Telecommunications – Transmitter and receiver at same station – With transmitter-receiver switching or interaction prevention
Reexamination Certificate
2000-09-07
2003-11-04
Trost, William (Department: 2684)
Telecommunications
Transmitter and receiver at same station
With transmitter-receiver switching or interaction prevention
C455S078000, C343S850000
Reexamination Certificate
active
06643497
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a portable telephone that eliminates the deterioration of speech quality due to the influence of a human body and more particularly, to a portable telephone that suppresses effectively or cancels the change of antenna impedance caused by approach or contact of a human body to the telephone without any measure for recognizing the approach and/or contact of the body.
2. Description of the Related Art
With radio communications devices or radio transceivers such as portable telephones, to match the output impedance value of the transmission circuit with the impedance value of the antenna and to match the input impedance value of the reception circuit with the impedance value of the antenna, various impedance matching circuits having different configurations have been used. The technique that several matching circuits with different impedance values are provided in advance and one of them is selectively used according to a specific condition has been well known.
For example, the Japanese Examined Patent Publication No. 58-51453, published on Nov. 16, 1983, discloses a “transmission device” configured in such a way that the impedance value is selected so as to maximize the power efficiency according to the transmitted output. Also, the Japanese Non-Examined Patent Publication No. 5-110454, published on Apr. 30, 1993, discloses a “radio communications apparatus”, in which several matching circuits having different impedance values are provided in advance and one of the matching circuits is selectively used by way of a switch according to the transmitted output.
In recent years, several techniques have been developed to accomplish the impedance matching in the radio communications devices or radio transceivers of this sort while taking the influence of a human body into consideration. These techniques have the intention to cancel or suppress the influence of a human body that the approach or contact of the body to the device or transceiver induces some change of the antenna impedance value, thereby deviating the antenna characteristic from its desired one.
For example, the Japanese Non-Examined Patent Publication No. 5-113216, published on May 7, 1993, discloses a “wireless remote-control device” configured in such a way that a second impedance matching circuit having a different impedance value from a first impedance matching circuit is used instead of the first impedance matching circuit within a specific time period after some kind of control operation is performed by the user or until the transmission or reception operation is finished. The impedance value is changed temporarily only when the user controls the remote-control device, because the device is affected by a human body only at that time. The remote-control device has an advantage that the means or measure for detecting and/or recognizing the body is unnecessary.
Recently, there has been the tendency that the antenna impedance value of portable telephones varies or fluctuates during the talking (i.e., calling or receiving) operation due to the influence of a human body (i.e., the user's body). This is because the distance between the user's temple and the antenna has been getting shorter according to the progress of miniaturization and weight reduction of portable telephones. Thus, impedance value mismatch tends to occur during the talking state, resulting in inconveniences such as talking or speech interception in low electrical field (weak radio wave) areas, or voice interruption during the talking state. To prevent such the deterioration of speech quality, various techniques have been developed.
For example, the Japanese Non-Examined Patent Publication No. 11-145852, published on May 28, 1999, discloses an “antenna circuit” having the following configuration. Specifically, the level of the transmission power from the antenna is detected while the level of the transmission power from the transmitter is kept constant. One of impedance matching circuits is selectively used so as to maximize the level thus detected of the transmission power from the antenna. This antenna circuit has an advantage that even if the impedance value of the antenna is changed due to the influence of a human body, an obtainable antenna gain is stable, thereby improving the speech quality.
The Japanese Non-Examined Patent Publication No. 11-136157, published on May 21, 1999, discloses a “mobile radio terminal device” capable of high-quality communication. This mobile radio terminal device comprises at least one impedance matching correction circuit and a human body recognizer for recognizing the contact of a human body, in addition to impedance matching circuits. The human body recognizer recognizes whether or not a human body is contacted with the device by way of a recognition signal outputted from the recognizer. If a human body is contacted with the device, the reception signal is transmitted to the at least one impedance matching correction circuit and one of the impedance matching circuits according to the level of the reception signal.
The wireless remote-control device disclosed in the Publication No. 5-113216 has an advantage that no measure for detecting the contact of a human body is necessary and therefore, the configuration of the device can be simplified. However, the configuration that the second impedance matching circuit is used instead of the first impedance matching circuit within a specific time period after some kind of control operation is performed by the user or until the transmission or reception operation is finished is applicable only to the wireless remote-control device. Thus, this configuration cannot be applied to portable telephones.
The antenna circuit disclosed in the Publication No. 11-145852 necessitates a circuit for detecting the level of the transmission power from the antenna while the level of the transmission power from the transmitter is kept constant, and a circuit for switching the impedance matching circuits in order to maximize the level of the transmission power from the antenna. Thus, the antenna circuit has a problem that the circuit configuration is complicated and the fabrication cost is raised.
The mobile radio terminal device disclosed in the Publication No. 11-136157 necessitates the human body recognizer for recognizing the contact of a human body and a circuit for selectively transmitting the reception signal to the at least one impedance matching correction circuit and one of the impedance matching circuits after measuring the level of the reception signal. Therefore, the mobile radio terminal device has a problem that the device configuration is complicated and the fabrication cost is increased.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a portable telephone that eliminates or suppress effectively the change of the antenna impedance due to approach or contact of a human body without any special measure for recognizing the approach or contact of a human body.
Another object of the present invention is to provide a portable telephone that ensures a desired antenna characteristic with a simple and low-cost configuration.
The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description.
A portable telephone according to the present invention is comprised of;
(a) an antenna;
(b) a radio section for processing a radio-frequency reception signal received by the antenna and for processing a radio-frequency transmission signal to be transmitted and sending the radio-frequency transmission signal thus processed to the antenna;
(c) a control section for controlling the radio section; and
(d) an impedance matching subsystem for matching an impedance of the antenna with an impedance of the radio section;
the impedance matching subsystem being designed to have different impedance values;
the different impedance values of the impedance matching subsystem being switched so as to be interlo
Harry Andrew T
McGinn & Gibb PLLC
NEC Corporation
Trost William
LandOfFree
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