A novel resonant circuit consisting of transformer-based switched variable inductors and switched accumulation MOS (AMOS) varactors is proposed to realize an ultrawide tuning range voltage-controlled-oscillator (VCO). The VCO IC is designed and fabricated using 0.11 µm CMOS technology and fully evaluated on-wafer. The VCO exhibits a frequency tuning range as high as 92.6% spanning from 1.20 GHz to 3.27 GHz at an operation voltage of 1.5 V. The measured phase noise of -120 dBc/Hz at 1 MHz offset from the 3.1 GHz carrier is obtained.

This paper proposes a novel wide-tunable CMOS low-noise amplifier (LNA) using a variable inductor. The variable inductance can be tuned by shielding the magnetic flux, which uses a metal plate above the inductor. The metal plate can be moved using a MEMS actuator. At the present time, the MEMS actuator has not been implemented yet. In this paper, we present a feasibility study on the proposed LNA using the variable inductor. The proposed LNA uses two variable inductors for input and output impedance matching-tuning. The LNA achieves a power gain (PG) of over 10 dB at a tuning range of 1.6-3.2 GHz.

This paper discusses the design and performance of on-chip passive components of transmission lines (TR) and inductors. First, the measurement technique of on chip passives is discussed. A transmission line that can be used for Gbps signal propagation on Si CMOS is examined. As a high density transmission line structure of diagonal-pair differential TR line is described. Also, a circuit and TR line is introduced for above 10 Gbps signal propagation. The on-chip inductor which is a key passive component in RF application of Si CMOS technology is discussed. We examine some on-chip inductors that have been developed in our group: small area inductor, high performance inductor using WL-CSP (Wafer-Level Chip-Size-Packaging) technology. Finally, a wide tuning range LC-VCO using a variable inductor for RF reconfigurable circuit is introduced.

This paper presents a novel wide tuning range CMOS Voltage Controlled Oscillator (VCO). VCO uses an on-chip variable inductor as an additional variable element to extend the tuning range of VCO. The fabricated variable inductor achieves the variable range of 35%. The VCO was fabricated using 0.35 µm standard CMOS process, and can be tuned continuously from 2.13 GHz to 3.28 GHz (tuning range of 38%) without degradation of phase noise. Wide tunable LC-VCO using a variable inductor is one of the key circuits for reconfigurable RF circuit.

A new concept of changing inductance values has been proposed, where a part of meander inductor is short circuited to reduce effective line length. Microwave characteristics of the short-circuited meander inductors and the meander inductor without the short circuit have been designed and fabricated on resin circuit boards. The reduction of inductance values by 40% has been successfully realized for the microwave frequency range from 0.5 GHz to 5 GHz for both designed and measured results. Using the proposed structure, low pass filters having two different cut-off frequencies have been designed and tested. Measured cut-off frequency changed 3.0 GHz to 4.2 GHz.