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1. A 49-63 GHz Phase-locked FMCW Radar Transceiver for High Resolution Applications

   Liu, Xuyang; Maktoomi, Md Hedayatullah; Alesheikh, Mahdi; Heydari, Payam; Aghasi, Hamidreza (October 2023, IEEE European Solid State Circuits Conference)

   TPC of IEEE ESSCIRC Conference (Ed.)

   This paper presents an mmWave FMCW radar that can achieve sub-centimeter-scale range resolution at 14- GHz chirp-bandwidth while maintaining the radar range beyond 50 meters. To meet the requirements on power efficiency, chirp linearity, and signal-to-noise ratio (SNR), a phase-locked steppedchirp FMCW radar architecture is introduced. Specifically, a fully integrated radar transceiver comprising an interleaved frequency-segmented phase-locked transmitter and a segmented receiver architecture with high sensitivity is presented. The proposed design addresses the limitations of conventional typeII phase-locked loops (PLLs) in extending the radar bandwidth across multiple sub-bands with identical chirp profiles. Fabricated in a 22nm FD-SOI technology, the prototype chip comprises two sub-bands with 14 GHz of free-running bandwidth and 10 GHz of phase-locked bandwidth. The system achieves -101.7 dBc/Hz phase noise at 1 MHz offset, 8 dBm of effective isotropic radiated power (EIRP), 10 dB noise figure (NF), and 362.6 mW collective power consumption of transmitter and receiver arrays. 

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2. A 23.7 to 29.9 GHz Tunable Fully Differential Voltage Controlled Oscillator Designed in 180nm CMOS process

   https://doi.org/10.1109/DCAS57389.2023.10130248  

   Kakaraparty, Karthik; Mahbub, Ifana (April 2023, 2023 IEEE 16th Dallas Circuits and Systems Conference (DCAS))

   This paper presents the design of a 23.7 to 29.9 GHz wide tuning range VCO (Voltage Controlled Oscillator) designed using a 180 nm CMOS process. In order to achieve a good phase noise performance and get a wide frequency tuning range, cross-coupling and gate biasing techniques are utilized in the proposed cross-coupled LC VCO architecture. The simulated phase noise of −130 dBc/Hz is achieved at a 1 MHz offset. With the supply voltage of 1.8 V, the total power consumption of the VCO is 32.04 mW. The proposed VCO has good performance in terms of low-phase noise and has a wide frequency tuning range, which makes it highly suitable for millimeter wave-based applications. 

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3. Design of a Reverse-Electrowetting Transducer Based Wireless Self-powered Motion Sensor

   https://doi.org/10.1109/ISCAS45731.2020.9180973  

   Tasneem, Nishat T.; Biswas, Dipon K.; Adhikari, Pashupati R.; Reid, Russell; Mahbub, Ifana (October 2020, IEEE International Symposium on Circuits and Systems proceedings)

   This paper presents a self-powered motion sensor based on reverse-electrowetting on dielectric (REWOD) energy harvesting having the capability of remotely keeping a track of any motion activity. The energy harvester includes a rectifier and a voltage regulator to provide the DC supply voltage to the analog front-end and the transmitter to wirelessly transfer the data from the motion sensor. The on-chip circuitry includes a seven-stage voltage-doubler based rectifier, an amplifier, an analog-to-digital converter (ADC), and a transmitter, and is designed in standard 180 nm CMOS process with a supply voltage of 1.8 V. The recycled folded cascode (RFC) based charge amplifier has a closed-loop gain of 53 dB within the bandwidth of 1-150 Hz, which is suitable to detect any low-frequency motion signal. An 8-bit SAR-ADC is designed to digitize the amplified signal with a sampling rate of 1 ksamples/s. The transmitter used for this application operates in the 3.1-5 GHz frequency band with an energy efficiency of 8.5 pJ/pulse at 100 kbps data rate. The wireless motion sensing device with the REWOD can be suitable for quantitatively monitoring the motion-related data as a wearable sensor. 

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4. A 2.53 NEF 8-bit 10 kS/s 0.5 μm CMOS Neural Recording Read-Out Circuit with High Linearity for Neuromodulation Implants

   https://doi.org/10.3390/electronics10050590  

   Tasneem, Nishat Tarannum; Mahbub, Ifana (March 2021, Electronics)

   This paper presents a power-efficient complementary metal-oxide-semiconductor (CMOS) neural signal-recording read-out circuit for multichannel neuromodulation implants. The system includes a neural amplifier and a successive approximation register analog-to-digital converter (SAR-ADC) for recording and digitizing neural signal data to transmit to a remote receiver. The synthetic neural signal is generated using a LabVIEW myDAQ device and processed through a LabVIEW GUI. The read-out circuit is designed and fabricated in the standard 0.5 μμm CMOS process. The proposed amplifier uses a fully differential two-stage topology with a reconfigurable capacitive-resistive feedback network. The amplifier achieves 49.26 dB and 60.53 dB gain within the frequency bandwidth of 0.57–301 Hz and 0.27–12.9 kHz to record the local field potentials (LFPs) and the action potentials (APs), respectively. The amplifier maintains a noise–power tradeoff by reducing the noise efficiency factor (NEF) to 2.53. The capacitors are manually laid out using the common-centroid placement technique, which increases the linearity of the ADC. The SAR-ADC achieves a signal-to-noise ratio (SNR) of 45.8 dB, with a resolution of 8 bits. The ADC exhibits an effective number of bits of 7.32 at a low sampling rate of 10 ksamples/s. The total power consumption of the chip is 26.02 μμW, which makes it highly suitable for a multi-channel neural signal recording system. 

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5. Highly Efficient Rectifier and DC-DC Converter Designed in 180 nm CMOS Process for Ultra-Low Frequency Energy Harvesting Applications

   https://doi.org/10.1109/DCAS51144.2020.9330671  

   Gunti, Avinash; Biswas, Dipon K.; Mahbub, Ifana; Adhikari, Pashupati R.; Reid, Russell C. (November 2020, 2020 IEEE 14th Dallas Circuits and Systems Conference (DCAS))

   null (Ed.)

   This paper presents the integration of an AC-DC rectifier and a DC-DC boost converter circuit designed in 180 nm CMOS process for ultra-low frequency (<; 10 Hz) energy harvesting applications. The proposed rectifier is a very low voltage CMOS rectifier circuit that rectifies the low-frequency signal of 100-250 mV amplitude and 1-10 Hz frequency into DC voltage. In this work, the energy is harvested from the REWOD (reverse electrowetting-on-dielectric) generator, which is a reverse electrowetting technique that converts mechanical vibrations to electrical energy. The objective is to develop a REWOD-based self-powered motion (such as walking, running, jogging, etc.) tracking sensors that can be worn, thus harvesting energy from regular activities. To this end, the proposed circuits are designed in such a way that the output from the REWOD is rectified and regulated using a DC-DC converter which is a 5-stage cross-coupled switching circuit. Simulation results show a voltage range of 1.1 V-2.1 V, i.e., 850-1200% voltage conversion efficiency (VCE) and 30% power conversion efficiency (PCE) for low input signal in the range 100-250 mV in the low-frequency range. This performance verifies the integration of the rectifier and DC-DC boost converter which makes it highly suitable for various motion-based energy harvesting applications. 

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