Raymond J. Weber

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.

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.

Increasing Radiation Tolerance of Field-Programmable- Gate-Array-Based Computers Through Redundancy and Environmental Awareness

Radiation-tolerant computing is of great importance to the aerospace community because future missions demand more computational power. Of special interest to the aerospace community are flight computers implemented on static random-access-memory-based field-programmable gate arrays. Such computer systems allow the in-flight reconfiguration of hardware that enables the practical deployment of truly reconfigurable computers. However, commercial static random-access-memory-based field-programmable gate arrays are uniquely susceptible to ionizing radiation. This paper introduces a computer architecture for static random-access-memory-based field-programmable gate arrays that resists failures caused by ionizing radiation. The approach extends the widely accepted fault mitigation practice of triple modular redundancy and configuration memory scrubbing by adding spare circuitry and environmental awareness through an ionizing radiation sensor. This paper describes the design of the system in addition to a theore...

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 cognitive beamforming array

This paper presents our design of a cognitive beamforming array that can be used for communications and RF mapping. This novel approach is through joint frequency and spatial scan to establish both spatial and spectral knowledge of the local 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 is present and could affect system performance. Our cognitive beamforming array is able to then maintain communications while simultaneously tracking user locations and updating its knowledge of the spectral situation. The response of this system to different scenarios was explored through the use of Matlab simulations prior to hardware implementation of the system. This array system will also help to open up new opportunities for national security and defense, economic development and address pressing social needs in underserved areas in addition to advances in related areas, such as RF localization techniques.

3D RF emitter location estimation

This paper describes a novel approach of a robust and efficient 3D location estimation technique for non-cooperative, active or passive RF emitters in a noisy environment with two or more arbitrary shaped arrays. Each array can provide precise frequency, direction of arrival (DOA) estimation and time of - arrival (TOA) estimation for the far field RF emitters. For an M-element array, the DOA estimator can adaptively estimate and track up to 2/3M independent emitters. We then apply the TDOA estimation and adaptive tracking algorithms to adaptive position finding and tracking involving one or two plane waves impinging on two synchronized uniform circular arrays, in the presence of uncorrelated receiver noise. Matlab simulations for mobile RF emitters location estimation are presented and discussed. The algorithms have been implemented to utilize an 8 - element uniform circular array that operates at 5.8GHz. Two identical arrays have been used for locating and tracking two fixed or/and mobile RF emitters‥ Test results show that the proposed system can achieve accuracy within 6 meters and resolution about 25 meters with the 8 - element circular array at a distance of 10 km. 1,2

A joint frequency and DOA estimation algorithm with diagonal load

We have developed 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]. This paper presents the algorithm with diagonal load for robust performance with improved accuracy and resolution. A 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 was 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)[2] 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.12

An automatic calibration system for smart antenna arrays

Experimental results have showed that beam patterns can achieve their theoretically expected performances only if the non-ideal array behavior is appropriately compensated. We have developed an automatic calibration system for smart antenna array. It is time saving, easy to operate and accurate. The test results show that the calibrated array has a much improved beam pattern comparing with the one without calibration and it is very close to the simulated pattern.

Experimental Conformation of Ionizing Sensing for Space Radiation Environmental Awareness

A prototype system has demonstrated the capability to use a custom-designed multi-channel sensor to monitor high energy radiation strikes by coupling the silicon sensing elements with a radiation tolerant computer system. The computer system uses triple modular redundant soft processors and custom signal conditioning circuitry to monitor single event effects caused by high energy particles passing through semiconductor materials. The operation of the system was confirmed by exciting the radiation sensing elements with high energy Krypton ions from a cyclotron and monitoring the number of current spikes generated by the generation of electron-hole pairs as the ions lose kinetic energy through collisions within the silicon lattice of the sensors.