Jan Craninckx

A 1.8-GHz low-phase-noise CMOS VCO using optimized hollow spiral inductors

A completely integrated 1.8-GHz low-phase-noise voltage-controlled oscillator (VCO) has been realized in a standard silicon digital CMOS process. The design relies heavily on the integrated spiral inductors which have been realized with only two metal layers and without etching. The effects of high-frequency magnetic fields and losses in the heavily doped substrate have been simulated and modeled with finite-element analysis. The achieved phase noise is as low as -116 dBc/Hz at an offset frequency of 600 kHz, at a power consumption of only 6 mW. The VCO is tuned with standard available junction capacitances, resulting in a 250-MHz tuning range.

A fully integrated CMOS DCS-1800 frequency synthesizer

This design integrates a 4/sup th/ order type-2 charge-pump PLL frequency synthesizer for the DCS-1800 system in a standard 0.4 /spl mu/m CMOS process without external components. The VCO uses an integrated hollow planar inductor, formed in the 2 metal levels available on a lowly-doped substrate. The coil has a symmetrical octagonal shape and size optimized using 2-D circular finite-element analysis. Skin effect and eddy current losses are minimized, and the quality factor is 8.6. VCO phase noise is -122.5 dBc/Hz at 600 kHz offset and tuning range is 20%.

A 1.75-GHz/3-V dual-modulus divide-by-128/129 prescaler in 0.7-/spl mu/m CMOS

A dual-modulus divide-by-128/129 prescaler has been developed in a 0.7-/spl mu/m CMOS technology. A new circuit technique enables the limitation of the high-speed section of the prescaler to only one divide-by-two flipflop. In that way, a dual-modulus prescaler with the same speed as an asynchronous divider can be obtained. The measured maximum input frequency of the prescaler is up to 2.65 GHz at 5 V power supply voltage. Running at a power supply of 3 V, the circuit consumes 8 mA at a minimum input frequency of 1.75 GHz.

A 1.8-GHz CMOS low-phase-noise voltage-controlled oscillator with prescaler

The implementation of the two high-frequency building blocks for a low-phase-noise 1.8-GHz frequency-synthesizing PLL in a standard 0.7-/spl mu/m CMOS process is discussed. The VCO uses on-chip bondwires, instead of spiral inductors, for low noise and low power. The design of these bondwire inductors is discussed in great detail. A general formula for the theoretical limit of the phase noise of LC-tuned oscillators is presented. The design of a special LC-tank allows a trade-off between noise and power. The realized VCO has a phase noise of -115 dBc/Hz at 200 kHz from the 1.8-GHz carrier and consumes 8 mA from a 3-V supply. The prescaler has a fixed division ratio of 128 and uses an enhanced ECL-alike high-frequency D-flipflop. Its power consumption is 28 mW.

A 65fJ/Conversion-Step 0-to-50MS/s 0-to-0.7mW 9b Charge-Sharing SAR ADC in 90nm Digital CMOS

A fully dynamic SAR ADC is proposed that uses passive charge-sharing and an asynchronous controller to achieve low power consumption. No active circuits are needed for high-speed operation and all static power is removed, offering power consumption proportional to sampling frequency from 50MS/s down to 0. The prototype implementation in 90nm digital CMOS achieves 7.8 ENOB, 49dB SNDR at 20MS/s consuming 290 muW. This results in a FOM of 65fJ/conversion-step.

Low-noise voltage-controlled oscillators using enhanced LC-tanks

Frequency synthesizers used in modern telecommunication systems, such as cellular telephones, need to have very low phase noise. Therefore, in the design of high performance frequency synthesizers using Phase Locked Loops (PLL), the Voltage-Controlled Oscillator (VCO) has become a key issue. The trend towards monolithic Integration poses some major challenges. This paper discusses the phase noise aspects of LC-tuned oscillators. A general formula is developed, based on the concepts of effective resistance and capacitance. The formula also applies for oscillators using active inductors. From these results the importance of an inductor with very low series resistance is apparent. To circumvent the technological limits given by an Inductors series resistance, a presented enhanced LC-tank can be used to make a trade-off between noise and power.

An 820μW 9b 40MS/s Noise-Tolerant Dynamic-SAR ADC in 90nm Digital CMOS

Current trends in analog/mixed-signal design for battery-powered devices demand the adoption of cheap and power-efficient ADCs. SAR architectures have been recently demonstrated as able to achieve high power efficiency in the moderate-resolution/medium- bandwidth range in Craninckx, J. and Van der Plas, G., (2007). However, when the comparator determines in first instance the overall performance, as in most SAR ADCs, comparator thermal noise can limit the maximum achievable resolution. More than 1 and 2 ENOB reductions are observed in Craninckx, J. and Van der Plas, G., (2007) and Kuttner, F., (2002), respectively, because of thermal noise, and degradations could be even worse with scaled supply voltages and the extensive use of dynamic regenerative latches without pre-amplification. Unlike mismatch, random noise cannot be compensated by calibration and would finally demand a quadratic increase in power consumption unless alternative circuit techniques are devised.

Flexible Baseband Analog Circuits for Software-Defined Radio Front-Ends

This paper presents a novel approach to design a digitally programmable low pass filter (LPF) and variable gain amplifier (VGA) intended for a software-defined radio (SDR) front-end. These flexible analog circuits are driven by a network-on-chip (NoC) that is able to set performance parameters like cut-off frequency, selectivity, noise, and gain guaranteeing at any time a near-optimal power/performance trade-off. A design approach is proposed to tackle the challenges imposed by flexibility in analog design. A silicon prototype is realized in 0.13-mum CMOS technology with 1.2-V supply voltage to prove the validity of the proposed solution. The LPF provides a frequency tuning range between 0.35 MHz and 23.5 MHz with an adaptive integrated noise level between 85 muVrms and 163 muVrms whereby the power consumption conveniently varies from 0.72 mW to 21.6 mW according to the required performance. The VGA is made up of two cascaded gain stages and provides a gain range from about 0 dB to 39 dB with a reconfigurable power/bandwidth.

A 40 nm CMOS 0.4–6 GHz Receiver Resilient to Out-of-Band Blockers

A highly-linear software-defined radio operating from 400 MHz to 6 GHz is presented, with the purpose of removing any dedicated filtering at the antenna. Very high resilience to out-of-band interference is achieved thanks to a 2.5 V linear LNA and mixer-based RF blocker filter. The 2 mm2, 40 nm digital CMOS receiver achieves +10 dBm out-of-band IIP3 and >; +70 dBm calibrated IIP2 at 3 dB NF. It tolerates 0 dBm blockers at 20 MHz offset with acceptable blocker NF.

A CMOS 1.8 GHz low-phase-noise voltage-controlled oscillator with prescaler

The two HF components for a full CMOS 1.8 GHz frequency synthesizing PLL, the VCO and prescaler, are realized. The low-phase-noise oscillator employs bondwires for the high-quality on-chip inductor. A special LC tank design enables an even further reduction of the phase noise. The prescaler uses an enhanced ECL-like CMOS D-flipflop and has a fixed division ratio of 128. The VCO and prescaler are integrated in a standard 0.7 /spl mu/m CMOS process.