Tuan Do-Hong

A method for wideband direction-of-arrival estimation using frequency-domain frequency-invariant beamformers

In this paper, we propose a new wideband direction-of-arrival (DOA) estimation method for wideband smart antennas based on Frequency-Domain Frequency-Invariant Beamformers (FDFIB). By appropriately designing the weights for frequency-domain beamformers at different frequencies, the frequency-invariant beam-patterns are obtained. Then beamformers play a role as (wideband) spatial processor transforming signals from element-space to beam-space. After that, the narrowband DOA methods can be applied in beam-space to estimate DOAs. The method is able to operate with arbitrary antenna army and arbitrary wide bandwidth without preliminary DOA estimate. In addition, the proposed method provides low computational time and simple implementation. The performance of proposed method in comparison with conventional wideband methods is illustrated in simulation results.

Wideband direction-of-arrival estimation using frequency-domain frequency-invariant beamformers: an analysis of performance

This paper presents an extension of the wideband direction-of-arrival estimation method using frequency-domain frequency-invariant beamformers (Do-Hong et al., 2003) with an analysis of performance. An asymptotic expression for the root-mean-square error and a resolution threshold of signal-to-noise-ratio for resolving directions of sources are shown. A comparison of analysis and simulation as well as numerical results are also presented.

A new design method for digital beamforming using spatial interpolation

The paper presents a new method for designing a digital beamformer using a uniform linear (or planar) array. By employing a spatial interpolation process at the digital signal processing section, the number of antenna elements, and the corresponding RF modules, analog/digital (A/D) converters, etc., are significantly reduced, while still retaining the same main beamwidth and the same sidelobe level (SLL) as the traditional beamforming method that requires a larger number of elements. In addition, the method provides for prescribing a narrow main beamwidth specification, while at the same time allowing for a prescribed low SLL specification. Illustrative design examples and a comparison with the traditional beamforming method are included.

An analysis of wideband direction-of-arrival estimation for closely-spaced sources in the presence of array model errors

This letter presents an analysis of wideband direction-of-arrival (DOA) estimation for closely-spaced sources using arbitrary antenna array taking into account the effect of array model error, which is important issue in practical implementation. Based on this analysis, a new wideband DOA estimation method without array calibration is then developed to deal with the effects of array errors. The performance improvement of the proposed method in the presence of array errors is shown in simulation results.

Wideband direction-of-arrival estimation and beamforming for smart antennas system

This paper summarizes the smart antennas approaches and presents the methods for wideband direction-of-arrival (DOA) estimation and wideband beamforming. For wideband DOA estimation, we focus on spectral-based methods using arbitrary antenna array. For wideband beamforming, time-domain processing and frequency-domain processing methods, which produce frequency-invariant beam response over wide signal bandwidth, are introduced. The method for design of wideband beamforming using spatial interpolation, which can reduce number of array elements and prescribe beampatterns, will be also presented.

Wideband direction-of-arrival estimation using spatially interpolated wideband beamformers

We present a new method for wideband direction-of-arrival (DOA) estimation, based on a spatially interpolated wideband beamformer (SIWB). The SIWB is designed to have a frequency-invariant beam-response, prescribed main beamwidth and prescribed sidelobe level within a wide signal bandwidth. For wideband DOA estimation, the SIWBs can be used as spatial preprocessors transforming the wideband signals at the outputs of an antenna array (element-space) into the beam-space signals prior to applying narrowband DOA estimation. The new SIWB-based method enhances the resolution of spectral estimation and reduces the root-mean-square error of DOA estimation without increasing the number of array elements. Furthermore, the proposed method is applicable for DOA estimation of coherent sources without preliminary DOA estimates. The performance of the proposed method in comparison with conventional methods is illustrated in simulation results.

Direction finding using spectral estimation with arbitrary antenna arrays

This paper presents direction-finding techniques for smart antennas based on conformal and irregular antenna arrays. Methods of spectral estimation are considered to estimate directions-of-arrival (azimuth and elevation) using two-dimensional arrays and three-dimensional arrays (conformal arrays). The effects of arbitrary arrays on the performance and on the resolution of direction-finding algorithms are illustrated by simulation results.

Front-End Processing with Lens Antenna Arrays for Direction-of-Arrival Estimation

Spectral estimation and direction-of-arrival (DOA) estimation is considered for discrete lens antenna array front ends. In this approach, when using the Multiple Signal Classification (MUSIC) algorithm, the dimension is reduced by the front end which performs spatial processing, resulting in increased computational speed and decreased computational load. As a specific example, simulations of a 33-element lens array with DOA estimation for 7 simultaneous sources shows that the computational load is reduced to 68% of that for a 33-element linear uniform array. In this paper, we consider the case of narrowband uncorrelated signals, and uniform spacing of receivers on the lens image surface, but the analysis can be extended to broadband non-uniform scenarios.

Smart antenna technology for high-altitude-platform based wireless communication systems

We present a digital beamforming scheme for future wireless communication systems based on high altitude platforms. The proposed digital beamforming scheme, which is installed on the platforms in high-altitude-platform (HAP) systems, can reduce significantly the number of antenna elements and the corresponding receiver modules, analog to digital (A/D) converters etc. without loss of performance. As a result, the system complexity and system costs can be reduced, therefore, enhancing feasibility of HAP based systems. Furthermore, in the proposed scheme, we can specify narrow main beamwidth and low sidelobe level simultaneously. Illustrative design examples and beam-pattern comparisons with traditional digital beamforming methods are included.

A new digital beamforming scheme for high-altitude-platform based communication systems

In this paper we present a digital beamforming scheme for wireless communication systems based on high altitude platforms. The proposed digital beamforming scheme, which is installed on the platforms in high-altitude-platform (HAP) systems, can reduce significantly the number of antenna elements and the corresponding receiver modules, analog to digital (A/D) converters etc. without loss of performance. As a result, the system complexity and the system costs can be reduced, therefore enhancing feasibility of HAP-based systems. Moreover, in the proposed scheme, it allows to specify narrow main beam width and low sidelobe level simultaneously. An illustrative example, which demonstrates the design of the new method, is included