JP4254401B2 - Portable wireless terminal and antenna selection method thereof - Google Patents

Description

  The present invention relates to a portable radio terminal and an antenna selection method thereof, and more particularly to a transmission / reception antenna selection control method in a portable radio terminal having a plurality of antennas.

  In general, when an antenna used for a portable wireless terminal is affected by the human body (especially when it is close to the head in a call state that is in use or when a hand is approached during key operation) Antenna characteristics deteriorate. For this reason, reception sensitivity is deteriorated and transmission output is lowered, and it becomes difficult to maintain a stable line connection state.

  In particular, in the case of a portable wireless terminal having a built-in antenna, since the user cannot recognize the mounting position of the antenna, the possibility of being affected by the human body becomes very large. Also, in this case, since the user cannot recognize that the reception sensitivity has decreased due to the influence of the antenna, it is determined that the sensitivity of the mobile wireless terminal itself is poor, causing a suspicion that it is a defective product, and consequently It can be a claim against the manufacturer.

  In portable radio terminals, there are so-called diversity-type terminals that are provided with a plurality of antennas, receive received radio waves having different reception paths, and select the antenna having the stronger radio wave (Patent Documents 1 and 2). reference).

JP 2000-183793 A JP 2002-261665 A

  In the techniques disclosed in Patent Documents 1 and 2 described above, the reception sensitivity is lowered due to the influence of the human body because it is a method of selecting one of a plurality of antennas as a transmission / reception antenna according to the reception level. It is impossible to determine whether the reception sensitivity has decreased in the weak electric field area. As described above, it is necessary to prevent a decrease in reception sensitivity due to the influence of the human body and maintain a stable line connection state.

  An object of the present invention is to provide a portable radio terminal and a method for selecting an antenna thereof, in which when the performance of an antenna in use deteriorates due to the influence of a human body, this is correctly detected and switched to the other antenna. .

The portable wireless terminal according to the present invention is a portable wireless terminal that selects a plurality of antennas to be a transmission / reception antenna, and performs control for selecting the plurality of antennas according to a transmission signal level supplied to the antenna. means seen including, said control means includes comparing means for comparing the transmission signal level and the predetermined level when you have selected one of the plurality of antennas, the transmission level is the predetermined this comparison Means for selecting another antenna when the level drops below the first level, first branch detection means for generating the predetermined level by branch detection of the output of the transmission power amplifier, and this first branch detection And an isolator connected to the output of the means, and a second branch detection means connected to the output of the isolator for branch detection of the transmission signal supplied to the antenna. , The comparison means is characterized in that so as to compare the output of said predetermined level and said second branch detection means.

An antenna selection method for a portable radio terminal according to the present invention is an antenna selection method for a portable radio terminal in which a plurality of antennas are selected as transmission / reception antennas, and the plurality of antennas are selected according to a transmission signal level supplied to the antenna look including a control step of forming the antenna selection control, wherein the control step includes a comparing step of comparing the transmission signal level and the predetermined level when you have selected one of the plurality of antennas, the A step of selecting another antenna when the transmission level falls below the predetermined level by comparison, and branch detecting the output of the transmission power amplifying unit to generate the predetermined level. And a second branch detection step for branch detection of the output that passed through the isolator of the output of the first branch detection step. Seen, the comparing step is characterized in that so as to compare the output of said predetermined level and said second branch detection step.

  According to the present invention, since the variation of the transmission signal level supplied to the antenna is detected and the antenna selection control is performed according to the detection result, the deterioration of the antenna performance due to the influence of the human body can be accurately detected, and the optimum This makes it possible to select a suitable transmitting / receiving antenna.

  In the present invention, by utilizing the fact that the load impedance of the antenna fluctuates due to the influence of the human body and the level of the transmission signal fluctuates accordingly, this transmission signal level fluctuation is detected and antenna selection is performed accordingly. I am doing so.

  Examples of the present invention will be described below. FIG. 1 is a functional block diagram of the present invention. Referring to FIG. 1, the antennas 1 and 2 are connected to the changeover switch 3 via matching circuits 11 and 21, respectively. The changeover switch 3 is controlled by the control unit 7 and is selected so that one antenna becomes a transmission / reception antenna. These antennas 1 and 2 are preferably mounted at positions physically separated as much as possible. The changeover switch 3 is connected to the receiving unit 5 and the transmitting unit 6 by a duplexer 4.

  That is, the reception signal received by the antenna 1 or 2 passes through the matching circuit 11 or 21, is filtered by the duplexer 4, and then is input to the reception unit 5. On the other hand, the transmission signal from the transmission unit 6 is radiated from the antenna 1 or 2 after being filtered by the duplexer 4.

  The transmission unit 6 includes a modulation unit 65, a power amplifier (power amplification unit) 64 that amplifies the modulation output, a first coupler 63 that branches the amplification output, an output of the coupler 63, and a second coupler 61. , And a second coupler 61 that branches the output of the isolator 62. The output of the second coupler 61 is input to the duplexer 4 and becomes a transmission signal for feeding power to the antenna.

  The transmitter 6 further includes a first diode detector 67 for detecting the branch output of the first coupler 63, a second diode detector 66 for detecting the branch output of the second coupler 61, and these detections. A comparator 68 for level comparison of the output. This comparison output is input to the control unit 7.

  FIG. 2 is a flowchart showing the operation of the present invention including the control unit 7 of FIG. 1, and the operation of the embodiment of the present invention will be described with reference to FIG. First, it is assumed that antenna 1 is selected from antennas 1 and 2 (step S1). The antenna 1 is optimized (matched) with a specific impedance by the matching circuit 11, and can transmit and receive the most efficiently at that impedance.

  Here, when the antenna 1 is not affected by the human body, the transmission signal amplified by the power amplifier 64 is input to the duplexer 4 through the coupler 63, the anisolator 62, and the coupler 61 at substantially the same level, and further, the switch 3 Then, the signal is supplied to the antenna 1 via the matching circuit 11 and radiated. At this time, the detection diodes 66 and 67 detect the transmission signals branched from the couplers 61 and 63 and convert them into a DC voltage. These detected DC voltages are input to the level comparator 68 and are compared in level (step S2).

  When the antenna 1 is not affected by the human body, as described above, the outputs of the detection diodes 66 and 67 can be regarded as almost the same, so that the comparison output of the comparator 68 is a logical output indicating that both are equal. However, when the antenna 1 is affected by the human body, the impedance of the antenna 1 fluctuates due to the influence, and the matching circuit 11 is in a mismatched state, and efficient reception cannot be performed. As a result, the level of the transmission / reception signal decreases.

  In the transmission signal, the level after the isolator 62 is affected by the impedance variation, that is, the load variation, and the level of the transmission signal is lowered. However, the portion before the isolator 62 is affected by the load variation due to the characteristics of the isolator. There is no. Therefore, the transmission signal level does not decrease. Therefore, the DC voltage level from the detection diode 66 is smaller than the transmission level when there is no influence of the human body, but the DC voltage level output from the detection diode 67 is irrelevant to the influence of the human body, and the fluctuation does not occur. Absent.

  Therefore, by comparing the output level of the detection diode 66 with the comparator 68 using the output level of the detection diode 67 as a reference level, it is detected that the output level of the detection diode 66 has decreased. (Step S3), the output logic of the comparator 68 changes. In response to this, the control unit 7 generates a control signal for switching from the antenna 1 to the antenna 2 (step S4), and controls the changeover switch 3 for switching.

  Thereafter, the process returns to step S2, and the detection output level comparison is performed again to detect that the antenna 2 is affected by the human body. If there is, the switching control to the antenna 1 is performed in the same manner.

  Examples of portable wireless terminals in the above embodiment include a mobile phone and a PDA (Personal Digital Assistant).

It is a block diagram of the Example of this invention. It is a flowchart which shows operation | movement of the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Antenna 3 Changeover switch 4 Duplexer 5 Reception part 6 Transmission part 7 Control part 11, 21 Matching circuit 61, 63 Coupler 62 Isolator 64 Power amplifier 65 Modulation part 66, 67 Detection diode 68 Comparator

Claims (2)

A portable wireless terminal that selects a plurality of antennas as transmission / reception antennas,
Look including control means for forming a selection control of the plurality of antennas in accordance with a transmission signal level supplied to said antenna,
The control means compares the transmission signal level with a predetermined level when one of the plurality of antennas is selected, and when the transmission level falls below the predetermined level due to this comparison And means for selecting another antenna,
First branch detection means for branch detection of the output of the transmission power amplification unit to generate the predetermined level, an isolator connected to the output of the first branch detection means, and an output of the isolator connected to the output Second branch detection means for branch detection of a transmission signal supplied to the antenna,
The portable wireless terminal characterized in that the comparison means compares the predetermined level with the output of the second branch detection means . An antenna selection method in a portable wireless terminal in which a plurality of antennas are selected and used as a transmission / reception antenna,
Including a control step of performing selection control of the plurality of antennas according to a transmission signal level supplied to the antenna,
The control step includes a comparison step of comparing the transmission signal level with a predetermined level when one of the plurality of antennas is selected, and when the transmission level is lower than the predetermined level due to this comparison And selecting other antennas,
A first branch detection step for branch detection of the output of the transmission power amplifying unit to generate the predetermined level; a second branch detection step for branch detection of the output that passed through the isolator of the output of the first branch detection step; Further including
The antenna selection method according to claim 1, wherein the comparison step compares the predetermined level with an output of the second branch detection step.

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