Photoactivated microwave oscillator

Predicted results and measured data of an original optically switched oscillator realised on GaAs MMIC technology are presented. The photoconductive effect within the semiconductor substrate is exploited to induce, by application of a suitable optical power on a microwave photoconductive switch, the oscillating behaviour of an active device at a frequency of 4.9 GHz. Modulation-intensity effect of an optical signal on free-running frequency and an output power are also analysed. This oscillator could be easily integrated within communication systems to achieve high data rate amplitude and phase modulation of microwave carriers.     

Delay-line-stabilised microwave oscillator

The technique of oscillator stabilisation by a delay line, previously used at h.f., is extended to microwave frequencies. Performance details are given at X-band, showing a stabilisation ratio of about 23 and an improvement in f.m. oscillator stability. The system remains in lock throughout X-band.     

Frequency instability measurement system of cryogenic maser oscillator

The frequency stability measurement of a new kind of secondary frequency standard, the whispering gallery mode maser oscillator, is reported. Based on a very simple design the beatnote comparison with a state-of-the-art cryogenic sapphire resonator oscillator gave a preliminary result of 10^-14 frequency instability at 1 s integration time. The measurement is limited by the microwave synthesis chain used to evaluate the maser stability.     

Quantum effects in cryogenic microwave voltage amplifiers

It is shown that in cryogenic microwave voltage amplifiers the standard definition of the noise figure F can be used and that it leads to the classical result without quantum effects. However, the available output noise power P_av of such an amplifier with available gain G_av is found to be $\text{FkTΔfG}{}_{\mathrm{av}}\text{(}\text{E}\text{kT}\text{)}$, where $\text{E}\text{=}\text{1}\text{2}\text{hf +}\text{hf}\text{[}\text{exp}\text{(}\text{hf}\text{kT}\text{) ? 1]}$ is the average energy of an harmonic oscillator of frequency f at the temperature T and $\text{E}\text{kT}$ is the quantum correction factor for thermal nose and shot noise. A discussion shows that this quantum effect might be measurable at 50–100 GHz and T = 4-2°K.     

Punchthrough oscillator?new microwave solid-state source

The performances of silicon p-n-p punchthrough oscillators have been studied experimentally at X band in a coaxial cavity. A range of mechanical tuning of more than 3 GHz has been obtained. The oscillator performance at current densities up to about 200 A/cm has been related to the measured diode impedance. The wide-active-band, sensitive-electronic-tuning and low-noise properties of the punchthrough oscillator suggest promising applications as a microwave signal source, as a local oscillator, in f.m.-c.w. radar and in a.f.c.     

X-band GaAs MESFET oscillator for cryogenic application at 4.2 K

A stripline X-band oscillator for use in a Josephson potentiometer has been designed and constructed. An oscillator comprising a packaged GaAs MESFET was successfully tested at temperatures of 300 and 4.2 K. The cooling improves the short term stability of the frequency during a period of several minutes by a factor of 10 to 10/sup -6/.<>     

一种应用于MCU的低温漂RC振荡器设计

针对高稳定性MCU的应用需求,设计了一种低温度灵敏度的RC振荡器.采用平均电压反馈电路降低比较器延迟对振荡器输出频率的影响,采用温度补偿技术补偿温度对振荡器输出频率的影响,实现RC振荡器高稳定性输出.设计了一种选频网络,实现宽频率范围内高精度输出,满足MCU对多种时钟频率的需求.RC振荡器基于SMIC 110 nm C...     

一种频率可调低温漂振荡器的设计

设计了一种频率可调,低温漂、结构简单的张弛振荡器。该振荡器利用基准电压和负反馈的钳位作用,通过改变外部电阻的阻值来线性改变振荡周期。利用电容两端电压不能突变的原理,使得每次充放电电容电压跳变后都远离反相器的阈值,这样便忽略阈值对振荡器的影响,并且省去了常规结构中的迟滞比较器,简化了电路结构,减小了振荡器的复位延时。基于0.18μm BCD(Bipolar-CMOS-DMOS)工艺模型,采用Cadence和Hspice进行仿真。在典型应用下,振荡器的频率范围为500 k Hz~2 MHz,温度在–20~+120℃变化时,振荡器的频率随温度变化的偏移量在±2.76%以内。     

RADIATION FROM THE CRYOGENIC CALIBRATION LOAD FOR MICROWAVE RADIOMETERS

A styrofoam layer is introduced to the cryogenic calibration load for microwave radiometers in order to keep the antenna at ambient temperature while calibrating. Obviously the insulation layer has nonuniform temperature profile. A novel approach based on the transmission-line theory is presented to calculate the emission from the load. According to the sample calculation through this new approach, the contribution of the insulation layer to the load radiation can not be neglected.     

Stabilizing an optoelectronic microwave oscillator with photonic filters

This paper compares methods of active stabilization of an optoelectronic microwave oscillator (OEO) based on insertion of a source of optical group delay into an OEO loop. The performance of an OEO stabilized with either a high-Q optical cavity or an atomic cell is analyzed. We show that the elements play a role of narrow-band microwave filters improving an OEO stability. An atomic cell also allows for locking the oscillation frequency to particular atomic clock transitions. This reports a proof-of-principle experiment on an OEO stabilization using the effect of electromagnetically induced transparency in a hot rubidium atomic vapor cell.     

Ultra-low power PSK backscatter modulator for UHF and microwave RFID transponders

An integrated circuit implementation of a PSK backscatter modulator for passive radio frequency identification (RFID) transponders is proposed. Such modulator offers a significant reduction of the power consumption with respect to other schemes already presented in the literature. Furthermore, the topology of the proposed modulator allows us to control its output resistance so that only a negligible fraction of the active power at the antenna goes to the modulator.     

Nonlinear behavior of the BARITT diode microwave oscillator

Nonlinear behavior of the free-running BARITT diode oscillator has been observed. Discontinuous changes in oscillation frequency and output power occur as the bias current changes. These non-linearities have been investigated in coaxial and waveguide oscillators and are caused by device and circuit interactions.     

Simple architecture low phase noise microwave cryogenic sapphire oscillators

The operation of a low phase noise 10.35 GHz microwave cryogenic sapphire resonator oscillator is demonstrated. Based on a very simple architecture, the oscillator presents phase noise performances of -104 dBrad²/Hz at f=10 Hz off the carrier (slope 1/f ³), lower than -152 dBrad²/Hz at f=1 kHz (slope 1/f), and of -160 dBrad²/Hz at fgsim10 kHz (white)     

Phase noise in cryogenic microwave HEMT and MESFET oscillators

The influence of cooling on the phase noise of HEMT and MESFET oscillators is addressed. The initial measurements of the device DC characteristics and low-frequency noise (0.1 kHZ-100 kHz) under cooling give indications on the suitability of a given device for use in low-phase-noise cooled oscillators. Cooled pseudomorphic AlGaAs-GaInAs-GaAs HEMTs (PHEMTs) turn out to be particularly well-suited as they are free of collapse and they are free of g-r noise in the frequency range of interest. The authors report on 4 GHz oscillators operated at 110 K and featuring a phase noise below -100 dBc/Hz at 10 kHz from the carrier in spite of a very modest loaded Q (160). It is suggested that high-temperature-superconductor resonators could greatly enhance the spectral purity of PHEMT oscillators     

Low cost microwave oscillator using substrate integrated waveguide cavity

A topology is proposed for designing a low-cost microwave oscillator. This new feedback oscillator makes use of a substrate integrated waveguide (SIW) cavity that acts as a frequency selector as well as a feedback-coupling device. The oscillator is stabilized by using an injection-locking scheme. A 12.02-GHz oscillator prototype was designed. Experimental results for phase noise, locking range, and quality factor of the new circuit are presented. An external Q of 178 was measured.     

基于光电振荡器的光脉冲和电微波信号发生器

设计了一种基于相位调制器的用于产生光脉冲和电微波信号的光电振荡器。该方案采用直调激光器配合相位调制器产生大啁啾并由DCF压窄输出光脉冲。利用偏振分束器和合束器在不增加有源器件的基础上形成双环路结构抑制微波信号的边模。该系统可以产生9.8 GHz的重复频率,脉宽小于 12 ps的光脉冲同时输出该频率的电微波信号。测得相位噪声为-105 dBc/Hz@10 kHz,Q值大于10¹⁰。     

光电振荡器的原理及其实验研究

光电振荡器应用了光电混合的技术手段,通过光纤储能和延迟的方法可实现频率精度、稳定度、相位噪声都显著优于常规微波介质振荡器的一种新型振荡源.简要介绍了光电振荡器的基本原理和研究现状,并应用内调制激光器和长光纤环结构进行了实验研究,得到了相位噪声优于-112 dBc/Hz@10 kHz、线宽＜1 Hz的高性能微波信号输出.     

Al0.3Ga0.7As-GaAs microwave resonant tunneling oscillator

We describe the design of a microwave oscillator using resonant tunneling diodes. The devices are fabricated from Al_0.3Ga_0.7As-GaAs double barrier hetero-structures grown by molecular beam epitaxy. Design criteria improving current drivability are established from a theoretical study of tunneling transmission probabilities. Very high peak current densities up to 3.10⁴ A/cm², favorable for high frequency operation as an oscillator, have been achieved experimentally. The devices exhibit stable oscillations at liquid nitrogen temperature and at room temperature when the tunnel diode oscillator is constructed with a stabilizing network.     

A figure of merit for a varactor-tuned microwave oscillator

This note derives a figure of merit for a varactor tuned microwave solid state oscillator. Thu figure of merit is in terms of electronic tuning range and power output normalized to the available power from the untuned oscillator. This enables the varactor which will give the required combination of thorns parameters to be specified in terms of y and f _c.

The figure of merit also shows that a varactor with a large value of the product yf _c maximizes the figure of merit.     

Magnetic frequency tuning of the microwave Gunn diode oscillator

It has been found experimentally that the oscillation frequency of a Gunn diode placed in the low-dimensional resonance system “metal pin-closely set short-circuiter” can be effectively controlled by magnetic field applied in the normal direction with respect to the waveguide wide wall.