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Oscillator Circuits
Published in Mike Golio, Commercial Wireless Circuits and Components Handbook, 2018
As discussed in the section on noise, the oscillator phase noise spectrum is the FM noise spectrum divided by fm2, where fm is the modulating, or carrier offset frequency. Oscillator frequency variations are easily measured with a frequency discriminator or other FM detector such as a transmission line discriminator [35]. Spectrum analyzers are also very useful for measuring oscillator phase noise as long as the analyzer noise is much less than that of the measured device. Spectrum analyzers can measure script L(fm) = PSSB(fm)/Hz/PC where the PSSB(fm)/Hz is the phase noise power per Hertz within the 1/f3 region close to the carrier. Typically if the noise measurement is very near the carrier frequency, i.e., within the f−3 region, the noise is dominated by phase noise. For modulating noise such as power supply pushing the actual phase noise spectrum, Sϕ(fm), is twice script L(fm) because the sidebands are correlated [31].
Ultra-Low-Power RF Transceivers
Published in Krzysztof Iniewski, Wireless Technologies, 2017
Emanuele Lopelli, Johan D. van der Tang, Arthur H. M. van Roermund
The maximum acceptable frequency error after predistortion can be derived by the following considerations. The orthogonality of PN codes has to be preserved. This means that the relative position of the channels along the frequency grid has to remain unchanged with respect to the ideal case. From this consideration, a maximum frequency error equal to the inter-channel spacing minus the channel bandwidth is allowed (for example, 100 kHz). If a 100 kHz maximum channel frequency shift is considered, then there would be the possibility that two channels get adjacent to each other (the interchannel spacing becomes zero). In this situation, if the specification on the oscillator phase noise remains unchanged, the amount of noise leaking in the adjacent channels increases, degrading the SNR in those channels.
A Theoretical and Experimental Study of Injection Pulling in Phase-Locked Optoelectronic Oscillator under Radio Frequency Signal Injection
Published in IETE Journal of Research, 2023
Abhijit Banerjee, Larissa Aguiar Dantas de Britto, Jayjeet Sarkar, Gefeson Mendes Pacheco
Injection-locking is a very effective means of: (a) selecting the desired mode from the multitude of natural oscillation modes possible; (b) heavily suppressing all spurious sidemode resonances. Formerly, it is equivalent to a type I PLL which employs proportional control only. In practice, it has the advantage of an instantaneous PLL-I loop delay and unconditional stability (if within the locking range). A physical implementation of a PLL-I will have a finite loop bandwidth and there may be instability above a proportional gain threshold. The problem is that at the operating frequencies of interest external microwave sources have levels of phase noise that exceed those of the free-running OEO at all offset frequencies except near carrier. This phase noise is injected with unit gain into the oscillator phase noise spectrum in a neighborhood of each mode. The neighborhood is smaller the lower the level of injection but then advantages (a) and (b) can be lost. Phase-locked loop OEO is the preferred means of locking to a system reference because: (1) There is greater controller design freedom. One can introduce integral control in addition to proportional control ensuring a zero asymptotic phase error and technically an infinite locking range. (2) The loop filter may be engineered so that the phase noise spectrum of the oscillator is primarily that of the system reference only where it is smaller than the phase noise of the free oscillator. (3) The PLL-OEO can be modified so that it is stable over the long term without any special enclosure. However, the modulation instability is the main practical limitation of injection-locked and phase-locked loop (IL-PLL OEO). There may be some virtue in using a low level of injection-locking to suppress higher-order sidemodes given that injection-locking is immune from instability caused by loop delay.
A 24 GHz frequency synthesizer for automotive collision avoidance radar
Published in International Journal of Electronics Letters, 2020
As dc bias point is close to the threshold voltage in the moderate inversion region due to this fact, the overdrive voltage is very small, and the drain noise and the main contributor of oscillator phase noise will be suppressed. The effective series resistances of the on-chip inductors, which are also the noise contributor, add the ohmic losses in the substrate and metal, and it is given by Eq. (8) (Thomas, 1998).
Test strategy for a 25-dBm 1-GHz CMOS power amplifier in a wireless power transfer context
Published in International Journal of Electronics, 2021
Fabian L. Cabrera, F. Rangel de Sousa
The backscatter frequency was extracted from the modulated spectrum. An example of the measured spectrum P is shown in Figure 15 when the distance is 12 mm (position A) and the PA power level is 15. The modulating tones can be distinguished at approximately 3.6 MHz from the carrier although the oscillator phase noise.