KR0147594B1 - Carrier signal generating system - Google Patents

Abstract

The present invention relates to a carrier signal reproducing apparatus, wherein a divider for digitally dividing a pilot signal carried in a modulated signal is divided to divide a signal having an original carrier frequency, and amplify and clip the divided signal. It is possible to accurately demodulate a transmitted signal by providing it as one carrier signal, having a delay time to have a phase difference of π / 2, and then amplifying and clipping the delayed signal as another carrier signal. have.

This is available for reproducing a carrier signal using a pilot signal of the transmitted signal to perform a demodulation operation.

Description

Carrier Signal Reproduction

1 is a block diagram for performing a general modulation and demodulation operation,

2 is a general frequency spectrum of an orthogonal modulated signal,

3 is a block diagram of a carrier signal reproducing apparatus of an orthogonal modulation and demodulation circuit according to the present invention;

4 is a block diagram showing a detailed embodiment of the frequency divider of FIG.

(A)-(e) of FIG. 5 are the partial waveform diagrams of the divider of FIG.

6A and 6B are waveform diagrams showing a carrier signal generated by the present invention.

* Explanation of symbols for main parts of the drawings

2: modulator 4: demodulator

21,22,45,46,59,64: Low pass filter

25,43,50: carrier generator 23,24,41,42: multiplier

26,44,60: phase shifter 27,72: adder

51,55: band pass filter 52,57,62: amplifier

53,58,63: Clipper 54: Divider

71: delay 73: counter

The present invention relates to a carrier signal reproducing apparatus, and more particularly, when demodulating a message signal from a transmitted signal, digitally dividing a pilot signal at a carrier signal frequency and using this digitally divided specific frequency signal. The present invention relates to a carrier signal reproducing apparatus for performing an accurate demodulation operation by reproducing.

Typically, when a signal is transmitted through a medium, the transmission signal is a combination of a message signal and a carrier signal. The message signal is a signal to be transmitted, and the carrier signal is a signal having a specific frequency through which the message signal can pass through a specific medium (eg, air during air transmission). That is, during transmission, the message signal is transmitted after being modulated with the carrier signal, and the transmitted signal is demodulated to remove the carrier signal in order to obtain the original signal.

1 is a block diagram for performing a general modulation and demodulation operation. Here, the modulator 2 and the demodulator 4 are configured. In general, the modulator 2 configured on the transmitting side (transmitting side) includes two message signals f (t1) and f (t2) for modulation. Is passed through a low-pass filter (21), (22) and then applied to one side of the multiplier (23) and multiplier (24), the carrier signal having a predetermined frequency generated in the carrier generator 25 Is applied to the other side of the multiplier 23 while the carrier signal applied to the phase shifter 26 and phase shifted is applied to the other side of the multiplier 24. At this time, the phase shifter 26 shifts the phase of the input signal by π / 2. Therefore, the carrier signal is mixed with the message signal, and in this process, frequency shift occurs in the multipliers 23 and 24, and the signal shifted in the multipliers 23 and 24 is transmitted through the adder 27. do.

In general, the demodulator 4 configured on the receiving side is for demodulating the transmitted signal, and the transmission signal is applied to one side of the multipliers 41 and 42 and the carrier signal generator 43 It is applied to the input side. The carrier generator 43 oscillates a carrier signal using the transmission signal as it is input to the multiplier 41 and then to the phase generator 44. At this time, the signal applied to the phaser 44 is applied to the multiplier 44 after the phase shifts by? / 2. Accordingly, the transmitted signal is demodulated to a desired waveform by passing the low pass filter 45, 46 and the carrier signal by the signal multiplied by the multipliers 41 and 42.

In this case, the orthogonal modulation frequency band is the same as the second degree, and a pilot signal having a frequency twice or three times the carrier frequency fc is generally carried in the modulation process. Accordingly, when the pilot signal synthesized with the signal is input to the carrier generator 43, the carrier generator 43 synchronously generates a carrier signal having the original frequency fc.

However, in the conventional apparatus configured as described above, there was a problem that demodulation could not be performed correctly because the carrier signal was not reproduced at the correct frequency in the carrier generator configured in the demodulator.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to divide a pilot signal for accurate demodulation operation, and to configure a carrier divider in a carrier generator to obtain a carrier signal frequency. The present invention provides a carrier signal reproducing apparatus.

A feature of the carrier signal reproducing apparatus according to the present invention for achieving the above object is that the signal signal is modulated by the carrier signal and the pilot signal having an integer frequency of the carrier signal in the transmitted signal A carrier signal reproducing apparatus for reproducing said carrier signal for demodulating a message signal; Carrier signal generating means for separating the pilot signal from the transmitted signal and performing digital division to output a first sinusoidal signal having a frequency of the original carrier signal; It is composed of a phase variable means for outputting a second sinusoidal wave having a constant phase difference by delaying a digitally divided signal of the carrier signal generating means by a predetermined time.

And, the carrier signal generating means; A first band pass filter for separating and outputting the pilot signal from the transmitted signal; A first amplifier for amplifying a pilot signal separated from the first band pass filter; A first clipper for clipping the amplified signal of the first amplifier to a predetermined voltage level; A divider for digitally dividing the clipped signal of the first clipper at the frequency of the carrier signal, and a second band pass filter for outputting the divided signal of the divider as a sine wave; It may be configured as an output unit for amplifying, clipping and outputting the sine wave of the second band pass filter. And, the divider is; Delay means for delaying a signal output from the first clipper for a predetermined time; Adding means for adding a signal output from said first clipper and a signal output from said delay means to output a pulse having a frequency of said pilot signal; And counting means for digitally counting the pulses output from the adding means and dividing the pulses at the carrier signal frequency. In addition, the output unit; An ideal phaser for outputting a signal of the second band pass filter without a time delay; A second amplifier for amplifying the output signal of the phase shifter; A second clipper for clipping the output signal of the second amplifier to a predetermined voltage level; It may also be configured as a first low pass filter for shaping the output signal of the second clipper.

Meanwhile, the phase variable means; A delay unit for outputting a signal output from the carrier signal generating unit after a time delay such that a? / 2 phase difference is generated; A third amplifier for amplifying the output signal of the delayer; A third clipper for clipping the output signal of the third amplifier to a predetermined sum level; It may also be configured as a second low pass filter for shaping the output signal of the third clipper.

Hereinafter, one preferred embodiment of a carrier signal reproducing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram of a carrier signal reproducing apparatus according to the present invention, and is composed of a carrier generator 50 and a phase generator 60 which can be configured to be opposed to the carrier generator 43, the phase generator 44 of FIG.

The carrier generator 50 has a band pass filter 51, an amplifier 52, a clipper 53, a divider 54, and a band pass filter 55 connected in series, and a band pass. On the output side of the filter 55, an ideal phase 56, an amplifier 57, a clipper 58, and a low pass filter 59 are connected in series, while a phaser 60 is connected.

The phase shifter 60 has a delay 61, an amplifier 62, a clipper 63, and a low pass filter 64 connected in series. The low pass filter 59 has an output signal of the multiplier of FIG. 41), the low pass filter 64 is configured such that an output signal is applied to the multiplier 42 of FIG.

The signal modulated and transmitted by the modulator 2 of FIG. 1 is applied to the pressure side of the multiplier 41 and the multiplier 42 and input to the carrier generator 50.

Accordingly, the bandpass filter 51 of the carrier generator 50 filters the pilot signal carried on the transmission signal, and when the filtered pilot signal is amplified by the amplifier 52 and input to the clipper 53, The clipper 53 clips the input signal to a predetermined voltage level and inputs it to the divider 54.

The divider 54 divides the pilot signal by two or three to output a signal having the original carrier frequency in order to reproduce the carrier signal using the pilot signal transmitted at twice or three times the carrier signal. do. The output signal of the divider 54 is input to the band pass filter 55 to filter frequency signals other than the carrier frequency to output a sine wave having the same frequency as the original carrier signal. In this case, a detailed circuit diagram and an operation description of the divider 54 are described with reference to FIG. 4.

The sine wave output from the bandpass filter 55 is input to the retarder 61 in the phase shifter 56 and the phase shifter 60, respectively.

As the sinusoidal wave input to the retarder 61 in the phase shifter 60 is delayed by the adjustment time, the phase shifts, is transformed into a signal having a phase difference of π / 2 from the original input signal, and then amplified by the amplifier 62. The amplified signal is inputted to the clipper 63, clipped, filtered through the low pass filter 64, and then output.

The sine wave input to the phase shifter 65 is inputted to the amplifier 57 without delay and then amplified and input to the clipper 58. The signal input to the clipper 58 is clipped to a predetermined level and then the low pass filter 59 After filtering through), it is output.

Meanwhile, a detailed circuit diagram of the divider 54 is shown in FIG. 4 and the operation of FIG. 3 will be described in detail with reference to FIGS. 4 and 5.

First, the divider 54 used in this invention shown in FIG. 4 outputs a difference signal between a delay unit 71 for delaying an input signal and an input signal and an output signal of the delay unit 71. The adder 72 and the digital counter 73 which output the frequency-divided signal after counting the output signal of the adder 72 for predetermined periods are comprised. The divider 54 configured as described above is a digital divider using a digital counter.

Accordingly, the pilot signal a1 whose level is clipped is input to the adder 71 and the delayer 72 as shown in FIG. 5A input from the clipper 53 of FIG. 3 and the delayer 71. The signal input to is applied to the adder 72 as a signal b1 delayed in adjustment time as shown in FIG. As the non-delayed signal a1 of FIG. 5 (a) and the signal b1 of FIG. 5 (b) are input, the adder 72 receives the pulse signal of FIG. 5 (c) corresponding to the difference. c1) is input to the counter 73. The counter 73 divides the pulse signal c1 of Fig. 5C into an adjustment frequency which can use this signal as a carrier signal. For example, if the transmitted pilot signal has a frequency twice that of the carrier frequency, the counter 73 divides the input signal into two, and at this time, the output signal outputs a pulse signal d1 as shown in FIG. .

On the other hand, when the pulse signal d1 as shown in FIG. 5 (d) is input to the band pass filter 55, the sine wave signal e1 as shown in FIG. 5 (e) corresponding to the frequency of the pulse signal d1 is outputted. . This sinusoidal wave signal becomes an output signal of the carrier generator 50, and this sinusoidal wave signal is a signal having? / 2th order as in modulation, so that it can be input to the multiplier 41 and the multiplier 42, respectively. The retarder 61 in the phase shifter 60 is input.

Accordingly, the signal a2 output through the phase shifter 56, the amplifier 57, the clipper 58, and the low pass filter 59 is in phase with the signal whose phase is input as shown in FIG. The signal b2 outputted from the phase shifter 50 is a signal having a phase of? / 2 difference as shown in FIG. This is caused by the delay operation of the delay unit 61 configured in the phase shifter 60, and the delay unit 61 is designed such that the output thereof is? / 2 delayed compared to the output of the phase shifter 56.

This is to separate and demodulate the original message signals f (t1) and f (t2) and to demodulate these signals since the two signals were transmitted as carrier signals having a phase difference of π / 2 during modulation.

Especially. In the present invention, since the frequency divider 54 is configured to accurately count the frequency of the carrier signal by using the counter 73 of the digital network type and divide the correct period, the divided signal output from the counter 73 is used. The frequency of the carrier signal generated can be accurate.

On the other hand, the signal of FIG. 6 (a) output from the low pass filter 59 is applied to the multiplier 41 as a carrier signal, and the signal of FIG. 6 (b) output from the phase shifter 60 is a carrier signal. Is applied to multiplier 42 as. Accordingly, the carrier signal carried on the signal transmitted by the carrier signals applied to the multiplier 41 and the multiplier 42 is removed so that the message signal is first passed through the low pass filter 45 and the low pass filter 46, respectively. It is output as a demodulation signal and a second demodulation signal.

As described above, according to the carrier signal reproducing apparatus according to the present invention, as the divider is configured by using a digital counter and a delay unit to generate a carrier signal, a carrier signal of the correct frequency is generated to accurately modulate and demodulate the signal. It has an effect.

Claims (5)

A carrier signal reproducing apparatus for reproducing a carrier signal for demodulating a message signal in a transmitted signal as a message signal modulated by a carrier signal and a paring lot signal having an integer frequency of the carrier signal are transmitted; Carrier signal generating means for separating the pilot signal from the transmitted signal and performing digital division to output a first sinusoidal signal having a frequency of the original carrier signal; And a phase varying means for delaying a digitally divided signal of said carrier signal generating means by a predetermined time to output a second sinusoidal wave having a constant phase difference. 2. The apparatus of claim 1, wherein the carrier signal generating means comprises: a first band pass filter for separating and outputting the pilot signal from the transmitted signal; A first amplifier for amplifying a pilot signal separated from the first band pass filter; A first clipper for clipping the amplified signal of the first amplifier to a predetermined voltage level; A divider for digitally dividing the clipped signal of the first clipper at the frequency of the carrier signal; A second bandpass filter for outputting the divided signal of the frequency divider as a sine wave; And an output unit for amplifying, clipping and outputting a sine wave of the second band pass filter. The apparatus of claim 2, wherein the divider comprises; Delay means for delaying a signal output from the first clipper by a predetermined time; Adding means for adding a signal output from said first clipper and a signal output from said delay means to output a pulse having a frequency of said pilot signal; And counting means for digitally counting pulses output from said adding means and dividing the pulses output at said carrier signal frequency. 3. The apparatus of claim 2, wherein the output unit; An ideal phaser for outputting a signal of the second band pass filter without a time delay; A second amplifier for amplifying the output signal of the ideal phase; A second clipper for clipping the output signal of the second amplifier to a predetermined voltage level; And a first low pass filter for shaping the output signal of the second clipper. 2. The apparatus of claim 1, wherein the phase varying means; A delay unit for outputting a signal output from the carrier signal generating unit after a time delay such that a? / 2 phase difference is generated; A third amplifier for amplifying the output signal of the delayer; A third clipper for clipping the output signal of the third amplifier to a predetermined voltage level; And a second low pass filter for shaping the output signal of the third clipper.