Adaptive Wideband Beamforming Based on Digital Delay Filter

Abstract

A novel adaptive wideband beamforming method is proposed, where beamforming is achieved by LMS based spacetime adaptive filtering algorithm. Conventional broadband beamforming requires desired signal to be incident from the broadside i.e. direction normal to the array. The new method overcome this constraint by make use of digital delay filters which compensate the delay of receiving data, so that the signal of interest can be treated as if it had arrived from the broadside. Then LMS based space-time adaptive filtering algorithm is applied to achieve beamforming. Another advantage of the proposed methodology is its low computational complexity while sustaining high resolution. The effectiveness and advantage of the proposed methodology is theoretically investigated, and computational complexity is also addressed. To verify the theoretical analysis, computer simulations are implemented and comparisons with other algorithms are made.

Fundamentals of Narrowband Array Signal Processing

“…It can be seen that when the step size parameter μ is small, the algorithm converges slowly, while the large value of step size parameter μ make the algorithm converge faster. The least mean square algorithm requires the training sequence, if the training sequence in the LMS algorithm is replaced by the DOA information of the desired signal, the Frost LMS algorithm can be obtained [40].…”

Broadband Frost Adaptive Array Antenna with a Farrow Delay Filter

“…The minimum variance distortionless response (MVDR) beamformer assumes the desired signal induced into the array from the normal direction, so that all the elements receive the same desired signal without any phase difference [2,8]. Therefore, the optimal problem for space-time beamforming is as follows:…”

“…Influence of the Filter Order. At the same simulation condition as the above, we only change the order of the filter and compare the error between the proposed Farrow and direct form structure in [6][7][8]. A comparison of the relative error ε e , defined in (40), for different filter structures is listed in Table 1.…”

“…That means that the desired signal and interference are both suppressed. The other three lines in Figure 7 are the pattern when the delay filter is used through the three methodologies such as time domain [6,8], frequency domain [7], and Farrow. They are very similar because the delay filters play the same functions.…”

“…Both methodologies are online methodologies. Typically, the Frost broadband array delay filter [8] is designed using the timedomain methodology [6]. One downside of using the timedomain methodology is that different delay times result in different filter coefficients, which implies that we have to redesign the filter coefficients if the direction of arrival (DOA) of the desired signal changes because DOA decides the delay time.…”