KR19990005964A - Demodulation device for two-way radio call data transmission system - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

Wireless Call Data Transmission System

2. The technical problem to be solved by the invention

Only the fixed data rate can be demodulated in the demodulator applied to the general two-way wireless paging data transmission system, which solves the inconvenience and cost loss of replacing the corresponding demodulator in the terminal station when improving the system capacity (data rate). To do so.

3. Summary of Solution to Invention

Digital switch and low pass filtering means for selectively filtering the baseband signals of the I and Q channels obtained from the QPSK demodulation unit 2 which QPSK demodulates the received radio call data with a low pass filter corresponding to each data rate. (3); A reference clock from a sampling means (4) for sampling the analog baseband signal obtained by the digital switch and the low pass filtering means (3) at a plurality of levels, and converting the digital baseband signal into a digital signal; Clock restoring means (7) for restoring a clock; Decoding and decoding the history data obtained by the sampling means (4) in synchronization with the reference clock obtained by the block recovery means (7) to restore to the original data sequence and to deliver to the demultiplexer (10) And descrambling means (8); Control means 12 for controlling the switching of the digital switch and the low pass filtering means 3 according to a control command transmitted from the network manager 16 to select a low pass filter corresponding to each data rate. It is a feature.

4. Important uses of the invention

It is applied to a radio call data transmission system for receiving and demodulating radio call data and a bidirectional radio call data satellite transmission system.

Description

Demodulation device for two-way radio call data transmission system

The present invention selectively demodulates data of a frequency (52-88MH _Z ) received from a down converter via a antenna and a low noise amplifier in a bidirectional radio call data transmission system using satellites according to a corresponding data rate. Demodulation of the two-way radio call data transmission system that reproduces the clock and provides it to the demultiplexer and reports the reception status and the alarm signal of the demodulator to the network management unit in connection with a paging remote control block (PECBFK DIRCLDGKA). It was intended to save the device.

The present invention relates to a demodulation device for a terminal station of a two-way radio call high speed data transmission system using satellites.

In general, a two-way radio call data transmission earth station system using a satellite is composed of a central base station and a terminal station. to provide.

In such a general two-way radio call data transmission system, a demodulator applied to a conventional terminal station is configured to demodulate only a fixed data rate. In other words, the demodulator can receive only a signal having a fixed data rate arbitrarily and demodulate it into an original signal, and demodulation is impossible for data rate received signals other than the fixed data rate.

Therefore, since the demodulator applied to the general two-way radio call data transmission system can demodulate only a fixed data rate, it is necessary to replace the corresponding demodulator of the terminal station in order to improve the system capacity (data rate). There was a problem of being consumed.

Accordingly, the present invention has been proposed to solve the problems of the demodulator applied to the terminal station of the conventional two-way radio call data transmission system as described above, and an object of the present invention is an antenna and a low noise amplifier in a two-way radio call data transmission system using satellites. Selectively demodulate the data of the frequency (52-88MH _Z ) received from the down-converter according to the data rate by providing the demultiplexer to reproduce the data and clock, and provide the paging remote control block (Paging) Remote Control Block (hereinafter referred to as PRCBFK DIRCLDGKA) provides a demodulation device for a two-way radio call data transmission system that reports the demodulator's reception status and alarm signal to the network management unit.

More specifically, a low pass filter corresponding to each data rate is independently implemented to receive a variable data rate, and a low pass corresponding to the corresponding data rate by using a switch controlled by digital logic. In order to improve the capacity of the system by selectively demodulating data of 64/128/256 / 512kbps by selecting the pass filter, the system capacity is increased by using the variable demodulator without replacing the corresponding demodulator of each terminal station. In order to minimize the cost and time required to provide a demodulation device of a two-way radio call data transmission system.

Technical means for achieving the object of the present invention, selectively filtering the baseband signals of the I and Q channels obtained from the QPSK demodulator for QPSK demodulation of the received radio call data with a lowpass filter corresponding to each data rate. A digital switch and low pass filtering means for outputting the control unit; Sampling means for sampling the analog baseband signals obtained from the digital switch and the low pass filtering means at a plurality of levels, converting them into digital signals, and outputting the digital signals; Clock recovery means for recovering a reference clock from the parallel data area obtained by the sampling means; Decoding and descrambling means for decoding and descrambling the parallel digital data obtained by the sampling means synchronously with the reference clock obtained by the clock recovery means, restoring the original data sequence, and delivering the original data sequence to a subsequent demultiplexer; Control means for controlling the switching of the digital switch and the low pass filter in accordance with a control command transmitted from the network management unit so that the low pass filter corresponding to each data rate is selected.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

1 is a block diagram of a demodulation device of a bidirectional wireless call data transmission system according to the present invention;

Figure 2 is a detailed configuration of the digital switch and low pass filter of Figure 1;

* Explanation of symbols for the main parts of the drawings

3: digital switch and low pass filter, 31, 32, 34, 36: first to fourth digital switch, 33, 35: first and second low pass filter, 7: clock restoring unit, 12: control unit

1 is a block diagram of a demodulation device of a bidirectional wireless call data transmission system according to the present invention.

As shown in FIG. 2, reference numeral 2 is a mixture of an IF (intermediate frequency) signal 1 of the 52-88MH _Z received from the down converter and a local oscillation signal set by the Costas loop section 5, and the I-channel 19 And a QPSK demodulator for converting the baseband signal of the Q channel 20 into reference numerals 3, and reference numeral 3 denotes base data of the I and Q channels 19 and 20 obtained from the QPSK demodulator 2, respectively. It is a digital switch and a lowpass filter which selectively filter out the lowpass filter corresponding to the rate.

Reference numeral 4 denotes a sampling unit for sampling the analog baseband signal obtained from the digital switch and the low pass filter unit 3 into a plurality of levels, converting the digital signal into digital signals, and outputting the reference numeral 7 to the sampling unit 4. A clock recovery unit for restoring a reference clock from the parallel data string obtained by the reference numeral 8, wherein reference numeral 8 denotes a decoding and disc for synchronizing the parallel digital data obtained from the sample line 4 in synchronization with the reference clock obtained from the clock recovery unit 7, It is a decoder and descrambler 8 which scrambles and restores the original data sequence to output.

In addition, reference numeral 9 denotes an RS-422 driver for converting data and a clock obtained from the decoder and the descrambler 8 into an RS-422 signal and transferring the same to the demultiplexer 10 at a later stage, and reference numeral 15 denotes a network manager. RS-232 driver converts the control command transmitted from the (PRCB) 16 to the TTL level and converts the status signal of the terminal station outputted from the control unit 12 into an RS-232 signal and transmits it to the network management unit 16. And a receiver, and reference numeral 5 denotes a baseband signal obtained from the digital switch and the low pass filter 3, and manipulates the local oscillation signal to the resultant value and converts the adjusted local oscillation signal into the QPSK demodulator 2; It is Costas loop part to apply to.

Here, the Costas loop section 5 is a kind of a suppressed carrier loop and has the same theoretical performance as that of a phase synchronization circuit (PLL) having a square-law device. The loop is a squarelaw device that is difficult to implement at a carrier frequency. The advantage is that instead of using a multiplier and a relatively simple low pass filter (LPF), two low band filters (I channel low band filter, Q channel) The low band filter must be fully matched.

On the other hand, reference numeral 6 denotes an automatic gain control unit which detects the level of the baseband signal of the I channel 19 obtained from the digital switch and the low pass filter unit 3 and generates an amplification degree control signal. Multi Protocol Serial Communication (MPSC) unit, and reference numeral 13 is a peripheral circuit unit of the control unit 12 as a ROM for storing a control program, a RAM for temporarily storing data, and an interface unit for interfacing data. Is implemented.

Subsequently, reference number 12 controls the entire operation of the demodulator according to the control command obtained from the network manager 16, and controls the digital switch and the digital switch in the low pass filter 3 to correspond to the respective data rates. The low pass filter is selected, and the control unit receives and controls the input signal from the keypad / LCD interface unit 11.

In the above, the digital switch and the low pass filter 3 are obtained from the QPSK demodulator 2 according to the switching control signal 21 output from the controller 12, as shown in FIG. First and second digital switches 31 and 32 for selectively providing baseband signals of the I-channel 19 and the Q-channel 20 to the rear filter, and the I-channel obtained from the first digital switch 31 A first low pass filter 33 for low-pass filtering by operating only a low pass filter suitable for a data rate set by the baseband signal of the baseband signal, and the baseband signal obtained by the first low pass filter 33 21 is a low pass filtering by operating only the low pass filter in accordance with the data rate to set the third digital switch 34 and the Q-channel baseband signal obtained by the second digital switch 32 to output according to the 21) 2 low pass filter unit 35, and the second low It consists of a signal output from the filter unit 35 to the fourth digital switch 36 to the switching outputs in accordance with the switching control signal 21.

Referring to the operation of the demodulation device of the two-way radio call data transmission system according to the present invention configured as described above are as follows.

First, a signal received by the GPS antenna is down-converted to a middle frequency (1F) 1 of a band of 52-88MH _z in a down converter and then transferred to the QPSK demodulator 2. The QPSK demodulator 2 then mixes the local oscillation signal obtained from the Costas loop unit 5 with the intermediate frequency signal 1 of the transmitted 52-88MH _Z to the basis of the I channel 19 and the Q channel 20. Create a band signal. The baseband signal of the Q channel 20 of the I channel 19 is thus applied to the digital switch and the low pass filter 3 to pass through the low pass filter corresponding to each data rate. The switching control signal 21 for selecting a suitable low pass filter is generated by the control unit 12. That is, the control command transmitted from the network management unit 16 is received by the RS-232 driver / receiver 15 to receive the TTL signal. The control command converted into the TTL signal is transmitted to the control unit 12 via the multi-protocol serial communication chip 14 and the peripheral circuit unit 13 in sequence, and the control unit 12 transmits the control command. In addition to controlling the entire operation of the demodulator, a low pass filter selection signal (switching control signal 21) in the digital switch and the low pass filter 3 is generated. The control unit 12 may also generate a low pass filter selection signal by the selection signal obtained through the keypad / LCD interface unit 11.

Meanwhile, as described above, the digital switch and the low pass filter 3 have the first to fourth digital switches 31, 32, 34 according to the switching control signal 21 generated by the controller 12. Control (36) to select a low pass filter, which is explained in more detail as follows.

In accordance with the switching control signal 21, the first and second digital switches 31 and 32 switch switching. The baseband signal of the I channel 19 is switched to the first low band by the switching switching operation. The baseband signal of the Q channel 20 is connected to the second low pass filter unit 35. Then, the first low pass filter 33 operates only the low pass filter of one of the first to fourth low pass filters 33a to 33d therein to filter and output the baseband signal of the input I channel to the set band. In addition, the second low pass filter 35 also operates the low pass filter of one of the first through fourth low pass filters 35a through 35d to operate the input baseband signal of the Q channel as the set band. It will be filtered out.

For example, if the switching control signal 21 output from the controller 12 is a control signal for switching and low-pass filtering a received signal having a data rate of 64 kbps, the first low pass filter 64 kbps in the first low pass filter 33. Only the first low pass filter (64 kbps) in the second low pass filter unit 35 operates to low pass filter the baseband signals of the input I channel 19 and the Q channel 20. The baseband signals of the low-pass filtered I-channel and Q-channel are applied to the sampling unit 4 at the rear stage through the third digital switch 34 and the fourth digital switch 36, respectively. Here, the first to fourth digital switches 31, 32, 34, 36 in the digital switch and the low pass filter 3 perform the same switching operation by one switching control signal 21. The first and second low pass filter units 33 and 35 also operate to always low pass filter the same data rate.

On the other hand, the 3-bit slicer 4a in the sampling section 4 samples the baseband signal of the I-channel output from the digital switch and the low pass filtering section 3, and digitally converts one of the eight levels to three bits. The 3-bit slicer 4b also samples the Q-channel baseband signal output from the digital switch and the low pass filter 3, and digitally converts one of eight levels. 3-bit parallel data string output.

Then, the clock recovery unit 7 restores the reference clock from the 3-bit serial data streams of the I and Q channels respectively output from the sampling unit 4, and provides the decoded clock to the decoder and the descrambler 8 accordingly. The descrambler 8 decodes and descrambles the 3-bit data regions of the I and Q channels input in synchronization with the reference clock to restore the original data sequence. The recovered data sequence is converted into an RS-422 signal by the RS-422 driver 9 and transferred to the demultiplexer (DEMUX) 10 at a later stage.

The automatic gain control section 6 detects the level of the baseband signal of the I channel output from the digital switch and the low pass filter section 3 to control the gain of the variable amplifier in the QPSK demodulation section 2. A signal 17 is generated, and the Costas loop unit 5 compares the I-channel baseband signal with the Q-channel baseband signal, and adjusts and outputs the local oscillation signal currently being output with the difference value.

In addition, the control unit 12 transmits the corresponding state information to the network management unit (PRCB) 16 when an operation problem of the system or an abnormality of the demodulator occurs, and the procedure is performed by surrounding the 8-bit state serial data generated by the control unit 12. The circuit unit 13, the multi-protocol serial communication chip 14, and the RS-232 driver / receiver 15 are sequentially transmitted to the network management unit 16.

As described above, the present invention can demodulate all signals received at a variable data rate, so it is necessary to replace a corresponding demodulator of a terminal station scattered in each region when improving the capacity of a system or using a new service using a high data rate. There is no need to reduce the tremendous cost of replacing the demodulator as in the past, and also eliminates the time required to replace the demodulator.

Claims (3)

In the two-way radio call data transmission system for transmitting radio call data through a satellite, Digital switch and low pass filtering means for selectively filtering the baseband signals of the I and Q channels obtained from the QPSK demodulation unit 2 which QPSK demodulates the received radio call data with a low pass filter corresponding to each data rate. (3); Sampling means (4) for sampling the analog baseband signal obtained by the digital switch and the low pass filtering means (3) at a plurality of levels, and converting the digital signal into digital outputs; Clock recovery means (7) for restoring a reference clock from the parallel data sequence obtained by said sampling means (4); Decoding and decoding the parallel digital data obtained by the sampling means (4) in synchronization with the reference clock obtained by the clock recovery means (7) to restore the original data sequence and to deliver to the demultiplexer (10) And descrambling means (8); A control means 12 for controlling the switching of the digital switch and the low pass filter means 3 in accordance with a control command transmitted from the network manager 16 so that the low pass filter corresponding to each data rate is selected; Demodulation device of the two-way radio call data transmission system, characterized in that configured. The method according to claim 1, wherein the digital switch and the low pass filter means, The baseband signal of the I channel 19 and the Q channel 20 obtained by the QPSK demodulator 2 is selectively provided to the rear filter according to the switching control signal 21 output from the control means 12. A first low pass filter for performing low pass filtering by operating only the first and second digital switches 31 and 32 and the baseband signal of the I channel obtained by the first digital switch 31 according to the data rate set A third digital switch 43 and a second digital switch 32 for switching and outputting the ground band signal obtained by the first low pass filter 33 in accordance with the switching control signal 21; A second low pass filter 35 for low-pass filtering of the Q channel obtained from the second channel, and a fourth digital switch for switching and outputting the signal output from the second low pass filter 35 according to the switching control signal 21. Two-way radio call data, characterized in that consisting of 36 Demodulation device for transmission system. The method of claim 2, wherein the first low pass filter unit 33 and the second low pass filter unit 35, A first lowpass filter for low-pass filtering the analog baseband signal input when the data rate is 64Kbps, a third lowpass filter for lowpass filtering the analog baseband signal input when the data rate is 128Kbps, and a 512Kbps data rate And a fourth low pass filter configured to low-pass filter the analog baseband signal inputted when the demodulator is bidirectional radio call data transmission system.