A beamformer with constant-gm vector modulators and its spatial intermodulation distortion

Michiel C.M. Soer, Eric A.M. Klumperink, Dirk-Jan van den Broek, Bram Nauta, Frank E. van Vliet

    Research output: Contribution to journalArticleAcademicpeer-review

    27 Citations (Scopus)
    674 Downloads (Pure)

    Abstract

    Spatial interference rejection in analog adaptive beamforming receivers can improve the distortion performance of the circuits following the beamforming network, but is susceptible to the nonlinearity of the beamforming network itself. This paper presents an analysis of intermodulation product cancellation in analog active phased array receivers and verifies the distortion improvement in a four-element adaptive beamforming receiver for low-power applications in the 1.0-2.5-GHz frequency band. In this architecture, a constant-Gm vector modulator is proposed that produces an accurate equidistance square constellation, leading to a sliced frontend design that is duplicated for each antenna element. By moving the transconductances to RF, a fourfold reduction in power is achieved, while simultaneously providing input impedance matching. The 65-nm implementation consumes between 6.5 and 9 mW per antenna element and shows a +1 to +20 dBm in-band and out-of-beam third-order intercept point due to intermodulation distortion reduction.
    Original languageEnglish
    Pages (from-to)735-746
    Number of pages12
    JournalIEEE journal of solid-state circuits
    Volume52
    Issue number3
    DOIs
    Publication statusPublished - 1 Mar 2017

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