A Full-Duplex Quadrature Balanced RF Front End with Digital Pre-PA Self-Interference Cancellation

Nimrod Ginzberg, Dror Regev, Genadiy Tsodik, Shimi Shilo, Doron Ezri, Emanuel Cohen

Research output: Contribution to journalArticlepeer-review


This article presents a quadrature balanced radio-frequency (RF) front-end transmitter (TX) architecture assisted by a digital self-interference cancellation (SIC) algorithm for simultaneous transmission and reception in next-generation full-duplex radios. The proposed quadrature balanced power amplifier (QBPA) topology is a four-port circuit with an embedded passive primary isolation (PI) between the antenna and the receiver (RX) low-noise amplifier (LNA), along with a very low power SIC injection mechanism that reuses the TX's gain. A transmit-receive (TR) isolation of >57 dB is measured for continuous-wave (CW) signals over an 80 MHz bandwidth (BW). A TR isolation of >50 and >56 dB is demonstrated for an 80 MHz 802.11ac orthogonal frequency-division multiplexing (OFDM) signal at 10-and 20 dB backoff from 30 dBm peak TX power (PTX,max), respectively, within the 2.4 GHz Wi-Fi band. A digital predistortion algorithm is applied to linearize the TX at the high output power case, achieving error vector magnitude (EVM) lower than-34.7 dB for concurrent TX-SIC operation. A simultaneous TR scenario is demonstrated, measuring an RX signal EVM of-22 dB, while PTX,max = 30 dBm. Measured RX loss is lower than 1.8 dB within the operating frequency band.

Original languageEnglish
Article number8897729
Pages (from-to)5257-5267
Number of pages11
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number12
StatePublished - Dec 2019


  • Channel estimation
  • Wi-Fi
  • digital predistortion (DPD)
  • full duplex (FD)
  • quadrature balanced power amplifiers (QBPAs)
  • self-interference cancellation (SIC)
  • simultaneous transmit-receive (TR)

All Science Journal Classification (ASJC) codes

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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