2016 24 th Iranian Conference on Electrical Engineering (ICEE) 978-1-4673-8789-7/16/$31.00 ©2016 IEEE Novel Compact Wideband Differential Reflective Phase Shifters With Wide Range of Phase Application Somayeh Khajepour, Department of Electrical Engineering, University of Shahid Beheshti, Tehran 15914, Iran Email: so.khajepour@mail.sbu.ac.ir. Shahrooz Asadi, Department of Electrical Engineering, University of Shahid Beheshti, Tehran 15914, Iran Email: sh_asadi@sbu.ac.ir. Mohammad Saeid Ghaffarian, Department of Electrical Engineering, Amirkabir University of Technology, Tehran 15914, Iran Email: msghaffarian@aut.ac.ir, Gholamreza Moradi, Department of Electrical Engineering, Amirkabir University of Technology, Tehran 15914, Iran Email: ghmoradi@aut.ac.ir. Abstract—This paper presents wideband compact differential reflective phase shifters based on the double layer slot-coupled coupler configuration. These novel phase shifters arrangement consists of a 3-dB hybrid coupler with the coupled and transmission ports terminated with elliptically shaped microstrip loads. By altering the ports termination of the coupler, phase shifters propose differential phase ranging from -90° to +90° over 1.2-6 GHz (137%) frequency band. To achieve different range of phase performance, the proper reactance is calculated at the outputs of coupler. These reactances are transformed to the elliptical- shaped microstrip load with various dimensions for every phase shifter. The calculation and simulations results show that the developed circuits provide ±30°, ±45°, ±60° and ±90° differential phase shifts with deviation less than 2.1°. The achieved return loss is better than 10dB as well as insertion loss is less than 1dB. The simulated phase shifters including reference line occupy maximum an area of 25 mm × 50 mm (0.14 λ × 0.28 λ ). Simulated results demonstrate that the proposed phase shifters are well suited for use in GPS/DCS/PCS/UMTS/WiBro/ Bluetooth/S-DMB/ WiMax/WLAN frequency bands. Keywords-reflective phase shifter; slot-coupled coupler; wideband; differential phase shift. I. INTRODUCTION Differential phase shifters are widely used components in many microwave instrumentation and systems such as phased array antennas, measurement systems, balanced amplifiers, mixers and monopulse networks. These four-port passive microwave devices provide a constant phase difference between the signals at their output ports over the band of interest. The most famous differential phase shifter is the Schiffman phase shifter which based on the edge-coupled stripline transmission configuration [1]. This structure consists of reference line and two edge coupled striplines which were integrated together at their bottom. By choosing the proper length of these lines and the degree of coupling, the phase difference between them can be made constant phase shift over one octave frequency band. However, a very narrow gap between the edge-coupled lines is needed for a broadband performance and when this circuit is fabricated in microstrip technology, its operation decreased [2]. The other techniques to build planar wideband couplers and phase shifters are including modified Schiffman [2]-[4], slot-coupled structures, [5]-[7], substrate integrated waveguides [8], loaded trans-mission lines [9] and etc. Slot-coupling approach involving a double-sided substrate, was first proposed by Tanaka [13]. The structure is formed by two microstrip lines separated by a rectangular slot in the common ground plane. In [14], Abbosh proposed a microstrip-slot-microstrip coupler with an elliptical-shaped broadside coupled structure that indicates good properties in UWB. This approach allowed to design compact UWB phase shifters with the phase difference no larger than 48° [5]. Then Sorn [6] developed Abbosh phase shifter to 90° phase shift by terminating two output ports of the coupler with capacitive load providing 3-7 GHz operating bandwidth. Finally, Guo by terminating Abbosh coupler outputs with open-ended and short- ended stubs, proposed UWB phase shifters in the range from - 180° to +180° with 7° phase deviation [7]. As a result, slot- coupled structures are a good candidate for wideband applications because of tight coupling, low phase deviation and size reduction. It seems very interesting to design coupler and phase shifter in specified 1-6 GHz frequency band that covers GPS/DCS/PCS/UMTS/WiBro/Bluetooth/S-DMB/WiMax/W- LAN which use in satellite communication, mobile communications and etc. As a literature review, the phase shifters are designed in the mentioned frequency band is investigated. In [4], a Schiffman phase shifter improved by modifying the ground plane underneath the coupled lines is proposed. Its amplitude and phase imbalance are 0.5 dB and 5° over 1.5-3.1 GHz. A 90° phase shifter, which comprises a stepped impedance open stub and a coupled line with 1.1 dB amplitude imbalance and 5° phase deviation over 0.75–2.4 GHz is presented in [8]. Also in [10], the proposed 90° phase shifter is based on the loaded