JP2921285B2 - Radio selective call receiver - Google Patents

Abstract

PURPOSE:To prevent the deterioration in a reception rate of a desired wave of the selective call radio receiver due to inter-modulation of an interference wave when an electric field strength of the interference wave is very strong. CONSTITUTION:The receiver is provided with a high frequency amplifier 3 having two transistors(TRs) 4, 5 amplifying a radio signal modulated by a digital selective call signal having a synchronizing signal to form a cascode amplifier, a demodulation section 10 demodulating the digital selective call signal and a notice section 12 replying the selective call signal, and also with a control section 11 detecting the presence of the synchronizing signal outputted from the demodulation section 10 to give a low level signal to the high frequency amplifier 3 when the synchronizing signal is in existence and giving a high level signal when no synchronizing signal is in existence, and a control TR 6 receiving the low or high level from the control section 11 to supply a bias signal for a normal bias or a gain reduction signal to the cascode amplifier respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio selective call receiver, and more particularly, to a radio selective call receiver improved in the problem that the reception rate is reduced due to cross modulation of the radio selective call receiver.

[0002]

2. Description of the Related Art In recent years, the number of radio selective calling receiver subscribers has been increasing steadily, and the frequency of radio waves used for calling tends to increase due to liberalization of services and the like. In an environment where there are many such frequencies, even in a place where the electric field of the desired wave received by the own radio selective receiver is sufficient, the interfering wave (the radio selective calling other than that of the own radio selective receiver) can be performed. If the electric field of the service wave) is very strong, a failure has occurred which indicates a decrease in the reception rate for calls due to the mutual interference of the electric fields.

As shown in FIG. 3, the conventional radio selective calling receiver includes an antenna 1 for receiving a transmission signal including a data signal to be described later transmitted from a base station, a high-frequency transistor 4 for amplifying the reception signal, 5. Decoding a high-frequency amplifier 3A comprising DC bias resistors 7 and 8 and a signal including an ID code for calling the own station included in the data signal modulated into the received signal, and collating the decoded signal with the built-in own station ID code. Demodulation unit 10 that outputs a calling signal when they match
And a notification unit 12 for inputting the call signal and outputting a notification sound, and a stabilizing power supply unit 13 for supplying power to the high-frequency amplification unit 3A. The received data signal normally outputs a burst signal intermittently for about 2 seconds at a cycle of 30 seconds. In the signal format of the burst signal, the head has a synchronization signal, and the ID code of the calling party is arranged next. The notification unit 12 has notified the carrier. Here, when there is a strong interfering wave described at the beginning, cross-modulation distortion occurs in the high-frequency amplifier 3A,
There was a case where a failure such that the synchronization signal was canceled occurred.

[0004]

SUMMARY OF THE INVENTION An object of the above-mentioned conventional radio selective calling receiver, since conventional RF amplification unit, when receiving strong interference wave and the original received signal, more intermodulation distortion saturation of a transistor or the like Has the disadvantage of causing In the worst case, there is a disadvantage that the synchronization signal is canceled and the reception rate is lost due to loss of reception synchronization.

[0005] An object of the present invention is to examine whether or not the reception is impossible due to the disappearance of the synchronizing signal due to the above-mentioned interference wave, by changing the high frequency and the gain of the amplifying section, and to determine the presence or absence of the synchronizing signal. The present invention is to provide a radio selective call receiver provided with a control means for confirming in accordance with the above procedure.

[0006]

SUMMARY OF THE INVENTION A radio selective calling receiver according to the present invention comprises a high frequency amplifier forming a cascode high frequency amplifier by two transistors for amplifying a radio signal modulated by a digital selective calling signal having a synchronization signal. , A radio selective calling receiver having a demodulator for decoding the digital selective calling signal and a notifying section for generating a ringing sound in response to the selective calling signal, the demodulator being inputted to the demodulator.
Interference of the demodulator due to excessive input signals including interfering signals
The presence or absence of the synchronization signal due to the cancellation of the synchronization signal by the modulation is detected, and in the case where the synchronization signal is present, the cascode is set in the high-frequency amplifier to set a gain for steady reception.
A low-level signal is supplied to the high-frequency amplifier, and in the absence of a synchronization signal, the gain of the high-frequency amplifier should be reduced.
And a control unit for supplying a signal of a “high” level. When the control unit inputs information of a state transition without a synchronization signal from a state with a synchronization signal as the steady reception, the control unit supplies a signal to the high-frequency amplifier. “High” from the “Low” level control signal
There predetermined number rows To convert the control signal of the level disturbance
Check that the signal cancels the synchronization signal.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 shows a configuration diagram of an embodiment according to the present invention. FIG. 2 is a flowchart showing the operation of the control unit, which is a main part of the present embodiment. 1, the same reference numerals as those in the conventional example of FIG. 3 have the same functions. The signal format of the transmission signal in the present embodiment is a format in which a synchronization signal included in a predetermined head is repeatedly transmitted at regular intervals in order to synchronize transmission data and reception data as described above. is there.

In FIG. 1, a radio signal received by an antenna 1 is input to a high-frequency amplifier 3 through a DC component cutting capacitor 2. The amplified radio signal is sent to the demodulation unit 10 and converted into a baseband signal.
The demodulated baseband signal is input to the control unit 11, and when it matches with its own calling number (ID code), the notifying unit 12 notifies the carrier. When the control unit 11 determines that the synchronization signal cannot be received due to the intermodulation of the interfering wave, the control unit 11 sends the control signal to the high-frequency amplifier 3 to reduce the gain.

[0009] Next will be described the configuration and operation of the high-frequency amplifying device 3 of this embodiment. The high-frequency amplifier 3 includes a transistor 4,
5, a control transistor 6, and DC bias resistors 7, 8, and 9. The input terminal is connected to the base of the transistor 4 and the resistor 7, and the other end of the resistor 7 is connected to the resistors 8, 9 and the collector of the transistor 5,
The other end of the resistor 9 is connected to the collector of the transistor 6. The collector of the transistor 4 is connected to the emitter of the transistor 5, and the connection point between the base of the transistor 5, the emitter of the transistor 6, and the resistor 8 is connected to the stabilized power supply 1
3 is connected. Gain control of the RF amplifier device 3 according to the present invention is performed by the transistor 6 and the resistor 9. The resistor 9 is connected to a connection point between the transistor 5 and the resistor 8, and the other end of the resistor 9 is connected to a collector of the transistor 6. The base of the transistor 6 is connected to the control unit 11, and the control signal of the control unit 11 is "HIGH" (power supply voltage or more than the power supply voltage value of the reception unit) or "LO".
One of two values of W "(0 V) is output.

When the receiving section (antenna 1, capacitor 2, high-frequency amplifier 3, demodulation section 10) is decoding the synchronization signal, control section 11 controls transistor 6 of high-frequency amplifier 3
"LOW" (0V) voltage is applied to the base of
With this and the power supply voltage applied to the high frequency amplifier 3, the transistor 6 is turned on. Since the resistor 9 is designed to be sufficiently smaller than the resistor 8, most of the current flows through the resistor 9.

When the receiving unit cannot receive the synchronization signal, it considers that the level of the interference wave is strong, and the control unit 11 sets the control signal voltage to the transistor 6 of the high-frequency amplifier 3 to "H".
At this time, the base voltage of the transistor 6 is equal to or higher than the emitter voltage, the transistor 6 does not conduct, and no current flows through the resistor 9 and only the resistor 8 flows. Therefore, by setting the control signal to "HIGH", the gain of the high-frequency amplifier 3 is reduced, and the level at which the interference wave is input can be suppressed.

[0012] Then the procedure of the control of the control unit 11 to the procedure and the high frequency amplifying unit 3 of the detection of the synchronizing signal will be described with reference to the flow of FIG. At the start, that is, when the power is turned on, the control signal to the high frequency amplifier 3 is set to "LOW" (S1).
01). The control unit 11 determines whether or not the synchronization signal transmitted at a constant period has been received (S102). If the synchronization signal has not been received (including the case of non-reception due to strong electric field intermodulation of an interfering wave), the determination is NO. However, here the control signal is again "LOW"
(S103). When the control signal is "L"
In the case of “OW”, the control unit 11 determines whether or not the intermittent synchronization signal of the 30-second cycle is not continuously received twice (S10).
4). In the case of two consecutive non-reception, the control unit 11, a control signal to the RF amplifier device 3 and "HIGH", to reduce the gain of the RF amplifier 3 (S105). With the gain reduced, the control unit 11 determines whether or not to receive a synchronization signal (S106). If reception is not possible, control unit 1
No. 1 considers that it is not non-reception due to strong electric field intermodulation of the interference wave, and returns the control signal to the high-frequency amplifier 3 to “LOW” (S107). When the synchronization signal is received in steps 102, 104, and 106, it is determined whether or not its own calling number has been received (S108), and when it is received, the notification unit 12 is activated and notified (S109).

[0013]

As described above, according to the present invention, when the reception rate is lowered due to the intermodulation when an interference wave of a strong electric field is input to the high-frequency amplifier, the gain of the high-frequency amplifier is reduced to reduce the interference wave. Has the effect of improving the intermodulation distortion characteristic due to the influence of the above, and significantly improving the reception rate of the desired wave as compared with the conventional one. In addition, by providing means for verifying the loss of the synchronization signal when the reception rate decreases in a predetermined procedure, it is possible to determine whether or not the loss is due to a decrease in the reception rate due to intermodulation distortion.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control operation according to the present embodiment.

FIG. 3 is a configuration diagram of a conventional radio selective calling receiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 Capacitor 3, 3A High frequency amplifier 4, 5, 6 Transistor 7, 8, 9 Resistance 10 Demodulation unit 11 Control unit 12 Notification unit 13 Stabilized power supply unit

Claims (2)

(57) [Claims] 1. A high-frequency amplifier forming a cascode high-frequency amplifier by two transistors for amplifying a radio signal modulated with a digital selective calling signal having a synchronization signal, a demodulator for decoding the digital selective calling signal,
In the radio selective calling receiver and a notifying section for generating a ringing in response to the selective call signal, the input to the demodulator
Demodulation due to excessive input signal including interfering signal
Wherein when the presence is detected and the synchronization signal the presence or absence of a synchronization signal due to the fact that the synchronization signal is canceled by the intermodulation of the vessel is in order to set the gain of the steady-received by the high frequency amplifier Kas
Supply a low-level signal to the code high-frequency amplifier ,
In the absence of a synchronization signal, the gain of the high- frequency amplifier is reduced.
And a control unit for supplying a “high” level signal to the high-frequency amplifier when the control unit inputs information of a state transition without a synchronization signal from a state with a synchronization signal as the steady reception. "low" level radio paging receiver, wherein the this <br/> a procedure for converting a "high" level control signal from the control signal to check the cancellation of the synchronization signal by a predetermined number of times performed disturbance signal . 2. When the control unit detects the absence of a synchronization signal at least twice, the previously output “low” level is switched to the “high” level, and even after switching to the “high” level, 2. The radio selective calling receiver according to claim 1, wherein when the absence of the synchronization signal is detected, the switched "high" level is returned to a "low" level.