JPH0448827A - Radio selective calling receiver - Google Patents

Abstract

PURPOSE:To adjust the tuning state automatically by providing a varactor diode to adjust a tuning frequency to an antenna tuning circuit and applying variable control to a voltage fed to the varactor diode in response to an electric field strength of a radio calling signal to be received. CONSTITUTION:The caracitance of varactor diodes 221-223 is changed in response to the supplied voltage to them. As a result, the impedance of an antenna tuning section 2 is changed resulting that an output level of a radio section 3 is changed. For example, when an input level is decreased, a transfer gate is turned off to lower a voltage fed to the varactor diodes. Then the capacitance of the varactor diode is increased and the tuning point of the antenna tuning section 2 is optimized to maximize the input level. However, when the capacitance reaches too much, since the tuning point is deviated again, the level is decreased, This change point is discriminated and the transfer gate is controlled to optimize the tuning point again and the level is maintained thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to radio selective calling receivers, and more particularly to improvements in antenna tuning circuits.

[Conventional technology]

FIG. 5 shows an example of a conventional receiver of this type.

In the figure, a radio paging signal is received by an antenna 1, matched via an antenna tuning section 2, and then amplified and frequency converted by a radio section 3 to output an IF frequency.

The radio paging signal converted to an IF frequency is amplified and amplitude limited by a limiter 4, and DC detected by a discreet 5. Also, after being passed through a low pass filter (LPF) 6,
The waveform is shaped by the comparator 7 and sent to the signal control section 8.

The signal control unit 8 detects a synchronization signal from the received signal, establishes bit synchronization and frame synchronization, and compares the subsequent individual call signal with the call number stored in advance in the individual number storage unit 9. When it is determined that the call is for the user, the speaker 10 is sounded to notify the user of the call.

[Problem to be solved by the invention]

In the conventional receiver described above, it is necessary to adjust and tune the antenna tuning circuit 2 in order to obtain the best reception sensitivity. For this reason, capacitance such as a fixed capacitor 21 and a variable capacitor 23 that constitute the resonant circuit and the inductance that constitutes the antenna 1 are provided, and the variable capacitor 2
It is configured to achieve synchronization by adjusting 3.

However, adjustment of the variable capacitor 23 must be performed manually, which increases the manufacturing or repair process.
There is a problem in that it leads to an increase in costs. Furthermore, because the adjustment is performed mechanically using the variable capacitor 23, there is a problem that damage to parts, poor adjustment, etc. occur, and the reliability of the receiver deteriorates.

The object of the invention is to enable automatic tuning;
Another object of the present invention is to provide a receiver with improved reliability.

[Means to solve the problem]

The radio selective calling receiver of the present invention includes a variable capacitance diode for adjusting the tuning frequency in the antenna tuning circuit,
The voltage applied to the variable capacitance diode is controlled to vary depending on the electric field strength of the received radio paging signal.

The means for changing and controlling this voltage includes, for example, an AC-DC converter that converts the received radio paging signal into a DC voltage, a plurality of comparators that compare each of the converted DC voltages with different reference voltages, and a plurality of comparators that are prepared in advance. The transfer gate is composed of a plurality of transfer gates each capable of outputting different voltages, and an output control section that selectively operates the transfer gates according to the output of the comparator.

[Effect]

According to the present invention, by controlling the change in the voltage applied to the variable capacitance diode according to the electric field strength of the received signal, it is possible to automatically adjust the state where the electric field strength is maximum, that is, the tuning state. .

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and the same parts as in the conventional receiver shown in FIG. 5 are given the same reference numerals. Here, the antenna tuning circuit 2 is composed of two fixed capacitors 21 and a plurality of (three in this case) variable capacitance diodes 221, 222, 223 connected in parallel. In addition to the circuit shown in FIG. 5, there is also a preamplifier 11 that amplifies the output of the radio unit 3, an AC-DC converter I2 that converts the amplified AC signal into a DC signal, and a converted DC signal ( A hold unit 13 that holds a DC voltage at -, a reference voltage generator 14 that generates a reference voltage, and a plurality of (four in this case) comparators 15 that compare the held voltage with the reference voltage. 154, and a plurality of (five in this case) transfer gates 161-16. and the comparator 15. Transfer gates 16I-16. Output control section 17 that controls on/off
It is attached with.

In addition, 18I to 18. is comparator 15+ ~154
Leader resistors 191 to 1 for generating divided voltages of reference voltages for comparison from the reference voltages corresponding to the respective reference voltages;
9. are each of the above transfer games) 16. .about.165, respectively, and transfer gates 161 to 16. This is a bleeder resistor that divides and sets the voltage output from the

Next, the operation of the receiver with this configuration will be explained.

A signal received by antenna l is tuned by antenna tuning section 2 and then supplied to radio section 3. The radio unit 3 amplifies the input radio paging signal and converts the frequency to, for example, 4
Output as an IF frequency signal of 55KH2. The output of this radio section 3 is sent to a limiter 4 and also to a preamplifier section 11 at the same time.

The limiter 4 amplifies and limits the amplitude of the input IF frequency signal, and then outputs it to the disk drive 5. Disc 5 performs DC detection on the amplitude-limited IF frequency signal,
This is passed through the LPF 6 as a calling signal, and noise components are removed. Further, this calling signal is waveform-shaped by a comparator 7 and then sent to a signal control section 8. The signal control unit 8 establishes synchronization using the synchronization signal included in the calling signal, and after the synchronization signal (compares and checks the individual calling signal with the calling number pre-stored in the individual number storage unit 9, When it is determined that there is a call, the speaker 10 is sounded to notify that there is a call.

On the other hand, as shown in FIG. 2(a) to i), the IF frequency signal output from the wireless section 3 (FIG. 2(a)
)) is amplified by the preamplifier 11 with a wide dynamic range within a range that does not saturate (see figure (b)), and the AC-DC
The signal is input to the converter 12, where it is rectified and smoothed and converted into a DC signal ((C) in the same figure). This DC signal is supplied to the hold section 13 at the next stage. The hold section 13 temporarily holds the input DC signal and sequentially outputs it in accordance with the clock signal supplied from the signal control section 8.

The voltages temporarily held by the hold circuit 13 are input to comparators 15+ to 154, respectively. Comparators 15+ to 15. The reference voltage (2) is obtained by dividing the reference voltage output from the reference potential generation unit 14 by the bleeder resistors 181 to 184, 1°V 31 V S3 + V S
a is input, and the held voltages are compared with these reference voltages, here VSI>VSI>V
The relationship is S3>VSI.

As a result, comparators 151-15. Each output waveform is as shown in (d) to g) in the same figure.

Although the output is converted to 4 bits by four comparators here, the number of bits can be changed as necessary.

Each comparator 15. The 4-bit binary signal output from -154 is input to the output control section 17.

The output control unit 17 controls the transfer gates 16° to 16. A control signal for controlling is outputted using a clock supplied from the signal control section 8.

Transfer gate 16. ~16. The reference voltage output from the reference potential generator 14 is applied to the bleeder resistor 19. ~1
9. The voltages divided by the voltages are supplied respectively.

Each transfer gate 16. ~16. The ON/OFF state of the bleeder resistors 191 to 19. is controlled according to the operation thereof. each transfer gate 16. ~ Voltage input to 16s vs
□.

vsrz l vsti l VST41 VS
T5 ((h) in the same figure) is a variable capacitance diode 22. ．．
22□, 223.

Variable capacitance diode 22. ．． 222, 22. The capacitance value of the capacitor changes as shown in the figure (g) according to the supplied voltage. As a result, the impedance of the antenna tuning section 2 is changed, and the output level of the radio section 3 is accordingly changed. Therefore, on the contrary, it is possible to tune the antenna tuning section 2 based on the output level from the radio section 3.

That is, FIG. 3 shows a flowchart showing the operations of the output control section 17 and the antenna tuning section 2.

First, in the initial state, the output level of the wireless section 3, that is, the input level of the output control section 17 is low (Sl), so the output control section 17 tries to raise the level.

For example, a variable capacitance diode 22. It is assumed that the output level increases as the capacitance of 223 decreases. The output control section 17 turns on the first transfer gate 161.
2) Increase the voltage (reverse bias voltage) supplied to the variable capacitance diodes 22 and 223 (S3). As the reverse bias voltage increases, the capacitance value of the variable capacitance diode becomes smaller (S4) The output level of the radio section 3 becomes larger. In other words, the input level of the output control section 170 increases.

Thereafter, the same operation is repeated sequentially from the second transfer gate 16□ to further increase the input level of the output control section 17 (S5). The level is maximum at the best tuning point, but
If this operation is continued further, the level will become smaller because the synchronization will shift in the opposite direction.

When the input level becomes smaller, the transfer gate is turned off in the reverse order (S6), and the voltage supplied to the variable capacitance diode is lowered (S7).

Then, the capacitance value of the variable capacitance diode increases (S
8) The tuning point of the antenna tuning section 2 is the best and the input level is maximum. However, if the capacitance value becomes too large, the tuning point will shift again, and the level will become smaller. This change point is determined (S9), and the transfer gate is controlled again so that the tuning point becomes the best, so that the level reaches the maximum (5IO). After that, this level is maintained.

FIG. 4 is a diagram showing the state of the antenna tuning section 2 due to the above-described operation. Figure (a) shows the reception frequency f in the initial state.
Indicates a state where synchronization at 0 is not achieved. From this state, the variable capacitance diodes 221-22. By changing the capacitance of and tuning at the receiving frequency f0,
).

However, the output control unit 17 cannot determine that this state is the best point and changes the capacitance further, resulting in a tuning shift in the opposite direction as shown in FIG. However, this time we can recognize that the state shown in figure (b) is the best, so we change the capacitance in the opposite direction,
As a result, an optimal tuning state can be obtained as shown in FIG. 4(d). This series of operations follows changes in the tuning level, so it is executed instantaneously.

In this embodiment, when all 4-bit outputs of the comparator are "H", the maximum voltage is the voltage across the variable capacitance diode 22.
．． .about.223, the output control section 17 controls the transfer gates 16, .about.16. It is configured to control this, but it goes without saying that this can be changed arbitrarily.

〔Effect of the invention〕

As explained above, in the present invention, a variable capacitance diode is provided in the antenna tuning circuit for adjusting the tuning frequency, and the voltage applied to the variable capacitance diode is controlled to vary according to the electric field strength of the received radio paging signal. Therefore, the state where the electric field strength is maximum, that is, the tuned state, can be automatically adjusted, and furthermore, the reliability of the receiver can be improved without the need for mechanical adjustment.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the selective calling receiver of the present invention, FIG. 2(a) or i) is a waveform diagram of each part of FIG. 1, and FIG. flowchart,
4(a) to 4(d) are frequency characteristic diagrams for explaining the tuning operation, and FIG. 5 is a block diagram of a conventional receiver. Engineering...Antenna, 2...Antenna tuning circuit, 3...
・Radio section, 4... Limiter, 5... Discre, 6
...LPF, 7...Comparator, 8...Signal control section, 9...Individual signal storage section, 10...Speaker,
11... Preamplification section, 12... AC-DC conversion section,
13...Hold section, 14...Reference voltage generation section, 1
5. ~154... comparator, 16. ~16.・・・
・Transfer gate, 17...output control section, 1B+
-184,191~19s...Bleeder resistance, 21.
...Fixed capacitor, 22, ~223... Variable capacitance diode, 23... Variable capacitor. Figure 3 Figure 4 Chi. Na

Claims (1)

[Claims] 1. In a radio selective calling receiver equipped with an antenna tuning circuit, a variable capacitance diode for adjusting the tuning frequency is provided in the antenna tuning circuit, and a radio paging receiver receives a voltage applied to the variable capacitance diode. 1. A radio selective calling receiver, characterized in that it is configured to perform change control according to the electric field strength of a signal. 2. The means for changing and controlling the voltage applied to the variable capacitance diode is A that converts the received radio paging signal into a DC voltage.
a C-DC converter, a plurality of comparators that compare the converted DC voltages with different reference voltages, a plurality of transfer gates each capable of outputting different voltages prepared in advance, and a plurality of transfer gates each capable of outputting a different voltage prepared in advance; 2. The radio selective calling receiver according to claim 1, further comprising an output control section for selectively operating said transfer gate.