Composite right/left handed (CRLH) couplers

• US 20050253667A1
• Filed: 03/28/2005
• Published: 11/17/2005
• Est. Priority Date: 03/26/2004
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Itoh, Tatsuo, Okabe, Hiroshi, Lin, I-Hsiang, Caloz, Christophe
• Granted Patent: US 7,508,283 B2
• Time in Patent Office: Days
• US Class Current: 333/118
• CPC Class Codes: H01P 5/227 90° branch line couplers

Abstract

High-frequency couplers and coupling techniques are described utilizing artificial composite right/left-handed transmission line (CRLH-TL). Three specific forms of couplers are described; (1) a coupled-line backward coupler is described with arbitrary tight/loose coupling and broad bandwidth; (2) a compact enhanced-bandwidth hybrid ring coupler is described with increased bandwidth and decreased size; and (3) a dual-band branch-line coupler that is not limited to a harmonic relation between the bands. These variations are preferably implemented in a microstrip fabrication process and may use lumped-element components. The couplers and coupling techniques are directed at increasing the utility while decreasing the size of high-frequency couplers, and are suitable for use with separate coupler or couplers integrated within integrated devices.

Claims

1. A coupler apparatus for generating separate signal channels from a radio-frequency input, comprising:

an input line configured for receiving a high-frequency input signal;

a transmission line connecting said input line to an output line and to at least one separate signal channel; and

means for creating a left-handed relationship between phase and group velocities within at least a portion of said transmission line.

2. A coupler as recited in claim 1, wherein said coupler is configured for operation at high-frequency on or above approximately 100 MHz.

3. A coupler as recited in claim 1, wherein said couplers include left-handed unit cells having an electrical length less than π

/2.

4. A coupler as recited in claim 1, wherein said means of creating said left-handed relationship comprises an artificial composite left-handed (LH) transmission line (TL), or an artificial composite right/left-handed (CRLH) transmission line (TL).

5. A coupler as recited in claim 1, wherein said coupler comprises a coupled-line backward coupler with two parallel LH-TLs.

6. A coupler as recited in claim 5, wherein said backward coupler is configured with a gap ratio s/h which can be increased up to a ratio s/h of approximately ¼

.

7. A coupler as recited in claim 1, wherein said coupler comprises a hybrid ring coupler with at least one portion of the ring implemented with LH-TL providing a negative phase rotation.

8. A coupler as recited in claim 7, wherein said negative phase rotation comprises a −

90°

phase rotation to replace an RH-TL section with a 270°

phase shift.

9. A coupler as recited in claim 1:

wherein said coupler comprises a branch-line coupler with microstrip line interconnecting said inputs with more than one output; and

wherein at least one said microstrip line includes an LH-TL portion.

10. A coupler as recited in claim 9, wherein said LH-TL portion comprises discrete capacitors and inductors.

11. A backward-coupler apparatus for generating separate signal channels from a radio-frequency (RF) input, comprising:

an input line configured for receiving a high-frequency RF input signal;

a first left-handed (LH) transmission line (TL) connecting said input line to an output line;

wherein said LH-TL is configured for generating anti-parallel phase and group velocities; and

a second LH-TL terminating in a coupled output and an isolated output, said second LH-TL positioned parallel to and in sufficient proximity with said first left-handed transmission line to generate a backward wave.

12. A backward-coupler as recited in claim 11, wherein said backward-coupler is configured to a −

3 dB bandwidth on the order of 35%.

13. A backward-coupler as recited in claim 11, wherein said LH-TL comprises a combination of series capacitors with shunt-shorted inductors.

14. A backward-coupler as recited in claim 13, wherein said combination comprises capacitors of value 2 C in series with inductors of value L.

15. A backward-coupler as recited in claim 13, wherein said combination comprises interdigital capacitors on either side of shunt-shorted stub inductors.

16. A backward-coupler as recited in claim 11, wherein said second LH-TL is sufficiently proximal said first LH-TL so that the gap s between said first and second LH-TLs, each of height h, can be increased up to a ratio s/h of approximately ¼

without loss of backward wave.

17. A hybrid-ring coupler apparatus for generating separate signal channels from a radio-frequency input, comprising:

an input line configured for receiving a high-frequency input signal;

a first transmission line (TL) connecting said input line to an output line;

a second TL connected between said input line and said output line to form a ring; and

wherein at least a portion of said first TL or said second TL, incorporates one or more left-hand (LH) TL sections in which anti-parallel phase and group velocities are generated.

18. A hybrid-ring coupler as recited in claim 17, further including a 90°

or 180°

, isolated, output or combination along said first or said second TL.

19. A hybrid-ring coupler as recited in claim 17, wherein said LH-TL section comprises multiple series capacitor with shunt inductor unit cells.

20. A hybrid-ring coupler as recited in claim 19, wherein said LH-TL section comprises lumped element capacitors in series with lumped element shunt-inductors.

21. A hybrid-ring coupler as recited in claim 19, wherein said LH-TL section generates a −

90°

phase rotation which replaces a +270°

phase rotation of a conventional RH-TL.

22. A hybrid-ring coupler as recited in claim 17, wherein at least a portion of said first TL or said second TL comprises a composite right/left-handed (CRLH) TL having alternating RH-TL and LH-TL sections providing a total phase rotation of −

90°

.

23. A hybrid-ring coupler as recited in claim 22, wherein three LH-TL sections each generate a −

35°

rotation and each of three interposed RH-TL sections generate 5°

rotation to provide the total of −

90°

of phase rotation.

24. A branch-line coupler apparatus for generating separate signal channels from a radio-frequency (RF) connection, comprising:

a plurality of high-frequency RF connections configured for receiving a high-frequency input signal;

a plurality of branch lines interconnecting said plurality of high-frequency RF connections;

wherein each said branch line comprises a transmission line (TL) segment;

wherein at least a portion of said branch lines incorporate left-handed (LH) TL generating a phase advance with anti-parallel phase and group velocities.

25. A branch-line coupler as recited in claim 24, wherein said plurality of branch lines comprise four microstrip branch lines connected in a non-overlapping pattern between four high-frequency RF connections.

26. A branch-line coupler as recited in claim 24, wherein each said branch line comprises a composite right/left-handed (CRLH) TL having RH-TL sections on either end of a LH-TL section.

27. A branch-line coupler as recited in claim 26, wherein said LH-TL section is configured with alternating series capacitors of value C and shunt inductors of value L and is coupled to the RH-TL section with a capacitor of value 2 C.

28. A branch-line coupler as recited in claim 24, wherein said LH-TL sections comprises multiple series capacitor with shunt inductor unit cells.

29. A branch-line coupler as recited in claim 24, wherein each of said LH-TL sections comprises lumped element capacitors in series with lumped element shunt-inductors.

30. A branch-line coupler as recited in claim 24:

wherein said branch-line coupler is configured with two pass-bands; and

wherein the frequency relationship of said two pass-bands can be set to desired frequencies which need not be harmonics of one another.