KR0155935B1 - Apparatus & method for recovering carrier having phase jitter tracker - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synchronizing carrier waves in a data transmission and reception system, and more particularly, to a method for reducing phase jitter occurring on a telephone line.

A carrier recovery method having a phase jitter tracker at a receiver that compensates for jitter occurring at a specific frequency on a telephone line includes comparing a phase error signal, setting the signal within a predetermined range, and filtering with a low pass filter; Filtering the introduced error signal into a predetermined band pass region; And summing the low / high pass filtered error signals and further adding carriers to the summed error signals.

The carrier recovery method having a phase jitter tracker according to the present invention effectively compensates for phase jitter occurring at a specific frequency without excessively increasing the bandwidth of the DPLL by using an IIR (infinitive impulse response) type bandpass filter.

Description

Carrier recovery method and apparatus with phase jitter tracker

1 is a block diagram showing a receiver of a typical fax modem stage.

2 is a block diagram illustrating a conventional digital phase locked loop (DPLL) unit.

3 is a block diagram of a DPLL capable of tracking phase jitter in accordance with the present invention.

4 is a flowchart of a carrier recovery method with a phase jitter tracker according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synchronizing carrier waves in a data transmission and reception system, and more particularly, to a method for reducing phase jitter occurring on a telephone line.

In a data transmission / reception system using a general telephone line, a process of synchronizing a carrier of a transmission system and a carrier of a reception system is necessary for recovering transmission data.

In order to synchronize with the carrier, a phase locked loop (PLL) or a band pass filter (PLL) is used in the receiving system. When this process is performed in a digital system, this is performed by a digital phase locked loop (DPLL) or digital. This is called a bandpass filter.

Conventional DPLL can track the random phase when the data rate is 9600bps or less, but as the data rate increases, the MMSE (mimimum mean square error) of the equalizer increases and Because phase jitter occurs at a specific frequency, tracking of the random phase causes a problem of inconsistent synchronization.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the carrier recovery method having a phase jitter tracker having a function of properly matching the phase of a high frequency signal component by tracking jitter on a specific frequency appearing at a receiver when data is transmitted at a speed of 9600bps or higher To provide.

It is another object of the present invention to provide a carrier recovery apparatus having a phase jitter tracker having a function of properly matching the phase of a high frequency signal component by tracking jitter on a specific frequency appearing at the receiving end when transmitting at high speed.

A carrier recovery method having a phase jitter tracker at a receiving end that compensates for jitter occurring at a specific frequency on a telephone line according to the present invention for achieving the above object, compares the phase error signal, set within a predetermined range and a low pass filter Filtering; Filtering the introduced error signal into a predetermined band pass region; And summing the low / high pass filtered error signals and further adding carriers to the summed error signals.

A carrier recovery apparatus having a phase jitter tracker at a receiving end that compensates for jitter occurring at a particular frequency on a telephone line to achieve the other object; A comparator configured to input an error signal generated by the receiver to include an error within a predetermined range; A low pass filter for low pass filtering the signal output from the comparator; A band pass filter unit which inputs an error signal generated by the receiving end and performs band pass filtering to a predetermined frequency range; And a random phase output unit for combining the signals output from the low pass filter and the band pass filter to add a carrier signal and a random phase output unit for combining and outputting the signals output from the carrier adding unit.

Hereinafter, a block diagram of a receiver and a conventional DPLL method will be described to aid in understanding the present invention.

1 is a block diagram showing a receiving apparatus of a general fax modem stage.

The apparatus shown in FIG. 1 includes a demodulation / equalization unit 100, a phase compensator 110, a quantization unit 120, an error calculation unit 130, a DPLL unit 140, and a decoding unit 150. .

Referring to the operation according to the configuration of FIG. 1, the received signal is converted into a digital signal through an A / D converter (not shown), applied to the demodulation / equalization unit 100, demodulated and equalized, and then phase corrected (110). Perform phase correction at Here, the phase correction outputs a phase error signal by introducing the data quantized by the quantization unit 120 and the output signal from the phase correction unit 110 by the error calculator 130. The DPLL unit 140 feeds back the expected error signal to the phase correction unit 110 so that phase correction is performed correctly.

When the phase corrected signal is introduced into the quantization unit 120 and quantized, the error calculation unit 130 outputs a phase error signal to the DPLL unit, and the DPLL unit 140 outputs a phase correction signal to output the phase correction signal. At 110.

2 is a block diagram for explaining a conventional DPLL unit.

When the phase error signal output from the error calculator 230 of FIG. 2 is introduced from the comparator 200 to compare whether the phase error signal is included in the predetermined reference signal range, the phase error signal is out of the reference signal range. After setting, the high pass is blocked by passing through the low pass unit 210, and the low pass filtered signal is added by the carrier adder 220 to output a random phase to correct the phase in the phase compensator 110. At this time, the phase error signal Ψ (n) input to the conventional DPLL can be expressed by the following equation.

Where n is a time index of a specific time and I 'and Q' represent data before quantization and I and Q represent quantized data.

Accordingly, the estimated random phase θ (n) outputted can be represented by the following equation, and Δf represents the channel frequency offset.

In this case, if Δf becomes larger than the bandwidth of the DPLL, the DPLL may not operate normally, resulting in a problem that the random phase generated through the line cannot be tracked.

3 is a DPLL block diagram capable of tracking phase jitter in accordance with the present invention and FIG. 4 is a flowchart of a carrier recovery method with a phase jitter tracker in accordance with the present invention.

The apparatus shown in FIG. 3 includes a comparator 300, a low pass filter 310, a carrier adder 320, a random phase output unit 330, and a band pass filter 320.

In operation 300 of the carrier recovery method having the phase jitter tracker of FIG. 4, in step 300, the error output unit 130 injects the signals output from the phase compensator 110 and the quantization unit 120 to output the phase error signal Ψ. (n) is calculated. In step 310, the phase error signal is introduced from the comparator 300 in the same manner as the conventional method, the phase error signal is set within a predetermined setting range, and the low pass filter 310 is filtered in step 320.

On the other hand, in step 330, when the bandpass filter 340 configured as an infinitive impulse response (IIR) type is subjected to bandpass filtering to receive data transmitted at high speed, jitter on a specific frequency appearing at the receiver through a telephone line is received. In step 340, the band pass filtered signal is added with the low pass filtered error signal and then added with the carrier signal, and then random phase output is performed in step 350.

As described above, the carrier recovery method having the phase jitter tracker according to the present invention effectively compensates for phase jitter occurring at a specific frequency without excessively increasing the bandwidth of the DPLL by using an IIR type bandpass filter. Compensation is provided even when there are multiple jitter components in frequency.

Claims (3)

A method for recovering a carrier having a phase jitter tracker at a receiver that compensates for jitter occurring at a specific frequency on a telephone line, the method comprising: comparing a phase error signal, setting the signal within a predetermined range, and filtering with a low pass filter; ; Filtering the introduced error signal into a predetermined band pass region; And summing the low / high pass filtered error signals and further adding carriers to the summed error signals. A carrier recovery apparatus having a phase jitter tracker at a receiving end that compensates for jitter occurring at a particular frequency on a telephone line; A comparator configured to input an error signal generated by the receiver to include an error within a predetermined range; A low pass filter for low pass filtering the signal output from the comparator; A band pass filter unit which inputs an error signal generated by the receiving end and performs band pass filtering to a predetermined frequency range; A phase jitter tracker comprising: a carrier adder for introducing a signal output from the low pass filter and a band pass filter, adding a carrier signal, and a random phase output unit for combining and outputting a signal output from the carrier adder; Having a carrier recovery device. 3. The carrier recovery apparatus of claim 2, wherein the band pass filter unit is configured of an IIR (infinitive impulse response) type band pass filter.