ANTENNA APPARATUS

• US 20120154245A1
• Filed: 02/24/2012
• Published: 06/21/2012
• Est. Priority Date: 08/25/2009
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: KOYAMA, Hiromasa, NAGUMO, Shoji, TAKATA, Masaaki, UEKI, Noriyuki
• Granted Patent: US 10,084,229 B2
• Time in Patent Office: Days
• US Class Current: 343/861
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H01Q 5/335 at the feed, e.g. for impedance matching
• CPC Class Codes: H01Q 9/40 Element having extended radiating surface
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance

Abstract

This disclosure provides an antenna apparatus in which stable antenna characteristics are maintained by detecting surrounding conditions that affect the antenna characteristics and appropriately compensating the antenna characteristics. More specifically, when surrounding condition such as a human body (e.g., a palm or fingers) approaches and enters an electric field of a pseudo dipole formed by an antenna element electrode, a stray capacitance is sensed and stable antenna characteristics are maintained by appropriately controlling an antenna matching circuit to compensate for a change in the antenna characteristics due to the approach of the surrounding condition.

Claims

1. An antenna apparatus, comprising:

an antenna element;

a feed unit;

an antenna matching circuit connected between the antenna element and a feed unit;

a capacitance detection circuit connected to the antenna element and configured to detect stray capacitance of the antenna element; and

a feedback control circuit that controls the antenna matching circuit in accordance with an output signal of the capacitance detection circuit.

2. The antenna apparatus according to claim 1, further comprising:

a reactance element on a wireless communication signal path that is a transmission path between the antenna element and the feed unit, said reactance element on said transmission path configured to prevent infiltration of a sensing signal to be detected by the capacitance detection circuit.

3. The antenna apparatus according to claim 1, comprising:

a reactance element on a sensing signal path that is a transmission path between the antenna element and the capacitance detection circuit, said reactance element on said sensing signal path configured to prevent leakage of a wireless communication signal fed to the antenna element or transmitted from the antenna element is provided.

4. The antenna apparatus according to claim 2, comprising:

a reactance element on a sensing signal path that is a transmission path between the antenna element and the capacitance detection circuit, said reactance element on said sensing signal path configured to prevent leakage of a wireless communication signal fed to the antenna element or transmitted from the antenna element is provided.

5. The antenna apparatus according to claim 1, wherein the capacitance detection circuit is a capacitance-voltage conversion amplifier circuit that includes a feedback capacitance in a feedback circuit of an inverting amplifier circuit, and that outputs a voltage which is approximately proportional to a rate of change of a detection object capacitance to the feedback capacitance.

6. The antenna apparatus according to claim 2, wherein the capacitance detection circuit is a capacitance-voltage conversion amplifier circuit that includes a feedback capacitance in a feedback circuit of an inverting amplifier circuit, and that outputs a voltage which is approximately proportional to a ratio of a rate of change of a detection object capacitance to the feedback capacitance.

7. The antenna apparatus according to claim 3, wherein the capacitance detection circuit is a capacitance-voltage conversion amplifier circuit that includes a feedback capacitance in a feedback circuit of an inverting amplifier circuit, and that outputs a voltage which is approximately proportional to a ratio of a rate of change of a detection object capacitance to the feedback capacitance.

8. The antenna apparatus according to claim 4, wherein the capacitance detection circuit is a capacitance-voltage conversion amplifier circuit that includes a feedback capacitance in a feedback circuit of an inverting amplifier circuit, and that outputs a voltage which is approximately proportional to a ratio of a rate of change of a detection object capacitance to the feedback capacitance.

9. The antenna apparatus according to claim 5, wherein the capacitance-voltage conversion amplifier circuit includes an AC signal source that generates an AC signal having a frequency sufficiently lower than a resonant frequency of the antenna element, the AC signal source being provided in an input section of the inverting amplifier circuit.

10. The antenna apparatus according to claim 6, wherein the capacitance-voltage conversion amplifier circuit includes an AC signal source that generates an AC signal having a frequency sufficiently lower than a resonant frequency of the antenna element, the AC signal source being provided in an input section of the inverting amplifier circuit.

11. The antenna apparatus according to claim 7, wherein the capacitance-voltage conversion amplifier circuit includes an AC signal source that generates an AC signal having a frequency sufficiently lower than a resonant frequency of the antenna element, the AC signal source being provided in an input section of the inverting amplifier circuit.

12. The antenna apparatus according to claim 8, wherein the capacitance-voltage conversion amplifier circuit includes an AC signal source that generates an AC signal having a frequency sufficiently lower than a resonant frequency of the antenna element, the AC signal source being provided in an input section of the inverting amplifier circuit.

13. The antenna apparatus according to claim 9, wherein a detector circuit is in an output section of the inverting amplifier circuit and is configured to detect an output signal of the inverting amplifier circuit.

14. The antenna apparatus according to claim 10, wherein a detector circuit is in an output section of the inverting amplifier circuit and is configured to detect an output signal of the inverting amplifier circuit.

15. The antenna apparatus according to claim 11, wherein a detector circuit is in an output section of the inverting amplifier circuit and is configured to detect an output signal of the inverting amplifier circuit.

16. The antenna apparatus according to claim 12, wherein a detector circuit is in an output section of the inverting amplifier circuit and is configured to detect an output signal of the inverting amplifier circuit.

17. The antenna apparatus according to claim 5, wherein an integrating circuit is in an output section of the inverting amplifier circuit and is configured to integrate an output voltage of the inverting amplifier circuit.

18. The antenna apparatus according to claim 1, wherein the antenna element is an antenna element that, as the antenna element alone, has a satisfactory radiation Q factor among a plurality of types of antenna element that can be connected to an antenna connection section of the antenna matching circuit.

19. The antenna apparatus according to claim 18, wherein selection conditions for the plurality of types of antenna element include a position of a feed point on the antenna element and a connection position of the capacitance detection circuit on the antenna element.