In this work a compact planar butler matrix is presented by removing the 0 dB crossover. The proposed butler matrix consists of 45°and 90°phase shifter, and four branch line coupler miniaturised by employing open stubs in each transmission line. As the crossover is removed from the circuit, the circuit size is reduced and the performance is enhanced compared to the conventional Butler matrix. The response obtained from the newly designed butler matrix is comparable to the conventional butler matrix which is operated at 2.5 GHz. The size occupied by the proposed butler matrix is 2.01k g 9 1.13k g . A phase difference of ±45°and ±135°is obtained between the output ports with a maximum of differential phase tolerance of 3°and S-parameter magnitude with a leeway of ±1.5 dB from the theoretical results. As the phase tolerance is within the acceptable limit of bandwidth region, so the interference in beams is found negligible. The measured result and simulated result is in accord. The planar circuit of very low cost with good performance can be used to provide feed to an antenna array system.
A compact, low‐cost Wilkinson power divider (WPD) of 1.3 GHz (f0) operating frequency, with a low‐pass filtering response, is presented in this study. Power division and low‐pass filtering responses are both achieved by using two symmetrical units of interdigital line resonators (ILRs). Each square unit of ILR exhibits a low‐pass filtering response, with a minimum insertion loss of 0.3 dB. The dumbbell‐shaped, defected ground structures are introduced for widening the attenuation band by suppressing the harmonics up to 14 GHz (up to 10.76 f0) and also for miniaturising the circuit. An isolation resistor of 100 Ω is placed between two output ports of the WPD for obtaining good isolation. The operating frequency of the low‐pass filter is 2 GHz with an attenuation of −17 dB up to 20 GHz. The proposed structure is fabricated using low‐cost substrate material FR4. Both the low‐pass filter and the power divider are fabricated and measured. The electromagnetic‐simulated and measurement results are experimentally verified.
A new defected ground structure (DGS) consisting of two square ring slots connects with a rectangular ring slot by two thin transverse slots under a microstrip line is proposed. In the frequency characteristics of proposed unit pattern, an attenuation zero is observed close to the attenuation pole. As a result, better transition sharpness, lower passband insertion loss and broader stopband are observed compares to dumbbell DGS. An equivalent lumped L-C network is proposed to model the introduced DGS unit and corresponding L-C parameters are extracted. Insertion loss is reduced by alternative transmission line on the top plane of the DGS unit.
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