KR20030091525A - The demodulator and the demodulating method for nulling the interference of HAM signal in telephone channel - Google Patents

Abstract

PURPOSE: A receiver for canceling the interference of a HAM signal in a telephone channel and a method for demodulating signals are provided to efficiently cancel the HAM signal in a receiving terminal. CONSTITUTION: A filter circuit(210) receives an analog signal including a HAM signal, performs the notch filtering of the analog signal, and outputs the notch-filtered analog signal. A gain control circuit(220) controls the gain of the notch-filtered analog signal, converts the controlled signal into a digital signal, and outputs the digital signal. A demodulating circuit(230) receives the digital signal, demodulates the received digital signal, and outputs the demodulated signal.

Description

A demodulator and the demodulating method for nulling the interference of HAM signal in telephone channel}

The present invention relates to a receiver and a signal demodulation method in a telephone channel, and more particularly, to a receiver and a signal demodulation method that can be removed by receiving when a ham (HAM) signal is detected at the receiver in the telephone channel.

In case of communication using 10Mbps telephone line channel, the frequency band is 7MHz. In this case, use a frequency band between 5 MHz and 9 MHz. However, it is not possible to perform stable communication in the frequency band, because of the HAM signal present in the 7.15MHz stage.

In general, a ham (HAM) in communication refers to amateur radio communication, and the signal used in such amateur radio communication is called a HAM signal. In addition, a frequency region in which the HAM signal is present will be called a ham band.

Since the HAM signal is characterized as a voice band as an analog signal, its frequency bandwidth is narrow, which exists over a specific frequency. According to the Karl frequency band-plan, the HAM signal may be present at a specific frequency, such as 1.8 MHz, 3.5 MHz, 7 MHz, 10 MHz, and 14 MHz.

FIG. 1 is a graph illustrating a case where a received signal is mixed with a HAM signal in a time domain and a frequency domain. As can be seen in Figure 1, the HAM signal has a narrow and strong signal at 7.15 MHz, which can be removed by a notch filter. As seen from the right time domain, the received signal Rx (t) is a signal including a signal x (t) and a HAM signal HAM (t) to be sent, and the signal filtered by the notch filter is There may be some distortion due to the non-ideal nature of the notch filter.

The HAM signal is noisy when trying to transmit or receive using a telephone line modem, which is a signal that should not be received. However, in a communication using a 10 Mbps telephone line modem, the bandwidth of the band is 7 MHz, and unfortunately, the HAM signal exists inside this bandwidth, which is a great obstacle for stable communication.

Therefore, when received with such a HAM signal, the effect of the HAM signal can be eliminated by notch filtering using a notch filter that forms a frequency null in a specific frequency band of the HAM signal. .

In general, the structure of the receiver requires an automatic gain control (AGC) that adjusts the size of the signal to a range value in which the receiver operates according to the size of the received signal.

However, when the notch filter is used to remove the influence of the HAM signal, there is a problem that the implementation performance of the receiver varies depending on which part of the receiver is located. In order to improve the performance of the receiver, There is a need to implement an appropriate receiver.

Accordingly, an aspect of the present invention is to provide a receiver capable of efficiently removing a received HAM signal at a receiver.

Another object of the present invention is to provide a signal demodulation method capable of efficiently removing a received HAM signal at a receiving end.

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the drawings cited in the detailed description of the invention, a brief description of each drawing is provided.

FIG. 1 is a graph illustrating a case where a received signal is mixed with a HAM signal in a time domain and a frequency domain.

2 is a diagram illustrating a receiver in a telephone line channel according to the present invention.

3 is a flow chart illustrating a receiving method in a telephone line channel according to the present invention.

One aspect of the present invention for achieving the above technical problem relates to a receiver in a telephone line channel. A receiver in a telephone line channel according to the present invention comprises: a filter circuit for receiving an analog signal including a HAM signal, notch filtering the analog signal, and outputting a notched filtered analog signal; A gain control circuit for controlling the gain of the notched filtered analog signal and converting the gain controlled signal into a digital signal and outputting the digital signal; And a demodulation circuit for receiving and demodulating the digital signal and outputting the demodulated signal.

Preferably, the filter circuit includes a HAM signal detection circuit for detecting the HAM signal included in the analog signal and outputting an enable signal; And a notch filter circuit configured to notch filter the analog signal in response to the enable signal and to output the notch filtered analog signal.

Also preferably, the gain control circuit may include: a gain adjusting circuit configured to control the gain of the analog signal and output a gain controlled analog signal in response to the gain control signal; An analog to digital conversion circuit for receiving the gain controlled analog signal and converting the gain controlled analog signal to the digital signal; And a gain control signal generation circuit for outputting the gain control signal in response to the digital signal.

Also preferably, the demodulation circuit includes a baseband conversion circuit for frequency shifting the digital signal into a baseband signal and performing low pass filtering; An equalizer for restoring distortion of an output signal of the filtering circuit; And a carrier reproducing circuit for reproducing a carrier having the same phase as the carrier modulated at the transmitting side.

Another aspect of the present invention for achieving the above technical problem relates to a signal demodulation method in a telephone line channel. A reception method in a telephone line channel according to the present invention includes a filtering step of receiving an analog signal including a HAM signal and notch filtering the analog signal to output a notch filtered analog signal; A gain control step of controlling a gain of the notched filtered analog signal and converting the gain controlled signal into a digital signal and outputting the digital signal; And a demodulation step of receiving and demodulating the digital signal and outputting the demodulated signal.

Preferably, the filtering step includes detecting the HAM signal included in the analog signal and outputting an enable signal; And a notch filtering step of notching filtering the analog signal in response to the enable signal and outputting a notch filtered analog signal.

Also preferably, the gain control step may include: a gain adjustment step of controlling a gain of the analog signal and outputting a gain controlled analog signal in response to the gain control signal; An analog-to-digital conversion step of receiving the gain controlled analog signal and converting the gain controlled analog signal to the digital signal; And a gain control signal generating step of outputting the gain control signal in response to the digital signal.

According to the present invention, a receiver is configured such that a notch filter used to remove the HAM signal is located at the analog signal stage. In addition, the present invention provides a signal demodulation method for performing notch filtering at an analog signal stage.

DETAILED DESCRIPTION In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

2 is a diagram illustrating a receiver in a telephone line channel according to the present invention. Referring to FIG. 2, the receiver 20 in the telephone line channel includes a filter circuit 210, a gain control circuit 220, and a demodulation circuit 230.

The filter circuit 210 includes a notch filter 211 and a HAM signal detection circuit 212. The HAM signal detection circuit 212 receives a predetermined reception signal Rx and detects whether the HAM signal is included in the reception signal Rx. If the HAM signal is included, the HAM signal detection circuit 212 performs the notch filter 211. An enable signal EN for enabling is generated and output to the notch filter 211.

The notch filter 211 notch filters the received signal Rx in response to the enable signal EN, and outputs the result signal F_OUT to the gain control circuit 221.

The gain control unit 220 includes a gain control circuit 221, an analog-to-digital conversion circuit 222, and a gain control signal generation circuit 223. The gain adjusting circuit 221 controls the gain of the notch filtered signal F_OUT in response to the gain control signal GCS and outputs the result to the analog-digital conversion circuit 222.

The analog-digital conversion circuit 222 receives a gain-controlled analog signal and converts it into a digital signal AD_OUT, and the digital signal AD_OUT is input to the gain control signal generation circuit 223.

The gain control signal generation circuit 223 generates a gain control signal GCS in response to the digital signal AD_OUT and outputs it to the gain adjustment circuit 221.

The demodulation circuit 230 includes a baseband conversion circuit 231, an equalizer 232, and a carrier reproduction circuit 233. The baseband conversion circuit 231 frequency shifts the output signal AD_OUT of the analog-digital conversion circuit 222 to a baseband signal in response to the output signal AD_OUT of the analog-digital conversion circuit 222. Low pass filtering is performed by the low pass filter 234 in the bandwidth.

Equalizer 232 restores distortion of the lowpass filtered signal. In addition, the carrier reproduction circuit 233 reproduces a carrier having the same phase as the carrier modulated at the transmitting side in response to the output signal of the equalizer 232.

Referring to Figure 2 describes the operation of the present invention. In response to the received signal Rx, the HAM signal detection circuit 212 detects whether the received signal Rx contains the HAM signal. As a result, when the HAM signal does not exist, the notch filter 211 does not operate and the reception signal Rx is directly input to the gain control circuit 220.

When the HAM signal is present, the HAM signal detection circuit 212 outputs the notch filtering enable signal EN to the notch filter 211, and the notch filter 211 performs notch filtering of the received signal Rx.

The gain F_OUT filtered by the filter circuit 210 is adjusted by the gain control circuit 221. This gain adjustment is made in the gain adjustment circuit 221 in response to the gain control signal GCS generated by the gain control signal generation circuit 223. The output signal of the gain control circuit 221 generates the digital signal AD_OUT by the analog-digital conversion circuit 222. In addition, the demodulation circuit 230 may receive a signal to be sent by the transmitter by demodulating the output signal in response to the output signal of the gain control circuit 220.

In the situation where the HAM signal is dominant in a specific frequency domain, after the HAM signal is removed from the analog stage in advance, the signal is converted into a digital signal and the gain is adjusted by the automatic gain control circuit, thereby converting it into a digital signal and adjusting the gain by the automatic gain control circuit. After that, the output signal having a higher gain can be obtained compared to the case of removing the HAM signal.

3 is a flow chart illustrating a receiving method in a telephone line channel according to the present invention. Referring to FIG. 3, the reception method in the telephone line channel includes a filtering step 310, a gain control step 320, and a demodulation step 330.

Referring to Figs. 3 and 2, the reception method in the telephone line channel according to the present invention is as follows.

The filtering step 310 is a step of receiving an analog signal Rx including the HAM signal, notch filtering the analog signal Rx, and outputting the same, which is performed by the filter circuit 210.

The filtering step 310 detects the HAM signal included in the analog signal Rx and outputs the enable signal EN, and notch-filters the analog signal Rx in response to the enable signal EN. And outputting the result F_OUT. The above steps are performed in the HAM signal detection circuit 212 and the notch filter 211, respectively.

The gain control step 320 controls the gain of the output signal F_OUT, converts the gain controlled signal into a digital signal AD_OUT, and outputs the converted signal. This is performed by the gain control circuit 220.

The gain control step 320 controls the gain of the output signal F_OUT in response to the gain control signal GCS and outputs a gain-controlled analog signal, and receives the gain-controlled analog signal. An analog-to-digital conversion step of converting a gain-controlled analog signal into the digital signal, and a gain control signal generation step of outputting a gain control signal GCS in response to the digital signal AD_OUT.

This gain adjustment step is performed in the gain control circuit 221, the analog-to-digital conversion step is performed in the analog-digital conversion circuit 222, and the gain control signal generation step is performed in the gain control signal generation circuit 223. .

The demodulation step 330 is a step of receiving and demodulating the digital signal AD_OUT and outputting the demodulated signal. This is done in demodulation circuit 230.

As described above, optimal embodiments have been disclosed in the drawings and the specification. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, the receiver and signal demodulation method in the telephone line channel according to the present invention can be effectively removed when the received signal includes the HAM signal by placing the notch filter in the analog stage. Specifically, by placing the notch filter at the analog stage, an output signal having a higher gain can be obtained.

In addition, by placing the notch filter at the analog stage, a signal having a high gain can be obtained in a situation where the HAM signal is dominant, thereby enabling efficient communication.

Claims (7)

A filter circuit for receiving an analog signal including a HAM signal and notch filtering the analog signal to output a notch filtered analog signal; A gain control circuit controlling the gain of the notched filtered analog signal and converting the gain controlled signal into a digital signal and outputting the digital signal; And, And a demodulation circuit for receiving and demodulating the digital signal and outputting the demodulated signal. The method of claim 1, wherein the filter circuit A HAM signal detection circuit for detecting the HAM signal included in the analog signal and outputting an enable signal; And And a notch filter circuit configured to notch filter the analog signal in response to the enable signal and to output the notch filtered analog signal. The gain control circuit of claim 1, wherein A gain control circuit for controlling the gain of the analog signal in response to a gain control signal and outputting a gain controlled analog signal; An analog to digital conversion circuit for receiving the gain controlled analog signal and converting the gain controlled analog signal to the digital signal; And And a gain control signal generating circuit for outputting the gain control signal in response to the digital signal. The method of claim 1, wherein the demodulation circuit A baseband conversion circuit for frequency shifting the digital signal into a baseband signal and performing low pass filtering; An equalizer for restoring distortion of an output signal of the filtering circuit; And, And a carrier reproducing circuit for reproducing a carrier having the same phase as a carrier modulated at the transmitting side. A filtering step of receiving an analog signal including a HAM signal and notch filtering the analog signal to output a notch filtered analog signal; A gain control step of controlling a gain of the notched filtered analog signal and converting the gain controlled signal into a digital signal and outputting the digital signal; And, And a demodulation step of receiving and demodulating the digital signal and outputting the demodulated signal. The method of claim 5, wherein the filtering step A HAM signal detection step of detecting the HAM signal included in the analog signal and outputting an enable signal; And And a notch filtering step of notching filtering the analog signal in response to the enable signal and outputting a notch filtered analog signal. The method of claim 5, wherein the gain control step A gain adjusting step of controlling a gain of the analog signal in response to a gain control signal and outputting a gain controlled analog signal; An analog-to-digital conversion step of receiving the gain controlled analog signal and converting the gain controlled analog signal to the digital signal; And And a gain control signal generating step of outputting the gain control signal in response to the digital signal.