JPH0750883B2 - Pager - Google Patents

Description

The present invention relates to a receiving system of a pager which is a wireless calling device.

[Outline of Invention]

According to the present invention, in the pager reception system, by knowing the modulation rate from the time when the data of the bit synchronization signal changes,
This is for automatically discriminating and receiving signals for pagers that are serviced at different modulation rates.

[Conventional technology]

Conventional pagers can only receive signals at a single modulation rate. For example, a pager receiving a signal with a modulation rate of 512 bps could not receive a signal with a modulation rate of 1024 bps. (See, for example, Japanese Patent Publication No. 56-501148.) [Problems and Objectives for Solving Problems] The present invention is intended to solve such problems, and the objective is to obtain different modulation speeds. Signals for pagers serviced in (for example, see Japanese Patent Laid-Open No. 59-161137)
Is automatically determined and received.

[Means for solving problems]

A pager of the present invention includes a front end for selecting a radio signal modulated at a predetermined modulation rate by a modulation signal including a bit synchronization signal and a selective calling signal, a demodulation circuit for demodulating the selected radio signal, and the demodulation circuit. And a modulation speed detector for detecting the modulation speed of the bit synchronization signal from the generated bit synchronization signal, wherein the modulation speed detector creates a reference signal for reading the demodulated demodulated signal. A generation unit, a reading unit that reads the demodulated signal based on the reference signal, a counting unit that counts the number of times the reading unit alternately reads a high level and a low level, and a count of the counting unit And a switching unit for switching the frequency of the reference signal in the reference signal generation unit according to the output.

[Action]

In the present invention, the front end selects the radio signal modulated by the modulation signal including the bit synchronization signal and the selective call signal, and the demodulation circuit demodulates the selected selective call signal. Then, the reading unit reads the demodulated signal based on the reference signal generated by the reference signal generation unit. In this case, the modulation rate detector detects the modulation rate of the demodulated bit synchronization signal, and the reference signal generator generates a reference signal having a frequency according to the detected modulation rate. As a result, the reading unit can read the selective call signal by the reference signal corresponding to the bit synchronization signal, so that the selective call signal can be surely read even when the modulation speed of the selective call signal changes.

〔Example〕

FIG. 1 is a block diagram of an embodiment of the present invention. Reference numeral 1 is an antenna, which is a portion for receiving a radio signal. The signal is selectively amplified by the front end 2 only in a predetermined frequency band. This signal is FM-modulated and demodulated by the demodulation circuit 3 in order to convert it into a required digital signal. The changing point of the digital signal is detected by the changing point detection circuit 4, and the phase of the reference signal source 5 is adjusted. The signal of the demodulation circuit 3 is read by the decoding circuit (reading unit) 6 at the time of rising of the signal of the reference signal source 5 with phase synchronization, and the counter 7 indicates the number of times the high level and the low level are read alternately in succession. count. When the number reaches a predetermined number, it is determined that the frequency of the reference signal source 5 is equal to the modulation speed of the digital signal of the demodulation circuit 3, and the subsequent signals are read at the frequency of the reference signal source.
When it is determined that they are not equal, the switching circuit 8 switches the frequency of the reference signal source 5 and the same operation is repeated.
The data read by the decoding circuit 6 is the logic processing circuit 9
Performs processing such as slave unit address match detection and notification by a buzzer. The modulation speed detector is composed of the entire circuits of 4 to 8.

FIG. 2 is a timing chart of signals used in the block diagram of FIG. (A) shows the case where the modulation speed is 1024 bps, and the demodulation circuit output 3 is a signal which repeats the high level and the low level every 1/1024 second when the bit synchronizing signal is received. When the reference signal source reads at the rising edge of the 1024HZ signal, high level and low level are read alternately as shown in the figure, so the modulation speed is determined to be 1024bps, and the subsequent data is read by the 1024HZ reference signal. Read in.

In (b), the modulation speed is 512 bps, and when the reference signal source is 1024 HZ, if you read at the rising edge, the high level and the low level continue twice, so it is determined that the modulation speed is not 1024 bps. it can. And the reference signal source is switched to 512HZ by the function of the switching circuit,
As shown in (c), when the output of the demodulation circuit is read at the rising edge, the high level and the low level alternate, so the modulation speed
It is determined to be 512 bps.

〔The invention's effect〕

As described above, according to the present invention, one pager can obtain information from many information sources by automatically discriminating the signals for the pager serviced at various modulation rates. Further, even when viewed from the transmitting side, it is not necessary to put data indicating the modulation rate in the selective calling signal, and the data transmission efficiency can be improved by that amount, and the communication system on the transmitting side can be simplified, The cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a pager according to an embodiment of the present invention. 2 (a), (b) and (c) are timing charts of the pager of the signal used in FIG.

Claims (1)

[Claims] 1. A front end for selecting a radio signal modulated at a predetermined modulation rate by a modulation signal including a bit synchronization signal and a selective call signal, a demodulation circuit for demodulating the selected radio signal, and the demodulation circuit. And a modulation rate detector for detecting the modulation rate of the bit synchronization signal from the bit synchronization signal, wherein the modulation rate detector generates a reference signal for reading the demodulated demodulated signal. Section, a reading section that reads the demodulated signal based on the reference signal, a counting section that counts the number of times the reading section alternately reads a high level and a low level, and a count output of the counting section And a switching unit for switching the frequency of the reference signal in the reference signal generating unit according to the above.