A Compact QPSK Modulator with Low Amplitude and Phase Imbalance for Remote Sensing Applications

Farhan Abdul Ghaffar, Tareq Y. Al-Naffouri, M. Kashan Mobeen, Khaled N. Salama, Atif Shamim

    Research output: Contribution to journalArticlepeer-review


    A new, compact and wide-band Quadrature Phase Shift Keying (QPSK) modulator is presented for remote sensing applications. The microstrip-based modulator employs quadrature hybrid coupler, Wilkinson divider, rat race coupler and GaAs MESFET switches. It is designed to be part of an X band remote sensing transmitter with a center frequency of 8.25GHz. The fabricated module demonstrates the lowest reported amplitude and phase imbalances (0.1dB and 0.4° respectively) around its center frequency. The modulation, tested up to 160 Mbps data rate, displays carrier suppression greater than 30 dB. With negligible DC power consumption and low insertion loss, it operates for a wide bandwidth of 3 GHz (7-10 GHz). The effect of amplitude and phase imbalance is investigated on the performance of the modulator. Finally, a transmitter employing this modulator exhibits an excellent overall Error Vector Magnitude (EVM) of around 8 % that is considerably low as compared to the typically obtained values for such transmitters.
    Original languageEnglish (US)
    JournalCanadian Journal on Electrical and Electronics Engineering
    StatePublished - Sep 30 2012

    Bibliographical note

    KAUST Repository Item: Exported on 2020-10-01


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