JP4037327B2 - Portable radio - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a portable wireless device such as a cellular phone or a PHS (Personal Handyphone System).
[0002]
[Prior art]
As a portable wireless device, there is one shown in Patent Document 1 that uses an antenna with a high gain. This is a coaxial cable having a characteristic impedance between the linear antenna element and the antenna terminal of the internal radio circuit that is larger than the internal impedance of the internal radio circuit and smaller than the impedance of the linear antenna element in the portable radio device. The linear antenna elements are connected and resonated by the coaxial cable.
[0003]
[Patent Document 1]
JP-A-8-288723 [0004]
[Problems to be solved by the invention]
The antenna performance of the two-fold portable wireless device varies depending on the method of drawing the coaxial cable. Specifically, if the grounding position between the outer conductor of the coaxial cable and the ground plane is not optimal, there arises a problem that the reflection loss of the antenna increases and the antenna efficiency and the antenna gain deteriorate. In addition, current portable radios use different frequencies for transmission and reception, but switching the frequency used by the terminal during transmission and reception increases the antenna impedance and increases the antenna reflection loss, thus deteriorating the antenna gain. Problem arises. In addition, the distance between the human body and the terminal changes during a voice call where the terminal is in contact with the ear or during data communication where the terminal is operated by holding it in the hand, so that the antenna impedance varies and the antenna reflection loss increases, resulting in an antenna gain. This causes the problem of deterioration. Also, there are terminals that use a diversity system that has at least two antennas inside the terminal and communicates while switching to an antenna with a high reception level. However, depending on the antenna used, the grounding position between the coaxial cable and the ground plane may not be optimal. There is a problem that when the antenna is used, the reflection loss increases and the antenna gain deteriorates.
[0005]
The present invention makes the grounding position between the outer conductor and the ground plane of the coaxial cable variable, thereby reducing the antenna reflection loss, switching the frequency, changing the usage mode of the terminal, and a plurality of systems. The object is to improve the antenna gain and the antenna efficiency when the antenna is switched.
[0006]
[Means for Solving the Problems]
A portable wireless device according to the present invention includes a first board having an antenna and a ground plane, a second board having a radio circuit, a coaxial cable for feeding power from the radio circuit to the antenna, and an outer conductor of the coaxial cable at a plurality of locations. in including a ground means comprising a switch for grounding to said base plate, those having enhanced the antenna performance by changing the grounding position of the coaxial cable outer conductor by an on / off the switch.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a configuration diagram illustrating a main part of a two-fold portable wireless device according to the first embodiment. In FIG. 1, the portable wireless device according to the first embodiment includes an upper substrate 1 that is a first substrate housed in an upper housing that is a first housing, and a lower housing that is a second housing. A lower substrate 2 which is a second substrate accommodated therein is provided. The upper substrate 1 is provided with a ground plane 3 and an antenna element 4. The antenna element 4 is connected to a radio circuit 5 provided on the lower substrate 2 by a coaxial cable 6 disposed on the substrate 1. The radio circuit 5 is controlled through the control line A by the control unit 8 provided on the lower substrate 2.
[0008]
Switches 7a to 7e serving as grounding means are provided between the outer conductor of the coaxial cable 6 and the ground plane 3 at a predetermined interval in the longitudinal direction of the coaxial cable 6, and the outside of the coaxial cable 6 is opened and closed by opening and closing these switches. The conductor and the ground plane 3 are contacted and separated. Any one of the switches 7a to 7e is closed by a control signal applied through the control line B from the control unit 8 which also operates as a switch control means.
[0009]
As shown in FIG. 6, “digital band”, “analog band”, and “C band” are provided as channels for mobile communication. The digital band is assigned 940 to 958 MHz as the transmission frequency and 810 to 828 MHz as the reception frequency. The analog band is assigned 925 to 940 MHz as the transmission frequency and 870 to 885 MHz as the reception frequency. Further, the C band is assigned 893 to 898 MHz as the transmission frequency and 838 to 843 MHz as the reception frequency. For example, when transmitting and receiving using a digital band channel, the portable wireless device switches the frequency so that a frequency within a range of 940 to 958 MHz is used during transmission and a frequency within a range of 810 to 828 MHz is used during reception. Also, the portable wireless device may operate by switching the frequency band used for transmission / reception between the digital band, the analog band, and the C band. FIG. 2 is an example of an open / close (on / off) pattern of the switches 7a to 7e in which the reflection loss of the antenna element 4 is lowest when transmitting using each transmission frequency of the digital band, the analog band, and the C band. , Stored in the control unit 8.
[0010]
Next, the operation will be described. If the control part 8 which is a control means of the radio | wireless circuit 5 and switch 7a-7e recognizes the frequency band used for transmission / reception among a digital band, an analog band, and C band, For example, if it transmits / receives using a digital band, The wireless circuit 5 is set so that a frequency within a range of 940 to 958 MHz is used for transmission and a frequency of 810 to 828 MHz is used for reception. More specifically, the control unit 8 controls the wireless circuit 5 via the control line A so as to operate at the transmission frequency (940 to 958 MHz) at the time of transmission, and operates at the reception frequency (810 to 828 MHz) at the time of reception. The wireless circuit 5 is controlled via the control line A. At the same time, the control unit 8 sets the opening and closing of the switches 7a to 7e in a desired pattern by the control signal via the control line B as the operating frequency of the wireless circuit 5 is switched during transmission and reception.
[0011]
Further, by switching the switches 7a to 7e as the frequency is switched in transmission / reception, the grounding position between the outer conductor of the coaxial cable and the ground plane is adjusted to reduce the reflection loss of the antenna, as described below. It is effective even when the frequency band used for transmission / reception is switched among the digital band, the analog band, and the C band. For example, when transmitting in the C band having a transmission frequency of 895 MHz, the control unit 8 sets the radio circuit 5 via the control line A so as to operate at 895 MHz, and at the same time, according to the open / close pattern of FIG. The switch 7a is turned on via B, and the switches 7b to 7e are turned off. When transmitting in an analog band with a transmission frequency of 935 MHz, the control unit 8 sets the wireless circuit 5 via the control line A so as to operate at 935 MHz, and at the same time, according to the open / close pattern of FIG. The switch 7c is turned on via B, and the switches 7a, 7b, 7d, and 7e are turned off.
[0012]
As described above, the portable wireless device according to the first embodiment switches the grounding position by the switches 7a to 7e that are grounding means for the outer conductor of the ground plane 3 of the upper substrate 1 and the coaxial cable 6 according to the frequency used for communication. . As a result, the reflection loss of the antenna can be minimized according to the frequency to be used. When the frequency is switched during transmission and reception, or when the frequency is switched between the digital band, the analog band, and the C band. Even in such a case, the antenna gain and antenna efficiency of the portable wireless device can be maintained with high quality.
[0013]
Embodiment 2. FIG.
FIG. 3 is a configuration diagram illustrating a main part of the portable wireless device according to the second embodiment. The configuration shown in FIG. 3 is obtained by adding a detection circuit 9 to the configuration shown in FIG. The detection circuit 9 is a circuit that detects antenna impedance fluctuations, and detects impedance fluctuations by measuring the amount of reflection from the antenna. Specifically, it is realized by a directional coupler such as a coupler or an isolator inserted in the line of the coaxial cable 6. The detection circuit 9 applies the detected signal to the control unit 8 via the control line C. Since the other elements are the same as those in FIG. 1, the same reference numerals as those in FIG.
[0014]
Next, the operation will be described. A portable wireless device, particularly a mobile phone, is used next to a person's head during a voice call, held by hand when using mail, or used on a metal desk during data communication. As the human body or object approaches, the antenna impedance varies and the reflection loss of the antenna changes. The detection circuit 9 detects the antenna impedance of the used state, and transmits information on the use state of the portable wireless device to the control unit 8 by a signal from the control line C. The control unit 8 opens and closes the switches 7a to 7e so that the antenna element 4 operates under the best conditions based on the usage state information obtained from the detection circuit 9.
[0015]
As an effect of providing the detection circuit 9, the antenna impedance shifts due to the approach of a human body or an object to the antenna element 4 and the reflection loss increases. However, by detecting the change in the antenna impedance and transmitting it to the control unit 8, the control unit 8 It is possible to appropriately open and close the switches 7a to 7e through the control line B to restore the shifted antenna impedance and reduce the loss due to the reflection loss. As described above, the antenna element can be operated under the best conditions depending on the usage state of the portable wireless device.
[0016]
Embodiment 3 FIG.
FIG. 4 is a configuration diagram illustrating a main part of the portable wireless device according to the third embodiment. The portable wireless device according to the third embodiment includes a first antenna element 4a and a second antenna element 4b in order to perform diversity reception. The first antenna element 4 a is disposed at the end of the upper substrate 1 and is fed from the radio circuit 5 by the coaxial cable 6. The second antenna element 4b is disposed on the lower substrate 2 on the side closer to the upper substrate 1. The second antenna element 4b is connected to the radio circuit 5 by a coaxial cable 6a. Since other elements are the same as those in FIG. 1, the same reference numerals as those in FIG.
[0017]
The reception levels of the two antenna elements 4a and 4b are measured by the radio circuit 5 at regular time intervals, and the reception levels of each antenna element are transmitted to the control circuit 8 through the control line D. The control circuit 8 switches to the wireless circuit 5 through the control line A so as to use an antenna element having a high reception level. At the same time, the control circuit 8 appropriately switches on / off the switches 7a to 7e of the coaxial cable 6 so that the antenna gain and the antenna efficiency of the selected antenna element are increased through the control line B.
[0018]
For example, FIG. 5 is a diagram showing changes in the antenna efficiency Ea of the first antenna element 4a and the antenna efficiency Eb of the second antenna element 4b depending on the ON positions of the switches 7a to 7e. The antenna gain and antenna efficiency are determined by the magnitude of the reflection loss. The smaller the reflection loss, the higher the antenna gain and antenna efficiency. In FIG. 5, the antenna efficiency Ea of the first antenna element 4a is lowest when the switches 7b and 7c are turned on, and the antenna efficiency Eb of the second antenna element 4b is lowest when the switches 7c, 7d and 7e are turned on. It shows that the necessary antenna efficiency Emin can be obtained.
[0019]
Therefore, as a result of the radio circuit 5 measuring the reception level of each antenna, if it is preferable to use the first antenna element 4a, the control circuit 8 is instructed to turn on either the switch 7b or 7c. On the other hand, when the reception level is higher than that of the first antenna element 4a and it is preferable to use the second antenna element 4b, the control circuit 8 is instructed to turn on either the switch 7c or 7d.
[0020]
As a result, in a portable wireless device having two or more antenna elements, a plurality of antennas for performing diversity communication by selecting an optimal grounding position between the outer conductor of the coaxial cable 6 and the ground plane 3 of the upper substrate 1. Regardless of which antenna element is selected, the antenna gain and antenna efficiency can be improved while keeping the antenna reflection loss low, so that the antenna gain and antenna efficiency of each antenna element can be balanced. Therefore, the problem that the antenna gain is extremely deteriorated by the selected antenna element can be solved.
[0021]
【The invention's effect】
As described above, according to the present invention, the antenna can be used in an optimum state, and transmission / reception of the portable wireless device can be performed with high sensitivity and stability.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a main part of a portable radio apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing optimum switch conditions at each frequency used for communication according to the first embodiment.
FIG. 3 is a configuration diagram showing a main part of a portable wireless device according to a second embodiment of the present invention.
FIG. 4 is a configuration diagram showing a main part of a portable wireless device according to Embodiment 3 of the present invention.
FIG. 5 is a diagram illustrating a relationship between antenna performance and switch position of the portable wireless device according to the third embodiment.
FIG. 6 is a diagram showing frequency bands used for communication.
[Explanation of symbols]
1 upper substrate, 2 lower substrate,
3 ground plane, 4 antenna elements,
5 radio circuit, 6 coaxial cable,
6a coaxial cable, 7a-7e switch,
8 control unit, 9 detection circuit,
A, B, C, D Control lines.

Claims (5)

A first board having an antenna and a ground plane; a second board having a radio circuit; a coaxial cable feeding power from the radio circuit to the antenna; and a switch grounding the outer conductor of the coaxial cable to the ground plane at a plurality of locations. A portable radio device comprising: a grounding means configured to change the grounding position of the outer conductor of the coaxial cable by turning on / off the switch to improve the antenna performance.   The portable wireless device according to claim 1, wherein the grounding means changes a grounding position of the outer conductor of the coaxial cable in accordance with a use frequency of the wireless device.   The grounding means detects a change in the antenna impedance based on a signal from a use state detection means of a radio, and changes the grounding position of the outer conductor of the coaxial cable based on the detection result. The portable wireless device according to 1.   A second antenna element for diversity reception is added together with the antenna element, and the grounding means is used to change the grounding position of the outer conductor of the coaxial cable so that the antenna performance of the antenna and the antenna performance of the second antenna are balanced most. The portable wireless device according to claim 1, wherein the portable wireless device is adjusted to a good state.   5. The grounding means is constituted by a plurality of switches, and the grounding position of the outer conductor of the coaxial cable is changed by turning on / off the switch by a control means. The portable wireless device according to any one of the above.

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