Balanced MMIC QPSK modulator with low amplitude and phase errors

Balanced MMIC QPSK modulator with low amplitude and phase errors

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A broadband monolithic microwave integrated circuit (MMIC) quadrature phase shift keying (QPSK) modulator with low amplitude and phase errors is proposed. The presented modulator adopts two wideband reflection-type binary BPSK modulators, each consisting of a modified Lange coupler with additional λ/4 transmission lines, varactor diodes, inductors and resistors. The proposed QPSK modulator is implemented in 0.15 μm GaAs low-noise pHEMT process. The measurements show an error vector magnitude and a demodulated I/Q offset <5.8% root-mean-square and −16.1 dB, respectively, from 18 to 26.5 GHz.


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      • 5. Sun, Y., Freundorfer, A.P., Sawatzky, D.: ‘A QPSK direct digital modulator in GaAs HBT at 28 GHz’. CCECE, Saskatoon, Canada, May 2005.

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