Oscillator Core Research Articles

20-GHz Differential Colpitts VCO in 0.35-μm BiCMOS

This work presents a differential Colpitts voltage controlled oscillator (VCO) with 8% tuning range at 20 GHz based upon the understanding on symbolic expressions of negative resistance and phase noise theory. Implemented in a 0.35-μm BiCMOS technology with f T = 60 GHz, the VCO has an output power of −4.8 dBm. The lowest phase noise is −85 dBc/Hz, and −111 dBc/Hz at 100-kHz and 1-MHz offset, respectively. The power consumption of oscillator core is 34 mW under a −3-V supply. The chip only occupies an area of 370 μm × 610 μm. Moreover, a comparison between two topologies of Colpitts VCO shows that the proposed topology is prior to the conventional in high frequency applications.

A 1 V 2.2 mW 7 GHz CMOS Quadrature VCO Using Current-Reuse and Cross-Coupled Transformer-Feedback Technology

A current-reused quadrature voltage-controlled oscillator (CR-QVCO) is proposed with the cross-coupled transformer-feedback technology for the quadrature signal generation. This CR-QVCO has the advantages of low-voltage/low-power operation with an adequate phase noise performance. A compact differential three-port transformer, in which two half-circle secondary coils are carefully designed to optimize the effective turn ratio and the coupling factor, is newly constructed to satisfy the need of signal coupling and to save the area consumption simultaneously. The quadrature oscillator providing a center frequency of 7.128 GHz for the ultrawideband (UWB) frequency synthesizer use is demonstrated in a 0.18 mum RF CMOS technology. The oscillator core dissipates 2.2 mW from a 1 V supply and occupies an area of 0.48 mm2. A tuning range of 330 MHz (with a maximum control voltage of 1.8 V) can be achieved to stand the frequency shift caused by the process variation. The measured phase noise is -111.2 dBc/Hz at 1 MHz offset from the center frequency. The IQ phase error shown is less than 2deg. The calculated figure-of-merit (FOM) is 184.8 dB.

A digitally controlled 2.4-GHz oscillator in 65-nm CMOS

This paper presents a 2.4-GHz digitally controlled oscillator (DCO). The circuit is designed using a 65-nm six-metal CMOS technology with an operating voltage of 1.2 V. The DCO comprises an LC oscillator core and the digital interface logic. It has a frequency range of about 200 MHz covering the 2.4-GHz ISM band, with around 5 MHz available for frequency modulation. Its frequency quantization step is approximately 20 kHz, with a digital SigmaDelta-modulator used to allow a 5-bit fractional digital control and provide an effective frequency resolution better than 1 kHz. Its free running oscillation phase noise is -125 dBc/Hz at 1 MHz frequency offset with 4.8 mA biasing current. The power consumption is adjustable from 1.8 mW to 12 mW.

Ka Band Phase Locked Loop Oscillator Dielectric Resonator Oscillator for Satellite EHF Band Receiver

This paper describes the design and fabrication of a Ka Band PLL DRO having a fundamental oscillation frequency of 19.250 GHz, used as local oscillator in the low-noise block of a down converter (LNB) for an EHF band receiver. Apposite circuital models have been created to describe the behaviour of the dielectric resonator and of the active component used in the oscillator core. The DRO characterization and measurements have shown very good agreement with simulation results. A good phase noise performance is obtained by using a very highQdielectric resonator.

A 600 $\mu$W BAW-Tuned Quadrature VCO Using Source Degenerated Coupling

A bulk-acoustic wave (BAW)-tuned quadrature voltage-controlled oscillator (BQVCO) designed in 0.13 mum CMOS is presented. The BQVCO operates at 2.1 GHz, with a power consumption of 600 muW at a 1 V supply. The oscillator achieves a phase noise of -143.5 dBc/Hz at 1 MHz offset with a figure of merit (FOM) of 212.1 dB. A new time-varying source degeneration coupling mechanism has been used to quadrature-couple the two oscillator cores for I/Q signal generation, reducing the required headroom of the series coupling transistors. A binary weighted capacitor array is designed for fine frequency tuning of the QVCO. For comparison, an identical QVCO with on-chip LC tank is fabricated, achieving a FOM of 179.7 dB.

Phase-Noise Reduction of $X$-Band Push–Push Oscillator With Second-Harmonic Self-Injection Techniques

A low phase-noise X-band push-push oscillator using proposed feedback topology is presented in this paper. The oscillator core was implemented in a 0.18-mum CMOS process. By using a power splitter and a delay path in the feedback loop connecting the output and current source of the oscillator, a part of the oscillator output power injects to the oscillator itself. With the proper phase delay in the feedback loop and high transconductance of the current source, a low phase-noise oscillator is achieved. The amplitude stability and phase stability are analyzed, the phenomena of the phase-noise reductions are derived, and the device-size selections of the oscillator are investigated. The time-variant function, impulse sensitivity function, is also adopted to analyze the phase-noise reductions of the second-harmonic self-injected push-push oscillator. These theories are verified by the experiments. This self-injected push-push oscillator achieves low phase noise of -120.1 dBc/Hz at 1-MHz offset from the 9.6-GHz carrier. The power consumption is 13.8 mW from a 1.0-V supply voltage. The figure-of-merit of the oscillator is -188.3 dBc/Hz. It is also the first attempt to analyze the second-harmonic self-injected push-push oscillator

Core region of Arctic Oscillation and the main atmospheric events impact on the Arctic

Arctic Oscillation (AO) is a seesaw pattern in which sea level pressure (SLP) at the polar and middle latitudes in North Hemisphere fluctuates between positive and negative phases. It has been used as a representative atmospheric circulation index to express climate change. The purpose of this paper is to reveal the regional difference of SLP variation. By calculating the correlation coefficients of AO Index with all the gridded SLPs, we have uncovered a special region named as Arctic Oscillation Core Region (AOCR), where the running correlation coefficients (RCC) between gridded SLP and AO index are all negative. The averaged SLP of this region correlates significantly with the AO index. The correlations between local SLPs and AO index outside of AOCR are weaker than those inside. RCC analysis reveals several strong discrepant events different from AO. These events occurred in the years of 1954, 1955, 1962, 1971, 1982/83, 1995, 1996/97, 1998, and 1999. A comparison of these events and the ENSO or PDO indices suggests that the events in 1982/83 and 1998 are probably associated with the ENSO processes. Events centered in other years are likely connected with PDO, which reached their minima in the years of 1950, 1955, 1962 and 1971. The result in this study provides an alternative insight to look at the mechanism of the variation of Arctic Oscillation.

9.6/4.8 GHz dual-mode voltage-controlled oscillator with injection locking

A prototype dual-mode voltage-controlled oscillator supporting two simultaneous oscillation modes is fabricated and demonstrated in a 0.18 µm CMOS process. The oscillator has two resonant ports while sharing one bias. Injection locking is applied to lock the low frequency, 4.8 GHz, to half of the high frequency, 9.6 GHz. The oscillator core consumes 7 mA from a 1.8 V supply. Measurement shows a tuning range of 5% and phase noise is −103 and −109 dBc/Hz measured at 1 MHz offset from the high and low frequency tones, respectively.

A 24-GHz SiGe phased-array receiver-LO phase-shifting approach

A local-oscillator phase-shifting approach is introduced to implement a fully integrated 24-GHz phased-array receiver using SiGe technology. Sixteen phases of the local oscillator are generated in one oscillator core, resulting in a raw beam-forming accuracy of 4 bits. These phases are distributed to all eight receiving paths of the array by a symmetric network. The appropriate phase for each path is selected using high-frequency analog multiplexers. The raw beam-steering resolution of the array is better than 10/spl deg/ for a forward-looking angle, while the array spatial selectivity, without any amplitude correction, is better than 20 dB. The overall gain of the array is 61 dB, while the array improves the input signal-to-noise ratio by 9 dB.

The hippocampal intrinsic network oscillator

Oscillatory activity characterizes the activity of the hippocampus in vivo; however, the underlying mechanism remains unknown. It is also known that during oscillations the number of action potentials provided by the principal cells is surprisingly low, and it is still an open question how oscillations can emerge under such constraints. One suggestion is that the discharge activity of inhibitory cells takes this function; however, this has been found, in my previous studies, not to be the case for cholinergically mediated and intrinsically generated hippocampal oscillations. This study identifies the hippocampal intrinsic network oscillator and the interactions which underlie the concurrent expression of cholinergically mediated theta (4-15 Hz) and gamma (20-80 Hz) oscillations. A particular axonal network that involves the hippocampal associative pathway, shown to consist of axonal collaterals of CA2 and some CA3 pyramidal cells, forms the oscillator core element. It is functionally activated via two cholinergically mediated reactions. First, direct activation of CA2 and CA3 pyramidal cells to discharge. Second, enhancement of gap junction-mediated axo-axonic interactions among axons of the core element and associated axons of interneurones, which together form the full oscillator. With these two reactions it is possible to explain the rhythmicities and patterns of activity, under the condition of a low number of action potentials. The discharge of CA3 pyramidals serves mainly as a trigger, while firing by CA2 pyramidals, and to a lesser degree by CA3 pyramidals, maintains the oscillatory activity. The cholinergically mediated 2-fold increase in axonal gap junction communication between cells serves two functions: (a) creation of specific activation pathways to produce the rhythmicities and patterns, and (b) formation of a reverberatory system that extends the time during which the sparsely generated action potentials can interact in the network, thereby providing a new source of action potentials, critical for the expression of oscillatory activity.

Performance-optimized microstrip coupled VCOs for 40-GHz and 43-GHz OC-768 optical transmission

We present 40- and 43-GHz voltage-controlled oscillators (VCOs) for use in SONET/SDH optical transmission systems operating at OC-768 rates. SONET system jitter requirements are explained, as are methods for achieving the requisite performance in manufacturable oscillators. We describe in detail a technique for using quadrature-coupled VCOs to achieve a fundamental improvement in jitter power performance. The 40-GHz oscillator has a tuning range of 5 GHz, a single-sideband phase-noise power spectral density of -99 dBc/Hz at 1-MHz offset from the carrier, and consumes 207 mW in the oscillator core. Total power consumption is 363 mW (including biasing and output buffers) from a 3-V supply. The oscillator occupies 0.189 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of die area and is implemented in a 120-GHz f/sub T/ SiGe BiCMOS process.

A 300-μm W 1.9-ghz cmos oscillator utilizing micromachined resonators

A low-power low-phase-noise 1.9-GHz RF oscillator is presented. The oscillator employs a single thin-film bulk acoustic wave resonator and was implemented in a standard 0.18-μm CMOS process. This paper addresses design issues involved in codesigning micromachined resonators with CMOS circuitry to realize ultralow-power RF transceiver components. The oscillator achieves a phase-noise performance of -100 dBc/Hz at 10-kHz offset, -120 dBc/Hz at 100-kHz offset, and -140 dBc/Hz at 1-MHz offset. The startup time of the oscillator is less than 1 μs. The oscillator core consumes 300 μA from a 1-V supply.

Analysis and design of an optimally coupled 5-GHz quadrature LC oscillator

A 5-GHz quadrature LC oscillator has been realized, in which the two LC stages are coupled with phase shifters. Analysis on the behavioral level shows that an N-stage LC oscillator is optimally coupled when each stage is connected with phase shifters providing /spl plusmn/180/spl deg//N phase shift. Simulation of the 5-GHz two-stage quadrature LC oscillator reveals a 4.3-dB reduction in phase noise compared to a quadrature LC oscillator without phase shifters. Measurements of the 5-GHz quadrature LC oscillator, made in a 30-GHz f/sub T/ process, show a phase noise lower than -113 dBc/Hz, with a resonator quality factor of only 4 and an oscillator core power dissipation of 21.2 mW.

The effect of varactor nonlinearity on the phase noise of completely integrated VCOs

This work discusses variations in phase noise over the tuning range of a completely integrated 1.9-GHz differential voltage-controlled oscillator (VCO) fabricated in a 0.5-/spl mu/m bipolar process with 25-GHz f/sub t/. The design had a phase noise of -103 dBc/Hz at 100 kHz offset at the top of the tuning range, but the noise performance degraded to -96 dBc/Hz at 100 kHz at the bottom of the tuning range. It was determined that nonlinearities of the on-chip varactors, which led to excessively high VCO gain at the bottom of the tuning range, were primarily responsible for this degradation in performance. The VCO has a power output of -5 dBm per side. Calculations predict phase noise with only a small error and provide design insight for minimizing this effect. The oscillator core drew 6.4 mA and the output buffer circuitry drew 6 mA, both from a 3.3-V supply.

A universal 0.03-mm/sup 2/ one-pin crystal oscillator in CMOS

A one-pin crystal oscillator with an integrated load capacitance of 15 pF has been realized in a standard 0.35-/spl mu/m CMOS technology. Due to the structure of the oscillator and the use of MOS gate capacitance for the load capacitors, the chip area can be very small. The total active area including load capacitors is less than 0.03 mm/sup 2/. The design can be operated with supply voltages in the range of 1.4-3.6 V and allows crystal frequencies in the range of 3-30 MHz. The current consumption of the oscillator core is 180 /spl mu/A at 10 MHz with 3.3-V power supply. It produces a rail-to-rail output swing, regulated by an amplitude control loop, and has the same flexibility and ease of frequency tuning as a common Pierce oscillator. As no special IC process options are required, the design is very suitable for clock generation in digital very-large-scale-integration chips.

Rainfall extremes in some selected parts of Central and South America: ENSO and other relationships reexamined

El Niños and anti-El Niños (La Niñas) are known to be associated with rainfall extremes in several parts of the globe. However, not all El Niños show good associations. Recently, a finer classification of El Niño events was attempted. It was noticed that Unambiguous ENSOW (El Niño–Southern Oscillation, Warm) events (years when El Niño existed, and the Tahiti minus Darwin pressure difference (T−D) minima and equatorial eastern Pacific sea surface temperature (SST) maxima occurred in the middle of the calendar year) were very well associated with droughts in India and southeast Australia (Tasmania). In addition, C (cold SST, La Niña) events showed reverse effects (excess rains) in these regions. In the present paper, rainfall in selected regions in Central and South America are examined. For the Southern Oscillation Core Region (low latitudes, 155°W–167°E) and for the Gulf–Mexico region, no finer classification was necessary. All El Niños were associated with excess rains and all La Niñas with droughts. As in India and Tasmania, Unambiguous ENSOW years were associated with droughts in some parts of northeast Brazil (Ceara, Rio grande do Norte, Paraiba, Pernambuco) and excess rains in Chile and Peru. C events did not have good associations except in Chile and Peru, where droughts occurred. The effect of El Niños showed some dependence on the month of commencement. In years when El Niños showed no effect, considerable influence of other factors (e.g. Atlantic SST on northeast Brazil rainfall) was noticed. Thus, predictions based on El Niño alone are likely to be erroneous, a fact which should be noted by the mass media. Effects of the recent El Niño of 1997–1998 are discussed. Copyright © 1999 Royal Meteorological Society

A 2.1-MHz crystal oscillator time base with a current consumption under 500 nA

A micropower crystal oscillator module for watch applications is presented. The integrated circuit is encapsulated with a 2.1-MHz crystal in a miniature vacuum package to reduce parasitic effects. The circuit comprises frequency tuning with a resolution of /spl plusmn/3 s/year ~/spl plusmn/0.1 parts per million (ppm)\ and auxiliary circuits. A single output delivers a signal of 16 384 Hz with a frequency stability of /spl plusmn/2 ppm over the temperature range (-10 to 70/spl deg/C). The oscillator core has two complementary active MOSFET's and amplitude stabilization in order to get both low power consumption and high stability. New coupling and biasing circuits between the oscillator and the dynamic frequency dividers allow to achieve a current consumption under 0.5 /spl mu/A for a supply voltage between 1.8 and 3.5 V.