COMPOSITE RIGHT/LEFT HANDED (CRLH) BRANCH-LINE COUPLERS

• US 20090079513A1
• Filed: 05/16/2008
• Published: 03/26/2009
• 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 7,667,555 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 branch-line coupler apparatus for generating separate signal channels from a radio-frequency (RF) connection, comprising:

a plurality of RF connections configured for receiving an input signal;

a plurality of branch lines interconnecting said plurality of RF connections;

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

wherein at least a portion of said branch lines comprises a composite right/left handed (CRLH) TL; and

wherein capacitance and inductance contributions of a left-handed (LH) TL section and a right-handed (RH) TL section of said CRLH TL are chosen so that a phase response of said CRLH TL is dominated by an LH contribution at below a center frequency, while the phase response is dominated by an RH contribution at above the center frequency.

2. An apparatus as recited in claim 1, wherein said plurality of branch lines comprise four microstrip branch lines connected in a non-overlapping pattern between four RF connections.

3. An apparatus as recited in claim 1, wherein said CRLH TL comprises a RH-TL section on either end of a LH-TL section.

4. An apparatus as recited in claim 3:

wherein said LH-TL section comprises alternating series capacitors of value C and shunt inductors of value L and

wherein said LH-TL section is coupled to said RH-TL section with a capacitor of value 2C.

5. An apparatus as recited in claim 1, wherein said LH-TL section comprises a unit cell.

6. An apparatus as recited in claim 5, wherein said unit cell comprises a series capacitor coupled with a shunt inductor.

7. An apparatus as recited in claim 1, wherein said LH-TL section comprises a lumped element capacitor in series with a lumped element shunt-inductor.

8. An apparatus as recited in claim 1:

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

wherein each of said pass-bands has a frequency relationship; and

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

9. An apparatus as recited in claim 1, wherein said CRLH TL comprises a unit cell.

10. An apparatus as recited in claim 9:

wherein said unit cell comprises a series combination of a right-handed inductor and a left-handed capacitor; and

wherein said series combination of said right-handed inductor and said left-handed capacitor is coupled to a paralleled combination of a right-handed shunt capacitor and a left-handed shunt inductor.

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

a plurality of RF connections configured for receiving an input signal;

a plurality of branch lines interconnecting said plurality of RF connections;

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

wherein at least a portion of said branch lines comprises a composite right/left handed (CRLH) TL.

12. An apparatus as recited in claim 11, wherein said CRLH TL comprises a RH-TL section on either end of a LH-TL section.

13. An apparatus as recited in claim 12:

wherein said LH-TL section comprises alternating series capacitors of value C and shunt inductors of value L and

wherein said LH-TL section is coupled to said RH-TL section with a capacitor of value 2C.

14. An apparatus as recited in claim 11, wherein said CRLH TL comprises a unit cell.

15. An apparatus as recited in claim 14:

wherein said unit cell comprises a series combination of a right-handed inductor and a left-handed capacitor; and

wherein said series combination of said right-handed inductor and said left-handed capacitor is coupled to a paralleled combination of a right-handed shunt capacitor and a left-handed shunt inductor.

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

a plurality of RF connections configured for receiving an input signal;

a plurality of branch lines interconnecting said plurality of RF connections;

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

wherein at least a portion of said branch lines comprise one or more unit cells;

wherein at least one said unit cell comprises a series combination of a right-handed inductor and a left-handed capacitor; and

wherein said series combination of said right-handed inductor and said left-handed capacitor is coupled to a paralleled combination of a right-handed shunt capacitor and a left-handed shunt inductor.