Siqi Zhu

Washington State University, Pullman, WA, United States

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Publications (6)2.23 Total impact

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    ABSTRACT: An 8-channel Ku band (12.5 GHz-14.7 GHz) transmit beamformer has been proposed and fabricated in a 0.18um SiGe BiCMOS technology, which has small phase variation over gain states and low gain/phase imbalance between channels. A current-steering variable gain amplifier (VGA) is proposed with constant current consumption for all gain states to maintain the input impedance, which achieves a small RMS phase variation of ±0.07°/dB. In addition to parasitics prediction from electromagnetic simulations, the layout of the 8-channel transmit beamformer is symmetrically designed to reduce gain/phase imbalance between channels. The RMS gain imbalance for channels 2-7 is ±0.14 dB and the RMS phase imbalance is ±0.71°, which, to the best knowledge of the authors, is the lowest compared to recently reported beamformers.
    Microwave Conference (EuMC), 2013 European; 01/2013
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    ABSTRACT: An ultra-wideband low phase variation variable gain amplifier (VGA) in 0.18/am BiCMOS process with high linearity is presented in this paper. The proposed VGA uses novel current steering gain blocks to achieve gain steps with low phase variation. The VGA has a measured gain range of 6.3-8.1 dB over the entire frequency range of 12-40 GHz and shows a phase variation of 0.2-0.78 °/dB. The VGA achieves a simulated input P1dB of 0 dBm at 26 GHz while consuming only 20.5 mW from 1.5 V power supply and occupies an active area of just 0.05 mm2. The VGA shows 7.6 times better Figure of Merit as compared to current state-of-the-art VGAs.
    Circuits and Systems (ISCAS), 2013 IEEE International Symposium on; 01/2013
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    ABSTRACT: A low phase error X-band eight-channel SiGe PIN diode phased array receiver for 9.5-11.5 GHz application has been proposed and fabricated in a commercial 0.18-μm SiGe BiCMOS process. High performance PIN diode switches used in phase shifters ensure low phase error for all phase states. The 9.5-11.5 GHz receiver, which consists of LNAs, VGAs, PIN diode passive phase shifters and active combiners, achieves over 10 dB measured average gain, less than 5 dB NF (at max. gain and ref. phase state) per channel. The RMS gain error is less than 1 dB and the RMS phase error is less than 4.8° at 9.5-11.5 GHz for all phase states. To the authors' best knowledge, this receiver achieves the lowest RMS phase error in multi-channel X-band phased array receivers using passive phase shifting method.
    Microwave Integrated Circuits Conference (EuMIC), 2013 European; 01/2013
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    ABSTRACT: A compact low phase imbalance broadband attenuator has been proposed and fabricated in a standard 0.18-um SiGe BiCMOS process. This inductor-less attenuator takes advantage of high linearity and low junction capacitance of the SiGe PIN (P-type Intrinsic N-type) diodes to achieve comparable performances with its GaAs counterparts. Symmetrical placement of PIN diodes in reference and attenuation paths ensures low phase imbalance between different attenuation states. T-type resistive network is employed for small chip size and separate DC biases for each bit are implemented to minimize leakage through the parasitic diodes between P-sub and N-well of the PIN diodes. This attenuator, including pads, occupies 0.85×0.412 mm2. It has 8 attenuation states with a 1 dB step. The average insertion loss is 9.2 dB for the reference path and the phase variation for different states is −4.1 to 2.4°, which is the lowest among recently reported broadband attenuators.
    Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International; 01/2012
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    ABSTRACT: A wireless biotelemetry system operates in vivo, which requires low power consumption for long-lasting operation, high output power for long transferable distance, and high throughput for incorporating many recording electrodes and transmitting raw brain signals. An implantable 2.4-GHz on-off keying (OOK) transmitter with high throughput and high energy efficiency for wireless biotelemetry systems has been designed in a 0.18-μm CMOS process. To balance power consumption and output power, a complementary voltage-controlled oscillator for the proposed transmitter is employed. Power consumption of the transmitter is reduced by switching the oscillator on and off to generate an OOK modulated signal. The transient delay for the transmitter is derived and applied to implement a high throughput transmitter. Rat skin-mimic emulating the implant environment such as electrical properties of the skin is used to measure the proposed transmitter in vitro. To transmit 136 Mb/s of OOK data, the transmitter consumes 3 mW of dc power and generates an output power of -14 dBm. The transmitter achieves energy efficiency of 22 pJ/bit with an associated bit error rate of 1.7 × 10<sup>- 3</sup> without using an error correction scheme.
    IEEE Transactions on Microwave Theory and Techniques 01/2011; · 2.23 Impact Factor
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    ABSTRACT: A 2.4 GHz on-off keying (OOK) transmitter with high data rate up to 136 Mb/s for biotelemetry applications has been designed in a 0.18 μm CMOS process. Power consumption of the transmitter is reduced by 38 percent with the proposed mechanism of switching an oscillator on and off to generate an OOK modulated signal. The TX for 136 Mb/s OOK data has a DC power consumption of 3 mW and an output power of -14 dBm. The TX achieves energy efficiency of 22 pJ/bit with an associated BER of 1.7×10<sup>-3</sup>. The TX, including a 2.4 GHz omni directional antenna, is implemented on a printed-circuit board measuring 8×9 mm<sup>2</sup> in size.
    Microwave Symposium Digest (MTT), 2010 IEEE MTT-S International; 06/2010