JPS6214545A - Noise adding device - Google Patents

Abstract

PURPOSE:To make BER measurement of each carrier possible by inserting noise to a common amplification stage in the reception side of a digital radio communication equipment. CONSTITUTION:A carrier signal to be measured in the reception signal which is branched by a hybrid HYB 7a and passes a buffer amplifier 8a is sent to a control signal generating circuit 5 through a BPF 3b and a switch 4. The random noise which passes a variable gain amplifier 2 from a noise generator 1 passes a variable attenuator 6 and is added to the reception signal by an HYB 7b. The output of the amplifier 2 is branched and is applied to the generating circuit 5 and passes a BPF 3b and is compared with the level of the carrier to be measured to generate a control voltage 102. The generating circuit 5 controls the gain of the amplifier 2 so that detection outputs of square-law detectors 52 and 53 are equal to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a noise adding device, and more particularly to a noise adding device used for measuring bit error rate (BER) in a multi-carrier digital radio line.

[Prior art]

BER@ characteristics are widely used as a method for evaluating the overall characteristics of digital wireless communication devices. This shows the change in BER with respect to the change in the carrier-to-noise power ratio (C/N). Generally, random noise is added to the receiving device using a noise adding device, and the magnitude of this random noise is changed. It is measured by changing the C/N. The range of BER to be measured is about 10-3 to 10-8, and depending on the bit frequency, it takes about 1 minute to several minutes to measure one piece of data, and during this time the C/N is kept constant. It is necessary to keep it. In conventional digital wireless communication systems, one wireless device transmits one carrier wave, so even when measurements are made using an actual wireless line that has been constructed, fluctuations in the received one-novel due to fading are accounted for by AGC. Since it is compensated, it can be easily measured by adding a constant 1/bel random noise to the output side of the AGC.

[Problems to be solved by the invention]

In a multicarrier digital wireless communication system that has been attracting attention in recent years, a plurality of carrier waves (for example, four waves) are arranged in one wireless channel, and these are commonly transmitted and received by one wireless device. Since each carrier wave is independently modulated with a digital signal, the BER needs to be measured for each carrier wave. AGC in such a multi-carrier receiving apparatus is performed not for each carrier but for all carriers in a common amplification stage. That is, although large fluctuations due to fading in the radio section are removed, fluctuations in reception level differences between carrier waves due to selective fading are not compensated for. Therefore, when measuring the BER, it is not possible to keep the C/N constant by adding a constant level of noise to the output side of the human GC amplifier as in the conventional method.

It is also possible to add noise at a stage after being separated into each carrier, but an input G'C and a measurement terminal (connector, hybrid, switch, etc.) for adding noise are required for each carrier. Therefore, it is not economical. SUMMARY OF THE INVENTION An object of the present invention is to solve the problems in the multi-carrier system described above and to provide a noise adding device that inserts noise into a common amplification stage and enables BE measurement for each carrier wave.

[Means to solve the problem]

The noise adding device of the present invention includes a noise generator that generates random noise, a variable gain amplifier that amplifies the output of this noise generator, and separates and extracts one wave from a plurality of commonly amplified multicarrier carrier waves. a bandpass filter; control means for controlling the variable gain amplifier by comparing the output of the bandpass filter and the branch output of the variable gain amplifier;
and output adjustment means for adjusting the output of the variable gain amplifier.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, showing an example of a noise adding device for a 4-line multi-line system. In FIG. 1, reference number 1 is a noise generator that generates random noise, 2 is a variable gain amplifier that amplifies its output, and 3 a
+3b, 3c, r3d are bandpass filters that separate and extract each carrier wave, 4 is a switch that selects one of the outputs, and 5 is a switch that compares the output of the bandpass filter with the branch output of the variable gain amplifier. 6 is a variable attenuator for adjusting the noise output level, 7a and 7b are hybrids, and 8 a p 8 b is an amplifier. This circuit is inserted into the output side of the receiving AGC amplifier and used for one cycle, and the received signal applied to the input terminal 100 is sent from the output terminal 101 to the subsequent stage of the receiving device via the hybrids 7a, 7b and the amplifier 8b. amplifier 8b
is provided to compensate for the insertion loss of the received signal due to the hybrid when the circuit is inserted.

Among the received signals branched by the hybrid 7a and amplified by the buffer amplifier 8a (not necessarily required), the carrier wave signal to be measured is passed through the bandpass filter 3b, for example.
, and is sent to the control signal generation circuit 5 via the switch 4. On the other hand, the random noise generated by the noise generator 1 and amplified by the variable gain amplifier 2 passes through the variable attenuator 6 to the hybrid 7.
b is added to the received signal. The output of the variable gain amplifier 2 is branched and applied to the control signal generation circuit 5, where it is compared with the level of the carrier wave to be measured separated by the bandpass filter 3b, and a control voltage 102 is generated. The control signal generation circuit 5 includes an amplifier 51. It consists of square law detectors 52 and 53 and a differential amplifier 54, and is configured to control the gain of the variable gain amplifier 2 so that the detection outputs of the square law detectors 52 and 53 are equal.

As is clear from the above explanation, when the 17 bells of the measured carrier wave fluctuate, the noise output also fluctuates accordingly.
C/ of the signal sent from the output terminal 101 to the reception demodulator side
N is kept constant. Note that the switch provided between the hybrids 7a and 7b is used when measuring the C/N value on the demodulator side.

The above embodiment is configured to be inserted into the receiving circuit and includes a hybrid for signal branching and noise insertion. They may be configured to be connected in parallel. Further, the variable attenuator 6 for adjusting the noise output may not be provided on the output side as shown in FIG. 1, but may be provided on the noise or carrier signal input side of the control signal generation circuit 5 to control the output.

〔Effect of the invention〕

As described above in detail, the noise adding device of the present invention has the effect of adding noise to the common amplification stage of a multi-carrier wireless device and economically measuring the BER characteristics of each carrier.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, in which reference numeral 1 is a noise generator, 2 is a variable gain amplifier, 3a, 3b
, 3c, 3d are bandpass filters, 4 is a switch, 5 is a control signal generation circuit, 6 is a variable attenuator, 7a #7b is a hybrid, sa, sb, sx are amplifiers, 52.53 is a square law detector, 54 is a Differential Increase Agent Patent Attorney Susumu Uchihara
:Figure 1

Claims (1)

[Claims] A noise generator that generates random noise, a variable gain amplifier that amplifies the output of this noise generator, a bandpass filter that separates and extracts one wave from a plurality of commonly amplified multicarrier carrier waves, and this bandpass filter. Noise characterized by comprising a control means for controlling the variable gain amplifier by comparing an output with a branch output of the variable gain amplifier, and an output adjustment means for adjusting the output of the variable gain amplifier. Additional equipment.