Abstract
Time-Modulated Linear Arrays (TMLAs) offer useful efficiency savings over conventional phased arrays when applied in parameter estimation applications. The present paper considers the application of TMLAs to acoustic systems and proposes an algorithm for efficiently deriving the arrival angle of a signal. The proposed technique is applied in the frequency domain, where the signal and harmonic content is captured. Using a weighted average method on harmonic amplitudes and their respective main beam angles, it is possible to determine an estimate for the signal’s direction of arrival. The method is demonstrated and evaluated using results from both numerical and practical implementations and performance data is provided. The use of Micro-Electromechanical Systems (MEMS) sensors allows time-modulation techniques to be applied at ultrasonic frequencies. Theoretical predictions for an array of five isotropic elements with half-wavelength spacing and 1000 data samples suggest an accuracy of within an angular range of approximately . In experiments of a 40 kHz five-element microphone array, a Direction of Arrival (DoA) estimation within of the target signal is readily achieved inside a range using a single switched input stage and a simple hardware setup.
Highlights
There are numerous situations where the range and origin of a transmitting source need to be determined
The present paper considers electrically scanned systems operating in the receive mode only which utilise Time-modulated Linear Arrays (TMLAs)
The Field-Programmable Gate Array (FPGA) on the myRIO was setup to produce a digital waveform to control a set of complementary metal-oxide-semiconductor (CMOS) analogue switches that select between the individual microphone elements
Summary
There are numerous situations where the range and origin of a transmitting source need to be determined. Some of the most common methods that achieve this use a receiver that electronically or physically scans space to find the Direction of Arrival (DoA). Electronic systems usually incorporate an array of sensors [1,2,3]. Parameters by Rotational Invariance Techniques" (ESPRIT) [5] algorithms. These algorithms make use of sub-space methods which involve a significant amount of computation to produce an accurate direction estimation for an incoming signal; the data of each element in the array usually needs to be recorded concurrently. The normalized array factor of an N element, TMLA when receiving a signal from direction θ can be written as [16] N AF (θ, t) = N −1 ∑.
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