JP2003018062A - Delay wave canceller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sneak-path canceller for utilizing asynchronous FFT(fast Fourier transform) estimation system that has enhanced tracking performance, economics and quality of signal or the like. SOLUTION: The canceller stores and input signal thereto branched from a received signal for each delay time block and analyzes the frequency of the signal, so as to enhance the tracking performance with respect to a delay wave component having a short delay time. The canceller adopts a variable delay element for a delay element in a filter, so as to attain compatibility between optimization of an elimination/suppression range of the delay wave component and the improvement of the economical efficiency. The echo canceller analogically carries out adaptive control for the amplitude and adopts full-scale processing in a digital filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a receiver for wirelessly receiving a signal from another device and a transmitter for wirelessly transmitting the signal received by the receiver to another device. The present invention relates to a wireless relay device. The present invention is
In particular, a delayed wave that arrives with a delay with respect to the signal to be relayed, for example, a sneak wave that wraps around from the transmitter to the receiver of the same wireless relay device is a signal received by the wireless relay device, particularly a component to be relayed. The present invention relates to a delayed wave canceller that removes or at least suppresses the influence exerted on a main wave. In the following description, terms such as “broadcast wave” and “channel” that are frequently used in the broadcasting field are used, but this is merely because the description is given using terrestrial television broadcasting as an example. The present invention can also be applied to relays in the wireless field other than terrestrial television broadcasting.

[0002]

2. Description of the Related Art A wireless relay device is a device that receives a signal wirelessly transmitted from another device and wirelessly transmits the received signal to the other device. For example, in a wireless relay station for terrestrial analog television broadcasting, a broadcast wave wirelessly transmitted from a master station is received, the received signal is amplified to a predetermined power, and the power amplified signal is transmitted to another wireless relay station. Alternatively, it is wirelessly transmitted to the viewer device. Further, in a wireless relay station for terrestrial analog television broadcasting, in order to prevent a failure in a device receiving the relayed broadcast wave, for example, a ghost in a viewer device, a channel different from a receiving channel is usually used. Send a broadcast wave. For example, when the broadcast wave is received from the master station on the N1th channel, the received signal is once frequency-converted from the N1th channel to the intermediate frequency, and the intermediate frequency signal is frequency-converted to the N2th channel.
Broadcast waves are transmitted on 2 channels (however, N1 ≠ N2).
Therefore, in terrestrial analog television broadcasting, a plurality of channels are required to broadcast a broadcast wave of a certain content nationwide.

On the other hand, in terrestrial digital television broadcasting in Japan, it is planned to carry out broadcasting using carriers multiplexed according to the OFDM (Orthogonal Frequency Division Multiplex) system. Broadcasting using OFDM waves is highly resistant to interference and interference, and the effect of highly correlated interference waves can be removed to some extent by received signal processing. That is, since it is difficult to cause a ghost or the like in a viewer device, it is considered to use a channel used as a reception channel also as a transmission channel in a radio relay station for digital terrestrial television broadcasting. . If this can be realized, it is sufficient to use one channel when broadcasting a broadcast wave of a certain content nationwide. That is, a so-called single frequency network (SFN: Single)
Frequency Network) and can contribute to effective use of frequency resources. A major issue in realizing such a wireless relay station is how to remove or suppress the influence of a delayed wave such as a sneak wave on a received signal.

First, the signal received by the radio relay station includes not only the main wave component but also a delayed wave component caused by a phenomenon such as multipath and wraparound. The main wave component here refers to a broadcast wave that arrives from the parent station, that is, the main wave or the parent station wave, which follows the shortest or the best of the plural radio propagation paths, generally from the parent station to the radio relay station. It is a component and generally has a higher (or sometimes lower) amplitude level than the delayed wave component. The delayed wave component mentioned here is a component of a broadcast wave that arrives at the wireless relay station after being delayed with respect to the main wave, although the signal has essentially the same content as the main wave. A typical cause of the delayed wave component is that the broadcast wave is transmitted to the wireless relay station via a propagation path different from the wireless propagation path traced by the main wave among a plurality of wireless propagation paths from the master station to the wireless relay station. Phenomenon, that is, the multipath between the master station and the wireless relay station and the broadcast wave transmitted from the wireless relay station is received by the same wireless relay station, that is, the wraparound from the transmitter to the receiver of the wireless relay station. There is. When a noticeable wraparound occurs, the loop gain of the wireless relay station from transmitter → wireless channel → receiver → transmitter exceeds 0 dB (loop oscillates), and the wireless relay station cannot relay broadcast waves normally. . For example, the safety mechanism in the wireless relay station operates and transmission stops. Therefore, for the purpose of allowing the relay operation by the wireless relay station to be normally continued, and by extension being able to continue the relay of broadcast waves without interruption, careful measures against wraparound are required.

As a measure against a delayed wave such as a sneak wave, there is a measure to provide a device for removing or suppressing the delayed wave component in the received signal. As shown in FIG. 1, the basic components of the wireless relay station are a receiving unit 10 that receives a master station wave,
A wrap-around canceller 30 is provided as the transmission unit 20 that wirelessly transmits the received master station wave, and as a device that removes or suppresses the delayed wave component in the received signal. Receiver 10
Receives the master station wave using the antenna 11 and converts the received signal from the radio frequency (RF) to the intermediate frequency (IF). The transmitting unit 20 converts the IF received signal obtained from the receiving unit 10, that is, the IF signal in the figure from IF to RF, and wirelessly transmits it from the antenna 21. Although not shown, an amplifier such as a low noise amplifier, an automatic gain control amplifier, a power amplifier, a filter for band limitation, a local oscillator for frequency conversion, a mixer, etc. are provided in the receiving unit 10 and the transmitting unit 20. It shall be provided inside or attached to them.

Further, the wraparound canceller 30 branches a part of the IF signal from a branch point 33 on the IF signal line connecting the receiving section 10 and the transmitting section 20, and inputs the signal, that is, the input signal, that is, the canceller input signal. A cancel signal is generated by utilizing the cancel signal, and the cancel signal is coupled to the IF signal at the coupling point 34 on the IF signal line. The branch point 33 and the coupling point 34 can be realized by a signal line branch, a coupler, or the like.
In the example of this figure, the branch point 33 and the coupling point 34 are on the IF signal line, but in principle, these points are from the antenna 11 through the receiving unit 10 and the transmitting unit 20 to the antenna 21.
It can be placed anywhere. Further, although the coupling point 34 is closer to the antenna 11 than the branch point 33,
It may be close to the antenna 21. Please refer to Japanese Patent Application Laid-Open No. 2001-28562 for the modifications related to the circuit connection including these. It is also possible to make such modifications to the embodiments of the invention described below.

The detour canceller 30 shown in FIG.
It has a filter 31 whose characteristics can be automatically adjusted and a control unit 32 which controls and updates the characteristics of this filter 31. To realize the characteristic control / update by the control unit 32,
It is desirable to use, as the filter 31, a digital filter whose characteristics can be set / updated by setting the tap coefficient.

For example, as shown in FIG. 2, the delay element 31
As the filter 31, a transversal filter having a configuration in which taps formed by a, a multiplication element 31b, and an addition element 31c are cascade-connected in a plurality of stages is used. The delay element 31a in each stage delays the output signal (or the input signal to the filter 31) from the delay element 31a in the previous stage for a predetermined time. Further, the multiplication element 31b in each stage multiplies the output signal from the delay element 31a in that stage (or the input signal to the filter 31) by a complex tap coefficient, and adds the element 3 in that stage.
Supply to 1c. The addition element 31c in each stage adds the output signal from the addition element 31c (or the multiplication element 31b) in the previous stage and the output signal from the addition element 31c in the previous stage, and the resulting signal is added to the addition element in the next stage. 31c (for the stages other than the last stage) or output to the connection point 34 (for the last stage).

The control unit 32 controls the characteristics of the filter 31.
It is a member to be updated. When a digital filter is used as the filter 31, the control unit 32 executes coefficient control for setting / updating the tap coefficient of the digital filter. The purpose of this control is to generate a cancel signal by the filter 31 so as to remove or at least suppress the influence of the delayed wave appearing in the received signal, especially the wraparound wave. The phenomenon of “wraparound” means that a part of the output of the transmission unit 20 passes through the antenna 21 and the radio propagation path, and
Since it is a phenomenon of reaching the antenna 11, the transfer function of the path from the branch point 33 to the coupling point 34 through the wraparound radio propagation path, that is, if the wraparound transfer function is approximately known, the characteristic of the filter 31 is adjusted based on it. Then, it is possible to generate a cancel signal capable of removing / suppressing the wraparound wave component in the received signal. For example, JP-A-200
In the canceller described in Japanese Patent 1-228562,
A cancel signal capable of removing / suppressing the wraparound wave component or its main components by estimating the wraparound transfer function according to the method conceptually shown in FIG. 3 and adjusting the characteristics of delay time, phase, and amplitude based on the result. Is being generated. Further, the multipath wave component can be similarly removed / suppressed.

The estimation method disclosed in Japanese Unexamined Patent Application Publication No. 2001-28562 obtains the frequency characteristic of the received signal by frequency-analyzing the received signal, and the frequency characteristic is regarded as a time characteristic to analyze the frequency again to delay. This is a method involving a two-step frequency analysis of obtaining a wave transfer function. The frequency analysis can be performed by discrete Fourier transform such as fast Fourier transform (FFT). FIG. 3 conceptually shows this estimation method with respect to the wraparound, focusing on the amplitude characteristic. That is, as an example of the situation where the received signal is deteriorated by the sneak wave, the received signal in the time domain shown as “OFDM wave on the time axis” in FIG. The amplitude-frequency characteristic shown as “OFDM wave on the frequency axis” is obtained in B), and the wraparound transfer function shown in FIG. 3C is obtained by performing FFT again by assuming this amplitude-frequency characteristic as a time characteristic. It means that.

In this estimation method, the amplitude frequency characteristic of the received signal becomes flat when no delayed wave is generated,
When a delayed wave is generated, a ripple waveform appears in the amplitude frequency characteristic that should be flat when the delayed wave is not generated (inside the broken line). The ripple waveform indicates the delay time, amplitude ratio, and phase difference of the delayed wave with respect to the main wave. It is a method that utilizes the fact that it has a waveform corresponding to the above, and is essentially a method that can be executed without depending on the broadcasting format such as the mode, the modulation method, and the hierarchical structure on which the broadcasting wave complies. It can seamlessly follow changes in broadcast format. It is not necessary to perform symbol synchronization / carrier synchronization with the received signal, and the circuit configuration is simple. Therefore, this estimation method is called an asynchronous FFT estimation method because it can be said that the estimation method is asynchronous with respect to broadcast waves and frequency analysis can be performed by FFT. According to the asynchronous FFT estimation method, the delayed wave can be detected in a time shorter than the period of the symbol carried by the broadcast wave. Therefore, the characteristics of the filter 31 are controlled based on the delayed wave transfer function estimated by the asynchronous FFT estimation method. As a result, the delayed wave component can be removed or suppressed by promptly following the generation and fluctuation of the delayed wave.

[0012]

As described above, the asynchronous F
By estimating the delayed wave transfer function by the FT estimation method and controlling the filter characteristics based on the result, the removal / suppression of the delayed wave component can be realized by a circuit with a simple configuration at high speed and stable operation. An object of the present invention is to improve a delayed wave canceller based on a method of estimating a delayed wave transfer function by frequency analysis of a received signal (for example, an asynchronous FFT estimation method), in particular, to improve and remove delayed waves.
The characteristic shape of the delay profile of delay wave (profile showing change / difference in amplitude etc. due to delay time) is used for compatibility between expansion of suppression object and economy, prevention of deterioration of transmission signal quality due to quantization noise, etc. The objective is to achieve by performing adaptive control of the filter characteristics.

[0013]

The delayed wave canceller according to the present invention is obtained by (1) means for branching a signal received by the wireless relay device at a predetermined branch point in the wireless relay device, and this branching. A filter for filtering the canceller input signal, a means for coupling the signal obtained from the filter with the received signal at a predetermined coupling point in the wireless relay device, and a delayed wave such as a sneak wave appearing in the received signal. An adaptive control means for adapting the characteristics of the filter to the transfer function of the delayed wave on the basis of the canceller input signal so as to remove or suppress the influence of (2) the adaptive control means. However, it is relatively fast for the transfer function of the delayed wave with a small delay time for the main wave, and relatively slow for the transfer function of the delayed wave with a large delay time. As the characteristics of the filter to adapt, by dividing the update time corresponding to the delay time with respect to the main wave is a signal to be relayed and updates the characteristic of the filter. In this way, the characteristics of the filter are divided and updated according to the delay time, for example, by updating the low-order characteristics of the filter at high speed, the delay time for the main wave component is short, and the amplitude level is generally high. The filter characteristic can be swiftly followed with respect to the wave component, that is, the delayed wave component which is most confusing with the main wave component on the delay profile and is likely to affect the signal quality.

The delayed wave canceller according to the present invention is also (1) means for branching a signal received by the wireless relay device at a predetermined branch point in the wireless relay device, and a canceller input signal obtained by this branching. And a means for coupling the output of the digital filter to the received signal at a predetermined coupling point in the wireless relay device, and eliminating the influence of a delayed wave such as a sneak wave appearing in the received signal. Or a delay wave canceller comprising adaptive control means for adapting the characteristics of the digital filter to the transfer function of the delay wave on the basis of the canceller input signal so as to be suppressed. It is a variable delay type digital filter that uses variable delay elements whose time can be individually and variably set as delay elements in each stage. And wherein the Rukoto. For example, on the delay profile, the delay time ranges from 0 to T1 and T2.
The delayed wave component appears in the range of to T3, but the delay time is T1.
In the environment where a small delayed wave component does not appear in the range of to T2, the delay time by each delay element is appropriately set by using a variable delay type digital filter as in the present invention. Range of T1 and T2
For the delayed wave component having the delay time belonging to the range of T3, the characteristics of the digital filter are made to follow, but T1 to T
It is possible not to react particularly to a delayed wave having a delay time belonging to the range of 2. Thus, the delay wave component can be removed / suppressed over a wide range / optimum range on the delay profile economically using a digital filter which has a small number of stages (the number of taps) and can be realized at low cost.

The delayed wave canceller according to the present invention is also (1) means for branching a signal received by the wireless relay device at a predetermined branch point in the wireless relay device, and a canceller input signal obtained by this branching. A filter for outputting the filtered output, means for coupling the filter output with the received signal at a predetermined coupling point in the wireless relay device, and elimination of the influence of a delayed wave such as a sneak wave appearing in the received signal or A delay wave canceller comprising: adaptive control means for adapting the characteristics of the filter to the transfer function of the delay wave based on the canceller input signal so as to be suppressed;
(2) The filter A / D-converts the canceller input signal obtained by branching, a digital filter for filtering and outputting the canceller input signal after A / D conversion, and a digital filter output for D / A Means to convert,
An amplitude adjusting circuit for adjusting the amplitude of the digital filter output after D / A conversion and providing it for the combination, and (3) the adaptive control means performs the adaptive control regarding the amplitude exclusively in the amplitude adjusting circuit. It is characterized by being controlled by In this way, a filter whose characteristics are set and controlled based on the estimated delayed wave transfer function is realized by a digital filter that filters a digital signal and an amplitude adjustment circuit that adjusts the analog signal amplitude, and adaptive control regarding amplitude is performed. By exclusively using the amplitude adjusting circuit, the reception signal and the canceller output can be combined by analog synthesis. At that time, since the A / D conversion, especially the amplitude quantization, in the delayed wave canceller can be performed with the amplitude level of the canceller input signal as a full scale, it is realized by a digital filter including adaptive control regarding the amplitude, and the received signal and the canceller are realized. As compared with the case where the coupling with the output is realized by digital synthesis, the deterioration of the transmission signal quality due to the quantization noise is less likely to occur.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. Since the present invention can be implemented as a detour canceller using the asynchronous FFT estimation method used in the radio relay station shown in FIG. 1, the radio relay station shown in FIG. 1 and FIG. On the premise of the transversal filter and the detouring transfer function estimation based on the principle shown in FIG. 3, description will be made focusing on the differences of the preferred embodiment of the present invention. Also, the reference symbols used in those figures are still used, but this is to show the correspondence,
It does not necessarily indicate that the configurations are the same.

FIG. 4 shows the members for the delay time estimation processing and the contents of the delay time estimation processing according to the embodiment of the present invention. As mentioned above, at the branch point 33,
The received signal is branched and input to the detour canceller 30 as a canceller input signal. It is this canceller input signal that is described as "coupling from received signal" in FIG. A / D converter 35 among the illustrated members
Converts the canceller input signal into digital data by sampling it at a predetermined speed. The memory 36 stores this digital data. The controller 32 uses the memory 3
Asynchronous FFT based on the data stored by
The estimation of the wraparound transfer function by the estimation method and the assignment / update of the tap coefficient of the filter 31 based on the result are executed. The "DSP", that is, a digital signal processor in the figure is an example of a means for executing frequency analysis such as FFT in the asynchronous FFT estimation method.

The memory 36 in this embodiment has a capacity capable of storing data corresponding to 8N sampling points. It is assumed that N is a power of 2 and is the minimum number of sampling points required to determine the tap coefficient of P stages of the filter 31. The memory 36 includes numbers 1 to 1 in the figure.
As shown by 8, it is divided into 8 areas for use. In the present embodiment, every time N number of sampling points of data are accumulated in the memory 36, the data is subjected to FFT (and thus the wraparound transfer function is estimated), and the tap coefficients for the first stage to the P stage are updated. Also, every time 2N sampling points of data are accumulated in the memory 36, the FFT of the accumulated data is performed.
(Then, the wraparound transfer function is estimated) and 2P from the first stage
Update the tap coefficient for the number of steps. Every time 4N sampling points of data are accumulated in the memory 36, the data is subjected to FFT (and thus the wraparound transfer function is estimated), and the tap coefficients for the first to 4Pth stages are updated. Every time 8N sampling points of data are accumulated in the memory 36, FFT (and thus estimation of a wraparound transfer function) is performed, and tap coefficients for the first stage to the 8Pth stage are allocated.
Update.

Therefore, the tap coefficients for the first to P stages are stored in the memory 36 for N sampling points, and the tap coefficients for the P + 1 to 2P stages are stored in the memory 36 for 2N sampling points. Each time data is accumulated, tap coefficients of 2P + 1 stages to 4P stages are stored in the memory 36 at 4N sampling points. When data of 4P + 1 stages to 8P stages are collected in memory 36, tap coefficients are stored in the memory 36 at 8N sampling points. Every time minute data is collected, it is assigned and updated. That is, as shown in FIG. 5, the time for which 8N pieces of data are accumulated in the memory 36 is 1
If the delay time in each stage of the filter 31 is the same, the delay time range 0 to T1 corresponding to the first stage to the P stage is ⅛ time, and the P + 1 stage to 2P stage.
1 for delay time range T1 to T2 corresponding to each stage
/ 4 of the delay time range T2 to T3 corresponding to the 2P + 1 stage to the 4P stage is ½ time and 4P.
Delay time range T3 to T corresponding to +1 to 8P stages
For 4, the tap coefficient is assigned / updated in the time of 1.

As described above, according to the present embodiment, it is possible to quickly follow a delayed wave having a short delay time with respect to the master station wave or the main wave. That is, in general, for a first-order wraparound wave having a high amplitude level and a small delay time, a multi-order wraparound wave having a lower amplitude level than the first-order wraparound wave, a multipath wave from a master station, and a multipath wave of a wraparound wave. It is possible to follow at high speed as compared with following to. The multi-order wraparound here means that a transmission signal including a wraparound wave component further wraps around. Therefore, by suppressing the influence of the first-order wraparound, the multi-order wraparound can also be suppressed.
It is more suitable for delay waves related to the delay time range in which the tap coefficient update speed is low by following the delay waves with a small delay time with respect to the master wave or main wave including the next wraparound wave at high speed. Removal suppression can be achieved.

In the above example, the capacity of the memory 36 is set to 8
Although it is set to N, if expressed more generally, the memory 36
^Has sampling points m ^nmax × N (where m,
N is a natural number of 2 or more, and nmax is a natural number). In the above example, every N points, every 2N points, every 4N
The tap coefficient of each P stage, 2P stage, 4P stage, and 8P stage is updated in four cycles of each point and every 8N point. To express this more generally, the number of divisions in the delay time range is n ^max , and the update cycle is a period during which data of m ⁿ × N sampling points is stored in the memory 36 (where n is 0). An integer not less than n ^max )
And the number of stages to be updated (the order of the characteristic) is 2 ⁿ ×
There are P stages (the characteristic of the filter 31 is 2 ⁿ × P or less (where P is a natural number)).

FIG. 6 shows a filter 31 according to this embodiment.
An example configuration is shown. Filter 31 in this embodiment
Is, for example, a variable delay type transversal filter, that is, a filter in which the variable delay element 31d is used as the delay element of each stage. The delay time by the variable delay element 31d can be individually variably set for each element. By setting the delay time, not only the estimation by the asynchronous FFT estimation method for the appropriate delay time range on the delay profile can be executed, but also the number of filter stages necessary for that can be suppressed, and thus the economical detour canceller 30 can be realized. Can be realized.

For example, as shown in FIG. 7, the delay profile of the received signal at a certain wireless relay station shows that the main wave component and the delay wave component having a high amplitude level appear in the delay time range 0 to T1. Only delayed waves having a low amplitude level appear in the ranges T1 to T2, and the delay time range T2 to T2
It is assumed that T3 is a delay profile showing that a delayed wave component having a high amplitude level appears.

In this case, in the present embodiment, for example, the first to N1th stages of the filter 31 are arranged in the delay time range 0 to T1.
The delay time ranges T1 to T2 from the N1 + 1th stage to the N2th stage.
In the delay time range T2 to T3,
To, respectively. First to N1th stages and N2th stage
The tap coefficient (complex coefficient in the figure) is assigned to the + 1st to Nth stages according to the result of frequency analysis or the like.
It is not assigned to the 1 + 1st stage to the N2th stage. Also, from the first stage
Variable delay element 3 of N1st stage and N2 + 1th stage to N3th stage
The delay time due to 1d is set to a short time comparable to the resolution, whereas the delay time due to the variable delay elements 31d of the N1 + 1th to N2th stages is necessary to “skip” the delay time range T1 to T2. Long time. That is,
The delay times by the variable delay elements 31d of the (N1 + 1) th stage to the (N2) th stage are set so that the total is T2-T1.

As described above, the delay time ranges 0 to T1 and T2 to T3, which have relatively high amplitude levels, are intensively allocated and densely covered, so that the wraparound waves belonging to the ranges are preferably removed.・ Can be suppressed. On the other hand,
For the delay time ranges T1 and T2, it is difficult to suitably remove / suppress the wraparound waves belonging to that range because the stages of the filter 31 are scarcely assigned, but the wraparound waves belonging to that range have relatively large amplitude levels. It can be said that it can be safely ignored. Regarding the multi-order rounding wave among them, the suppression of the first-order rounding wave by the tap coefficient allocation in the delay time range 0 to T1,
It can be suitably removed and suppressed.

In this embodiment, the tap coefficient is not assigned to the wraparound wave (delayed wave) having a relatively low amplitude level as described above, so that the number of stages of the filter 31 is reduced as compared with the conventional case. Alternatively, the processing range can be expanded.

For example, in order to process the entire delay time range 0 to T3, conventionally, a number of stages of about T3 / resolution was required. On the other hand, in the present embodiment, the delay time range T in which only the wraparound wave having a relatively low amplitude level exists
Since 1 to T2 are skipped, the required number of stages is about (T2-T1) / resolution-α less than the conventional one (α
Is the number of stages assigned to the delay time ranges T1 and T2). That is,
Comparing the delay time ranges 0 to T3 with each other, the present embodiment requires a smaller number of stages than the conventional one and is economical.

Further, this embodiment requires (T1
+ (T3−T2)) / resolution + α If a conventional detour canceller is configured with the same number of detours, there is a delay time range T1 to T1 + (T3−T2) in which only detour waves with relatively low amplitude levels exist. On the other hand, no stage is assigned to the delay time ranges T2 to T3 in which a sneak wave having a relatively high amplitude level exists. Therefore, when compared with the same number of stages, the present embodiment is superior in that the wraparound wave having a high amplitude level and a long delay time can be removed / suppressed.

As described above, according to the present embodiment, a wraparound wave (more generally a delayed wave) having a high amplitude level, which leads to deterioration of the transmission signal quality, is removed and suppressed over a wide delay time range, while being filtered. It is possible to suppress the number of stages of 31 and maintain and improve the economical efficiency. The variable delay element 31d is provided in front of the multiplication element 31b at the first stage. One reason is that the delayed wave whose delay time with respect to the main wave is extremely small can be excluded from the estimation target, so that the above effect is more remarkable. This is because

FIG. 8 shows how the amplitude adjusting circuit 39 in this embodiment is used. In the present embodiment, the canceller input signal is A / D converted by the A / D converter 37, the digital data obtained thereby is filtered by the filter 31 which is a digital filter such as a transversal filter, and the output of the filter 31 is D The A / A converter 38 performs D / A conversion, and the output of the D / A converter 38 is subjected to automatic amplitude adjustment by an amplitude adjusting circuit 39 and supplied to the connection point 34. In addition, the control unit 32, of the adaptive control of the characteristics of the filter 31 based on the estimated loop-in transfer function,
Amplitude control is not performed, but only adaptive control relating to delay time and phase is performed for the characteristics of the filter 31, and the amplitude is made to follow by the amplitude adjusting circuit 39 such as a variable attenuator or a variable gain amplifier. That is,
In this embodiment, the amplitude adjusting circuit 39 functions as an adaptive filter in cooperation with the filter 31 to generate a cancel signal.

Since such a configuration is adopted, according to the present embodiment, the occurrence of quantization noise when a sneak wave (delayed wave) component having an amplitude level higher than that of the main wave component is generated, As a result, the deterioration of the transmission signal quality due to it is prevented. First, conventionally, a method of combining a quantized cancel signal with a quantized received signal, that is, digital synthesis has been studied. According to this method, when a delayed wave whose amplitude level is higher than that of the main wave component is generated, the quantization scale is determined according to the delayed wave amplitude level, resulting in the number of quantization bits of the main wave component in the received signal. Will decrease. Therefore, even if the wraparound wave (delayed wave) component is preferably removed, noise associated with quantization with a small number of bits, that is, quantization noise, remains in the main wave component. On the other hand, the present embodiment employs analog synthesis in which an analog cancel signal is combined with an analog received signal. That is, although the A / D conversion is included in the series of processes for generating the cancel signal, the cancel signal to be combined with the received signal is an analog signal, and the received signal at the combined destination is not quantized. It is a signal. Further, the amplitude quantization in the detour canceller 30, that is, the A by the A / D converter 37
Since the D / A conversion can be performed with the amplitude level of the canceller input signal as a full scale, the D / A converter 38
The C / N ratio of the signal output from is good. After undergoing the amplitude adjustment by the amplitude adjusting circuit 39, that is, the adaptive control regarding the amplitude, this signal having a good C / N ratio is combined with the analog reception signal. Therefore, the transmission signal quality such as C / N
The ratio becomes higher.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a wireless relay station including a detour canceller.

FIG. 2 is a block diagram showing a configuration of a transversal filter.

FIG. 3 is a diagram showing an asynchronous FFT estimation method, in particular, (A) shows a received signal on a time axis, that is, an OFDM wave,
(B) is an amplitude-frequency characteristic obtained by frequency-analyzing it by a method such as FFT, and (C) is a wraparound transfer function obtained by frequency-analyzing it as a time characteristic by a method such as FFT. FIG.

FIG. 4 is a block diagram showing a configuration and an operation of a wraparound canceller according to an embodiment of the present invention, particularly a portion related to estimation processing for each delay time.

FIG. 5 is a delay profile diagram illustrating the appearance of first-order and multi-order wraparound components.

FIG. 6 is a block diagram showing a configuration of a detour canceller, in particular, a variable delay type transversal filter according to an embodiment of the present invention.

FIG. 7 is a delay profile diagram illustrating a range in which tap coefficients are assigned and a range in which tap coefficients are not assigned.

FIG. 8 is a block diagram showing a detour canceller according to an embodiment of the present invention, in particular, a digital signal processing section and an analog signal processing section.

[Explanation of symbols]

10 receivers, 11, 21 antennas, 20 transmitters,
30 wraparound canceller, 31 filter, 31b
Multiplication element, 31c addition element, 31d variable delay element,
32 control unit, 33 branch point, 34 connection point, 35, 3
7 A / D converter, 36 memory, 38 D / A converter, 39 Amplitude adjusting circuit.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Takashi Maruyama, inventor             5-1-1 Shimorenjaku, Mitaka City, Tokyo Japan             Wireless Co., Ltd. F-term (reference) 5K022 DD01 DD29 DD39                 5K046 AA05 HH15 HH18 HH22 HH53                       HH78                 5K072 AA04 BB14 BB25 BB27 DD15                       GG12 GG13 GG31

Claims (3)

[Claims] 1. A means for branching a signal received by the wireless relay device at a predetermined branch point in the wireless relay device, a filter for filtering a canceller input signal obtained by this branch, and a signal obtained from this filter. Means for coupling to the received signal at a predetermined coupling point in the wireless relay device, and the canceller input signal based on the canceller input signal so as to eliminate or suppress the influence of a delayed wave such as a sneaking wave appearing in the received signal. In a delay wave canceller comprising: an adaptive control means for adapting the characteristics of the filter to a transfer function of a delayed wave, the adaptive control means compares the transfer function of the delayed wave with a small delay time with respect to the main wave. It is a signal that should be relayed so that the characteristics of the above filter are adapted at a relatively high speed and at a relatively low speed for a transfer function of a delayed wave with a large delay time Delayed wave canceler and updates the characteristic of the filter divides the update time according to the delay time for. 2. A means for branching a signal received by the wireless relay device at a predetermined branch point in the wireless relay device, a digital filter for filtering and outputting a canceller input signal obtained by this branch, and a digital filter output. Means for coupling to the received signal at a predetermined coupling point in the wireless relay device, and the canceller input signal based on the canceller input signal so as to eliminate or suppress the influence of a delayed wave such as a sneaking wave appearing in the received signal. In a delay wave canceller comprising: an adaptive control unit that adapts the characteristics of the digital filter to the transfer function of the delay wave, the digital filter includes variable delay elements for which delay times can be individually and variably set. A delay wave canceller, which is a variable delay type digital filter used as a delay element. 3. A unit for branching a signal received by the wireless relay device at a predetermined branch point in the wireless relay device, a filter for filtering and outputting a canceller input signal obtained by this branch, and a filter output. Means for coupling to the received signal at a predetermined coupling point in the wireless relay device, and the delay based on the canceller input signal so as to remove or suppress the influence of a delayed wave such as a sneak wave appearing in the received signal. A delay wave canceller, comprising: adaptive control means for adapting the characteristics of the filter to a wave transfer function, wherein the filter A / D-converts a canceller input signal obtained by branching; A digital filter for filtering and outputting the converted canceller input signal, a means for D / A converting the digital filter output, and a D / A
An amplitude adjusting circuit for adjusting the amplitude of the converted digital filter output and providing the combined signal, wherein the adaptive control means performs the adaptive control concerning the amplitude exclusively by controlling the amplitude adjusting amount in the amplitude adjusting circuit. Characteristic delayed wave canceller.