JPS61135237A - Transversal equalizer - Google Patents

Abstract

PURPOSE:To always secure a proper working level range by normalizing the tap coefficient setting conditions of a transversal filter based on the maximum tap coefficient corresponding to the distortion characteristics and correcting the fluctuation of the output level. CONSTITUTION:A signal sent from a terminal 101 is supplied to a transversal filter TRF1. The TRF1 sends an output signal obtained by reducing the distortion of an input signal with the tap coefficient setting conditions controlled by a tap coefficient control signal given from a D/A converter 6 to a variable attenuator 8. Here a control circuit 2 of a tap coefficient normalizing means 9 reads the tap coefficient setting conditions out of a memory circuit 4 with the prescribed signal given from a sumbwheel switch 3 and supplies it to an arithmetic circuit 5. The circuit 5 sets the maximum tap coefficient of the TRF1 as the upper limit value in response to the distortion characteristics of the input signal sent from the terminal 101 and normalizes the setting conditions given from the circuit 4. Then the tap coefficient control signal and the level control signal are sent to D/A converters 6 and 7 via the circuit 2. The converter 7 controls the attenuator 8 with the level control signal for correction of the level fluctuation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a transversal equalizer, and particularly to a transversal equalizer that improves the applicable level range of tap coefficient control of a transversal filter.

(Prior Art) Conventionally, for example, TDMA (Time Division
ion Mu 1t-1ple Access)
In a transversal equalizer used in a communication line based on the above-mentioned system, the tap coefficients given to each tap of the transversal filter forming the main part of the transversal equalizer are based on the input In order to be applicable regardless of the distortion characteristics of the signal, the maximum value of the tap coefficient estimated from the distortion characteristics of the input signal is set in advance, and a relative The coefficient value is defined within a predetermined dynamic operation range. FIG. 4 is a block diagram showing the main parts of an example of a conventional transversal equalizer, including a transversal filter 36, a control circuit 3
7, Samir switch 38, memory circuit 39 and D-
It is configured to include an A converter 40. The transversal filter 36 is an example of a case where the number of taps is 5,
Its detailed block diagram is shown in FIG. Since the transversal filter shown in FIG. 2 will be necessary in the detailed explanation of the present invention to be described later, its operation will be briefly explained.

In FIG. 2, the signal input from the terminal 103 is 1
:3 branched into three in the high pre-do circuit 11-1 and sent to the delay element 23-1 and the weighting circuits 13 and 18. The signal delayed by the predetermined time T by the delay element 23-1 is branched into three parts in the 1:3 high preamplifier 1-2, and then sent to the delay element 23-2, the weighting circuit 14, and the
Sent to 9th. Thereafter, by the same procedure, the delay element 23
-2 and 1:3 high pre, do 11-3, delay element 23
-3 and 1:3 high pre, do 11-4, delay element 23
-4 and 1:2 Hypuri and 12 respectively, the corresponding branch signals are transmitted through weighting circuits 15 and 20, weighting circuits 16 and 21, weighting circuits 17 and 2.
Sent to 2. Needless to say, I was delayed 23-2~2'
The delay time of 3-4 is T, as in the case of the aforementioned delay element 23-1.

For weighting circuits 13 to 17 and weighting circuits 18 to 22 corresponding to each tap, tap coefficient control signals output from the D-A converter 40 in FIG. The signals are inputted via the above-mentioned weighting circuits, and the signals are combined with the branched signals described above in each weighting circuit. The output signals of the weighting circuits 13 to 17 are sent to the signal combining circuit 24 and combined, and the weighting circuit 18
22 output signals are sent to the signal synthesis circuit 25 and synthesized. The output signals of the signal combining circuits 24 and 25 are each sent to an orthogonal combining circuit 26, where they are combined with a phase difference of π/2, and outputted via a terminal 104. The transfer function H(ω) of the transversal filter in this case is given by the following equation.

In the above formula, rk (k=-2,-1,0,1,2) and dk (k=-2,=1, Ot 112) are
Weighting circuits 13 to 17 and weighting circuit 1, respectively.
Tap coefficients corresponding to 8 to 22 indicate the angular frequency. Therefore, it is possible to control the frequency characteristics of the transversal filter depending on the setting conditions of each tap coefficient described above.

In the conventional transversal type equalizer shown in FIG. The signal passes through a transversal filter 36 whose setting conditions for each tap coefficient are controlled by a coefficient control signal, and is outputted via a terminal 118 as a predetermined equalized signal. In this case, the tap coefficient control signal, a digital control signal output from the control circuit 37, is converted into an analog signal by the DA converter 40 and generated. Control circuit 3
7 is connected to the Samir switch 38), and predetermined tap coefficient setting conditions are stored in the storage circuit 3 via a predetermined output signal from the Samir switch 38.
9 is also read out and the digital control signal is output.

The tap count setting conditions stored in the memory circuit 39 are as follows:
As already mentioned above, the digital control signal is supplied via the control circuit 37 (defined by a relative coefficient value with the maximum value of the tap coefficient estimated from the distortion characteristics of the input signal as the upper limit reference value). is read out and transmitted to terminal 117 by D-A converter 40 and transversal filter 36.
The distortion of the signal input from the terminal 118 is equalized and output from the terminal 118.

(Problems to be Solved by the Invention) In the conventional transpertile equalizer described above, as described above, the maximum value of the tap coefficient under the tap count setting conditions stored in the storage circuit 39 is estimated. It is set to a specific reference value so that it can adapt to the maximum distortion of the input signal. In general, the relative operating level range of the tap coefficients corresponding to the weighting circuit of a transversal equalizer is practically too bulky with respect to the maximum standard value.
.

It is approximately 40 to 50 dB, therefore, the lower limit of the tap coefficient setting value is limited to the above level range with respect to the maximum reference value of the tap coefficient, and the operation level of the tap coefficient setting is limited to a level below that level. It is not possible to expand the range. Therefore, as the distortion of the signal input to the transversal equalizer changes. If the operating range of the setting level of the tap coefficient corresponding to each weighting circuit is in a region relatively low with respect to the maximum reference value, the lower limit value of the tap coefficient setting described above is not a constraint. There is a drawback that the tap coefficient setting operating range of the versatile equalizer is reduced and the originally expected distortion equalization characteristics are deteriorated.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the transversal equalizer of the present invention includes a plurality of delay elements connected in cascade in an input signal path, and a connection of the delay elements. a plurality of weighting circuits corresponding to signals branched from the point; a signal synthesizing means for synthesizing output signals of these weighting circuits under predetermined conditions;
a transversal filter comprising: a storage circuit that stores tap coefficient setting conditions for the weighting circuit; a control circuit that reads out the stored contents of the storage circuit; and converts an output signal of the control circuit into an analog signal; an A-D converter that outputs to each of the plurality of corresponding weighted @paths;
In the transversal equalizer, tap coefficient normalization means normalizes the tap coefficients for the plurality of weighting circuits; The apparatus includes level control means for correcting level fluctuations in the output signal of the filter via a predetermined level control signal.

(Example) Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing the main parts of a first embodiment of the present invention. As shown in the figure, the present embodiment includes a transversal filter 1, a tap coefficient normalization means 9 including a control circuit 2, a storage circuit 4, and an arithmetic circuit 5, a Samir switch 3, and a D-A converter. 6, a level control means 10 including a DA converter 7 and a variable attenuator 8.

111, the block diagram of the transversal filter #1' is shown in FIG. 2, and its operation has already been described above. The signal input to the transversal filter l via the terminal 1oit is
By passing through the transpulsal filter 1 whose tap coefficient setting conditions are controlled by the tap coefficient control signal output from the I)-A converter 6, the distortion is reduced and the output is sent to the variable attenuation 58. It will be done. The D-A converter 6 converts the digital control signal output from the control circuit 2 into an analog signal, and converts the digital control signal output from the control circuit 2 into an analog signal.
It has the function of supplying signals to each weighting circuit. Composition 1
The circuit 2 is connected to a Samir switch 3, a memory circuit 4, and an operation circuit 5, and predetermined tap coefficient setting conditions are stored in the memory circuit 4 via a predetermined output signal from the Samir switch 3. The data is read from and input to the arithmetic circuit 5. The arithmetic circuit 5 uses the tap coefficient setting conditions input from the storage circuit 4, with the investigated maximum value of the tap coefficients for the transversal filter 1 as an upper limit reference value, in accordance with the distortion characteristics of the signal input from the terminal 101. The digital control signal that is normalized in the arithmetic circuit 5 and corresponds to the coefficient setting conditions is outputted via the control circuit 2.
The signal is sent to the DA converter 6. The operation process in which the analog input and output coefficient control signals are output from the DA converter 6 and supplied to the transversal filter 1 has already been described.

The distortion equalization function of the transversal filter 1 is as described above, but it has a different system from the conventional equalizer.
In the present invention, in order to maintain the tap coefficient setting operating range related to the distortion equalization function within a predetermined proper operating range, the tap coefficient setting conditions stored in the storage circuit 4 are set to The value is normalized using the upper reference value. Therefore, the level of the equalized signal output from the transversal filter 1 varies in accordance with the upper reference value. As a countermeasure for this, the arithmetic circuit 5 has, in addition to the arithmetic function for normalizing the above-mentioned tap coefficient setting conditions, an arithmetic processing function for level correction of the input signal accompanying the normalization arithmetic processing. 5 also outputs a digital level control signal via the control circuit 2t-, and the D-A converter 7! will be sent to. In the DA converter 7, the level control signal is converted into an analog level control signal, and sent to the variable attenuator 8. In the variable attenuator 8, the level of the distortion-equalized signal input from the transversal filter 1 is equalized by the DA converter 7.
The transversal filter 1 is controlled and adjusted by the level control signal sent from the transversal filter 1 to correct level fluctuations in the input signal that occur in the transversal filter 1 as a result of normalizing the tap coefficient setting conditions, and is outputted via the terminal 102. Ru.

Next, a second embodiment of the present invention will be described.

FIG. 3 is a schematic diagram showing the main parts of the second embodiment. As shown in the figure, this embodiment includes a transversal filter 27, a tap coefficient normalization means 34 including a control circuit 28 and a storage circuit 30, a Samir switch 29, a DA conversion circuit 31, D-A converter 3
2 and a level control means 35 including a variable attenuator 33;
It is equipped with

In FIG. 3, a detailed block diagram of the transversal filter 27 is shown in FIG.
This is the same as in the embodiment.

The control circuit 28 is connected to a Samir switch 29 and an i-memory circuit 30, and the storage circuit 30 has a terminal 1.
Corresponding to the distortion characteristics of the signal input from 15, the maximum value of the tap coefficients investigated in advance is normalized as the upper limit reference value.

Coefficient setting conditions are stored. The above normalized tap coefficient setting conditions are read out through the control circuit 28 via a predetermined output signal from the Samir switch 29;
It is sent to the DA converter 31 as a digital control signal. Further, from the memory circuit 30, via the control circuit 28,
A control signal for correcting the level fluctuation in the output signal of the transversal filter 27 that occurs with the normalization of the tap coefficient setting conditions is also read out and sent to the DA converter 32. An analog level control signal is output from the DA converter 32, inputted to the variable attenuator 33, corrected for level fluctuations in the signal sent from the transversal 9 filter 27, and outputted via the terminal 116. The operations performed are the same as in the first embodiment. In this second embodiment, the normalization tap coefficient setting conditions stored in the storage circuit 30 are switched or replaced in advance in response to changes in the distortion characteristics of the signal input from the terminal 115. It is necessary to be prepared.

(Effects of the Invention) As explained in detail above, in the butterfly transversal equalizer of the present invention, the tap coefficient setting conditions of the transversal filter are set to the maximum value of the tap coefficients set corresponding to the distortion characteristics. By normalizing it as a reference value and correcting the level fluctuation of the signal output that occurs due to the normalization, the operating level range of the tap coefficient is always maintained appropriately regardless of the input signal of any distortion characteristic. This has the effect of maintaining normal distortion equalization characteristics for Km.

[Brief explanation of the drawing]

1 and 3 are diagrams showing the main parts of the first and second embodiments of the present invention, respectively, and FIG. 2 is a block diagram showing the main parts of an example of a transversal filter. FIG. 4 is a block diagram showing the main parts of a conventional transversal equalization amount. In the figure, 1, 27, 36: old transpertil filter, 2, 28, 37: control circuit, 3
．． 29,38... Namir Switch, 4,3
0゜39...Memory circuit, 5...Arithmetic circuit, 6,7,31゜32.40...D-A
Converter, 8, 33... Variable attenuator, 9, 34...
...Tap coefficient normalization means, 10°35...
...Level control means, 11-1 to 4...1:3
Hybrid circuit, 12...1:2 hybrid circuit, 13-22... Weighting circuit, 23-
1 to 4... Manufacturing element, 24, 25...
Signal synthesis circuit, 26... Orthogonal synthesis circuit.

Claims (3)

[Claims] (1) A plurality of delay elements connected in cascade in the input signal path, a plurality of weighting circuits corresponding to the signals branched from the connection point of the delay elements, and the output signals of these weighting circuits are synthesized under predetermined conditions. a transversal filter comprising: a signal synthesizing means for converting the output signal of the control circuit into an analog signal; a D-A converter that converts the signal into a signal and outputs the signal to each of the plurality of weighting circuits; and tap coefficient normalization for normalizing tap coefficients for the plurality of weighting circuits in a transversal equalizer. A transversal equalizer comprising: means for controlling the level of an output signal of the transversal filter that occurs as the tap coefficients are normalized. (2) The tap coefficient normalization means includes the storage circuit;
the control circuit; an arithmetic circuit provided corresponding to the control circuit that executes arithmetic processing including tap coefficient normalization;
and the arithmetic circuit also has an arithmetic processing function for generating the level control signal.
The transversal equalizer described in section 1). (3) The tap coefficient normalization means includes the storage circuit;
the control circuit, and the recording circuit stores both a normalized tap coefficient setting condition and a setting condition of the level control signal corresponding to the normalized tap coefficient setting condition. A transversal equalizer according to claim (1).