JPS59131233A - Detecting circuit of burst signal - Google Patents

Abstract

PURPOSE:To detect the presence or absence of a burst signal despite the decrement of the input field of the burst signal and the increment of the heat noise power, by providing a means to extract the pre-word part forming the burst signal. CONSTITUTION:A pre-word using various codes is set at the head part of a burst signal for the burst communication. Thus it is possible to transmit the burst signal through a heat noise limiting filter with reduced deterioration of the pre-word part by carrying out a prescribed processing. Furthermore an identifying circuit 12 for wave detection signal holds the burst signal detected by an envelope curve wave detector 2 and a filter circuit 11 for easier processing of the burst signal. Then the burst signal is converted into continuous signals.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides time division multiple access (T
In the DMA) system, a burst signal is installed in a receiving device that receives a digitally modulated wave that has both a prefix word and an information word that follows it, and detects the presence or absence of a burst signal from among the received signals containing the burst signal and thermal noise. The present invention relates to a burst signal detection circuit used to detect and diagnose the operating state of a receiving device.

One of the communication methods suitable for communication systems such as satellite communication systems is the burst communication method. In the burst communication method, a transmission operation is performed only when transmitting information. This burst communication method can reduce the amount of power required, and
It has the advantage of being able to communicate between multiple transmitting and receiving stations using the same satellite and the same frequency band. In such a burst communication system using a satellite (transponder), in order to diagnose the operating state, it is necessary to determine the presence or absence of a Parse I signal and then to determine whether there is a failure in the receiving device. For this reason, conventional receivers perform envelope detection on the received signal that contains a lot of thermal noise as a result of signal power attenuation due to propagation path loss, and peak-hold the envelope detection signal to detect the presence or absence of burst signals. was.

However, if the thermal noise power applied to the envelope detector is large as a result of increased propagation path loss, the thermal noise is envelope-detected even if the burst signal disappears.

Since the peak is held, there is a drawback that it does not provide an alarm signal when the burst signal is interrupted.

In addition, 1. Normally, in order to detect the presence or absence of a signal, the thermal noise frequency band is limited using a filter to reduce the thermal noise power to an equal constraint, and the signal power to thermal noise power ratio (S/ ) By increasing the I ratio), the thermal noise power when the signal is lost is reduced. However, in the digital modulation method applied to burst communication.

The spectrum of the signal itself is expanded and has a certain frequency band, so if you limit the band below that band with a filter, the burst signal power will also decrease, making it impossible to achieve the required S/N ratio. There were drawbacks.

Therefore, an object of the present invention is to provide a burst signal detection circuit that can detect the presence or absence of a burst signal even when the input electric field of the received burst signal decreases and the thermal noise power increases in a burst communication system. .

According to the present invention, in a burst signal detection circuit that is installed in a burst communication receiving device that receives a signal including a burst signal and thermal noise, and that detects the presence or absence of a burst signal from a received signal, means for reducing the power value of the noise; and a prefix () constituting the burst signal.
A burst signal detection circuit is obtained, characterized in that it has means for extracting a preamble word portion.

FIG. 1 shows a conventionally used burst signal detection quald circuit. In the peak hold circuit 3, Xl is a diode for detecting the output v of the envelope detector 2, and C! is a capacitor that holds the voltage, R1 is a resistor that determines the discharge time constant of the held voltage, and 3
-1 is an identification/determination circuit for determining the presence or absence of a burst signal. The received signal l input to the receiving device is transmitted to the amplifier 1.
After being appropriately amplified, it is output as an output signal P, but at that time, the amplification gain of the amplifier 1 is large.

There is generation of thermal noise in the amplifier 1 itself. Part of the received signal p containing this amplified thermal noise is branched and inputted to the envelope detector 2 to detect the presence or absence of a burst signal, and the envelope-detected signal V is sent to the envelope detector 2 by a peak hold circuit. The detected voltage at that time is held, and if there is no burst signal, an alarm signal V is generated. Close and send.

In the circuit configuration shown in FIG. 1 as described above, the received signal p amplified by the amplifier 1 is thermal noise.

As long as the thermal noise power exceeds a certain level, it is determined that a burst signal exists.

The present invention has been made in order to eliminate the drawback of the conventional burst signal detection circuit that it is determined that a burst signal is present when thermal noise exists above a certain level of power as described above.
Focusing on the preamble word that is normally placed at the beginning of the park signal, we inserted a filter into the conventional burst signal detection circuit to limit the thermal noise power, and thereby created a prefix word without error. The purpose is to detect the presence or absence of a first signal by extracting a portion. Namely.

In order to distinguish between burst signals and thermal noise, we focused on their frequency band characteristics and used a filter to pass burst signals with a certain degree of rise response, while limiting the frequency band for thermal noise. The power value is decreased to increase the power difference with the burst signal. Furthermore, there is a prefix word (
As will be described later, we focused on the property that since the sign of the preamble word is fixed, it can be converted to reduce the transient response of the burst signal when it passes through the filter. The purpose of this method is to extract the positional word part and detect the presence or absence of a burst signal.

The present invention will be described in detail below based on the drawings.

FIG. 2 shows the code structure of various burst signals used in the burst communication system.・Guest signal.

It consists of a prefix word and an information word, of which the prefix word is originally provided to quickly perform carrier wave recovery and clock signal recovery in the burst signal demodulation circuit. Therefore, the prefix may be divided into a part for quickly regenerating the carrier wave and a part for quickly regenerating the clock signal component, or it is encoded so that both can be performed at the same time.

In the burst signal shown in FIG. 2, (a) shows a code structure in which only a carrier wave component (CW) for carrier wave recovery is included at the beginning as a prefix word.

At this time, the clock signal is extracted from the following information word portion. (bl is a prefix with a carrier wave component for carrier wave regeneration at the beginning, followed by a
A code consisting of 10 songs (Oπ0 when expressed as a carrier band signal
(corresponding to a phase-modulated signal), (C) shows the installation order of the information word and the code for re-using the clock signal in (b). The reverse case is shown (d-1).

(d-2) is a burst signal ' mainly applied to burst communication for multilevel orthogonal modulation of four or more phases.

As shown in (d-1), when carrying out orthogonal modulation of carrier waves, for example, the parallel channels are only carrier wave components consisting of codes 111..., and the orthogonal channels are 1010...
This is a case where the signal is used for reproducing a clock component consisting of the codes .

As shown in Figure 2 above, in burst communication, prefix words using various codes are placed at the beginning of the burst signal, but one thing in common is that which burst Since the sign of the prefix is fixed in the signal as well, it can be parsed by performing certain controlled processing.

FIGS. 3 and 4 are block diagrams showing the configuration of an embodiment of a burst signal detection circuit according to the present invention.

Referring to FIG. 3, 1 and 2 are an amplifier and an envelope detector, respectively, as in FIG. 1, and 11 filter circuits are added for limiting thermal noise power.

12 is an envelope detector 2. A circuit for holding the burst signal detected by the filter circuit 11 to facilitate processing and converting it into a continuous signal is used.
In the example shown in this figure, the same peak hold circuit as in FIG. 1 is applied. However, it goes without saying that this circuit can be realized by other means (eg digital processing circuits).

FIG. 3(b) shows the envelope detector 2 in FIG. 3(a).
The installation position of the filter circuit 11 is reversed.

This is an embodiment in which a filter 11 for limiting thermal noise is inserted in the carrier band.

In part, FIG. 4 shows an example in which an envelope detector 2 is used instead of the envelope detector 2 in FIG.
This is an example when the phase detection circuit 13i is used, and the fifth
The figure shows a specific example of the phase detection circuit 13.

FIG. 5(a) shows the case where a 1-bit delay circuit 13-1 and a phase comparison circuit 13-2-i are used as the phase detection circuit 13 (
Here, a 1-bit delay means a time corresponding to the time length of one code. ), and Fig. 2 (a-1) (a-2
) The burst signal shown in (b) is input to the 9 phase detection circuit 13.
As a 2-bit delay circuit 13-3 and a phase comparator circuit 13-
Fig. 2 fb), fc
) By inputting the burst signal shown in ), the prefix part of the burst signal can also be converted to a DC signal. Furthermore, FIG. 5(e) is similar to FIGS. 2(a) to (d).
FM detector 13-4, which can be applied to any burst signal of the 9-phase detector circuit 13, and which can extract the carrier signal component of the prefix word as a burst DC signal; This is an example using 'z.

As described above, in the burst mail detection circuits of the present invention shown in FIGS. 3 and 4, the filter 11 is used to limit the thermal noise power, and the prefix part of the burst signal is If you extract it as a signal and hold it, you will get . Here, when the filter 11 is installed in the carrier band as in the case of FIG. 3 (bl) and FIG. 4 (a),
The part of the prefix code that corresponds to the carrier wave (carrier waveform (CW)).

In terms of codes, it is suitable for detecting signals that follow the same code (1111...). Furthermore, in the case of a circuit in which the filter 11 is inserted after the phase detection circuit 13 as shown in FIG. 4(b), there is a feature that the clock signal reproduction code part of the prefix word can also be converted into a burst DC signal. In this case, even if the pass band of the filter 11 is narrowed so as to limit the thermal noise power more tightly, the deterioration of the prefix detection signal V' can be reduced.

The above will be explained with reference to the operational waveform diagram shown in FIG. FIG. 6 (al is 1) For example, FIG. 4(b) shows the waveform of the output V of the phase detection circuit 13, where the waveform portion where the prefix of the burst signal is detected is Vs, and the portion where thermal noise is detected is vN.
, and its detection and voltage are respectively vs + vN
It is shown in H. At this time, the detected signal identification circuit 12 identifies the presence or absence of a burst signal with a voltage '(i=V+H. In the circuit shown in FIG. 1).

Since the peak of the signal V shown in FIG. 6(a) is held as it is, both *vs+vN and VTI+ are exceeded.

Therefore, the presence or absence of a burst signal cannot be determined.

Also, if Vs' and vN are approximately the same voltage, and V
In cases similar to TI, stable identification is still not possible.

On the other hand, as shown in FIG. 4(b), the waveform V' is shown in FIG. 6(b) when the thermal noise power of the signal v is band-limited using the filter 11. As shown in the figure.

Thermal noise voltage ■N' is much lower than VTI+, making it easier to identify, but the waveform v j where the prefix part is detected
The startup time will also be longer due to the transient response. In order to prevent Vs from deteriorating even if this rise time becomes longer, the DC signal time TB of v8 shown in Fig. 6(a) must be set.
It is better if the length is longer, in which case it becomes possible to detect burst signals more stably. In addition, FIG. 6(e) shows the state of FIG. 4(b) when it is determined that there is a burst signal.
) output V of the detected signal identification circuit 12. If this time is set to a high level (H), for example, when it is determined that there is no burst signal, +(iv.) becomes a low level (L) as shown in FIG. 6(d). Serves as a warning signal for burst signal disconnection.

As explained above, according to the present invention, in a burst communication system, even if the propagation path loss increases and the receiving device input decreases equivalently, the Gust signal can be detected without any problem. be.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of a conventionally used burst signal detection circuit, Figure 2 is a code configuration diagram of various burst signals used in the burst communication system, Figures 3 and 4.
The figure is a block diagram showing an embodiment of the burst signal detection circuit according to the present invention, FIG. 5 is a block diagram showing a specific embodiment of the phase detection circuit of FIG. 4, and FIG. FIG. 3 is a waveform diagram for explaining the operation of FIG. DESCRIPTION OF SYMBOLS 1...Amplifier, 2...Envelope detector, 3...Peak bold circuit, 3-1...Identification determination circuit, 11...Filter circuit, 12...Detected signal identification circuit, 13...・
Phase detection circuit, 13-1...1 bit delay circuit, 13
-2... Phase comparator circuit, 1-3-3... 2-bit delay circuit. 13-4...FM detector + X l...diode. Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. In a burst signal detection circuit that is installed in a burst communication type receiving device that receives a signal including a burst signal and thermal noise and detects the presence or absence of the burst signal from the received signal, A burst signal detection circuit specially designed to include means for reducing a power value and means for extracting a prefix part constituting the burst signal.