KR100262153B1 - Method for generating i/q data in a demodulator of channel modem for satellite communication system - Google Patents

Abstract

PURPOSE: A method of generating an I, Q data in a demodulator of a channel modem for a satellite communication system is provided, in case of demodulating the data received in the demodulator into I, Q data, to flexibly change and output the number of filter tab corresponding to the data input. CONSTITUTION: In a demodulator of a channel modem for a satellite communication system which demodulates the modulation frequency signal input from a down converter, the modulation frequency signal input is multiplied by a predetermined exponential function to generate a cosine function and sine function data. The number of tab is flexibly set on the basis of a control data about the number of filter tab according to the characteristics of data input from a channel unit processor which controls overall channel modem operations. A coefficient of the cosine function is filtered out of the cosine function and the sine function data to generate I data. A coefficient of the sine function is filtered out of the cosine function and the sine function data to generate Q data.

Description

A method for generating eye and queue data in a demodulator of a channel modem for a satellite communication system.

The present invention relates to a demodulation unit for a channel modem for a satellite communication system, and in particular, a channel for a satellite communication system that can flexibly set the number of filter taps corresponding to I and Q data when generating I and Q data with respect to an input frequency signal. The present invention relates to a method for generating IQ data in a demodulation unit of a modem.

With the recent rapid development of communication technology, wireless communication is being spread and activated to transmit and receive voice signals or data through airwave transmission network rather than the conventional wired network, so that subscribers located at remote sites can perform mutual communication through satellites. Satellite communication is becoming more and more common.

1 is a block diagram showing the internal configuration of a channel modem for a general satellite communication system.

In the figure, reference numeral 11 denotes a voice / data processor that performs an interface function between the UPH bus and the MPH bus and the channel unit processor 12, which will be described later, and specifically processes voice and data transmitted and received through an airwave transmission network. Data Processor (hereinafter referred to as SDP), and 12 is a channel unit processor (hereinafter referred to as CUP) that controls the overall configuration of the channel modem.

Further, reference numeral 13 denotes a transmission frequency synthesizer for synthesizing and outputting a predetermined frequency signal for generating an intermediate frequency signal, for example, 112.512 MHz ± 20 MHz, based on the control data from the channel unit processor 12, 14 is a reception frequency synthesizer for synthesizing and outputting a predetermined frequency signal for receiving an intermediate frequency signal, for example, 112.384 MHz ± 20 MHz, based on the control data from the channel unit processor 12.

Reference numeral 15 denotes a modulator for outputting a 512KHz modulated signal by BPSK or QPSK modulating the I, Q channel data output from the SDP 11, and 16 denotes a 512KHz output from the modulator 15. An intermediate frequency generator generates and outputs an intermediate frequency signal of 70 MHz ± 20 MHz based on a modulation signal and a frequency of 112.512 MHz ± 20 MHz and a reference frequency of 42 MHz applied from the transmission frequency synthesizer 13.

Reference numeral 17 denotes an intermediate frequency signal for outputting a modulated signal of 384 KHz based on the received 70 MHz ± 20 MHz intermediate frequency signal, the frequency of 112.384 MHz ± 20 MHz applied from the receiving frequency synthesizer 14 and the reference frequency of 42 MHz. A demodulator 18 is a demodulator for demodulating and outputting I and Q channel data from a 384 KHz modulated signal applied by the intermediate frequency signal receiver 17, and 19 stores frequency data for each frequency ID. Look-up Table.

In the above configuration, when a predetermined frequency ID is input through the UPH bus, the CUP 12 reads the frequency data corresponding to the corresponding frequency ID into the lookup table 19 to transmit the synthesizer 13 and the receive frequency synthesizer ( 14), the frequency signal (112.512 MHz ± 20 MHz, 112.384 MHz ± 20 MHz) having a variable range of 20 MHz is output-controlled from the corresponding frequency synthesizer.

In the intermediate frequency signal generator 16, a 20 MHz variable is mixed by mixing a frequency signal (112.512 MHz ± 20 MHz) applied from the transmission frequency synthesizer 13 to a 512 KHz modulated signal output from the modulator 15. An intermediate frequency signal (70 MHz ± 20 MHz) having a range is generated, and in the intermediate frequency signal receiving unit 17, a frequency signal having a variable range of 20 MHz is again applied to the intermediate frequency signal having a variable range of 20 MHz (112.384 MHz). By mixing ± 20 MHz), a frequency signal of 384 KHz corresponding to a predetermined communication channel is detected.

On the other hand, the demodulator 18 converts the 384KHz signal input from the intermediate frequency signal receiver 17 into I, Q demodulated data and outputs it by setting the maximum capacity of the filter tap required by the input data. , Will output the Q data.

However, since the input data does not always require the filter tap of the maximum capacity, there is waste of the filter tap when the input data requires a filter tap smaller than the data requiring the maximum capacity.

Accordingly, the present invention has been made in view of the above-described circumstances. In demodulating the data input to the demodulator into I and Q data, the satellite communication can be generated by varying the number of filter taps corresponding to the input data. The purpose of the present invention is to provide a method for generating I and Q data in a demodulator of a channel modem for a system.

1 is a block diagram showing the internal configuration of a channel modem for a general satellite communication system.

Figure 2 is a block diagram showing the internal configuration of the demodulation device 50 in the channel modem according to an embodiment of the present invention.

3 is a diagram showing an internal configuration of a low pass filter 55 of a demodulation device 50 according to an embodiment of the present invention.

*** Explanation of symbols for the main parts of the drawing ***

50: demodulation device, 51: down converter,

52: encoder, 53: quantizer,

54: demodulation section, 55: low pass filter (LPF),

56: synthesizer, 57: matching filter,

58: data message, 59: error estimator,

70: data converter, 80: I data filter,

90: Q data filter.

In the demodulation apparatus for the channel modem for satellite communication system according to the present invention for achieving the above object, the I, Q data generation method, demodulates the modulation frequency signal input from the down converter for downconverting the intermediate frequency signal into a predetermined frequency signal A channel modem demodulation device comprising: a data conversion step of generating a cosine function and a sine function data by multiplying an input modulated frequency signal by a predetermined exponential function; and controlling overall operation of a channel modem operation. The filter tap number setting step of dynamically setting the tap number based on the control data on the number of filter taps according to the characteristics of the data input from the channel unit processor, and the coefficient of the cosine function from the cosine function and the sine function data generated in the data conversion step. I data generation step of filtering and generating I data, and converting the data From a cosine function and a sine function to the data generated by the filter coefficient of the sine function it is characterized in that is configured to include a Q data generation step of generating the Q data.

According to the present invention having the above-described configuration, multiply the input 384KHz data and the exponential function to convert the cosine function and the sine function data, and filter the cosine function coefficient and the sine function coefficient from the converted data, respectively. The coefficient of the cosine function is output as I data, and the coefficient of the sine function is output as Q data.

That is, by dynamically setting the number of filter taps required according to the characteristics of the data input from the intermediate frequency signal receiver, not only is it possible to prevent waste of memory due to unnecessary filter taps, but also the number of filter taps required by the input data is small. In this case, since the number of processing taps is reduced, the processing time of data becomes faster.

Next, an embodiment according to the present invention will be described with reference to the drawings.

2 is a block diagram showing an internal configuration of a demodulation device according to the present invention.

In the figure, reference numeral 51 denotes a down converter that down-converts the intermediate frequency signal transmitted from the intermediate frequency stage (IF stage) to a band of 384 KHz based on a synchronization signal applied from an RX synchronizer (not shown). Where 52 is an encoder that samples the 384 KHz signal applied from the downconverter 51 based on a sampling frequency of 512 KHz, and 53 is a quantizer that quantizes the 128 KHz sampled signal applied from the encoder 52.

Reference numeral 54 is a demodulation unit for synchronously detecting the 128 KHz signal transmitted from the quantizer 53 on the basis of the oscillation frequency applied from the 128 KHz oscillator and converting the signal band to 0 Hz. A low pass filter (LPF) that performs baseband filtering around a reference frequency (0 Hz). The signal passing through the low pass filter 55 is an original signal before both sides of the band are removed and modulated. Q data is output.

Reference numeral 56 denotes a synthesizer which synthesizes and outputs a signal applied from the low pass filter 55 and a signal applied through the error estimator 59 to be described later.

On the other hand, reference numeral 57 is a matched filter for filtering to a band having a predetermined filter coefficient value in order to detect the sampling instant value of the signal applied from the synthesizer 56, which is a route selected by a modulator (not shown). By convoluting the same root-laid cosine function with the signal applied by the las- cosine function, the sampling instant value of the applied signal is detected.

Also, reference numeral 58 denotes a decimator which detects the data applied from the matching filter 57 at predetermined intervals, which has a predetermined size between the information data in a modulator (not shown) on the transmitting side. As a corresponding process of the receiving side in inserting the dummy data and performing the modulation process, if the size of the dummy data is one bit, the decimator 58 of the demodulator is defined to have a detection interval of '2'.

Further, reference numeral 59 detects an error component of data applied from the decimator 58, applies the detected signal to the synthesizer 56, and matches the timing error component data along the satellite. It is an error estimator applied to the filter 57.

3 is a view showing the internal configuration of the low pass filter 55 of the demodulation device 50 according to the present invention.

In the figure, reference numeral 70 denotes a data converter for converting an input frequency signal of 384KHz into a cosine and a sine function (cos, sin) and outputting the same. By multiplying ^{jπn / 2} , a cosine function and a sin function signal are output.

Also, reference numeral 80 denotes an I data filter that outputs I data by filtering and shifting only coefficients of a cosine function in the data output from the data converter 70, which is determined according to the number of filter taps required by the input data. The flexible I data filter tab is set based on the control data applied from the CUP.

In addition, reference numeral 90 denotes a Q data filter for outputting Q data by filtering and shifting only coefficients of sin functions in the data output from the data converter 70, which is based on the number of filter taps required by the input data. The flexible Q data filter tab is set based on the control data applied from the CUP.

In addition, the I and Q data filters have different coefficients of the data, that is, the number of filter taps according to the characteristics of the input data. The number of filter taps of the data according to the characteristics of the data is shown in Table 1 below.

That is, the demodulation device according to the present invention multiplies the input 384KHz data and the exponential function to convert the cosine function and the sine function data, and filters the cosine function coefficient and the sine function coefficient from the converted data, respectively. The coefficient of the cosine function is output as I data, and the coefficient of the sine function is output as Q data.

Therefore, by setting the number of filter taps flexibly on the basis of the number of filter taps required for data input to the I and Q data filters, it is possible to prevent the problem of unnecessary filter taps being set.

In addition, when the number of filter taps required by the input data is small, the number of processing taps is reduced, so that the processing time of data is shortened.

In addition, this invention is not limited to the said Example, It can variously deform and implement within the range which does not deviate from the technical summary of this invention.

As described above, according to the present invention, in the demodulation device for the channel communication system for the satellite communication system, memory waste due to unnecessary filter taps is set by flexibly setting the required number of filter taps according to the characteristics of data input from the intermediate frequency signal receiver. In addition, the number of the processing taps is reduced when the number of filter taps required by the input data is small, so that the processing time of the data is faster.

Claims (1)

A demodulation apparatus for a channel modem for a satellite communication system for demodulating and outputting a modulated frequency signal input from a down converter for downconverting an intermediate frequency signal into a predetermined frequency signal, A data conversion step of generating a cosine function and a sine function data by multiplying an input modulation frequency signal by a predetermined exponential function; A filter tap number setting step of flexibly setting the number of taps based on control data on the number of filter taps according to the characteristics of data input from a channel unit processor for controlling the overall operation of the channel modem; An I data generation step of generating I data by filtering coefficients of the cosine function from the cosine function and the sine function data generated in the data conversion step; In the demodulation device of the channel modem for the satellite communication system, characterized in that it comprises a Q data generation step of generating the Q data by filtering the coefficient of the sine function from the cosine function and the sine function data generated in the data conversion step I, How to generate Q data.

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