JP3866923B2 - Portable wireless communication device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a portable wireless communication device, and more particularly to a portable wireless communication device that transmits and receives signals using two frequency bands at different timings.
[0002]
[Prior art]
Conventionally, there are mobile phones that transmit and receive signals using the 800 MHz band and mobile phones that transmit and receive signals using the 1500 MHz band. For example, these two types of mobile phones are combined into one. When considering a mobile phone, the following three methods are conceivable as methods using both the 800 MHz band and the 1500 MHz band.
[0003]
The first method is a method of providing an LC parallel resonance circuit 13 between the antenna 11 and the transmission / reception circuit 12 as shown in FIG. The LC parallel resonance circuit 13 includes an inductor 14 and a capacitor 15 connected in parallel. If this LC parallel resonance circuit 13 is provided, it is possible to resonate at two points of the 800 MHz band and the 1500 MHz band.
[0004]
In the second method, a variable reactance element is added to an antenna that resonates in the 800 MHz band, and the resonance frequency is moved to the 1500 MHz band. The third method is a method of separately providing a small antenna for the 800 MHz band and a small antenna for the 1500 MHz band.
[0005]
[Problems to be solved by the invention]
However, in the first method, an LC parallel resonant circuit with a high Q that can be combined with a small antenna with a high Q cannot be configured with a chip capacitor and a chip inductor, and the dielectric resonance is large and expensive. In other words, the mobile phone has to be used in a large size and high price.
[0006]
In the second method, when a varicap diode is used as the variable reactance element, the current technology limits the amount of change in reactance at 800 MHz to about 200Ω, and an antenna that can handle both the 800 MHz band and the 1500 MHz band is used. The reactance change is too small to configure. When a PIN diode and a chip inductor are used as the variable reactance element, the element that does not cause self-resonance at the operating frequency is tens of nH at most, and the reactance change amount at 800 MHz is about 200Ω. too small.
[0007]
Further, in the third method, since two antennas are used, the size and price of the antenna portion are doubled as compared with the conventional method, and there is a problem that the mobile phone becomes large and expensive.
[0008]
Therefore, a main object of the present invention is to provide a portable wireless communication device that can use two frequency bands at different timings and is small and inexpensive.
[0009]
[Means for Solving the Problems]
The portable wireless communication device according to the present invention is a portable wireless communication device that transmits and receives signals by using the first frequency band and the second frequency band on the higher frequency side than the first frequency band at different timings. Then, the antenna for transmitting and receiving signals, the variable reactance element coupled to the antenna, and the reactance of the variable reactance element are controlled, and when the first frequency band is used, the resonance frequency of the antenna is set to the first When the second frequency band is used, the resonance frequency of the antenna is set to the third frequency band closest to the first frequency band out of the approximately one- fifth frequency band of the second frequency band. adjusted to those having a control circuit Ru is a multiple resonance antenna in a second frequency band.
[0010]
Preferably, the first frequency band is the 800 MHz band, the second frequency band is the 1500 MHz band , the third frequency band is the 700 MHz band, and the control circuit uses the antenna resonance when using the 800 MHz band. the frequency to 800 MHz, Ru is multiplied resonate at 1500Hz band antenna by adjusting the resonant frequency of the antenna to substantially 1 of 700MHz band half of 1500MHz band when using the 1500MHz band.
[0011]
Preferably, the variable reactance element is a varicap diode.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a circuit block diagram showing a configuration of a mobile phone according to an embodiment of the present invention. In FIG. 1, the cellular phone includes a small antenna 1, a transmission / reception circuit 2, a varicap diode 3, a chip inductor 4, a choke coil 5, a capacitor 6, and a voltage generation circuit 7.
[0013]
In order to reduce the size of the mobile phone, a small antenna 1 is used. The antenna 1 has a high Q because of its small size. The varicap diode 3 is connected between the input / output node 2a of the transmission / reception circuit and the base end 1a of the antenna 1, and is provided to change the resonance frequency of the antenna 1 depending on the operating frequency. The chip inductor 4 is connected between the input / output node 2a of the transmission / reception circuit 2 and the ground potential GND line, and is provided for matching.
[0014]
The choke coil 5 and the capacitor 6 are connected in series between the base end portion 1a of the antenna 1 and the ground potential GND line. An output node 7 a of the voltage generation circuit 7 is connected to a node between the choke coil 5 and the capacitor 6. The voltage generation circuit 7 is controlled by the transmission / reception circuit 2. When the transmission / reception circuit 2 transmits / receives in the 800 MHz band, the voltage generation circuit 7 outputs 3 V to reduce the capacitance value of the varicap diode 3, and the transmission / reception circuit 2 transmits / receives in the 1500 MHz band. Outputs 0 V to increase the capacitance value of the varicap diode 3. The transmission / reception circuit 2 performs transmission / reception via the antenna 1 and the varicap diode 3 using the 800 MHz band and the 1500 MHz band at different timings, and controls the voltage generation circuit 7.
[0015]
Next, the operation of this mobile phone will be described. When the cellular phone operates in the 800 MHz band, 3 V is applied to the cathode of the varicap diode 3 (base end of the antenna 1) by the voltage generation circuit 7. At this time, the combined impedance of the small antenna 1 and the varicap diode 3 moves in the clockwise direction as the frequency increases as shown in FIG. 2, and the combined impedance of the chip inductor 4 as shown in FIG. Change. At this time, double resonance that occurs due to resonance in the 800 MHz band occurs at 1600 MHz.
[0016]
When the mobile phone operates in the 1500 MHz band, when the voltage generation circuit 7 operates in the 800 MHz band in which 0 V is applied to the cathode of the varicap diode 3 and 3 V is applied to the cathode of the varicap diode 3. In comparison, the capacitance value of the varicap diode 3 is increased. As a result, as shown in FIG. 4, the reactances of the antenna 1 and the diode 3 change clockwise as compared with FIG. Since the reactance 1 / ωC of the diode 3 is inversely proportional to the frequency, the amount of change in reactance varies depending on the frequency band, changes about 150Ω in the 800 MHz band, and moves around 700 MHz to the point B in the figure, and changes about 80Ω in the 1500 MHz band to 1500 MHz. The neighborhood moves to point B in the figure. Further, the combined impedance of the chip inductor 4 changes as shown in FIG. 5 and resonates in the 700 MHz band and the 1500 MHz band which is double resonance thereof.
[0017]
In this embodiment, the resonant frequency of the 800 MHz band small antenna 1 is lowered to the 700 MHz band by the varicap diode 3, and the 1500 MHz band resonance is obtained by double resonance. Therefore, a TDMA mobile phone using both the 800 MHz band and the 1500 MHz band at different timings can be configured with a size and price almost the same as a mobile phone using a single frequency band.
[0018]
Note that the resonance frequency of the antenna 1 can be changed in the same manner as described above by using a PIN diode and a chip inductor instead of the varicap diode 3. However, in this case, the number of parts is increased and current consumption is increased as compared with the case where the varicap diode 3 is used.
[0019]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0020]
【The invention's effect】
As described above, the portable wireless communication device according to the present invention controls the first frequency band by controlling the reactance of the antenna for transmitting and receiving signals, the variable reactance element coupled to the antenna, and the variable reactance element. When using the antenna, the resonance frequency of the antenna is set to the first frequency band, and when using the second frequency band, the resonance frequency of the antenna is set to the first of the frequency bands of approximately a plurality of the second frequency band . and a multiple control circuit which Ru is resonated closest third antenna is adjusted to a frequency band in the second frequency band to the first frequency band is provided. Therefore, a portable wireless communication device using two frequency bands can be configured with a size and price almost the same as a portable wireless communication device using a single frequency band.
[0021]
Preferably, the first frequency band is the 800 MHz band, the second frequency band is the 1500 MHz band , the third frequency band is the 700 MHz band, and the control circuit uses the antenna resonance when using the 800 MHz band. the frequency to 800 MHz, Ru is multiplied resonate at 1500Hz band antenna by adjusting the resonant frequency of the antenna to substantially 1 of 700MHz band half of 1500MHz band when using the 1500MHz band. The present invention is particularly suitable in this case.
[0022]
Preferably, the variable reactance element is a varicap diode. In this case, the number of parts can be reduced and the current consumption can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram showing a configuration of a mobile phone according to an embodiment of the present invention.
FIG. 2 is an impedance chart for explaining the operation of the mobile phone shown in FIG. 1;
3 is another impedance chart for explaining the operation of the mobile phone shown in FIG. 1. FIG.
4 is still another impedance chart for explaining the operation of the mobile phone shown in FIG. 1. FIG.
FIG. 5 is still another impedance chart for explaining the operation of the mobile phone shown in FIG. 1;
FIG. 6 is a circuit block diagram showing a configuration of a conventional mobile phone.
[Explanation of symbols]
1,11 Small antenna, 2,12 transceiver circuit, 3 varicap diode, 4 chip inductor, 5 choke coil, 6,15 capacitor, 7 voltage generation circuit, 13 LC parallel resonance circuit, 14 inductor.

Claims (3)

A portable wireless communication device that transmits and receives signals using a first frequency band and a second frequency band on a higher frequency side than the first frequency band at different timings,
An antenna for transmitting and receiving the signal;
A variable reactance element coupled to the antenna; and a reactance of the variable reactance element is controlled to set the resonance frequency of the antenna to the first frequency band when the first frequency band is used, and the second frequency band If the frequency band of the antenna is used, the resonance frequency of the antenna is adjusted to a third frequency band that is closest to the first frequency band out of substantially a plurality of frequency bands of the second frequency band. a control circuit which Ru is a multiple resonance the antenna in the second frequency band, the portable wireless communication device. The first frequency band is an 800 MHz band;
The second frequency band is a 1500 MHz band,
The third frequency band is a 700 MHz band;
The control circuit adjusts the resonance frequency of the antenna to 800 MHz when using the 800 MHz band, and adjusts the resonance frequency of the antenna to a 700 MHz band that is approximately one half of the 1500 MHz band when using the 1500 MHz band. multiplied Ru is resonated at 1500Hz band the antenna, the portable radio communication apparatus according to claim 1.   The portable wireless communication device according to claim 1, wherein the variable reactance element is a varicap diode.

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