Combined low frequency receive and high frequency transceive antenna system and method

• US 5,170,493 A
• Filed: 07/25/1988
• Issued: 12/08/1992
• Est. Priority Date: 07/25/1988
• Status: Expired due to Fees

• Current Assignee: UPS Aviation Technologies, Inc. (Garmin Limited)
• Original Assignee: II Morrow, Inc.
• Inventors: Roth, Stephen A.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): FAILE, ANDREW I
• Application Number:
  US07/223,911
• Time in Patent Office: 1,597 Days
• Field of Search: 455/78, 455/80, 455/82-83, 455/142-143, 455/282, 455/291, 333/126, 333/129, 333/132, 333/134, 343/858, 343/861, 342/57-58, 342/388, 342/389, 342/55
• US Class Current: 455/82
• CPC Class Codes: H01Q 5/50 Feeding or matching arrangements for broad-band or multi-band operation
• CPC Class Codes: H04B 1/18 Input circuits, e.g. for coupling to an antenna or a transmission line coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H
• CPC Class Codes: H04B 1/48 in circuits for connecting transmitter and receiver to a common transmission path, e.g. by energy of transmitter H04B1/46 takes precedence

Abstract

A dual function antenna system and method. A system is provided for using a single antenna for both the reception of low frequency navigational signals, such as LORAN-C, and high frequency communications signals in the VHF region. The antenna is at a remote location from a low frequency receiver and a high frequency transceiver. Both the low frequency and the high frequency signals are coupled to the receiver and transceiver, respectively, over the same transmission line at one end thereof. A preamplifier is provided at the location of the antenna to increase the strength of the low frequency signal applied to the transmission line. A high pass filter is provided to couple the antenna and the transmission line and prevent feedback from the output of the preamplifier from reaching its input. The other end of the transmission line is coupled to the high frequency transceiver by a high pass filter, and to the low frequency receiver by a low pass filter. The preamplifier is supplied with DC power over the transmission line, and includes a current regulator so that the preamplifier may be used with a wide range of supply voltages.

Claims

1. A system for coupling a radio antenna to a high frequency transmitter and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to transmit high frequency signals and receive low frequency signals, comprising:

(a) preamplifier means for connecting said antenna to said first transmission line, amplifying low frequency signals present at said antenna, and applying said low frequency signals, as amplified, to said first transmission line, said preamplifier means having an input port for receiving signals to be amplified and an output port for outputting amplified signals; and

(b) high frequency path means for coupling high frequency signals present on said first transmission line to said antenna without coupling to said antenna said low frequency signals applied to said first transmission line by said preamplifier so as to prevent feedback of low frequency signals output at said output port of said preamplifier to said input port thereof.

2. The system of claim 1, wherein said preamplifier means has an input port for receiving signals to be amplified and an output port for outputting amplified signals, said system further comprising low frequency input network means, disposed between said antenna and said input port of said preamplifier means, for substantially matching the impedance of said antenna to the impedance of said preamplifier means at said input port at the frequency of said low frequency signals.

3. The system of claim 2, wherein said preamplifier means comprises amplifier means, disposed between said input port and said output port, for amplifying signals applied to said input port, and current regulator means for supplying substantially constant current DC power to said amplifier means.

4. The system of claim 3, wherein said preamplifier means further comprises means for receiving DC power for said amplifier means at said output port and applying said DC power to said amplifier means through said current regulator means.

5. The system of claim 2, wherein said low frequency input network means comprises band pass filter means for limiting the range of frequencies which can be coupled from said antenna to said input port of said preamplifier means to a predetermined range of frequencies corresponding to said low frequency signals.

6. The system of claim 5, wherein said low frequency input network means comprises a filter whose elements include the distributed reactance of said antenna.

7. The system of claim 5, wherein said low frequency signals are LORAN-C navigation signals and said low frequency input network means has a band pass characteristic of approximately 100 kHz±

25 kHz.

8. The system of claim 1 further comprising low pass filter means, connected to said first transmission line, for coupling said low frequency signals, as amplified, from said first transmission line to a low frequency receiver, and high pass filter means, connected to said first transmission line, for coupling said high frequency signals from said transmitter to said first transmission line.

9. A method for coupling a radio antenna to a high frequency transmitter and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to transmit high frequency signals and receive low frequency signals, comprising:

(a) amplifying low frequency signals present at said antenna and applying said low frequency signals, as amplified, to said first transmission line; and

(b) coupling high frequency signals present on said first transmission line to said antenna without coupling to said antenna said amplified low frequency signals applied to said first transmission line thereby preventing said amplified low frequency signals from producing feedback and concommitant instability.

10. The method of claim 9, further comprising coupling high frequency signals present on said first transmission line to said antenna and vice versa without substantially attenuating low frequency signals present on said antenna.

11. The method of claim 9 wherein said amplifying step includes matching the impedance of said antenna to the impedance of said first transmission line at the frequency of said low frequency signals.

12. The method of claim 9, further comprising employing an amplifier in said amplifying step and matching the impedance of said antenna to the input impedance of said amplifier at the frequency of said low frequency signals.

13. The method of claim 9, further comprising coupling high frequency signals from said transmitter to said first transmission line without substantially attenuating low frequency signals present on said first transmission line.

14. The method of claim 9, further comprising coupling low frequency signals present on said first transmission line to said receiver, without coupling high frequency signals present on said transmission line to said receiver.

15. A system for coupling a radio antenna to a high frequency transmitter and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to transmit high frequency signals and receive low frequency signals, comprising:

(a) preamplifier means for connecting said antenna to said first transmission line, amplifying low frequency signals present at said antenna, and applying said low frequency signals, as amplified, to said first transmission line, said preamplifier means having an input port for receiving signals to be amplified and an output port for outputting amplified signals;

(b) low frequency input network means, disposed between said antenna and said input port of said preamplifier means, for substantially matching the impedance of said antenna to the impedance of said preamplifier means at said input port at the frequency of said low frequency signals;

(c) low pass filter means, disposed between said output port of said preamplifier means and said first transmission line, for permitting said low frequency signals, as amplified, to be passed from said preamplifier means to said first transmission line and DC power to be passed from said first transmission line to said preamplifier means, without allowing high frequency signals present on said first transmission line to be passed from said first transmission line to said output port of said preamplifier means; and

(d) high frequency path means for coupling high frequency signals present on said first transmission line to said antenna without coupling to said antenna said low frequency signals applied to said first transmission line.

16. A system for coupling a radio antenna to a high frequency transmitter and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to transmit high frequency signals and receive low frequency signals, comprising:

(a) preamplifier means for connecting said antenna to said first transmission line, amplifying low frequency signals present at said antenna, and applying said low frequency signals, as amplified, to said first transmission line; and

(b) high frequency path means for coupling high frequency signals present on said first transmission line to said antenna without coupling to said antenna said low frequency signals applied to said first transmission line, said high frequency path means comprising a band pass filter connected between said antenna and said first transmission line, for limiting the range of frequencies which can be coupled between said antenna and said first transmission line via said high frequency path to a predetermined range of high frequency signals.

17. The system of claim 16, wherein said band pass filter is coupled to said antenna through a first series capacitor.

18. The system of claim 17, wherein said first series capacitor has a capacitance of substantially about 3.9 picofarads or less.

19. The system of claim 16, wherein said band pass filter is coupled to said first transmission line through a second series capacitor.

20. The system of claim 16, wherein said high frequency signals are VHF communication signals and said band pass filter permits signals of approximately 150 MHz±

2.5 MHz to pass therethrough with a good impedance match to said antenna and to said first transmission line.

21. A system for coupling a radio antenna to a high frequency transmitter and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to transmit high frequency signals and receive low frequency signals, comprising:

(a) preamplifier means for connecting said antenna to said first transmission line, amplifying low frequency signals present at said antenna, and applying said low frequency signals, as amplified, to said first transmission line, said preamplifier means including means for receiving DC power from said first transmission line;

(b) high frequency path means for coupling high frequency signals present on said first transmission line to said antenna without coupling to said antenna said low frequency signals applied to said first transmission line;

(c) low pass filter means, connected to said first transmission line, for coupling said low frequency signals, as amplified, from said first transmission line to a low frequency receiver, said low pass filter means including means for passing DC power for said preamplifier means to said first transmission line; and

(d) high pass filter means, connected to said first transmission line, for coupling said high frequency signals from said transmitter to said first transmission line.

22. A system for coupling a radio antenna to a high frequency transmitter and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to transmit high frequency signals and receive low frequency signals, comprising:

(a) preamplifier means for connecting said antenna to said first transmission line, amplifying low frequency signals present at said antenna, and applying said low frequency signals, as amplified, to said first transmission line;

(b) high frequency path means for coupling high frequency signals present on said first transmission line to said antenna without coupling to said antenna said low frequency signals applied to said first transmission line; and

(c) a second, relatively short transmission line electrically disposed between said antenna and said high frequency path means, said high frequency path means comprising a network for matching the impedance of said second transmission line to the impedance of said first transmission line at the frequency of said high frequency signals.

23. The system of claim 22, wherein said preamplifier means has an input port for receiving signals to be amplified and an output port for outputting amplified signals, said system further comprising low frequency input network means, disposed between said second transmission line and said input port of said preamplifier means, for substantially matching the impedance of said antenna to the impedance of said preamplifier means at said input port at the frequency of said low frequency signals, said low frequency input network means having an input choke means for substantially blocking said high frequency signals.

24. A method for coupling a radio antenna to a high frequency transmitter and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to transmit high frequency signals and receive low frequency signals, comprising:

(a) employing an amplifier to amplify low frequency signals present at said antenna and applying said low frequency signals, as amplified, to said first transmission line;

(b) coupling high frequency signals present on said first transmission line to said antenna without coupling to said antenna said low frequency signals applied to said first transmission line; and

(c) filtering signals present at said antenna before applying them to said amplifier so as to permit low frequency signals present at said antenna to pass to the input of said amplifier while preventing high frequency signal present at said antenna from passing to the input of said amplifier.

25. The method of claim 24, wherein said filtering includes substantially preventing frequencies above and below a predetermined range of frequencies from passing to the input of said amplifier.

26. A method for coupling a radio antenna to a high frequency transmitter and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to transmit high frequency signals and receive low frequency signals, comprising:

(a) employing an amplifier to amplify low frequency signals present at said antenna and applying said low frequency signals, as amplifier, to said first transmission line;

(b) coupling high frequency signals present on said first transmission line to said antenna without coupling to said antenna said low frequency signals applied to said first transmission line; and

(c) filtering the output of said amplifier so as to permit said low frequency signals, as amplified, to be coupled to said first transmission line but to prohibit high frequency signals present on said first transmission line from being applied to said amplifier.

27. A method for coupling a radio antenna to a high frequency transmitter and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to transmit high frequency signals and receive low frequency signals, comprising:

(a) employing an amplifier to amplify low frequency signals present at said antenna and applying said low frequency signals, as amplified to said first transmission line;

(b) coupling high frequency signals present on said first transmission line to said antenna without coupling to said antenna said low frequency signals applied to said first transmission line; and

(c) regulating the current used by said amplifier so a to permit said amplifier to operate over a wide range of supply voltages.

28. The method of claim 27, wherein current is supplied to said amplifier over said first transmission line.

29. A method for coupling a radio antenna to a high frequency transmitter and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to transmit high frequency signals and receive low frequency signals, comprising:

(a) amplifying low frequency signals present at said antenna and applying said low frequency signals, as amplifier, to said first transmission line;

(b) coupling high frequency signals present on said first transmission line to said antenna without coupling to said antenna said low frequency signals applied to said first transmission line;

(c) connecting a relatively short second transmission line to said antenna; and

(d) matching the impedance of said second transmission line to the impedance of said first transmission line at the frequency of said low frequency signals.

30. A dual-purpose antenna system, comprising:

(a) a radio antenna having relatively low impedance at high frequencies and relatively high impedance at low frequencies;

(b) first coupling means for coupling said antenna to a first transmission line at said low frequencies, said first coupling means including amplifier means for amplifying signals at said low frequencies and means for receiving DC power from said first transmission line and applying it to said amplifier means;

(c) second coupling means for coupling said antenna to said first transmission line at said high frequencies;

(d) third coupling means for coupling said first transmission line to a low frequency radio receiver at said low frequencies, said third coupling means including means for passing said DC power to said transmission line; and

(e) fourth coupling means for coupling said first transmission line to a high frequency radio transmitter at said high frequencies.

31. A dual-purpose antenna system, comprising:

(a) a radio antenna having relatively low impedance at high frequencies and relatively high impedance at low frequencies;

(b) first coupling means for coupling said antenna to a first transmission line at said low frequencies;

(c) second coupling means for coupling said antenna to said first transmission line at said high frequencies;

(d) third coupling means for coupling said first transmission line to a low frequency radio receiver at said low frequencies;

(e) fourth coupling means for coupling said first transmission line to a high frequency transmitter; and

(f) second transmission line disposed between said antenna and said first and second coupling means.

32. A system for coupling a radio antenna to a high frequency receiver and low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to receive high frequency signals and receive low frequency signals, comprising:

(a) preamplifier means for connecting said antenna to said first transmission line, amplifying low frequency signals present at said antenna, and applying said low frequency signals, as amplified, to said first transmission line, said preamplifier means having an input port for receiving signals to be amplified and an output port for outputting amplified signals; and

(b) high frequency path means for coupling high frequency signals present at said antenna to said first transmission line without coupling to said antenna said low frequency signals applied to said first transmission line by said preamplifier so as to prevent feedback of low frequency signals output at said output port of said preamplifier to said input port thereof.

33. A method for coupling a radio antenna to a high frequency receiver and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to receive high frequency signals and receive low frequency signals, comprising:

(a) amplifying low frequency signals present at said antenna and applying said low frequency signals, as amplified, to said first transmission line; and

(b) coupling high frequency signals present at said antenna to said first transmission line without coupling to said antenna said amplified low frequency signals applied to said first transmission line, thereby preventing said amplified low frequency signals from producing feedback and concomitant instability.

34. A system for coupling a radio antenna to a high frequency receiver and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to receive high frequency signals and receive low frequency signals, comprising:

(a) preamplifier means for connecting said antenna to said first transmission line, amplifying low frequency signals present at said antenna, and applying said low frequency signals, as amplified, to said first transmission line; and

(b) high frequency path means for coupling high frequency signals present at said antenna to said first transmission line to said antenna without coupling to said antenna said low frequency signals applied to said first transmission line, said high frequency path means comprising a band pass filter connected between said antenna and said first transmission line, for limiting the range of frequencies which can be coupled between said antenna and said first transmission line via said high frequency path to a predetermined range of high frequency signals.

35. The system of claim 34, wherein said band pass filter is coupled to said antenna through a first series capacitor.

36. The system of claim 35, wherein said first series capacitor has a capacitance of substantially about 3.9 picofarads or less.

37. The system of claim 34, wherein said band pass filter is coupled to said first transmission line through a second series capacitor.

38. The system of claim 34, wherein said high frequency signals are VHF communication signals and said band pass filter permits signals of approximately 150 MHz±

2.5 MHz to pass therethrough with a good impedance match to said antenna and to said first transmission line.

39. A system for coupling a radio antenna to a high frequency receiver and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to receive high frequency signals and receive low frequency signals, comprising:

(a) preamplifier means for connecting said antenna to said first transmission line, amplifying low frequency signals present at said antenna, and applying said low frequency signals, as amplified, to said first transmission line;

(b) high frequency path means for coupling high frequency signals present at said antenna to said first transmission line without coupling to said antenna said low frequency signals applied to said first transmission line; and

(c) a second, relatively short transmission line electrically disposed between said antenna and said high frequency path means, said high frequency path means comprising a network for matching the impedance of said second transmission line to the impedance of said first transmission line at the frequency of said high frequency signals.

40. The system of claim 39, wherein said preamplifier means has an input port for receiving signals to be amplified and an output port for outputting amplified signals, said system further comprising low frequency input network means, disposed between said second transmission line and said input port of said preamplifier means, for substantially matching the impedance of said antenna to the impedance of said preamplifier means at said input port at the frequency of said low frequency signals, said low frequency input network means having an input choke means for substantially blocking said high frequency signals.

41. A method for coupling a radio antenna to a high frequency receiver and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to receive high frequency signals and to receive low frequency signals, comprising:

(a) employing an amplifier to amplify low frequency signals present at said antenna and applying said low frequency signals, as amplified, to said first transmission line;

(b) coupling high frequency signals present at said antenna to said first transmission line without coupling to said antenna said low frequency signals applied to said first transmission line; and

(c) filtering signals present at said antenna before applying them to said amplifier so as to permit low frequency signals present at said antenna to pass to the input of said amplifier while preventing high frequency signals present at said antenna from passing to the input of said amplifier.

42. The method of claim 41, wherein said filtering includes substantially preventing frequencies above and below a predetermined range of frequencies from passing to the input of said amplifier.

43. A method for coupling a radio antenna to a high frequency receiver and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to receive high frequency signals and receive low frequency signals, comprising:

(a) employing an amplifier to amplify low frequency signals present at said antenna and applying said low frequency signals, as amplified, to said first transmission line;

(b) coupling high frequency signals present at said antenna to said first transmission line without coupling to said antenna said low frequency signals applied to said first transmission line; and

(c) regulating the current used by said amplifier so as to permit said amplifier to operate over a wide range of supply voltages.

44. The method of claim 43, wherein current is supplied to said amplifier over said first transmission line.

45. A method for coupling a radio antenna to a high frequency receiver and a low frequency receiver over the same first transmission line so that said antenna may be simultaneously used to receive high frequency signals and to receive low frequency signals, comprising:

(a) amplifying low frequency signals present at said antenna and applying said low frequency signals, as amplified, to said first transmission line;

(b) coupling high frequency signals present at said antenna to said first transmission line without coupling to said antenna said low frequency signals applied to said first transmission line;

(c) connecting a relatively short second transmission line to said antenna;

(d) matching the impedance of said second transmission line to the impedance of said first transmission line at the frequency of said low frequency signals.