Impedance matching circuit and antenna apparatus using the same

• US 20020118075A1
• Filed: 07/17/2001
• Published: 08/29/2002
• Est. Priority Date: 12/15/1999
• Status: Abandoned Application

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Miyazaki, Moriyasu, Nishino, Tamotsu, Endo, Tsutomu, Ohwada, Tetsu
• Application Number:
  US09/905,897
• Publication Number:
  US 20020118075A1
• Time in Patent Office: Days
• US Class Current: 333/32
• CPC Class Codes: H01Q 1/2283 mounted in or on the surface of a semiconductor substrate as a chip-type antenna or integrated with other components into an IC package
• CPC Class Codes: H01Q 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• CPC Class Codes: H01Q 1/362 for broadside radiating helical antennas
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 11/08 Helical antennas
• CPC Class Codes: H01Q 21/30 Combinations of separate antenna units operating in different wavebands and connected to a common feeder system
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them
• CPC Class Codes: H01Q 5/50 Feeding or matching arrangements for broad-band or multi-band operation

Abstract

One matching circuit (8-2) comprises a transmission line (6b) of a predetermined electrical length and a parallel resonance circuit (5) connected in parallel with the transmission line. The resonance circuit has a resonant frequency f2 and a predetermined susceptance at a frequency f1 lower than the frequency f2. ANother matching circuit (8-1) comprises a transmission line (6a) of a predetermined electrical length and a capacitor element (b 3a) connected in series with the transmission line between an input terminal (2) of an antenna (1) and the matching circuit (8-2) so that the input impedence of the antenna at the frequency f2 may match the characteristic impedance of an external circuit (10).

Claims

1. An impedance matching circuit for matching input impedance of an antenna and characteristic impedance of an external circuit with each other at two frequency bands, a frequency f1 and a higher frequency f2, comprising:

a transmission line having a predetermined electrical length, connected to the antenna in which an impedance matching has been performed at the frequency f2; and

a second matching circuit including a parallel-resonant circuit connected in parallel with said transmission line, and adapted to resonate at the frequency f2 and exhibit a predetermined susceptance value at the frequency f1.

2. The impedance matching circuit according to claim 1, further comprising:

a first matching circuit interposed between an input terminal of the antenna and said second matching circuit to match the input impedance of the antenna and the characteristic impedance of the external circuit with each other at the frequency f2.

3. The impedance matching circuit according to claim 2, wherein said first matching circuit includes a transmission line having a predetermined electrical length, connected to the input terminal of the antenna, and a capacitance device connected in series to the transmission line.

4. The impedance matching circuit according to claim 2, wherein said first matching circuit includes a transmission line having a predetermined electrical length, connected to the input terminal of the antenna, and an inductance device connected in series to the transmission line.

5. The impedance matching circuit according to claim 2, wherein said first matching circuit includes a transmission line having a predetermined electrical length, connected to the input terminal of the antenna, and a parallel-resonant circuit connected in parallel with the transmission line, composed of inductance and capacitance devices connected in parallel with each other and adapted to resonate at the frequency f1 and exhibit a predetermined susceptance value at the frequency f2.

6. The impedance matching circuit according to claim 1, wherein said second matching circuit includes a transmission line having a predetermined electrical length, a short stub connected to the transmission line, and an open stub connected to the transmission line at a place substantially identical to that for the short stub, wherein electrical lengths of the short and open stubs are set such that a sum of the electrical lengths of the short and open stubs can be roughly 1/4, or an odd number multiple, of a wavelength at the frequency f2, and a sum of susceptance values of the short and open stubs can take a predetermined susceptance value at the frequency f1.

7. The impedance matching circuit according to claim 6, wherein a first matching circuit is interposed between an input terminal of the antenna and said second matching circuit to match the input impedance of the antenna and the characteristic impedance of the external circuit with each other at the frequency f2, said first matching circuit including a transmission line having a predetermined electrical length, and connected to the input terminal of the antenna, and a reactance device connected to the transmission line.

8. The impedance matching circuit according to claim 7, wherein for the reactance device of said first matching circuit, a capacitance device having a conductor pattern connected in series to the transmission line is used, and the transmission lines of said first and second matching circuits, and the short and open stubs are constructed by using a planar transmission line.

9. The impedance matching circuit according to claim 7, wherein said first matching circuit includes a transmission line having a predetermined electrical length, and connected to the input terminal of the antenna, a short stub connected to the transmission line, and an open stub connected to the transmission line at a place roughly identical to that for the short stub, and wherein electrical lengths of the short and open stubs are set such that a sum of the electrical lengths of the short and open stubs can be roughly 1/4, or an odd number multiple, of a wavelength at the frequency f1, and a sum of susceptance values of the short and open stubs can take a predetermined susceptance value at the frequency f2.

10. The impedance matching circuit according to claim 1, wherein said second matching circuit includes a transmission line having a predetermined electrical length, a first open stub connected to the transmission line, and a second open stub connected to the transmission line at a place roughly identical to that for the first open stub, and wherein electrical lengths of the first and second open stubs are set such that a sum of the electrical lengths of the first and second open stubs can be roughly 1/2, or an integral multiple, of a wavelength at the frequency f2, and a sum of susceptance values of the first and second open stubs can take a predetermined susceptance value at the frequency f1.

11. The impedance matching circuit according to claim 10, wherein a first matching circuit is interposed between an input terminal of the antenna and said second matching circuit to match the input impedance of the antenna and the characteristic impedance of the external circuit with each other at the frequency f2, said first matching circuit including a transmission line having a predetermined electrical length, connected to the input terminal of the antenna, and a reactance device connected to the transmission line.

12. The impedance matching circuit according to claim 11, wherein for the reactance device of said first matching circuit, a capacitance device having a conductor pattern connected in series to the transmission line is used, and the transmission lines of said first and second matching circuits, and the first and second open stubs are constructed by using a planar transmission line.

13. The impedance matching circuit according to claim 11, wherein said first matching circuit includes a transmission line having a predetermined electrical length, and connected to the input terminal of the antenna, a first open stub connected to the transmission line, and a second open stub connected to the transmission line at a place roughly identical to that for the first open stub, and wherein electrical lengths of the first and second open stubs are set such that a sum of the electrical lengths of the first and second open stubs can be roughly 1/2, or an integral multiple, of a wavelength at the frequency f1, and a sum of susceptance values of the first and second open stubs can take a predetermined susceptance value at the frequency f2.

14. The impedance matching circuit according to claim 10, wherein a first matching circuit is interposed between an input terminal of the antenna and said second matching circuit, said first matching circuit including a micro strip line, and an impedance transformer provided to match the input impedance of the antenna and the characteristic impedance of the external circuit with each other at the frequency f2.

16. The impedance matching circuit according to claim 15, wherein said parallel-resonant circuit includes a short stub connected to the transmission line, and an open stub connected to the transmission line at a place roughly identical to that for the short stub.

17. The impedance matching circuit according to claim 15, wherein said parallel-resonant circuit includes a first open stub connected to the transmission line, and a second open stub connected to the transmission line at a place roughly identical to that for the first open stub.

19. An antenna apparatus according to claim 18, wherein the parallel-resonant circuit of said impedance matching circuit includes a short stub connected to the transmission line, and an open stub connected to the transmission line at a place roughly identical to that for the short stub.

20. An antenna apparatus according to claim 18, wherein the parallel-resonant circuit of said impedance matching circuit includes a first open stub connected to the transmission line, and a second open stub connected to the transmission line at a place roughly identical to that for the first open stub.

15. An impedance matching circuit comprising:

a hollow cylindrical dielectric;

a ground conductor provided in a cylindrical inner surface of said cylindrical dielectric;

a plurality of first matching circuits disposed in a cylindrical outer surface of said cylindrical dielectric to perform impedance matching at a frequency f2, each of said first matching circuits including a strip conductor constituting a micro strip line with said ground conductor via said cylindrical dielectric, a transmission line, and a capacitance device; and

a plurality of second matching circuits disposed in the cylindrical outer surface of said cylindrical dielectric and respectively connected to said plurality of first matching circuits, each of said second matching circuits including the strip conductor, a transmission line, and a parallel-resonant circuit adapted to resonate at the frequency f2 and exhibit a predetermined susceptance value at a frequency f1.

18. An antenna apparatus comprising:

a hollow cylindrical dielectric;

helical radiation devices amounting to N in number, including a strip-like conductor and helically wound on a cylindrical outer surface of said cylindrical dielectric;

a ground conductor provided in a region, the region being a part of a cylindrical inner surface of said cylindrical dielectric;

a strip conductor provided in the cylindrical inner surface of said cylindrical dielectric, constituting a micro strip line with said ground conductor via said cylindrical dielectric, and constituting a power supply line to each of said helical radiation devices;

impedance matching circuits amounting to N in number, respectively connected to said helical radiation devices, each of said impedance matching circuits including a first matching circuit having the strip conductor, a transmission line and a capacitance device, and adapted to perform impedance matching at a frequency f2, and a second matching circuit connected to the first matching circuit, the second matching circuit having the strip conductor, a transmission line, and a parallel-resonant circuit adapted to resonate at the frequency f2 and exhibit a predetermined susceptance value at a frequency f1; and

an N-distribution circuit including the strip conductor, wherein said N-distribution circuit comprises distributing terminals amounting to N in number exhibiting required distribution amplitude and phase characteristics, said distributing terminals being respectively connected to input terminals of said impedance matching circuits amounting to N in number.