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Phase Locked Loop Design
Published in Mike Golio, Commercial Wireless Circuits and Components Handbook, 2018
There are two types of fluctuating phase terms. The first is the discrete signal components, which appear in the spectral density plot. These are commonly referred to as spurious signals. The second type of phase instability is random in nature and is commonly called phase noise. There are many sources of random phase perturbations in any electronic system, such as thermal, shot, and flicker noise. One description of phase noise is the spectral density of phase fluctuations on a per-Hertz basis. The term spectral density describes the energy distribution as a continuous function, expressed in units of phase variance per unit bandwidth. The spectral density is described by the following equation () Sϕ(fm)=Δϕrms2(fm)measurementBW
Frequency Synthesis and Clock Recovery
Published in Bang-Sup Song, Micro CMOS Design, 2017
One most straightforward way to achieve low phase noise is to increase the loop bandwidth. The inverse of the open loop gain, which is defined as PNTF, high-pass shapes the VCO phase noise within the PLL loop bandwidth. Assume that the output frequency of fo = 2.441 GHz is synthesized with a channel spacing of 1 MHz. If an integer-N synthesizer is used, N = 2441 and fref = 1 MHz, but the same frequency can also be synthesized with a fractional-N synthesizer, N = 244.1 and fref = 10 MHz. That is, fractional-N PLL can suppress the VCO phase noise with a 10× wider bandwidth. Note that if smaller than 1 MHz channel spacing is desired, the loop bandwidth of the integer-N synthesizer gets narrower accordingly.
Continuous-Time Circuits
Published in Tertulien Ndjountche, CMOS Analog Integrated Circuits, 2017
where in2¯Δf is the power spectral density of the current noise source, and Γrms is the root-mean-square value of the ISF. In the simple case where a noise-free sinusoid waveform is used for the ISF determination, we have Γrms2=1/2, and the noise contribution due to the parasitic resistance Rp alone can be derived from Equation (7.112), assuming that in2¯Δf=4kT/Rp and qmax = CVmax, where Vmax is the maximum voltage swing across the LC tank. The time-variant noise analysis approach is limited by the fact that the determination of the ISF can require complex simulations. In practice, simulation programs such as SpectreRF can be used to compute the phase noise directly.
Design of a Voltage-Controlled Oscillator for Ka-Band Applications
Published in IETE Journal of Research, 2022
As shown in (26), the phase noise is dependent on temperature, current, offset frequency, fundamental frequency, and tank quality factor. For example, by increasing the current, the phase noise improves, but the power consumption is increased. Also, with the higher quality factor, the lower phase noise is obtained. In this paper, the quality factor of the tank is improved by a varactor-less technique, because the quality factor of the varactor is low for the high frequency, as shown in Figure 3. Therefore, the phase noise of this technique is better than the tank with varactor, since the oscillation frequency is adjusted with the current ( and ). Also, we designed VCO at a low frequency which is generated the fundamental and the second harmonic frequency; then the operational frequency is increased with a differential amplifier. This technique help designer to have a good trade-off between noise figure and operational frequency because it is difficult to have a low noise figure at high frequency. Figure 11 illustrates the phase noise of the proposed VCO and a VCO with varactor. As shown in Figure 11, the phase noise of the proposed technique is improved.
Design of Dual-Delay-Path Low-Power VCRO with I-MOS Varactor Tuning
Published in IETE Journal of Research, 2021
Table 4 shows the phase noise performance of the proposed VCRO. The phase noise L(Δf) of the ring VCO [22, 23] is given as follows: where , ΔV = gate overdrive voltage, γ = a coefficient which depends on the device condition, η = characteristic constant, Δf = offset frequency and Pdissi. = total power dissipation, Vdd = supply voltage. Differential ring oscillator-based VCO have a tradeoff between various parameters such as tuning range, phase noise, multiphase output generation and power, among them phase noise is the most vital parameter. Phase noise may be considered as the power spectrum of output frequency of an oscillator not being concentrated on a centre frequency, rather it is spread adjacent to the fundamental frequency. Phase noise can also be measured as an output signal power to noise power at an offset from the oscillation frequency ranging from KHz to MHz and expressed as dBc/Hz. There are few parameters that affect the phase noise performance such as offset frequency, high temperature and power consumption [24–26]. By selecting proper delay structure phase noise may be minimized to some extent. In the proposed VCRO, phase noise results have been obtained at 0.6 and 1 MHz offset from the centre frequency for different values of supply voltage (Vdd) and source/drain voltage (Vids). Phase noise waveforms are shown in Figure 11(a–c).
Design and Performance Analysis of Active Inductor Based VCO for IEEE 802.11a/b/g/n/ac Applications
Published in International Journal of Electronics, 2020
The purity of transmitted signal and the adjacent channel rejection are affected by the phase noise of oscillator. The phase noise of the generated signal will degrade the signal-to-noise ratio (SNR) of the signal. Again, phase noise of VCO affects the performance of AM detectors or SSB detectors. In case of digital transmission system, for example, in phase-shift keying (PSK), phase noise will affect the performance parameter bit error rate (BER). Furthermore, large value of phase noise will cause transmission error due to incorrect detection in digital phase detection. In case of active inductor-based VCO, the amount of phase noise is large due to presence of active elements. However, VCO with passive inductor exhibits good phase noise performance. So, active inductor-based VCO adds more noise than the passive LC VCO. However, the area consumption of the LC VCO will be greater than active inductor-based VCO.