JPH0690385A - Waveform equalizer - Google Patents

Abstract

PURPOSE:To accurately detect a reference signal to detect transmission line distortion by controlling an AGC output at AM transmission so as to be a prescribed multiple of that at FM transmission. CONSTITUTION:In the case of FM transmission, a selector 6 selects an output of a nonlinear de-emphasis 5, a selector 12 selects an output of an AGC 2, and a selector 14 selects an output of an ADC 3 respectively. On the other hand, when a detector 10 detects AM transmission, a display signal is sent to a waveform equalization control means 15 and allows the selector 6 to select an output of a multiplier 16. The means 15 controls the selector 12 to select an attenuator 11 and controls the selector 14 to select a multiplier 13 when a signal whose amplitude is 1/k from the attenuator 11 is outputted via the ADC 3. Furthermore, the means 15 detects transmission line distortion based on a reference signal whose amplitude is 1/k detected by a detector 8 to control a tap coefficient of an equalization filter 4 thereby correcting distortion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an equalizer for removing transmission line distortion when analog transmission of sample values is performed,
In particular, the present invention relates to a waveform equalizer that effectively equalizes transmission line distortion during AM transmission such as CATV.

[0002]

2. Description of the Related Art A type of high-definition broadcasting system
A MUSE system has been developed that can support both M transmission and FM transmission. In this system, in order to secure S / N in consideration of the nature of noise during transmission, digital transmission is performed in FM transmission. Non-linear emphasis and non-linear de-emphasis processing by signal processing are used, and in the AM transmission, the S / N is ensured by setting the signal to the full dynamic range.

Therefore, the received signal is converted into an A / D converter (hereinafter, referred to as
In the receiver of the MUSE system which converts into a digital signal by the ADC) and processes it, the MUSE is used during FM transmission.
It is set to a level of about 1/2 of the ADC input range with respect to the low frequency of the signal, and to a level of about 1 during AM transmission. This state is shown in FIG.

In FIG. 2, first, (a) shows the case of FM transmission. For example, if the resolution of the ADC is 10 bits, the input signal is input so as to have a signal amplitude equivalent to 9 bits.
Then, after A / D conversion, non-linear de-emphasis is applied to restore a 10-bit signal to suppress triangular noise peculiar to FM transmission.

Next, (b) shows the case of AM transmission, and the input signal is input with a signal amplitude of the full input range of 10 bits. Then, for these signals, the transmission line distortion is detected from the reference signal (for example, impulse response) as shown in the figure, and waveform equalization is performed.

By the way, as this waveform equalizing device, the device shown in FIG. 3 is conventionally known.
The outline of the operation of this prior art will be described. In FIG. 3, reference numeral 1 is an input terminal, and an analog signal input from the input terminal is an automatic gain control amplifier (hereinafter referred to as AGC).
The signal is controlled so that the signal has an amplitude of a specified level at 2 and is input to the ADC 3. The signal sampled by the ADC 3 is supplied to both the equalization filter 4 and the sync / data detector 10.

The sync / data detector 10 has a function of detecting a sync signal and other control data to detect a transmission system. Depending on the transmission system, the FM / data transmission is performed as shown in FIG. The gain of the AGC 2 is controlled so that the level shown in FIG.

On the other hand, the reference signal detector 8 detects the reference signal from the signal guided from the equalization filter 4 and supplies the reference signal to the waveform equalization control means 9. Therefore, the waveform equalization control means 9 obtains a filter tap coefficient for suppressing transmission path distortion from the supplied reference signal and sets it in the equalization filter 4 to perform waveform equalization. The waveform-equalized signal is supplied to the non-linear de-emphasis 5 and the selector 6.

The non-linear de-emphasis 5 restores the non-linear emphasis during FM transmission and guides the signal to the selector 6. This selector 6 is a sync / data detector 10
The signal guided from the non-linear de-emphasis 5 is selected during FM transmission, and the signal directly guided from the equalization filter 4 is selected during AM transmission and output from the output terminal 7.

[0010]

The above-mentioned prior art is based on the AM.
No consideration was given to the case where there is a large transmission line distortion during transmission, and at this time there was the problem that the reference signal could not be detected accurately and waveform equalization became impossible.

For example, in the case where the transmission system has a ghost as shown in FIG. 4 (b), the input analog signals are the undistorted signal (a) and the ghost ( b)
It becomes a signal with distortion (c) that is a combination of. Then, since AGC is applied to the frame pulse of this signal,
The signal output from the AGC is as shown in FIG. Therefore, the AGC output signal of the level shown in FIG. 4 (d) is input to the ADC, and the reference signal for detecting the transmission path distortion exceeds the input dynamic range of the ADC and is clipped. For this reason, the reference signal cannot be detected accurately and waveform equalization cannot be performed.

[0012]

In the first invention, the AGC is used.
Output signal (hereinafter referred to as AGC output) is multiplied by 1 / α to lead to the ADC, and a digital signal converted by the ADC (hereinafter referred to as ADC output) is multiplied by α to synchronize / data. The waveform equalization control means is provided with a first multiplier for leading to the detecting means and a second multiplier for multiplying the output signal of the equalization filter by α and leading to the selector.
The selector selects the output signal of the second multiplier while controlling the output signal to be 1, and α = 1 during FM transmission.
And the selector selects the output signal of the non-linear de-emphasis.

According to the second aspect of the invention, an ADC having a resolution m bits higher than the specification resolution n bits of the ADC required to secure the performance of the MUSE receiver (for example, if the specification resolution n is 10 bits, m 11 bits or more) is used, and an attenuator that reduces the signal amplitude to 1 / k and a subtractor that subtracts h from the ADC output signal are provided in front of the ADC input.

[0014]

[Equation 4]

[0015]

[Equation 5]

[0016] is given.

[0017]

In the first aspect of the invention, during AM transmission, α is controlled so that the output signal of the attenuator multiplied by 1 / α has a signal amplitude that does not exceed the ADC input dynamic range. The ADC output signal is guided to the first multiplier for multiplying by α, is returned to the original signal amplitude level, and is guided to the synchronization / data detection. Thus, the synchronization / data detection means can detect the synchronization signal, the transmission method, and the like. Also, 1 / α for the equalization filter
Since the signal is introduced, the reference signal is not clipped and is accurately detected, so that waveform equalization is normally performed. The signal after waveform equalization is multiplied by α by the second multiplier to return to the original signal amplitude and output through the selector. As a result, the reference signal can be converted into a digital signal without being clipped by the ADC even if there is a large transmission line distortion during AM transmission, and thus waveform equalization can be normally performed.

In the second aspect of the invention, an ADC having a resolution m bits higher than the specification resolution n bits of the ADC required to secure the performance of the MUSE receiver is used. Set the signal amplitude at the input stage to 1
A subtractor that subtracts h from the ADC output signal so that it falls within the ADC input dynamic range by multiplying by / k subtracts h from the A / D converted digital signal.

The values of k and h at this time are given by the following equations.

[0020]

[Equation 6]

[0021]

[Equation 7]

As a result, the reference signal can be accurately converted into a digital signal without being clipped by the ADC during AM transmission, and waveform equalization can be normally performed.

[0023]

EXAMPLE A waveform equalizer according to the present invention will be described below.
This will be described in detail with reference to the illustrated embodiment. FIG. 1 shows an embodiment of a waveform equalizer according to the present invention, in which 11 is an AG
Attenuator for multiplying analog signal after C by 1 / k, 12 is A
A second selector that selects the GC output and the output of the attenuator 11 and guides it to the ADC 3, 13 is a first multiplier that multiplies the digital signal output from the ADC 3 by k, and 14 is an ADC.
The third selector 16 selects the output of the third multiplier 13 and the output of the first multiplier 13 and guides it to the sync / data detector 10. Reference numeral 16 denotes a signal after waveform equalization which is an output signal of the equalization filter 4. A second multiplier 15 for doubling controls the equalization filter 4 by the reference signal derived from the reference signal detector 8 to perform waveform equalization, and switches between the second and third selectors 12, 14. This is a waveform equalization control means for performing control, and the rest is the same as the conventional example of FIG.

Next, the operation of the embodiment shown in FIG. 1 will be described. In the case of FM transmission, as shown in the figure, the first selector 6 outputs the output of the nonlinear de-emphasis 5, the second selector 12 outputs the output of the AGC 2, and the third selector 14 outputs.
Selects the output of ADC 3, respectively. Therefore, this case is the same as the conventional example, a series of processing is performed with the signal amplitude shown in FIG. 2A, and the same operation as the conventional example is performed.

Next, the case of AM transmission will be described. First, as in the case of FM transmission, the second selector 12 and the third selector 14 are selected as shown. When the sync / data detector 10 detects that the AM transmission is performed, a signal indicating the AM transmission is supplied to the waveform equalization control means 15 and the output of the second multiplier 16 is selected. , The first selector 6 is switched.

Therefore, when the waveform equalization control means 15 receives the AM transmission, it controls the second selector 12 so as to select the attenuator 11, and then the amplitude 1 / k from the attenuator 11 is changed. The signal is sampled by ADC3,
The third selector 14 is controlled so as to select the first multiplier 13 at the time of outputting.

Further, the waveform equalization control means 15 detects the transmission line distortion on the basis of the reference signal of the amplitude 1 / k detected by the reference signal detector 8 and is given an equalization filter characteristic for correcting it. The filter tap coefficient of the equalization filter 4 is controlled. The waveform-equalized signal of amplitude 1 / k is multiplied by k by the second multiplier 16 to be returned to the original amplitude, and is output from the output terminal 7 through the first selector 6.

An example of the switching timing of each selector by the waveform equalization control means 15 is shown in FIG. ADC3
The sampling clock 501 is input to the ADC 3, and the ADC3 output 502 is output as the output signal of the ADC 3. Second
The selector 12 selects the output of the attenuator 11 at the same time that the output n ₁ is converted into a digital signal by the ADC 3 by the selector 12 switching signal 503. As a result, the output of the ADC3 at the next sampling clock becomes 1
/ K · n ₂ .

If the first multiplier 13 outputs the output of the ADC 3, for example, immediately after multiplying it by k, it outputs the output signal 504 of the multiplier 13. Third selector 14
By the selector 14 switching signal 505.
The output of 3 is switched to the output of the first multiplier 13 and is led to the sync / data detector 10. As a result, the signal introduced to the sync / data detector 10 is 506.

Although not shown, for example, when the first multiplier 13 latches the output of the ADC 3 and multiplies it by k and then latches it again and outputs it, a delay of 2 clocks occurs, In this case, if delay means for delaying the output of the ADC 3 by 2 clocks and providing it to the second selector is provided and the switching signal 505 of the second selector 14 is controlled to be delayed by 2 clocks, it is guided to the sync / data detector 10. The output signal is 506 delayed by 2 clocks. Therefore,
A signal having the same amplitude as the input signal amplitude is always guided to the sync / data detector 10, and sync / data detection is normally performed.

Further, the second multiplier 16 multiplies the delayed signal whose waveform is equalized by the equalization filter 4 by k and outputs the multiplier 16 output 507. As a result, the signal after n ₂ multiplied by 1 / k is waveform-equalized, and the signal is multiplied by k and output from the first selector 6 as the waveform-equalized signal n ₂ '507.

Therefore, according to this embodiment, the signal at the time of AM transmission, which is likely to be clipped at the ADC due to transmission path distortion, is multiplied by 1 / k and k times before and after the ADC. Since it can be set within the input dynamic range of, the reference signal can always be detected accurately, and waveform equalization can be reliably performed. In this embodiment, the value of the coefficient k is 1
Any value may be used as long as it is not limited to a specific value.

Next, another embodiment of the present invention will be described with reference to FIG. The embodiment of FIG. 6 is different from the embodiment of FIG. 1 in that the fourth selector 17 that selects the output of the second multiplier 16 and the output of the equalization filter 4 and guides them to the first selector 6 is used. By providing the waveform equalization control means 18 which is provided and also controls the fourth selector 17, the others are shown in FIG.
This is the same as the first embodiment. Therefore, the differences from the embodiment of FIG. 1 will be described below.

When the sync / data detector 10 detects AM transmission, it controls the first selector 6 to select the output of the fourth selector 17. At this point, the fourth selector 17 selects the one shown, that is, the output of the equalization filter 4. The waveform equalization control means 18 detects the transmission line distortion from the reference signal of the amplitude 1 / k detected by the reference signal detector 8 and supplies the equalization filter 4 with a filter coefficient necessary for equalizing the distortion. By doing so, waveform equalization is performed. Then, the signal of amplitude 1 / k output from the equalization filter 4 is multiplied by k in the second multiplier 16 and then supplied to the fourth selector 17.

Next, at this timing, the waveform equalization control means 18 controls the fourth selector 17, and the second multiplier 1
Select the signal from 6. These selector control timings will be described with reference to FIG. Second and third selector 1
The control timings 2 and 14 are the same as those in the embodiment of FIG. The signal equalized by the equalization filter 4 becomes the equalization filter 4 output signal 508. For example, the second multiplier 1
If 6 multiplies the input signal by k and outputs it immediately,
Since this is the output of the multiplier 16 507, the fourth selector 17 switches from the output of the equalization filter 4 to the output of the second multiplier 16 at the timing of the selector 17 switching signal 509.

As a result, the amplitude of the signal output from the fourth selector 17 is always the amplitude corresponding to the input signal amplitude, and a signal having an amplitude of k times is not output. Although not shown, the second multiplier 1
When the input signal 6 is multiplied by k and then latched and output, the output signal of the second multiplier 16 is delayed by 1 clock from 507. In this case, the output of the equalization filter 4 is delayed by 1 clock. By providing a delay means for leading to the fourth selector 17 and delaying the switching by the switching signal 509 of the fourth selector 17 by one clock, the same effect as described above can be obtained.

Therefore, also in this embodiment, the signal at the time of AM transmission, which may be clipped at the ADC due to the transmission path distortion, is 1 / k, k before and after the ADC.
By doubling the value, it is possible to fit within the input dynamic range of the ADC, so that the reference signal can be accurately detected, and waveform equalization can always be performed reliably. Also in this embodiment, the value of the coefficient k may be any value as long as it is 1 or more.

By the way, in this embodiment, for example,
When k = 2, the S / N is 3 dB, and when k = 4, the S / N is also 6 dB down. Therefore, even in the case of AM transmission,
When the transmission line distortion is not so large that there is no fear of exceeding the input range of the ADC3, the second, third, and fourth selectors 12, 14, and 17 are selected from the illustrated ones, and the input range of the ADC3 is set. The selectors 12, 14, 17 may be controlled at the timing shown in FIG.

By doing so, waveform equalization can be sufficiently performed without degrading the S / N when the transmission line distortion is small even in the AM transmission.

Next, FIG. 7 shows another embodiment of the present invention. This embodiment is different from the embodiment of FIG.
Is provided to the ADC 3, and an OF / UF limiter 19 is provided for applying a limiter when the output signal of the second multiplier 13 overflows / underflows, and its output is provided to the third selector 14. The other points are the same as those in the embodiment of FIG. 1 in that they are supplied and that a waveform equalization control means 20 for controlling the third selector is provided. Therefore, differences from the embodiment of FIG. 1 will be described below.

During FM transmission, each selector selects the one shown in the figure, and performs the same operation as in the conventional example. And sync /
When the data detector 10 detects AM transmission,
The first selector 6 is controlled to select the output of the second multiplier 16, and informs the waveform equalization control means 20 that the AM transmission is performed.

When the waveform equalization control means 20 receives the signal representing the AM transmission, it controls the third selector 14 to open the OF signal.
The output of the / UF limiter 19 is selected. As a result, the signal multiplied by k by the first multiplier 13 becomes O.
It is limited by the F / UF limiter 19 and guided to the sync / data detector 10. In this case, for example, the resolution of the ADC 3 is 10 bits, and the signal amplitude shown in FIG.

Now, the limit value in the OF / UF limiter 19 is set to 0 and 1023, for example, and the limiter is applied to the signal multiplied by k in the first multiplier 13 to synchronize / data detector 1
If it is supplied to 0, this sync / data detector 1
When the amplitude of the frame pulse is 64 or less and 956 or more, 0 controls the gain of the AGC 2 so as to reduce the amplitude. Therefore, the synchronization / data detector 10 finally reduces the gain of the AGC 2 until the amplitude of the frame pulse becomes 64 and 956 after k times.

As a result, the input signal amplitude of the ADC 3 is
Since it is 1 / k as in the embodiment shown in FIG. 1, it does not fall into the input range of the ADC 3 and is not clipped. The operation after the equalization filter 4 is the same as that of the embodiment shown in FIG.

Therefore, according to this embodiment, the AM which may be clipped in the ADC due to the transmission path distortion.
By making the signal at the time of transmission 1 / k and k times before and after the ADC, it can be kept within the input dynamic range of the ADC, so that the reference signal can be accurately detected and waveform equalization is always ensured. Can be done.

According to this embodiment, it is possible to omit the attenuator and the selector in the preceding stage of the ADC, and as a result, the AD
Since it is not necessary to switch and control the selector according to the C sampling clock, the configuration and control can be simplified. Further, although not shown, in this embodiment as well,
Similarly to the embodiment of FIG. 6, the fourth output of the equalization filter 4 and the second multiplier 16 is selected and led to the first selector.
In the case of AM transmission, if the transmission path distortion is small and there is no fear of exceeding the input range of the ADC, the third selector outputs the output of the ADC 3 and the fourth selector outputs the equalization filter. By selecting the output of 4, it is possible to perform sufficient waveform equalization without degrading the S / N.

FIG. 8 shows another embodiment of the present invention. The difference between this embodiment and the above-mentioned embodiment is that
An attenuator 22 that multiplies the output of GC2 by 1 / α and supplies it to ADC3, and a third multiplier 23 that multiplies the output of ADC3 by α.
And a fourth multiplier 24 for multiplying the output of the equalization filter 4 by α
And a transmission line distortion is detected from the reference signal derived from the reference signal detector 8, and a filter coefficient for correcting the distortion is guided to the equalization filter 4 to perform waveform equalization, and the attenuator 2
This is because the waveform equalization control means 21 for controlling the second, third, and fourth multipliers 23, 24 is provided, and the other points are the same as those in the above-described embodiment.

The points different from the other embodiments will be described below. The initial state is α = 1, which is the same as the conventional example. The attenuator 22 multiplies the signal guided from the AGC 2 by 1 / α so that the signal falls within the input range of the ADC. The third multiplier 23 outputs the ADC output signal to α
It is multiplied and returned to the original signal amplitude, and is guided to the synchronization / data detector 10. Further, the fourth multiplier 24 multiplies the signal of amplitude 1 / α equalized by the equalization filter 4 by α and guides it to the first selector 6.

Here, the timing at which the waveform equalization control means 21 controls the value of α is such that the waveform equalization control means 18 of the embodiment shown in FIG.
7 is the same as the timing of controlling 7, and the signal multiplied by 1 / α by the attenuator 22 is sampled by the ADC 3 and input to the third multiplier 23 by α.
Is controlled, and α is controlled at the timing when the signal of amplitude 1 / α waveform-equalized by the equalization filter 4 is input to the fourth multiplier 24.

The value of the coefficient α is determined by the waveform equalization control means 21, and the method is, for example, 1, 2,
A simple integer such as 4 may be used, or the reference signal is controlled so that 0 <reference signal value <1023 from the value of the signal derived from the reference signal detector 8 (for example, ADC
If the resolution of 3 is 10 bits and the reference signal has a value of 0 or 1023, it may be considered that the ADC 3 is clipped. As is apparent from this, the value of the coefficient α is not particularly limited as long as it is 1 or more.

Therefore, according to this embodiment, the signal at the time of AM transmission, which is likely to be clipped at the ADC due to the transmission path distortion, is multiplied by 1 / α and α before and after the ADC so that the input dynamic of the ADC is increased. Since it can be set within the range, the reference signal can be accurately detected and sufficient waveform equalization can be performed.

Further, according to this embodiment, the value of α can be adaptively controlled according to the magnitude of the transmission line distortion. Therefore, when the transmission line distortion is small and it is not necessary to increase α so much, S Less deterioration of / N.

FIG. 9 shows another embodiment of the present invention. This embodiment differs from the embodiment of FIG. 8 in that
When the specification resolution of DC3 is n bits, an equalization filter 4 that performs waveform equalization processing on an n-bit digital signal,
Instead of the reference signal detector 8 and the waveform equalization control means 15,
An equalization filter 25 for performing waveform equalization processing on the m-bit (m ≧ n) digital signal α times (α ≧ 1) by the third multiplier 23, a reference signal detector 27, and waveform equalization control means 26. Is used to guide the output signal of the third multiplier 23 to the equalization filter 25, and the lower bits of the output signal of the equalization filter 25 are subjected to the non-linear de-emphasis processing 5 and the first
The lower bit passing means 28 leading to the selector 6 of
The fourth multiplier 24 is omitted, and the rest is the same as the embodiment of FIG. Therefore, the differences from the embodiment of FIG. 8 will be described below.

First, the initial state is α = 1, and this case is the same as the embodiment of FIG. Sync / data detector 10
Is detected to be AM transmission, the first selector 6
Is controlled to select the output of the lower bit passing means 28, and at the same time, the waveform equalization control means 26 is informed of the AM transmission. Therefore, the waveform equalization control means 26
If it is M transmission, the 1 / α attenuator 22, the third
Is controlled so that clipping is not applied in the input dynamic range of the ADC 3. Here, the output signal of the third multiplier 23 becomes m bits (m ≧ n) when multiplied by α (α ≧ 1), where n is the specification resolution of the ADC 3.

The equalization filter 25, the reference signal detection 27, and the waveform equalization control means 26 are waveform equalization means for equalizing the waveform of an m-bit digital signal. Output. The lower bit passing means 28 passes only the lower n bits of the guided m-bit signal.

Therefore, according to this embodiment, the signal at the time of AM transmission, which is likely to be clipped at the ADC due to the transmission path distortion, is multiplied by 1 / α and α before and after the ADC so that the input dynamic of the ADC is increased. Since it can be set within the range, the reference signal can be accurately detected, and waveform equalization can be reliably performed.

Further, according to the embodiment of FIG. 9, the value of α can be adaptively controlled according to the magnitude of the transmission path distortion, like the embodiment of FIG. If it is not necessary to increase α so much, deterioration of S / N is small. Further, according to this embodiment, even in the case of FM transmission, when the transmission line distortion is large and the reference signal is clipped, the waveform equalization control means 26 can control α. In the case of transmission, the same effect as in the case of AM transmission can be obtained.

Although not shown, the 1 / α attenuator 2
The third multiplier 23 for multiplying by 2 and α is the same as the one embodiment of FIGS. 1, 6 and 7 is a 1 / k attenuator, the first multiplier for multiplying by k, the second and third multipliers. You may comprise by a selector etc. Further, although not shown in the figure, the third multiplier 23 is
The output of ADC 3 is multiplied by α and the output of ADC 3 is multiplied by α. The output of ADC 3 is multiplied by α. Alternatively, it may be guided to the synchronization / data detector 10.

FIG. 10 is also another embodiment of the present invention. This embodiment is different from the other embodiments in that the output of the AGC 2 is 1
/ K times the attenuator 11, an ADC 29 having a resolution higher than the specified resolution as an ADC for A / D converting the output signal of the attenuator 11, a subtractor 30 for subtracting h from the output signal of the ADC 29, and a subtraction With the provision of the means 31 for generating the value h, the other points are the same as in the conventional example of FIG.

The operation of the embodiment shown in FIG. 10 will be described with reference to FIG. In case of AM transmission, AGC output signal is AD
The C input dynamic range is controlled to the level shown in FIG. Attenuator 11
The AGC output signal guided to is multiplied by 1 / k
Be led to. Here, the value of the coefficient k is given by the following equation when the specification resolution of the ADC is n bits and the resolution of the ADC 29 is m bits.

[0061]

[Equation 8]

Therefore, for example, the specification resolution n of the ADC is 1
If it is 0 bit, the resolution m of ADC 29 is 11 bit
In case of, k = 2, and in case of 12 bits, k = 4.

The signal multiplied by 1 / k is converted into a digital signal by the ADC 29. If the resolution of the ADC 29 is 11 bits, the value after conversion into a digital signal is shown in FIG. 11 (b). It becomes a value. The output signal of the ADC 29 is guided to the subtractor 30, and the subtraction value h derived from the subtraction value generating means 31 is subtracted. The value of h is given by the following equation.

[0064]

[Equation 9]

As a result, for example, the specified resolution n of the ADC
Is 10 bits, the resolution m of the ADC 29 is 11 bits.
If so, h = 512, and if 12 bits, h = 15
36. Considering the case where the resolution of the ADC 29 is 11 bits, considering the above example, since h = 512, the output signal amplitude of the subtractor 30 is 64 to 956, which is the signal value of the specified level shown in FIG. As a result, the level of the frame pulse is supplied to the sync / data detector 10 at the signal amplitude value of the specified level, so that the sync / data detector 10 sets the AGC 2 to the level shown in FIG. 11 (a). Control.

Therefore, also in this embodiment, the signal at the time of AM transmission, which is likely to be clipped at the ADC due to the transmission path distortion, is multiplied by 1 / k in the preceding stage of the ADC.
Since it can be set within the input dynamic range of C, the reference signal can be accurately detected, and waveform equalization can always be performed reliably. Further, according to the embodiment of FIG. 10, since the bit accuracy of A / D conversion is the same as that of the conventional example, there is no possibility that the S / N is deteriorated.

FIG. 12 is also an embodiment of the present invention. This embodiment is different from the embodiment of FIG. 10 in that the subtractor 30 and the subtraction value generating means 31 are replaced with the lower bit passing means 28. , The output signal of the ADC 29 is led to the lower bit passing means 28, and the output thereof is led to the equalization filter 4 and the synchronization / data detector 10, and the other points are the same as the embodiment of FIG. Regarding the difference from the embodiment of FIG. 10, the operation of the lower bit passing means 28 will be described with reference to FIG. 11 in the case where the specification resolution n of the ADC is 10 bits and the resolution m of the ADC 29 is 11 bits.

In this embodiment, the amplitude of the signal output from the AGC 2 is as shown in FIG. 11 (a), which is multiplied by 1 / k by the attenuator 11 and guided to the ADC 29.
As a result, the output signal of the ADC 29 becomes as shown in FIG.

Here, the lower bit passing means 28 is
Only the lower 10 bits (= n) of the bit signals are guided to the equalization filter 4 and the sync / data detector 10. As a result, the values of 576 and 1468 in 11 bits become 64 and 956 in the lower 10 bits, which are supplied to the equalization filter 4 and the sync / data detector 10. Therefore, the level of the frame pulse is supplied to the sync / data detector 10 with the signal amplitude value of the specified level, and the sync / data detector 10 sets the AGC 2 to the level shown in FIG. Control. On the other hand, the coefficient k is as shown in FIG.
Similar to the embodiment of, the following equation is given.

[0070]

[Equation 10]

Therefore, according to this embodiment, the AM which may be clipped in the ADC due to the transmission path distortion.
By multiplying the signal during transmission by 1 / k times before the ADC,
Since it can be set within the input dynamic range of the ADC, the reference signal can be accurately detected, and waveform equalization can be reliably performed. Further, according to this embodiment, the bit precision of A / D conversion is the same as that of the conventional example, so that the S / N does not deteriorate. Further, according to this embodiment, a subtracter or the like is not required and only the lower bits of the digital signal need to be guided, so that the circuit configuration becomes simple.

[0072]

According to the present invention, when a large transmission path distortion occurs in the case of AM transmission and a clip is applied beyond the input dynamic range of the ADC, the ADC input is adjusted so that it falls within the ADC input dynamic range. Since the signal amplitude can be controlled to prevent clipping, it is possible to accurately detect the reference signal for detecting transmission line distortion, which is good not only for FM transmission but also for AM transmission. It is possible to perform waveform equalization on the.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a waveform equalizer according to the present invention.

FIG. 2 is a waveform diagram for explaining the operation.

FIG. 3 is a block diagram showing a conventional example of a waveform equalizer.

FIG. 4 is a waveform diagram for explaining the operation.

FIG. 5 is a timing chart for explaining the operation.

FIG. 6 is a block diagram showing a second embodiment of the waveform equalizer according to the present invention.

FIG. 7 is a block diagram showing a third embodiment of the waveform equalizer according to the present invention.

FIG. 8 is a block diagram showing a fourth embodiment of the waveform equalizer according to the present invention.

FIG. 9 is a block diagram showing a fifth embodiment of the waveform equalizer according to the present invention.

FIG. 10 is a block diagram showing a sixth embodiment of a waveform equalizer according to the present invention.

FIG. 11 is a waveform diagram for explaining the operation.

FIG. 12 is a block diagram showing a seventh embodiment of the waveform equalizer according to the present invention.

[Explanation of symbols]

 1 analog signal input terminal 2 automatic gain control amplifier (AGC) 3 A / D converter (ADC) 4 equalization filter 5 non-linear de-emphasis processing means 6 selector 7 digital signal output terminal after waveform equalization 8 reference signal detector 9 Waveform equalization control means 10 Sync / data detector 11 1 / k attenuator 12 Second selector 13 First multiplier 14 Third selector 15 Waveform equalization control means 16 Second multiplier 17 Fourth Selector 18 Waveform equalization control means 19 Overflow / underflow limiter 20 Waveform equalization control means 21 Waveform equalization control means 22 1 / α attenuator 23 Third α-multiplier 24 Fourth α-multiplier 25 etc. Equalization filter 26 Waveform equalization control means 27 Reference signal detector 28 Lower bit passing means 29 A / D converter (ADC) 30 Subtractor 31 Subtraction Value generation means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Kasahara 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa AV equipment division, Hitachi, Ltd. (72) Inventor Masako Totsuka 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Incorporated company Hitachi, Ltd. AV equipment division (72) Inventor Yuichi Ninomiya 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Broadcasting Technology Laboratory

Claims (10)

[Claims] 1. A transmission line distortion of a receiver which receives an analog signal transmitted by switching between AM transmission and FM transmission and digitally processes de-emphasis processing in the latter stage of an A / D converter in the case of FM transmission. In a waveform equalizer for equalizing a signal, an attenuator that multiplies a received analog signal by 1 / α, an A / D converter that samples an output signal of the 1 / α attenuator, and an A / D converter A first multiplier for multiplying the output signal by .alpha., A sync / data detecting means for detecting a sync signal and data of a transmission system from the output signal of the first multiplier, and the A / D conversion Filter for correcting the transmission line distortion of the output signal of the output device, non-linear de-emphasis processing means for performing non-linear de-emphasis processing on the signal waveform-equalized by the adaptive filter, and the adaptive filter A second multiplier for multiplying the waveform equalized signal by α, a first selector for selecting and outputting the output signal of the non-linear de-emphasis processing means and the output signal of the second multiplier are provided. The adaptive filter is composed of an equalization filter and a waveform equalization control means for supplying the equalization filter with a filter coefficient required for correction of the waveform distortion obtained from a reference signal for detecting transmission path distortion. With this waveform equalization control means, the first selector selects the second multiplier output in the case of AM transmission, and the first selector outputs the non-linear de-emphasis output in the case of FM transmission. The value of α of the 1 / α attenuator and the first and second multipliers is controlled to be α ≧ 1 in the case of AM transmission, and F
A waveform equalizer, which is configured to control α = 1 in the case of M transmission. 2. The invention according to claim 1, wherein the 1 / α attenuator comprises a 1 / k attenuator and a second selector, and
The k attenuator multiplies the received analog signal by 1 / k and the second selector is connected to select the input and output of the 1 / k attenuator to supply to the A / D converter.
The first multiplier is composed of a third k multiplier and a third selector, and the third k multiplier multiplies the output of the A / D converter by k and the third selector The output of the third k multiplier and the output of the A / D converter are selected and connected so as to be supplied to the synchronization / data detecting means.
In the case of FM transmission, the
The first selector selects the output of the non-linear de-emphasis, the second selector selects the input of the 1 / k attenuator, and the third selector selects the output of the A / D converter. In the case of AM transmission, the first selector outputs the output of the fourth multiplier,
The second selector is controlled to select the output of the 1 / k attenuator and the third selector to select the output of the third k multiplier, and the value of k is k ≧ 1. A waveform equalizer characterized by being configured as follows. 3. The invention according to claim 1, wherein the 1 / α attenuator comprises a 1 / k attenuator and a second selector, and
a k attenuator multiplies the received analog signal by 1 / k and the second selector is connected to select the input and output of the 1 / k attenuator to supply to the A / D converter, The first multiplier is composed of a third k multiplier and a third selector, and the third k multiplier multiplies the output of the A / D converter by k and the third selector The output of the third k multiplier and the output of the A / D converter are connected so as to be selected and supplied to the synchronization / data detecting means, and the second multiplier is connected to the fourth k multiplier. And a fourth selector, wherein the fourth k multiplier multiplies the output of the adaptive filter by k and the fourth selector outputs the output of the fourth k multiplier and the output of the adaptive filter. Is selected and supplied to the first selector, and in the case of FM transmission, the first selector is connected. Is controlled to select the output of the non-linear de-emphasis, the second selector to select the input of the 1 / k attenuator, and the third selector to select the output of the A / D converter. In the case of AM transmission, when the first selector selects the output of the fourth selector, and when the second selector selects the output of the 1 / k attenuator, the third selector. Selects the output of the third k multiplier and the second selector selects the input of the 1 / k attenuator, the third selector
Waveform equalizer, wherein each selector is controlled so as to select the output of the A / D converter, and the value of k is set to k ≧ 1. 4. A transmission line distortion of a receiver which receives an analog signal transmitted by switching between AM transmission and FM transmission and digitally processes de-emphasis processing in the case of FM transmission in a subsequent stage of an A / D converter. In a waveform equalizer for equalizing a signal, an attenuator that multiplies a received analog signal by 1 / α, an A / D converter that samples an output signal of the 1 / α attenuator, and an A / D converter A first multiplier for multiplying the output signal by .alpha., A sync / data detecting means for detecting a sync signal and data of a transmission system from the output signal of the first multiplier, and the A / D conversion Filter for correcting the transmission path distortion of the output signal of the converter, non-linear de-emphasis processing means for performing non-linear de-emphasis processing on the signal waveform-equalized by the adaptive filter, and the non-linear de-emphasis processing means. And a waveform obtained by selecting the output signal of the processing means and the output signal of the adaptive filter and outputting the adaptive filter from the equalization filter and the reference signal for detecting the transmission line distortion. A waveform equalization control means for supplying a filter coefficient required for distortion correction to the equalization filter is provided. With the waveform equalization control means, in the case of AM transmission, the first selector serves as the adaptive filter. Select the output, F
In the case of M transmission, the first selector controls so as to select the non-linear de-emphasis output, and the 1 / α attenuator and the α of the first and second multipliers.
The waveform equalizer is characterized in that the value of is controlled to α ≧ 1 in the case of AM transmission and is controlled to α = 1 in the case of FM transmission. 5. The 1 / α attenuator according to claim 4, wherein the 1 / α attenuator is composed of a 1 / k attenuator and a second selector.
the k attenuator multiplies the received analog signal by 1 / k and the second selector is connected to select the input and output of the 1 / k attenuator to supply to the A / D converter, The first multiplier is composed of a third k multiplier and a third selector, and the third k multiplier multiplies the output of the A / D converter by k times and the third selector The output of the third k multiplier and the output of the A / D converter are selected to perform the synchronization / decoding.
For FM transmission, the first selector outputs the output of the non-linear de-emphasis, and the second selector inputs the input of the 1 / k attenuator. The third selector is controlled to select the output of the A / D converter, and in the case of AM transmission, the first selector outputs the output of the adaptive filter and the second selector outputs the output of the adaptive filter. The output of the 1 / k attenuator is controlled so that the third selector selects the output of the third k multiplier, and the value of k is k ≧ 1. A characteristic waveform equalizer. 6. A transmission line distortion of a receiver which receives an analog signal transmitted by switching between AM transmission and FM transmission, and digitally processes de-emphasis processing in the case of FM transmission in a subsequent stage of an A / D converter. In a waveform equalizer for equalizing a signal, an automatic gain control amplifier for controlling the amplitude of a received analog signal, an A / D converter for sampling a signal output from the automatic gain control amplifier, and the A / D conversion A multiplier for multiplying the output signal of the amplifier by α, and a synchronization / decoder for controlling the automatic gain control amplifier while detecting a synchronization signal and data of a transmission system from the output signal of the first multiplier. −
Data detection means, an adaptive filter for correcting transmission path distortion of the output signal of the A / D converter, a non-linear de-emphasis processing means for performing non-linear de-emphasis processing on the signal waveform-equalized by the adaptive filter, A second multiplier for multiplying the signal equalized by the adaptive filter by α, and a first selector for selecting and outputting the output signal of the non-linear de-emphasis processing means and the output signal of the second multiplier. Along with providing the adaptive filter, an equalization filter, and a waveform equalization control means for supplying to the equalization filter a filter coefficient necessary for correction of waveform distortion obtained from a reference signal for detecting transmission line distortion, And the waveform equalization control means
In the case of M transmission, the first selector controls so as to select the second multiplier output, and in the case of FM transmission, the first selector controls so as to select the non-linear de-emphasis output. The values of α of the 1 / α attenuator and the first and second multipliers are controlled to be α ≧ 1 in the case of AM transmission and α = 1 in the case of FM transmission. Waveform equalizer characterized by. 7. The invention according to claim 6, wherein the first multiplier is a third k multiplier and an output signal of the third k multiplier is subjected to overflow / underflow limiter O.
An F / UF limiter and a second selector, and the third selector
While multiplying the output of the A / D converter by k, the OF / UF limiter applies an overflow / underflow limiter to the output signal of the third k multiplier, and further the second The selector selects the output of the OF / UF limiter and the output of the A / D converter to synchronize / synchronize
In the case of AM transmission, the second selector is connected to each of the OF / UF limiters and is connected to supply the data detecting means. The second selector is controlled to select the output, and in the case of FM transmission, the second selector is controlled to select the output of the A / D converter, and the value of k is k ≧ 1. A waveform equalizer characterized in that 8. A transmission line distortion of a receiver which receives an analog signal transmitted by switching between AM transmission and FM transmission, and digitally processes de-emphasis processing in the case of FM transmission in a subsequent stage of an A / D converter. In a waveform equalizer for equalizing a signal, an automatic gain control amplifier for controlling the amplitude of a received analog signal, an A / D converter for sampling a signal output from the automatic gain control amplifier, and the A / D conversion A multiplier for multiplying the output signal of the amplifier by α, and a synchronization / decoder for controlling the automatic gain control amplifier while detecting a synchronization signal and data of a transmission system from the output signal of the first multiplier. −
Data detection means, an adaptive filter for correcting transmission path distortion of the output signal of the A / D converter, a non-linear de-emphasis processing means for performing non-linear de-emphasis processing on the signal waveform-equalized by the adaptive filter, A first selector that selects and outputs the output signal of the non-linear de-emphasis processing means and the output signal of the adaptive filter is provided, and the adaptive filter is an equalization filter and a reference signal for detecting transmission line distortion. And a waveform equalization control means for supplying to the equalization filter the filter coefficient required for the correction of the waveform distortion obtained from the first selector in the case of AM transmission by the waveform equalization control means. Is controlled to select the output of the adaptive filter, and in the case of FM transmission,
The first selector is controlled so as to select the non-linear de-emphasis output, the value of α of the first and second multipliers is set to α ≧ 1 in the case of AM transmission, and FM transmission is performed. In the case of, the waveform equalizer is configured so that α = 1. 9. A transmission line distortion of a receiver which receives an analog signal transmitted by switching between AM transmission and FM transmission and digitally processes de-emphasis processing in the latter stage of an A / D converter in the case of FM transmission. In a waveform equalizer for equalizing a signal, an attenuator that multiplies a received analog signal by 1 / k, an A / D converter that samples an output signal of the 1 / k attenuator, and an A / D converter Subtracting means for subtracting the digital value h from the output digital signal, synchronizing / data detecting means for detecting a synchronizing signal, data of the transmission system, etc. from the output signal of the subtracting means, and output of the subtracting means An adaptive filter that corrects signal transmission path distortion, a non-linear de-emphasis processing unit that performs non-linear de-emphasis processing on a signal whose waveform is equalized by the adaptive filter, and the non-linear de-emphasis processing unit. A first selector that selects and outputs the output signal of the linear de-emphasis processing unit and the output signal of the adaptive filter is provided, and the adaptive filter is an equalization filter and a reference signal for detecting transmission path distortion. And a waveform equalization control means for supplying the filter coefficient necessary for correcting the waveform distortion obtained from the above to the equalization filter, and in the case of AM transmission, for the specification resolution n bits of the A / D converter, And resolution m bits (n <m)
Using the A / D converter of, the above k and h values are [Equation 2] A waveform equalizer characterized by being configured as follows. 10. A transmission line distortion of a receiver which receives an analog signal transmitted by switching between AM transmission and FM transmission, and digitally processes de-emphasis processing in the case of FM transmission in a subsequent stage of an A / D converter. A waveform equalizer for equalizing the received signal, an attenuator that multiplies the received analog signal by 1 / k,
An A / D converter for sampling the output signal of the 1 / k attenuator, and a sync / data detecting means for detecting a sync signal or transmission system data from the output signal of the A / D converter. ,
An adaptive filter for correcting transmission path distortion of an output signal of the A / D converter, a non-linear de-emphasis processing means for performing non-linear de-emphasis processing on a signal whose waveform is equalized by the adaptive filter, and the non-linear de-emphasis processing means. A first selector that selects and outputs the output signal of the adaptive filter and the output signal of the adaptive filter, and the adaptive filter is a waveform distortion obtained from an equalization filter and a reference signal for detecting transmission path distortion. And a waveform equalization control means for supplying the filter coefficient required for correction of the equalization filter to the equalization filter. In the case of AM transmission, a resolution of m bits ( Using an A / D converter of n <m),
Let the value of k be And the lower n bits of the m-bit digital signal converted by the A / D converter are supplied to the adaptive filter and the synchronization / data detecting means. Waveform equalizer.