Andrea Mazzanti

Analysis and design of injection-locked LC dividers for quadrature generation

Injection-locked LC dividers for low-power quadrature generation are discussed in this paper. Modeling the circuits as regenerative frequency dividers leads to very simple analytical expressions for the locking band, phase deviation from quadrature and phase noise. Maximizing the ratio between the injected and the biasing current is beneficial to all the above parameters whereas reducing the tank quality factor improves locking band and quadrature accuracy, though at the expense of current consumption, for given output amplitude. To validate the theory, experiments have been carried on a 0.18-/spl mu/m CMOS direct conversion IC, embedding an injection-locked quadrature generator, realized for the Universal Mobile Telecommunication System. Frequency locking range as large as 24% and phase deviation from quadrature around 0.8/spl deg/ are measured while each divider consumes 2 mA. The phase noise of the quadrature generator is determined by the driving oscillator phase noise because the dividers contribution is easily made negligible up to hundreds of megahertz offset.

Novel Insight Into the Natural History of Short QT Syndrome

Objectives This study intends to gain further insights into the natural history, the yield of familial and genetic screening, and the arrhythmogenic mechanisms in the largest cohort of short QT syndrome (SQTS) patients described so far. Background SQTS is a rare genetic disorder associated with life-threatening arrhythmias, and its natural history is incompletely ascertained. Methods Seventy-three SQTS patients (84% male; age, 26 ± 15 years; corrected QT interval, 329 ± 22 ms) were studied, and 62 were followed for 60 ± 41 months (median, 56 months). Results Cardiac arrest (CA) was the most frequent presenting symptom (40% of probands; range, <1 month to 41 years). The rate of CA was 4% in the first year of life and 1.3% per year between 20 and 40 years; the probability of a first occurrence of CA by 40 years of age was 41%. Despite the male predominance, female patients had a risk profile superimposable to that of men (p = 0.49). The yield of genetic screening was low (14%), despite familial disease being present in 44% of kindreds. A history of CA was the only predictor of recurrences at follow-up (p < 0.0000001). Two patterns of onset of ventricular fibrillation were observed and were reproducible in patients with multiple occurrences of CA. Arrhythmias occurred mainly at rest. Conclusions SQTS is highly lethal; CA is often the first manifestation of the disease with a peak incidence in the first year of life. Survivors of CA have a high CA recurrence rate; therefore, implantation of a defibrillator is strongly recommended in this group of patients.

Single-Stage Low-Power Quadrature RF Receiver Front-End: The LMV Cell

This paper presents the first quadrature RF receiver front-end where, in a single stage, low-noise amplifier (LNA), mixer and voltage-controlled oscillator (VCO) share the same bias current. The new structure exploits the intrinsic mixing functionality of a classical LC tank oscillator providing a compact and low-power solution compatible with low-voltage technologies. A 0.13-mum CMOS prototype tailored to the GPS application is presented. The experimental results exhibit a noise figure of 4.8 dB, a gain of 36 dB, an IIP3 of -19 dBm with a total power consumption of only 5.4 mW from a voltage supply of 1.2 V

Programmed ventricular stimulation for risk stratification in the Brugada syndrome: A pooled analysis

Background— The role of programmed ventricular stimulation in identifying patients with Brugada syndrome at the highest risk for sudden death is uncertain. Methods and Results— We performed a systematic review and pooled analysis of prospective, observational studies of patients with Brugada syndrome without a history of sudden cardiac arrest who underwent programmed ventricular stimulation. We estimated incidence rates and relative hazards of cardiac arrest or implantable cardioverter-defibrillator shock. We analyzed individual-level data from 8 studies comprising 1312 patients who experienced 65 cardiac events (median follow-up, 38.3 months). A total of 527 patients were induced into arrhythmias with up to triple extrastimuli. Induction was associated with cardiac events during follow-up (hazard ratio, 2.66; 95% confidence interval [CI], 1.44–4.92, P<0.001), with the greatest risk observed among those induced with single or double extrastimuli. Annual event rates varied substantially by syncope history, presence of spontaneous type 1 ECG pattern, and arrhythmia induction. The lowest risk occurred in individuals without syncope and with drug-induced type 1 patterns (0.23%, 95% CI, 0.05–0.68 for no induced arrhythmia with up to double extrastimuli; 0.45%, 95% CI, 0.01–2.49 for induced arrhythmia), and the highest risk occurred in individuals with syncope and spontaneous type 1 patterns (2.55%, 95% CI, 1.58–3.89 for no induced arrhythmia; 5.60%, 95% CI, 2.98–9.58 for induced arrhythmia). Conclusions— In patients with Brugada syndrome, arrhythmias induced with programmed ventricular stimulation are associated with future ventricular arrhythmia risk. Induction with fewer extrastimuli is associated with higher risk. However, clinical risk factors are important determinants of arrhythmia risk, and lack of induction does not necessarily portend low ventricular arrhythmia risk, particularly in patients with high-risk clinical features.

A Low-Noise Quadrature VCO Based on Magnetically Coupled Resonators and a Wideband Frequency Divider at Millimeter Waves

Wireless on-chip processing at millimeter waves still lacks key functions: quadrature generation enabling direct conversion architectures and simplifying phased-array systems, frequency division with an operating range wide enough to compensate spreads due to component variations. This paper addresses the implementation of these functions, introducing new circuit solutions. The quadrature voltage-controlled oscillator (VCO) relies on a ring of two tuned VCOs, where the oscillation frequency depends on inter-stage passive components only, demonstrating low noise and accurate quadrature phases. Prototypes, realized in 65-nm CMOS, show 56-60.4-GHz tunable oscillation frequency, phase noise better than 95 dBc/Hz at 1-MHz offset in the tuning range, 1.5 maximum phase error while consuming 22 mA from a 1-V supply. The frequency divider is based on clocked differential amplifiers, working as dynamic CML latches, achieving high speed and low power simultaneously. A divider by 4 realized in 65-nm CMOS occupies 15 m 30 m, features an operating frequency programmable from 20 to 70 GHz in nine bands and consumes 6.5 mW.

Oxide Breakdown After RF Stress: Experimental Analysis and Effects on Power Amplifier Operation

The target in the design of CMOS radio-frequency (RF) transceivers for wireless application is the highest integration level, despite reliability issues of conventional submicron MOSFETs, due to high RF voltage and current peaks. In this scenario, this paper investigates gate-oxide breakdown under RF stress by using a class-E power amplifier (PA) for experiments. We showed that maximum RF voltage peaks for safe device operation are much larger than usual DC limits, and that the physical mechanism of oxide degradation is triggered by the rms value of oxide field, and not by its maximum, as generally believed. This finding has a strong impact on RF circuit designs, especially in MOSFET scaling perspectives. Finally, breakdown effects on PA operations are discussed

Gene-Specific Therapy With Mexiletine Reduces Arrhythmic Events in Patients With Long QT Syndrome Type 3

Background Long QT syndrome type 3 (LQT3) is a lethal disease caused by gain-of-function mutations in the SCN5A gene, coding for the alpha-subunit of the sodium channel NaV1.5. Mexiletine is used to block late sodium current and to shorten QT interval in LQT3 patients. Objectives The aim of this study was to determine whether mexiletine prevents arrhythmic events (arrhythmic syncope, aborted cardiac arrest, or sudden cardiac death) in LQT3 patients. Methods The endpoint of this retrospective cohort study, which studied consecutive LQT3 patients who were referred to our center and treated with mexiletine, was to evaluate the antiarrhythmic efficacy of mexiletine by comparing the number of arrhythmic events per patient and the annual rate of arrhythmic events during observation periods of equal duration before and after the beginning of therapy with mexiletine. Results The study population comprised 34 LQT3 patients, 19 (56%) of whom were male. The median age at beginning of treatment with mexiletine was 22 years, and median QTc interval before therapy 509 ms. The median duration of oral mexiletine therapy was 36 months, at an average daily dose of 8 ± 0.5 mg/kg. Mexiletine significantly shortened QTc (by 63 ± 6 ms; p < 0.0001) and reduced the percentage of patients with arrhythmic events (from 22% to 3%; p = 0.031), the mean number of arrhythmic events per patient (from 0.43 ± 0.17 to 0.03 ± 0.03; p = 0.027), and the annual rate of arrhythmic events (from 10.3% to 0.7%; p = 0.0097). Conclusions Besides shortening QTc interval, mexiletine caused a major reduction of life-threatening arrhythmic events in LQT3 patients, thus representing an efficacious therapeutic strategy.

Injection-Locked CMOS Frequency Doublers for

On-chip frequency generators for high frequency applications suffer from degradation of key passive components, variable capacitors in particular. In this framework, frequency multipliers can play a key role, allowing the design of voltage-controlled oscillators running at a frequency lower than required with advantage in terms of signal spectral purity and frequency tuning range. In this paper we present two injection locked frequency doublers for Ku-band and F-band applications respectively. Despite differences in implementation details, the same topology where a push-push pair injects a double frequency tone locking an autonomous differential oscillator is adopted. The circuits require limited input signal swing and provide a differential output over a broad frequency range. Dissipating 5.2 mW, the Ku-band multiplier, realized in a 0.13 μm CMOS node, displays an operation bandwidth from 11 GHz to 15 GHz with a peak voltage swing on each output of 470 mV. The F-band multiplier, realized in 65 nm CMOS technology, displays an operation bandwidth from 106 GHz to 128 GHz with a peak voltage swing on each output of 330 mV and a power dissipation of 6 mW. A prototype including the multiplier, driven by a half-frequency standard LC-tank VCO, demonstrates an outstanding 13.1% tuning range around 115 GHz.

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Injection-locked quadrature voltage-controlled oscillators are introduced in this paper as high accuracy, low phase noise, and low-power I and Q generators. A master voltage-controlled oscillator (VCO), running at twice the output frequency, locks two coupled VCOs. The former determines phase noise while the latter sets phase accuracy, thus, breaking the tradeoff between the two parameters, the main limit of free running coupled VCOs, recently proposed in the framework of highly integrated solutions. The proposed design has been tailored to DCS 1800 and prototypes have been fabricated in a 0.18-mum CMOS technology. Experiments show a phase noise of -127 dBc/Hz and -139 dBc/Hz at 600 kHz and 3 MHz, respectively, while consuming 10 mA from 1.8 V supply. A 185-dB state-of-the-art phase noise figure of merit results. Accuracy between output signals is determined by means of image band rejection (IBR) measurements on a purposely developed single-side-band upconversion mixer. Minimum IBR among 20 samples is as large as 46 dB

-Wave and mm-Wave Applications

High-rate communications technology leveraging the unlicensed spectrum around 60 GHz is almost ready for deployment with several demonstrations of successful wireless links. One key aspect of the transceiver is the ability to handle analog fractional bandwidths in the order of 20%, challenging for both the linear processing chain and the frequency reference generator. In classical LC loaded stages bandwidth trades with gain making them unsuitable for wide band amplifiers at millimeter-waves where the available device gain is relatively low. In this work, we exploit inter-stage coupling realizing higher order filters where wider bandwidth is achieved at the expense of in-band gain ripple only. The receiver adopts a sliding IF architecture employing an integer-N type-II synthesizer, with a three state phase frequency detector charge pump combination, a switched tuned LC VCO followed by a low power wide range divider chain. By judicious choice of charge pump current and filter components integrated phase noise, critical for signal constellation integrity at high rate, is kept low. This paper inspects the inter-stage coupling technique, providing design formulas, and discusses the design of each receiver block. Experiments performed on 65 nm prototypes provide: 6.5 dB maximum noise figure over >;13 GHz bandwidth, -22.5 dBc integrated phase noise while consuming 84 mW.