JP2000307483A - Adaptive equalizer and demodulating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the adaptive equalizer which can compensate the distortion of radio communication handling a burst signal by providing a function corresponding to a delay detection system. SOLUTION: The device is equipped with a quadrature detector 12, an oscillator 7, analog/digital converters 8 and 9, the adaptive equalizer 19 which compensate waveform distortion included in sample signals xi(k) and xq(k), and a discriminating decision circuit 17 which obtains a decoded signal by discriminating and deciding the outputs of a base band delay detecting circuit 6 and a base band delay detector 6. The adaptive equalizer 19 is equipped with a digital filter 14, a sum arithmetic circuit 5 which sums up digital filter outputs yi(k) and yq(k) and the discriminating decision result d(k) of the discriminating decision circuit 17 to estimate the true value of the adaptive equalizer output, a subtracter 16 which calculates the difference between the adaptive equalizer output and estimated true value to find an error quantity e(k), and a coefficient updating circuit 15 which adaptively updates frequency characteristics of the digital filter according to the estimated true value and error quantity of the adaptive equalizer output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adaptive equalizer and a demodulator, and more particularly, to an adaptive equalizer and a demodulator. The present invention relates to an adaptive equalizer and a demodulator for adaptively equalizing

[0002]

2. Description of the Related Art In digital radio communication, a waveform of a received signal is distorted due to fading in a radio transmission path or imperfect adjustment of a radio apparatus. Since the waveform distortion causes a code error, an adaptive equalizer for compensating for the waveform distortion is mounted on a wireless device used in an environment where severe fading is severe or a wireless device having a large number of values.

[0003] Adaptive equalizers can be classified into those comprised of analog circuits such as delay lines and variable resistors, and those comprised of digital circuits such as flip-flops, multipliers and adders. In addition, this circuit multiplies the input signal delayed by several stages by a filter coefficient and adds these to filter parts that perform filtering, and updates the filter coefficients to adaptively change the frequency characteristics of the filter part. It consists of a variable coefficient updating unit, and can be classified according to the structure of each unit. First, the filter unit can be classified into a linear filter and a non-linear filter. As an example of the former, there is no return path, and the impulse response disappears in a finite time (FIR (Finite impulse)
SE response filter (also called transversal filter), and IIR (Infinite impulse) having a feedback path and infinite impulse response.
ulse response) filter.
Also, as an example of the latter, a DFE (Decision f
eedback equalizer).
The filter unit can be classified into a structure in which taps are arranged at symbol intervals and a structure in which taps are arranged at fractional intervals of symbol time.

On the other hand, the coefficient updating unit can be classified by an adaptive algorithm. ZF (Z
ero-forcing) method, LMS (Least m
mean squares method, MSE (mean sq)
ure error method and RLS (Recurs)
live least squares) method. These adaptive algorithms sequentially update the filter coefficients so that the maximum value of the error of the actual output with respect to the true value of the output of the adaptive equalizer or the root mean square value of the error is minimized. Hereinafter, a transversal adaptive equalizer with symbol intervals using the ZF method as an adaptive algorithm will be described as an example.

FIG. 14 shows the configuration of an adaptive equalizer and the configuration of a demodulation device for quadrature modulation provided with this circuit. The demodulation apparatus includes a quadrature detector 12 for quadrature detecting a received signal to generate I- and Q-channel baseband signals, and a carrier signal synchronized with the received signal from the received signal or the baseband signal. A carrier reproduction circuit 11 for outputting to the quadrature detector 12, analog / digital converters 8 and 9 for sampling the quadrature detector output, and sample signals x _i (k) output from the analog / digital converters 8 and 9;
Adaptive equalizer 1 for compensating waveform distortion included in x _q (k)
9 and an identification determination circuit 17 for determining the output of the adaptive equalizer 19 to obtain a decoded signal.

[0006] The adaptive equalizer 19 has an I channel and a Q channel.
Flannel sample signal x_i(K), x _qFilter (k)
The digital filter 14 and the digital filter 14
Output y_i(K), y_q(K) and determination by the identification determination circuit 17
Result y^-(K) (note that y^-Indicates the y bar. Hereinafter the same
Same. And a subtractor 16 that calculates the difference between
Determination result y of identification determination circuit 17^-(K) and error amount e
Adapt digital filter frequency characteristics based on (k)
And a coefficient updating circuit 15 that updates the coefficient.

[0007] The digital filter is composed of sample signals x (k) = [x _i (k), x _q (k) of I channel and Q channel.
] ^T and the filter coefficient C (k) calculated by the coefficient operation circuit
K-th output based on

[0008]

(Equation 1)

Is calculated. Where a ^T is the vector a
Represents the transposition of Further, M and N are arbitrary natural numbers, and the number of taps of the digital filter is M + N + 1. If equation (1) is implemented by a digital circuit, the result is as shown in FIG. As shown, the digital filter is composed of four blocks 23 to 26 having the same structure and two adders 27,
28. Each block includes delay circuits 32-34 for delaying the sample signal by one symbol time;
It comprises M + N + 1 multipliers 35 to 38 and one multi-input adder 39.

FIG. 16 shows the operation of the subtractor and the discrimination determination circuit in QPSK (Quadrature phase shi).
ft keying) modulation method will be described as an example. Let the output of the equalizer be y (k) = [y _i (k), y _q (k)] ^T. The discrimination circuit determines the discrimination based on the threshold value set on the orthogonal axis of the I channel and the Q channel.

[0011]

(Equation 2)

Is output as an error amount. Next, the configuration of the coefficient updating circuit is shown in FIG. This circuit is the maximum value of the absolute value of the error

[0013]

(Equation 3)

The filter coefficient C (k) is updated so that is minimized. Here, ξ represents i or q.

[0015]

(Equation 4)

Here, μ represents a correction amount of the filter coefficient, and is called a step size parameter. Ξ and ζ represent i or q. Therefore, this circuit also includes four blocks 45 to 48 having the same structure, and corresponds to the four blocks 23 to 26 of the digital filter in FIG. Each of the blocks 45 to 48 includes delay circuits 55 to 58 and M + N + 1 arithmetic units 50 to 54 from # -N to #M. Each arithmetic unit 5
Reference numerals 0 to 54 denote encoders 59 and 60 for judging positive / negative, two multipliers 61 and 63, and an up / down counter 62.
And an accumulator 64. Two encoders 59, 60
Obtains the identification determination result and the sign of the error amount, respectively. The multiplier 61 multiplies the output of the encoder. The up / down counter 62 adds the multiplication result for a certain period of time, and further obtains the sign of the addition result. Here, N shown in FIG.
_udc is a parameter that determines the time to be added. Another multiplier 63 multiplies μ and outputs the result to the accumulator.
The accumulation result is output as a filter coefficient.

By removing the encoder of FIG. 17 and replacing the up / down counter with an accumulator,
The correction amount can be varied depending on the identification determination result and the magnitude of the error amount. Thereby, the convergence time can be shortened, and the update of the filter coefficient can be stabilized. In addition to this change, the identification determination result y ^- by entering the filter input x (k) instead of (k), MSE method can be realized. The MSE method has a larger circuit scale than the ZF method, but has a feature of excellent convergence. The LMS method is a simplified version of the MSE method.
Also, the RLS method is an algorithm that is more excellent in convergence than the MSE method. However, the RLS method further increases the circuit scale. Although the configuration shown in FIG. 17 cannot be used as it is to realize the RLS method, the filter input x
If information on (k) and the error amount e (k) can be obtained, the RLS method can also be realized.

Regarding the structure of the filter, see Takebe,
"Design of digital filter", Tokai University Press published. Regarding adaptive algorithms, see Miyagawa et al., "Digital Signal Processing," published by the Institute of Electronics, Information and Communication Engineers,
And S.I. Details by Haykin, Takebe Translation, "Introduction to Adaptive Filters", published by Hyundai Kogakusha.

[0019]

As described above, the adaptive equalizer needs the identification decision result of the output of the adaptive equalizer or the input of the adaptive equalizer and the error amount in order to obtain the filter coefficient. Also, PSK or QAM (Quadrature a)
When an adaptive equalizer is applied to an amplitude modulation scheme, the identification determination result and the error amount need to be obtained independently for the I channel and the Q channel in order to stably and reliably obtain the filter coefficient. Therefore, as shown in FIG. 16, thresholds are set on the orthogonal axes of the I and Q channels, and the discrimination judgment and the determination of the error amount are performed independently for each channel.

However, in order to make such a discrimination, it is necessary to synchronize the carriers so that the orthogonal coordinate plane formed by the output of the adaptive equalizer and the reference coordinate plane on which the threshold value is set do not deviate in time. is there. For this reason, a demodulation device having an adaptive equalizer is provided with a carrier recovery circuit as shown in FIG. Such a demodulation method for synchronizing carriers is called a synchronous detection method.

On the other hand, in mobile communications such as mobile phones and satellite communications, digital data is mainly transmitted using burst-like radio signals. Demodulators applied to these wireless communications are required to reduce the carrier synchronization time in order to efficiently cope with burst signals. However, the current carrier regeneration circuit requires time for carrier regeneration and the circuit becomes complicated,
It has become difficult to employ a synchronous detection method in a demodulator for mobile communication. For this reason, a delay detection method that does not require carrier reproduction by decoding data from the difference between two sample signals separated by one symbol is used. However, in this method, two error amounts separated by one symbol have a correlation with each other, and furthermore, an error amount between the I and Q channels also has a correlation. Therefore, there is a problem that a conventional adaptive equalizer cannot determine a filter coefficient. . Therefore, the conventional adaptive equalizer cannot cope with the delay detection method, and thus there is a problem that an adaptive equalizer cannot be employed as a means for distortion compensation in mobile communication or satellite communication that handles burst signals.

The present invention relates to an adaptive equalizer and a demodulator for adaptively equalizing waveform distortion of a digital modulation wave caused by a radio transmission path or a radio communication device, the demodulator having a function corresponding to a delay detection method, An object of the present invention is to provide an adaptive equalizer capable of compensating distortion in wireless communication using signals.

[0023]

According to a first aspect of the present invention, there is provided an adaptive equalizer for compensating for a waveform distortion of a digital modulation wave caused by a wireless transmission path and a wireless communication apparatus. Based on the output and the result of the delayed detection and discrimination determination of the adaptive equalizer output, calculating means for estimating the true value of the adaptive equalizer output, and for the true value of the estimated adaptive equalizer output, Means for determining the error amount of the output of the adaptive equalizer;
Coefficient updating means for sequentially updating filter coefficients based on the error amount and the estimated true value of the output of the adaptive equalizer.

According to the first aspect of the present invention, the adaptive equalizer is provided with arithmetic means for estimating the true value of the output of the adaptive equalizer,
Means for obtaining an error amount of the output of the adaptive equalizer with respect to the true value of the output of the adaptive equalizer, and sequentially updating the filter coefficient based on the error amount and the true value of the output of the adaptive equalizer. An adaptive equalizer that adaptively equalizes waveform distortion of a digital modulation wave caused by a wireless transmission path or a wireless communication device by providing a function corresponding to a delay detection method, Distortion compensation in wireless communication that handles

According to a second aspect of the present invention, the coefficient updating means according to the first aspect replaces the filter coefficient based on the error amount and the estimated true value of the output of the adaptive equalizer, instead of sequentially updating the filter coefficient. The filter coefficient is sequentially updated based on the error amount and the input of the adaptive equalizer. According to the second aspect of the present invention, the adaptive equalizer according to the first aspect may be an adaptive equalizer that sequentially updates a filter coefficient based on an error amount and the input of the adaptive equalizer.

According to a third aspect of the present invention, in an adaptive equalizer for compensating waveform distortion of a digital modulation wave caused by a wireless transmission path and a wireless communication apparatus, a k-th (k is an integer)
The true value of the output of the adaptive equalizer at k-th is determined based on the output of the adaptive equalizer at Calculating means for estimating, means for calculating an error amount of the output of the adaptive equalizer at the k-th with respect to the true value of the output of the adaptive equalizer estimated at the k-th, Coefficient updating means for sequentially updating filter coefficients based on a past estimated true value of the adaptive equalizer output.

According to the third aspect of the present invention, the output of the adaptive equalizer at the k-th position and the output of the adaptive equalizer at the k-th and (k-1) -th positions are detected by delay detection and discriminated and determined. calculating means for estimating the true value of the output of the adaptive equalizer at the k-th position, means for calculating the error amount of the output of the adaptive equalizer at the k-th position relative to the true value of the output of the adaptive equalizer at the k-th position, Based on the error amount in the past and the true value of the output of the adaptive equalizer estimated in the past from the k-th, it is provided with coefficient updating means for sequentially updating the filter coefficients, and is compatible with differential detection that does not require synchronous demodulation. The adaptive equalizer can make distortion compensation possible for a time-series signal in wireless communication digital transmission in which a burst occurs.

According to a fourth aspect of the present invention, the coefficient updating means according to the third aspect is configured such that the coefficient updating means is configured to calculate the error value based on the error amount past the k-th and the true value of the output of the adaptive equalizer estimated past the k-th. Instead of sequentially updating the filter coefficients, the filter coefficients are sequentially updated based on the error amount past the k-th and the input of the adaptive equalizer. According to the fourth aspect of the present invention, the adaptive equalizer according to the third aspect is an adaptive equalizer that sequentially updates filter coefficients based on an error amount past the k-th and an input of the adaptive equalizer. You may.

According to a fifth aspect of the present invention, in the adaptive equalizer according to the first or second aspect, the arithmetic means performs delay detection and identification determination based on the instantaneous phase of the output of the adaptive equalizer. Calculating means for estimating the true value of the output of the adaptive equalizer by linearly converting the output of the adaptive equalizer by the determined signal point transition angle. According to the fifth aspect of the present invention, the demodulation device uses the M-phase PSK modulation method or
When the value star QAM modulation method is adopted, the arithmetic means linearly converts the output of the adaptive equalizer by a signal point transition angle obtained by performing delay detection and identification judgment based on the instantaneous phase of the output of the adaptive equalizer. By performing the conversion, the true value of the output of the adaptive equalizer can be estimated.

According to a sixth aspect of the present invention, in the adaptive equalizer according to the third or fourth aspect, the calculating means includes a delay based on the instantaneous phase of the output of the adaptive equalizer at the k-th and (k-1) -th. K-1 obtained by performing detection and discrimination judgment
Calculating means for estimating the true value of the output of the adaptive equalizer at the k-th by linearly converting the output of the adaptive equalizer at the (k-1) -th by the signal point transition angle from the k-th to the k-th signal point transition angle;
It is characterized by having.

According to the sixth aspect of the present invention, when the demodulation device employs the M-phase PSK modulation method or the M-ary star QAM modulation method, the arithmetic means is adapted to adapt to the k-th and k-1 th modulations. Linearly converting the output of the adaptive equalizer at the (k-1) th by the signal point transition angle from the (k-1) th to the kth obtained by performing the delay detection and the discrimination judgment based on the instantaneous phase of the equalizer output Thus, the true value of the output of the adaptive equalizer at the k-th position can be estimated.

According to a seventh aspect of the present invention, there is provided a demodulation apparatus comprising the adaptive equalizer according to the first to sixth aspects. According to the seventh aspect of the present invention, there is provided a demodulator for adaptively equalizing waveform distortion of a digital modulation wave caused by a wireless transmission path or a wireless communication device, the demodulator having a function corresponding to a delay detection method, It is possible to perform distortion compensation in wireless communication to be handled.

[0033]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. This figure shows a configuration example of a demodulation device provided with the adaptive equalizer of the present invention. The demodulation apparatus includes a quadrature detector 12 for quadrature detection of a received signal and outputting I- and Q-channel baseband signals, an oscillator 7 for generating a carrier signal having a fixed period not synchronized with the received signal, Analog output sampling
The digital converters 8 and 9, the adaptive equalizer 19 for compensating for waveform distortion included in the sample signals output from the analog / digital converters 8 and 9, and the difference between the outputs of two adaptive equalizers separated by one symbol. The baseband delay detection circuit 6 to be obtained and an identification determination circuit 17 for determining the output of the baseband delay detector 6 to obtain a decoded signal are provided. The adaptive equalizer 19 performs a sum operation on the digital filter 14 for filtering the I-channel and Q-channel sampled signals, the digital filter output and the discrimination result of the discrimination circuit 17, and estimates the output of the adaptive equalizer. Summation operation circuit 5 for finding the value
A subtractor 16 for calculating the difference between the output of the adaptive equalizer and the estimated true value to obtain an error amount; and adaptively changing the frequency characteristic of the digital filter based on the estimated true value and the error amount of the output of the adaptive equalizer. And a coefficient updating circuit 15 for updating.

FIG. 2 shows a feature of the present invention in a QPSK modulation method.
The formula is shown as an example. Digital signal for adaptive equalizer
The filter 14 receives the input sample signal sequence x (k) =
[X _i(k), x_q(k)]^TMultiplied by the filter coefficient C (k)
In addition, y (k) = [y represented by Expression (1)_i(k), y
_q(k)]^TAnd y (k-1) = [y_i(k-1), y_q(k
-1)]^TIs output. Baseband differential detection circuit 6 and
And the discrimination determination circuit 17 performs delay detection based on these signals.
Then, an identification determination result d (k) is output. For example, QPSK
In the modulation method, based on the instantaneous phase of the baseband signal,
The delay detection follows the following equation.

Θ (k) = tan ⁻¹ ｛y _q (k) / y _i (k)｝ Δθ (k) = θ (k) −θ (k−1)

[0036]

(Equation 5)

Furthermore, subtractor estimated true value y according to equation (2) ^- output the difference (k) and the adaptive equalizer output y (k) as the error amount e (k). The coefficient update circuit 15 calculates the true value y ⁻ (k) of the adaptive equalizer and the error amount e (k) based on
According to equation (4), the (k + 1) th filter coefficient C (k +
Calculate 1). The digital filter 14 filters the input signal using the updated filter coefficient C (k + 1).

As described above, the present invention has a function of deriving the error amount required by the conventional adaptive equalizer and the result of discriminating the output of the adaptive equalizer from the result of the delay detection. The conventional algorithm can be used as it is as the adaptive algorithm for. Further, the digital filter configuration is the same, and the conventional filter structure can be used as it is. Therefore, the present invention can be applied to a demodulator in which it is difficult to adopt the synchronous detection method, and is effective as a means for compensating waveform distortion in wireless communication using a burst signal. (Embodiment 1) Embodiment 1 will be described with reference to FIG. First
As described above, the demodulator shown in the figure includes a quadrature detector 12, an oscillator 7, analog / digital converters 8, 9, an adaptive equalizer 19, and a baseband differential detection circuit 6, A determination circuit 17; The adaptive equalizer 19 includes a digital filter 14, a sum calculation circuit 5, a subtractor 16, and a coefficient update circuit 15.

FIG. 3 shows a specific configuration example of the baseband differential detection circuit 6 and the discrimination determination circuit 17. The baseband differential detection circuit 6 and the discrimination determination circuit 17 of FIG.
A configuration corresponding to the SK modulation method (M is an even number of 2 or more) and performing differential detection based on the instantaneous phase of a baseband signal is illustrated. The baseband differential detection circuit 6, a coordinate transformation circuit _{^{(tan -1 {y q (k}} ) / y i (k)}), a delay circuit 84, a subtractor 85, the identification judgment circuit 17 , An identification determiner 88.

The baseband differential detection circuit 6 has a terminal 8
From 1, 82, the adaptive equalizer output y (k) = [y _i (k),
y _q (k)] ^T is input. The coordinate conversion circuit 83 obtains the instantaneous phase θ (k) according to the arctangent function. This circuit is RO
It can be configured using M (Read only memory). The delay circuit 84 delays [theta] (k) by one symbol time and outputs [theta] (k-1). The subtractor 85 calculates θ (k)
And the difference Δθ (k) between θ and k (k−1) is calculated. The identification determiner 88 identifies and determines the value of △ θ (k) as any one of the M phases, and outputs the determination result d (k) and the decoded signal from the terminals 18, 20, and 80.

FIG. 4 shows a specific example of the configuration of the sum calculation circuit 5. This figure is also an embodiment corresponding to the M-phase PSK modulation method. The sum calculation circuit 5 includes two delay circuits 93 and 94
And two types of ROMs 95 and 96 and a complex multiplier 97. The sum operation circuit 5 has an adaptive equalizer output y (k)
= [Y _i (k), y _q (k)] ^T and the discrimination determination result d (k)
Are input from terminals 90 and 92. y _i (k) and y
_q (k) is delayed by one symbol time in each of the two delay circuits 93 and 94, and output as _yi (k-1) and _yq (k-1). On the other hand, d (k) is two kinds of ROMs 95 and 9
6 and cos {d (k)} and sin respectively
Output as {d (k)}. The complex multiplier 97 performs a complex multiplication of these signals, and y _i ⁻ (k) = y _i (k−1) cos d (k)｝ − y _q (k−1) sin ｛d (k)｝ ^{_{y q - (k) = y}} i (k-1) sin {d (k)} + y q (k-1) outputs a cos {d (k)} ( 8).

The sum operation circuit corresponding to only the QPSK modulation system has two delay circuits 9 as shown in FIG.
3, 94, two code converters 102 and 103 and two 4-1 selectors 100 and 101 are also possible. Each of the 4-1 selectors 100 and 101 has y _i (k)
, _Yq (k) _yi (k-1), _yq (k-1) and d (k)
Is applied.

The digital filter and the coefficient updating circuit provided in the present invention include a digital filter (FIG. 15) and a coefficient updating circuit (17th element) provided in a conventional adaptive equalizer.
FIG. The above embodiment has been described with reference to an example in which the present invention is mainly implemented using hardware. However, the operation of the above circuit is described by software,
CPU (Central Processing Unit) and DSP (Di
It is also possible to operate on a digital signal processor (digital signal processor). (Embodiment 2) As Embodiment 2, an adaptive equalizer corresponding to the M-ary star QAM modulation system (M is an even number of 2 or more) will be described.

FIG. 6 shows the configurations of the baseband differential detection circuit and the identification judgment circuit. Baseband differential detection circuit 6
Is a square addition circuit (y _i ² (k) + y _q
² (k)) This is a circuit to which 105 is added. This circuit performs the processing described in the first embodiment, and at the same time, squares the output of the input adaptive equalizer by the square addition circuit 105.
It is added and output. On the other hand, the identification determination circuit 17
This is a circuit obtained by adding one more identification discriminator 89 to the circuit of FIG. Discrimination and decision circuit 17 and, at the same time performs the processing described in Example 1, newly by the identification determiner 89 is added to determine identify the amplitude components of the adaptive equalizer output, identification determination result d _a (k) the output I do.

FIG. 7 shows the configuration of the sum calculation circuit. This circuit includes three multipliers 133 and 134 in the circuit of FIG.
This is a circuit to which 135 is added. In this circuit, in addition to the processing described in the first embodiment, the decision result d _a (k) is output to the output of the complex multiplier.
Is multiplied by α times or 1 / α times, and y (k) is output. Here, α is a constant that depends on the amplitude level ratio of the signal point of the M-value star QAM modulation method.

Embodiments 1 and 2 show the embodiments of the adaptive equalizer of the present invention corresponding to the M-phase PSK modulation system and the M-ary star QAM modulation system, respectively. It is to be noted that the adaptive equalizer according to the present invention can be realized by slightly modifying the above-described circuits depending on the modulation schemes other than the modulation schemes that can be demodulated by the delay detection scheme. Next, the effect of the present invention obtained by the computer simulation will be described in the eighth.
This is shown in FIGS. In the simulation, a Nyquist transmission system having a roll-off rate of 0.6 using QPSK as a modulation method and a baseband differential detection method as a demodulation method was used. In addition, the carrier and clock frequencies are each set to 14
The frequency was set to 0 [MHz] and 12.5 [MHz], and a case where there was no carrier frequency difference between the modulation and demodulation devices and a case where there was a difference were examined.
Further, as fading conditions, the amplitude ratio between the interference wave and the direct wave is 0.999, the delay time difference is T / 4 (T is a symbol period), and the phase difference between the interference wave and the direct wave is 4π / 5 [rad].
, The carrier-to-noise power ratio (C
NR) was infinite.

FIG. 8 shows the signal point arrangement on the I and Q orthogonal coordinates of the received signal under the fading environment. Note that the frequencies of the carriers in the modem are equal. From this figure, it can be seen that the distribution of signal points has expanded due to the influence of the interference wave, and the signal point interval has become narrower. Therefore, it is clear that the code error rate increases under this condition. On the other hand, FIG. 9 shows the signal point arrangement of the output of the adaptive equalizer under the same conditions.
The number of taps of the adaptive equalizer is five. From this figure, it can be seen that the signal points of the output of the adaptive equalizer have converged to four points, and that the waveform distortion has been compensated for by the adaptive equalizer of the present invention.

Next, FIG. 10 shows the relationship between the elapsed time from the start of the operation of the adaptive equalizer and the amount of error [△ θ (k) -d (k)] at the time of delay detection and discrimination judgment. Show. In addition,
The error amount in the figure indicates a mean square value calculated 20 times. From this figure, it can be seen that the error amount decreases to about 5 degrees at about 400 [T], and the adaptive equalizer has converged. next,
FIGS. 11, 12, and 13 show the signal point arrangement before and after the adaptive equalizer and the time change of the error amount when there is a difference of 5 [ppm] in the carrier frequency between the modems. . Because the carriers are not synchronized between the modems,
11 and 12 can be considered that the signal points in FIGS. 8 and 9 are rotated about the origin. FIG. 13 shows the relationship between the elapsed time and the error amount similarly to FIG.
From this figure, it can be seen that the adaptive equalizer has converged at about 400 [T].

Therefore, it can be said that the adaptive equalizer of the present invention does not require synchronous detection, and is useful as a distortion compensation means in a demodulation device using a delay detection method. As described above, since the adaptive equalizer of the present invention can be applied to the differential detection system unlike the conventional adaptive equalizer, it can be applied to wireless communication that handles burst signals. Further, since an adaptive equalizer generally has an effect of compensating for a shift in sample timing, the adaptive equalizer of the present invention can also be used as a clock recovery circuit in a demodulator using a delay detection method. is there.

[0050]

According to the present invention as described above, the following various effects can be obtained. According to the first aspect of the present invention, the adaptive equalizer is provided with arithmetic means for estimating the true value of the output of the adaptive equalizer, and the output of the adaptive equalizer for the true value of the output of the adaptive equalizer is estimated. Means for calculating an error amount, and coefficient updating means for sequentially updating filter coefficients based on the error amount and the estimated true value of the output of the adaptive equalizer. An adaptive equalizer that adaptively equalizes the waveform distortion of a digitally modulated wave to be provided is provided with a function corresponding to a differential detection method, and can perform distortion compensation in wireless communication that handles burst signals.

According to the second aspect of the present invention, the adaptive equalizer according to the first aspect is an adaptive equalizer that sequentially updates a filter coefficient based on an error amount and the input of the adaptive equalizer. Is also good. According to the third aspect of the present invention, the k-th adaptive equalizer output and the k-th and k-1th adaptive equalizer outputs are delay-detected and discriminated and determined. Calculating means for estimating the true value of the output of the adaptive equalizer; means for calculating an error amount of the output of the adaptive equalizer at the kth with respect to the true value of the output of the adaptive equalizer estimated at the kth; Adaptive equalization corresponding to differential detection that does not require synchronous demodulation, including coefficient updating means for sequentially updating filter coefficients based on the error amount and the true value of the adaptive equalizer output estimated in the past from the kth. By vessel
Distortion can be compensated for a time-series signal in wireless communication digital transmission in which a burst occurs.

According to the fourth aspect of the present invention, the adaptive equalizer according to the third aspect is an adaptive equalizer that sequentially updates filter coefficients based on an error amount past the k-th and an input of the adaptive equalizer. It may be a vessel. According to the fifth aspect of the present invention, when the demodulation device adopts the M-phase PSK modulation method or the M-ary star QAM modulation method, the arithmetic means is configured to perform delay detection based on the instantaneous phase of the output of the adaptive equalizer. The true value of the output of the adaptive equalizer can be estimated by linearly converting the output of the adaptive equalizer by the signal point transition angle obtained by performing the discrimination determination.

According to the sixth aspect of the present invention, when the demodulation device employs the M-phase PSK modulation system or the M-ary star QAM modulation system, the arithmetic means is adapted to adapt to the k-th and k-1 th modulations. Linearly converting the output of the adaptive equalizer at the (k-1) th by the signal point transition angle from the (k-1) th to the kth obtained by performing the delay detection and the discrimination judgment based on the instantaneous phase of the equalizer output Thus, the true value of the output of the adaptive equalizer at the k-th position can be estimated.

According to the seventh aspect of the present invention, a demodulation apparatus for adaptively equalizing waveform distortion of a digital modulation wave caused by a radio transmission path or a radio communication apparatus has a function corresponding to a delay detection method, It is possible to perform distortion compensation in wireless communication using a burst signal.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating the operation principle of the present invention.

FIG. 3 is a diagram showing a first embodiment of a baseband differential detector and an identification determination circuit.

FIG. 4 is a diagram showing a first embodiment of a sum calculation circuit.

FIG. 5 is a diagram illustrating another configuration example of the sum calculation circuit.

FIG. 6 is a diagram illustrating a second embodiment of a baseband differential detector and an identification determination circuit.

FIG. 7 is a diagram showing a second embodiment of the sum calculation circuit.

FIG. 8 is a diagram showing a result of a computer simulation and showing a signal point arrangement when waveform distortion occurs due to fading.

FIG. 9 is a diagram showing a result of a computer simulation and showing a signal point arrangement obtained by compensating waveform distortion due to fading by the adaptive equalizer of the present invention.

FIG. 10 is a diagram showing a result of a computer simulation, showing a relationship between an elapsed time since the operation of the adaptive equalizer of the present invention and the amount of error when performing delay detection and discrimination determination.

FIG. 11 is a diagram showing a result of a computer simulation and showing a signal point arrangement when waveform distortion occurs due to fading.

FIG. 12 is a diagram showing a result of a computer simulation and showing a signal point arrangement obtained by compensating waveform distortion due to fading by the adaptive equalizer of the present invention.

FIG. 13 is a diagram showing a result of a computer simulation, showing a relationship between an elapsed time from when the adaptive equalizer according to the present invention starts operation and an error amount at the time of delay detection and discrimination determination.

FIG. 14 is a block diagram showing a conventional example.

FIG. 15 is a block diagram showing a conventional example, and is a diagram showing a configuration of a digital filter.

FIG. 16 is a diagram showing the operation principle of a conventional example.

FIG. 17 is a block diagram showing a conventional example, and is a diagram showing a configuration of a coefficient updating circuit.

[Explanation of symbols]

 5 Summation calculation circuit 6 Baseband delay detection circuit 7 Oscillator 8, 9 A / D converter 10 Input terminal 12 Quadrature detector 14 Digital filter 15 Coefficient update circuit 16, 85, 102, 103 Subtractor 17 Identification judgment circuit 19 Adaptation Equalizer 18, 20 Output terminal 83 Coordinate conversion circuit 84, 93, 94 Delay circuit (T) 88, 89 Discriminator 95, 96 ROM 97 Complex multiplier 105 Square addition circuit 133, 134, 135 Multiplier

Continued on the front page F term (reference) 5K004 AA05 AA08 FA05 FG02 FG03 FH03 JG01 JH02 JJ06 5K046 AA05 EE06 EE32 EE55 EE56 EF11 EF17 EF46

Claims (7)

[Claims] An adaptive equalizer for compensating for a waveform distortion of a digital modulation wave caused by a wireless transmission path and a wireless communication device, wherein the output of the adaptive equalizer and the output of the adaptive equalizer are detected by delay detection and identified. Calculating means for estimating the true value of the output of the adaptive equalizer (hereinafter referred to as “true value”) based on the determined result; and an adaptive equalizer for the estimated true value of the output of the adaptive equalizer Adaptive equalization, comprising: means for obtaining an error amount of an output; and coefficient updating means for sequentially updating a filter coefficient based on the error amount and the true value of the output of the estimated adaptive equalizer. vessel. 2. The coefficient updating means according to claim 1, wherein said error amount and said adaptive equalization are used instead of sequentially updating a filter coefficient based on said error amount and said estimated true value of an output of said adaptive equalizer. An adaptive equalizer characterized by sequentially updating a filter coefficient based on a filter input. 3. An adaptive equalizer for compensating waveform distortion of a digitally modulated wave caused by a wireless transmission path and a wireless communication device, wherein: an output of the adaptive equalizer at a k-th position (k is an integer);
calculating means for estimating a true value of the output of the adaptive equalizer at the k-th position based on the result of delay detection of the output of the adaptive equalizer at the k-th and k-1 positions and discrimination determination; Means for calculating an error amount of the output of the adaptive equalizer at the k-th with respect to the true value of the output of the adaptive equalizer, and an error amount past the k-th and the output of the adaptive equalizer estimated past the k-th And a coefficient updating means for sequentially updating the filter coefficients based on the true value of the adaptive equalizer. 4. The coefficient updating means according to claim 3, wherein instead of sequentially updating the filter coefficients based on the error amount past the k-th and the true value of the output of the adaptive equalizer estimated past the k-th. , An adaptive equalizer characterized by sequentially updating filter coefficients based on an error amount past the k-th and the input of the adaptive equalizer. 5. The adaptive equalizer according to claim 1, wherein the output of the adaptive equalizer is linearly transformed by a signal point transition angle obtained by performing delay detection and identification determination based on the instantaneous phase of the output of the adaptive equalizer. 3. The adaptive equalizer according to claim 1, further comprising a calculating unit for estimating a true value of an output of the equalizer. 6. The k-th to k-th signal obtained by performing differential detection and discrimination determination based on the instantaneous phase of the output of the adaptive equalizer at the k-th and k-1st positions. 4. An arithmetic unit for estimating a true value of the output of the adaptive equalizer at the k-th position by linearly converting the output of the adaptive equalizer at the (k-1) -th point by the point transition angle. Or the adaptive equalizer according to 4. 7. A demodulator comprising the adaptive equalizer according to claim 1. Description: