JPS62116033A - Signal detecting method - Google Patents

Abstract

PURPOSE:To shorten the detecting time of signals regardless of the transmission speed of the signals and band width of a filter, by detecting the presence/absence of the signals by measuring the phase jitter of the received wave of a radio channel and comparing the phase jitter with a reference value. CONSTITUTION:When the power ratio (CNR) between a carrier wave and noise is large, the output of an EX-OR circuit 11 almost becomes zero. When the CNR is small, a jitter quantity is outputted from the EX-OR circuit 11 because the phase trembles. For the AND of the output of the EX-OR circuit 11 the output of a clock 10 is taken at an AND circuit 12 and outputted to a counter 13. When the AND is counted by the counter 13, the jitter quantity can be expressed quantatively. When the jitter quantity measured by means of the counter 13 is compared with the previously set jitter quantity at the time of normal reception at a comparator 14, the presence/absence of a signal can be discriminated. Since the detecting time does not relay on the transmission speed of a control signal and, in addition, no filter is required, the detecting time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a signal detection method for determining the presence or absence of a signal on a radio channel, and particularly to a technique for performing detection in a short time.

<Background Art> Mobile communication is for communicating with mobile objects such as ships and automobiles, and is configured by connecting a base station and a plurality of mobile stations via wireless lines. Since the frequency band that can be used in this communication is limited, a method is adopted in which each mobile station is provided with a plurality of common radio channels and is made to use an empty channel. However, when multiple mobile stations make calls simultaneously on one channel, they may interfere with each other and the base station may not be able to correctly receive signals from any of the mobile stations.

To reduce this probability, when a base station detects a signal sent from a mobile station on a certain channel and determines that it is in use, it broadcasts a signal that prohibits other mobile stations from transmitting on that channel. was.

FIG. 2 is a block diagram showing a conventional circuit for detecting the presence or absence of a signal from a mobile station. As shown in the figure, the IF amplified output amplified by an IF (intermediate frequency) amplifier 1 is demodulated by a demodulator 2 and output to a signal input boot 3, and a preliminary signal detection circuit (hereinafter referred to as a detection circuit) It was outputting to 4.

The detection circuit 4 is.

It detects the preliminary signal for synchronization that is prefixed to the control signal from the mobile station as a low frequency tone signal.

The output of the demodulator is first rectified and integrated by a filter 5 and a rectifier-integrator 6, and the value is compared with a set value by a comparator 7 to detect the presence or absence of a preliminary signal. .

<Problems to be Solved by the Invention> However, even with the above configuration, other mobile stations may Since there is a possibility that the two transmit signals and interfere with each other, it is necessary to shorten the detection time as much as possible to reduce the probability of this happening.

In order to shorten the detection time, it is conceivable to increase the transmission speed of the control signal or to widen the bandwidth of the filter 4. However, the transmission speed cannot be increased indefinitely due to the limitation of the bandwidth for signal transmission, and increasing the bandwidth of the filter 4 increases the noise output of the demodulator 2 and increases the probability of false detection. There was a problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve this problem and provide a signal detection method with short detection time.

Means for Solving the Problems> The present invention provides a signal detection method for determining the presence or absence of a signal on a wireless channel, which measures the phase jitter of a received wave on the wireless channel, and compares the phase jitter with a preset reference value. The determination is made by comparing the measured value with the measured value.

Effect> When the carrier wave power is large, the power ratio of the carrier wave to noise (hereinafter referred to as CNR) is large, and when the carrier wave power is small, the CNR is large.
NR is small. Also, the received wave is equivalently P due to the noise component.
It is in the form of M modulation. That is, when the carrier wave power is large, the phase knock of the received wave is small, and when the carrier wave power is small, the in-phase book is large.

Therefore, the present invention measures the phase jitter of a received wave and compares the value with a reference value to determine the presence or absence of a signal in a wireless channel.

<Example> First, the principle of the present invention will be explained using FIGS. 3 to 5.

FIGS. 3(a) and 3(b) are explanatory diagrams showing the relationship between the carrier signal and noise. FIGS. 3(a) and 3(b) show the case where the carrier signal is small, and FIG. 3(b) shows the case when the carrier signal is large. The received signal at the receiver is a combination of the carrier signal C sent from the transmitter and the noise added in the propagation path.

The distribution of this noise (the range indicated by the broken line in the figure) can generally be approximated to a Gaussian distribution. As can be seen from the figure, the received signal is
The signal is equivalently subjected to PM modulation by the noise R. Fourth
The figure is a time chart showing the waveform of a received signal amplified by a limiter, where A shows the case where the CNR is small and B shows the case where the CNR is large. When the carrier signal C is small and the CNR is small,
A large phase knock occurs as shown by the broken line in the figure.

Therefore, by quantitatively measuring this phase knock, the strength of the carrier wave signal C can be determined.

Next, an embodiment in which the present invention is applied to a base station in mobile communication will be described using FIGS. 1 and 5.

FIG. 1 is a block diagram showing an example of a circuit suitable for implementing the present invention for detecting the presence or absence of a signal from a mobile station, and FIG. 5 is a time chart showing waveforms at each point in the circuit of FIG.

As shown in FIG. 1, the IF amplified by the IF amplifier 1
The amplified output is demodulated by the demodulator 2 and sent to the signal input.
output to port 3.

The IF amplified output is also output to a limiter amplifier 8, and the limiter amplifier 8 outputs it to a shift register 9 and an exclusive OR circuit (hereinafter referred to as gX-OR circuit) 10 (fifth
Figure (b)). Shift register 9 receives the clock from clock 11/? (FIG. 5 (a)), the output of the limiter amplifier 8 is divided by one wavelength, and the EX-OR circuit 10
(Fig. 5 ρ→).

The EX-OR circuit 10 performs an operation on these outputs and outputs it to an AND circuit (hereinafter referred to as an AND circuit) 12 (fifth
In the figure)). When the CNR is large, the output of the limiter amplifier 8 and the output of the shift register 9 are almost in phase,
The output of the EX-OR circuit 11 is approximately O. Also CNR
If is small, there is a fluctuation in the phase, so the value corresponding to the phase jitter (hereinafter referred to as knock amount) is EX-OR.
It is output from the circuit 11.

The output of the EX-OR circuit 11 is combined with the output of the clock 10 by the AND circuit 12 and output to the counter 13 (FIG. 5(E)). By measuring this with the counter 13, the amount of jitter can be expressed quantitatively. Furthermore, by making the output of the clock 10 sufficiently higher than the IF frequency, the accuracy of detecting the amount of jitter can be improved. The presence or absence of a signal can be determined by comparing the amount of jitter measured by this counter 13 with a preset amount of jitter during normal reception using a comparator 14.

Since this implementation has the above configuration, unlike the conventional configuration in which discrimination is made based on the demodulated output, the detection time does not depend on the transmission speed of the control signal because it cannot be discriminated unless several bits are received, and the filter is not used. Since there is no need to go through the process, the detection time can be shortened.

Therefore, there is an advantage that the collision probability of calls from mobile stations can be greatly reduced.

Further, in this embodiment, the jitter amount is measured from the output of the IP amplifier, but a structure in which the amount of jitter is measured from the output of the radio station or the wave amplifier 5 is also conceivable.

Further, if the carrier wave is subjected to PM modulation, PM modulation is applied regardless of the size of CNH.

Therefore, this detection method can be applied in a region where fluctuations in the amount of jitter due to the magnitude of CNR are larger than fluctuations due to PM modulation.

<Effects of the Invention> As explained above, according to the present invention, the presence or absence of a signal is detected by measuring the phase jitter of a received wave in a wireless channel and comparing it with a reference value. This has the advantage that the detection time can be shortened without being affected by the bandwidth of the filter, and the effect of the blank line control can be further enhanced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a circuit for detecting the presence or absence of a signal from a mobile station suitable for implementing the present invention, FIG. 2 is a conventional circuit for detecting the presence or absence of a signal from a mobile station, and FIG. 3 (a)
(b) is an explanatory diagram showing the relationship between the carrier wave signal and noise;
The figure is a time chart showing the waveform of a received signal amplified by a limiter, and FIG. 5 is a time chart showing the waveform at each point in the circuit of FIG. 7: IF amplifier, 8: Limiter, 9: Shifton transistor,
10: Clock, z I: EX-OR circuit, 12
: AND circuit, 13: counter, 14: comparator. Figure 1 Figure 2

Claims (1)

[Claims] In a signal detection method for determining the presence or absence of a signal on a wireless channel, the phase jitter of a received wave on the wireless channel is measured, and the determination is made by comparing the measured value with a preset reference value. A signal detection method characterized by: