JPS61135235A - Antenna system - Google Patents

Abstract

PURPOSE:To minimize the reduction of a reception input level by controlling a variable reactance element of an impedance matching circuit set between an antenna and a receiver so as to secure the maximum input level of the receiver. CONSTITUTION:The received wave is applied to a receiver 3 via an antenna 1 and an impedance matching circuit 2 containing a variable reactance element like a variable capacity diode, etc. to undergo conversion, amplification, etc. of frequency. Then a signal corresponding to the input level of the receiver 3 is extracted through a terminal RSSi and converted into a digital signal by an A/D converter 4 to be applied to a logical circuit 5. The circuit 5 changes the bias voltage which is applied to variable capacity diodes 2-6 and 2-1 via D/A converters 1 and 6 and controls the bias voltage so that the output level of the terminal RSSi of the receiver 3 is maximum. Thus the reduction of the received input level is minimized to avoid a call unable state even in case a human body, etc. get close to the antenna 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in the antenna system of a mobile radio receiver, for example, a portable receiver used at frequencies above the VIP band.

In recent years, portable receivers in the VHF-11HF band have been widely used, but the antenna system used in these receivers is affected by the influence of nearby human bodies and external objects, which causes the antenna impedance to change significantly. , the matching with the receiver may be disrupted and the reception level may drop significantly, making it impossible to make calls.

Therefore, there is a need for an antenna system that is less likely to cause such a situation.

[Conventional technology]

In general, % wavelength sleeve antennas, A wavelength whip antennas, or loop antennas are used as antennas for portable receivers, but the antenna impedance of these antennas is significantly affected by nearby human bodies and objects. Changes to

For this reason, an impedance matching circuit inserted between the receiver and the antenna is unable to match the antenna impedance and the receiver input impedance, resulting in a significant drop in the reception input level.

[Problem that the invention seeks to solve]

As explained above, a large change in antenna impedance caused by the influence of a human body, etc. near the antenna causes a large impedance mismatch between the antenna and the receiver, which significantly reduces the reception level. There was a problem in that it was sometimes impossible to talk to the other station.

[Means for solving problems]

The above problems are solved by the antenna system of the present invention, which controls the reactance value of the variable reactance element inserted in the impedance matching circuit so that the input level to the receiver is maximized.

[Effect]

The present invention provides an impedance matching circuit that automatically absorbs changes in antenna impedance caused by a human body coming close to the antenna, thereby preventing a decrease in the reception power level.

That is, conventional impedance matching circuits cannot absorb changes in antenna impedance because it is difficult to re-match between the antenna and the receiver in response to changes in antenna impedance.

However, in the impedance matching circuit of the present invention, a variable reactance element is inserted and the actance value of the variable reactance element is controlled so that the reception level is maximized.

Therefore, it is possible to minimize the drop in level due to impedance mismatch between the antenna and receiver.
Unable to make calls will almost disappear.

〔Example〕

The gist of the present invention will be specifically explained below with reference to illustrated examples. Note that the same reference numerals indicate the same objects throughout the figures.

FIG. 1 shows a block diagram of one embodiment of the present invention, and FIG. 2 shows a system operation flow diagram.

In FIG. 1, received waves are received from antenna 1. The signal is applied to the receiver 3 via, for example, a π-type impedance matching circuit 2 that includes a variable reactance element (for example, a variable capacitance diode).

This received wave is subjected to processing such as frequency conversion and amplification in the receiver 3, but a signal corresponding to the receiver input level [for example, AGC of an intermediate frequency amplifier with AGC (not shown) in the receiver
A signal obtained by linearizing the @ pressure through a logarithmic amplifier (not shown) is taken out from the terminal R3Si, digitized by the analog/digital conversion circuit 4, and applied to the logic circuit 5.

The logic circuit 5 first determines the voltage applied to the variable capacitance diode 2-1 in the impedance matching circuit 2 according to the system operation flow shown in FIG. 2 in the following procedure. , ■ Initial voltage V on variable capacitance diodes 2-1 and 2-2
ol and Vo2 are applied, and the level of terminal R5S i is measured.

■ Vol voltage only increases by ΔVo1 and terminal R
Measure the level of 5S i and compare with the previous value. At this time, if it is increasing, repeat this.

・If it falls below the previous value, reverse the polarity of ΔVol and set Vo
Apply and repeat.

・If it is maximum, fix the Vol.

Now that the bias voltage of the variable capacitance diode 2-1 has been optimally set, next, the optimal bias voltage of the variable capacitance diode 2-2 is determined using the same procedure.

Note that when a variable capacitance diode is used as the variable reactance element, it is possible to electronically cover more than 90% of the area on the Smith chart.

Furthermore, digital/analog conversion circuits 6 and 7 are used to convert the digital output from the logic circuit 5 into a bias voltage for the variable capacitance diode.

FIG. 3 shows a block diagram of another embodiment of the invention.

As shown in the figure, the AGC voltage from the terminal R5Si is amplified by the DC amplifier 8 without being converted into a digital signal, and the AGC voltage from the terminal R5Si is amplified by the DC amplifier 8.
The bias voltage of the variable capacitance diode 2-1 is controlled so that the level from Si is maximized.

In this case, it is also possible to connect a variable capacitance diode in series with the capacitor 2-3 and control the bias voltage of the two variable capacitance diodes using the output voltage of the DC amplifier 8.

〔Effect of the invention〕

As explained in detail above, even if the antenna of a portable receiver is installed near the human body, it can almost match the input impedance of the receiver, so the drop in the received input level is minimized. This has the effect of almost eliminating the possibility of being blocked and unable to make a call.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the present invention, Figure 2 shows the operation flow of the present invention. FIG. 3 shows another block diagram of the invention. In the figure, ■ is antenna, 2 is an impedance matching circuit, 3 is the receiver, 4 is an analog/digital conversion circuit; 5 indicates a logic circuit. grass cause Grass 3 @

Claims (1)

[Claims] In a receiving system including an antenna, an impedance matching circuit for impedance matching between the antenna and the receiver, and the receiver, a variable reactance is inserted into the impedance matching circuit so that the input level to the receiver is maximized. An antenna system characterized by controlling the reactance value of an element.