KR100540170B1 - Apparatus and method of digital tv receiver for beam-forming using direction of arrival estimation of main path signal - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a beamforming apparatus using the estimation of the incident angle of the main path signal, and a method thereof.

2. The technical problem to be solved by the invention

Provided is a beamforming apparatus and method for improving the reception performance of a DTV receiver by estimating the incident angle of a main path signal among multipath signals.

3. Summary of Solution to Invention

An incidence angle estimating means for determining an incidence angle at which the spatial spectrum of the multipath signal is the maximum as an incidence angle of a main path signal, and applying a weight calculated based on the determined incidence angle to the multipath signal for the determined main path signal incidence angle Beam forming means for forming a pattern and adding means for summing outputs of the beam forming means and outputting them to the channel equalizing means.

4. Important uses of the invention

Used in digital TV receivers

DTV, multipath, main path signal, incident angle estimation, beamforming

Description

Beamforming Apparatus and Method for Digital TV Receiver Using Estimation of Incidence Angle of Main Path Signal {APPARATUS AND METHOD OF DIGITAL TV RECEIVER FOR BEAM-FORMING USING DIRECTION OF ARRIVAL ESTIMATION OF MAIN PATH SIGNAL}             

1 is an exemplary configuration of a conventional DTV receiver.

2 is a view for explaining a conventional selective beam forming method.

3 is a detailed configuration diagram of an embodiment of a DTV receiver to which the present invention is applied.

4 is an exemplary diagram for estimating an angle of incidence of a received main path signal using spatial spectrum.

5 is a detailed flowchart of an embodiment of an incident angle estimation algorithm according to the present invention;

6 is an exemplary view showing a beam pattern of a beam former in a DTV receiver to which the present invention is applied.

* Explanation of symbols for the main parts of the drawings

101 antenna means 102 demodulation means

103 channel equalization means 310 antenna means

320: demodulation means 330: incident angle estimation means

340: beam forming means 350: adding means

360: channel equalization means

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital TV (DTV), and more particularly, to a beamforming apparatus using estimation of an incident angle of a main path signal, which improves reception performance of a DTV receiver by estimating an incident angle of a main path signal among multipath signals. And to a method thereof.

The signal transmitted from the digital broadcast transmitter is transmitted to the receiver under the influence of a channel, and the effects of the channel include multipath, Doppler frequency, and dynamic channel for mobile reception.

On the other hand, the mobile channel has a Rayleigh fading channel characteristic with little amplitude difference between a desired main path received signal and an undesired multipath received signal and a frequency selective slow fading variable channel characteristic. The receiver of VSB (Vestigial SideBand) DTV system in such a poor Ray-Lay fading channel environment is applied to the channel equalizer using LMS (Least Mean Square), RLS (Recursive Least Squares), Kalman algorithm, etc. The interference of the dynamic multipath was eliminated.

1 is an exemplary configuration diagram of a conventional DTV receiver. As shown in FIG. 1, the signal affected by the multipath channel is received by the antenna means 101, converted into a baseband signal through the demodulation means 102, and then input to the channel equalization means 103. The demodulation means 102 performs a synchronization process such as frequency synchronization and symbol timing. The distortion of the signal by the multipath channel is eliminated in the channel equalization means 103.

However, in the conventional VSB (Vestigial SideBand) DTV system, when the multipath signals having similar magnitudes, such as the Rayleigh channel, are received, it is difficult to compensate in the channel equalization means 103 of the receiver.

Since the channel equalizer of the conventional VSB (Vestigial SideBand) DTV system does not completely detect the desired main path signal and track the variable channel characteristics, there is a detection and tracking error in the output signal of the channel equalizer. Since this error acts as a new noise source that is independent of ambient noise of the transmission channel, there is a problem in that the value of the threshold of visibility (TOV), which is the minimum signal-to-noise ratio that can recover the original signal in the DTV, increases. That is, in a mobile channel environment having a ray lay fading channel characteristic, an equalization performance sufficient for restoring the original signal cannot be obtained only by the channel equalizer.

In order to solve this problem, a technique for removing interference of dynamic multipath by applying spatial signal processing technique using beamforming has been introduced in a VSB type DTV system. According to the conventional technology, the performance of the receiver can be improved by forming a beam in a direction in which the interference of the multipath is minimized by applying the spatial signal processing technique.

Among the beamforming methods to which the spatial signal processing technique is applied, a switched beamforming method is known.

The selective beamforming method performs a function of canceling a multipath signal received in an undesired orientation by forming a plurality of beams facing a predetermined orientation, and forming a beam directed in a direction in which a desired signal exists. Here, a method of forming a beam having a desired signal among the k beams formed may be performed by comparing a received power of each beam. In this case, since the selective beamforming method has a beamforming weight directed to a predetermined orientation, it can be applied even if no signal is known in advance.

However, according to this prior art, the angle of incidence of the main path signal is still unknown and only forms a beam pattern in multiple directions and forms a beam based on the signal incident in each beam pattern.

2 is a view for explaining a conventional selective beam forming method. Since the incidence angle of the main path signal is not known as shown in FIG. 2, the incidence angle of the main path signal is unknown and only a beam pattern is formed in a plurality of directions, and a beam is formed based on the signal incident in each beam pattern. In this case, since the number of beam patterns is limited, in the worst case, the reception rate of the DTV receiver is degraded when the main path signal is incident between adjacent beam patterns and another multipath signal is incident with the greatest gain for the selected beam pattern. There is this.

The present invention has been proposed to solve the above problems, and estimates the incidence angle of the main path signal of the multi-path signal to obtain the weight for beam formation to estimate the incidence angle of the main path signal which can improve the reception performance of the DTV receiver. It is an object of the present invention to provide a beam forming apparatus and a method thereof.

In order to achieve the above object, the present invention provides a beam forming apparatus for a receiver of a digital TV having an array antenna and channel equalization means, wherein the spatial angle of the multipath signal received and demodulated by the antenna is maximized. An incidence angle estimation means for determining an incidence angle of a path signal, beam forming means for forming a beam pattern with respect to the determined main path signal incidence angle by applying a weight calculated based on the determined incidence angle to the multi-path signal, and Provided is a beam forming apparatus comprising an adding means for summing the outputs and outputting the sum to the channel equalizing means.

Also, in order to achieve the above object, the present invention provides a method for beamforming a receiver of a digital TV having an array antenna and channel equalization means, the first step of demodulating a multipath signal received by the antenna, the demodulated multiplex. A second step of determining an incident angle at which the spatial spectrum of a path signal is maximized as an incident angle of a main path signal, and applying a weight calculated based on the determined angle of incidence to the multi-path signal for the determined main path signal incident angle And a fourth step of summing the multipath signals with weights according to the beam pattern formed by the third step and outputting the multipath signals to the channel equalization means.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a detailed configuration diagram of an embodiment of a DTV receiver to which the present invention is applied. As shown in FIG. 3, the DTV signals received at each antenna element (antenna 1 to antenna N) of the array antenna means 310 are respectively input to the demodulation means 320. Then, a baseband signal is output from each demodulator (demodulator 1 to demodulator N) of the demodulation means 320. The baseband signal is expressed by Equation 1 below.

....

....

Here, X _D is a vector for signals input to the D-th antenna element of each antenna element of the array antenna means 310, N is the number of antenna elements, and k is the number of received signals.

Meanwhile, vectors X ₁ to X _N representing the input signal are provided to the incident angle estimating means 330, and the incident angle estimating means 330 estimates the incident angle using the X ₁ to X _N vectors. The method of estimating the incident angle will be described later in detail.

When the incident angle is estimated as described above, the beam forming unit 340 obtains the weight vector W expressed by Equation 2 using the estimated incident angle.

In this case, when the incidence angle of the main path signal is estimated according to the present invention, the weight vector W is a vector having a (N × 1) dimension, and the estimated incidence angle and between the respective antenna elements constituting the antenna means 310 are measured. Can be found using distance. That is, the weight vector W may be obtained by adding the phase difference corresponding to the distance between each antenna element to the estimated incident angle. The W vector has a property of W ^H W = 1 and maximizes the power of the output signal y (k) of the beam forming means 340, where W ^H is a hermitian vector of the vector W. Represents a conjugate transpose matrix of W.

When the weight vector W is obtained as described above, the beam forming means 340 forms a beam using the weight vector, and the adding means 350 outputs a signal obtained by adding the formed beams. At this time, the output Y (k) of the adding means 350 is as shown in [Equation 3] and [Equation 4].

The output Y (k) of the adding means 350 is transmitted to the channel equalizing means 360, and the channel equalizing means 360 removes the influence of the remaining channel of the output Y (k) of the adding means 350. It will play a role.

The method of estimating the incident angle includes a delay sum method and a capon method.

The delay sum method is a method of directing the antenna beam in each direction, measuring the power, and then estimating the direction indicating the largest output as the angle of incidence of the signal. The linear combination is then combined to obtain the output for each direction. The car phone method satisfies the constraints of maintaining a constant gain with respect to the directing direction and obtains the direction spectrum while minimizing the output.

In both methods, the direction in which the spatial spectrum of the incident angle has the maximum value is estimated as the incident angle. [Equation 5] is an equation representing the spatial spectrum in the delay sum method, and [Equation 6] is an equation representing the spatial spectrum in the Carpon method.

At this time, the following [Equation 5] Conventional beam former (Conventional BF (BeamFormer)) as a spatial spectrum value corresponding to the change of the incident angle θ incident angle estimating means 340 for used in the paper Union method V _BF (θ ) Is estimated as the incident angle of the main path signal. On the other hand, to Equation 6] orientation car phone (Capon) beam if the former incident angle to the spatial spectrum value corresponding to the change in the angle of incidence θ estimating means (340) for use in car phones method a V _CAP (θ) is the maximum value Is estimated as the incidence angle of the main path signal.

Here, a (θ) is a vector representing the array gain of the antenna according to the incident angle θ and has the same dimension (N × 1) as the weight vector W, which can be obtained according to the arrangement of the antenna elements, and the array for the estimated angle of incidence. The gain is the same value as the weight vector W. In addition, the R matrix is input to the antenna means 310 and demodulated signals X ₁ , X ₂ , ..., X _D , ...., X _N , The covariance matrix can be obtained by multiplying the matrix represented by Equation 1 and its transpose matrix, and the components in the main diagonal direction represent the maximum power of signals input to the antenna elements of the antenna means 310.

R = X × X ^T

, X^T는 X의 전치 행렬임.Where X is

, X ^T is the transpose of X.

The incidence angle having the maximum value in the spatial spectrum of the received signal represented by Equations 5 and 6 is estimated as the incidence angle θ of the main path signal. At this time, the process of calculating the spatial spectrum and determining the incident angle at which the calculated spatial spectrum is maximum corresponds to a process of estimating the incident angle of the received signal.

4 is an exemplary diagram for estimating an incident angle of a main path signal received using a spatial spectrum. In this case, the channel characteristics of the applied multipath signal are shown in Table 1 below.

Example of Channel Characteristics for Multipath Signals division Signal size Delay time Azimuth (incident angle) Main route One 0 μs + 5 ° Multipath 1 0.5 1 μs -15 ° Multipath 2 0.4 2 μs + 40 °

The spatial spectrum of the signal received using the multipath channel model of [Table 1] can be obtained using Equations 5 and 6, as shown in FIG. It can be seen that both methods exhibit maximum values at an angle of incidence of + 5 ° of the main path signal.

5 is a detailed flowchart illustrating a beam forming method using an incident angle estimation method according to the present invention. A beam forming method using the incident angle estimation will be described in detail with reference to FIG. 5 as follows.

The signal received by the antenna means 310 is demodulated by the demodulation means 320 into a baseband signal (501). The incidence angle estimating unit 330 obtains a spatial spectrum using the demodulated signal (502), and then estimates the incidence angle at an angle at which the spatial spectrum is maximized (503). When the incident angle is estimated as described above, the weight vector W is obtained by applying the estimated incident angle (504), and the beam forming unit 340 forms the beam by applying the weight vector W to the demodulation signal (505). At this time, a phase value obtained by the incident angle estimation is applied to each of the N demodulated signals, and the phase is converted in the same manner as the phase of the demodulated signal in the phase converter.

The embodiment in the case where the incident angle is estimated to be θ ₁ for the beam forming apparatus according to the present invention is as follows.

In the process of estimating the incidence angle with respect to the main path signal before processing the digital signal for beam formation, if the main path signal is present in the θ ₁ direction among the multipath signals, the incidence angle will be estimated in the θ ₁ direction.

For the estimated incidence angle θ ₁ direction, the array input vector x (k) input to the antenna means 310 with respect to the transmission signal d ₁ (k) is given by Equation 8 below, and (N × 1). Is a vector with dimensions

Here, a (θ ₁ ) is a vector representing the array gain in the θ ₁ direction. As described above, the array gain in the θ ₁ direction estimated by the incident angle is equal to the weight vector W, and the dimension of (N × 1) is obtained. Have In addition, n (k) represents a noise signal and is a vector having a dimension of (N × 1). At this time, by applying the array gain a (θ ₁ ), the signal component in the direction estimated by the incident angle has the effect of increasing the signal strength by the number of antennas.

Meanwhile, the average power E (y (k) y ^* (k)) of the output y (k) of the beam forming unit 340 with respect to the transmission signal d ₁ (k) is obtained as shown in Equation 9 below. Can be.

과

은 각각 안테나로 입사된 신호와 잡음의 전력이다. here,

and

Are the power of the signal and noise incident to the antenna, respectively.

6 is an exemplary view illustrating a beam pattern of a beam former in a DTV receiver to which the present invention is applied.

The incidence angle estimating means 330 estimates the incidence angle of the main path signal of the main path signal after estimating using V _BF (θ) or V _CAP (θ), and the beam forming means 340 is configured for the estimated incidence angle. The beam is formed by applying the weights [w ₁ , w ₂ , w ₃ , ... w _N ] in the incident direction. As shown in FIG. 6, the beam pattern can be obtained in the correct direction without having to form a plurality of beam patterns by estimating the incident angle of the main path signal in the above manner.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

As described above, the present invention has the effect of forming the beam pattern only in the estimated direction without forming a plurality of beams by forming the beam pattern in the estimated direction by estimating the incident angle of the main path signal.

Accordingly, the present invention enables the estimation of the incident angle of the main path signal by using a part of the received signal without the training string information promised between the DTV transmitter and the DTV receiver, thereby receiving digital broadcast in a channel having poor dynamic multipath. This has the effect of improving performance.

Claims (8)

A beam forming apparatus of a receiver of a digital TV having an array antenna and channel equalization means, Incidence angle estimation means for determining an incidence angle at which the spatial spectrum of the multipath signal received and demodulated by the antenna is maximized as an incidence angle of the main path signal; Beam forming means for forming a beam pattern with respect to the determined main path signal incident angle by applying a weight calculated based on the determined angle of incidence to the multipath signal; And Addition means for summing outputs of the beam forming means and outputting the same to the channel equalizing means; Beam forming apparatus comprising a. The method of claim 1, The spatial spectrum is, Given by the following equation Beam forming apparatus, characterized in that.

A (θ) is an array gain determined according to the array antenna array, and R is a matrix defined by X × X ^T as a covariance matrix for X representing the multipath signal. The method of claim 1, The spatial spectrum is, Given by the following equation Beam forming apparatus, characterized in that.

A (θ) is an array gain determined according to the array antenna array, and R is a matrix defined by X × X ^T as a covariance matrix for X representing the multipath signal. The method of claim 2 or 3, The weight is, The array gain for the determined angle of incidence Beam forming apparatus characterized in that. A beam forming method of a receiver of a digital TV having an array antenna and channel equalization means, Demodulating a multipath signal received by the antenna; A second step of determining an incident angle at which a spatial spectrum of the demodulated multipath signal is maximized as an incident angle of a main path signal; A third step of forming a beam pattern with respect to the determined main path signal incidence angle by applying a weight calculated based on the determined incidence angle to the multipath signal; And A fourth step of summing the multipath signals with weights according to the beam pattern formed by the third step and outputting the summed multipath signal to the channel equalization means; Beam forming method comprising a. The method of claim 5, The spatial spectrum is, Given by the following equation Beam forming method characterized in that. A (θ) is an array gain determined according to the array antenna array, and R is a matrix defined by X × X ^T as a covariance matrix for X representing the multipath signal. The method of claim 5, The spatial spectrum is, Given by the following equation Beam forming method characterized in that.

A (θ) is an array gain determined according to the array antenna array, and R is a matrix defined by X × X ^T as a covariance matrix for X representing the multipath signal. The method according to claim 6 or 7, The weight is, The array gain for the determined angle of incidence Beam forming method characterized in that.

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