SIGNAL PROCESSING CIRCUIT AND ANTENNA APPARATUS

• US 20120001701A1
• Filed: 09/12/2011
• Published: 01/05/2012
• Est. Priority Date: 03/13/2009
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: TANIGUCHI, Katsumi, KATO, Noboru
• Granted Patent: US 8,912,906 B2
• Time in Patent Office: Days
• US Class Current: 333/5
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: H01Q 11/08 Helical antennas
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 9/27 Spiral antennas
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

To form a signal processing circuit and an antenna apparatus that do not need a circuit to adjust resonant frequency of a resonant circuit or resonant-frequency adjustment work and that are downsized, an antenna coil and a capacitor define an antenna resonant circuit. An impedance matching circuit including capacitors, a first coil, and a second coil is provided between the antenna resonant circuit and a wireless IC. The first coil and the second coil are magnetically coupled.

Claims

1. A signal processing circuit connected to a high-frequency circuit including two terminals, the signal processing circuit comprising:

two coils that are connected to the two terminals of the high-frequency circuit and are magnetically coupled to each other.

2. The signal processing circuit according to claim 1, wherein the two coils cause signals at the two terminals to be approximately 180°

out of phase with each other.

3. The signal processing circuit according to claim 1, wherein the two terminals are balanced terminals that output or receive balanced signals, and the two coils are connected in series with the balanced terminals of the high-frequency circuit, respectively.

4. The signal processing circuit according to claim 1, wherein the two terminals are balanced terminals that output or receive balanced signals, and the two coils comprise a first coil connected to the balanced terminal of the high-frequency circuit and a second coil magnetically coupled to the first coil.

5. The signal processing circuit according to claim 1, wherein the two coils are magnetically coupled to each other such that the coils strengthen magnetic flux with each other.

6. The signal processing circuit according to claim 1, wherein the two coils have an identical coil axis and are aligned in a direction of the coil axis.

7. The signal processing circuit according to claim 1, wherein the two coils are located on a plane, and one of the two coils is disposed inside the other coil.

8. The signal processing circuit according to claim 1, wherein the two coils have an identical inductance.

9. The signal processing circuit according to claim 1, wherein the two coils are provided on a multilayer substrate comprising a magnetic substance.

10. The signal processing circuit according to claim 9, wherein at least a portion of a circuit electrically connected to the two coils is disposed on or within the multilayer substrate.

11. An antenna apparatus comprising:

the signal processing circuit according to claim 1;

wherein

the high-frequency circuit is a wireless IC for use in a wireless IC device to communicate with an external device wirelessly; and

the signal processing circuit is included in an impedance matching circuit connected between an antenna resonant circuit and balanced terminals, the antenna resonant circuit comprising an antenna coil to transmit or receive signals to or from the external device wirelessly.