A varactor configuration minimizing the amplitude-to-phase noise conversion in VCOs

Amplitude-to-phase-noise conversion due to varactors can severely limit the close-in phase noise performance in LC-tuned oscillators. This work proposes a rigorous analysis of this phenomenon, which highlights the fundamental limitations of single-ended tuned and differentially tuned diode varactor configurations. The back-to-back varactor topology is identified as a suitable solution to linearize the tank capacitance. The amplitude to phase noise conversion is greatly attenuated and the 1/f/sup 3/ phase noise is drastically reduced, without impairing the achievable tuning range. These results are validated through circuit simulations in an existing 0.35-/spl mu/m CMOS technology.     

Phase noise up-conversion reduction for integrated CMOS VCOs

The recent progress in standard CMOS integrated VCO design is mainly due to improved modelling and simulation techniques for integrated planar inductors. Further improvement can be achieved by focusing on the active circuitry. A discussion is presented into reducing the up-conversion of low frequency noise     

Millimeter-wave VCOs with wide tuning range and low phase noise, fully integrated in a SiGe bipolar production technology

Millimeter-wave voltage-controlled oscillators (VCOs) are presented which are fully integrated in a SiGe bipolar production technology. The low-cost differential circuits have been designed and optimized for low phase noise and wide tuning range. As an example, by varying the bias voltage of the on-chip varactor, the oscillation frequency can be changed from 36 to 46.9 GHz (i.e., by 26%). In this wide frequency range, phase noise between -107 and -110dBc/Hz at 1-MHz offset frequency and single-ended voltage swing of about 0.95V/sub pp/ /spl plusmn/10% (differential: 1.9V/sub pp/) were measured. The circuit consumes 280mW at -5.5-V supply voltage. The high oscillation frequency and low phase noise at wide tuning range are record values for fully integrated oscillators in Si-based technologies. The basic oscillator was then extended by a cascode stage as an output buffer. Now the VCO performance is no longer degraded if nonperfectly terminated transmission lines are driven. Thus, the chip can be mounted in a low-cost socket; however, at the cost of increased phase noise and power consumption.     

Noise calculations and experimental results of varactor tunableoscillators with significantly reduced phase noise

The single-sideband phase noise of varactor tunable GaAs MESFET oscillators is investigated. Two oscillator circuits with different microstrip resonator circuits were designed and fabricated. Using a resonator consisting of coupled microstrip lines instead of a single microstrip line, which is a planar monolithically integrable structure, phase noise is reduced significantly because the quality factor is higher for the coupled resonator. The phase noise is calculated using a nonlinear time domain method, which solves the Langevin equations, describing the deterministic and stochastic behavior of an oscillator by perturbation methods. Calculated and measured phase noise agree within the accuracy of measurements. The very low phase noise of 95 dBc/Hz at 100 kHz offset frequency is achieved     

Improving linearity in MOS varactor based VCOs by means of the output quiescent bias point

This paper presents a CMOS based LC tank VCO topology improving the tuning range linearity. The VCO tuning range is linearized with PMOS varactors which remain in the inversion region for an extended range of the control voltage. This is achieved with the design of the quiescent operating point in the VCO's output nodes with a value close to the voltage rails, letting the varactors to behave quasi linearly in the achievable VCO tuning range. The experimental results of a VCO in a CMOS 0.35 µm process show a linear tuning range improvement of 75% of the control voltage in the (1.43–1.55) GHz range, with a minimum VCO gain variation compared to similar architectures. The results show a phase noise improvement from −94 dBc/Hz to −124 dBc/Hz @600 kHz offset from the carrier with an overall reduced amplitude noise for the VCO.     

The output signals and noise from a nonlinearity with amplitude-dependent phase shift

On the assumption that each input signal represents only a small part of the total input power, the output signals and output noise spectrum are found by extending the Barrett-Lampard diagonal expansion to the case of the quadrivariate distribution of input amplitude and phase at two different times. This expansion yields a decomposition of the nonlinearity into a summation of generalized Laguerre polynomials with uncorrelated outputs, whose spectra are simply autoconvolutions of the input spectrum. A slight generalization of the notion of memoryless nonlinearity allows this result to he applied very simply to devices, such as limiters and TWT amplifiers, that cause AM-to-PM conversion.     

基于非线性及光延迟的全光相位噪声抑制研究

采用光学非线性混合和可调光延迟方法,抑制激光线宽引起的低速相位噪声,提出并证明了全光的相位噪声抑制方案.采用原始信号的相位共轭和两个窄线宽光泵浦,抑制了激光线宽引起的相位噪声.仿真结果表明,对于具有相同激光线宽的40Gbit/s正交相移键控信号,其误差矢量幅度可从30％优化到14％.     

Concepts and methods in optimization of integrated LC VCOs

Underlying physical mechanisms controlling the noise properties of oscillators are studied. This treatment shows the importance of inductance selection for oscillator noise optimization. A design strategy centered around an inductance selection scheme is executed using a practical graphical optimization method to optimize phase noise subject to design constraints such as power dissipation, tank amplitude, tuning range, startup condition, and diameters of spiral inductors. The optimization technique is demonstrated through a design example, leading to a 2.4-GHz fully integrated, LC voltage-controlled oscillator (VCO) implemented using 0.35-μm MOS transistors. The measured phase-noise values are -121, -117, and -115 dBc/Hz at 600-kHz offset from 1.91, 2.03, and 2.60-GHz carriers, respectively. The VCO dissipates 4 mA from a 2.5-V supply voltage. The inversion mode MOSCAP tuning is used to achieve 26% of tuning range. Two figures of merit for performance comparison of various oscillators are introduced and used to compare this work to previously reported results     

Influence of fiber nonlinearity on the phase noise to intensitynoise conversion in fiber transmission: theoretical and experimentalanalysis

Intensity noise resulting from the phase modulation to intensity modulation conversion of laser phase noise can be a major impairment in direct detection systems. In this paper, we investigate theoretically and experimentally the influence of fiber nonlinearity on the conversion of laser and optical amplifier phase noise to intensity noise by fiber transmission. Very good agreement of relative intensity noise (RIN) spectra at the output of a standard singlemode fiber between experimental data and theoretical predictions has been achieved. Results reveal that the fiber nonlinearity can enhance significantly the RIN magnitude and lead to a shift of the RIN dips toward higher frequencies, and consequently to a broader RIN spectrum at fiber output     

Linearization of oscillation frequency for integrated LC-VCO with inversion-mode varactor

Metal-oxide semiconductor (MOS) varactors are widely used in voltage-controlled oscillators (VCOs) due to the need for a tunable capacitance. Two types of varactors that have been integrated on-chip include the inversion-mode and accumulation-mode types. The inversion-mode varactor offers immunity to latch-up, but suffers from a non-linear C(V) characteristic which directly leads to a nonlinear oscillation frequency tuning curve. This paper proposes an oscillation frequency linearization technique for LC-VCO with an inversion-mode varactor. The linearity of the frequency tuning curve is improved by linearization of C(V) characteristics of the inversion-mode varactor. A new varactor configuration consisting of varactor units and resistor divider network is proposed. The single-switch integrated LC-VCO with the proposed varactor configuration is fabricated in TSMC 0.18 μm CMOS technology. The improvement of linearity of the frequency tuning curve has been verified using mathematical models and measurement results.     

光纤损耗对双环注入锁定光电振荡器相噪的影响

考虑到光纤的延时损耗,对双环注入锁定光 电振荡器(OEO)建立了理论解析模型;基于建立的模型,研究了光纤损耗对 对其相位噪声的影响。通过实验验证了所建模型的正确性,并得出:如考虑光纤的损耗, 振荡信号的相噪并非随着光纤长度 的增加而降低,当光纤长度增加到一定程度时,光纤的损耗会影响到振荡信号的相噪,使得 光电混合谐振腔的品质因子(Q)降低, 最终相噪会随之呈现增加的趋势。本文研究成果能够在工程中得到广泛应用,可为获取 最佳长度光纤延时线提供参考。     

Analytical performance evaluation of the OFDM systems in the presence of jointly fifth order nonlinearity and phase noise

This paper presents an exact theoretical analysis of the performance degradation in an orthogonal frequency division multiplexing (OFDM) system when the signal including phase noise is passed through a nonlinear circuit such as high power amplifier (HPA). This circuit is modeled as a fifth order memory-less nonlinear polynomial model (5th order MLNPM). The nonlinear model is derived from important electrical parameters such as gain, 1-dB compression and 3rd order intercept point. Theoretical analysis shows that the detected data symbol at the receiver consists of attenuated version of the original transmitted data symbol, common phase error (CPE), inter-sub-carrier interference (ICI), third and fifth order intermodulation (IM) components. The analytical expressions for intermodulation noise term are derived using combinatorial methods. By use of the derived expressions, a closed-form output signal to noise ratio (SNR), degradation factor (DF) and probability of error can be evaluated theoretically. For verifying the accuracy of our analysis, comparisons between the theoretical and simulated results with electrical parameter of an actual and applicable HPA are presented. The comparisons show that bit error rate (BER) of analytical results is closely match with simulation results for OFDM system using M-QAM modulation.     

On the effect of Wiener phase noise in OFDM systems

Multicarrier modulation exhibits a significant sensitivity to the phase noise of the oscillator used for frequency down-conversion at the portable receiver. For this reason, it is important to evaluate the impact of the phase noise on the system performance. We present an accurate method to determine the error probability of an orthogonal frequency-division multiplexing (OFDM) system in the presence of phase noise. In particular, four modulation schemes are analyzed and their performances are compared     

The effect of background noise on phase ranging measurements in urban vehicle monitoring systems

The effect of background noise on the performance of phase-trilateration urban vehicle-monitoring systems is discussed. An expression for the density function of the error as a function of such system parameters as carrier-to-noise ratio, frequency deviation, observation time, and bandwidth is derived.     

Analysis of resonator phase shift for two series LC quadrature VCOs

Based on the investigation of resonator phase shift, an analytical framework to compare the phase noise between two series LC quadrature voltage-controlled oscillators (QVCOs) is presented. The bottom- series QVCO is analytically demonstrated to have lower phase noise than the top-series QVCO. Simulation data show good agreement with the presented analysis.     

The effect of crosstalk and phase noise in multichannel coherentoptical ASK systems

The authors extend the analysis of G.J. Foschini et al. (1988) to a two-channel system and to a wider class of IF filters. The authors carry out a comprehensive study of the sensitivity of an optical receiver in a two-channel ASK system, taking into account phase noise and crosstalk, including crosstalk arising from phase noise in the second channel. They compare the results with previous work in the limit of no phase noise and show how the agreement is good. They compute the penalty due to crosstalk for different linewidths and filter shapes. It is shown that the minimum channel spacing is a few bit rates more than the IF filter bandwidth, and is therefore increased significantly by significant phase noise. The detailed IF filter shape appears to have only a weak effect     

The influence of X-ray radiation on the low-frequency noise of integrated circuits

The sensitivity of various parameters of integrated circuits developed by various technologies to X-ray radiation and the possibility to predict the level of low-frequency noise are considered.     

The impact of laser phase noise on the coherent subcarriermultiplexing system

In coherent optical subcarrier multiplexing (CSCM) systems, the laser phase noise may cause signal spectrum broadening and hence, causes significant deterioration in the system performance. The impact of phase noise on the CSCM system is analyzed in terms of carrier-to-noise ratio, intermodulation distortion, and adjacent channel crosstalk. The optimal modulation index and carrier to noise ratio are also presented. Some numerical results are outlined     

Performance degradation of LC-tank VCOs by impact of digital switching noise in lightly doped substrates

In mixed analog-digital designs, digital switching noise is an important limitation for the performance of analog and RF circuits. This paper reports a physical model describing the impact of digital switching noise on LC-tank voltage-controlled oscillators (VCOs) in lightly doped substrates. The model takes into account the propagation from the source of substrate noise to the different components in the VCO and the resulting modulation of the oscillator frequency. The model is validated with measurements on a 3.5-GHz LC-tank VCO designed in 0.18-/spl mu/m CMOS. It reveals that for this VCO, impact occurs mainly via the nonideal metal ground lines for lower frequencies and low tuning voltage and via the integrated inductors for higher frequencies and high tuning voltage. To make the design immune to substrate noise, the parasitic resistance of the on-chip ground interconnect has to be kept as low as possible and inductors have to be shielded. Hence, the developed model allows investigating the dominant mechanisms behind the impact of substrate noise on a VCO, which is crucial information for achieving a substrate noise immune design.     

Fully integrated low phase noise multi-band LC-tank voltage controlled oscillator with switched-capacitor resonator

This paper presents the design and implementation of a fully integrated low noise multi-band LC-tank voltage-controlled-oscillator(VCO).Multi-band operation is achieved by using switched-capacitor resonator.Additional three-bit binary weighted capacitor array is also used to extend frequency tuning range in each band.To lower phase noise,two noise filters are added and a linear varactor is adopted.Implemented in a 0.18 μm complementary-metal-oxide-semiconductor(CMOS) process,the VCO achieves a frequency tuning range covering 2.26～2.48 GHz,2.48～2.78 GHz,2.94～3.38 GHz,and 3.45～4.23 GHz while occupies a chip area of 0.52 mm2.With a 1.8 V power supply,it draws a current of 10.9 mA,10.6 mA,8.8 mA,and 6.2 mA from the lowest band to the highest band respectively.The measured phase noise is-109～-120 dBc/Hz and-121～-131 dBc/Hz at a 1 MHz and 2.5 MHz offset from the carrier,respectively.