JPH0580988B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to noise measurement of digital signals received by digital radio, and particularly to selection of digital signals in diversity reception or processing of received digital signals. This invention relates to noise measurement for obtaining squelch signals.

(Prior Art) Conventionally, in order to compare the quality of digital signals (for example, bit error rate) in diversity reception, or to obtain a squelch signal for the received digital signal, the quality of the received signal is compared with the received field strength, Alternatively, a method of knowing by measuring out-of-band noise of a received signal is known.

(Problems to be Solved by the Invention) In the conventional technology, the received digital signal and the measurement result of its quality do not necessarily correspond, resulting in the following problems 1 to 3. .

The first problem is that when conventional methods are applied to squelch signal detection, when the receiver receives urban noise or interference waves, it is difficult to distinguish them from the desired signal, and the squelch signal is erroneously responded to. The problem is that even though it is not a wave, it is processed incorrectly.

The second problem is that when detecting a squelch signal, the error rate of the received digital signal and the received field strength vary somewhat depending on the receiver (usually within a range of several dB). The squelch signal responds even when the electric field strength is low and the quality of the digital signal is poor.

The third problem is that when measuring the quality of digital signals using the conventional method at two receivers,
If diversity reception is performed in which the output of the receiver is selected using these results, the field strength measurement results and error rate may vary due to variations in urban noise, interference waves, or variations in the characteristics of the receiver itself. Therefore, the one with better received signal quality is not necessarily selected, and the diversity effect deteriorates.

The above problems occur not only when measuring the received electric field strength but also when measuring out-of-band noise of the received signal.

Furthermore, when measuring the received electric field strength, it is necessary to use an expensive device such as a logarithmic amplifier in order to obtain a voltage proportional to the received electric field strength.

The object of the present invention is to pass the received signal through a high-pass filter, input it to a rectifier circuit to obtain a signal wave containing a clock frequency component, and then input the output of the rectifier circuit to a clock pulse regeneration circuit to regenerate the clock pulse. In the receiving device, regarding the output of the rectifier circuit, a first measurement result obtained by sampling the time point when the probability of the amplitude being the maximum is highest, and a second measurement result obtained by sampling the time point when the probability that the amplitude becomes the minimum value is highest. An object of the present invention is to provide a noise measuring device configured to eliminate the above-mentioned drawbacks by comparing and passing the comparison results through a low-pass filter, and to obtain an output voltage corresponding to the noise contained in the received signal. .

(Means for Solving the Problems) A noise measuring device according to the present invention is configured to include a clock generating means, first and second sampling/measuring means, and an identifying means.

The clock generation means is for passing the high frequency component of the received signal and rectifying it to generate a signal wave containing the clock frequency component, and further regenerating the clock frequency component from the signal wave.

The first sampling/measuring means is for measuring the amplitude of the rectified output by sampling the time point at which the probability of the amplitude being the maximum is highest.

The second sampling/measuring means is for measuring the amplitude by sampling the time point where the probability of the amplitude being the minimum is highest.

The identification means includes first and second sampling/
The measurement results obtained by the measurement means are compared with each other to obtain a comparison result, and only the low-frequency components thereof are passed to obtain a voltage corresponding to the noise contained in the received signal.

(Example) Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a noise measuring device according to the present invention. In Figure 1, 1
is the receiver, 2 is the low frequency device, 3 is the high frequency device, 4
5 is a rectifier circuit, 5 is a band waver, 6 is a comparator, 7 is an identification circuit, 8 is a delay circuit, 9 is a sampling pulse generation circuit, 10 is a sample hold circuit, 11
12 is an inverter, 12 is a sampling pulse generation circuit, 13 is a sample hold circuit, 14 is a comparator, 15 is an integrating type low-frequency wave generator, and 16 is a comparator.

FIG. 2 is an explanatory diagram showing operation waveforms of each part in FIG. 1.

In FIG. 1, the output received by a receiver 1 is passed through a low frequency filter 2 to remove noise and obtain a received signal _x2 . As shown in Fig. 2, the signal x ₂
This shows that the eye pattern is open. Furthermore, in order to obtain a clock frequency component, the signal x ₂ is inputted to a rectifier circuit 4 through a high frequency converter 3, and is rectified by the rectifier circuit 4. Since the output of the rectifier circuit 4 includes a clock frequency component, the clock frequency component is extracted by a bandpass filter 5 and further compared with a reference voltage Vc ₁ by a comparator 6.

This rectifies the waveform and provides ₆ regenerated clock pulses.

Next, use ₆ regenerated clock pulses to convert the received signal.
x ₂ is identified by the identification circuit 7, and the identification circuit 7 outputs the received digital signal x ₇ .

In the noise measuring device described above, the following can be said about clock pulse reproduction.

As shown in Fig. 2, when the received signal x ₂ does not contain noise, the output x ₃ of the high frequency converter 3
There are phase points (t ₁ , t ₂ , t ₃ in FIG. 2) where the amplitude becomes very small between the output x ₄ of the rectifier circuit 4 and the output x 4 of the rectifier circuit 4. In the present invention, noise measurement results are obtained by measuring to what extent such waveform properties are maintained. In the sample-and-hold circuit 10, the waveform of the signal x ₄ is sampled by a sampling pulse x ₉ at the time points (for example, t ₁ , t ₂ , t ₃ ) when the amplitude is the smallest. On the other hand, the signal
The x ₄ waveform is sampled by the sample-and-hold circuit 13 at the times when the amplitude is the highest due to the sampling pulse x ₁₂ (for example, t ₁ ', t ₂ ', t ₃ ').

The delay circuit 8 and the sampling pulse generation circuit 9 are used to generate sampling pulses in the sample hold circuit 10. A delay circuit 8 appropriately delays the clock pulse x ₆ , and a sampling pulse generating circuit 9 outputs a sampling pulse x ₉ having a minute pulse width in synchronization with the rise of the output x ₈ of the delay circuit 8.
Here, the delay amount of the delay circuit 8 is adjusted in accordance with the time points such as t ₁ , t ₂ , and t ₃ in x ₄ when the delay amount becomes minimum with respect to the rising edge of the sampling pulse x ₉ .

The inverter 11 and the sampling pulse generation circuit 12 are used to obtain a sampling pulse for the sample hold circuit 13. The inverter 11 inverts the signal _x8 , and the sampling pulse generation circuit 12 inverts the signal x8 in synchronization with the rise of the signal _x8 . It outputs ₁₂ sampling pulses with a minute pulse width. Therefore, the temporal position of signal x ₁₂ is exactly at the center point of each pulse of signal x ₉ , at which point the waveform of signal x ₄ reaches its peak value.

As shown in FIG. 2, when the signal x ₄ contains no noise, the result x ₁₀ sampled by the sample-and-hold circuit 10 has a zero level as shown by the solid line. The result x13 sampled by the sample and hold circuit ₁₃ shows a high value depending on the level of the signal _x4 . Therefore, when signal x ₄ does not include noise, x ₁₀ <x ₁₃ always holds between signal x ₁₀ and signal x ₁₃ . Therefore, when the signal x ₁₀ and the signal x ₁₃ are compared by the comparator 14, the output x ₁₄
is always at a high level. However, if the signal x ₄ contains noise, the above relationship does not necessarily hold. As shown by the dotted line in Fig. 2, when noise is added to the signal x ₄ , △V ₁ , △V ₂ ,
Sample △V ₃ , ... and apply the voltage △V ₁ , to the signal x ₁₀
△V ₂ and △V ₃ occur.

At this time, signal x ₁₃ is not necessarily at a high level even when compared with the above voltage, so as a result of comparing signal x ₁₀ and signal x ₁₃ , the signal
As shown by the dotted line in the x ₁₄ waveform, the level becomes low with a certain probability. That is, when the signal x ₄ does not include noise, the signal x ₁₄ always has a high level, and the probability that the signal x 14 shows a low level tends to increase depending on the degree of noise. Therefore, if the signal x ₁₄ is passed through the low frequency filter 15 to remove the pulse-like fluctuations, a voltage x ₁₅ corresponding to the noise contained in the signal x ₄ can be obtained. Here, if there is noise in the received signal x ₂ , the waveform of the signal x ₄ will be disturbed accordingly, and the measurement of the noise in the signal x ₄ can be understood as measuring the noise in x ₂ .

As described above, in the present invention, the received signal
The noise contained in x ₂ is measured.

Next, in the comparator 16, the output of the low frequency converter 15 is
When _x15 becomes smaller than a certain value _Vc2 , this is regarded as a noise condition and the output SQ is lowered to a low level. That is, SQ is used as a squelch signal to output a low level when the receiver 1 does not receive a normal signal and the eye pattern of the received signal output is not open. In this case, no signal processing is performed on the output _x7 of the identification circuit 7.

(Effects of the Invention) As explained above, the present invention passes a received signal through a high-pass filter, inputs it to a rectifier circuit to obtain a signal wave containing a clock frequency component, and further reproduces a clock pulse from the output of the rectifier circuit. In a receiving device that regenerates a clock pulse by inputting it to a circuit, the first measurement result is the sampling of the time when the output of the rectifier circuit has the highest probability of maximum amplitude, and the first measurement result of sampling the time of highest probability of minimum amplitude. By comparing the second measurement result and passing the comparison result through a low-pass filter, it is possible to measure the noise included in the eye pattern of the received signal.
There are the following first to fourth effects corresponding to the bit error rate.

First, there is a case where the eye pattern of the received signal does not open to urban noise, interference waves, etc., and there is an effect that the received signal is determined to be noise and measured. As a result, the conventional problem of erroneously outputting a response due to a squelch signal is solved.

Second, even if there are variations in receiver performance, a squelch response signal corresponding to the bit error rate can be obtained.

Thirdly, the present invention is applied to diversity reception, in which the measurement results of noise included in the eye patterns of the respective received signals of two receivers are compared with each other. , it is possible to reliably select a signal with a low error rate. Therefore, the diversity effect does not deteriorate as in the conventional case.

Fourth, the present invention has the effect that the circuit configuration is extremely simple, and there is no need to use expensive devices such as logarithmic amplifiers as in the conventional electric field strength measurement method. Therefore, it is advantageous in terms of price.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a noise measuring device according to the present invention. FIG. 2 is a waveform explanatory diagram showing operating waveforms of each part of the noise measuring device shown in FIG. 1. 1... Receiver, 2, 3, 5, 15... Wave device,
4... Rectifier circuit, 6, 14, 16... Comparator, 7
... Identification circuit, 8 ... Delay circuit, 9, 12 ... Sampling pulse generation circuit, 10, 13 ... Sample hold circuit, x ₂ - x ₁₀ , x ₁₂ - x ₁₅ , SQ ...
Signal, △V ₁ , △V ₂ , △V ₃ , Vc ₁ , Vc ₂ ... Voltage,
t ₁ , t ₁ ′, t ₂ , t ₂ ′, t ₃ , t ₃ ′...time.

Claims (1)

[Claims] 1. Clock generation means for passing a high frequency component of a received signal and then rectifying it to generate a signal wave including a clock frequency component, and further reproducing the clock frequency component from the signal wave, and an output of the rectification. a first sampling/measuring means for measuring the amplitude by sampling a point in time when the probability that the amplitude is the highest is highest; A second sampling/measuring means is used to compare the measurement results of the first and second sampling/measuring means to obtain a comparison result, and only the low-frequency components thereof are passed through to form the received signal. 1. A noise measuring device comprising: identification means for obtaining a voltage corresponding to included noise.