JP4735164B2 - Wireless transmission circuit, wireless transmitter, wireless communication circuit, and wireless communication device - Google Patents

Description

  The present invention relates to a radio transmission circuit, a radio transmitter, a radio communication circuit, and a radio communication device including an antenna matching circuit automatic switching device that selects an optimum antenna matching circuit according to a communication environment, and more particularly to an actual communication environment. The present invention relates to a radio transmission circuit, a radio transmitter, a radio communication circuit, and a radio communication device including an antenna matching circuit automatic switching device that can select an optimum antenna matching circuit.

FIG. 3 shows a configuration of a conventional radio circuit. The radio circuit includes an antenna 1, an antenna matching circuit 2, an antenna switch 3, a receiving circuit 4, a transmitting circuit 6 and an LSI 8.
The antenna 1 receives an electromagnetic wave in a specific frequency band and converts it into an electric signal, and also converts the electric signal sent from the LSI 8 into an electromagnetic wave and sends it out to the atmosphere. The antenna matching circuit 2 is a circuit that performs impedance matching so that the antenna 1 can efficiently transmit and receive electromagnetic waves. The antenna switch 3 connects the antenna 1 to one of the reception circuit 4 and the transmission circuit 6. The receiving circuit 4 is a circuit that converts an analog electric signal input from the antenna 1 into a digital electric signal and outputs the digital electric signal to the LSI 8. The transmission circuit 6 is a circuit that converts a digital electrical signal input from the LSI 8 into an analog electrical signal and outputs the analog electrical signal to the antenna 1. The LSI 8 processes a digital electric signal.

  In the above configuration, the antenna matching circuit 2 is a “human body matching circuit” in which the antenna characteristics are optimal when used in a state close to a human body, or the antenna characteristics are optimal in a state of being separated from the human body. It was designed as a “non-human body matching circuit” or a matching circuit exhibiting an intermediate characteristic between them.

  When the antenna matching circuit 2 is designed as a “human body matching circuit”, the antenna characteristics during use on the head side of the human body are good, but the antenna is not used when placed on a desk or in a standby state. Characteristics deteriorate. On the other hand, when the antenna matching circuit 2 is designed as a “non-human body matching circuit”, the antenna characteristics are good when used on a desk or in a standby state, but on the human head side, etc. Antenna characteristics deteriorate during use. Furthermore, when designed to show characteristics intermediate between the “human body matching circuit” and the “non-human body matching circuit”, the antenna characteristics are the same even in any use state.

  Therefore, in the above configuration, it is difficult to ensure optimum antenna characteristics when used on the human head side, etc., or when used on a desk or the like, or during standby. If the optimum antenna characteristics cannot be ensured, it may lead to a situation in which the mobile phone cannot be used in an emergency (disaster or accident) in a weak electric field (outskirts such as the sea or mountains).

  Moreover, since loss occurs due to impedance mismatch with the antenna, a larger transmission power is required, resulting in an inefficient communication environment such as an increase in power consumption and a shortened call time.

As conventional techniques aimed at solving such problems, “a mobile phone capable of compensating for antenna impedance changes” disclosed in Patent Document 1, “mobile communication device” disclosed in Patent Document 2, and Patent “Antenna circuit and wireless transmission / reception apparatus” disclosed in Document 3, “Portable wireless device” disclosed in Patent Document 4, “Antenna matching adjustment circuit” disclosed in Patent Document 5, and Patent Document 6 "Communication cards and communication equipment".
JP 2001-0777719 A JP 2002-076982 A JP 2004-304521 A JP 09-083403 A Japanese Patent Laid-Open No. 11-251956 Re-specialized WO2002 / 069122

  The invention disclosed in Patent Document 1 is configured to switch the antenna matching circuit by detecting the presence or absence of an audio signal. In recent years, since many mobile phone terminals have a function (video phone function, hands-free call function) that can make a call without being close to the human body, the invention disclosed in Patent Document 1 Depending on the situation in which the antenna is used, it may not be possible to switch to an antenna matching circuit that provides optimum antenna characteristics.

  The invention disclosed in Patent Document 2 has a configuration in which impedance matching is switched by detecting that an earphone microphone is attached. However, since the earphone microphone is not necessarily worn when used in a state where it is not close to the human body, the invention disclosed in Patent Document 2 has optimum antenna characteristics depending on the situation in which the mobile phone terminal is used. May not be switched to the antenna matching circuit.

  The invention disclosed in Patent Document 3 has a configuration in which the matching circuit is switched by detecting whether the mobile phone is in a standby state, a normal voice call state, or a hands-free call state. However, in any of these states, the impedance of the antenna is not always constant. For example, even in the same standby state, the antenna impedance differs depending on whether the cellular phone is in a pocket of clothes or in a bag. Further, when the cellular phone is temporarily separated from the human body for some reason during a voice call, the impedance of the antenna changes. Therefore, in the invention disclosed in Patent Document 3, it may not be possible to switch to an antenna matching circuit that provides optimum antenna characteristics depending on the situation in which the mobile phone terminal is used.

  The invention disclosed in Patent Document 4 is provided with a plurality of matching devices each having different impedance matching, and the reflected power by comparing the reflected power by the matching device selected last time with the reflected power by the matching device selected this time is calculated. In this configuration, the smaller one is actually used. However, in order to obtain such a configuration, a memory for recording information indicating which matching unit was selected last time is indispensable, and thus the circuit configuration and control become complicated.

  The invention disclosed in Patent Document 5 and Patent Document 6 is configured to adjust the constant of a single antenna matching circuit according to the level of the reflected wave. In such a configuration, the control algorithm becomes complicated.

  Thus, conventionally, there is a possibility that a matching circuit suitable for the actual communication state of the terminal may not be selected, and there is a problem that control for impedance matching becomes complicated.

  The present invention has been made in view of such a problem, and provides a wireless transmission circuit, a wireless communication circuit, a wireless transmitter, and a wireless communication device that can select a matching circuit suitable for an actual communication state of a terminal with simple control. For the purpose.

In order to achieve the above object, the present invention provides, as a first aspect, an antenna for sending a radio signal at least to the atmosphere, a signal generating means for outputting an electric signal to the antenna via an antenna switch , A directional coupler that guides the reflected wave of the electrical signal reflected by the antenna to a path different from the signal generating unit via the antenna switch, and the reflected wave input from the antenna via the directional coupler And a matching circuit provided between the antenna and the antenna switch for impedance matching between the antenna and the electric signal in accordance with the detection result of the intensity of the reflected wave. And a wireless transmission circuit having a matching circuit selection means for selecting from a plurality of matching circuit groups having different characteristics. It is.

  In any of the above configurations according to the first aspect of the present invention, the matching circuit selection unit compares the intensity of the reflected wave with a predetermined threshold value, and the intensity of the reflected wave is higher than the threshold value. It is preferable to select another matching circuit instead of the currently selected matching circuit. In addition, the matching circuit group is optimal for impedance matching between the antenna and the electrical signal when the antenna is close to the human body, and is optimal for impedance matching between the antenna and the electrical signal when the antenna is separated from the human body. And a non-human body matching circuit.

  Moreover, in order to achieve the said objective, this invention provides the radio | wireless transmitter provided with the radio | wireless transmission circuit concerning the structure in any one of said 1st aspect of this invention as a 2nd aspect. .

  In order to achieve the above object, according to a third aspect of the present invention, as a third aspect, the wireless signal received via the wireless transmission circuit and the antenna according to any one of the configurations of the first aspect of the present invention is converted into an electrical signal. And a means for converting to a wireless communication circuit.

  Moreover, in order to achieve the said objective, this invention provides the radio | wireless communication apparatus provided with the radio | wireless communication circuit concerning the 3rd aspect of this invention as a 4th aspect.

  According to the present invention, it is possible to provide a wireless transmission circuit, a wireless communication circuit, a wireless transmitter, and a wireless communication device that can select a matching circuit suitable for an actual communication state of a terminal with simple control.

[First Embodiment]
A first embodiment in which the present invention is suitably implemented will be described.
FIG. 1 shows a configuration of a radio circuit according to the present embodiment. This radio circuit includes an antenna 1, an antenna matching circuit 2, an antenna switch 3, a reception circuit 4, a coupler 5, a transmission circuit 6, a smoothing circuit 7, and an LSI 8.
The antenna matching circuit 2 includes a human body matching circuit that provides optimum impedance matching while being carried, a non-human body matching circuit that provides optimum impedance matching in a state away from the human body, and a circuit that switches between them.
This wireless circuit is a circuit applied to a wireless transmitter or a wireless communication terminal (such as a mobile phone).

The transmission power output from the transmission circuit 6 is output from the antenna 1 to the atmosphere via the coupler 5, the antenna switch 3, and the antenna matching circuit 2. At this time, the reflected wave from the antenna 1 is input to the smoothing circuit 7 by the action of the coupler 5. The reflected wave input to the smoothing circuit 7 is converted into a DC voltage and input to the LSI 8. The LSI 8 includes an A / D converter (not shown) and constantly monitors the amount of reflected waves.
The above operation is repeatedly executed at predetermined intervals.

When the antenna matching circuit 2 selects the human body matching circuit, the amount of reflected waves is small because the mismatch loss is small if the user is carrying a mobile phone, and the mismatch loss if it is installed on a desk or the like. Therefore, the amount of reflected waves is large.
On the other hand, when the antenna matching circuit 2 selects a non-human body matching circuit, if the user carries a mobile phone, the mismatch loss is large and the amount of reflected waves increases. In this case, the amount of reflected wave is reduced because the mismatch loss is small.

  A threshold is set for each of the human body matching circuit selection and the non-human body matching circuit selection. If the amount of reflected waves increases (in other words, the mismatch loss increases), it is determined that the mobile phone that the user was carrying was installed on the desk or the other way around. The antenna matching circuit 2 is switched from the human body matching circuit to the non-human body matching circuit or vice versa.

  As a result, the wireless circuit according to the present embodiment has an optimum antenna matching circuit according to the situation, whether it is used while being carried by a user or installed on a desk or the like. Since it can be selected, a wireless transmission terminal equipped with this can always transmit a wireless signal with the best antenna quality. In addition, a mobile phone provided with this can always communicate with the best antenna quality. Therefore, stable communication is possible without interruption of the call or noise.

[Second Embodiment]
A second embodiment in which the present invention is suitably implemented will be described. The radio circuit according to this embodiment is substantially the same as that of the first embodiment, but includes a circulator 9 instead of the coupler 5.
Since the circuit operation in this configuration is the same as that of the first embodiment, a duplicate description is omitted.

Each of the above embodiments is an example of a preferred embodiment of the present invention, and the present invention is not limited to these.
For example, in each of the above embodiments, a mobile phone that transmits and receives radio signals has been described as an example. However, it is not always necessary to have a function of receiving radio signals, and the present invention can also be applied to a radio transmitter. It is.
In each of the above embodiments, an example is given in which one of two types of matching circuits (human body matching circuit, non-human body matching circuit) is selected according to the intensity of the reflected wave from the antenna. The above matching circuits (for example, for normal calls (for communication held on the human head side), for videophones (for communication held on a place other than the human head side), for hands-free calls (desktop) Or the like for communication))) may be selected according to the intensity of the reflected wave from the antenna.
As described above, the present invention can be variously modified.

It is a figure which shows the structure of the radio | wireless circuit concerning 1st Embodiment which implemented this invention suitably. It is a figure which shows the structure of the radio | wireless circuit concerning 2nd Embodiment which implemented this invention suitably. It is a figure which shows the structure of the conventional radio | wireless circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Antenna matching circuit 3 Antenna switch 4 Reception circuit 5 Coupler 6 Transmission circuit 7 Smoothing circuit 8 LSI
9 Circulator

Claims (6)

An antenna for transmitting at least a radio signal to the atmosphere;
Signal generating means for outputting an electrical signal to the antenna via an antenna switch ;
A directional coupler that guides a reflected wave of the electrical signal reflected by the antenna to a path different from the signal generation unit via the antenna switch ;
Means for detecting the intensity of the reflected wave input from the antenna via the directional coupler;
In order to perform impedance matching between the antenna and the electric signal according to the detection result of the intensity of the reflected wave, a matching circuit provided between the antenna and the antenna switch is provided with a plurality of matching circuits having different characteristics. A wireless transmission circuit having matching circuit selection means for selecting from a group.   The matching circuit selection unit compares the intensity of the reflected wave with a predetermined threshold value, and when the intensity of the reflected wave is higher than the threshold value, the matching circuit is changed to the currently selected matching circuit. The wireless transmission circuit according to claim 1, wherein a matching circuit is selected.   The matching circuit group includes a human body matching circuit in which impedance matching between the antenna and the electric signal is optimal when the antenna is close to the human body, and the antenna and the electric signal when the antenna is separated from the human body. The wireless transmission circuit according to claim 1, further comprising: a non-human body matching circuit that optimizes impedance matching.   A wireless transmitter comprising the wireless transmission circuit according to claim 1.   4. A wireless communication circuit comprising: the wireless transmission circuit according to claim 1; and means for converting a wireless signal received via the antenna into an electrical signal.   A wireless communication device comprising the wireless communication circuit according to claim 5.

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