Highly Reconfigurable Quadrature Coupler With Ideal Impedance Matching and Port Isolation

Pei-Ling Chi, Ting Chen Hsu

Research output: Contribution to journalArticle

19 Scopus citations


This paper proposes a varactor-based coupler structure that allows for reconfigurable operating frequency, power-dividing ratio, and coupler to/from crossover responses. Particularly, this coupler can theoretically realize perfect impedance matching and port isolation at all tuning states. The coupler analysis, design equations, and design graphs were conducted, given, and discussed in detail. For demonstration purposes, two prototypes were experimentally developed and characterized. The first quadrature coupler demonstrates a frequency-tuning range from 0.632 to 1.5 GHz with a constant power-dividing ratio of -3 dB, <2.3° phase imbalance, >20-dB isolation, and >14-dB return loss. In the second prototype, for the phase error <6.7°, isolation and return loss >19 dB, the power-dividing ratio was tuned from -6.4 to 20.5 dB at 1 GHz, yielding a 26.9-dB tuning range and crossover characteristics at low bias voltages. Measured and simulated results are in good agreement.

Original languageEnglish
Article number7873312
Pages (from-to)2930-2941
Number of pages12
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number8
StatePublished - 1 Aug 2017


  • Crossover
  • quadrature coupler
  • reconfigurable
  • varactor

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