KR100305380B1 - Error Compensation Device of Channel Modem for Satellite Communication System - Google Patents

Abstract

The present invention relates to a phase error compensating device in a channel modem for a satellite communication system that can estimate a phase error of data input to a demodulation device.

In the present invention, a demodulation apparatus for a channel modem for a satellite communication system that demodulates an input frequency signal of a predetermined level into I and Q data, and estimates and compensates an error for the I and Q demodulated data. Error detecting means for detecting an error component generated through satellites in the I and Q demodulated data, phase error data extracting means for extracting only phase error data from the detected error data, the extracted phase error data and phase error Data multiplication means for multiplying an estimated coefficient, data synthesizing means for synthesizing the multiplied data and subsequent delayed data, data range limiting means for outputting only data within a predetermined range from the synthesized data, and data range limiting Data delay means for delaying the data applied from the means based on the reference phase data, and the multiplication. And data output means for synthesizing the processed data and the data output from the data range limiting means.

Description

Phase Error Compensation Device for Channel Modem for Satellite Communication System

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel modem of a communication system using satellites, and more particularly, to a phase error compensating device in a channel modem for a satellite communication system, which is capable of estimating a phase error of data input to a demodulation device.

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 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 demodulates a 384KHz signal modulated by the QPSK method into I, Q data, and outputs the demodulated signal. Since the phase is changed due to the distortion of the data, the problem of misinterpreting the information data occurs.

That is, if the phase to be transmitted is 90 ° and the phase is modulated with data as "0,1", if the data is changed to "1,1" for the above reason during the transmission process, the receiver will demodulate this data. It will demodulate in 360 ° phase.

Therefore, in the channel modem for satellite communication system, it is necessary to accurately estimate the phase error value generated through the satellite, and to output data by compensating for the error based on the estimated phase error value.

Accordingly, the present invention was created in view of the above circumstances, and when demodulating the data input to the demodulator of the channel modem, by estimating and compensating for the phase error of the input data, accurate demodulation of the information data can be performed. The purpose of the present invention is to provide a phase error compensation device for a channel modem for a satellite communication system.

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

2 is a block diagram showing an internal configuration of a demodulation device 50 in a channel modem for a satellite communication system according to the present invention.

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

50: demodulation device, 51: error data detection unit,

52: satellite data extraction unit, 53: first multiplier,

54: data synthesizer, 55: limiter,

56: second multiplier, 57: data output unit,

58: data converter.

The phase error compensation device of the channel modem for satellite communication system according to the present invention for demonstrating the above object, demodulates the input frequency signal of the predetermined level into I, Q data, A channel modem demodulation device for estimating / compensating an error and outputting the error, comprising: error detecting means for detecting an error component generated through satellites in the I and Q demodulated data, and a phase in the detected error data; Phase error data extraction means for extracting only error data, data multiplication means for multiplying the extracted phase error data and a phase error estimation coefficient, data synthesis means for synthesizing the multiplied data and subsequent delayed data, the synthesis Data range limiting means for outputting only data within a predetermined range from the received data; And data delay means for delaying the data based on the reference phase data, and data output means for synthesizing the multiplied data and the data output from the data range limiting means.

That is, according to the present invention having the above-described configuration, even if the phase data is changed due to the orbital change of the satellite or the weather worsening, it is estimated and compensated for, thereby reducing the error rate of the data due to the phase error.

Hereinafter, 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 phase error compensation device according to an embodiment of the present invention.

In the figure, reference numeral 51 denotes an error data detection unit for detecting an error component of input data. Although not shown, the error data detection unit 51 detects signal data from data applied from the matched filter means of the demodulator, takes a complex number of the detected data, calculates the magnitude of the signal, and matches the matched filter. The signal applied from the means is obtained by multiplying the signal size data obtained by taking the complex conjugate.

Subsequently, the data output from the error data detection unit 51 is applied as an input of the phase data extraction unit 52, and is output as complex data such as 0 + j1.

On the other hand, the phase data extracting unit 52 extracts only the data corresponding to the phase data from the complex-type error data input from the error data detecting unit 51 and outputs the data to the first multiplier 53 and the second multiplier 56. Done.

That is, if the input error data is 0 + j1, only "1" data which is phase data is extracted here.

The first multiplier 53 multiplies the first phase estimation coefficient arbitrarily set by the system administrator and the data applied from the phase data extracting unit 52 and outputs the input signal of the data synthesizer 54.

On the other hand, the second multiplier 56 multiplies the second phase estimation coefficient arbitrarily set by the system administrator with the data applied from the phase data extracting unit 52 and outputs the data to the data output unit 57.

Here, the first phase estimation coefficient and the second phase estimation coefficient are phase variables that can be arbitrarily set by a system administrator, and are set according to an error increase, such as deterioration of weather conditions, based on statistical values or experimental values. This variable corresponds to the slope of the hour.

Meanwhile, the data applied from the first multiplier 53 is applied as input data of the data synthesizer 54, and the output signal of the data synthesizer 54 is applied as an input signal of the limiter 55.

The limiter 55 is a device that limits the range of input data to within a specific range. For example, the limiter 55 outputs only data within a range of -π to + π from the input data.

On the other hand, the data converter 58 is a data converter which delays the data applied from the limiter 55 based on the reference phase data applied from the open loop of the demodulator, although not shown. After delaying the data by performing, it is output to the data synthesizer 54.

That is, the data is delayed based on the reference phase data until the data is shifted within the data range of the limiter 55, and then synthesized with the data input from the first multiplier 53 to confirm the range of the synthesized data. Done.

On the other hand, when the data input to the limiter 55 is within the range set in the limiter 55, the output data of the limiter 55 is applied to the data output unit 57, from the second multiplier 56 The output signal of the limiter 55 is output as a signal having a slope according to the second phase estimation coefficient by being combined with the input data.

That is, the range of phase data of the limiter 55 is set when designing the system. The range of the setting range of -π to + π is a data range in which no error occurs in the phase data. If the input data is "1,0" and an error occurs by π / 4, it is shifted by π / 4 in the range of the limiter 55, so it is based on the reference phase data. By looping forward, the phase error is estimated and compensated for and transmitted.

Therefore, as described above, even if the phase data is changed due to the change in the orbit of the satellite or the weather worsening, the error rate of the data due to the phase error can be reduced.

On the other hand, the present invention is not limited to the above embodiments and can be modified in various ways without departing from the technical spirit of the present invention.

For example, it can be used as a device for compensating for phase error in a data modulation and demodulation device of a general wireless communication system.

As described above, according to the present invention, even if the phase data is changed due to the change in the orbit of the satellite or the weather worsening, the error rate of the data due to the phase error can be reduced by estimating and compensating for the phase data.

Claims (1)

A channel modem for a satellite communication system which demodulates an input frequency signal of a predetermined level into I, Q data, and performs error estimation / compensation processing on the I, Q demodulated data based on a predetermined phase error estimation coefficient. In the demodulation device, Error detecting means for multiplying the I, Q demodulated data and its conjugate complex number to detect an error component of the data; Phase error data extraction means for extracting only phase error data among the error components detected by the error detection means; Data multiplication means for multiplying the phase error data output from the phase error data extraction means and the phase error estimation coefficient for error estimation; Data range limiting means for outputting only data within a predetermined set phase angle range from the received data; Data delay means for delaying data applied from said data range limiting means a predetermined level based on predetermined reference phase data to generate predetermined delay information; Outputs data applied from the data multiplication means to the data range limiting means, and performs phase compensation processing of input data based on data applied from the data multiplication means and data delay information applied from the data delay means. Phase error compensation device in a channel modem for a satellite communication system, characterized in that it comprises a phase compensation means.