Yikun Huang

Analysis for Capon and MUSIC DOA estimation algorithms

This paper derived the large-sample MSE of the DOA estimates obtained by Capon and MUSIC methods in the narrowband array processing case. The Monte Carlo simulations have been carried out for two independent non-coherent sources. MSE variation is studied with respect to the mismatch in array calibration and the number of array elements. The simulation results show that bother methods are sensitive to the phase mismatch. Capon is bias estimator for small number of array element. However when the array element number is large, those two methods come to similar result.

A blind iterative calibration method for high resolution DOA estimation

A novel online antenna array calibration method is presented in this paper. Unlike conventional calibration process, the proposed method is a blind approach that does not require prior knowledge of angles used for calibration and the method can be modified for real time calibration processing. An iterative process is used to converge to the actual bearings while the measured steering vector is estimated via Eigenvalue decomposition. The correction matrix is then estimated by use of the least squares estimator. The last step consists of pre-multiplying the measured data set by the obtained correction matrix which mitigates magnitude, phase, and mutual coupling effects on the acquired data set. The experimental study has been carried out on an 8-element uniform circular array (UCA) with an 8-channel RF receiver board at 5.8GHz. The performance of Bartlett, MUSIC, Beamspace MUSIC, and S2-MUSIC direction of arrival (DOA) estimation algorithms have been examined on CW and Harris SeaLancet RT1944/U radio signals. The lab test results have shown significant improvements on high resolution DOA estimation in terms of accuracy and resolution. The proposed method can be implemented in a direction finding system and can be run periodically to mitigate any changes in the environment and maintain high resolution performance over time. Potential applications of the calibration method include improvement of accurate passive RF signal source localization, high QoS wireless communications with beamforming antennas and sensor networking.

Spatial selective MUSIC for direction of arrival estimation with uniform circular array

This paper proposes a novel DOA method based on spatial selectivity that uses the robustness of the cophasal algorithm and the accuracy of MUSIC while greatly reducing the complexity and the speed of the system. This novel algorithm was used for uniform circular array (UCA). The method consists of two computation steps, namely, rough and smooth search. In the rough search step standard switched beam is used for spatial selective beamforming. In the smooth search, optimal element reduction is applied for DOA estimation of the target by modifying the classical MUSIC algorithm.

FPGA implementation of a Bartlett direction of arrival algorithm for a 5.8ghz circular antenna array

This paper presents the design and prototyping of a Bartlett direction of arrival algorithm for an adaptive array antenna system using a Xilinx Virtex-5 FX70 FPGA. The algorithm was prototyped in both full custom VHDL hardware and in a Xilinx MicroBlaze soft processor to analyze the performance tradeoffs between hardware and software implementations. The design was tested using an 8-element circular antenna testbed. The implementation and analysis presented in this work will aid system designers to understand the tradeoffs between implementing algorithms in custom hardware versus in an embedded system and when a hybrid approach is more advantageous. 1 2

A Compact Smart Antenna for WiMAX Radio

In this paper, we present our design and development of a compact, light weight, high gain smart antenna for WiMAX radio systems. The antenna head is an 8-monopole uniform circular array placed on a ground plane with ground skirt. The operation frequency is 5.8GHz. The array is connected to an 8-channel beamforming board via low-loss coax. The 8-channel signal combines through a power splitter/combiner which directs the signal to/from the WiMAX radio. An FPGA chip is on board to control the digital phase shifters, attenuators and switches for T/R synchronization, signal searching, beamforming, and tracking. The test results show that the smart antenna is capable of tracking mobile targets, communicating directionally with desired users, suppressing interference and jamming, and enabling a long range with high throughput and reliable connection.

An Adaptive Smart Antenna Testbed for WiMAX Radio

In a world where ubiquitous connectivity became more of a necessity then luxury sparsely populated and rural areas remain the least connected areas around the globe. Considering conventional wired or wireless infrastructure will cost billions to implement and maintain. A very attractive solution that has proven improved performance in terms of signal quality, coverage area and connection speed consists of using an adaptive smart antenna system in conjunction with IEEE 802.16 WiMAX [1]. This paper presents the design and development of a testbed to analyze the feasibility of utilizing such novel solution. Though supported by the WiMAX standard, a smart antenna system utilizing this radio technology has not been implemented yet. This design serves as a common flexible platform for testing the system as a whole and in part. The different system’s modules, namely, the Direction Of Arrival (DOA) estimation module, the beamforming module and the computer interface have been tested and showed promising results.

Performance analysis of a null steering algorithm

In this paper we have analyzed the performance of a general null steering algorithm by simulation studies for the expected OISR and standard deviation of OISR for different signal to noise level and different number of samples. We have also studied a special case of the general approach and compared the expected value of OISR using the definition and the approximate expression of the expected value of OISR The results show that the approximation E{OSIR} (eq.8) is not accurate enough even in the case where higher SNR, large T, and distanced sources were used. These results are useful for predicting the asymptotic performance of an open-loop adaptive null steering system under different signal to noise level and different number of snapshots.

A wideband circular array for frequency and 2D angle estimation

This paper presents a novel method for joint frequency and 2D angle estimation of incoming signals upon a circular array over a very wide frequency band (2–18 GHz). 1,2A temporal domain ESPRIT frequency estimation algorithm was extended for azimuth and elevation angles estimation. These direction estimation results are automatically paired with frequency. The algorithm provides non-ambiguous, high resolution and accuracy in both frequency and direction of arrival estimation over the frequency range. The DOA estimation resolution was analyzed for two signals with different frequency. The estimation accuracy vs. signal to noise ratio (SNR) and array element number were studied. The frequency estimation accuracy was compared with the standard FFT method. The DOA estimation accuracy and resolution were compared with the original MUltiple SIgnal Classification (MUSIC) DOA estimation results. The proposed technique can be used for wireless communication applications and wireless sensor networks and it can also be used for RF emitter detection and tracking. The system is consistent with the Air Forces layered sensing architecture concept.

Cognitive beamforming antenna

This paper presents our design of a cognitive beamforming antenna that is capable of reconfiguring its spatial and spectral receiving and transmitting properties in response to the dynamic situations encountered. We accomplish this through joint frequency and spatial scans to establish both spectral and spatial knowledge of the local RF environment. With this information we are able to establish the optimal frequencies and beam patterns to exploit the current environmental situation, including adding beam pattern nulls if required. This design is an effective solution in the common situation where strong interferences and spectral congestion are present that could impact system performance.1,2

A compact beamspace DOA estimation and beamforming communication device

This paper describes our design of a compact and efficient beamspace direction of arrival (DOA) estimation and beamspace beamforming device. The robust functionality includes high resolution RF emitter DOA estimation and beamforming in a noisy environment with strong interference. Simulations for beamspace DOA estimation using beamspace MUSIC and beamspace Capon methods are presented in conjunction with beamspace Capon beamforming. The DOA estimation accuracy, resolution, and beamforming output signal quality have been carefully studied and quantified. The algorithms have been implemented to utilize an 8 element uniform circular array (UCA) and an 8 channel analog beamformer (BF) operating at 5.8 GHz. The simulations and initial experimental results show that the proposed system can achieve good accuracy once it is properly synchronized. In addition, a significant decrease in hardware is realized when operating in beamspace versus element space. 1 2