JPH1079622A - Frequency sharing antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna capable of extending an antenna gain over a wide frequency band in an antenna system used for a radio communication terminal equipment or the like. SOLUTION: An electrically controllable inductance change circuit 2 is connected in series to the antenna 1. Moreover, an electrically controllable capacitance change circuit 3 is connected in parallel to the antenna 1. The resonance frequency of the antenna 1 is largely changed of a PIN diode used for a switch and the inductance change circuit 2 using a coil and is finely adjusted by using the capacitance change circuit 3 employing a varactor diode. The inductance change circuit 2 and the capacitance change circuit 3 are controlled electrically to allow the antenna 1 to cope with two frequency bands apart largely from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency sharing antenna, and more particularly to a frequency sharing antenna having a function of electrically adjusting a resonance frequency in a wide band.

[0002]

2. Description of the Related Art When a transmission frequency band and a reception frequency band are far apart from each other, for example, when a transmission frequency is 2.5 GHz and a reception frequency is 1.6 GHz as a frequency band used in a satellite communication system, an antenna device is used. Need to cover two bands separated by 0.9 GHz. In order to cover these bands with one antenna, the fractional band is about 4 with the center frequency of 2.05 GHz.
A 3.9% (0.9 / 2.05) broadband antenna is required. However, a small-sized antenna having a wide band exceeding 10% of the fractional band cannot be easily realized. The reason is that the frequency band characteristic of the antenna depends on the antenna (1
This is because the bandwidth becomes narrower when the antenna is downsized by lowering the resonance frequency by loading some lumped constant such as an inductor as compared with (/ 2λ dipole antenna). That is, miniaturization of the antenna and widening of the frequency band are contradictory characteristics. When matching is forcibly performed by the matching circuit, the band is narrowed, and the antenna efficiency is reduced due to the insertion loss of the matching circuit.

When the transmission and reception frequency bands are separated as described above, it is difficult to realize a more compact and highly efficient antenna while covering the transmission and reception frequency band with one antenna.

FIG. 6 shows an example of a conventional technique described in a public patent publication (Japanese Patent Laid-Open No. Hei 4-213907). FIG.
FIG. 6A is a configuration diagram of a conventional antenna device for changing a resonance frequency. FIG. 6A shows a configuration in which a capacitance changing circuit 3 is connected in parallel with the antenna 1, and the value of the capacitance is changed by a control signal voltage so that the resonance of the antenna 1 FIG. 6B shows a case where an inductance changing circuit 2 is connected in series with the antenna 1. Similarly, the resonance frequency of the antenna is changed by changing the value of the inductance by the control signal voltage. Is to change.

[0005]

However, in the above-mentioned conventional device, as shown in the schematic diagram of the transmission and reception frequency band of the first embodiment of the present invention in FIG. 3, the reception frequency band 5 and the transmission frequency band 6 are largely separated. In this case, the change amount is small only by the capacitance change circuit, and when the frequency is finely adjusted, it cannot be coped with only the inductance change circuit. Further, when an antenna is provided for each of the transmission and reception, there is a problem that the number of parts increases and the device becomes complicated.

An object of the present invention is to provide a frequency sharing antenna capable of obtaining a sufficient gain even in a satellite communication system in which a reception frequency band and a transmission frequency band are separated from each other. And

[0007]

According to a first aspect of the present invention, there is provided an inductance changing circuit in series with an antenna in charge of a large change in the resonance frequency of the antenna, and fine adjustment of the resonance frequency of the antenna in parallel with the antenna. A responsible capacitance changing circuit is provided, and the inductance changing circuit and the capacitance changing circuit are operated by a control signal voltage.

According to a second aspect of the present invention, a control signal voltage of the inductance changing circuit is superimposed on an antenna feed line.

[0009]

DETAILED DESCRIPTION OF THE INVENTION According to the first aspect of the present invention, the resonance frequency of the antenna is largely changed by an inductance changing circuit connected in series with the antenna, and fine adjustment is performed by a capacitance changing circuit connected in parallel with the antenna 1. Has an action.

According to a second aspect of the present invention, the resonance frequency of the antenna is changed by superimposing the control signal voltage of the inductance changing circuit on the feed line for the antenna.

(Embodiment 1) FIG. 1 is a configuration diagram of a frequency sharing antenna according to Embodiment 1 of the present invention, FIG. 2 is a circuit diagram of the frequency sharing antenna, and FIG. 3 is a schematic diagram of the transmission / reception frequency band. FIG. 4 is an equivalent circuit diagram of a frequency sharing antenna for explaining a change in resonance frequency due to the inductance changing circuit. Reference numeral 1 denotes an antenna, 7 denotes a coil used in the inductance changing circuit 2, and 8 denotes a PIN diode used as a switch for changing the value of the inductance. Reference numeral 9 denotes a terminal for applying a control signal voltage to the PIN diode 8. Reference numeral 10 denotes a choke coil for suppressing high-frequency power supplied to the antenna 1 from leaking to the terminal 9 to which the control signal voltage is applied and the ground 11. Numeral 12 denotes a varactor diode used to change the value of the capacitance, which is a capacitance changing circuit 3. Numeral 13 denotes a terminal for applying a control signal voltage of the capacitance of the varactor diode 12. 14 is P
This is a capacitor for separating the control signal voltages of the IN diode 8 and the varactor diode 12. Reference numeral 15 denotes a transmission / reception circuit.

The operation of the frequency sharing antenna configured as described above will be described with reference to the schematic diagram of the transmission / reception frequency band of FIG. 3 and the principle of operation of FIGS. 4 (a) and 4 (b). First, the resonance frequency of the antenna 1 is determined using the inductance changing circuit 2 and the transmission frequency band 6 and the reception frequency band 5 are determined.
The operation in the case where the switching is largely performed will be described. First, an equivalent circuit in which the control signal voltage is applied from the terminal 9 to the PIN diode 8 via the choke coil 10, that is, an equivalent circuit in which the PIN diode 8 is ON is shown in FIG.
As shown in FIG. 4A, it is necessary to design the antenna 1 in advance so that the resonance frequency of the antenna 1 in FIG. 4A is within the transmission frequency band 6 in FIG. In addition,
Reference numeral 16 denotes a variable capacitor corresponding to the varactor diode 12.

Next, when the resonance frequency of the antenna 1 is shifted from the transmission frequency 17 to the reception frequency 18, the control signal voltage is lowered and the PIN diode 8 is turned off. FIG. 4B shows an equivalent circuit at this time. FIG.
In (b), the coil 7 is inserted in series with the antenna 1, and the resonance frequency of the antenna 1 is reduced. The value of the inductance of the coil 7 must be appropriately selected so that the resonance frequency of the antenna 1 is switched between the transmission frequency band 6 and the reception frequency band 5 by changing the ON / OFF state of the PIN diode 8.

Next, a case where the resonance frequency of the antenna 1 is finely adjusted will be described. Regardless of whether the resonance frequency of the antenna 1 is in the reception frequency band 5 or the transmission frequency band 6, fine adjustment of the resonance frequency is performed by the capacitance changing circuit 3.
This is performed using Generally, the value of the capacitance of the varactor diode 12 changes continuously with respect to the applied voltage. The control signal voltage is applied to the varactor diode 12 from the terminal 13 through the choke coil 10 to control the capacitance of the varactor diode. I do. As shown in FIG. 3, when the resonance frequency of the antenna 1 is shifted to the higher one 19, the control signal voltage is increased to the varactor diode 12 and the capacitance value is decreased. Conversely, when the resonance frequency of the antenna 1 is lower 20, the control signal voltage applied to the varactor diode 12 is reduced, and the capacitance of the varactor diode 12 is increased. Thus, the varactor diode 1 is controlled by the control signal voltage.
The resonance frequency of the antenna 1 is finely adjusted by changing the capacitance of the antenna 2.

(Embodiment 2) FIG. 5 is a circuit diagram of a frequency sharing antenna for superposing a control signal voltage on a feeder according to Embodiment 2 of the present invention. In FIG. 5, 1 is an antenna, 7 is a coil used in an inductance changing circuit,
Reference numeral 8 denotes a PIN diode used as a switch for changing the value of inductance, reference numeral 9 denotes a terminal for applying a control signal voltage to the PIN diode 8, and reference numeral 10 denotes a control signal voltage of high-frequency power supplied to the antenna 1. A choke coil 15 for suppressing leakage to the terminal 9 and the ground 11 is a transmitting / receiving circuit.

In FIG. 5, a high-frequency output signal transmitted from the transmission / reception circuit 15 is supplied to the antenna 1 through the antenna feed line 4. Fig. 3 shows the resonance frequency of the antenna 1.
When moving to the middle transmission frequency band 6, a control voltage is applied to the terminal 9 and the PIN diode 8 is turned on. Thereby, the coil in the inductance changing circuit 2 is short-circuited, and the resonance frequency of the antenna 1 increases. Conversely, in order to shift the resonance frequency of the antenna 1 to the reception frequency band 5 in FIG. 3, the control voltage applied to the terminal 9 is reduced so that the PIN diode 8 in the inductance changing circuit 2 is turned off. . As a result, the coil 7 is inserted in series with the antenna 1, and the resonance frequency of the antenna 1 decreases. The value of the inductance of the coil 7 must be set so that the transmission frequency band 6 and the reception frequency band 5 can be switched by turning on / off the PIN diode 8.

As described above, the PIN signal is transmitted through the choke coil 10 for blocking high frequency components by the transmission / reception control signal voltage.
In this configuration, the switching of the diode 8 is controlled to switch the resonance frequency between the transmission and reception frequency bands 5 and 6.

[0018]

As described above, according to the present invention, in a frequency sharing antenna for electrically controlling a resonance frequency,
Broadband frequency characteristics required for a communication system in which transmission and reception frequencies are far apart can be realized. Further, the size of the entire antenna device can be reduced, which is effective in reducing the size of the mobile communication terminal.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a frequency sharing antenna according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of the frequency sharing antenna according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram of a transmission / reception frequency band according to the first embodiment of the present invention.

FIG. 4 is an equivalent circuit diagram of a frequency sharing antenna for explaining a change in resonance frequency caused by the inductance changing circuit according to the first embodiment of the present invention;

FIG. 5 is a circuit diagram of a frequency sharing antenna for superimposing a control signal voltage on a power supply line according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional antenna device that changes a resonance frequency.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 antenna 2 inductance changing circuit 3 capacitance changing circuit 4 antenna feed line 5 reception frequency band 6 transmission frequency band 7 coil 8 PIN diode 10 choke coil 11 ground 12 varactor diode 15 transmission / reception circuit 16 variable capacitor 17 transmission frequency 18 reception frequency

Claims (2)

[Claims] An inductance changing circuit is provided in series with the antenna to control a large change in the resonance frequency of the antenna, and a capacitance changing circuit is provided in parallel with the antenna to fine-tune the resonance frequency of the antenna. A frequency sharing antenna characterized in that a circuit and a capacitance changing circuit are operated by a control signal voltage. 2. The frequency sharing antenna according to claim 1, wherein a control signal voltage of said inductance changing circuit is superimposed on a feed line for the antenna.