KR970007873B1 - Bpsk demodulation circuit - Google Patents

Abstract

A BPSK demodulation circuit is provided to improve a stability of the circuit. The demodulator comprises: a low noise amplifier(20) for amplifying a demodulated signal; a first and a second band pass filter(60,70) for detecting a first band and a second band; a first and a second envelope detector(80,90) for envelope detecting the detected signal; a first and a second limiter(100,110) for limiting the detected signal from the first and second envelope detectors; and a flip-flop(120) for restoring the limited signal from the limiter(100,110).

Description

BPSK Demodulation Circuit

1 is a block diagram according to the present invention.

2 is a conventional BPSK demodulator.

3 is an operational waveform diagram according to the present invention.

* Explanation of symbols for main parts of the drawings

10: antenna 20: amplifier

30,40: First and second band pass filter 50,60: First and second envelope detectors

90: R.S latch

The present invention relates to a demodulation circuit of the present invention, and more particularly, to a biphase shift keying (BPSK) demodulation circuit.

The present invention discloses that when a BPSK modulator having a flat envelope disclosed in patent applications 90-15940 and 91-1299, which is disclosed herein, is phase-modulated while having any flat data with a flat envelope, It is invented to receive this.

Prior to the invention of BPSK modulators such as Patent Applications Nos. 90-15940 and 91-1299, BPSK demodulators as in FIG.

The BPSK demodulator of FIG. 1 receives a signal propagated by an arbitrary BPSK modulator through the antenna 10 and sufficiently increases a weak signal in the low noise amplifier 20 and applies it to the mixer 50. At the same time, in the multiplier 30, the output of the low noise amplifier 20 is branched, multiplied, and applied to the divider 40, and the divider 40 divides it by 1/2 and applies it to the mixer 50. Do it.

Therefore, when the mixer 50 receives the output of the low noise amplifier 20, the mixer 50 receives the output of the divider 40 at the same time. At this time, the mixer 50 removes the carrier by mixing the output of the sieve 40 and the output of the low noise amplifier 20 and restores the original signal by synchronous detection.

However, the demodulator of FIG. 1 can sufficiently demodulate a signal modulated by a conventional BPSK modulator, but a signal modulated and transmitted by the modulators disclosed in the above-described patent applications Nos. 90-15940 and 91-1299. You cannot demodulate.

Accordingly, an object of the present invention is to provide a BPSK demodulation circuit capable of demodulating a BPSK modulated signal to have a flat envelope.

In order to achieve the above object, the present invention provides a low-noise amplifier (20) for receiving low-noise amplification of a signal transmitted by BPSK modulation, and receiving the output of the low-noise amplifier (20) to in-phase signal components or quadraise signal components. First and second band pass filters 60 and 70 for detecting first and second band signals included therein, and first and second envelope detection for signals detected by the first and second band pass filters 60 and 70, respectively. The first and second limiters 100 and 110 which limit the signals detected by the two envelope detectors 80 and 90, the first and second envelope detectors 80 and 90 to predetermined levels, and the first and second limiters The flip-flop 120 is configured to receive the signal limited by the 100 and 110 and finally restore the original signal.

Hereinafter, the present invention will be described in detail based on the above configuration.

First, a modulation signal transmitted from Patent Application Nos. 90-15940 and 91-1299 (hereinafter referred to as 'Pre-Application') previously filed herein will be briefly described with reference to FIG.

In the above-mentioned application, the digital data as shown in (1) of FIG. 3 to be transmitted is shaped as (2) and (3), respectively. Here, when the digital data (1) to be transmitted is transitioned, (2) and (3) are represented by the equation, (2) is represented by ± sin 2πf _s t, and (3) is represented by the form of cos2πf _s t, respectively. Can be.

When the shaped signals (2) and (3), i.e., the in-phase signal and the quad-raise signal, are f (t) and g (f), respectively, Z (t) is Z when the modulated signal is Z (t). It can be expressed as (t) = f (t) cos 2πfct + g (t) sin 2πfct. In FIG. 3, (4) shows Z (t), and since the envelope of this signal is always constant, the spectrum does not change even when amplified by a nonlinear amplifier. Here, when calculating the instantaneous frequency of the modulated signal Z (t), when the original digital data 1 transitions from "low" to "high", that is, in the section I, III of FIG.

Z (t) = sin 2πf _s tcos 2πf _c t + cos 2πf _s t

= K sin {2πft + tan (tan 2πft)}

= K sin (2πf _c t + 2πf _s t)

= K sin {2π (f _c + f _s ) t}

In this case, the instantaneous frequency f _z = f _c -f _s is obtained, and on the contrary, when the original digital data 1 transitions from "high" to "low", that is, in section II of FIG.

Z (t) = sin 2πf _s tcos cos 2πf _c t + cos 2π _k f _s t + sin 2πf _c t

= K sin {2πf _c t + tan ^-1 (-tan 2πf _s t)}

= K sin (2πf _c t + 2πf _s t)

= K sin {2π (f _c + f _s ) t}

Therefore, the instantaneous frequency f _z = f _c -f _s becomes. In this case, f _c + f _s is defined as f _H , and f _c -f _s is defined as f _L.

Therefore, when the pre-priority BPSK modulates the original digital data signal 1 of FIG. 3, the frequency to be changed at the time of data transition to the output modulation signal is f _H or f _L.

In the present invention, it is immediately focused on the advantages.

In other words, in view of the fact that the frequency of the modulated signal changes every data transition of the original digital signal 1, the received modulated waveform can be demodulated using two band pass filters having a center frequency at f _H · f _L. To help.

After passing the received modulation waveform through the first and second band pass filters 60 and 70 having a center frequency of f _H · f _L , the envelope is detected through the first and second envelope detectors 80 and 90 and then When the limit is passed through the first and second limiters 100 and 110, the waveforms output from the first and second limiters 100 and 110 become as shown in FIGS. 7 and 8 of FIG. 3. At this time, if the two signals (7) and (8) are respectively applied to the R and S input terminals of the RIP Spool pull-flops 120, which are R and S pull-flops, respectively, the raw data is restored and output.

Therefore, the present invention can sufficiently demodulate when transmitting the one data by modulating the first application so that the first application has a flat envelope. In addition, the present invention has the advantage that the combination of the above-described application with the disadvantage that the conventional BPSK demodulator, that is, zero crossing distortion and the like can be sufficiently solved.

Claims (1)

A demodulation circuit comprising: a low noise amplifier (20) for receiving low noise amplification of a signal transmitted by BPSK modulation, and a first phase and a second phase including a in-phase signal component or a quad-raise signal component simultaneously receiving the output of the low noise amplifier 20; First and second band pass filters 60 and 70 for detecting band signals, and First and second envelope detectors 80 for envelope detection of signals detected by the first and second band pass filters 60 and 70, respectively. 90 and the first and second limiters 100 and 110 limiting signals detected by the first and second envelope detectors 80 and 90 to predetermined levels, respectively, and the first and second limiters 100 and 110 respectively. BPSK demodulation circuit comprising a flip-flop (120) for receiving a signal and finally recovering the original signal.