Isolating signal divider/combiner and method of combining signals of first and second frequencies

• US 6,515,557 B1
• Filed: 08/13/2001
• Issued: 02/04/2003
• Est. Priority Date: 08/13/2001
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Wangsvick, Chad M., Salvail, Gary M., Kusbel, Mark E.
• Primary Examiner(s): Tokar, Michael
• Assistant Examiner(s): NGUYEN, LINH V
• Application Number:
  US09/929,189
• Publication Number:
  US 20030030508A1
• Time in Patent Office: 540 Days
• Field of Search: 333/126, 333/128, 333/129, 333/132, 333/134, 333/136, 343/858, 343/700, 343/853, 343/860
• US Class Current: 333/126
• CPC Class Codes: H01P 5/12 Coupling devices having more than two ports H01P5/04 takes precedence

Abstract

A signal divider/combiner (11) and method combines first and second frequency signals received by microstrip patch antennas (58, 48). A first transmission line stub (28) blocks the second frequency signals on the first signal receiving path, and a second transmission line stub (20) blocks the first frequency signals on the second signal receiving path providing increased signal levels at a receiver input (10). In one embodiment, the transmission line stubs are open-circuit stubs and are positioned a quarter-wavelength from a combining junction (12) formed from stripline transmission lines (14, 32, 50). The transmission line stubs (28, 20) also reduce radiation of the first frequency signal by the second antenna as well as radiation of the second frequency signal by the first antenna. In one embodiment, the first and second frequency signals are the L1 and L2 signals provided by the Global Positioning System.

Claims

1. A signal divider/combiner for dividing/combining signals of first and second similar narrowband frequencies comprising:

first, second and third transmission lines meeting at a junction, the first, second and third transmission lines having substantially the same impedance as each other, the first and second transmission lines having substantially the same impedance throughout their length;

a first transmission line stub section coupled to the first transmission line to substantially block signals of the second frequency along the first transmission line; and

a second transmission line stub section coupled to the second transmission line to substantially block signals of the first frequency along the second transmission line,

wherein the first transmission line stub section is a first open-circuit stub positioned a first distance from the junction, the first distance being substantially equal to an odd multiple number of quarter-wavelengths of the second frequency, and wherein the second transmission line stub section is a second open-circuit stub positioned a second distance from the junction, the second distance being substantially equal to an odd multiple number of quarter-wavelengths of the first frequency.

2. The signal divider/combiner as claimed in claim 1 wherein the similar frequencies are greater than 1000 MHz.

3. The signal divider/combiner as claimed in claim 2 wherein the first, second and third transmission lines and the first and second open-circuit stubs are either microstrip or stripline transmission lines, and wherein the first frequency is a Global Positioning System (GPS) L1 frequency, and the second frequency is a GPS L2 frequency.

4. The signal divider/combiner as claimed in claim 2:

wherein the first open-circuit stub has a length substantially equal to an odd multiple number of quarter-wavelengths of the second frequency, and

wherein the second open-circuit stub has a length substantially equal to an odd multiple number of quarter-wavelengths of the first frequency.

5. The signal divider/combiner as claimed in claim 1 wherein the signals of the first and second frequencies are provided respectively by first and second antennas, and wherein:

the first transmission line to provide signals of the first frequency from the first antenna;

the second transmission line to provide signals of the second frequency from the second antenna; and

the third transmission line to receive a combined signal of the first and second frequencies from the junction and to provide the combined signal to a receiver input.

6. The signal divider/combiner as claimed in claim 5 wherein an output of first antenna is substantially devoid of signals of the second frequency received by the second antenna, and an output of the second antenna is substantially devoid of signals of the first frequency received by a first antenna, thereby reducing radiation of signals of the first frequency by the second antenna, and radiation of signals of the second frequency by the first antenna.

22. The antenna receiving system as claimed in claim 1 wherein the first transmission line stub section is an open-circuit stub section having a length substantially equal to an odd multiple number of quarter-wavelengths of the second frequency, and

wherein the second transmission line stub section is an open-circuit stub section having a length substantially equal to an odd multiple number of quarter-wavelengths of the first frequency.

7. A signal combiner for combining signals of first and second similar frequencies comprising:

a first transmission line section to provide signals of the first frequency;

a second transmission line section to provide signals of the second frequency;

a third transmission line section to form a junction with the first and second transmission line sections, the junction to combine signals of the first and second frequencies, the first, second and third transmission line sections having substantially the same impedance as each other and throughout their length;

a first transmission line stub section coupled to the first transmission line section to substantially block signals of the second frequency; and

a second transmission line stub section coupled to the second transmission line section to substantially block signals of the first frequency,

wherein the first transmission line stub section is a first open-circuit stub positioned a first distance from the junction, the first distance being substantially equal to an odd multiple number of quarter-wavelengths of the second frequency, and wherein the second transmission line stub section is a second open-circuit stub positioned a second distance from the junction, the second distance being substantially equal to an odd multiple number of quarter-wavelengths of the first frequency.

8. The signal combiner as claimed in claim 7 further comprising:

a first antenna output to provide signals of the first frequency along the first transmission line section, the first transmission line stub section to block signals of the second frequency along the first transmission line section reducing signals of the second frequency at the first antenna output; and

a second antenna output to provide signals of the second frequency along the second transmission line section, the second transmission line stub section to block signals of the first frequency along the second transmission line section reducing signals of the first frequency at the second antenna output.

9. The signal combiner as claimed in claim 7 wherein the third transmission line section to provide combined signals of the first and second frequency from the junction to a receiver antenna input.

10. The signal combiner as claimed in claim 7 wherein the similar frequencies are greater than 1000 MHz.

11. The signal combiner as claimed in claim 7 wherein the first transmission line stub section has a length substantially equal to an odd multiple number of quarter-wavelengths of the second frequency, and

wherein the second transmission line stub section has a length substantially equal to an odd multiple number of quarter-wavelengths of the first frequency.

12. The signal combiner as claimed in claim 7 wherein the junction is a “

tee”

junction.

13. The signal combiner as claimed in claim 7 wherein the junction is a “

y”

junction.

14. The signal combiner as claimed in claim 7 wherein the first, second and third transmission line sections and the first and second transmission line stub sections are stripline transmission lines.

15. The signal combiner as claimed in claim 7 wherein the first, second and third transmission line sections and the first and second transmission line stub sections are microstrip transmission lines.

16. The signal combiner as claimed in claim 7 wherein the first frequency is a Global Positioning System (GPS) L1 frequency, and the second frequency is a GPS L2 frequency.

17. An antenna receiving system for receiving signals of first and second similar frequencies comprising:

a 180-degree hybrid in the form of a transmission line ring to phase shift and combine signals of the first frequency received by a first antenna;

a common transmission line section to provide signals of the first and second frequency to a receiver input;

a first transmission line section coupled between the 180-degree hybrid and the common transmission line section;

a first transmission line stub section coupled to the first transmission line section to reduce propagation of signals of the second frequency along the first transmission line section;

a second transmission line section to provide signals of the second frequency from a second antenna, the second transmission line section coupled to the common transmission line section, and

a second transmission line stub section coupled to the second transmission line section to reduce propagation of signals of the first frequency along the second transmission line section,

wherein the first, second and common transmission lines have substantially the same impedance as each other and throughout their length,

wherein ends of the first and second transmission line sections form a junction with an end of the common transmission line section;

wherein the first transmission line stub section is positioned a first distance from the junction, the first distance being substantially equal to an odd multiple number of quarter-wavelengths of the second frequency, and

the second transmission line stub section is positioned a second distance from the junction, the second distance being substantially equal to an odd multiple number of quarter-wavelengths of the first frequency.

18. The antenna receiving system as claimed in claim 17 further comprising:

a first 90-degree hybrid to combine signals of the second frequency received by the second antenna and coupled with the second transmission line section.

19. The antenna receiving system as claimed in claim 18 further comprising second and third 90 degree hybrids to phase shift and combine a plurality of signals from the first antenna and provide combined signals to the 180 degree hybrid.

20. The antenna receiving system as claimed in claim 19 wherein the first antenna is a microstrip patch antenna to receive Global Positioning System (GPS) L1 frequency signals, and the second antenna is a microstrip patch antenna to receive GPS L2 frequency signals.

21. The antenna receiving system as claimed in claim 20 wherein the transmission line ring, the first, second and third hybrids, the common transmission line section, the first and second transmission line sections and the first and second transmission line stub sections are comprised of either microstrip or stripline transmission lines, the common transmission line section.