Current reused LC VCOs

This paper presents current reused voltage controlled oscillator (VCO) topologies by stacking switching transistors in series like a cascode. The VCOs can operate with only half the amount of dc current compared to those of the conventional VCO topologies. Fabricated in 0.18-/spl mu/m CMOS process, a differential VCO operates in a 2.1-GHz band with a phase noise of -110dBc/Hz at 1-MHz offset, and a quadrature VCO operates in a 3.1-GHz band with a phase noise of -102dBc/Hz at 1-MHz offset. The proposed topologies can be adopted for low-power applications.     

A 5-GHz low phase noise differential colpitts CMOS VCO

A low noise 5-GHz differential Colpitts CMOS voltage-controlled oscillator (VCO) is proposed in this letter. The Colpitts VCO core adopts only PMOS in a 0.18-/spl mu/m CMOS technology to achieve a better phase noise performance since PMOS has lower 1/f noise than NMOS. The VCO operates from 4.61 to 5 GHz with 8.3% tuning range. The measured phase noise at 1-MHz offset is -120.42 dBc/Hz at 5 GHz and -120.99 dBc/Hz at 4.61 GHz. The power consumption of the VCO core is only 3 mW. To the authors' knowledge, this differential Colpitts CMOS VCO achieves the best figure of merit (FOM) of 189.6 dB at 5-GHz band.     

Frequency dependence on bias current in 5 GHz CMOS VCOs: impact on tuning range and flicker noise upconversion

The tuning curve of an LC-tuned voltage-controlled oscillator (VCO) substantially deviates from the ideal curve 1//spl radic/(LC(V)) when a varactor with an abrupt C(V) characteristic is adopted and the full oscillator swing is applied directly across the varactor. The tuning curve becomes strongly dependent on the oscillator bias current. As a result, the practical tuning range is reduced and the upconverted flicker noise of the bias current dominates the 1/f/sup 3/ close-in phase noise, even if the waveform symmetry has been assured. A first-order estimation of the tuning curve for MOS-varactor-tuned VCOs is provided. Based on this result, a simplified phase-noise model for double cross-coupled VCOs is derived. This model can be easily adapted to cover other LC-tuned oscillator topologies. The theoretical analyses are experimentally validated with a 0.25 /spl mu/m CMOS fully integrated VCO for 5 GHz wireless LAN receivers. By eliminating the bias current generator in a second oscillator, the close-in phase noise improves by 10 dB and features -70 dBc/Hz at 10 kHz offset. The 1/f/sup 2/ noise is -132 dBc/Hz at 3 MHz offset. The tuning range spans from 4.6 to 5.7 GHz (21%) and the current consumption is 2.9 mA.     

8-GHz CMOS quadrature VCO using transformer-based LC tank

A fully integrated quadrature VCO at 8 GHz is presented. The VCO is implemented using a transformer-based LC tank in 0.18 /spl mu/m CMOS technology, in which two VCOs are coupled to generate I-Q signals. The VCO is realized employing the drain-gate transformer feedback configuration proposed here. This makes use of the quality factor enhancement in the resonator using a transformer and the deep switching-off technique by controlling gate bias. By turning off switching transistors of the differential VCO core deeply, the phase noise performance is improved more than 10 dB. The measured phase noise values are -110 and -117 dBc/HZ at the offset frequencies of 600 kHz and 1 MHz respectively. The tuning range of 250 MHz is achieved with the control voltage from 0 to 1 V. The VCO draws 8 mA in two differential core circuits from 3 V supply. When the bias voltage goes down to 2.5 V, the phase noise decrease only 2 dB compared to that of 3 V bias. The VCO performances are compared with previously reported quadrature Si VCOs in 5/spl sim/12 GHz frequency range.     

Low phase noise IP VCO for multistandard communication using a 0.35-/spl mu/m BiCMOS SiGe technology

In this letter, we report that a commonly used 0.35-/spl mu/m, 60-GHz-F/sub MAX/ BiCMOS SiGe monolithic microwave integrated circuit (MMIC) technology is able to provide very low phase noise signal generation in the X-band frequency range. This statement has been demonstrated using a differential LC voltage-controlled oscillator (VCO) in which varactors are realized with metal-oxide semiconductor (MOS) transistors and inductors with a patterned ground shield technology. This VCO features an output power signal in the range of -5 dBm and exhibits a phase noise of -96 dBc/Hz at a frequency offset of 100kHz from carrier and -120 dBc/Hz at a frequency offset of 1 MHz. The VCO features a tuning range of 430 MHz or 4.3% of its operating frequency. Its power consumption is in the range of 70 mW (200 mW with buffers circuits) for a chip size of 800/spl times/1000 /spl mu/m/sup 2/ (including RF probe pads).     

A compact 43-GHz monolithic differential VCO in 0.5-/spl mu/m InP DHBT technology

A compact monolithic integrated differential voltage controlled oscillator (VCO) using 0.5-/spl mu/m emitter width InP/InGaAs double-heterostructure bipolar transistors with a total chip size of 0.42 mm /spl times/ 0.46 mm is realized by using cross-coupled configuration for extremely high frequency satellite communications system applications. The device performance of F/sub max/ greater than 320 GHz at a current density of 5 mA//spl mu/m/sup 2/ and 5-V BVceo allows us to achieve a low phase noise 42.5-GHz fundamental VCO with -0.67-dBm output power. The VCO exhibits the phase noise of -106.8 dBc/Hz at 1-MHz offset and -122.3 dBc/Hz at 10-MHz offset from the carrier frequency.     

A fully integrated 5.8 GHz U-NII band 0.18-/spl mu/m CMOS VCO

A fully integrated 5.8 GHz CMOS L-C tank voltage-controlled oscillator (VCO) using a 0.18-/spl mu/m 1P6M standard CMOS process for 5 GHz U-NII band WLAN application is presented. The VCO core circuit uses only PMOS to pursue a better phase noise performance since it has less 1/f noise than NMOS. The measurement is performed by using a FR-4 PCB test fixture. The output frequency of the VCO is from 5860 to 6026 MHz with a 166 MHz tuning range and the phase noise is -96.9 dBc/Hz at 300 kHz (or -110 dBc/Hz at 1 MHz) with V ctrl = 0 V. The power consumption of the VCO excluding buffer amplifiers is 8.1 mW at V/sub DD/ = 1.8 V and the output power is -4 dBm.     

11-GHz CMOS differential VCO with back-gate transformer feedback

A fully integrated back-gate transformer feedback CMOS differential voltage-controlled oscillator (VCO) has been designed for high-frequency and low-phase noise operation using an 0.18-/spl mu/m CMOS process. The proposed VCO topology utilizes the monolithic transformer feedback configuration from the drain to the back-gate of the switching transistors in VCO. The VCO operating in an 11-GHz band shows the phase noise of -109dBc/Hz at 1-MHz offset, and draws around 3.8mA in the differential core circuits from a 1.8-V power supply.     

5-GHz CMOS LC VCOs with wide tuning ranges

A 4.8-GHz LC voltage-controlled oscillator (VCO) optimized for maximum tuning range was designed and fabricated using 0.25-/spl mu/m 1P5M CMOS process. The optimized design used an inverse proportionality between the two parasitic capacitances of the inductor and the MOS transistors for minimizing the parasitic capacitance at the oscillation node. The fabricated LC VCO has a wide tuning range of 20.3% from 4.32 GHz to 5.3 GHz with a power dissipation of 7.3 mW. This tuning range performance is comparable to, or better than, those of the reported CMOS LC VCOs in 5-GHz band. The measured phase noise is -82 dBc/Hz and -114.6 dBc/Hz at 100 KHz and 1-MHz offset, respectively.     

A low-phase-noise K-band CMOS VCO

A novel circuit topology for low-phase-noise voltage controlled oscillators (VCOs) is presented in this letter. By employing a PMOS cross-coupled pair with a capacitive feedback, superior circuit performance can be achieved especially at higher frequencies. Based on the proposed architecture, a prototype VCO implemented in a 0.18-/spl mu/m CMOS process is demonstrated for K-band applications. From the measurement results, the VCO exhibits a 510-MHz frequency tuning range at 20GHz. The output power and the phase noise at 1-MHz offset are -3dBm and -111dBc/Hz, respectively. The fabricated circuit consumes a dc power of 32mW from a 1.8-V supply voltage.     

一种双带宽UHF主从耦合式LC VCO

为了满足无线通信系统应用需要,设计了一种主从耦合式LC压控振荡器(VCO).基于0.18 μm CMOS标准工艺,由一个5 GHz主VCO和两个起分频作用的从VCO组成,其中主VCO选用PMOS考毕兹差分振荡结构,在两个互补交叉耦合的从VCO的输出端之间设置有注入式NMOS器件以达到分频的目的.仿真及硬件电路实验结果表明,在1.8 V低电源电压下,5 GHz主VCO的调谐范围为4.68～5.76 GHz,2.5 GHz从VCO的调谐范围为2.32～2.84 GHz;在1 MHz的偏频下,5 GHz主VCO的相位噪声为118.2 dBc/Hz,2.5 GHz从VCO的相位噪声为124.4 dBc/Hz.另外,主从VCO的功耗分别为6.8 mW和7.9 mW,因此特别适用于低功耗、超高频短距离无线通信系统中.     

Fully integrated 5.35-GHz CMOS VCOs and prescalers

Two 5.35-GHz monolithic voltage-controlled oscillators (VCOs) and two prescalers have been fabricated in a digital 0.25-μm CMOS process. One VCO uses p⁺/n-well diodes, while the other uses MOS varactors, Q of 57 at 5.5 GHz and 0 V bias (low-Q condition) for a p ⁺/n-well varactor has been achieved. For an MOS varactor, it is possible to achieve a quality factor of 140 at 5.5 GHz. The tuning ranges of the VCOs are >310 MHz, and their phase noise is <-116.5 dBc/Hz at a 1-MHz offset while consuming ~7 mW power at V_DD=1.5 V. The low phase noise is achieved by using only PMOS transistors in the VCO core and by optimizing the resonator layout. The prescalers utilize a variation of the source-coupled logic. The power consumption is 4.1 mW at 1.5-V V_DD and 5.4 GHz. By widening the transistors in the first three divide-by-two stages, the maximum operating frequency is increased to 9.96 GHz at V_DD=2.5 V     

Noise property of a quadrature balanced VCO

A quadrature balanced voltage controlled oscillator (B-VCO) with current source switching is proposed and analyzed. This letter shows analytically that the switching improves the phase noise. A switched transistor is also used as a coupling transistor to generate quadrature signals without degrading the phase noise. To investigate the effect of quadrature coupling on the phase noise, a single B-VCO and a quadrature B-VCO are implemented with identical components in an 0.18-/spl mu/m CMOS process. Both VCO cores draw about 8.8mA under a low bias voltage of 1.8V. The oscillation frequencies are 10.21GHz and 10.81GHz. The measured phase noises of the single at an offset frequency of 1MHz VCO is -114.83 dBc/Hz while that of the quadrature VCO is -116.67 dBc/Hz. The quadrature B-VCO is superior to the single B-VCO with respect to phase noise and oscillation frequency in the X-band.     

A low-phase-noise and low-power multiband CMOS voltage-controlled oscillator

A low voltage multiband all-pMOS VCO was fabricated in a 0.18-/spl mu/m CMOS process. By using a combination of inductor and capacitor switching, four band (2.4, 2.5, 4.7, and 5 GHz) operation was realized using a single VCO. The VCO with an 1-V power supply has phase noises at 1-MHz offset from a 4.7-GHz carrier of -126 dBc/Hz and -134 dBc/Hz from a 2.4-GHz carrier. The VCO consumes 4.6 mW at 2.4 and 2.5 GHz, and 6 mW at 4.7 and 5 GHz, respectively. At 4.7 GHz, the VCO also achieves -80 dBc/Hz phase noise at 10-kHz offset with 2 mW power consumption.     

A low phase-noise CMOS VCO with harmonic tuned LC tank

This paper presents a phase-noise reduction technique for voltage-controlled oscillators (VCOs) using a harmonic tuned (HT) LC tank. The phase-noise suppression is achieved through almost rectangular-shaped voltage at the switching differential cell, which effectively maximizes the slope of the switching cell output voltage at a zero crossing point. In addition, the proposed technique also suppresses the down-conversion of the noise around the second harmonic frequency by the second harmonic short of the tank. One second HT VCO and two third HT VCOs are designed and implemented to evaluate the concept using a 0.35- and 0.13-/spl mu/m CMOS process. The figure-of-merit (FOM) of the second HT VCO, third HT VCO1, and third HT VCO2 are -180.7, -183.7, and -189.5, respectively. The best FOM performance of the VCO has phase noises of -100.4, -132.0, and -140.8dBc/Hz at 100-kHz, 1-MHz, and 3-MHz offset frequencies at the 2-GHz carrier, respectively. This VCO consumes 3.29 mA from a 1.8-V supply with the silicon area of 500 /spl mu/m/spl times/750 /spl mu/m.     

Ultra-low-Voltage high-performance CMOS VCOs using transformer feedback

A transformer-feedback voltage-controlled oscillator (TF-VCO) is proposed to achieve low-phase-noise and low-power designs even at a supply below the threshold voltage. The advantages of the proposed TF-VCO are described together with its detailed analysis and its cyclo-stationary characteristic. Two prototypes using the proposed TF-VCO techniques are demonstrated in a standard 0.18-/spl mu/m CMOS process. The first design using two single-ended transformers is operated at 1.4 GHz at a 0.35-V supply using PMOS transistors whose threshold voltage is around 0.52 V. The power consumption is 1.46 mW while the measured phase noise is -128.6 dBc/Hz at 1-MHz frequency offset. Using an optimum differential transformer to maximize quality factor and to minimize the chip area, the second design is operated at 3.8 GHz at a 0.5-V supply with power consumption of 570 /spl mu/W and a measured phase noise of -119 dBc/Hz at 1-MHz frequency offset. The figures of merits are comparable or better to that of other state-of-the-art VCO designs operating at much higher supply voltage.     

Theoretical analysis of low phase noise design of CMOS VCO

A theoretical analysis on low phase noise of voltage-controlled oscillators (VCOs) based on complementary cross-coupled LC VCO by 0.35-/spl mu/m complementary metal oxide semiconductor technology is demonstrated. From the procedure of optimization steps, the excess noise factor of the amplifier coming from the active device has been determined. The proposed VCO operates at 2 GHz with phase noise of -116 dBc/Hz at offset frequency 600 kHz. The power consumption is 22.62 mW under 3 V bias with 9.1% frequency tuning. The achievement of low phase noise is also matched with prediction by formula in the frequency domain.     

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 2 V 1.8 GHz fully integrated CMOS dual-loop frequency synthesizer

A 2 V 1.8 GHz fully integrated CMOS dual-loop frequency synthesizer is designed in a standard 0.5 /spl mu/m digital CMOS process for wireless communication. The voltage-controlled oscillator (VCO) required for the low-frequency loop is designed using a ring-type VCO and achieves a tuning range of 89% from 356 to 931 MHz and a phase noise of -109.2 dBc/Hz at 600 kHz offset from 856 MHz. With an active chip area of 2000/spl times/1000 /spl mu/m/sup 2/ and at a 2 V supply voltage, the whole synthesizer achieves a tuning range from 1.8492 to 1.8698 GHz in 200 kHz steps with a measured phase noise of -112 dBc/Hz at 600 kHz offset from 1.86 GHz. The measured settling time is 128 /spl mu/s and the total power consumption is 95 mW.     

A 900-MHz 1.5-V CMOS voltage-controlled oscillator using switched resonators with a wide tuning range

A 900-MHz fully integrated VCO was fabricated in a 0.18-/spl mu/m foundry CMOS process. Under 1.5 V power supply, this VCO can be tuned from 667 MHz to 1156 MHz which corresponds to a 53.6% tuning range. The VCO has nearly constant phase noise over the whole tuning frequency, credit to the switched resonators used in this VCO. The phase noise at a 600 kHz offset is -123.1 dBc/Hz at 1125 MHz center frequency and -124.2 dBc/Hz at 667 MHz center frequency.