JPS635663A - Discrimination level setting system - Google Patents

Abstract

PURPOSE:To always set an optimum discrimination level regardless of any distortion of a transmission line by sequentially leveldiscriminating reception data at preset plural levels, obtaining the number of errors arising in the discriminated output data and setting the level having the minimum number of errors among all levels as a discrimination level. CONSTITUTION:If error detection data is periodically insert into data series in terms of the reception data, an error detection circuit 6b detects errors. Namely, reference data the same as the error detection data is previously stored in a reference data storage circuit 8. Among output data from a discrimination circuit 4, the error detection data is stored in a reception data storage circuit 7. A comparator circuit 9 compares the error detection data from the reception data storage circuit 7 with reference data from the reference data storage circuit 8, detects the number of errors arising in reception data series, and issues the number of errors information to an error information retrieval part 10. A discrimination level control part 13 sets the discrimination level of the discrimination circuit 4 to an optimum value based on the information from an error information retrieval part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for setting the discrimination level of a discrimination circuit that binarizes received data to an optimum value in digital transmission such as facsimile and teletext.

BACKGROUND TECHNOLOGY In digital transmissions such as facsimile broadcasts and text broadcasts, data transmitted from the transmitting side is distorted at the receiving side due to transmission path distortion caused by various causes such as ghost noise (echo noise in telephone facsimiles) and low electric fields. It may not be received correctly. Therefore, in response to such transmission path distortion, it is necessary to always adjust the discrimination level of a discrimination circuit that binarizes received data to an optimum value to improve the receiving performance of received data. Conventional methods for setting this type of discrimination level include a so-called fixed discrimination level method in which the discrimination level is set to a value that is considered to be optimal based on the received data, and an average value method in which the discrimination level is set to the average value of the received data. .

Problems to be Solved by the Invention In the above-mentioned fixed method, the optimal discrimination level varies greatly depending on the transmission line distortion, so the transmission line distortion for which the set value is the best is extremely limited. Therefore, it is not possible to set the optimum discrimination level for all transmission path distortions.

In addition, the average value method is good against many transmission path distortions, but when there is a negative polarity TV ghost in teletext broadcasting that has TV radio waves on the transmission path, the average value method of the received data The discrimination level set to is not optimal.

This is because in teletext broadcasting, a digital signal is superimposed on a video image signal, and the signal is AM-modulated and transmitted. Therefore, even ghosts that do not have much effect on TV images may appear as 5.
In a teletext signal sent periodically at a 73 MHz beep/) rate, there is a ghost that is significantly affected. The properties of a ghost change greatly depending on the phase difference between the carrier waves on which the signal is superimposed; when the phase difference between the desired wave and the reflected wave is 0 degrees, it is called a positive polarity ghost, and when it is 180 degrees, it is called a negative polarity ghost. . - On the other hand, television receivers are equipped with an automatic gain control (AGC) circuit that automatically controls the gain of the high-frequency amplifier so that a constant contrast screen is displayed even when the electric field strength changes. It is provided. Due to the interaction between this AGC circuit and the ghost, the character multiplex signal at the video output stage becomes smaller when it is a positive polarity ghost, and larger when it is a negative polarity ghost, and the optimal discrimination level for a negative polarity ghost is lower than the average value of the signal. It has been confirmed by the experimental results of the inventor of the present invention that the Therefore, in the average value method, the set discrimination level is not optimal when negative polarity ghost distortion exists in teletext broadcasting that uses television radio waves for the transmission path.

An object of the present invention is to solve the above-mentioned technical problems and provide a discrimination level setting method that can always set an optimal discrimination level for any type of transmission path distortion. That's true.

Means for Solving the Problems The present invention sets the discrimination level of a discrimination circuit that discriminates the level of received data given via a transmission line in multiple stages over a predetermined range, and performs all of these discriminations. Discrimination characterized by sequentially level-discriminating the data based on the level, determining the number of errors in the output data from the discriminator circuit for each set discrimination level, and setting the level with the minimum number of errors as the discrimination level. This is a level setting method.

According to the present invention, received data is sequentially level-discriminated at a plurality of predetermined levels, the number of errors in the discriminated output data is determined, and the level with the minimum number of errors among all levels is set as the discrimination level. Set as . This makes it possible to always set an optimal discrimination level even for transmission line distortion caused by various causes such as impulse noise, ghost noise, and low electric fields.

Embodiment FIG. 1 is a block diagram showing the configuration of a teletext receiver 8!1 according to an embodiment of the present invention. A multiplexed television signal transmitted from a broadcasting station is received by an antenna 2 and provided to a data receiving section 3. This multiplexed television signal has teletext data modulated and multiplied by 'm'. The data receiving section 3 performs processing such as demodulation and amplification, and the teletext data is provided to the discrimination circuit 4. In the discrimination circuit 4,
The level is discriminated at the discrimination level, and the waveform is shaped into a binary digital signal. The output from the discrimination circuit 4 is given to an error correction/error detection section 5. This error correction/false 9 detection section 5 is
The error detection circuit 6b, which includes the error correction port jl) 6m and the error detection circuit 6b, is composed of a received data storage circuit 7, a reference data storage circuit 8, and a comparison circuit 9.

The output from the discrimination circuit 4 is given to the error correction circuit 6a, and the received data storage circuit 7 of the error detection circuit 6b.
given to.

If the received data has a data format in which an error correction code is added to the data group, the error correction circuit 6a corrects the data group based on the error correction code in the received data. Perform error correction processing. During correction processing in the error correction circuit 6a, the number of errors in the data group can be detected, and this error number data is given to the error information search section 10. The data correctly corrected by the error correction circuit 6a is sent to the data processing unit 11, where it is subjected to decoding processing, display processing, etc., and conforms to the standards of the display means 12 realized by a CRT (cathode a tube) or the like. The teletext data is converted into a signal and given to the display means 12 to display the teletext data.

If the received data is of a format including the above format, in which error detection data is periodically inserted into the data group, an error is detected by the error detection circuit 6). In other words, the same reference data as the error detection data is
The reference data is stored in the reference data storage circuit 8 in advance. Error detection data of the output data from the discrimination circuit 4 is stored in the received data storage circuit 7. The comparison circuit 9 compares the error detection data from the received data storage circuit 7 with the reference data from the reference data storage circuit 8, detects the number of errors in the received data group, and sends the error number information to the error information search section. Give 10. The discrimination level control unit 13 sets the discrimination level of the discrimination circuit 4 to an optimal value based on information from the error information search unit 10, as described later.

FIG. 2 is a 70-chart showing the operation of setting the discrimination level of the discrimination circuit 4 to an optimum value. Moving from step n1 to step n2, the discrimination level of the discrimination circuit 4 is set in multiple stages within a predetermined range.Next, the process moves from step n2 to step n3, and the discrimination level of the discrimination circuit 4 is set to the first discrimination level. is set to Next step n4
Next, the received data from the data receiving unit 3 is level-discriminated at the first discrimination level, and it is determined whether the error correction/detection unit 5 has successfully corrected/detected the error. If the number of errors is very large, error correction or detection may not be possible), the number of errors is given to the error information search section 10 and stored in step n5.

Next, in step n6, the discrimination circuit 4 is
It is determined whether or not the level has been discriminated. If not, the level of the discrimination circuit 4 is set to the next second discrimination level in step n7, and the process returns to step n4 again to set the discrimination level of the second mouth. Level discrimination of the next received data is performed at step n5, and the number of errors is detected at step n5 as described above. In this way, step n4,
A series of operations n5, n6, and n7 are repeated, and when level discrimination of all discrimination levels is completed in step n6, the process moves to step n8.

Note that if there are so many errors in the data that errors cannot be detected in step n4, step n6
Move to.

In step n8, it is determined whether or not the error number information has been given to the error information search unit 10 at least once, and if so, the error information search unit 10 determines the discrimination level at which the number of errors is the minimum; The data is given to the discrimination level control section 13, and thereby the discrimination level control section 13
The level at which the number of errors is the smallest is set as the discrimination level of the discrimination circuit 4. In this way, the discrimination level of the discrimination circuit 4 is set, and the operation ends at step nil.

In step n8, if the error number information is not stored in the error information search unit 10 at all, that is, if the distortion in the transmission path is so great that error detection processing cannot be performed at any level, the process moves to step I]10 to retrieve the received data. Set the discrimination level to the average value of .

In this way, the number of T errors in the received data is detected, and the level of the discrimination circuit 4 that minimizes the number of errors is set as the discrimination level. This makes it possible to always set the discrimination level to an optimal value, regardless of the type of transmission path distortion.

In this main embodiment, even if the transmitting side does not send out the error detection data stored in the receiving side, if the data is in a data format with an ffi') correction code added, the error correction circuit 6a
By using this, the number of errors can be detected, and even in such a case, the discrimination level of the discrimination circuit 4 can be easily set to the optimum value.

In the above embodiment, the discrimination circuit 4 was used to binarize the teletext data, but the present invention can also be suitably implemented in order to set the discrimination level of the signal at an optimum value. can.

Effects As described above, according to the present invention, the discrimination level can always be set to the optimum value for any type of transmission line distortion. Therefore, it is possible to improve the receiving performance of digital compensation data.

[Brief explanation of the drawing]

FIG. 1 is a simplified block diagram of a teletext broadcast reception 8!1 according to an embodiment of the present invention, and FIG. 2 is a flowchart showing the operation of setting the discrimination level of the discrimination circuit 4 to an optimum value. 1... Teletext receiver, 3... Data receiving section, 4.
...Discrimination circuit, 5...Error correction/error detection section, 6a.
...Error correction circuit, 6b...Error detection circuit, 7...
Received data storage circuit, 8...Reference data storage circuit, 9
...Comparison circuit, 10...Error information search unit, 13...
・Discrimination Level Control Department Agent Patent Attorney Number of strokes Kei - Department 2nd! i0

Claims (1)

[Claims] The discrimination level of a discrimination circuit that discriminates the level of received data given via a transmission path is set in multiple stages over a predetermined range, and the data is sequentially processed at all these discrimination levels. A discrimination level setting method comprising: discriminating levels, determining the number of errors in output data from a discrimination circuit for each of the set discrimination levels, and setting the level with the minimum number of errors as the discrimination level.