Browsing by Author "Wu, Ge"

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    A Broadband Variable-Gain Amplifier and a Broadband Self-Calibrated High-Sensitivity Power Detector for the Square Kilometre Array
    (2014-12-03) Wu, Ge; Belostotski, Leonid; Haslett, James W.
    The Square Kilometre Array (SKA) is an international project to design and construct the next generation ultra-sensitive radio telescope. Depending on the final configuration, the SKA will require millions of receivers ideally fabricated in a low cost semiconductor process. This thesis presents a study of using CMOS technologies, which are themost common and less expensive semiconductor option, to implement a variable gain amplifier (VGA) with a linear-in-dB performance and an RMS power detector (PD) for a mid-frequency SKA receiver. Two linear-in-dB VGAs were designed and experimentally verified in this work. The first VGA meets most of the SKA specifications except bandwidth and linear-in-dB range. The second VGA uses a bandwidth extension technique and a low threshold voltage transistor to achieve a maximum tunable gain range of 34 dB and the linear-in-dB range of 28.5 dB within ±1 dB error, an upper 3 dB cutoff frequency of 2.1 GHz and a power consumption of 1.1mW. Both S11 and S22 are less than -10 dB from 100 MHz up to 4.2 GHz. This VGA achieved the lowest power consumption among comparable VGAs published to date. A differential broadband self-calibrated RMS PD using the MOSFET square-law characteristics was proposed and experimentally verified in this work. After automatically compensating mismatches between all circuit components by adjusting input transistor bulk voltage, the proposed PD circuit showed the highest sensitivity and lowest power consumption of all PDs published prior to this work. The PD operates over an input power range from -48 dBm to -11 dBm with output voltage offset less than 0.95 dB for the SKA midfrequency range with an input-referred P1dB of -11 dBm, 3 dB bandwidth of 1.8 GHz and power consumption of only 1.2 mW. This PD meets all requirements of the mid-frequency SKA receiver. This power detector was embedded within the receiver and fabricated in a TSMC 65nm CMOS process. Measurement results showed an input power range from -40 dBm to -20 dBm with power consumption of 1.5mW.