Badar Muneer*, Zhu Qi and Shanjia Xu A Digital SIW Phase Shifter Implemented by Switching Transverse Slots via PIN Diodes DOI 10.1515/freq-2015-0007 Received January 11, 2015 Abstract: A new idea of Substrate integrated waveguide (SIW) based digital phase shifter by controlling the trans- verse slots etched over the top metallic surface of SIW is proposed. A PIN diode is mounted on each transverse slot. Slots are made “enabled” or “disabled” by switching the state of PIN diode. A detailed explanation and demonstra- tion is presented in this paper. As a result, a digital four bit phase shifter can be realized. Furthermore, equivalent circuit model for proposed device has also been discussed. Insertion loss is as low as 1.5 dB for a wide bandwidth of 31% (6.75–9.25 GHz), with a phase imbalance of Æ 4° and amplitude imbalance of Æ 0.5 dB. Simulation results agree well with the measured results. Keywords: phase shifter, PIN diode, transverse slot, sub- strate integrated waveguide (SIW) 1 Introduction SIW based power dividers and phase shifters are given preference in design of microwave circuits over the other kind of technologies, as there are several advantages associated with SIW based structures, such as, High power handling capability, low insertion loss and high Q factor as well as lower cost of fabrication and compact size are also advantages of SIW based structures, when compared to rectangular waveguide filled with dielectric. Several fixed SIW phase shifters have been developed by the researchers. Fixed phase shifters accomplished by un- equal width SIW are proposed in [1], [2]. Some fixed phase shifters incorporating inductive posts into SIW have been developed in [3], [4], a relatively recent pub- lication reports fixed phase shift achieved by introducing double-stub [5]. However, SIW phase shifter with the ability of electronic control are in demand. SIW based analogue phase shifters that employ var- actor diodes are proposed in [6]–[11]. But the phase and amplitude imbalance of these designs limit their use in application where high accuracy is desirable. Also the bandwidth performance of previous designs of controlla- ble SIW phase shifters is not satisfactory for many application. In this paper a new idea of an electronically control- lable SIW digital phase shifter that provides phase shift for an acceptable insertion loss and relatively wider bandwidth. This phase shifting device is composed of a small section of SIW with the transverse slots on the top surface. The position of slots in longitudinal direction is controlled electronically by using PIN diodes. PIN diodes are used to electrically short circuit the two long edges of slot to make it virtually disappear. Turning the slots “ON” and “OFF” in a certain configuration, a phase shift at output port can be seen. Using this phenomenon, a phase shifter is realized and demonstrated in this paper. 2 Structure of the phase shifter Proposed phase shifter is a section of substrate integrated waveguide with a certain number of slots present on the top surface. Each slot is loaded with a PIN diode that is used to either make the slot visible at the output port (in reverse biased state) or to make it virtually invisible to the output port (in forward biased state). Figure 1 shows the schematic of a simple SIW based such phase shifter with four transverse slots. An efficient way of mounting PIN diode on slot is presented in [6], but it introduces further layers to the structure, this makes the structure bulky. Another method of using chip capacitor to isolate the PIN diode from the top metallization has also been explained in [7], this a good solution but makes the fabrication process tedious. The biasing scheme used in this work is unique in the way that it not only keeps the design low profile, but also makes it much easier to provide biasing signal by avoiding additional bias Tee network. Due to the perfect electric boundary condition present at the top *Corresponding author: Badar Muneer, Department of Electronics Engineering and Information Science, University of Science and Technology of China (USTC), Hefei 230017, P.R. China, E-mail: badar@mail.ustc.edu.cn http://orcid.org/0000-0002-5090-9744 Zhu Qi, Shanjia Xu, Department of Electronics Engineering and Information Science, University of Science and Technology of China (USTC), Hefei 230017, P.R. China Frequenz 2015; 69(9-10): 383–387 Unauthenticated Download Date | 6/18/16 11:02 PM