JPH0248832A - Antenna tuning circuit and individual selective call receiver using the same - Google Patents

Abstract

PURPOSE:To realize antenna turning in the best state automatically without the need of reducing the Q of the antenna by constituting a variable condenser of an antenna tuning circuit with a varactor diode and controlling the condenser with a signal from a PLL local oscillation circuit. CONSTITUTION:A signal of a frequency component different from a desired frequency corresponding to a digital signal of a signal line 17 by just an intermediate frequency is outputted from a signal line 15 and a voltage corresponding to the frequency of the line 15 is generated in the line 9. Since a varactor diode is used for a VCO 61 to vary the oscillated frequency, the circuit has only to be controlled by taking the case into account in such a way that the voltage of the line 9 is higher when the frequency of the line 15 is high and when the frequency is low, the voltage is lower. That is, the voltage of the line 9 is amplified properly by a buffer amplifier 7 and given to the varactor diode 111, then an optimum tuning condenser is obtained from the diode 111. Thus, the voltage from a PLL local oscillator 6 is given to the diode 111 to obtain a condensor in response to each radio frequency.

Description

[Detailed Description of the Invention] [Industrial Application Fields] The present invention uses a voltage controlled oscillator (hereinafter referred to as V
Regarding antenna tuning circuits that are inserted between high-frequency circuits and antennas and matched so that high-frequency power is efficiently transmitted in wireless communication equipment that has wireless communication equipment (referred to as CO), variable capacitance diodes are particularly used as tuning variable capacitors. The present invention relates to an antenna tuning circuit using the antenna tuning circuit and an individual selective call receiver having the same.

[Prior Art] Conventionally, as shown in FIG. 6, this type of antenna tuning circuit uses a variable capacitor or a semi-fixed capacitor (trimmer capacitor) as a variable capacitor 11 for antenna tuning, and is manually adjusted. was doing.

The antenna tuning circuit 1' converts the high frequency current flowing from the antenna 2 to the ground terminal 3 to the high frequency transformer 13 and the variable capacitor 11. The capacitor 14 efficiently transmits the signal to the high frequency amplifier circuit 4.

[Problems to be Solved by the Invention] However, in the conventional antenna tuning circuit described above, the adjustment of the variable capacitor 11 must be manually re-adjusted each time the radio frequency for tuning changes, which is a hassle. was occurring. It is also conceivable to lower the Q of the antenna to reduce the influence of poor tuning and omit the adjustment, but this has the drawback of lowering the overall efficiency.

By the way, individual selective calling receivers usually receive only one frequency and can only be used in one service area.In order to use them in service areas in other areas, you must carry multiple receivers. There was a need.

On the other hand, in order to be able to receive a plurality of frequencies with one receiver, it is conceivable to use PLL synthesizer technology and use this as a local oscillation circuit to perform frequency switching.

However, in such a multi-frequency individual selective call receiver, the circuit becomes complicated and the battery capacity increases, resulting in an increase in the size of the entire device, which is inconvenient for the person carrying the receiver.

In order to solve this problem, only the PLL synthesizer section can be separated so that normally only one wave can be received, but multi-frequency reception can be performed only when used in other areas, so that the user can detach the PLL synthesizer section as needed. Just install a PLL synthesizer section.

In any case, the multi-frequency individual selective calling receiver described above receives a large number of frequencies, so a variable tuning circuit between the antenna and the input of the receiver is required, and the tuning is optimal depending on the receiving frequency. You must do so.

The technical problem of the present invention is to
The object is to be able to achieve the best tuning state at each frequency and to automatically adjust the tuning of the antenna without human intervention.

Another object of the present invention is to provide an individual selective calling receiver capable of receiving a plurality of frequencies by having an automatic antenna tuning function.

[Means for Solving the Problems] In the present invention, the tuning variable capacitor is composed of a variable capacitance diode, and as a means for generating a control voltage for capacitance adjustment to the variable capacitance diode, oscillation is applied to vCO in the PLL circuit. It is characterized by using a voltage applied for frequency control, and can be applied to both receivers and transmitters.

Further, according to the present invention, an external device having a PLL circuit including a vCO is removably attached to the receiver body, and when the receiver body and the external device are electrically connected, the vCO in the external device is There is obtained an individual selective paging receiver characterized in that it has means for automatically adjusting the tuning frequency of the antenna tuning circuit in accordance with the control voltage.

[Function] The antenna tuning circuit of the present invention uses a voltage given to vCO for controlling the oscillation frequency. That is, by focusing on the fact that the voltage applied to vCO changes depending on the radio frequency, and applying the changing voltage to the variable capacitance diode, a tuning capacitance corresponding to each radio frequency can be obtained.

[Embodiment] FIG. 1 shows a first embodiment of a receiver having an antenna tuning circuit according to the present invention. The antenna tuning circuit 1 includes a variable capacitance diode 111, a capacitor 12.degree. 14, and a high frequency transformer 13. 5 is a frequency mixing circuit including a bandpass filter, and 6 is a PLL local oscillation circuit. The operation of the PLL local oscillation circuit 6 is as follows. First, the output signal of the variable frequency divider circuit 62 and the output signal of the reference oscillator 63 are connected to the phase comparator 6.
4. Compare the phases. These error signals are filtered through a low-pass filter 6.
The oscillation frequency of C061 is adjusted by the voltage obtained through VCO6 so that the error signal is always constant.
Controls the oscillation frequency of 1.

Further, since the variable frequency divider circuit 62 can change its frequency division ratio according to the digital signal given from the signal line 17, the oscillation output of the frequency corresponding to the digital signal on the signal line 17 is supplied to the signal line 15 as a reference. Stability almost equivalent to that of the oscillator 63 can be obtained.

It is now assumed that the high frequency current flowing from the antenna 2 to the ground terminal 3 is efficiently transmitted to the high frequency amplification circuit 4 by the antenna tuning circuit 1. For this purpose, the antenna tuning circuit 1 must be adjusted to the best condition for the desired frequency. That is, when the frequency is higher, the capacitance value of the variable capacitance diode 111 is lower, and therefore the voltage on the line 8 is higher; when the frequency is lower, the capacitance value of the variable capacitance diode 111 is higher, and therefore the voltage on the line 8 is higher.
voltage must be lower.

In FIG. 1, the voltage on line 8 is derived from the output voltage on line 9 of low-pass filter 65 through buffer amplifier 7. The buffer amplifier 7 serves as a buffer to prevent the antenna tuning circuit 1 and the PLL local oscillation circuit 6 from influencing each other, and also to amplify or attenuate changes in the voltage level of the line 9 to increase the capacitance of the variable capacitance diode 111. [It has the role of bringing the system to a convenient level.]

The high frequency amplification circuit 4, the frequency mixing circuit 5, and the PLL local oscillation circuit 6 perform so-called heterodyne detection, and the signal line 10 receives only signals of desired frequency components from the radio waves received from the antenna 2. It is selected and amplified by the antenna tuning circuit 1 and the high frequency amplification circuit 4 and output.

Further, a signal having a frequency component different from that of the signal line 10 by an intermediate frequency is outputted to the signal line 15, and furthermore, the signal of the signal line 10 and the signal of the signal line 1 are outputted by the frequency mixing circuit 5.
5 are frequency-mixed, and only the intermediate frequency component is selectively output to the output line 16.

As mentioned above, by outputting from the signal line 15 a signal with a frequency component that differs from the desired frequency corresponding to the digital signal on the signal line 17 by exactly the intermediate frequency, the signal on the line 9 corresponds to the frequency of the signal line 15. This means that a certain voltage is generated. Therefore, usually ■C0
61 uses a variable capacitance diode to change the oscillation frequency, so considering that case, signal line 1
When the frequency of 5 is higher, the voltage of line 9 is higher;
When the frequency of signal line 15 is lower, the voltage on line 9 is output lower. Therefore, the voltage on the line 9 is appropriately amplified by the buffer amplifier 7, and the voltage on the line 9 is amplified by the buffer amplifier 7.
11, the variable capacitance diode 111 can always obtain the optimum tuning capacitance value corresponding to the desired frequency.

It should be noted that a digital signal for setting a frequency division number to vary the oscillation frequency is input to the PLL local oscillation circuit 6. By applying a voltage obtained by digital-to-analog conversion of this digital signal to the variable capacitance diode 111, a tuning capacitance corresponding to each radio frequency can be obtained.

An example will be explained below with reference to FIG.

FIG. 2 shows a second embodiment of the invention. The same parts as in FIG. 1 are given the same numbers. The difference from the embodiment shown in FIG. 1 is that as a means for obtaining the output voltage of the line 8, the digital signal of the signal line 17 is converted into an analog signal of a level convenient for adjusting the capacitance of the variable capacitance diode 111 by a digital-to-analog conversion circuit 18. The point is that it is being converted. Since the signal on the signal line 17 corresponds to the desired frequency, by appropriately converting it in the digital-to-analog conversion circuit 18, the signal on the line 8 is converted to a signal on the same principle as explained in the embodiment of FIG. can generate voltage for antenna tuning.

Although the above explanation was based on the embodiment of a receiver, it goes without saying that the present invention can also be applied to a transmitter having a PLL oscillator based on the same principle.

A third embodiment of the present invention will be described with reference to FIGS. 3 to 5. In this embodiment, the above-described antenna tuning circuit is applied to an individual selective calling receiver.

FIG. 3 is a block diagram schematically showing an individual selective calling receiver according to the present invention.

The high frequency signal received by the antenna 21 is transmitted to the tuning circuit 22.
The impedance is matched to the RF amplifying section 23. The signal amplified by the RF amplifier section 23 is lowered in frequency by a local oscillator signal in the mixing circuit 24, further passes through the IF amplifier section 25, is converted into a digital calling signal by the detection/waveform shaping section 26, and is subjected to signal processing. Ru.

Here, in the case of single-frequency reception, that is, when using the receiver without connecting the external accessory device described later,
The switch SW1 is connected to the crystal local oscillator 27. Further, the switch SW2 is in an OFF state, and the tuning circuit 22
is tuned at the frequency of single-frequency reception.

Next, when an external accessory is connected, switch SW
1 switches to the PLL synthesizer section 28. moreover,
The switch SW2 is turned on, and the tuning circuit 22 is controlled by the PLL synthesizer section 28.

FIG. 4 is an external view of the individual selective calling receiver.

21 is an antenna of the receiver, 41 is an external accessory device of the individual selective calling receiver, and 42 is a connector for connecting the receiver main body and the external accessory device 41.

FIG. 5 is a block diagram of an individual selective call receiver according to the present invention. A broken line portion 100 is the receiver body. antenna 2
The tuning circuit No. 1 is composed of a varactor 31 as a variable capacitance diode, and capacitors CI, C2, and C3. Variation of the tuning frequency of the tuning circuit is achieved by varying the voltage applied to the varactor 31.

When using the individual selective call receiver as a standalone unit,
The voltage of the receiver power supply 32 is made constant by a constant voltage circuit 33,
It is applied to the varactor 31 through the variable resistor vR1 and the first switching circuit 34.

The switching circuit 34 is always ON when the individual selective calling receiver is used as a standalone unit.
Tuning of the antenna 21 is achieved by adjusting the variable resistor VR1 in advance.

The second switching circuit 35 performs switching of the power supply of the crystal station oscillator circuit 36. When the individual selective call receiver is used alone, the second switching circuit 35 is turned on, and the output of the crystal local oscillation circuit 36 is injected into the mixing circuit 24 as the local oscillation frequency through the capacitor C4.

The broken line part 200 is an external accessory device, and the PLL circuit is the first
As in the figure, VCO 51, variable frequency divider circuit 52, reference oscillator 5
3, a phase comparator 54, and a low-pass filter 55. By controlling the frequency division number of the variable frequency divider circuit 52 by the PLL control unit 56, the output frequency of the VCO 51 can be set to a desired oscillation frequency.

Now, when the external accessory device 200 is connected to the receiver body 100, electrical connection is made through the connector 42. In this case, the connector contact 42b is grounded and the first . The second switching circuits 34 and 35 are turned off. At this time, the DC voltage output from the low-pass filter 55 is applied as the voltage for controlling the tuning circuit of the antenna 21 through the connector contact 42a. The DC voltage of the low-pass filter 55 is proportional to the oscillation frequency of the VCO 51, and the VCO
The buffer amplifier 57 operates so that the characteristics of the relationship between the input voltage and the oscillation frequency match the tuning characteristics of the antenna 21.

On the other hand, the output of the VCO 51 is amplified by the buffer amplifier 58 and is injected into the mixing circuit 24 through the connector contact 42C and the capacitor C5. The connector contact 42d is for bringing the receiving main body 100 and the external accessory device 200 to the same ground potential.

As explained above, in this embodiment, a varactor is used in the antenna tuning circuit of the individual selective calling receiver to enable external voltage control of the tuning frequency, so that the optimal antenna can be adjusted according to changes in the local oscillation frequency. You can get synchronization. This allows the individual selective calling receiver to be used in one service area or in another service area as required.

In the third embodiment, the receiver main body 100 and the external accessory device 200 are separable, but the present invention incorporates the circuit inside the external accessory device 200 into the receiver main body 100. may also be applied.

[Effects of the Invention] As explained above, the present invention configures the variable capacitor of the antenna tuning circuit with a variable capacitance diode, and the capacitance is
By controlling the signal using the L local oscillator circuit, it is now possible to reduce the Q of the antenna without having to manually tune the antenna, which was previously done manually every time the frequency changed. This has the effect that antenna tuning can be performed automatically under the best conditions without the need for tuning.

Further, the individual selective calling receiver according to the present invention can be used in service areas of other regions and can automatically perform antenna tuning.

Ground terminal, 4... High frequency amplifier circuit, 5... Frequency mixing circuit, 6... PLL local oscillation circuit, 7... Buffer amplifier, 111... Variable capacitance diode.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of a receiver having an antenna tuning circuit according to the present invention, FIG. 2 shows a second embodiment of a receiver having an antenna tuning circuit according to the present invention, and FIG. A schematic configuration diagram applied to an individual selective calling receiver, FIG. 4 is an external view showing the individual selective calling receiver used in the present invention and an external accessory device in a separated state, and FIG. 5 is a schematic diagram of the individual selective calling receiver according to the present invention. A block diagram of a paging receiver and external auxiliary equipment, FIG. 6 is an example of a receiver having a conventional antenna tuning circuit. 1...Antenna tuning circuit, 2...Antenna, 3...
・Contact figure 4

Claims (1)

[Claims] 1. In the antenna tuning circuit, the tuning variable capacitor is composed of a variable capacitance diode, and as a means for generating a control voltage for capacitance adjustment to the variable capacitance diode, a PLL circuit is used for controlling the oscillation frequency. An antenna tuning circuit characterized in that an antenna can be automatically tuned by using a signal given to the antenna. 2. In an individual selective calling receiver having an antenna tuning circuit, when an external device having a PLL circuit including a voltage controlled oscillator is removably attached to the receiver body, and the receiver body and the external device are electrically connected. . An individual selective paging receiver comprising means for automatically adjusting the tuning frequency of the antenna tuning circuit in accordance with a control voltage of a voltage controlled oscillator in the external device.