relative bearing between his own course of travel and the course of travel leading to said source of radio frequency energy;

whereby said analog electrical signal provides both homing guidance information and audio frequency communication information from said remotely located source of radio frequency energy by way of signal from said scanning directive antenna having a substantial average value incorporating the maximum response of said directive antenna array in lieu of the nulled or minimum response of said directive antenna array.