JPH10224142A - Resonance frequency switchable inverse f-type antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna which is used in a broad band by switching a resonance frequency and moreover is miniaturized. SOLUTION: A flat plate element 2 is arranged, facing a ground plate 1, and a feeding part 3 is provided around the element 2. Short pins 4, 4a and 4b are arranged at places that are separated from the part 3 around the element 2. The pins 4, 4a and 4b are connected to the plate 1 through switches SW1 to SW3 and an impedance matching circuits 5. The switches SW1 to SW3 are on-off controlled by a control circuit 6.

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 telephone, and more particularly, to a TDMA (Time Division Multiplex Communication) / F.
The present invention relates to an antenna suitable for a DD (Frequency Division Duplex) system telephone.

[0002]

2. Description of the Related Art In recent years, an inverse F which can be downsized by mobile communication has been developed.
Type antennas are often used. FIG.
The example of a type antenna is shown. A flat plate element 2 is arranged so as to face the ground plate 1 shown in the drawing, and a feeder 3 is provided around the flat plate element 2. A short pin 4 is arranged at a position in the periphery of the flat plate element 2 away from the power supply unit 3. Such an inverted-F type antenna has one resonance frequency, and the resonance frequency is the distance L shown in FIG. 2, that is, the distance from the point farthest from the short pin 4 of the flat plate element 2 to the short pin 4. It becomes low when the distance is long, and becomes high when the distance of L is short.

In addition, the usable bandwidth becomes narrower due to the miniaturization of the antenna, and in a system having different transmission and reception frequencies such as a TDMA / FDD type mobile phone, one of the above-mentioned inverted F-type antennas is used for either one. Could only be used for

As described above, an antenna having one resonance frequency has a narrow usable bandwidth. Conventionally, a whip antenna, a helical antenna, or the like can cover the transmission / reception band with one antenna. That is, communication with the base station uses only the analog band and performs transmission and reception. However, recently, the transmission and reception bands have to be shifted based on the instructions of the base station, and TDMA-F
In a mobile phone of the DD digital system, when the above-described antenna is used and the frequency is different between transmission and reception and the frequency must be shifted to a different band (for example, switching the analog band to the digital band). Transmission / reception) has a problem that the bandwidth is not enough.

FIG. 4 shows an example of a conventional inverted-F antenna having a wide frequency band. As shown in the figure, a flat plate element 2a and a flat plate element 2b facing the ground plate 1 are arranged side by side,
Power is supplied to each element by the power supply units 3a and 3b. Then, the length L of both elements is made equal, and the element width We1,
By changing We2 and the widths Ws1 and Ws2 of the grounding portions, the resonance frequency of both elements has a width. Such an inverted-F antenna has two resonance frequencies and a wide bandwidth as shown in FIG.

[0006]

The inverted F-type antenna having the two resonance frequencies described above has a wide bandwidth, but has a problem that the size cannot be reduced because a plurality of flat elements are arranged. It has not been practical to use it for a mobile phone that requires a small size with a wide bandwidth such that the frequency is different and a different band is used alternately.

[0007] The present invention has been made in view of the above points, and it is an object of the present invention to provide an inverted-F antenna that can be used for a wide band and that can be downsized. It is.

[0008]

An inverted-F type antenna capable of switching the resonance frequency according to the present invention is an antenna used for a TDMA / FDD telephone, and is connected between a flat plate element and ground via a switch. A plurality of short pins are provided and the switch means is turned on / off by a control circuit.

In the inverted F-type antenna, an impedance matching circuit is provided between the short pin and the ground, and a peripheral distance from a point A farthest from the feeder of the flat plate element to the short pin turned on by the switch means is arbitrarily set. , The resonance frequency can be changed.

Further, in the inverted F-type antenna, an impedance matching circuit is provided in a feed section for feeding the flat plate element, and the impedance matching circuit is controlled by the control circuit, so that the impedance matching circuit is controlled from a point A farthest from the feed section of the flat plate element. The resonance frequency can be changed by arbitrarily changing the peripheral distance to the short pin turned on by the switch means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An inverted-F antenna according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an inverted-F antenna according to an embodiment of the present invention. A flat plate element 2 is arranged so as to face the ground plate 1 shown in FIG. 1, and a feeder 3 is provided around the flat plate element 2. Short pins 4 and 4 are provided at positions around the flat plate element 2 and away from the feeder 3.
a and 4b are arranged.

The short pins 4, 4a and 4b are connected to the switch S
It is connected to the ground plate 1 via W1, SW2, SW3 and impedance matching circuits 5, 5, 5. Also,
The above-described impedance matching circuit 5 may be provided in the power supply unit 3 and the impedance matching circuit may be simultaneously controlled by the control circuit 6 that controls ON / OFF of the switches SW1, SW2, and SW3. Impedance matching circuit,
5, 5, and 5 are matched so that the antenna impedance becomes 50Ω.

The factor for determining the resonance frequency f of the antenna according to the present invention is L shown in FIG.
Short pins (4, 4) turned on by W2 and SW3
a, 4b), the height H of the flat plate element 2 from the ground plate 1, the number of short pins, the position of the short pins, and the like. The objective can be achieved by changing the distance L and the number of short pins.

With the above configuration, the control circuit 6 shorts any short pins 4, 4a, 4b to the ground plate 1, changes the resonance frequency of the antenna for transmission and reception, or switches the resonance frequency when shifting to a different band. . In this case, the antenna resonates at the highest frequency when the switches SW1, SW2, and SW3 are all on. Also, switch S
When only W1 is on, it resonates at the lowest frequency. When only the switch SW2 is on, resonance occurs at a frequency between the resonance frequency when the switch SW1 is on and the resonance frequency when the switch SW3 is on. Further, when only the switch SW3 is turned on, resonance occurs at a high frequency different from the above.

FIG. 3 shows the switches SW1, SW2, S
7 shows a diode switch as a specific configuration of W3.
In FIG. 3, the mesh wire 11 of the coaxial cable connected to the power supply unit 3
Is connected to the ground plate 1. The plate element 2 and the ground plate 1 are connected by a series circuit of a capacitor 12 and a diode 7. The connection point between the capacitor 12 and the diode 7 is connected to the control input terminal 1 via the coil 8.
0 and connected to the ground plate 1 via the capacitor 9. In such a circuit, when a voltage V is applied to the control input terminal 10, the capacitor 12 and the diode 7
Is short-circuited at a high frequency. Also, by disposing a varicap instead of the above-described diode switch, the resonance frequency can be changed to a wide band.

[0016]

The inverted F-type antenna of the present invention can be used for a wide band by switching the resonance frequency, and can be downsized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an inverted-F type antenna according to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating the principle of an inverted-F antenna.

FIG. 3 is a circuit diagram for explaining a modification of the embodiment of the present invention.

FIG. 4 is a perspective view showing an example of a conventional inverted-F antenna.

FIG. 5 is a graph showing a reflection loss characteristic of the inverted F-type antenna.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ground plate 2, 2a, 2b Flat plate element 3, 3a, 3b Feed unit 4, 4a, 4b Short pin 5 Impedance matching circuit 6 Control circuit 7 Diode 8 Coil 9 Capacitor 10 Control input terminal 11 Reticulated wire 12 Capacitor

Claims (3)

[Claims] 1. An antenna for use in a TDMA / FDD type telephone, wherein a plurality of short pins connected between a flat plate element and ground via switch means are provided, and the switch means is turned on / off by a control circuit. Inverted F-type antenna capable of switching the resonance frequency. 2. An impedance matching circuit (5) is provided between the short pin and the ground, and the short pins (4, 4a, 4a, 4a, 2. The inverted F-type antenna according to claim 1, wherein the resonance frequency can be changed by arbitrarily changing a peripheral distance (L) reaching 4b). 3. A feed point (3) for feeding power to the flat plate element, wherein an impedance matching circuit is provided, and the impedance matching circuit is controlled by the control circuit, and a point farthest from the feed section (3) of the flat plate element (2). The resonance frequency switchable inverse F according to claim 1, wherein the resonance frequency can be changed by arbitrarily changing a peripheral distance (L) from A to the short pin (4, 4a, 4b) turned on by the switch means.
Type antenna.