• P-ISSN 0974-6846 E-ISSN 0974-5645

Indian Journal of Science and Technology


Indian Journal of Science and Technology

Year: 2019, Volume: 12, Issue: 28, Pages: 1-7

Original Article

QPSK Demodulator based on a New Half Mode Substrate Integrated Waveguide Six-port Junction


Objectives: This study presents a novel architecture of a six-port demodulator operating at 2.45 GHz. The new structure of the six-port junction was based on a branch-line coupler and made up of a Wilkinson power divider and three 90°-hybrid coupler. Methods: The six-port design was accomplished using HMSIW technology. Simulation was carried out using ADS software of Agilent technologies and HFSS software. Then, an RF-DC conversion circuit was optimized and designed. Our choice fell on a Schottky diode-based power detector and a resistive adaptation to its input. Subsequently, to validate this system we have assembled these two circuits using a co-simulation Harmonic Balance-momentum. Then the six-port configuration was connected to power detectors to show its performance as a demodulator circuit. Finally, the use of an appropriate algorithm on MATLAB allowed us to extract the amplitudes of the four output signals as a function of the phase difference between the two input signals. Findings: The obtained results showed that the six-port junction has good performances in terms of phase difference, return loss, reflection and isolation. We conclude that the six-port junction, designed as a phase discriminator, has the best qualities for demodulating an RF signal. Application: For each output voltage we have a phase shift for which the corresponding power is canceled so the power detector allows, by measuring the output powers and by detecting the one that is minimal compared to the others, to differentiate the four states of modulation which highlights the good behavior of our system.

Keywords: Six-port junction, HMSIW, Power detector, Linearization, QPSK demodulation


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