JP2819919B2 - Radio selective call receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is used for wireless call communication. In particular, the present invention relates to a technique for removing intermodulation due to unnecessary waves of a wireless signal having a close frequency.

[0002]

2. Description of the Related Art Radio selective calling receivers (pagers)
Has the NTT system in Japan and the POCSAG code internationally. Both are 512 bits / s by FSK modulation
Data communication using a BCH code for error detection and correction.

[0003] The subscribers of the radio selective calling receiver are steadily growing, and the frequency of radio waves used for calling tends to increase at an accelerating rate due to the liberalization of services.

[0004]

In such a situation where a number of close frequencies are mixed, an unnecessary wave (own wave) can be obtained even in a place where the electric field of the desired wave received by the radio selective calling receiver is sufficient. If the electric field of the radio selective call service other than the radio selective call receiver is receiving an extremely strong electric field, for example, if it moves directly under the transmission tower, the radio selective call may be caused by mutual interference of the electric fields. There is a problem that the reception rate of the receiver is significantly reduced.

The present invention has been made in such a background, and at the time of intermodulation by an unnecessary wave, the level of an input signal is attenuated to improve the intermodulation and improve the reception rate of a desired wave. It is intended to provide a radio selective calling receiver.

[0006]

According to the present invention, there is provided an antenna for receiving a radio signal, an amplification circuit for amplifying the radio signal arriving at the antenna, and a demodulation unit for demodulating the signal amplified by the amplification circuit. A receiving unit, a control unit for extracting and identifying call number information from a signal demodulated by the receiving unit, and a notifying unit for notifying a carrier of a call according to an instruction of the control unit. In the equipped radio selective calling receiver,
The receiving unit includes means for attenuating a reception gain at a stage preceding the amplifying circuit, and the control unit activates the means for attenuating the call number information when the call number information cannot be identified from a received signal, thereby enabling the call number information Identify and attenuate the hand
The call number information can be identified even when the stage is enabled.
If not, disable the attenuating means and
It is characterized by including means for returning to a state .

The attenuating means includes a semiconductor switching element provided in the antenna circuit, and a low impedance circuit for grounding the antenna input by the element, and the control section closes the semiconductor switching element. It is desirable to include bias supply means.

[0008]

A similar signal is present in the vicinity of the frequency to be received by one's own radio selective calling receiver, and the intermodulation of this signal degrades the reception rate of the desired signal.

Therefore, by attenuating the entire level of the input signal by the attenuating circuit, an unnecessary wave level from a nearby signal, which is lower than the level of the desired signal, is also attenuated at the same time. Intermodulation is improved with a lower proportion of the level.

In the present invention, a simple but freely ON / OFF attenuating circuit using a diode and a capacitor is provided, and a control unit capable of performing flow control is provided.

In the control procedure, the damping circuit is OFF in the initial state.
It has become. There, a paging signal for the paging of the radio selective paging receiver is received. This call signal is continuously transmitted for a predetermined time at a constant interval. If it can be immediately identified as a call signal to the radio selective call receiver, the user activates a ringing sound or the like to notify the wearer of the call signal.

However, due to intermodulation of adjacent signals,
If it is not possible to discriminate whether the calling signal is directed to the radio selective calling receiver or not, the attenuating circuit is turned ON at the time when it is unknown twice consecutively. By this operation, the overall level of the input signal is reduced, and the unnecessary wave level from a nearby signal included therein is also reduced. At this time, the level of the desired wave also decreases, but there is no problem because it is higher than the level of the unnecessary wave. This improves intermodulation,
The ringing signal is identified.

If the calling signal cannot be identified even though the attenuating circuit is turned on, it is determined that the cause is not an unnecessary wave from an adjacent signal, and the attenuating circuit is turned off again.
To return to the initial state.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

The present invention relates to an antenna 1 for receiving a radio signal.
, An amplifying circuit 10 for amplifying a radio signal arriving at the antenna 1, a demodulating unit 11 for demodulating a signal amplified by the amplifying circuit 10, and a demodulation unit 14 demodulated by the receiving unit 14. In a radio selective call receiver including a control unit 12 for extracting call number information from a signal and a notifying unit 13 for notifying a user of a call according to an instruction of the control unit 12, a receiving unit 14 includes an amplifying circuit 10 A wireless signal attenuating circuit 2 as means for attenuating the reception gain is provided in the preceding stage, and the control unit 12 controls the wireless signal attenuating circuit 2 when the received signal is received but the call number information cannot be extracted. Characterized in that it includes a binary signal generation circuit 15.

The radio signal attenuating circuit 2 includes diodes 3 and 4 of semiconductor switching elements provided in the antenna circuit, and capacitors 6 and 7 as low impedance circuits for grounding the antenna input by the elements. Reference numeral 12 denotes a binary signal generating circuit 1 as a bias supply means for closing the semiconductor switching element.
5 and a resistor 5.

Next, the operation of the apparatus according to the embodiment of the present invention will be described.

The transmission signal in the embodiment of the present invention has a format in which a predetermined paging signal is repeatedly transmitted at regular intervals. In FIG. 1, a radio signal received by an antenna 1 passes through a radio signal attenuating circuit 2,
The signal is input to the amplifier circuit 10. The amplified wireless signal is sent to the demodulation unit 11 and is converted into a baseband signal. The demodulated baseband signal is input to the control unit 12, and when it matches the calling number of the user, the notification unit 13 notifies the wearer of the baseband by sounding and / or emitting light. If the control unit 12 determines that the paging signal cannot be identified due to the intermodulation of the unnecessary wave, the control unit 12 sends a control signal to the radio signal attenuating circuit 2 to reduce the level of the unnecessary wave.

The radio signal attenuating circuit 2 includes diodes 3 and 4, a resistor 5, and capacitors 6 to 9. The diodes 3 and 4 are connected in series. The anode side is connected to the power supply of the receiving unit 14, and the cathode side is connected to the control signal terminal of the control unit 12 through the current limiting resistor 5. The control signal is generated by the binary signal generation circuit 15 and takes two values of “High” and “Low”. The connection between the diode 3 and the diode 4 is connected to the antenna 1 and the amplifier circuit 10 through the capacitors 8 and 9. Capacitors 8 and 9 are for DC component cut,
The capacitor 6 grounds the cathode of the diode 4 at the frequency of the radio signal. The capacitor 7 grounds the anode of the diode 3 at the frequency of the radio signal.

When the receiving unit 14 is receiving the call signal, the control unit 12 controls the resistor 5 of the radio signal attenuating circuit 2.
Is applied with a voltage of “High”. In this state,
Since no direct current flows through the diodes 3 and 4 and the impedance is high with respect to the radio signal frequency, the radio signal attenuating circuit 2 does not affect the level of the radio signal.

When the receiving unit 14 cannot identify the calling signal, the control unit 12 determines that the level of the unnecessary wave is strong, and sets the control signal voltage to the radio signal attenuating circuit 2 to "Low". At this time, a direct current flows through the diodes 3 and 4, the resistance value of the diodes 3 and 4 with respect to the input radio signal decreases, and unnecessary waves flow to the ground through the diodes 3 and 4, and the capacitors 6 and 7. Accordingly, the level at which unnecessary waves are input to the amplifier circuit 10 decreases. Further, the level of the DC current flowing through the diodes 3 and 4 can be changed by changing the value of the resistor 5 to change the level at which unnecessary waves are attenuated.

Next, referring to FIG. 2, a description will be given of a state of removal of an unnecessary unnecessary wave. FIG. 2 is a diagram for explaining unnecessary wave removal.

As shown in FIG. 2A, when a similar signal exists near the desired wave, an unnecessary wave from the signal enters the desired wave area. However, the level is lower than the level of the original desired wave.

Therefore, the reception gain α causes intermodulation. Therefore, the control signal voltage of the radio signal attenuating circuit 2 is set to “Low”, and the reception gain is set to β as shown in FIG.
Decay until Then, the entire level of the input signal also drops to β, and unnecessary waves of the adjacent signal fall outside the level of the reception gain and are removed. Therefore, intermodulation is improved.

Next, a control procedure of the apparatus according to the embodiment of the present invention will be described with reference to FIG. FIG. 3 is a flowchart showing the operation of the control unit 12.

At the start, the control signal to the radio signal attenuating circuit 2 is set to "High" (S1). When the control unit 12 receives a wireless signal transmitted at a fixed cycle (S
2), identify whether it is a call signal or not (S3). If the identification is not possible, it is confirmed whether the control signal is "High" (S4). When the control signal is “High”, the control unit 12 confirms whether the wireless signal cannot be identified twice consecutively (S5). In the case where identification cannot be performed twice consecutively, the control unit 12 sets the control signal to the wireless signal attenuating circuit 2 to “Low”.
And the reception gain is attenuated (S6). With the reception gain attenuated, the control unit 12 identifies again whether the radio signal is a call signal (S7). If it cannot be identified, the control unit 1
2 judges that the cause of the indistinguishability is not due to the intermodulation of unnecessary waves, and returns the control signal to the radio signal attenuating circuit 2 to “High” (S8).

If the received radio signal is identified as a calling signal, the control unit 12 checks whether or not the received radio signal includes its own calling number (S9).
3 is activated to notify the caller of the call (S10).

[0028]

The intermodulation is improved by attenuating the level of the input signal at the time of intermodulation due to unnecessary waves.
The reception rate of the desired wave is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating unnecessary wave removal by an attenuation circuit.

FIG. 3 is a flowchart showing the operation of the apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 Radio signal attenuation circuit 3, 4 diode 5 Resistor 6-9 capacitor 10 Amplification circuit 11 Demodulation unit 12 Control unit 13 Notification unit 14 Receiving unit

Claims (2)

(57) [Claims] 1. A receiving unit comprising: an antenna from which a radio signal arrives; an amplification circuit for amplifying the radio signal arrived at the antenna; a demodulation unit for demodulating a signal amplified by the amplification circuit; and a control unit to identify and extract the call number information from the demodulated signal by parts, the radio selective calling receiver and a notification unit for notifying a call to a mobile user according to an instruction of the control unit, the receiving unit Means for attenuating a reception gain at a stage preceding the amplification circuit, wherein the control unit activates the means for attenuating the call number information when the call number information cannot be identified from a received signal, and performs the call.
Number information is identified, and the attenuating means is enabled.
If the call number information cannot be identified in the
A radio selective calling receiver comprising means for invalidating the attenuating means and returning to an initial state . 2. The attenuating means includes a semiconductor switching element provided in an antenna circuit and a low impedance circuit for grounding an antenna input by the element, and the control unit closes the semiconductor switching element. 2. The radio selective calling receiver according to claim 1, further comprising a bias supply unit.