United States of America As Represented by the Secretary of the Air Force

David C Tsui

James B Tsui

James N Hedge

A solution to the AOA problem is provided, receiving the data via a plurality of antennas, which uses a switching network to couple the antennas to a single receiver and a single analog-to-digital converter to digitize the incoming signal. It is possible to solve the problem where there might be multiple signals present. In the receiver, the incident radiation is mixed with a local oscillator signal and down converted to an intermediate frequency (IF). This IF signal is discretely sampled in the analog-to-digital converter, and further processing is done using digital techniques. The incoming signal has to be phase compared to obtain the angle of arrival. Different delay times are used to receive the digital data from the different antennas at the same sampling times, with the data aligned according to the time axis. The frequency of the incoming signals can then be detected by performing a Fast Fourier Transform (FFT) on the data from one antenna with respect to time. Once the primary frequencies are determined, one can find the related amplitudes of the data from the other antennas. An FFT can then be performed on the amplitude values found. The output of this FFT gives the phase information related to the incoming signals and thus the solution to the AOA problem.

Angle of arrival (AOA) solution using a single receiver

The technique to measure the frequency very accurately for electronic warfare (EW) applications, and is simple in hardware, and which can accomplish this goal with a signal with real data (in contrast to complex data). It uses trigonometric identities to compute the location of the zero, which is very precise, but requires the use of an inverse trigonometric function. From these crossings, one can find the frequency very accurately using only one channel of data. The input signal is down converted and digitized with one A/D converter. The digitized data is used to find the zero crossing. The resolution of the zero crossing is limited by the clock cycle. Three uniformly digitized points around a zero crossing are used to find the time for the crossing. The device according to the invention will calculate the frequency very accurately using only one channel of data. This method can be used to measure the angle of arrival in a two antenna configuration with very precise results where the distance between the two antennas does not exceed half the wavelength of the incoming signal.

Highly accurate zero crossings for frequency determination

The technique to measure the frequency very accurately for electronic warfare (EW) applications, and is simple in hardware, and which can accomplish this goal with a signal with real data (in contrast to complex data). It uses a linear approximation between points to calculate zero crossings of an incoming signal. From these crossings, one can find the frequency very accurately using only one channel of data. The input signal is down converted and digitized with one A/D converter. The digitized data is used to find the zero crossing. The resolution of the zero crossing is limited by the clock cycle. Two uniformly digitized points around a zero crossing are used to find the time for the crossing. The device according to the invention will calculate the frequency very accurately using only one channel of data. This method can be used to measure the angle of arrival in a two antenna configuration with very precise results where the distance between the two antennas does not exceed half the wavelength of the incoming signal.

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Centerville, OH, United States of America

David C Tsui