Noise performance of frequency- and phase-locked CW magnetrons operated as current-controlled oscillators

Low-power continuous wave "cooker" magnetrons driven from industrial-quality switch-mode power supplies have been frequency locked by driving them as current-controlled oscillators in a phase-lock loop (PLL). The noise performance of these frequency-locked oscillators is reported as a function of heater power. The injection of -30- to -40dB signals derived from the reference oscillator of the PLL into the magnetron's output waveguide while the anode current is controlled by the PLL is shown to phase lock the magnetron's output. Results for locking performance are presented.     

A theoretical and experimental study of the noise behavior ofsubharmonically injection locked local oscillators

A method for the phase-noise characterization of optically controlled subharmonically injection-locked oscillators that is based on a nonlinear model of synchronized oscillators is presented. It allows FM noise degradation at large-signal levels to be predicted easily and accurately. The theoretical analysis shows that (1) the nth-order subharmonic injection locking oscillator is primarily locked by the nth harmonic output of an injected signal, which is generated by the nonlinearity of the active device; (2) the minimum FM noise degradation factor of the nth-order subharmonically locked oscillator is n² when the injection power is sufficiently strong; and (3) a subharmonic injection locking LO with low injection power, good FM noise degradation, and large locking range can be designed by determining the optimum injection power level, by selecting the optimal nonlinear multiplication factor, and by decreasing the intrinsic noise level of the active device. The experimental results confirm the accuracy of the analysis     

Optically controlled oscillators for millimeter-wave phased-arrayantennas

An approach for the design of optically synchronized millimeter-wave local oscillators based on a subharmonically injection-locked phase-lock-loop technique is introduced. The experimental results support the desired goal of frequency and phase coherency, phase shift control of millimeter-wave oscillators, and self-oscillating mixing to downconvert a millimeter-wave RF signal. Experimental results and theoretical analysis show the advantages of the proposed approach: large locking range of two subharmonically locked oscillators, lower FM noise degradation, and smaller phase error caused by frequency detuning     

Phase noise in LC oscillators

Analytical methods for the phase-noise analysis of LC-tuned oscillators are presented. The fundamental assumption used in the theoretical model is that an oscillator acts as a large-signal LC-tuned amplifier for purposes of noise analysis. This approach allows us to derive closed-form expressions for the close-to-carrier spectral density of the output noise, and to estimate the phase-noise performance of an oscillator from circuit parameters using hand analysis. The emphasis is on an engineering approach intended to facilitate rapid estimation of oscillator phase noise. Theoretical predictions are compared with results of circuit simulations using a nonlinear phase-noise simulator. The analytical results are in good agreement with simulations for weakly nonlinear oscillators. Complete nonlinear simulations are necessary to accurately predict phase noise in oscillators operating in a strongly nonlinear regime. To confirm the validity of the nonlinear phase-noise models implemented in the simulator, simulation results are compared with measurements of phase noise in a practical Colpitts oscillator, where we find good agreement between simulations and measurements     

Phase Locking of 2-mm Wave Sources Upon High-Order IMPATT Multipliers

We describe experiments resulting in the phase locking of two electrically tunable 2-mm wave sources based on active high-order IMPATT multipliers. Phase locking modes were tested on a pair of identical multiplying sources (master and slave) with the tuning ranges 138.5+/?1.5 GHz (master) and 140.0+/? GHz (slave). The phase lock loop (PLL) system is used to lock the slave source to the master source. The multipliers of this type can translate the spectra of highly stable centimeter-wave oscillators to any part of the millimeter range with the output power 100÷20 mW over the 30 to 140 GHz range without additional amplification. The phase locked sources operate over a 3% frequency band with low phase noise and rapid frequency tuning. The amplitude-frequency characteristics of the sources are presented with the locking-mode signal spectra.     

CMOS injection locked oscillators for quadrature generation at radio-frequency

The design of quadrature local oscillators for CMOS wireless transceivers is still one of the most challenging issues. This paper focuses the advantages of injection locking techniques to achieve high-performance quadrature generators. A synchronizing oscillator sets spectral purity while locked oscillators set quadrature accuracy and drive the mixer LO input capacitances. Two different architectures, realized in a 0.18 μm CMOS technology, are illustrated and compared. The first, using LC tank locked oscillators as frequency dividers, is tailored to UMTS and show high driving capability with low power. Simple and accurate equations for the design are reported. The second quadrature generator, employing coupled VCOs driven by an auxiliary VCO, is tailored to DCS1800 and achieves outstanding phase accuracy and phase noise. Experimental results compare favorably against previously published solutions.     

Low phase-noise microwave oscillators with interferometric signal processing

Phase-noise spectral density of a 9-GHz oscillator has been reduced to -160 dBc/Hz at 1-kHz offset frequency, which is the lowest phase noise ever measured at microwave frequencies. This performance was achieved by frequency locking a conventional loop oscillator to a high-Q sapphire dielectric resonator operating at the elevated level of dissipated power (/spl sim/0.4 W). Principles of interferometric microwave signal processing were applied to generate the error signal for the frequency control loop. No cryogenics were used. Two almost identical oscillators were constructed to perform classical two-oscillator phase-noise measurements where one oscillator was phase locked to another. The phase locking was implemented by electronically controlling the level of microwave power dissipated in the sapphire dielectric resonator.     

Direct measurement of FM noise in 80 GHz solid-state oscillators

A technique for the measurement of FM noise in W-band oscillators is described. The method is `direct?, since it makes use of a tuned frequency discriminator operating at the fundamental oscillator frequency. The equipment is compared with other types of noise measurement systems, and the important factors affecting sensitivity are noted. Measurements of the FM noise performance of oscillators utilising GaAs TEOs and Si impatts are presented.     

On the noise properties of injection-locked oscillators

This paper presents a detailed study of noise properties of injection-locked oscillators. We describe an elaborate numerical model, which offers the accuracy of the best known analytical models when analyzing a single oscillator. Those analytical models do not use perturbation theory since the Wiener nature of the noise renders small-signal analysis inadequate. Our model can be extended to any locked oscillators configuration while keeping the same accuracy. This was not done to date with any of the rigorous analytical models. We analyze unidirectionally and bidirectionally coupled oscillators operating in fundamental or harmonic-locking modes. Harmonic locking is analyzed in detail and the indirect locking process underlying it is identified while the noise of all harmonics is explored in detail. The results of the model are confirmed in a series of experiments employing electrooptic implementations with a photo-HBT-based oscillator. The various configurations we analyze and demonstrate experimentally represent important applications such as spectral purity enhancement, timing extraction, and low-jitter optical pulse generation.     

Voltage-controlled crystal oscillators

The quartz crystal oscillator is normally thought of as a stable generator of a fixed frequency. It is possible, however, to design and construct voltage tunable quartz crystal oscillators that can be electrically tuned over a frequency range on the order of ±0.3 percent of the crystal frequency. This is accomplished with a nonlinearity between frequency and voltage on the order of 0.1 percent. Moderately good long-term frequency stability and low phase noise is exhibited by the oscillators. A reactive network including varactor diodes is used to provide a voltage variable reactance which, in combination with a quartz crystal network, forms a resonator having an antiresonant frequency that is a linear function of tuning voltage. The basic reactance network is not practically realizable. However, the application of one of Norton's network transformation theorems results in a realizable network. The oscillator described is very simple in design and provides an inexpensive solution to a large number of signal processing and measurement problems.     

Analysis of MESFET injection-locked oscillators in fundamental modeof operation

In this paper, nonlinear analyses of MESFET oscillator in free-running and injection-locked states are studied based on the Volterra series method and stability analysis. The approach shown is capable of quantitatively analyzing the injection locking performance of oscillator using three-terminal devices in the fundamental mode of operation. Both the transmission-type and reflection-type injection locked oscillators (ILO) are simulated and experimentally verified     

Injection locking of oscillators

An oscillator can be locked in frequency by an external signal which is injected into the oscillator. In the oscillator model developed by Adler [1], the mechanism of the locking process depends upon the following. 1) The initial frequency difference between the oscillator and external signals. 2) The relative amplitude between the injected and the oscillator signals. 3) The circuit parameters. There are cases when the time required for locking must be known, particularly when an oscillator is being locked to a pulsed signal. In this paper, the work of Adler is extended to develop an equation which is useful for higher levels of locking signal, a case often encountered when an oscillator is being injection locked by a pulsed signal. Because the solution of this equation is unwieldy and difficult to understand intuitively, except in very special cases, curves describing the locking mechanism were obtained using a digital computer. These curves enable a designer to construct oscillators which will provide a desired performance. The curves were checked experimentally and showed a close agreement between predicted and measured results. The experimental data indicates that the theory describes the locking time remarkably well even at high levels of locking signal.     

Optical synchronization of millimeter-wave oscillators fordistributed architecture

A review of various methods of phase and frequency synchronization of active MMIC based transmit/receive modules is presented, and particular emphasis is placed on the synchronization of oscillators through the use of an indirect subharmonic optical injection locking technique. In this approach, the nonlinear behavior of large-signal modulated laser diodes and solid-state oscillators is exploited to extend the bandwidth of the synchronizing link to the millimeter-wave frequency range. Experimental results of the phase and frequency coherency of two 21.5 GHz FET oscillators are reported. Optimum performance is achieved at a subharmonic factor of 1/4, with a locking range of 84 MHz and a phase noise degradation of only 14 dB. The phase coherency measurement of two injection-locked oscillators points to a phase shift, which is introduced as a result of the frequency detuning between the slave and master oscillator signals. A scheme to correct for this phase error is presented     

A low phase noise PLL using Vackar VCO and a wide-locking range tunable divider for V-band signal generation in 65-nm CMOS

This paper presents a low phase noise integer-N phase-locked loop (PLL) for V-band signal generation. To enhance the frequency stability, we use a new class of Vackar voltage-controlled oscillator (VCO) in the PLL. The Vackar VCO achieves a low phase noise performance by effectively suppressing the AM-PM conversion. To properly align the locking range with the output of the VCO, a divider with wide locking range is realized by the current-mode logic (CML) D-flip-flops with tunable load. For spur reduction, an enhanced charge-pump structure is used to reject transient current glitches. With good static and dynamic current matching achieved in the charge pump, the reference spur is suppressed down to ?50 dBc. The designed PLL is implemented in a 65 nm RFCMOS process, and the measurement demonstrates a low phase noise signal up to 17 GHz. The in-band phase noise (at 1 MHz offset) and out-band phase noise (at 50 MHz offset) are ?103.6 and ?126.8 dBc/Hz, respectively. The PLL consumes 50.7 mW and occupies a chip area of 0.9 mm².     

Low-noise phase lock of high spectral purity 100 MHz VCXO to a highstability 10 MHz reference oscillator

A low-noise phase-locked loop based on a digital frequency divider is presented. This PLL is used to phase lock a 100 MHz VCXO to a high stability 10 MHz reference oscillator. The measured residual phase noise of the dividers and of the locked VCXO are reported     

一种基于偏移源的频率合成技术分析

针对一种基于偏移源的频率合成技术,建立了锁相环(PLL)线性模型,对相位噪声和杂散信号性能进行分析。从分析结果看,在锁相环反馈支路中使用一个偏移源将压控振荡器(VCO)输出信号下混频至一个较低的中频,从而将锁相环的环路分频比大大降低,使改善后的锁相环噪底达到-135 dBc/Hz。介绍了偏移源和主环的关键合成技术,结合工程应用设计的基于偏移源的C频段频率合成器,相位噪声偏离载波10 kHz处≤-99 dBc/Hz,偏离载波100 kHz处≤-116 dBc/Hz,杂散小于-70 dBc。     

低相位噪声微波振荡器设计

针对Ka和Ku波段上、下变频装置对微波振荡器低相位噪声和小型化的要求,该文采用单环锁相式频率合成技术完成了微波振荡器的设计,并对锁相环的相位噪声进行了理论计算。分析了鉴相频率、鉴相器灵敏度和环路带宽对锁相环输出相位噪声的影响,根据分析结果对微波振荡器电路参数合理选择,同时兼顾了低相位噪声与小型化的设计要求。测试结果表明,振荡器的相位噪声指标与理论计算一致,各项指标均达到要求,可满足实际工程应用。     

Jitter in ring oscillators

Jitter in ring oscillators is theoretically described, and predictions are experimentally verified. A design procedure is developed in the context of time domain measures of oscillator jitter in a phase-locked loop (PLL). A major contribution is the identification of a design figure of merit κ, which is independent of the number of stages in the ring. This figure of merit is used to relate fundamental circuit-level noise sources (such as thermal and shot noise) to system-level jitter performance. The procedure is applied to a ring oscillator composed of bipolar differential pair delay stages. The theoretical predictions are tested on 155 and 622 MHz clock-recovery PLL's which have been fabricated in a dielectrically isolated, complementary bipolar process. The measured closed-loop jitter is within 10% of the design procedure prediction     

A study of injection locking and pulling in oscillators

Injection locking characteristics of oscillators are derived and a graphical analysis is presented that describes injection pulling in time and frequency domains. An identity obtained from phase and envelope equations is used to express the requisite oscillator nonlinearity and interpret phase noise reduction. The behavior of phase-locked oscillators under injection pulling is also formulated.