JPH03112276A - Ringing compensation circuit - Google Patents

Abstract

PURPOSE:To suppress production of loopback distortion practically and to prevent ringing by a post-interpolation filter by converting a signal comprising of a sampling series into a sampling series comprising a high sampling frequency so as to apply ringing compensation. CONSTITUTION:An original signal is sampled by a sampling circuit 1. Normally the signal is A/D-converted and digitized at the circuit l. The resulting signal is led to a sampling frequency doubler circuit 2, where the sampling frequency is converted into a frequency 2fs. Then the converted signal is led to a known ringing compensation circuit 3. Then the resulting signal is led to a known ringing compensation circuit 3. Then ringing is eliminated (reduced). There are frequency gaps in the frequency spectrum, then loopback distortion causes no problem. Then the signal is led to a low pass filter 4. The cut-off characteristic in the filter is unsharpened to prevent new ringing in this state. Then the signal is converted into an analog signal by a D/A converter 5. Then the signal is converted into a continuous signal. As a result, a signal 7 with no (less) ringing is finally obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a circuit system for specifically realizing a system for compensating for (reducing or eliminating) ringing that occurs when a signal is applied to a filter, etc. .

[Conventional technology]

In the past, many attempts have been made to compensate for ringing. One is based on sampled signal sequences.

An example of a conventional device is disclosed in Japanese Patent Application No. 159122/1963 (
Filter Ringing Compensation Method and Apparatus). In this example, it is configured by a combination of a symmetric filter and a point-symmetric filter, or a combination of an asymmetric filter and an asymmetric filter.

In this configuration, the filter may be a continuous delay line,
Alternatively, a method using a sample value sequence such as digital signal processing may be used.

The present invention is a circuit system realized by the latter method [Problem to be solved by the invention] In the ringing compensation described above, a new frequency component is generated by removing (reducing) the ringing. This is because, for example, as is well known, ringing occurs when an impulse is applied to an ideal reduction filter because if the frequency band is limited to a certain frequency, a ringing waveform essentially occurs. If this waveform is modified, naturally higher frequency components will be generated.

”-2 The conventional technology does not take into account the influence of this generated frequency component on the circuit configuration, and therefore,
When processing a sample value series, there is a problem in that frequency components overlap.

Furthermore, the above conventional technology does not take into account ringing that occurs when returning a sample value sequence to a continuous signal.
There is a problem in that it cannot be compensated for (or must be removed in an analog manner using another method) for what occurs in this part.

The present invention aims to provide a concrete circuit format that solves these problems.

[Means to solve the problem]

In order to achieve the above object, signal processing is performed at a frequency higher than the sampling frequency f8 of the original Kakini value series.

FIG. 1 shows a block diagram of the circuit configuration, and FIG. 2 shows its frequency relationship. Here, a case where calculation is performed at 2 fs is shown.

The original signal is sampled by a sampling circuit 1.

This frequency spectrum is shown in FIG. 2(a). however,
It is originally given as a sample value series, and there are cases where a sampling circuit is not required. Usually, this is where Al2D conversion is performed and digitized.

This is guided to the sampling frequency doubling circuit 2. Here, the sampling frequency is converted to 2fs. This method is well known. For example, it is sufficient to insert a sample value series of fs into every other 2fs and 0 into every other 2fs, and then use a low-pass digital filter to leave only the components shown in (1)).

This signal is then guided to a known ringing compensation circuit 3. This eliminates (reduces) ringing. The frequency spectrum is shown in FIG. 2(C).

Unlike (,), there is a gap in frequency, so aliasing distortion is not a problem.

This signal is then guided to a low pass filter 4. Here, the cutoff characteristics are made gentle to prevent new ringing from occurring at this stage. However, this low-pass filter may be omitted.

If the sample value series is a digital signal, the I)/A converter 5 converts it into an analog signal.

This signal is then converted into a continuous signal by a post-interpolation filter 6. The gains of filter 4 and filter 6 are shown in Fig. 2(d),
Shown in (e).

As a result, the final ringing-free (less) signal 7
get. This frequency spectrum is shown in FIG. 2Cf).

[Effect]

Signal with ringing removed using sample value series (Figure 2 (C))
Since the sampling frequency is 2 fs, there is little concern about aliasing distortion.

Furthermore, as is clear from FIG. 2, the characteristics of the low-pass filters 4 and 6 do not have to be steep, so no new ringing occurs here.

Therefore, a waveform without (less) ringing can be obtained.

This is impossible with the frequency spectrum shown in FIG. 2(a).

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

FIG. 3 shows a specific example of the first known ringing compensation circuit 3. In FIG. Here, the ringing generated by the symmetric digital filter 10 having desired characteristics is compensated for by the output of the point symmetric digital filter 11 and the edge detection output.

As shown in Figures 1 and 2, the sampling frequency is Jsl
Since it is 2fs from 10. to 2fs, these filters 10.
11 may double the number of taps (number of delay stages) of the conventional filter and set the coefficient to 0 for every other filter.

FIG. 4 is for compensating for the ringing that has already occurred (however, the delay element for adjusting the delay amount is omitted). In this case as well, the configuration may be similar to the above. Furthermore, a combination type of FIG. 3 and FIG. 4 is also possible.

Furthermore, the following cases can also be implemented in the same way.

(1) The sampling frequency for ringing removal is 2f8
It is not limited to , and may be an integer Xfs. Furthermore, in principle, it may be (m/n)fs.

(2) The ringing removal circuit is not limited to the combinations of [symmetrical filters, point-symmetrical filters] shown in Figs. is possible. Here, the symmetric filter 10-point symmetric filter is a filter whose coefficient is the sum of both coefficients.

(3) In the configuration shown in FIG. 4, the characteristics of the point-symmetric filter may be known or may be determined from a reference signal included in the signal.

(4) Although there are many other specific methods for ringing compensation, it is clear from the explanation in the text that the present invention is applicable to all methods that perform compensation based on sample value series. be.

(5) The circuit for increasing the sampling frequency and the circuit for removing (compensating) ringing can be made common.

〔Effect of the invention〕

According to the present invention, ringing compensation is possible even when the sampling frequency fs is nearly twice the frequency band of the target signal.

That is, to practically prevent the occurrence of aliasing distortion by compensating for ringing in the sample value series, and further to practically suppress the occurrence of ringing by the post-interpolation filter for converting the sample value series into a continuous signal. I can do it.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the configuration of an embodiment of the present invention, and FIG.
The figure is an explanatory diagram showing the frequency relationship, Figure 3. FIG. 4 is a known configuration diagram of a linking compensation circuit in an embodiment. 2... Sampling frequency conversion circuit, 3... Linking compensation circuit.

Claims (1)

[Claims] 1. A ringing compensation circuit that performs ringing compensation by converting a signal consisting of a sample value series into a sample value system consisting of a higher sampling frequency.