Antenna apparatus
First Claim
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1. An antenna apparatus, comprising:
- a substrate ground electrode;
an antenna element electrode that forms an electric field with the substrate ground electrode and radiates an electromagnetic wave by the electric field;
an antenna matching circuit that performs antenna matching;
a capacitance detection circuit that detects a capacitance between the antenna element electrode and the substrate ground electrode, converts a change of the capacitance into a change of voltage, and outputs the change of the voltage; and
a feedback control circuit that controls the antenna matching circuit on the basis of the change of the voltage, whereinthe 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.
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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.
19 Citations
8 Claims
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1. An antenna apparatus, comprising:
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a substrate ground electrode; an antenna element electrode that forms an electric field with the substrate ground electrode and radiates an electromagnetic wave by the electric field; an antenna matching circuit that performs antenna matching; a capacitance detection circuit that detects a capacitance between the antenna element electrode and the substrate ground electrode, converts a change of the capacitance into a change of voltage, and outputs the change of the voltage; and a feedback control circuit that controls the antenna matching circuit on the basis of the change of the voltage, 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification