A CMOS low-noise low-power quadrature LC oscillator

IEICE Electron. Express

2009

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Abstract:A new LC quadrature voltage-controlled oscillator (LC-QVCO), made with direct coupling of two CMOS LC-VCOs, is presented. In the proposed circuit two identical cross-connected LC-VCOs are coupled together by directly connecting the bulk of the crossconnected transistors of one VCO to the bulk of the MOS varactors of the other VCO in such a way no extra devices are needed for coupling. Thus, no extra noise sources and power consumption are added to the core VCOs and results in high performance of QVCO. A Linear analysis of the circuit and the result of simulation in a 0.18 μm CMOS technology are presented. The same proposed coupling scheme can be used for multiphase signal generation as well. Simulation shows the proposed QVCO can operate with supply voltage as low as 0.5 V .

“…1 (a) [4]. Each of the four crossconnected transistors M 1−4 is placed in a separate well, as their bulks need to be connected to different potentials.…”

Section: The Proposed Lc-qvcomentioning

confidence: 99%

A new low-phase noise direct-coupled CMOS LC-QVCO

Ebrahimi

IEICE Electron. Express

2009

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“…An approach frequently encountered in the recent published literature is the coupling of two identical core LC-VCOs [5][6][7][8][9][10][11][12][13][14][15][16][17]. The core LC-VCOs are symmetric circuits which generate two oscillating outputs with identical waveforms and with half period phase difference between them [15].…”

Section: Introductionmentioning

confidence: 99%

“…The core LC-VCOs are symmetric circuits which generate two oscillating outputs with identical waveforms and with half period phase difference between them [15]. Due to their low phase noise, these types of QVCOs are popular in RF circuits [5][6][7][8][9][10][11][12][13][14][15][16][17]. Based on the mechanism of coupling of the two core LC-VCOs, the LC-QVCOs can be divided into two main categories.…”

Section: Introductionmentioning

confidence: 99%

A second-harmonic LC-quadrature voltage controlled oscillator with direct connection of MOSFETs’ substrate

Hemmati

Analog Integr Circ Sig Process

2011

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This work introduces a new low noise secondharmonic quadrature voltage controlled oscillator (QVCO) made by coupling two identical cross-connected LC voltage controlled oscillators. In each of the core oscillators the substrate nodes of the MOS varactors, and also the substrate nodes of the cross-connected MOSFETs are configured in such a way that they act as common mode nodes. Then the core oscillators are coupled together via direct connection of the substrates of the MOS varactors in one of the core oscillators to the substrates of the cross-connected MOSFETs in the other core oscillator, and vice versa. No extra elements are used for coupling of the two core oscillators and therefore no extra noise sources are imposed on the circuit. Operation of the proposed QVCO was investigated with simulation using a commercial 0.18 lm RF CMOS technology: it shows a power dissipation of 9.7 mW from a 1.8 V supply voltage and a simulated phase noise of -125.5 dBc/Hz at 1 MHz offset from center oscillation frequency of 5 GHz. Since the tail transistor can be eliminated, the proposed QVCO can operate with supply voltages as low as 0.5 V, as confirmed with simulation.

“…Due to their low phase noise and low power consumption, LC-QVCOs have received lots of attention in the recent years [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. LC-QVCOs are usually made of coupling two identical cross-connected LC-VCOs in which oscillating signals are injected from one oscillator to the other and vice versa [2].…”

Section: Introductionmentioning

confidence: 99%

“…Depending on their mechanism of operation, LC-QVCOs can be categorized in two main groups. In the first group, two identical LC-VCOs are coupled in an ''in-phase anti-phase'' manner in such a way that the first harmonic oscillating signals are injected from each of the core oscillator to the other [2][3][4]. In the second group known as superharmonic QVCOs, the second harmonic oscillating signals, instead of the first harmonics, from a common mode node in each of the core oscillators are injected to the other.…”

Section: Introductionmentioning

confidence: 99%

A new robust capacitively coupled second harmonic quadrature LC oscillator

Ebrahimi

Analog Integr Circ Sig Process

2010

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A study of some reported superharmonic LC quadrature voltage-controlled oscillator (LC-QVCO) is performed in which it is shown that robustness of the quadrature oscillation varies depending on the coupling configuration. Next, a new superharmonic LC-QVCO is proposed in which the common source node in either of two identical cross-connected LC-VCOs is coupled via a capacitor to the node common between the two varactors in the LC-tank of the other LC-VCO. As a result of connecting common mode nodes, the currents flowing through the two coupling capacitors are comprised of only the even harmonics. In the proposed coupling configuration there exists a closed loop through which the second harmonic signals circulate. A qualitative argument is presented to justify the robustness of the quadrature nature of the proposed QVCO by applying the Barkhausen phase criterion to the second harmonic signals in the loop. Since the coupling devices are only two capacitors, no extra noise sources and power consumption are added to the core VCOs. A Monte-Carlo simulation showed that the phase error of the proposed QVCO caused by device mismatches is no more than 1°. Also, generalizing this method to several numbers of VCOs in a loop, multiphase signals can be generated. The proposed circuits were designed using a 0.18-lm RF CMOS technology and simulation results are presented.