JP2003087217A - Sneak canceler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sneak canceler capable of accurately removing only a sneak wave even when a sneak wave whose power is larger than a master station wave arrives or a plurality of sneak waves arrive. SOLUTION: An FIR filter- T coefficient operation part 4 calculates the FIR filter coefficient of a space area canceler by using the copy of a sneak wave generated by an FIR filter- T in a time area canceler and receiving signals of respective antenna elements and an FIR filter- T coefficient compensation part 6 compensates the variation of a time area canceler output signal which is generated due to the updating of the filter coefficient of the space area canceler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wrap-around canceller, and more particularly to a sneak-canceller for removing a wrap-around wave from its own transmitting antenna observed at a receiving antenna of a relay station in a single frequency network such as digital terrestrial broadcasting. Regarding

[0002]

2. Description of the Related Art Terrestrial digital broadcasting, which is scheduled to start service in 2003, uses orthogonal frequency division multiplexing (O) as a modulation method.
FDM: Orthogonal Frequency Division Multiplexin
It has been decided to adopt g). Since OFDM is strong against multipath interference, a single frequency network (SF) that uses the same frequency in all service areas
N: Single Frequency Network) can be constructed. However, in the SFN relay station, when the radio wave emitted from the transmitting antenna wraps around to the local receiving antenna and the power of the wraparound wave becomes larger than the power of the parent station wave, loop oscillation occurs in the relay station. for that reason,
It is necessary to develop technology to eliminate the wraparound wave and prevent oscillation.

As a method of removing the sneak wave, a time domain signal processing represented by an adaptive equalizer, a space domain signal processing represented by an adaptive array or a side lobe canceller, and a space-time domain signal obtained by combining the two are used. There is processing.

A method of suppressing the wraparound wave by the time domain signal processing is, for example, a "wraparound canceller" described in Japanese Patent Laid-Open No. 11-355160, or Japanese Patent Laid-Open No. 2000-2000.
There is a "wraparound canceller" described in Japanese Patent Publication No. 341238, Koichiro Imamura, Hiroyuki Hamazumi, Kazuhiko Shibuya, Makoto Sasaki, et al., "Basic Study of Broadcast Canceller for Broadcast Wave Relay in Terrestrial Digital Broadcasting SFN", Japan Society for Image Information and Media. Journal, vol.54, No.11, pp.1568-1575, 2000.

Further, the results of the outdoor experiment using the wraparound canceller are as follows: Koichiro Imamura, Hiroyuki Hamazumi, Kazuhiko Shibuya, Makoto Sasaki, Yuyuki Owada, Warm Saeki, Takao Kanai, Reiko Fukuhara, Tohru Takase, Katsuyuki Kawase, "Broadcast wave SFN experiment at Hokutan Tarumi relay station", Technical Report of the Institute of Image Information and Television Engineers, vol.2
4, No. 43, pp. 17-23, 2000. The principle of this wraparound canceller will be described below with reference to FIGS. However, in order to simplify the explanation, all noise components are omitted.

In the notation of each variable, t is a time domain signal and ω is a frequency domain signal. n represents a symbol or sample time and n + 1 represents a variable update. With respect to n, a part that is not particularly necessary in the description will be omitted.

FIG. 8 is a block diagram showing the structure of the wraparound canceller. In FIG. 8, d (t) and D (ω) represent the master station wave and its Fourier transform, and u (t) and U (ω)
Represents a wraparound wave and its Fourier transform, and y (t), Y
(Ω) represents the signal received by the antenna 1 of the relay station and its Fourier transform, and g (t) and G (ω) represent the impulse response of the amplifier 2 of the relay station and its Fourier transform (ie transfer function). , C (t), and C (ω) represent the impulse response of the sneak path and its Fourier transform (that is, transfer function). w _T (t) and W _T (ω) are FIR (Finite I
mpulse Response) shows the time domain representation of the coefficients of the filter_T3 (ie the impulse response) and its Fourier transform in the frequency domain representation (ie the transfer function), r
(T) and R (ω) represent the output signal of the FIR filter_T3 (the duplicated signal of the wraparound wave) and its Fourier transform,
s (t) and S (ω) represent the signal (canceller output signal) at the observation point and its Fourier transform.

The FIR filter_T3 shown in FIG. 8 is shown in FIG.
The configuration is as shown in. In FIG. 9, z^-1Is
The unit delay operator 31. Replicating signal r of wraparound wave
(T) is obtained from the FIR filter_T coefficient calculation unit 4.
FIR filter_T3 coefficient w _T(T) and canceller
The force signal s (t) is calculated by the following equation.

R (t) = w _T (t) * s (t) (1) Here, “*” represents a convolution operation. When the equation (1) is expressed by Fourier transform, R (ω) = W _T (ω) S (ω) (2)

Next, the principle of the detour canceller will be described. From FIG. 8, the spectrum U (ω) of the sneak wave received by the relay station is expressed as U (ω) = C (ω) G (ω) S (ω) (3). As a result, the spectrum Y (ω) of the signal received by the relay station is: Y (ω) = D (ω) + U (ω) = D (ω) + C (ω) G (ω) S (ω). ). In addition, the spectrum S of the signal at the observation point
(Ω) is a S (ω) = Y (ω ) -R (ω) = Y (ω) -W T (ω) S (ω) ... (5). And rearranging by substituting equation (4) into equation (5), S (ω) = D (ω) / [1- {C (ω) G (ω) -W T (ω)}] ... (6) Is obtained. Thus, if the overall transfer function at the observation point and F (ω), F (ω ) = S (ω) / D (ω) = 1 / [1- {C (ω) G (ω) -W T ( ω)}] ... (7).

[0011] The signal loop interference canceller at the observation point in a state that is working ideally, S (ω) = D ( ω) ... because it is (8), cancellation conditions from the equation (6), W _T (Ω) = C (ω) G (ω) (9)

[0012] Here, the replica of the wave echo by echo canceller _{R (ω) = W T (} ω) S (ω) and the actual loop interference U (ω) = C (ω ) G (ω) S (ω) The wraparound residual E (ω) is defined by the equation (10) in consideration of the error.

[0013] is substituted into E (ω) = C (ω ) G (ω) -W T (ω) ... (10) (7) (10) the relationship, E (ω) = 1-1 / F (ω) = 1-D (ω) / S (ω) (11) is obtained. As a result, the signal S (ω) at the observation point is measured,
If a known pilot signal is used as D (ω), the wraparound residual E (ω) can be obtained. The wraparound wave can be canceled by updating the FIR filter_T coefficient W _T (ω) using E (ω).

The update of the filter coefficient is performed by the FIR filter_T coefficient calculation unit 4 in FIG. The calculation process is shown in Fig. 1.
It shows in 0. OFDM signal s of symbol n at the observation point
Estimated value D (n, ω) of the transmission signal generated from the Fourier transform S (n, ω) of (n, t) and a known pilot signal
From F (n,
ω) is calculated, and E (n, ω) is calculated by the equation (11). By performing an inverse Fourier transform on E (n, ω), the impulse response e (n, t) of the wraparound residual can be obtained. FIR filter_T coefficient update step size μ
_{If T} , the gradient of the filter coefficient (change amount Δw _T (n,
t)) is Δw _T (n, t) = μ _T e (n, t) (12), and the updated filter coefficient is expressed by the following equation.

W _T (n + 1, t) = w _T (n, t) + Δw _T (n, t) (13) By sequentially updating this filter coefficient, the condition of Expression (9) is satisfied. The cancel operation is performed.

As described above, this wraparound canceller generates a duplicated signal of the wraparound wave from the received signal at the observation point and a known pilot signal with an FIR filter, and then uses the received signal (master station wave + wraparound wave). This is to cancel the wraparound wave component by reducing it, and is called a time domain canceller. With this time domain canceller, it is possible to accurately remove the wraparound waves even when a plurality of wraparound waves arrive.

A method of removing a sneak wave by spatial domain signal processing is described in, for example, LC Godara, “Application of
Antenna Arrays to Mobile Communications, Part 2:
Beam-Forming and Direction-of-Arrival Consideratio
ns, “Proceedings of the IEEE, Aug. 1997, and Nobuyoshi Kikuma, Adaptive Signal Processing by Array Antenna, Science and Technology Publishing, 1999. Among the spatial domain signal processing, the radio wave propagation environment A technique for adaptively controlling antenna directivity is called an adaptive array.

In order to operate the adaptive array, some kind of prior information about the incoming modulated wave is necessary, and it can be divided into several methods. Among them, the minimum mean square error (MMSE: Minimum Mean Squar
Since an adaptive array based on e Error) uses a known pilot signal as prior information, it is possible to accurately direct null (reception sensitivity is 0) in the interference wave direction, and
It can be said that this method is suitable for the actual propagation environment because the null automatically follows the interference wave direction even when the arrival direction of the interference wave changes. It is also applicable when the received power of the sneak wave is larger than the received power of the master station wave. Less than,
An MMSE type adaptive array compatible with wideband signals will be briefly described with reference to FIGS. 11 to 13.

FIG. 11 shows an MMSE wideband adaptive array, and FIG. 12 shows FIR filter_p [p = 1,
..., P]. In Figure 11, ♯1~♯P represents a reception array antenna elements, x _p (t) represents the received signal of the element _p, w p (t) represents the impulse response of the FIR filter _p, y _p ( t) represents the output signal of element p, y (t) is the array antenna output signal, and d
(T) is a known pilot signal (reference signal), and e
(T) is an error signal.

Next, the operation will be described. The output signal y _p (t) at the element _p is y _p (t) = w _p (t) * x _p (t) = Σ {τ = 0, ..., N _s −1} w _p (τ) x _p (T−τ) (14) Here, N _s is the number of taps of the FIR filter_p. The array antenna output signal y (t) is the sum of the output signals of each element. The received signal and the filter coefficient at each tap of each element are arranged side by side to obtain the following N _s.
P × 1 vector x (t) = [x ₁ (t), ..., x ₁ (t− (N _s −1)), x ₂ (t), ..., x ₂ (t− (N _s −1) _{), ..., x P (t} ), ..., x P (t- (N s -1))] T ... (15a) w (t) = [w 1 (0), ..., w 1 (N s - _{1), w 2 (0)} , ..., w 2 (N s -1), ..., w P (0), ..., it is defined as _{w P (N s -1)]} T ... (15b), y (t) is y (t) = Σ {p = 1, ..., P} y p (t) = Σ {p = 1, ..., P} Σ {τ = 0, ..., N s -1} w p It can be expressed as (τ) x _p (t-τ) = w ^T (t) x (t) (16). However, the superscript “T” represents transposition.

The error signal e (t) is e (t) = d (t) -y (t) (17), and the mean value of the squares of the error signal (mean square error) E
[| E (t) | ² ] is as follows.

E [| e (t) | ² ] = E [| d (t) −y (t) | ² ] = E [| d (t) −w ^T (t) x (t) | ² ] (18) Here, E [•] represents an expected value operator. By choosing w (t) appropriately, the mean square error is minimized.

Although there are several methods for sequentially updating w (t) that minimizes the equation (18), a method based on the steepest descent method (LMS: Least Mean Square) will be described here. The optimization algorithm based on the steepest descent method is expressed by equation (19).

[0024] w (n + 1, t) = w (n, t) - (μ s / 2) ∂E [| e (n, t) | 2] / ∂ w (n, t) ... (19) here , N is the sample time, μ _s is the FIR filter_p coefficient update step size, and ∂ / ∂ w (n,
t) represents the differential operator of w (n, t). Formula (18)
The ∂E [| e (n, t ) | 2] / ∂ w (n, t) = - 2E [x (n, t) e * (n, t)] ... (20) because it is (superscript The subscript “*” represents a complex conjugate), and the equation (19) is w (n + 1, t) = w (n, t) + μ _s E [ x (n, t) e ^* (n, t)] = w (N, t) + Δ w (n, t) (21)

FIG. 13 shows the FIR filter shown in FIG.
It is a figure which shows the calculation process of the 1-P coefficient calculation part. E by the sample value average processing block of FIG. 13 [x (n, t) e
^* (N, t)] is calculated, but since it is actually difficult to calculate the expected value, the expected value operator is removed and w (n + 1, t) = w (n, t) + μ _s x (n , T) e ^* (n, t) ... (22), or by averaging an appropriate finite number (J) of sample values, w (n + 1, t) = w (n, t) + μ _s [Σ {j = 1, ..., J} x _j (n, t) e _j ^* (n, t)] / J (23).

Another method for sequentially updating the FIR filter coefficient is SMI (Sample Matrix Inversion).
And RLS (Recursive Least Squares). A description of these methods will be omitted.

When the adaptive array is applied to a relay station for digital terrestrial broadcasting, SP (Scattered Pilot) or CP (Con
tinual Pilot) is used as a reference signal. At this time,
The adaptive array functions as a spatial domain canceller that directs nulls in the direction of the wraparound wave. However, in order to form a null, the condition that the time correlation between the master wave and the wraparound wave is small is required.

Recently, many studies have been made on spatio-temporal domain signal processing which is a combination of time domain signal processing and spatial domain signal processing, but these are simply constructed by connecting an adaptive array or a side lobe canceller and an adaptive equalizer. Most of them are the ones or the ones that are characterized by high performance by combining them with the conventional diversity technology. Descriptions of these examination examples are omitted.

[0029]

The amount of fluctuation of the amplitude / phase of the wraparound wave in a certain fixed time is proportional to the size of the wraparound wave. Therefore, as the wraparound wave increases, the fluctuation exceeds the tracking capability of the canceller. The broadcast wave relay SFN at the above-mentioned “Hokutan Tarumi Relay Station”
According to the "experiment," the power ratio D / U = 0 [dB] of the master wave and the sneak wave is the limit of the canceling ability at present. However, the time domain canceller has a large number of taps of the FIR filter. The wraparound wave can be canceled.

Further, the adaptive array (spatial domain canceller) has a limitation that the number of decoupling waves that can be removed is [the number of array antenna elements-1]. Although not possible, it is possible to cancel the wraparound wave even when the power of the wraparound wave is larger than that of the master station wave.

As described above, both cancellers have a complementary relationship. Therefore, a spatio-temporal domain canceller that combines the two is effective in significantly improving the wraparound wave removal capability.

The space-time domain canceller can flexibly adopt the control algorithm. However,
Since the sneak wave is a signal delayed from the master station wave, it has a correlation with the master station wave, and the output power minimization method with direction constraint and maximum S
The NR method does not operate unless the sneak wave is larger than the master station wave. In this way, the MMSE can operate even when the desired wave and the interfering wave have a correlation, and it also corresponds to the case where the power of the sneak wave is small.

When operating the MMSE type adaptive array, (1) the transmission signal is duplicated, that is, demodulated to obtain an error from the reception signal, or (2) S from the reception signal.
It is necessary to extract only the carrier component corresponding to P to obtain an error from SP. Since (1) requires demodulation processing, the circuit scale and processing time inevitably increase. Also in the case of (2), y (t) is Fourier-transformed, only the frequency component corresponding to SP is extracted, and it is returned to the time domain signal by the inverse Fourier transform.
A calculation is needed to obtain the difference with the time domain signal corresponding to P. If these calculations are performed for each symbol, the amount of calculation will increase significantly, and the hardware configuration of the device will be complicated.

Further, as another problem of the cascade connection configuration, it is conceivable that updating the filter coefficient of the space domain canceller destroys the equilibrium state of the time domain canceller. As a result, it takes a long time for both filter coefficients to converge to the optimum value, the follow-up speed with respect to the environment change becomes slow, and the filter coefficients may diverge depending on the propagation environment.

Therefore, a main object of the present invention is to provide a sneak canceller capable of accurately removing a sneak wave even when a sneak wave having a power larger than that of a master station arrives or a plurality of sneak waves arrive. Is.

[0036]

SUMMARY OF THE INVENTION The present invention provides a spatial domain canceller having an adaptive array as a basic configuration, and a FI.
In a detour canceller in which time domain cancellers having an R filter as a basic configuration are cascaded, a replica of a detour wave generated by an FIR filter of the time domain canceller and a FIR filter coefficient of a spatial domain canceller using received signals of respective antenna elements. It is characterized by comprising FIR filter coefficient calculation means for calculating

Another aspect of the present invention is a wrap-around canceller in which a space domain canceller having an adaptive array as a basic configuration and a time domain canceller having an FIR filter as a basic configuration are cascade-connected to each other, and the time domain canceller is associated with the update of the filter coefficient of the spatial domain canceller. An FIR filter coefficient compensating means for compensating the fluctuation of the output signal by the FIR filter of the time domain canceller is provided.

Furthermore, another invention is a wrap-around canceller in which a space domain canceller having an adaptive array as a basic configuration and a time domain canceller having an FIR filter as a basic configuration are cascade-connected, and the FI of the time domain canceller is used.
A replica of the wraparound wave generated by the R filter and the FIR of the spatial domain canceller using the received signals of each antenna element.
An FIR filter coefficient calculating means for calculating a filter coefficient and an FIR filter coefficient compensating means for compensating the fluctuation of the output signal of the time domain canceller due to the update of the filter coefficient of the spatial domain canceller by the FIR filter of the time domain canceller are provided. To do.

Further, the time domain canceller FI converts the duplicated signal of the sneak wave from the received signal and the known pilot signal.
It is characterized in that it is generated by the R filter and is canceled from the received signal to cancel the wraparound wave component.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a detour canceller according to an embodiment of the present invention. In FIG.
d (t), D (ω ) denotes a Fourier transform to the parent station _{wave, u 1 (t) ~u P} (t), U 1 (ω) ~U P (ω) is an antenna ♯1~♯P Showing the wraparound wave and its Fourier transform, which arrive at x ₁ (t) to x _P (t), X ₁ (ω) to X
_P (ω) represents the received signals at the antennas # 1 to #P and their Fourier transforms. w ₁ (t) to w _P (t), W
₁ (ω) to W _P (ω) is a time domain representation (that is, impulse response) of the coefficients of the FIR filters_1 to _P connected to the antennas # 1 to #P and a frequency domain representation (that is, transmission) that is a Fourier transform thereof. Function), y (t), Y (ω)
Is the signal received at the relay station and its Fourier transform, g
(T) and G (ω) are the impulse response of the amplifier of the relay station and its Fourier transform (ie transfer function), c ₁ (t) ~
c _P (t), C ₁ (ω) to C _P (ω) are impulse responses of the sneak path and its Fourier transform (that is, transfer function), w _T (t), W _T (ω) are of the FIR filter_T. The time domain representation of the coefficients (ie impulse response) and its Fourier transform, the frequency domain representation (ie transfer function), r (t), R (ω) is the FIR filter_T output signal (a wraparound wave replica signal) and its Fourier Transformation, s
(T) and S (ω) are signals (canceller output signals) at the observation point and their Fourier transforms, Δy (t), and ΔY (ω).
Represents the spatial domain canceller output variation and its Fourier transform.

The main purpose of the FIR filters_1 to P shown in FIG. 1 is to form nulls in a wide band in the array antenna directivity. In addition, the effect of compensating for the linear distortion that occurs when the ratio of the bandwidth of the OFDM signal to the radio center frequency (ratio band) is large. The tap numbers of the FIR filters_1 to P are determined according to the actual system.

FIG. 2 is a block diagram showing a calculation process of the FIR filter_T coefficient calculation unit shown in FIG. Although the calculation process in the FIR filter_T coefficient calculation unit 4 is the same as that in FIG. 10, description thereof will be omitted. Here, the updated filter coefficient is w _T ′ (n, t), which is the FIR filter_
It is a coefficient before T compensation.

Further, the FIR filter_T coefficient change amount Δw
_T (n, t) is output to the spatial domain canceller processing determination unit 7 for each symbol, and S (n, ω) is F for each symbol.
It is output to the IR filter_T coefficient compensator 6.

FIG. 3 is a block diagram showing the structure of the spatial domain canceller processing determining section 7, and a method of determining whether or not to process the filter coefficient of the spatial domain canceller will be described with reference to FIG. Here, first, with respect to the change amount Δw _T (n, t) of the FIR filter_T coefficient output from the FIR filter_T coefficient calculation unit 4, the maximum value Δw _TM (n, t) of those absolute values is obtained. That is, Δw
_TM (n, t) is the maximum slope value of the FIR filter_T coefficient. Next, Δw _TM (n, t) is compared with an arbitrary threshold value. As a result, the processing determination value takes a value of 0 or 1.

Processing determination value = 1: threshold value> Δw _TM (n, t) 0: threshold value ≦ Δw _TM (n, t) (24) This processing determination value is FIR filter_1 to symbol for each symbol.
It is output to the P coefficient calculation unit. The threshold value is selected as an appropriate value depending on the size of the sneak wave and the convergence of the time domain canceller.

FIG. 4 is a block diagram showing the configuration of the FIR filter_1 to P coefficient calculation unit 8 of FIG. In FIG. 4, the processing determination values output from the spatial domain canceller processing determination unit 7 are the FIR filter_1 to P coefficient calculation unit internal 8
Sent to the switch. If the processing determination value is 0, FI
The R filter_1 to P coefficient change amount Δw _p (n, t) becomes 0, and the coefficients of the FIR filters_1 to P are not updated.

When the coefficients of the FIR filter_T have converged to some extent, the processing determination value of the equation (24) becomes 1, and the spatial domain canceller processing determination unit updates the coefficients of the FIR filters_1 to P of the spatial domain canceller. 7 gives instructions.

When the replica signal r (n, t) of the wraparound wave converges to some extent, an error signal e (n, t) which is a difference signal between the master station wave d (n, t) and the array antenna output signal y (n, t).
t), so the spatial domain canceller is MMSE
The operation will be equivalent to and will converge. In addition,
r (n, t) does not necessarily have to converge depending on the situation. For example, if the wraparound wave is large, r (n,
Even if t) is not converged, the component of the wraparound wave becomes dominant in r (n, t), and the spatial domain canceller operates so as to cancel this component.

Ideally, the expected value E [x _p (n, t) r ^* (n, t)] is calculated in the sample value averaging block of FIG. 4, but the expected value is actually calculated. Since it is difficult, one symbol, that is, the sample value of the symbol n is averaged and used as an expected value.

As described above, FIR filter_1
~ P coefficient calculation unit 8 is the spatial domain canceller processing determination unit 7
Based on the processing determination value output from the FIR filter
1 to P coefficient is output. Letting this be w _p ″ (n, t), the following equation is obtained.

Process determination value = 0 → w _p ″ (n, t) = w _p (n, t) (25) Process determination value = 1 → w _p ″ (n, t) = w _p (n, t) ) + Δw _p (n, t) (26) Here, Δw _p (n, t) = − μ _s E [x _p (n, t) r ^* (n, t)] (27).

The updated FIR filter_1-P coefficients are output to the FIR filters_1-P. The configurations of the FIR filters_1 to P are the same as those in FIG. Also, FI
The R filter_1 to the P coefficient calculation unit 8 calculates Δw for each symbol.
_p (n, t) is a spatial domain canceller output variation calculator 9
Output to.

Next, in order to explain the operation of the detour canceller when the coefficients of the FIR filter filters_1 to P are updated by the equation (26), the signal S (ω) at the observation point is formulated using FIG. Turn into. The spatial domain canceller output signal Y (ω) is: Y (ω) = Σ {p = 1, ..., P} W _p (ω) X _p (ω) = Σ {p = 1, ..., P} W _p ( ω) {D (ω) + U _p (ω)} = D (ω) Σ {p = 1, ..., P} W _p (ω) + G (ω) S (ω) Σ {p = 1, ..., P } W _p (ω) C _p (ω) (28) The signal at the observation point S (omega) is the S (ω) = Y (ω ) -R (ω) = Y (ω) -W T (ω) S (ω) ... (29). As a result, by substituting the equation (28) into the equation (29) and rearranging the equation, the equation (30) is obtained.

[0054]

[Equation 1]

[0055] By the way, when the coefficients of the FIR filter _1~P is updated w _p (n, t) from the w _p "(n, t) to,
S (ω) in equation (30) is affected by that. Formula (11)
As shown in equation (13), the time domain canceller calculates the wraparound residual E (ω) using this S (ω), and returns it to the time domain signal e (t) by the inverse Fourier transform to obtain the FIR.
The amount of change in the filter_T coefficient is calculated, and the filter coefficient is updated.

By repeating this operation for each symbol, the FIR filter_T coefficient converges, but S (ω)
Is affected by changes in the coefficients of the FIR filters_1 to P, the equilibrium state of the time domain canceller that has converged collapses. Furthermore, a vicious circle occurs in which the error again causes a filter coefficient calculation error of the spatial domain canceller, and the filter coefficients of the time domain and spatial domain canceller may diverge.

Therefore, in order to prevent such a vicious circle, the detour canceller has a compensation function of adjusting the FIR filter_T coefficient. The compensation function will be described below. In the explanation, the following variables are defined.

W _p ″ (n, ω) = W _p (n, ω) + ΔW _p (n, ω) (31) W _T ″ (n, ω) = W _T (n, ω) + ΔW _C (n , Ω) (32) Here, the expressions (31) and (32) are both expressions in the frequency domain, and the expression (31) is different from the expression (26) by W
_T (n, ω) is the FIR filter_T at symbol n
And ΔW _C (n, ω) is the coefficient of FIR filter_T
Is the compensation coefficient of. Further, the transfer function of the amplifier and the transfer function of the sneak path are expressed as follows.

G (n, ω) = G (33) C _p (n, ω) = C _p (34) At this time, W _p ″ (n, ω) and W _T ″ (n, ω) The signals S ″ (n, ω) at the corresponding observation points, and W _T (n, ω)
ω) and the signal S at the observation point corresponding to W _p (n, ω)
Each of (n, ω) is expressed by the following equation.

[0060]

[Equation 2]

In order to eliminate the influence of the changes in the FIR filter_1 to P coefficients, it is sufficient that S ″ (n, ω) and S (n, ω) are the same. S ″ (n, ω) = S (n , Ω), formulas (35) and (36) are arranged, and further formulas (28),
Solving for ΔW _C (n, ω) using the relationship of equation (29), the relationship ΔW _C (n, ω) = ΔY (n, ω) / S (n, ω) (37) is obtained. To be Here, ΔY (n, ω) = Σ {p = 1, ..., P} ΔW _p (n, ω) X _p (n, ω) ... (38). ΔY (n, ω) is the Fourier transform of the amount of change in the spatial domain canceller output signal due to the change in the coefficients of the FIR filters_1 to P.

Next, the process of compensating the FIR filter_T coefficient will be described in accordance with the above principle. The inverse Fourier transform of the signal Δy (n, t) corresponding to the Fourier transform ΔY (n, ω), that is, ΔY (n, ω), is obtained by the spatial domain canceller output change amount calculation unit 9 shown in FIG.

FIG. 5 is a block diagram showing the configuration of the spatial domain canceller output variation calculation section 9. The spatial domain canceller output variation is calculated by comparing the signal received by the array antenna with F
FI output from IR filter_1 to P coefficient calculation unit 8
It is calculated from the R filter_1 to the P coefficient change amount by the following formula.

Δy (n, t) = Σ {p = 1, ..., P} Δw _p (n, t) * x _p (n, t) ... (39) Calculated by the spatial domain canceller output variation calculation unit 9 Δ
y (n, t) is output to the FIR filter_T coefficient compensating unit 6.

FIG. 6 is a block diagram showing the structure of the FIR filter_T coefficient compensator 6. In FIG. 6, Δy
After Fourier transform of (n, t), the compensation coefficient ΔW _C (n, ω) of the FIR filter_T is calculated by complex division of Expression (37). This compensation coefficient is Δw _C by the inverse Fourier transform.
Convert to (n, t). As a result, the FIR filter_T
The coefficient of the compensator 6 is: w _T (n + 1, t) = w _T ″ (n, t) + Δw _T (n, t) = w _T (n, t) + Δw _T (n, t) + Δw _C (n, t) = w _T '(n, t) + Δw _C (n, t) (40)

The flow of the filter coefficient updating operation of the detour canceller of the present invention based on the above principle can be summarized and shown by the flowchart shown in FIG. An outline of the filter coefficient updating operation will be described with reference to FIG.

Step SP (abbreviated as SP in the figure)
At 1, the filter coefficient is initialized and reception is started. The symbol is received in step SP2, and the change amount of the coefficient of the FIR filter_T3 is calculated by the FIR filter_T coefficient calculation unit 4 in step SP3.
In step SP4, the spatial domain canceller processing determination unit 7 determines whether the spatial domain canceller processing determination value is "0" or "1". This determination is based on equation (24). If the determination value is "1", in step SP5, the FIR filter_1 to the P coefficient calculator 8 calculates the FIR filter_1 to the FIR filter_1 based on the calculation formula in step SP6.
The P coefficient change amount is calculated. Then, in step SP7, the FIR filter_1 to P coefficient calculation unit 8 updates the coefficients of the FIR filters_1 to P with the calculated coefficients.

On the other hand, the spatial domain canceller output variation calculating section 9 computes the spatial domain canceller output variation based on the equation (39) in step SP8, and the FIR filter_T coefficient compensating section 6 uses the computing equation of step SP10. Based on the calculated coefficient, the coefficient of the FIR filter_T3 is updated with the calculated coefficient in step SP11.

In step SP4, if the spatial domain canceller processing determination value is "0", FIR filters 1 to
The coefficient of P is not updated and the calculation of step SP12 is performed, and the coefficient of the FIR filter_T3 is updated with the calculated coefficient in step SP11.

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

[0071]

As described above, according to the present invention, by forming the space-time domain canceller in which the space-domain canceller and the time-domain canceller are combined, a sneak wave having a larger power than the master station wave arrives. In this case, even when a plurality of wraparound waves arrive, it is possible to remove the wraparound wave with high accuracy.

Further, the configuration is such that the spatial domain canceller operates only when the slope of the filter coefficient of the time domain canceller is smaller than the threshold value, and the time domain canceller output signal that fluctuates when the filter coefficient of the spatial domain canceller is updated. By adding the function of compensating with the FIR filter of the time domain canceller, divergence of both cancellers can be prevented.

Further, it is possible to use the copy of the wraparound component obtained by the time domain canceller as an error signal necessary for updating the filter coefficient of the space domain canceller without hindering the convergence operation of the time domain canceller. As a result, [pilot signal-spatial domain canceller output signal]
It is possible to significantly reduce the calculation amount without needing to perform the calculation of, and it is possible to simplify the hardware configuration when the device is used.

Further, it has the advantages of both the time domain and spatial domain cancellers, and can realize a cancellation characteristic superior to the case of using either alone.

[Brief description of drawings]

FIG. 1 is a block diagram of a detour canceller according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a calculation process of an FIR filter_T coefficient calculation unit shown in FIG.

FIG. 3 is a block diagram showing a configuration of a spatial domain canceller processing determination unit shown in FIG.

FIG. 4 is a block diagram showing a configuration of FIR filter_1 to P coefficient calculation section shown in FIG. 1.

5 is a block diagram showing a configuration of a spatial domain canceller output change amount calculation unit shown in FIG. 1. FIG.

6 is a block diagram showing a configuration of an FIR filter_T coefficient compensator shown in FIG.

FIG. 7 is a flowchart showing a filter coefficient updating operation of the detour canceller according to the embodiment of the present invention.

FIG. 8 is a diagram showing a principle of a time domain wraparound canceller.

9 is a block diagram showing a configuration of the FIR filter_T shown in FIG.

10 is a block diagram showing a configuration of an FIR filter_T coefficient calculation unit shown in FIG.

FIG. 11 is a block diagram showing an MMSE wideband adaptive array.

12 is a block diagram showing a configuration of an FIR filter_p shown in FIG.

FIG. 13 is a block diagram illustrating an LMS-based FIR filter_p coefficient updating process.

[Explanation of symbols]

3 FIR filter_T, 4 FIR filter_T coefficient calculation unit, 5 transmission antenna, 6 FIR filter_T coefficient compensation unit, 7 spatial domain canceller processing determination unit, 8 F
IR filter_1 to P coefficient calculation unit, 9 Spatial domain canceller output change amount calculation unit.

Continued front page    (72) Inventor Norikachi Omi             1-3-3 Shimaya, Konohana-ku, Osaka Sumitomo Electric             Ki Industry Co., Ltd. Osaka Works (72) Inventor Yoro Okada             1-3-3 Shimaya, Konohana-ku, Osaka Sumitomo Electric             Ki Industry Co., Ltd. Osaka Works F-term (reference) 5K022 DD01 DD23 DD33                 5K046 AA05 BB00 EE57 HH56 HH68

Claims (4)

[Claims] 1. A wrap-around canceller in which a space-domain canceller having an adaptive array as a basic configuration and a time-domain canceller having a FIR filter as a basic configuration are cascade-connected, and a replica of a wrap-around wave generated by an FIR filter of the time-domain canceller. And a wrap-around canceller, comprising FIR filter coefficient calculating means for calculating the FIR filter coefficient of the spatial domain canceller using the received signals of the respective antenna elements. 2. A wrap-around canceller in which a space domain canceller having an adaptive array as a basic configuration and a time domain canceller having an FIR filter as a basic configuration are cascade-connected, and a time domain canceller output signal accompanying update of a filter coefficient of the spatial domain canceller. The wrap-around canceller, further comprising FIR filter coefficient compensating means for compensating for the fluctuation of the above by the FIR filter of the time domain canceller. 3. A wrap-around canceller in which a space-domain canceller having an adaptive array as a basic configuration and a time-domain canceller having a FIR filter as a basic configuration are cascade-connected, and a replica of a wrap-around wave generated by the FIR filter of the time-domain canceller. And FIR filter coefficient calculation means for calculating the FIR filter coefficient of the spatial domain canceller using the received signals of the respective antenna elements, and the fluctuation of the output signal of the time domain canceller due to the update of the filter coefficient of the spatial domain canceller. A wrap-around canceller, comprising FIR filter coefficient compensating means for compensating with the FIR filter of the canceller. 4. The time domain canceller generates a duplicated signal of a wraparound wave from the received signal and a known pilot signal by the FIR filter, and cancels the wraparound wave component by subtracting it from the received signal. Item 5. The wraparound canceller according to any one of items 1 to 3.