JPH07193607A - Bpsk demodulation circuit - Google Patents

Abstract

PURPOSE:To prevent the inversion at BPSK demodulation by having only to add a simple configuration component to a receiver side. CONSTITUTION:An input BPSK signal is demodulated by a BPSK demodulator 2. Furthermore, the input BPSK signal is detected by a carrier detection circuit 3, compared with a detection level set by resistors 34, 35 at a comparator 36, which provides a carrier detection output. A one-shot pulse circuit 4 generates a negative pulse having a predetermined pulse width at the leading of the detection output and gives the pulse to an inversion correction circuit 5. A D flip-flop 51 of the inversion correction circuit 5 latches a demodulation signal at said leading of the pulse. The latched high level signal and the demodulation signal are given to an exclusive OR circuit 52, from which a correct demodulation signal with corrected inversion is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a BPSK demodulation circuit capable of preventing an inversion phenomenon during demodulation.

[0002]

2. Description of the Related Art Two-phase PSK (hereinafter referred to as BPS) obtained by two-phase modulation of transmission data with an arbitrary carrier is one of digital communications.
There is a BPSK communication that sends a signal (K).

In the BPSK demodulation circuit for demodulating the BPSK signal, it is not possible to determine whether the reference phase is 0 or π, so that the demodulation signal inversion phenomenon may occur. Conventionally, in order to prevent this inversion phenomenon, a bit previously demodulated on the transmitter side by an encoder using an adder 10 and a delay circuit 11 as shown in FIG. 6 and demodulated on the receiver side is used. Similarly, as shown in FIG. 7, the series is added by an adder 10 and a delay circuit 11.
A method of decoding with a decoder using is adopted.

[0004]

However, in the above method, an encoder and a decoder are required on the transmitting side and the receiving side, respectively, which causes a cost increase.

The present invention solves the above drawbacks,
It is an object of the present invention to provide a BPSK demodulation circuit capable of preventing an inversion phenomenon by simply adding a simple configuration on the receiver side.

[0006]

The present invention is based on a BPSK demodulator for demodulating a BPSK signal, a carrier detection circuit for detecting that the carrier of the BPSK signal is above a predetermined level, and an output of the carrier detection circuit. A pulse generation circuit for generating a pulse having a pulse width shorter than at least the preamble period of the BPSK signal, and the inversion of the BPSK demodulated signal depending on the level of the BPSK demodulated signal in the preamble period of the BPSK signal occurs at the timing of this pulse. An inversion correction circuit that determines whether or not there is an inversion and corrects the inversion when an inversion occurs.
It is a PSK demodulation circuit.

[0007]

According to the present invention, it is determined whether or not the inversion has occurred depending on whether the level of the demodulated signal in the preamble period of the BPSK signal is 1 or 0. If the inversion has occurred, the inversion is corrected and output. By doing so, the inversion can be easily corrected on the receiver side.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the circuit of this embodiment, where 1 is B
An input terminal to which a PSK-modulated BPSK signal is input,
Reference numeral 2 is a BPSK demodulator for demodulating this BPSK signal, 3 is a carrier detection circuit for detecting the presence or absence of carriers of the BPSK signal, and 4 is a one-shot pulse for generating once a pulse having an arbitrary pulse width based on this carrier detection output. circuit,
5 is a D flip-flop 51 and an exclusive OR
An inversion correction circuit composed of the circuit 52, and 6 is an output terminal for outputting the inverted BPSK demodulated signal.

Next, the operation of the above circuit will be described with reference to FIG. First, the preamble part (rising part) of the transmission data a is defined as low. This transmission data is a two-phase modulated BPSK signal b with a carrier of several tens of MHz
Is input to the input terminal 1. This BPSK signal is BPS
Demodulated by the K demodulator 2. If data inversion occurs at that time, the result is as shown in FIG. 3c.

On the other hand, as shown in FIG. 2, the carrier detection circuit 3 includes capacitors 30, 32, a diode 31, and a resistor 23.
(FIG. 3d), the detection level set by the resistors 34 and 35 is compared with the comparator 36, and the carrier detection output e
Is output.

At the rising edge of the output d, the one-shot pulse circuit 4 generates a negative pulse f having a predetermined pulse width and supplies it to the inversion correction circuit 5. In the inversion correction circuit 5, the demodulation signal c at the rising edge of the pulse f is first latched by the D flip-flop 51. The latched high signal and demodulated signal c are exclusively O
By passing the signal through the R circuit 52, the correct demodulated signal g whose inversion has been corrected is output.

When the output of the BPSK demodulator 2 is not inverted, the output of the D flip-flop 51 is low, so the inversion correction circuit 6 outputs the demodulated output as it is without correction.

An embodiment in which the preamble part of the transmission data a is defined to be high is shown in FIGS. 4 and 5. 4 is different from FIG. 1 in that the exclusive O
The only difference is that the inverter 53 is connected to the output of the R circuit 52, and the inversion correction circuit 6 corrects the demodulated signal as shown in FIG. 5c as shown in FIG. 5h.

[0014]

As described above, according to the present invention, the inversion phenomenon can be prevented only by adding a simple structure on the receiver side.

[Brief description of drawings]

FIG. 1 is a block diagram of a BPSK demodulation circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a carrier detection circuit.

FIG. 3 is a waveform diagram of a main part of FIG.

FIG. 4 is a block diagram of a BPSK demodulation circuit according to another embodiment of the present invention.

FIG. 5 is a waveform diagram of a main part of FIG.

FIG. 6 is a diagram showing a conventional encoder.

FIG. 7 is a diagram showing a conventional decoder.

[Explanation of symbols]

 2 BPSK demodulator 3 Carrier detection circuit 4 One-shot pulse circuit 5 Inversion correction circuit

Claims (1)

[Claims] 1. A BPSK demodulator for demodulating a BPSK signal, a carrier detection circuit for detecting that the carrier of the BPSK signal is at a predetermined level or higher, and at least the BP based on the output of the carrier detection circuit.
A pulse generation circuit for generating a pulse having a pulse width shorter than the preamble period of the SK signal, and the BPS according to the level of the BPSK demodulated signal in the preamble period of the BPSK signal at the timing of this pulse.
A BPSK demodulation circuit including an inversion correction circuit that determines whether or not inversion occurs in a K demodulation signal and corrects the inversion when inversion occurs.