JPH0133063B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a pulse trio detection circuit, and particularly to a pulse trio detection circuit that detects pulses contained in a test pulse signal used for monitoring the speech quality of a repeater in a digital communication system, etc. This invention relates to a circuit that digitally detects a trio signal.

(2) Background of the technology In general, in communication systems that transmit signals using bipolar pulses, testing of each repeater and transmission line or locating fault locations involves applying test pulses to the repeater or transmission line under test. This is done by inputting. As this test pulse signal, a pattern signal is used in which a so-called pulse trio consisting of a pair of double-current pulses and one single-current pulse is repeated for each predetermined bit. Therefore, it is necessary to detect a pattern signal containing this pulse trio at the output side of the repeater under test or the transmission line, but how this detection is performed depends on the configuration and cost of the test equipment such as the repeater. Therefore, an appropriate detection method is required.

(3) Prior art and problems Conventionally, pulse trio detection when testing repeaters, etc. utilizes the fact that low frequency components change depending on the density of pulse trios included in the test pattern signal. This was done by detecting low frequency components with a bandpass filter in a predetermined band.

However, the above-mentioned conventional type requires a pulse trio tester having bandpass filters for various bands and frequencies, which makes the tester configuration complicated, increases the price, and makes it difficult to integrate into an IC. It was hot.

(4) Purpose of the Invention In view of the problems with the conventional type described above, the purpose of the present invention is to detect that a violation of an input bipolar pulse occurs every two input pulses in a pulse trio detection circuit. Based on this concept, it is an object of the present invention to enable a pulse trio to be properly detected using a simple circuit, and to easily integrate the detection circuit into an integrated circuit.

(5) Structure of the Invention According to the present invention, the present invention provides a bipolar-unipolar conversion circuit that converts an input bipolar signal into a unipolar signal, a violation detection circuit that detects bipolar violation of the input bipolar signal, and a violation detection circuit that detects bipolar violation of the input bipolar signal. a counter that counts the output pulses of the bipolar/unipolar conversion circuit and is reset by the output of the violation detection circuit; a decoder circuit that detects that the counted value of the counter is 2; and the output of the decoder circuit and the This is achieved by providing a pulse trio detection circuit characterized by comprising a gate circuit connected to the output of the violation detection circuit and detecting that the number of input pulses between violation pulses is two. Ru.

(6) Examples of the invention Examples of the invention will be described below with reference to the drawings. FIG. 1 partially shows the configuration of a digital communication system that is tested using a pulse trio detection circuit according to an embodiment of the present invention. In the system shown in the figure, a terminal section 3 including a terminal station circuit 1 and a terminal station repeater 2, intermediate repeaters 4 and 5, etc., and another terminal section including a terminal station circuit 1' and a terminal station repeater 2' are provided. Station equipment 3' etc. are connected via relay lines 6 and 7.

In the system shown in FIG. 1, a signal from a terminal, etc. (not shown) is input to the terminal circuit 1 of the terminal device 3, and the signal is converted into a bipolar signal in the terminal circuit 1 and sent to the transmitting amplifier of the terminal repeater 2. 2-1 to the relay line 6. The signal sent to the relay line 6 is relayed via amplifiers 4-1 and 5-1 such as intermediate repeaters 4 and 5, and is received by another terminal device 3'. The signal received by the terminal device 3' is amplified and shaped by the receiving amplifier 2'-1 of the terminal repeater 2' and sent to a terminal (not shown) via the terminal circuit 1'. Similarly, the signal input to the terminal circuit 1' of the terminal device 3' is received by the terminal device 3 via the terminal repeater 2' relay line 7, intermediate repeaters 4 and 5, etc. Terminal circuit 1 amplified and shaped by receiving side amplifier 2-2 of repeater 2
and transmitted to other terminals.

In the above communication system, for example, when determining the error tolerance of the intermediate repeaters 4 and 5, etc., for example, one of the terminal equipment 3
Send out a test pulse signal including the pulse trio PT as shown in . Here, a pulse trio is a 3-bit continuous pulse consisting of a pair of double-current pulses and one single-current pulse, as shown in Figure 2a.
It means PT. As a test pulse signal, a pattern in which this pulse trio PT is repeated every n bits is used, with the polarity reversed at a low frequency (audio frequency) as shown in FIG. 2b.

Conventionally, the above-mentioned test pulse signal does not satisfy the bipolar side and has a DC component within the period of polarity reversal, and therefore has a low frequency component in the long term. They were conducting tests on repeaters, etc. That is, by inputting a test pulse signal as shown in FIG. 2b, for example, to the intermediate repeater under test,
By inputting the output of the intermediate repeater to a bandpass filter of a predetermined band, the low frequency component is detected, and the presence/absence, density, polarity, etc. of the pulse trio is detected from the period, level, etc. of this low frequency component. They were conducting tests on repeaters, etc. However, as mentioned above, this conventional method has the disadvantages that the test equipment becomes complicated and it is difficult to integrate it into an IC.

A pulse trio detection circuit according to an embodiment of the present invention, unlike such conventional methods, digitally detects the presence or absence of a pulse trio.
Figure 3 shows the circuit. The pulse trio detection circuit in Fig. 3 is a bipolar/unipolar conversion circuit 1.
0, bipolar violation detection circuit 11,
Counter 12, OR gate 13, AND gate 1
4, 15, another counter 16, and inverters 17, 18, 19, etc.

FIG. 4 shows waveforms of various parts in the circuit of FIG. 3, and the operation of the circuit of FIG. 3 will be explained below with reference to FIG. Assume that, for example, a pulse trio train as shown in FIG. 4a is applied to the input terminal a of the bipolar/unipolar conversion circuit 10.
The bipolar/unipolar conversion circuit 10 outputs +NRZ when the input bipolar pulse is a positive polarity pulse.
Outputs a positive pulse to the output terminal. Furthermore, when the input bipolar pulse is a negative polarity pulse, a positive polarity pulse is output to the -NRZ output terminal.
Pulses from both of these output terminals are input to the bipolar violation detection circuit 11, and if two or more bits of pulses are continuously input from the same output terminal, for example, the +NRZ output terminal, a violation error pulse is detected. Output. Therefore, if two or more pulses of the same polarity are input in succession in the pulse signal input to the bipolar/unipolar conversion circuit 10, a violation error pulse is output from the output of the violation detection circuit 11. Ru. This violation error pulse is output at the time of the later pulse of the successive pulses of the same polarity, as shown in FIG. 4b. On the other hand, + of the bipolar/unipolar conversion circuit 10
The signals of the NRZ output terminal and the -NRZ output terminal are applied to the OR gate 13, and a unipolar pulse is outputted to the output terminal C of the OR gate 13 as shown in FIG.
It is applied to the counting input terminal IN of 2. counter 1
2 counts the input unipolar pulses and generates an output of each digit at each output terminal Q _A to Q _D. Further, an error pulse from the violation error detector 11 is applied to the clear terminal CLR of the counter 12, and the count value of the counter 12 is cleared to zero by this error pulse. Therefore, assuming that the counting and clearing operations in the counter 12 are performed, for example, at the falling edge of the input signal and the clearing signal, respectively, when a pulse trio train as shown in FIG. 4a is input, a violation occurs. The count value of the counter 12 becomes 2 at the time when the error pulse is generated. That is, the number of unipolar pulses between violation error pulses is two. When the count value of the counter 12 becomes 2, the outputs Q _A , Q _C , Q _D
Both become “0”, that is, low level, and the output Q _B
Only one signal becomes "1", that is, a high level. Therefore, the output d of the AND gate 14 becomes a high level, and the output e of the AND gate 15 to which this output d and the output b of the violation error detector 11 are input becomes "1", that is, a high level, and the pulse trio becomes Detected. The counter 16 generates, for example, a high-level output when the output e of the AND gate 15, that is, a predetermined number or more of detection pulses are input within a predetermined time, and determines a pulse trio due to an error in the transmission line, etc. We are dealing with cases where this is done incorrectly.

(7) Effects of the Invention As described above, according to the present invention, since the pulse trio is detected digitally, the pulse trio detection circuit can be easily integrated into an integrated circuit, and the pulse trio detection circuit can be easily integrated into an integrated circuit. It is possible to reduce the cost of the repeater test equipment by using a bandpass filter or the like in the process, and it is also possible to accurately detect pulse trios.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing the configuration of a digital communication system in which a transmission line, etc. is tested using a pulse trio detection circuit according to an embodiment of the present invention, and FIG. FIG. 3 is a schematic waveform diagram showing the structure of a signal, FIG. 3 is a block circuit diagram showing a pulse trio detection circuit according to an embodiment of the present invention, and FIG. 4 is a diagram for explaining the operation of the circuit in FIG. FIG. 1, 1'... End station circuit, 2, 2'... End station repeater, 2-1, 2'-1, 2-2, 2'-2... Amplifier, 3, 3'... End station section , 4, 5... intermediate repeater,
4-1, 4-2, 5-1, 5-2...Amplifier,
6, 7... Relay line, 10... Bipolar/unipolar converter, 11... Bipolar violation detector, 12... Counter, 13... OR gate, 14, 15... AND gate, 16...
counter.

Claims (1)

[Claims] 1 A bipolar-unipolar conversion circuit that converts an input bipolar signal into a unipolar signal, a violation detection circuit that detects bipolar violation of the input bipolar signal, counts output pulses of the bipolar-unipolar conversion circuit, and converts the input bipolar signal into a unipolar signal. A counter that is reset by the output of the violation detection circuit, a decoder circuit that detects that the counted value of the counter is "2," and a violation detection circuit that is connected to the output of the decoder circuit and the output of the violation detection circuit. 1. A pulse trio detection circuit comprising a gate circuit for detecting that the number of input pulses between pulses is "2".