JP2002208871A - Portable radio communication machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and inexpensive portable radio communication machine which uses two frequency bands at different timings. SOLUTION: In a portable telephone set using a 800 MHz band and a 1,500 MHz band at different timings, the capacitance value of a varicap diode 3 is controlled. Thus, the resonance frequency of an antenna 1 is set to be the 800 MHz when the 800 MHz band is used and to be a 700 MHz band, when using the 1,500 MHz band. Then, the resonance of the 1,500 MHz band is obtained at twice the resonance. Consequently, the portable telephone set using the two frequency bands can be constituted in the same size and cost as a portable telephone set, using the single-frequency band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable radio communication device, and more particularly, to a portable radio communication device that transmits and receives signals using two frequency bands at different timings.

[0002]

2. Description of the Related Art Conventionally, there are portable telephones that transmit and receive signals using the 800 MHz band and portable telephones that transmit and receive signals using the 1500 MHz band.
For example, when considering a mobile phone in which these two types of mobile phones are combined into one, an 800 MHz band and a 1500 MHz band are considered.
The following three methods are conceivable as methods for using both of the Hz bands.

In a first method, an LC parallel resonance circuit 13 is provided between an antenna 11 and a transmission / reception circuit 12, as shown in FIG.
It is a method of providing. 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] A second method is to add a variable reactance element to an antenna resonating in the 800 MHz band to provide a 1500 MHz signal.
This is a method of moving the resonance frequency to the Hz band. The third method is to use a small antenna for 800 MHz band and 1500 MHz.
This is a method of separately providing a small antenna for the z band.

[0005]

However, according to the first method, a high-Q LC parallel resonance circuit which can be combined with a small-Q antenna having a high Q cannot be constituted by a chip capacitor and a chip inductor. , Because large and expensive dielectric resonators must be used,
There is a problem that the size and price of the mobile phone are increased.

According to the second method, when a varicap diode is used as a variable reactance element, the change in reactance at 800 MHz is limited to about 200 Ω in the current technology, and the change in reactance at 800 MHz is 150 MHz.
The amount of change in reactance is too small to configure an antenna that can support both the 0 MHz band. When a PIN diode and a chip inductor are used as the variable reactance elements, the element that does not cause self-resonance at the operating frequency is at most several tens of nH, and the change in the reactance at 800 MHz is limited to about 200Ω. too small.

In the third method, since two antennas are used, there is a problem that the size and the price of the antenna part are doubled as compared with the conventional method, and the size and the price of the portable telephone are increased.

Therefore, the main object of the present invention is to
An object of the present invention is to provide a small and inexpensive portable wireless communication device that can use two frequency bands at different timings.

[0009]

A portable radio communication device according to the present invention uses a first frequency band and a second frequency band higher than the first frequency band at different timings to transmit signals. A portable wireless communication device for transmitting and receiving signals, wherein an antenna for transmitting and receiving signals, a variable reactance element coupled to the antenna, and a reactance of the variable reactance element are controlled to use the first frequency band. Sets the antenna resonance frequency to the first frequency band, and sets the antenna resonance frequency to the second frequency band when the second frequency band is used.
And a control circuit for setting the frequency band to approximately one-fourth of the above frequency band.

[0010] Preferably, the first frequency band is 800 MHz.
The z-band, the second frequency band is the 1500 MHz band, and the control circuit sets the resonance frequency of the antenna to the 700 MHz band which is approximately half of the 1500 MHz band when using the 1500 MHz band.

Preferably, the variable reactance element is a varicap diode.

[0012]

FIG. 1 is a circuit block diagram showing a configuration of a portable telephone according to an embodiment of the present invention.
1, this mobile 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.

In order to reduce the size of the mobile phone, a small antenna 1 is used. Since antenna 1 is small, Q
High antenna. 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 frequency used. The chip inductor 4 is connected between the input / output node 2a of the transmission / reception circuit 2 and a line of the ground potential GND,
It is provided for matching.

The choke coil 5 and the capacitor 6 are
It is connected in series between the base end 1a of the antenna 1 and the line of the ground potential GND. Output node 7a of 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 performs transmission / reception in the 800 MHz band, it 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.

Next, the operation of the portable telephone will be described. If the mobile phone operates in the 800 MHz band,
The voltage generating circuit 7 applies 3 V to the cathode of the varicap diode 3 (the base end of the antenna 1). At this time, as shown in FIG. 2, the combined impedance of the small antenna 1 and the varicap diode 3 moves clockwise as the frequency increases, and the combined impedance of the chip inductor 4 as shown in FIG. Change. At this time, double resonance caused by resonance in the 800 MHz band occurs at 1600 MHz.

When the portable telephone operates in the 1500 MHz band, 0 V is applied to the cathode of the varicap diode 3 by the voltage generation circuit 7, and 3 V is applied to the cathode of the varicap diode 3.
The capacitance value of the varicap diode 3 is larger than when operating in the MHz band. Thereby, 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 the reactance differs depending on the frequency band.
Around 00 MHz moves to the point B in the figure. Further, the combined impedance of the chip inductor 4 changes as shown in FIG.
Resonates in the MHz band.

In this embodiment, the resonance frequency of the small antenna 1 in the 800 MHz band is
To 700 MHz band, and 15 times
A resonance in the 00 MHz band is obtained. Therefore, it is possible to configure a TDMA type mobile phone that uses both the 800 MHz band and the 1500 MHz band at different timings with a size and a price almost the same as those of a mobile phone using a single frequency band.

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 components increases and the current consumption increases as compared with the case where the varicap diode 3 is used.

The embodiments disclosed this time are to be considered in all respects as illustrative 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]

As described above, in the portable radio communication device according to the present invention, an 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 frequency band, and the second frequency band is used. In such a case, a control circuit is provided for setting the resonance frequency of the antenna to a frequency band that is substantially a multiple of the second frequency band. Therefore, it is possible to configure a portable wireless communication device using two frequency bands at the same size and price as a portable wireless communication device using a single frequency band.

Preferably, the first frequency band is 800 MHz
The z-band, the second frequency band is the 1500 MHz band, and the control circuit sets the resonance frequency of the antenna to the 700 MHz band which is approximately half of the 1500 MHz band when using the 1500 MHz band. The present invention is particularly suitable in this case.

Preferably, the variable reactance element is a varicap diode. In this case, the number of components is small, and the current consumption is small.

[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.

FIG. 3 is another impedance chart for explaining the operation of the mobile phone shown in FIG. 1;

FIG. 4 is another impedance chart for explaining the operation of the mobile phone shown in FIG. 1;

FIG. 5 is 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.

[Description of Signs] 1,11 Small antenna, 2,12 Transmitter / receiver 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)

[Claims] 1. A portable wireless communication device for transmitting and receiving signals by using a first frequency band and a second frequency band higher in frequency than the first frequency band at different timings, wherein: An antenna for performing transmission and reception of the antenna, a variable reactance element coupled to the antenna, and controlling the reactance of the variable reactance element to change the resonance frequency of the antenna to the first frequency band when using the first frequency band. And a control circuit that sets the resonance frequency of the antenna to a frequency band that is substantially a multiple of the second frequency band when the second frequency band is used. 2. The first frequency band is an 800 MHz band, the second frequency band is a 1500 MHz band, and the control circuit sets the resonance frequency of the antenna to 1500 MHz when using the 1500 MHz band. 2. The portable radio communication device according to claim 1, wherein the band is set to a 700 MHz band which is approximately one half of the band. 3. The portable wireless communication device according to claim 1, wherein the variable reactance element is a varicap diode.