System for transmitting digital signals with FM signals

• US 20020187759A1
• Filed: 06/12/2001
• Published: 12/12/2002
• Est. Priority Date: 06/12/2001
• Status: Active Grant

• Current Assignee: SPX Corporation
• Original Assignee: SPX Corporation
• Inventors: Stenberg, James T.
• Granted Patent: US 6,934,514 B2
• Time in Patent Office: Days
• US Class Current: 455/117
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes
• CPC Class Codes: H04H 20/30 by a single channel

Abstract

A system for transmitting digital signals in the same band and on the same channel with FM signals is disclosed. The design of the system according to the present invention includes a coupler, which may be a +3 dB hybrid quadrature coupler, and circularly polarized antenna. The +3 dB hybrid quadrature coupler maintains isolation between the FM signals and the digital signals. The circularly polarized antenna receives the FM signals and the digital signals, and transmits the signals after they have each been separately received at the circularly polarized antenna.

Claims

1. An apparatus for transmitting FM signals and digital signals, comprising:

a +3 dB hybrid quadrature coupler having a first input and a second input;

a first transmission line coupled to the first input;

a second transmission line coupled to the second input; and

a circularly polarized antenna coupled to the first transmission line and the second transmission line.

2. The apparatus according to claim 1, further comprising:

a first transmitter, wherein the first transmitter is coupled to the first input.

3. The apparatus according to claim 2, further comprising:

a second transmitter, wherein the second transmitter is coupled to the second input.

4. The apparatus according to claim 3, wherein the first transmitter transmits at least one of a digital signal and an FM signal.

5. The apparatus according to claim 4, wherein the second transmitter transmits at least one of a digital signal and an FM signal that is different from the at least one of a digital and an FM signal transmitted by the first transmitter.

6. The apparatus of claim 1, wherein the antenna has a first dipole arm connected to the first transmission line.

7. The apparatus of claim 6, wherein the antenna has a second dipole arm connected to the second transmission line.

8. The apparatus according to claim 5, wherein the first transmitters transmits the at least one of a digital signal and an FM signal as at least one of right-hand circularly polarized and left-hand circularly polarized.

9. The apparatus according to claim 8, wherein the second transmitter transmits the at least one of a digital signal and an FM signal that is different from the at least one of a digital and an FM signal transmitted by the first transmitter as polarized opposite to a signal transmitted by the first transmitter.

10. A system for transmitting digital signals with FM signals, comprising:

a coupler means for splitting a digital signal into a first digital signal part and a second digital signal part, and for splitting an FM signal into a first FM signal part and a second FM signal part;

a first transmission line means and a second transmission line means coupled to the coupler means for transmitting the first digital signal part, the second digital signal part, the first FM signal part, and the second FM signal part; and

antenna means for receiving the first digital signal part, the second digital signal part, the first FM signal part, and the second FM signal part from the first transmission line means and the second transmission line means.

11. The system according to claim 10, further comprising:

a transmission means for transmitting the FM signal to the coupler means.

12. The system according to claim 10, further comprising:

a transmission means for transmitting the digital signal to the coupler means.

13. The system according to claim 10, wherein the first transmission line transmits a pair of signals including at least one of the digital signal first part and digital signal second part, and at least one of the FM signal first part and FM signal second part such that there is a phase difference of 90 degrees between the pair of signals for simultaneously transmitting a pair of signals, while maintaining isolation between the pair of signals.

14. The system of claim 10, wherein the first digital signal part and the second digital signal part are equal in amplitude.

15. The system of claim 10, wherein the first FM signal part and the second FM signal part are equal in amplitude.

17. The method according to claim 16, further comprising:

transmitting the first pair of signals using the first transmission line to a first dipole arm of a circularly polarized antenna.

18. The method according to claim 16, further comprising:

transmitting the second pair of signals using the second transmission line to a second dipole arm of the circularly polarized antenna.

19. The method according to claim 16, wherein the first digital signal part and the second digital signal part are equal in amplitude.

20. The method according to claim 16, wherein the first FM signal part and the second FM signal part are equal in amplitude.

16. A method for transmitting digital signals and FM signals, comprising:

splitting a digital signal into a first digital part and a second digital part, such that there is a 90 degrees phase difference between each part using a hybrid quadrature coupler;

splitting an FM signal into a first FM part and a second FM part, such that there is a 90 degrees phase difference between each part using a +3 dB hybrid quadrature coupler; and

transmitting a first pair of signals and a second pair of signals using a first transmission line and a second transmission line, wherein each pair of signals includes at least one of the digital signal first part and the digital signal second part, and including at least one of the FM signal first part and the FM signal second part, wherein there is a 90 degrees phase difference between the pair of signals.