Changhua Cao

Millimeter-wave voltage-controlled oscillators in 0.13-/spl mu/m CMOS technology

This paper describes the design of CMOS millimeter-wave voltage controlled oscillators. Varactor, transistor, and inductor designs are optimized to reduce the parasitic capacitances. An investigation of tradeoff between quality factor and tuning range for MOS varactors at 24 GHz has shown that the polysilicon gate lengths between 0.18 and 0.24 /spl mu/m result both good quality factor (>12) and C/sub max//C/sub min/ ratio (/spl sim/3) in the 0.13-/spl mu/m CMOS process used for the study. The components were utilized to realize a VCO operating around 60 GHz with a tuning range of 5.8 GHz. A 99-GHz VCO with a tuning range of 2.5 GHz, phase noise of -102.7 dBc/Hz at 10-MHz offset and power consumption of 7-15mW from a 1.5-V supply and a 105-GHz VCO are also demonstrated. This is the CMOS circuit with the highest fundamental operating frequency. The lumped element approach can be used even for VCOs operating near 100-GHz and it results a smaller circuit area.

A 410GHz CMOS Push-Push Oscillator with an On-Chip Patch Antenna

The uses of terahertz systems (300 GHz to 3 THz) in radars, remote sensing, advanced imaging, and bio-agent and chemical detection have been extensively studied. A compact and low-cost signal source is a key circuit block of terahertz systems. Traditionally, the circuits have been built using highly optimized III-V technologies. With the advances of CMOS, it has become realistic to consider terahertz circuits in CMOS. This paper reports a signal source operating near 410 GHz that is fabricated using low-leakage transistors in a 6 M 45 nm digital CMOS technology.

Progress and Challenges Towards Terahertz CMOS Integrated Circuits

Key components of systems operating at high millimeter wave and sub-millimeter wave/terahertz frequencies, a 140-GHz fundamental mode voltage controlled oscillator (VCO) in 90-nm CMOS, a 410-GHz push-push VCO with an on-chip patch antenna in 45-nm CMOS, and a 125-GHz Schottky diode frequency doubler, a 50-GHz phase-locked loop with a frequency doubled output at 100 GHz, a 180-GHz Schottky diode detector and a 700-GHz plasma wave detector in 130-nm CMOS are demonstrated. Based on these, and the performance trends of nMOS transistors and Schottky diodes fabricated in CMOS, paths to terahertz CMOS circuits and systems including key challenges that must be addressed are suggested. The terahertz CMOS is a new opportunity for the silicon integrated circuits community.

A 50-GHz Phase-Locked Loop in 0.13-

A 50-GHz charge pump phase-locked loop (PLL) utilizing an LC-oscillator-based injection-locked frequency divider (ILFD) was fabricated in 0.13-mum logic CMOS process. The PLL can be locked from 45.9 to 50.5 GHz and output power level is around -10 dBm. The operating frequency range is increased by tracking the self-oscillation frequencies of the voltage-controlled oscillator (VCO) and the frequency divider. The PLL including buffers consumes 57 mW from 1.5/0.8-V supplies. The phase noise at 50 kHz, 1 MHz, and 10 MHz offset from the carrier is -63.5, -72, and -99 dBc/Hz, respectively. The PLL also outputs second-order harmonics at frequencies between 91.8 and 101 GHz. The output frequency of 101 GHz is the highest for signals locked by a PLL fabricated using the silicon integrated circuits technology.

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The electromagnetic spectrum between 300GHz and 3THz is broadly referred as terahertz [1]. The utility of this portion of spectrum for detection of chemicals and bio agents, for imaging of concealed weapons, cancer cells and manufacturing defects [1, 2], and for studying chemical species using electron paramagnetic resonance, as well as, in short range radars and secured high data rate communications has been demonstrated. However, high cost and low level of integration for III–V devices needed for the systems have limited their wide use. The improvements in the high frequency capability of CMOS have made it possible to consider CMOS as a lower cost alternative for realizing the systems that can greatly expand the use of this spectrum range.

m CMOS

The feasibility of integrating antennas and required circuits to form wireless interconnects in foundry digital CMOS technologies has been demonstrated. The key challenges including the effects of metal structures associated with integrated circuits, heat removal, packaging, and interaction of transmitted and received signals with nearby circuits appear to be manageable. This technology can potentially be used for intra and inter-chip interconnection, and implementation of true single chip radios, beacons, radars, RFID tags and others, as well as contact-less high frequency testing

Towards terahertz operation of CMOS

A 182-GHz Schottky barrier diode detector has been demonstrated in 130-nm foundry CMOS using signals generated on-chip by modulating the bias current of a push-push voltage controlled oscillator as input. This work demonstrated that it is possible to build a detector operating near the top end of millimeter-wave range using digital CMOS

Silicon Integrated Circuits Incorporating Antennas

The design of millimeter-wave CMOS voltage-controlled oscillators (VCOs) is reviewed. A low parasitic cross-coupled transistor layout is developed, and used to demonstrate a 140-GHz fundamental mode VCO in 90-nm CMOS and a 192-GHz push-push VCO in 130-nm CMOS. These are the circuits with the highest fundamental and harmonic operating frequencies achieved in silicon integrated circuits

A Millimeter-Wave Schottky Diode Detector in 130-nm CMOS Technology

Multi-level modulation of a 16.8-GHz class-E power amplifier with negative resistance enhanced power gain is demonstrated in a 130-nm CMOS process. The circuit achieves power gain of ~ 30 dB, and power-added efficiency (PAE) of 16% for the highest output power level of 6.8 dBm. The average efficiency for a random data pattern is ~ 8%. The circuit also exhibits 10-dBm saturated output power and ~ 22% maximum PAE. By realigning the highest output power level to the 10-dBm saturated output power, the efficiency can be improved. For a random data pattern, this PA should achieve ~ 2X higher efficiency than Class A PAs. The circuit supports seven amplitude levels for 400 Megabits per second (Mbps) data transmission. The multi-level output signal levels follow a square-root relation. The circuit including an address decoder occupies ~ 1.4 mm2.

Millimeter-Wave CMOS Voltage-Controlled Oscillators

The feasibility of CMOS circuits operating at frequencies near 200 GHz has been demonstrated. A 140-GHz fundamental mode VCO in 90-nm CMOS, a 192-GHz push-push VCO in 130-nm CMOS, and a 180-GHz detector circuit in 130nm CMOS have been demonstrated. With the continued scaling of MOS transistors, 1-THz CMOS circuits will be possible in the near future. Index Terms – CMOS, mm-wave, oscillator, Schottky diode, detector, phase locked loop, terahertz.