This book presents the advantages of having Butler Matrices in a receiver system integrated with Low Noise Amplifiers (LNAs). The performances of array antennas with and without LNAs and with and without Butler Matrix are evaluated in terms of measured signal to noise ratio (SNR) at each output port. The SNR values are combined to evaluate the diversity gains available with diversity combining techniques.
By using narrow beams available from the Butler Matrix, it is possible for a receiver to increase the gain in the desired signal directions and reduce the gain in interference directions. Hence, high-gain narrow beam signals for long-range application are produced. A novel technique is introduced which uses high linearity LNAs and a second Butler Matrix, acting as a mirror of the first Butler Matrix, reconstructing the antenna patterns of the individual radiating elements.
The resulting outputs have high linearity and broad beam width that can be used for short-range communications. This book provides a method which could be applicable in vehicle communication systems, where long-range communications with roadside beacons and short-range communications with a fast moving vehicle are both required.