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A simple automatic tuning circuit is proposed which is suitable for controlling very large channel resistance of weak-inverted transistors operated in the linear regime. The channel resistance for 1.2 MΩ nominal value presents about ± 0.6% variation for −20–80°C temperature range, ±5% variation at process/temperature (P/T) corners and total harmonic distortion = −42 dB for differential signals. The supply voltage was VDD = 1 V and the current consumption was about 470 nA. The proposed concept and the performance were confirmed and evaluated by simulations using standard 0.35 μm CMOS process.

An adaptive impedance tuning circuit (AITC) is used to compensate for the impedance between the arbitrary load impedance and the characteristic impedance of interest. An AITC is required for correct and accurate load impedance measurements. A new type of mismatch measurement circuit that measures the arbitrary load impedance more accurately is proposed and its performance against existing methods is compared. The proposed circuit exhibits a significant performance improvement compared with the conventional method, and it could be applied to different communication systems that have a variety of input signal strengths.

A power-efficient, process, voltage and temperature (PVT) robust gds cancellation method for gain enhancement is proposed. The method generates a negative conductance, which matches and cancels the positive conductance. This makes the gds cancellation method effective over process and wide temperature variation without the aid of external calibration or a tuning circuit. The method senses signals from cascode nodes instead of output nodes, making the method insensitive to output voltage swing. The simulation results of an example implementation in IBM 0.13 µm process show at least 22 dB DC gain enhancement over all process corners and temperatures ranging from − 20 to 80°C, with less than 9% power consumption overhead.

This paper proposes a class-F synchronous rectifier using an independent second harmonic tuning circuit for the power receiver of 2.4 GHz wireless power transmission systems. The synchronous rectifier can be designed by inverting the RF output port to the RF input port of the pre-designed class-F power amplifier based on time reversal duality. The design of the class-F power amplifier deploys an independent second harmonic tuning circuit in the matching networks to individually optimize the impedances of the fundamental and the second harmonic. The synchronous rectifier at the 2.4 GHz frequency is designed and implemented using a 6 W gallium nitride high electron mobility transistor (GaN HEMT). Peak RF-dc conversion efficiency of the rectifier of 69.6% is achieved with a dc output power of about 7.8 W, while the peak drain efficiency of the class-F power amplifier is 72.8%.

A digitally controlled oscillator (DCO) suitable for multi-standards radio-frequency (RF) operation is presented. It has an LC topology using an active inductor based on CMOS controllable inverters. The tunability of the oscillator frequency is ensured by varying the digital word applied to the inverters’ control voltages. The proposed DCO has a small area and exhibits a high-frequency tuning range while achieving low power consumption with good stability against process variations.

An ultra-low-power tunable bump circuit is presented. It incorporates a novel wide-input-range tunable pseudo-differential transconductor linearised using the drain resistances of saturated transistors. Measurement results show that the transconductor has a 5 V differential input range with <20% of linearity error. The bump circuit demonstrates tunability of the centre, width and height, consuming 18.9 nW power from a 3 V supply, occupying 988 μm2 in a 0.13 μm CMOS process.

A 245 GHz sensor system for gas spectroscopy is presented, which includes an integrated SiGe transmitter (TX) and receiver (RX), and a 0.6 m-long gas absorption cell between the TX and RX modules. The integrated local oscillators (LOs) of TX and RX chips are controlled by two external phase-locked loops (PLLs), whose reference frequencies are swept with constant frequency offset for a low intermediate frequency of the RX. The RX consists of a differential low-noise amplifier, an integrated 122 GHz LO with a 1/64 divider, a 90° differential hybrid and an active subharmonic mixer. The TX consists of an integrated 122 GHz LO with a 1/64 divider, and a frequency doubler. The TX and RX chips are fabricated in 0.13 µm SiGe BiCMOS technology with fT/fmax of 300 GHz/500 GHz. Using external dielectric lenses for the TX and RX modules, the gas absorption spectra were measured for acetonitrile and methanol.

A new continuously tunable optoelectronic oscillator based on shifted dispersion-induced RF-fading is proposed and experimentally demonstrated. The design provides wideband continuously all-optical tunability by incorporating the shifted RF-fading based on a Mach-Zehnder structure in an optoelectronic feedback loop. By simply varying the path difference between the two arms of the Mach-Zehnder configuration via an adjustable variable delay line, the fundamental frequency of the oscillator can achieve extremely high and continuous tuning with a frequency upper bound dependent on the delay properties of the variable optical delay line.

A bump circuit with flexible tuning ability that uses 500 times less power and is smaller than previous circuits has been demonstrated by researchers at the University of Tennessee in the US. The bump circuit is a family of circuits with bell-shaped, non-linear transfer functions. First appearing in 1991, they are widely used to provide similarity or distance measures in analogue signal processing systems such as support vector machines, neural networks and analogue machine-learning systems. The researchers from the University of Tennessee designed their circuit as an important building block in an analogue deep-learning machine, which is able to perform unsupervised learning and extract salient features from high-dimensional input data, with a much better power efficiency than the existing digital machine learning implementations.

Wireless power transfer (WPT), through the transmission of contactless energy, is not only being used for charging batteries in smartphones, but it is also being increasingly used in the field of industrial applications. The capacitive based approach is utilized in this paper because of its ability to transmit power in a metal surrounding environment where the inductive-based approach failed to perform. This work focuses on the coupling study of a rotary CPT application where the power supply is stationary while the load rotates and therefore allows the load to rotate 360o free rotation. The Class E MOSFET power inverter is used here due to its ability to achieve high efficiency compared to other class of converters at high frequency. The prototype of the CPT for rotary application has also been successfully developed with disk plate thickness of 1mm-2mm. Overall, the developed CPT system for rotary application is able to deliver 5.5Watt with 83.33% efficiency. To enhance the power efficiency and ZVS conditions, a self-tuning circuit using phased-locked-loop has been proposed in this paper. The efficiency of the developed system with self-tuning circuit is increased to 97.%.