JPH01293024A - Paging system and its receiver - Google Patents

Abstract

PURPOSE:To digitize a succeeding demodulator circuit and averaging process circuit by making the modulating frequency band of transmitting carriers sufficiently narrower. CONSTITUTION:Since the frequency band of transmitting signals is narrowed and a receiver is constituted in such a way that the signals received by the receiver are converted into digital signals after they are converted into signals having a sufficiently narrow frequency band, an A/D converter having a low sampling frequency can be used as the A/D converter 28 of the system and a digital delaying device 42 can be used as the succeeding demodulator circuit 40 instead of a one-bit delaying device to be used for performing two-phase DPSK demodulation. Therefore, the devices after the demodulator circuit 40 can be digitized and the constitutions of the A/D converter 28 and demodulator circuit 40 can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a paging system and a receiving device for a paging system, and particularly to a device that repeatedly transmits the same data multiple times and receives it.

[Prior Art] A typical wireless paging system is a personal calling system called a "pager." Communication methods for this pager include a tone signal method and a digital signal method. Of these, in the former case, it is difficult to convert even a part of the circuit into LSI, whereas in the latter case, the main part of the circuit can be formed into LSI, so the size of the device can be reduced to about 80% compared to the former. I can do it. Therefore, digital signaling systems are becoming mainstream these days.

FIG. 4 shows a schematic configuration of a receiving device among conventional transmitting/receiving devices employing a digital signal system.

In the figure, a 250 MHz modulated signal received by an antenna 1 is amplified by a high frequency amplifier 2, then converted to 21.4 Ml1z by a first mixing station 3, and then sent to a second mixing station 5 via a bandpass filter 4. added to. The second mixing station 5 converts the modulated signal added thereto into an intermediate frequency of 455 kl (z) and outputs it. This intermediate frequency is applied to an intermediate frequency (IF) amplifier 7 via a bandpass filter 6, where After being amplified, it is input to the demodulation circuit 8.The demodulation circuit 8 extracts the transmission signal component from the modulated signal and supplies it to the active low-pass filter 9.The active low-pass filter 9 includes a comparator, and the signal component and A digital signal is generated by comparing it with a reference level and inputted to the decoder 10.The decoder 10 sends data corresponding to the digital signal to FROMI.
It is taken out from I and added to the speaker 13 via the buffer amplifier 12.

Although such conventional transmitting/receiving devices can be made smaller through digitization, it has also become important to widen the service area, and the present inventor, in collaboration with others, As a method to expand this service area, we have previously invented a wireless paging system that transmits the same modulated signal multiple times and performs averaging and addition on the receiving side to regenerate the transmitted signal, and has already applied for a patent (patent application). 1982-332172). In this method, a transmitting device modulates a carrier wave of, for example, 400 MHz with an ID code and a message for personal identification, and repeatedly transmits this. After the receiving device demodulates the received signal, it performs averaging processing, deciphers the message, and decodes the ID code. It performs determination, etc., and FIG. 5 is a schematic configuration diagram of a receiving device that performs these processes. In the figure, a modulated signal is received by a receiving circuit 14, then converted to a baseband signal by a demodulating circuit 15, and inputted to an averaging processing circuit 1B. This averaging processing circuit IB improves the S/N ratio by averaging a plurality of times and applies it to the message processing circuit 17 and the ID code discrimination circuit 20. Among these, the message processing circuit 7 decodes the message from the baseband signal obtained by the averaging process and outputs the information, and then the display drive circuit 18 displays it on the display 19. On the other hand, the ID code discrimination circuit 20 selects the ID code part of the baseband signal, compares it with the ID code registered in the built-in ROM, and when the two match, causes the buzzer 22 to sound via the buzzer drive circuit 21. . Thus, it is possible to notify the recipient that a message has been sent and to display its contents.

This receiver is for use in paging systems, and focuses on the fact that high-speed signals are not required to be transmitted.It improves the S/N ratio through averaging and improves reception sensitivity to increase service area. We are trying to expand our business.

Incidentally, in the receiving device shown in FIG. 5, the averaging processing circuit 16 is configured to input an analog signal and output a digital signal, and a message decoding circuit 17 and a display driving circuit 18 connected to this are configured to input an analog signal and output a digital signal. , the ID code discrimination circuit 20, and the buzzer drive circuit 21 are digital circuits, so they can be constructed with a single-chip LSI, thereby realizing miniaturization of the device.

[Problems to be Solved by the Invention] Regarding the receiving device shown in FIG. 5, since the receiving circuit 14 handles a weak high frequency signal, it is impossible to completely digitize it, but the averaging processing circuit If 16 and demodulation circuit 15 can be digitized, further miniaturization can be achieved.

Of these, the averaging processing circuit 16 can be digitized by using, for example, a digital averaging processing circuit configured to update the data stored in the memory by adding the received signal one after another in packet units using a digital memory. It is.

On the other hand, if the demodulation circuit 15 is also provided with an A/D converter at the front stage, it is not impossible to digitize itself, but if the high frequency signal is sampled as it is, the A/D converter
There was a problem in that a D converter with a high sampling frequency f was required, making it extremely expensive. Furthermore, although the circuit configuration of the demodulation circuit itself differs depending on the modulation/demodulation method, even when the C/N ratio of the signal obtained by the receiving circuit is small, the error rate of the demodulated data is relatively low compared to other modulation methods. It is possible to employ a two-phase DPSK (differential phase keying) modulation and demodulation method, which is one of the non-coherent detection methods with a low transmission rate. In this case, a demodulation circuit may be employed in the DPSK, which is composed of a multiplier and a 1-bit delay device to which input signals are supplied, and a cosine roll-off filter that responds to the output signal of this multiplier. however,
This circuit also has a problem in that the circuit configuration of the 1-bit delay device becomes complicated.

The present invention was made in order to solve the above problems, and it is possible to digitize at a low cost without complicating the configuration after the demodulation circuit, thereby further reducing the size of the receiving side device. The object of the present invention is to obtain a paging method and a receiving device for a paging system that can perform the following tasks.

[Means for Solving the Problem] In the paging method according to the present invention, the sampling frequency of A/D conversion is set to several tens of kilohertz in order to realistically digitize the configuration after the demodulation circuit in the receiving device. In other words, the modulation frequency band of the carrier wave to be transmitted is set to be sufficiently narrow. In other words, in the paging method, the modulated wave obtained by modulating a carrier wave with the data to be transmitted is repeatedly transmitted multiple times, and the transmitted data is received and demodulated. After converting the received modulated wave into a signal having a carrier wave with a frequency higher than 1/2 of the frequency of the modulated wave, A/D conversion is performed to obtain a digital signal, and this digital signal is used to demodulate. A paging method is provided, which is characterized in that it performs the following: and then performs averaging.

Further, according to the present invention, for a paging system comprising a receiving circuit, a frequency converting section that converts the modulated wave obtained by the receiving circuit to a low frequency band, and a demodulating circuit that demodulates using the output signal of the frequency converting section. In the receiving device, the frequency converter is configured such that the highest frequency of its output signal is several tens of kilohertz or less, and is provided with an A/D conversion means for converting the output signal from the frequency converter into a digital signal, There is provided a receiving device for a paging system, characterized in that the demodulation circuit is converted into a digital circuit and is configured to process a digital signal obtained by the A/D conversion means.

[Function] In the present invention, the frequency band of the transmitted signal is narrowed, and the receiving device converts the received signal into a signal in a sufficiently low frequency band, and then converts it into a digital signal. A D converter with a low sampling frequency is sufficient, and a digital delay device can be used as a subsequent demodulation circuit in place of a 1-bit delay device when performing two-phase DPSK demodulation. As a result, digitization after the demodulation circuit becomes possible, and the configurations of the A/D converter and the demodulation circuit can be simplified.

[Embodiment] FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 4 indicate the same elements. This figure shows only the receiving device of the transmitting/receiving device as a paging system that adopts the two-phase DPSK modulation/demodulation method, and the receiving circuit 14 amplifies and outputs a two-phase DPSK modulated signal with a carrier frequency of fS. In this case, the frequency converter 30 is provided at the subsequent stage. This frequency conversion section 30 receives the DPSK modulated signal as one input, receives the output signal of the local oscillation circuit 31 as the other input, and connects a mixing circuit 32 that mixes both and outputs the resultant signal. It has a low-pass filter 33 that passes only the frequency components of the band. An A/D converter 28 is provided on the output side of the frequency converter 30 to convert a modulated wave in a low frequency band into a digital signal. Further, at the output stage of the A/D converter 28, a digital multiplier 41. Digital delay device 42 and digital filter 43
A DPSK demodulation circuit 40 consisting of the following is provided, and a digital averaging processing circuit 29 for averaging the output of this DPSK demodulation circuit 40 is provided.

This digital averaging processing circuit 29 has a memory 50 that stores the digital signal from the DPSK demodulation circuit 40 based on an addressing signal and a read/write (R/W) signal from a CPU (central processing unit) 52. ing. For example, when data for one packet is stored in the memory 50, it is read out one after another, added to the corresponding data of the next packet in the adder 54, the resulting 10 data are temporarily stored in the register 5B, and then 50 (. By repeating this operation multiple times, averaging processing is performed, and the number of repetitions is increased to n
times, the signal-to-noise ratio of the signal is 3 Iogz n (dB)
will only improve. The circuit configuration after the digital averaging processing circuit 29 is completely the same as that shown in FIG. 5, so a description of the configuration will be omitted.

The operation of this embodiment configured as described above will be explained below with reference to FIG. 2 as well.

First, as shown in FIG. 2(a), a carrier frequency is f from a transmitting device (not shown). When a narrowband modulated signal with a bandwidth of approximately 1 kHz is transmitted, the receiving circuit 14 receives it and applies the amplified modulated signal to the mixing circuit 32 . At this time, the local oscillation circuit 31 outputs a sine wave signal of (f - 10kHz) and adds it to the mixing circuit 32. The mixing circuit 32 mixes these signals to generate the second signal.
As shown in Figure (b), a modulated signal with a center frequency of 10 kHz and a modulated signal with a center frequency of 2 f -10 kHz are output. Among these, the center frequency is 2 f −1
Since the 0kHz modulation signal is removed by the low-pass filter 33, the frequency converter 30 outputs a signal with a center frequency of 10kHz.
The modulation signal has a bandwidth of 10 kHz (5 kHz ” 1
5kllz) is output.

Next, the A/D converter 28 converts this modulation signal into a digital signal, but since the maximum frequency of the modulation signal is 15kllz, it is sufficient to set the sampling frequency to 30kl (z, and in this sense, it is a simple With a configuration, and
An inexpensive A/D converter is sufficient.

Next, the DPSK demodulation circuit 40 processes the digital signal and outputs a transmission signal, that is, a baseband signal.
The processing procedure and the like are well known, and the operation of each element after the digital averaging processing circuit 29 is also well known as a wireless paging system, so a description of the operation will be omitted.

In this case, as a digital circuit, the sampling frequency f
Since it is sufficient to use a quantization bit of about 40kllz, and 8 bits is sufficient for the number of quantization bits required for demodulation and averaging, the circuit configuration is simplified and is One chip L
It is also possible to convert it into an SI.

Thus, according to this embodiment, digitization after the demodulation circuit and simplification of the configurations of the A/D converter and the demodulation circuit are achieved, thereby realizing miniaturization and cost reduction of the device.

[Effects of the Invention] As is clear from the above explanation, according to the present invention,
Since the modulation frequency band of the transmitted wave is sufficiently narrowed, the receiving device can convert the received modulated signal to a low frequency band, so that the sampling frequency required for A/D conversion of the modulated signal can be low. , it became possible to digitize the subsequent demodulation circuit and averaging processing circuit.

Furthermore, the digital circuit portion can be implemented as a one-chip LSI, which has the effect of making the receiving device even more compact.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIGS. 2(a) and 2(b) are diagrams showing the frequency conversion situation to explain the operation of the embodiment, and FIG. FIG. 4 is a block diagram showing the configuration of the digital averaging processing circuit in FIG. 1, FIG. 4 is a block diagram showing the configuration of a receiving device used in a conventional paging system, and FIG. FIG. 2 is a block diagram of the proposed receiving device. 28... A/D converter 29... Digital averaging processing circuit 30...
Frequency conversion unit 40...DPSK demodulation circuit Inventor: Shun Hirohashi Patent applicant: Victor Japan Co., Ltd.

Claims (2)

[Claims] (1) In a paging method in which a modulated wave obtained by modulating a carrier wave with data to be transmitted is repeatedly transmitted multiple times, and the transmitted data is received and demodulated, the frequency band of the modulated wave is set to several tens of kilohertz. With a narrow band of about
A/D after converting the received modulated wave into a signal having a carrier wave with a frequency higher than 1/2 of the frequency of the modulated wave.
A paging method characterized by converting into a digital signal, demodulating using this digital signal, and then performing averaging. (2) A receiving device for a paging system comprising a receiving circuit, a frequency converting section that converts the modulated wave obtained by the receiving circuit to a low frequency band, and a demodulating circuit that performs demodulation using the output signal of the frequency converting section, The frequency conversion section is configured such that the highest frequency of its output signal is several tens of kilohertz or less, and A/D conversion means for converting the output signal from the frequency conversion section into a digital signal is provided, and the demodulation circuit is 1. A receiving device for a paging system, characterized in that it is configured to be converted into a digital circuit and to process a digital signal obtained by the A/D conversion means.