JP3226897B2 - Antenna for portable radio - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna for a portable wireless device, and more particularly to an antenna for a portable wireless device that receives two distant communication bands or a wide communication band.

[0002]

2. Description of the Related Art In a conventional antenna for a portable radio, in order to reduce the size of a linear antenna, a technique for forming a helical antenna by spirally forming a radiation conductor has been widely used. In addition, with the miniaturization of portable radios, it is necessary to realize smaller helical antennas.However, when the helical antenna is miniaturized, the bandwidth becomes narrower, and the bandwidth required for the portable radio can be covered. It becomes difficult.

In particular, portable radios having two or more separate communication bands require an antenna having a wider bandwidth to cover those bands, which hinders miniaturization. On the other hand, there is a method of devising the antenna structure so that it has two communication bands. However, since it requires a volume equivalent to the arrangement of two antenna elements, it is necessary to meet the demand for miniaturization. Can not.

As an antenna in which a communication band having a narrow communication band can be used in two communication bands separated from each other, for example, in Japanese Utility Model Application Laid-Open No. 56-95107, a ferrite bar antenna is used as shown in FIG. Two communication bands are received by short-circuiting a part of the wound coil and changing the resonance frequency of the antenna. However, if the circuit configuration as shown in FIG. 8 is adopted, the resonance frequency is determined by the number of turns of the coil 23 and the capacitance of the capacitors 27 and 28 connected in parallel. And a switch 26 for short-circuiting the capacitor to the ground and a switch 26 for switching the capacitor. In addition, since the position of the power supply terminal is changed by changing the resonance frequency, the power supply terminal also needs to be switched, and a switch 30 for that purpose is required.
This requires two switches, complicates the communication band switching circuit, and increases the mounting area. The signal thus received is mixed with a signal of a local oscillator 34 (not shown) to form an intermediate frequency, and sent to an intermediate frequency amplifier circuit (not shown).

FIG. 9 shows an antenna of Japanese Utility Model Laid-Open No. 4-10412. In this antenna, as shown in the figure, the resonance frequency is changed by inserting a conductor piece 56 inside the helical antenna and short-circuiting a part of the helical antenna. In this method, the resonance frequency is changed during the production process. Can only do
It cannot be used in a portable wireless device that receives two communication bands by switching the frequency of an antenna.

[0006]

As described above, in the method according to the prior art, the number of switches for switching the resonance frequency of the antenna increases, and the circuit becomes complicated. However, there is a problem in that the mounting area of the antenna becomes large, the antenna and its peripheral circuits become large, and the antenna cannot be applied to a portable wireless device. Further, when the antenna has two resonance frequencies, there is a problem that the volume of the antenna becomes large.

The present invention has been made in view of such a background, and an antenna for a portable wireless device characterized in that one communication band changeover switch has two separate communication bands or a wide communication band. The purpose is to provide.

[0008]

According to the first aspect of the present invention,
In the antenna for a portable wireless device, a radiating element formed on a plane, one feed terminal connected to the radiating element, and a plurality of communication band switching terminals provided at intervals in the longitudinal direction of the antenna; A switch for short-circuiting or opening between two or more terminals of the plurality of communication band switching terminals, a drive circuit for driving the switch, and a control unit for operating the drive circuit by an external signal ; S
The switch is released in the standby state and released in the call state.
Another object is to provide an antenna for a portable wireless device configured to switch a resonance frequency by selecting one of a short circuit and a short circuit .

According to a second aspect of the present invention, in the antenna for a portable wireless device according to the first aspect, one of the communication band switching terminals is shared with a power supply terminal.

According to a third aspect of the present invention, in the portable wireless device antenna according to the first or second aspect, the switch is directly short-circuited or opened by externally applying a signal.

[0011]

FIG. 1 is a block diagram showing the configuration of a helical antenna for a portable wireless device and peripheral circuits according to a first embodiment of the present invention. In this figure, reference numeral 1 denotes a helical antenna, and a power supply terminal 2 and a communication band switching terminal 3,
I have four. Reference numeral 5 denotes a communication band changeover switch which short-circuits or opens the terminals 3 and 4. A receiving circuit 6 is connected to the power supply terminal 2 and performs high-frequency amplification, frequency conversion, and demodulation of a received wave. A control circuit 7 supplies channel data to the receiving circuit 6 to determine a receiving frequency and controls the switch driving circuit 8.

Next, the operation of the first embodiment of the present invention will be described in detail with reference to FIGS. FIG. 2 shows FIG.
FIG. 2A is a diagram showing the characteristics of the helical antenna of FIG. 2, and FIG. 2A shows a case where the first communication band is separated from the second communication band.
(B) is a case where the first communication band and the second communication band are close to each other to form one wide communication band.

First, when the reception frequency is in the first communication band of FIG. 2, channel data a for determining the reception frequency is applied from the control circuit 7 to the reception circuit 6 and operates as a reception circuit in the first communication band. . Further, a communication band switching signal (for example, LOW level) linked to the channel data from the control circuit 7 is applied to the switch driving circuit 8, and the switch 5 is opened by the switch driving circuit 8, so that the helical of the first communication band is released. Act as an antenna. Therefore, the reception wave of the first communication band received by the helical antenna 1 passes through the power supply terminal 2 and is demodulated by the reception circuit 6. Next, when the reception frequency is in the second communication band, the control circuit 7 applies the channel data a of the reception frequency to the reception circuit 6 and operates as a reception circuit in the second communication band. At the same time, a band switching signal (eg, HIGH level) opposite to the first communication band, which is linked to the channel data, is applied to the switch driving circuit 8, and the switch 5 short-circuits the communication band switching terminals 3, 4 by the switch driving circuit 8. However, as the effective length of the helical antenna decreases, the resonance frequency increases, and the helical antenna operates as a helical antenna in the second communication band.

A reception wave of the second communication band received by the helical antenna 1 passes through the power supply terminal 2 and is demodulated by the reception circuit 6. Here, the helical antenna 1 can adjust the frequency of the first communication band by adjusting the total length, and the interval between the first communication band and the second communication band is determined by the communication band switching terminals 3 and 4. , The desired communication band interval can be obtained. At this time, if the horizontal axis represents the frequency and the vertical axis represents the reflection loss of the antenna, the reflection loss characteristics of the helical antenna are as shown in FIG. 2A, and two bands can be covered. In addition, by overlapping the first communication band and the second communication band, FIG.
It is also possible to operate as a broadband helical antenna as shown in FIG.

FIG. 3 shows the communication band changeover switch 5 of FIG.
And a specific circuit diagram of the switch drive circuit 8 portion. Here, the switch section 5 of the helical antenna 1 is configured using a diode. In this figure, capacitors C2 and C3 are provided so that their impedance is sufficiently low in the reception frequency band, and the choke coil L
1, L2 are chosen such that their impedance is sufficiently high. Similarly, for the capacitor C4,
It is selected so that the impedance is sufficiently low in the reception frequency band.

In the operation shown in FIG. 3, first, when the band switching signal output from the control circuit 7 is at the HIGH level, the semiconductor switch SW1 is turned on, a current flows through the diode D1, and the diode D1 is turned on. At this time, capacitors C2 and C
3 is selected so as to exhibit a sufficiently low impedance in the reception frequency band, the communication band switching terminals 3 and 4 are short-circuited at a high frequency, and the resonance frequency of the antenna is increased. Since L1 and L2 show sufficiently high impedance in the reception frequency band, the influence of the impedance of the circuit on the power supply side can be almost ignored.

Next, when the band switching signal is at the LOW level, the switch SW1 is turned off and no current flows, so that the diode D1 has a high impedance, the communication band switching terminals 3 and 4 are open, and resonance of the antenna occurs. The frequency will be lower. Note that the diode D1 has such a characteristic that the larger the flowing current, the lower the impedance at the time of ON.
For this reason, the value of the resistor R1 is determined so that a current flows so that the impedance when the diode D1 is ON becomes a desired value.

In the case of FIG. 3, a portable radio device used in a communication system that receives in the first communication band having a low frequency during standby and uses a specific frequency in the communication bands 1 and 2 only when a communication state is established. , Second call with high frequency
Since the current flows through the communication band switching circuit only when the communication band is selected, it is possible to produce a great effect that current consumption can be reduced during standby.

The capacitor C1 is a capacitance for helical antenna matching, and is on the order of several picofarads. The capacitance of each of the capacitors C2 and C3 and the choke coils L1 and L2 is appropriately selected depending on the frequency band to be used. However, in communication in a frequency band of about 1800 MHz, the values of these elements are determined by the values of the capacitors C2 and C3. It is desirable that the size is about 100 picofarads and the choke coils L1, L2 are about 100 nanohenries. In this embodiment, since a diode is used for the communication band changeover switch, a switch driving circuit is necessary. However, an element that can be directly controlled by the control circuit,
For example, when a GaAs semiconductor switch or the like is used,
The switch drive circuit can be omitted.

FIG. 4 shows a second embodiment of the present invention.
At a high frequency of about 1800 MHz, if the distance between the helical antenna and the communication band switching circuit is not sufficient, it may hinder the emission of radio waves from the helical antenna. However, one of the communication band switching terminals must be shared with the power supply terminal. By
The communication band changeover switch can be mounted near the power supply terminal side of the helical antenna, and does not hinder radiation from the helical antenna. Also in this case, the frequency of the first communication band can be adjusted by adjusting the total length of the helical antenna 1, and the interval between the communication bands 1 and 2 can be changed by changing the position of the communication band switching terminal 3. A desired communication band interval can be obtained.

The operation of the two embodiments of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and is within a range not departing from the gist of the present invention. Even a design change or the like is included in the present invention.

For example, as shown in FIG. 5, an antenna 9 in which a part of an antenna element is straightened, as shown in FIG. 6, an antenna 10 formed on the same plane, or FIG.
As shown in the above, in any case of the antenna 11 in which the antenna element is formed in a sawtooth shape, the resonance frequency of the antenna can be switched as in the above-described embodiment.

[0023]

As described above, according to the present invention, a plurality of distant communication bands and a wide communication band can be covered by changing a resonance frequency of an antenna by switching a communication band switch according to a reception frequency. Can be
In addition, since there is only one switch for switching, the number of parts can be significantly reduced, and the effect of reducing the size of the antenna can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a helical antenna for a portable wireless device and peripheral circuits according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating characteristics of the helical antenna of FIG. 1;

FIG. 3 is a specific circuit diagram of a communication band changeover switch of FIG. 1 and a switch driving circuit portion.

FIG. 4 is a block diagram showing a configuration of a helical antenna for a portable wireless device and peripheral circuits according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a helical antenna for a portable wireless device in which a part of an antenna element according to a third embodiment of the present invention is straightened.

FIG. 6 is a block diagram showing a configuration of a portable wireless device antenna formed on the same plane according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of an antenna for a portable wireless device in which an antenna element according to a fourth embodiment of the present invention is formed in a sawtooth wave.

FIG. 8 is a circuit diagram of a communication band switching type antenna according to the related art.

FIG. 9 is a sectional view of a helical antenna having a variable resonance frequency according to the related art.

[Explanation of symbols]

 1, 9, 10 Helical antenna 2 Feeding terminal 3, 4 Communication band switching terminal 5 Switch 6 Receiving circuit 7 Control circuit 8 Switch driving circuit D1 Diode L1, L2 Choke coil C1-C4 Capacitor R1 Resistance SW1 Switch

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-14040 (JP, A) JP-A-58-138102 (JP, A) JP-A-4-196603 (JP, A) JP-A-4-196603 334201 (JP, A) Japanese Utility Model 48517 (JP, U) Japanese Utility Model 557912 (JP, U) Japanese Utility Model 58-43009 (JP, U) Japanese Utility Model 57-171304 (JP, U) Japanese Utility Model Showa 59-177207 (JP, U) Japanese Utility Model Showa 60-30646 (JP, U) Japanese Utility Model Hei 4-8517 (JP, U) Japanese Utility Model Showa 56-95107 (JP, U) Japanese Utility Model Showa 62-44538 (JP, U) Japanese Utility Model Application Hei 6-81118 (JP, U) Japanese Utility Model Application Sho 62-143307 (JP, U) Patent 3098430 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01Q 1/24-1/38 H01Q 9/14 H01Q 11/08 H04B 1/38

Claims (6)

(57) [Claims] An antenna for a portable wireless device, comprising: a radiating element formed on a plane; a plurality of communication terminals provided at a distance from one feeding terminal connected to the radiating element to a length direction of the antenna; A band switching terminal, a switch for short-circuiting or opening between two or more terminals of the plurality of communication band switching terminals, a driving circuit for driving the switch, and a control unit for operating the driving circuit by an external signal It consists of a, the switch is opened in a standby state, in call state
An antenna for a portable wireless device, wherein either one of an open or a short circuit is selected . 2. The antenna for a portable wireless device according to claim 1, wherein one of said communication band switching terminals is shared with a power supply terminal. 3. The switch according to claim 1, wherein two or more of the plurality of communication band switching terminals are short-circuited or opened by a semiconductor switch that opens and closes in response to a signal directly supplied from a control unit. An antenna for a portable wireless device according to claim 1 or claim 2. 4. The portable radio antenna according to claim 1, wherein a part of the antenna element is straight. 5. The portable radio antenna according to claim 1, wherein the switch is opened in a standby state and one of an open state and a short circuit is selected in a call state. 6. A signal from the outside, mobile phone antenna according to any one of claims 1 to 5 linked to the channel data of the receiving circuit, characterized in that applied to said control unit.