JP2758712B2 - Radio selective call receiver - Google Patents

Abstract

PURPOSE:To automatically adjust an antenna tuning section to the best state in accordance with a receiving frequency by detecting the level of a radio call signal on the poststage side of the antenna tuning section and deciding the control signal to be given to the element of the antenna tuning section so that the level of the radio call signal can become the highest. CONSTITUTION:A series circuit composed of a fixed capacitor 201 and variable- capacity capacitor 203 is connected between one end of an antenna 1 and ground and a fixed capacitor 202 is connected between the other end of the antenna 1 and the input of a radio section 3. An antenna tuning section 2 is constituted by connecting a parallel circuit of three variable-capacity capacitors 204-206 between the connecting point of the capacitor 202 and antenna 1 and ground. When antenna tuning is not obtained against a receiving frequency, the output level of the section 3 becomes lower. In such a state, an output controlling section 16 adjusts the voltage applied across varactor diodes 203-206 by controlling transfer gates 109-113 so that the best tuned point can be obtained against the receiving frequency.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio selective calling receiver, and more particularly, to a radio selective calling receiver having a function of automatically adjusting an antenna tuning section to the best condition.

[Conventional technology]

The conventional radio selective call receiver has a configuration as shown in FIG. In this radio selective paging receiver, a radio paging signal is received by an antenna 1 and tuned and impedance-matched by an antenna tuning section 2 composed of fixed capacitors 210 to 212 and a variable capacitor 213, and then the radio section 3 Amplification and local oscillator 4
Performs a frequency conversion by mixing with the local oscillating frequency signal to generate an IF frequency signal. The IF frequency signal is amplitude-limited by the limiter 5 and DC-detected by the discriminator 6. When the level of the radio call signal is low, since there is much noise, the output of the discrimination 6 is passed through a low-pass filter (LPF) 7, the waveform is shaped by a comparator 8 and sent to a signal control unit 9. When a call signal is received, the signal control unit 9 establishes bit synchronization and frame synchronization by detecting a synchronization signal, and thereafter sets an individual call signal and its own call number stored in the individual number storage unit 10 in advance. Are compared with each other, and when they match, it is determined that the call is its own call, and the fact that there is a call from the speaker 11 is notified.

[Problems to be solved by the invention]

As described above, the conventional radio selective calling receiver includes the variable capacitor 213 in the components of the antenna tuning unit 2. Conventionally, an antenna adjustment step is provided in the process of manufacturing or repairing the receiver, and the work of adjusting the capacity of the variable capacitor 213 is performed using various measuring devices and the like. This is to optimize the reception sensitivity at a specific reception frequency, but this antenna adjustment step has contributed to an increase in receiver manufacturing cost.

In addition, this type of radio selective calling receiver often uses a superheterodyne system, and the reception frequency can be changed by changing the oscillation frequency of the local oscillator 4. However, when the reception frequency is changed, the conventional radio selective calling receiver needs to re-adjust the antenna tuning unit 2 in accordance with the change, and the same problem as described above occurs.

The present invention has solved such a conventional problem.
An object of the present invention is to provide a radio selective call receiver having a function of automatically adjusting an antenna tuning section to an optimum state according to a reception frequency of a radio call signal.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a radio selective paging receiver that performs paging notification by receiving a radio paging signal including a paging number assigned to itself in advance. An antenna tuning unit, which is connected between a radio unit that amplifies a paging signal and includes an element whose electrical characteristics change according to a control signal, and a radio paging signal is received by a radio selective paging receiver A signal control unit that alternately generates a first clock and a second clock; a preamplifier that amplifies a radio call signal output from the radio unit; and an output of the preamplifier to a DC signal. An AC-DC converter for converting, a hold unit for holding an output level of the AC-DC converter in synchronization with the first clock, a reference potential generator, A series circuit of bleeder resistors that divides a reference potential supplied from the reference potential generation unit by resistance and generates reference voltages having different values, an output of the hold unit is input to one input, and the other input is A level detector for converting the output level of the hold unit into a digital signal having a number of bits equal to the number of the comparators, comprising a plurality of comparators to which respective different reference voltages generated by a series circuit of the bleeder resistors are input; A series circuit of a bleeder resistor that divides a reference potential supplied from the reference potential generating section by resistance to generate control signals having different values, and a plurality of types of control signals generated by the series circuit of the bleeder resistor. A control signal generation unit including a plurality of transfer gates for selecting one control signal from the control signal; The control signal applied to the element of the antenna tuning unit is changed by changing the on / off state of the plurality of transfer gates in synchronization with the second clock, and the maximum level radio paging signal is detected by the level detection unit. And output control means for determining a control signal to be detected and thereafter continuously applying the control signal to the element.

A detection unit for detecting an oscillation frequency of a local oscillator connected to the radio unit; a value of a control signal at a start of sweeping in the output control unit according to the oscillation frequency of the local oscillator detected by the detection unit; Is changed.

[Action]

In the radio selective calling receiver of the present invention, when the radio paging signal is received by the antenna, the signal control unit generates the first clock and the second clock alternately.
Each time the first clock is generated, the hold unit holds the output level of the AC-DC converter that converts the output of the preamplifier that amplifies the radio call signal output from the radio unit to a DC signal, Level detection means converts the output level of the hold section into a digital signal having a plurality of bits.
On the other hand, each time the second clock is generated, the output control means changes the on / off state of the plurality of transfer gates in the control signal generation section to change the control signal given to the elements of the antenna tuning section. Then, the level detection means determines a control signal at which the maximum level of the radio call signal is detected, and thereafter continuously applies the control signal to the element.

Further, when the detecting means detects the oscillation frequency of the local oscillator connected to the radio unit, the value of the control signal at the time of starting the sweep in the output control means is changed according to the detected oscillation frequency of the local oscillator.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. In FIG. 1, a radio calling signal received by an antenna 1 is supplied to a radio unit 3 via an antenna tuning unit 2. The wireless unit 3 amplifies the input wireless calling signal and performs frequency conversion by mixing with the local oscillation frequency signal supplied from the local oscillator 4, and outputs, for example, an IF frequency signal of 455 kHz. The output of the radio unit 3 is sent to the limiter 5 and to the preamplifier 12. The limiter 5 amplifies and limits the amplitude of the input wireless calling signal, and outputs the amplified signal to the discriminator 6. The discriminator 6 performs FM detection on the amplitude-limited signal and sends the signal to a low-pass filter (LPF) 7 as a calling signal. The low-pass filter 7 removes the noise component from the calling signal, and the signal is shaped by the next comparator 8 and then sent to the signal control unit 9. The signal control unit 9 establishes synchronization by a synchronization signal of the call signal,
Performs a comparison and comparison between the individual call signal following the synchronization signal and the call number stored in advance in the individual number storage unit 10,
When both match, it is determined that the call is its own, and the speaker 11 notifies that the call has been made.

Next, an automatic tuning function of antenna tuning according to the present embodiment will be described.

The input stage of the radio unit 3 is usually a high-frequency amplifier circuit using transistors, and the input impedance is capacitive. Therefore, the antenna 1 and the antenna tuning unit 2 make the impedance inductive and impedance matching is performed, and the signal received by the antenna 1 is most efficiently transmitted to the radio unit 3.
Synchronize so that you can input to. It is also desirable to be able to cover a relatively wide range of tuning points without exchanging elements, and to suppress the occurrence of component damage and poor adjustment by eliminating the need for mechanical adjustment. Therefore, in this embodiment, a series circuit of a fixed capacitor 201 and a variable capacitor 203 is connected between one end of the antenna 1 and the ground,
A fixed capacitor 202 is connected between the other end of the antenna and the input of the radio unit 3, and a parallel circuit of three variable capacitors 204 to 206 is connected between the fixed capacitor 202 and the connection point between the antenna 1 and the ground. The antenna tuning unit 2 is configured by being connected. A control voltage is applied to the cathodes of the variable capacitance diodes 203 to 206 as described later.

Normally, the input impedance of the input stage transistor of the wireless unit 3 changes depending on the reception frequency. In the conventional radio selective calling receiver shown in FIG. 6, the tuning point is adjusted by the variable capacitor 213 to optimize the sensitivity, and if it is not enough, the capacitance values of the capacitors 210 to 212 are changed. Thus, the tuning capacity and impedance at a desired frequency are secured. On the other hand, in this embodiment, the adjustment of the antenna tuning unit 2 is performed as follows.

In FIG. 1, an IF frequency signal output from a radio unit 3 is amplified by a preamplifier 12 having a wide dynamic range within a range not saturated, and is input to an AC-DC converter 13.
The AC signal input to the AC-DC converter 13 is rectified and smoothed and converted to a DC signal. This DC signal is supplied to the next-stage hold unit 14. The hold unit 14 temporarily holds and outputs the input DC signal in synchronization with the clock signal supplied from the signal control unit 9.

The voltage output from the hold unit 14 is input to the-input terminals of the comparators 101 to 104, respectively. Voltages Vs1 to Vs4 obtained by dividing the reference voltage output from the reference potential generator 15 by the bleeder resistors 105 to 108 are input to the + input terminals of the comparators 101 to 104, respectively. Comparator 101
.. 104 compare a voltage input to the-input terminal with a voltage input to the + input terminal, and output a 1-bit digital signal a having a logic "1" or a logic "0" according to the comparison result.
~ D is output. Then, digital signals “a, b, c, d” of a total of 4 bits output from the comparators 101 to 104 are sent to the output control unit 16. Here, each comparator 10
If the voltage applied to the-input terminal is higher than the voltage applied to the + input terminal, the outputs a to d are set to logic "1", otherwise, to logic "0", Vs1>Vs2>
Since there is a relationship of Vs3> Vs4, when a binary number (a, b, c, d) is considered, the magnitude of the value is the magnitude of the voltage output from the hold unit 14, that is, the frequency conversion appearing in the output of the radio unit 3. This corresponds to the level of the later radio call signal. In the present embodiment, the level of the radio calling signal is converted into 4-bit digital signals a to d as described above, but the number of bits is not limited to 4 bits and can be changed as necessary. is there.

The 4-bit digital signals a to d output from the comparators 101 to 104 are input to the output control unit 16 as described above. The output control unit 16 includes comparators 101 to 1
Transfer gates 109 to 113 according to the input signal from 04
The control signal for controlling ON / OFF of (TG1 to TG5)
The signal is output in synchronization with the clock supplied from the signal control unit 9.

The transfer gates 109 to 113 are supplied with voltages Vst1 to Vst5 obtained by dividing the reference potential output from the reference voltage generator 15 by bleeder resistors 114 to 118, respectively. Then, the on / off of each of the transfer gates 109 to 113 is controlled by a control signal from the output control unit 16, so that
A voltage corresponding to the control state is supplied to the variable capacitance diodes 203 to 206 of the antenna tuning unit 2. In this embodiment, five types of voltages Vst1 to Vst5 are used, but more voltages may be used if necessary.

Since the capacitance values of the variable capacitance diodes 203 to 206 change according to the voltage applied to the cathode side, the impedance of the antenna tuning unit 2 changes, and as a result, the output level of the radio unit 3 changes. Here, if the antenna is not tuned to the reception frequency, the output level of the radio unit 3 becomes small. In such a case, the output control unit 16 controls the transfer gates 109 to 113 to control the variable capacitance diodes 203 to 206.
Is adjusted so that the output of the radio unit 3 is maximized, that is, the best tuning point with respect to the reception frequency is obtained.

FIG. 2 is a flowchart showing a processing example of the output control unit 16 performing such an operation. Hereinafter, the operation of the automatic adjustment control of the antenna tuning unit 2 by the output control unit 16 will be described with reference to FIG.

After the radio selective calling receiver shown in FIG. 1 is turned on and each part becomes operable, when a radio calling signal is received by the antenna 1, the radio unit 3, the limiter 5, the discrimination 6, the low The band-pass filter 7, the comparator 8, and the signal control unit 9 perform the operations described above. At this time, the signal control section 9 detects the input signal, and thereby outputs the output control section 16.
The clock is supplied alternately to the
The control unit 16 causes the hold unit 14 to perform a predetermined operation while causing the hold unit 14 to perform a hold operation.

When the first clock is input, the output control unit 16
The transfer gates 109 and 110 are turned off, and the other transfer gates 111 to 113 are turned on (S1), so that the control voltage Vst3 is supplied to the antenna tuning unit 2. In this state, when the first clock is input from the signal control unit 9 to the hold unit 14, the DC voltage corresponding to the level of the radio calling signal when received by the antenna tuning unit 2 controlled by the control voltage Vst3. The output is held by the hold unit 14, and the output control unit 16 inputs a value obtained by converting the held value into a 4-bit binary number by the comparators 101 to 104 and stores it in the level storage area Y (S2). At this time, the control value (the content of the control that the transfer gates 109 and 110 are turned on and the others are turned off) is stored in the internal control value storage area CNY (S
2). In the initial state, the contents of the maximum level storage area MAX storing the value 0 are compared with the contents of the level storage area Y. If Y <MAX, the process proceeds to step S5, and from Y ≧ MAX to step S4. . Here, since the input level does not normally become zero, Y> MAX, and at the time of the first clock input, the output control unit 16 proceeds to step S4 to store the current input level and control value in the maximum level storage area MAX. The best control value storage area BST is transferred to the BST (the initial value of the best control value storage area BST is such that the transfer gates 109 and 110 are turned off and the others are turned on). Then, it waits for the next clock.

When the next clock is input from the signal control unit 9, the output control unit 16 also turns on the transfer gate 110 (S
1) The control voltage Vst2 is supplied to the antenna tuning unit 2. When the next clock is input from the signal control unit 9 to the hold unit 14 in this state, the level corresponds to the level of the radio paging signal received by the antenna tuning unit 2 controlled by the control voltage Vst2. The DC output is held by the hold unit 14, and the output control unit 16 inputs a 4-bit binary value corresponding to the hold value, stores it in the level storage area Y, and stores the control value at that time in the control value storage area.
Store it in CNY (S2). Then, a comparison is made with the previous input level stored in the maximum level storage area MAX, and the process proceeds to step S4 or S5 according to the comparison result. That is, if the determination result in step S3 is Y <MAX, the reception sensitivity of the radio calling signal is reduced by increasing the control voltage applied to the antenna tuning unit 2, that is, by decreasing the capacitance of the variable capacitance diodes 203 to 206. This means that the capacitance of the variable capacitance diodes 203 to 206 has to be increased in order to increase the receiving sensitivity, so the process proceeds to step S5. On the other hand, if the determination result in step S3 is Y ≧ MAX, the receiving sensitivity of the radio calling signal is increased by reducing the capacity of the variable capacitance diodes 203 to 206, and the variable capacitance diodes 203 to 206 If the capacity is reduced, the sensitivity may be further improved. Therefore, the process returns to step S1 to repeat the above operation. Then, when returning to step S1 and repeating the above-described operation, Y <MAX is determined in step S3 when the peak of the reception sensitivity has passed, so that the process proceeds to step S5 at that point.

In step S5, the output control unit 16 controls the transfer gates 109 to 113 to be sequentially turned off this time when the next clock is input from the signal control unit 9. For example, if the process proceeds to step S5 when the transfer gate 109 is turned on, the output control unit 16 turns off the transfer gate 109 and turns off the others in step S5. Then, in this state, when the next clock is input from the signal control unit 9 to the hold unit 14, the control voltage Vst2
The DC output corresponding to the level of the radio paging signal when received by the antenna tuning unit 2 controlled by the control unit is held by the hold unit 14, and the output control unit 16 outputs a 4-bit 2 bit corresponding to the hold value. The base value is input and stored in the level storage area Y, and the control value at that time is stored in the control value storage area CNY (S6). And the maximum level storage area M
The input level is compared with the input level stored in AX, and the process proceeds to step S8 or S9 according to the comparison result. That is, if the determination result in step S7 is Y <MAX, the reception sensitivity of the radio calling signal is reduced by reducing the control voltage applied to the antenna tuning unit 2, that is, by increasing the capacitance of the variable capacitance diodes 203 to 206. In this case, since the input level stored in the maximum level storage area MAX is considered to be the maximum input level, the best control value storage that stores the control value that can obtain the maximum input level Area BS
Control of the transfer gates 109 to 113 is continued thereafter according to the stored contents of T. As a result, the antenna tuning unit 2 is automatically adjusted to the best state, and that state is maintained thereafter.

On the other hand, if the determination result of step S7 is Y ≧ MAX,
By reducing the control voltage applied to the antenna tuning unit 2, that is, by increasing the capacity of the variable capacitance diodes 203 to 206, the reception sensitivity of the radio calling signal is increased, and furthermore, the capacitance of the variable capacitance diodes 203 to 206 is increased. Since there is a possibility that the sensitivity may be further improved if is increased, the process returns to step S5 to repeat the above operation. Then, when the above-described operation is repeated, it is determined that Y <MAX in step S7 at a point after the peak point of the reception sensitivity, and the process proceeds to step S9 at that point to perform the same operation as described above.

The automatic adjustment of the antenna tuning unit 2 by the output control unit 16 or the like described above does not need to be performed frequently, and may be performed once in the following cases.

At the time of manufacture and repair At the time of changing the reception frequency After the power of the receiver is turned on, it is optional to perform automatic adjustment at any time. For example, the automatic adjustment can be performed as follows.

(1) It is performed only once when the first wireless call signal is received after the power is turned on. For example, a flag that is reset at the time of turning on the power is provided in the signal control unit 9 or the output control unit 16, and if the flag is reset, the flag is set by performing automatic adjustment when the first radio call signal is received. It can be realized with a configuration that

(2) The receiver is provided with an instruction means such as an automatic adjustment start button, and when the automatic adjustment is instructed by the instruction means, the automatic adjustment is performed by receiving a radio call signal.

FIG. 3 is a block diagram of another embodiment of the present invention, in which the same reference numerals as in FIG. 1 denote the same parts, 17 is a frequency divider,
18 is an FV converter, and 19 is a reference potential controller.

In FIG. 3, a radio paging signal received by an antenna 1 is supplied to a radio unit 3 via an antenna tuning unit 2. The radio unit 3 amplifies the input radio calling signal and performs frequency conversion by mixing with the local oscillation frequency signal supplied from the local oscillator 4.
Outputs IF frequency signal. The output of the radio unit 3 is a limiter 5
And to the preamplifier 12. The configuration and operation of the stage after the limiter 5 and the stage after the amplifying unit 12 are the same as those in the embodiment shown in FIG.

In the present embodiment, the oscillation frequency signal of the local oscillator 4 is supplied to the radio unit 3 and to the frequency divider 17. Normally, the oscillation frequency signal is a high frequency signal of about several tens of MHz, so that the frequency divider 17 divides the frequency into a low frequency signal of about several tens KHz. The low-frequency signal after the frequency division naturally changes when the oscillation frequency of the local oscillator 4 changes. The divided frequency signal divided by the frequency divider 17 is input to the FV converter 18. The FV converter 18 outputs a DC voltage having a level corresponding to the input frequency-divided frequency signal. This DC voltage is supplied to the reference potential control unit 19. The reference potential control unit 19 uses the supplied DC voltage to
The setting of the reference voltage generated by the reference potential generator 15 is controlled. That is, the reference voltage is increased or decreased. Subsequent operations of the output control unit 16 and the like are the same as in the embodiment of FIG.

As described above, when the reference voltage generated by the reference potential generator 15 rises and falls, the control voltages Vst1 to Vst5 generated by the bleeder resistors 114 to 118 and the transfer gates 109 to 113 change up and down. Therefore, the output control unit 16 can change the control voltage (Vst3 in the above-described example) at the change (sweep) start point to the level expected in advance with respect to the change in the reception frequency. The control voltage can be determined.

In the present embodiment, the reference voltage generated by the reference potential generation unit 15 is raised and lowered to raise and lower the change start point of the control voltage. However, in the configuration of the bleeder resistors 114 to 118 and the transfer gates 109 to 113, control of a wide range If the voltage can be covered, the reference potential of the reference potential generation unit 15 is fixed, and the output control unit 16 changes the transfer start point, that is, the transfer gate that is turned on at the sweep start time, according to the output of the reference voltage control unit 19 You may do it.

In the present embodiment, when the reference voltage generated by the reference potential generation unit 15 rises or falls, the bleeder resistance 105
Although the reference voltages Vs1 to Vs4 on the side of .about.108 also change, the reference voltages Vs1 to Vs4 can be fixed.

FIG. 4 shows an example of the signal waveform of each part in the embodiment shown in FIGS. FIG.
Numeral 301 denotes an IF frequency output signal waveform of the radio unit 3, FIG.
Reference numeral 302 denotes a signal waveform amplified by the preamplifier 12. FIG. 3C shows a waveform 303 obtained by rectifying the AC signal in the AC-DC converter 13. The signal 303 is further smoothed and converted into a DC signal, and then input from the hold unit 14 to each of the comparators 101 to 104. The waveform is 304 in FIG.

In FIG. 3D, Vs1 to Vs4 indicate the reference voltage levels output from the reference potential generator 15 and divided by the bleeder resistors 105 to 108 and input to the comparators 101 to 104, respectively. In the embodiment, as described above, these reference voltage levels Vs1 to Vs4 change according to the change of the local oscillation frequency.

305 in FIG. 4E is the output waveform of the comparator 101, 306 in FIG. 4F is the output waveform of the comparator 102, 307 in FIG. 4G is the output waveform of the comparator 103, and FIG. Numerals 308 denote output waveforms of the comparator 104, respectively. In the previous embodiment, the output control unit 16 controls the maximum voltage to be applied to the variable capacitance diodes 203 to 206 when all of the outputs of the total of 4 bits of the comparators 101 to 104 are logic "1"("H"). Controls the transfer gates 109-113.

Reference numeral 309 in FIG. 3I indicates a voltage level applied to the variable capacitance diodes 203 to 206. Vst1 to Vst5 indicate voltage levels output from the reference potential generator 15 and input to the transfer gates 109 to 113 after voltage division by the bleeder resistors 114 to 118. In the embodiment of FIG. 3, as described above, these voltage levels Vst1 to Vst5 are changed by changing the local oscillation frequency.
Changes.

Reference numeral 310 in FIG. 4 (j) indicates a change in the capacitance value of the variable capacitance diodes 203 to 206 due to the application of a voltage to the cathode side. When the voltage is high, the capacity is small, and when the voltage is low, the capacity is large. Therefore, the tuning capacity of the antenna tuning section 2 is changed by the change of the voltage and the capacity, so that the optimum tuning and impedance matching conditions are obtained.

FIG. 5 shows a tuning state of the antenna tuning unit 2 according to the present invention. FIG. 7A shows the reception frequency in the initial state.
Indicates a state where synchronization is not achieved in F0. FIG. 11B shows a state where the capacitance of the variable capacitance diodes 203 to 206 is changed and tuning is achieved at the reception frequency F0. However, the output control unit 16 cannot determine at that time that the point shown in FIG. 3B is the best point, and further changes the capacity, so that the tuning is again shifted as shown in FIG. At that time, it can be determined that the state shown in FIG. 11B was the best, and the capacitance was changed in the opposite direction to the previous state.
Return to the state. This returned state is shown in FIG. 4D, and the tuning is best. Further, FIGS. 5 (e) and 5 (f) show a state in which the best tuning is always obtained according to the reception frequency even if the reception frequency changes to Fh or Fl.

The operation described above is performed instantaneously (for example, several msec to several tens msec) in order to follow the change of the tuning point.

〔The invention's effect〕

As described above, the radio selective calling receiver of the present invention configures an antenna tuning unit including an element such as a variable capacitance diode whose electric characteristics change according to a control signal,
The level of the radio paging signal is detected at the subsequent stage of the antenna tuning unit, and a control signal to be given to the element of the antenna tuning unit is determined so that this level becomes substantially maximum. Can be automatically adjusted to the best condition. For this reason, the antenna adjustment step in the manufacture or repair of the receiver can be eliminated, and the manufacturing cost of the receiver can be reduced. In addition, when the reception frequency changes, the antenna tuning unit is automatically adjusted to match the reception frequency. Therefore, even when the reception frequency is changed, manual adjustment of the antenna tuning unit is not required.
In particular, by detecting the oscillation frequency of the local oscillator and changing the starting point of the control signal sweep when the control means determines the optimum control signal, the optimum control signal can be determined even when the reception frequency greatly changes. Thus, the automatic adjustment of the antenna tuning unit adapted to the changed reception frequency can be performed reliably and promptly.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a flowchart showing a processing example of an output control unit 16, FIG. 3 is a block diagram of another embodiment of the present invention, and FIG. FIG. 5 is a diagram showing an example of a signal waveform of each unit in the embodiment of FIG. 5, FIG. 5 is a diagram showing various states of the antenna tuning unit 2, and FIG. 6 is a block diagram of a conventional radio selective calling receiver. In the figure, 1 ... antenna 2 ... antenna tuning unit 3 ... wireless unit 4 ... local oscillator 5 ... limiter 6 ... discrete 7 ... low-pass filter (LPF) 8 ... comparator 9 ... signal Control unit 10 Individual number storage unit 11 Speaker 12 Preamplifier unit 13 AC-DC conversion unit 14 Hold unit 15 Reference potential generation unit 16 Output control unit 17 Frequency Frequency divider 18 FV converter 19 Reference potential controller 101-104 Comparator 105-108, 114-118 Bleeder resistor 109-113 Transfer gate 201, 202 Fixed capacitor 203-206 Variable capacitance capacitor

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-48832 (JP, A) JP-A-60-12828 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04B 1/18-1/24 H04B 7/24-7/26 H04Q 7/06-7/38

Claims (2)

(57) [Claims] An antenna for receiving a radio call signal and a radio section for amplifying the radio call signal in a radio selective call receiver for performing a call notification by receiving a radio call signal including a call number assigned to the radio telephone in advance. And an antenna tuning unit configured to include an element whose electrical characteristics change according to a control signal, and a first clock and a first clock when a radio paging signal is received by the radio selective paging receiver. A signal control unit that alternately generates a second clock; a preamplifier that amplifies a radio call signal output from the radio unit; and an AC-DC converter that converts an output of the preamplifier to a DC signal. A holding unit that holds an output level of the AC-DC conversion unit in synchronization with the first clock; a reference potential generation unit; and a reference potential generation unit. And a series circuit of bleeder resistors for generating a reference voltage having a different value by dividing the reference potential to be generated, and an output of the hold unit is input to one input and generated by a series circuit of the bleeder resistance to the other input. A plurality of comparators to which different reference voltages are inputted, and a level detecting means for converting an output level of the hold unit into a digital signal having a bit number equal to the number of the comparators; and A series circuit of a bleeder resistor for generating control signals having different values by dividing the supplied reference potential by resistance, and selecting one control signal from a plurality of types of control signals generated by the series circuit of the bleeder resistors A control signal generation unit including a plurality of transfer gates for synchronizing with the second clock. Then, by changing the on / off state of the plurality of transfer gates, the control signal applied to the element of the antenna tuning unit is changed, and the control signal at which the maximum level radio call signal is detected by the level detecting means is changed. Output control means for determining and thereafter continuously applying the control signal to the element. 2. A control means for detecting an oscillation frequency of a local oscillator connected to the radio unit, wherein the output control means controls the start of sweeping in accordance with the oscillation frequency of the local oscillator detected by the detection means. The radio selective call receiver according to claim 1, further comprising a configuration for changing a signal value.