A Modified 4×4 Butler Matrix Based Switched Beamforming Network with Five Beams

In this work 4x4 Butler matrix with 1×4 microstrip patch antenna array has been proposed to form a switched beamforming network operating at 3 GHz. This beamformer generates 4 orthogonal beams. 4x4 Butler matrix comprises 4 directional couplers, two phase shifters and two crossovers. The directional couplers have been used to divide the power equally with 90 ̊ phase shift, the phase shifters performs the phase delay in the design and the crossover works for isolation. All simulation results of these components matched the theory. Linear 1×4 microstrip patch antenna array elements have been matched using inset feed technique. These elements had a good performance at the design frequency. The CST MICROWAVE STUDIO SUIT was used for simulations. The total size of the Butler matrix is 104 mm×100mm. The return loss obtained was less than –15 dB and the output power distribution was in the range of -6 to -8 dB at the 3GHz design frequency. The four beams have been obtained in the directions -14°, -42°, 42° and 14° with a narrow beamwidth and with a gain of 11.4 dB, 11.2 dB, 11.2dB, and 11.4dB respectively A modified Butler matrix also has been proposed to generate a fifth beam at together with the original four beams obtained in the conventional design. The modification increased the scan capability Keywords: 4x4 Butler matrix, beamforming, linear array, radiation pattern.