A cost-effective technique for extending the low-frequency range ofa microwave noise parameter test set

The operating frequency range of an on-wafer noise parameter test set based on the multiple-impedance technique has been extended in the low-microwave frequency range (down to the L-band). A simple technique, using a phase shifter cascaded with the microwave tuner, allows different reflection coefficients of the load impedance to be obtained at the device input. These coefficients are well distributed over the Smith chart in the entire frequency range. As an example, noise parameters of a passive device have been measured between 1 and 8 GHz, and a good agreement between measured and calculated values is observed. This technique has also been used to measure the noise parameters of different heterojunction bipolar transistors. A minimum noise figure of 1 dB was obtained at 1 GHz on a GaAlAs/GaAs HBT which is in agreement with expected results     

Merits of PM noise measurement over noise figure: a study at microwave frequencies

This paper primarily addresses the usefulness of phase-modulation (PM) noise measurements versus noise figure (NF) measurements in characterizing the merit of an amplifier. The residual broadband (white PM) noise is used as the basis for estimating the NF of an amplifier. We have observed experimentally that many amplifiers show an increase in the broadband noise of 1 to 5 dB as the signal level through the amplifier increases. This effect is linked to input power through the amplifier's nonlinear intermodulation distortion. Consequently, this effect is reduced as linearity is increased. We further conclude that, although NF is sometimes used as a selection criteria for an amplifier for low-level signal, NF yields no information about potentially important close-to-carrier 1/f noise of an amplifier nor broadband noise in the presence of a high-level signal, but a PM noise measurements does. We also have verified experimentally that the single-sideband PM noise floor of an amplifier due to thermal noise is -177 dBc/Hz, relative to a carrier input power of 0 dBm.     

The gain and noise figure of Yb-Er-codoped fiber amplifiers based on the temperature-dependent model

A novel temperature-dependent model for Yb³⁺-Er³⁺-codoped fiber amplifier (EYDFA) based on the energy transfer from Yb³⁺ to Er³⁺ is established. Using appropriate fiber and energy transfer parameters, the coupled rate equations is numerically solved at 25 and 40 °C. The pumping powers are 100 and 200 mW at a pump wavelength of 1060 nm. The signal gain and noise characteristics of a 0.3 m erbium/ytterbium co-doped fiber (EYDF) in a single-pass configuration are investigated by using 1, 10 and 100 μW signals at 1535 nm. A maximum signal gain of 40.5 dB and a corresponding noise figure of 3.65 dB at the temperature of 25 °C are achieved.     

A novel phase noise measurement of phase modulation microwave photonic links

Abstract

Microwave photonic links can provide many advantages over traditional coaxial due to its low loss, small size, lightweight, large bandwidth and immunity to external interference. In this paper, a novel phase noise measurement system is built, since the input signal and the power supply noise can be effectively cancelled by a two-arm configuration without the phase locking. Using this approach, the phase noise performance of the 10-GHz phase modulation photonic link has been measured for the first time, evaluated the values of ?124 dBc/Hz at 1 kHz offset and ?132 dBc/Hz at 10 kHz offset is obtained. Theoretical analysis on the phase noise measurement system calibration is also discussed.     

Permanent magnets for microwave devices

The magnetron, invented in 1939, created the need for a microwave tube magnet which evolved from the early horn magnet to the U magnet, the E magnet, and finally the bowl magnet. A more recent innovation, the self-shielded cylindrical magnet, is now used on many crossed-field amplifiers. The klystron and the traveling wave tube created the need for permanent magnets with gaps longer than their diameters. The field straightener and the periodic permanent magnet facilitated the use of permanent magnets in focusing these linear beam tubes. The operation of magnetrons, crossed field amplifiers, klystrons, traveling wave tubes, and microwave ferrite devices, and the permanent magnets which are used in conjunction with these devices are described. Magnetic circuit design criteria, design methods, and the magnetization and stabilization of permanent magnets are discussed. The requirements of microwave devices have provided much of the incentive for the great advances in permanent magnet materials made in the last decade. The recent development of rare-earth-cobalt powders which exhibit the highest magnetocrystalline anisotropy ever recorded are of great interest to the microwave device designer.     

Characteristics of materials for microwave devices

The characteristics of materials like ferrites, garnets, ferroelectrics temperaturecompensated dielectrics and copper-coated PTFE-based composites, extensively used in microwave devices are discussed.     

A microwave photonic generator of chaotic and noise signals

The transition to chaos in a microwave photonic generator has been experimentally studied for the first time, and the generated broadband chaotic microwave signal has been analyzed. The generator represented a ring circuit with the microwave tract containing a low-pass filter and a microwave amplifier. The optical tract comprised a fiber delay line. The possibility of generating chaotic oscillations with uniform spectral power density in a 3–8 GHz range is demonstrated.     

A novel impedance pattern for fast noise measurements

Complete noise characterization of an active device implies the extraction of the minimum noise figure (F_min), noise resistance (R_n), and optimum value of the complex input reflection coefficient (Γ_opt). Such quantities can be obtained through a minimum of four noise figure measurements, associated to four different reflection coefficients at the input of the DUT, (Γ_in,k k = 1 · · · 4), forming an "impedance pattern." Measurement redundancy is usually required to reduce overall uncertainty, therefore forcing one to use, for the synthesis of a large number of different terminations, an impedance tuner. This paper introduces a novel four-points input pattern, which becomes an "optimum" trade-off between accuracy and complexity, while avoiding the use of a tuner: a drastic reduction in cost and complexity of the measurement bench therefore results     

Analysis of inductive multiport microwave devices employing a novel double parallel plate approach

The authors present a novel surface integral equation approach to analyse inductive microwave devices with several parallel input-output ports containing inductive metallic and dielectric obstacles. The technique decomposes the main problem into three subproblems, employing different kinds of Green's functions. One of the subproblems uses the classical Green's functions of an infinite unbounded medium with the constitutive parameters of the dielectric obstacles. A novel point of the technique is the formulation of the two other subproblems with two different, 90deg rotated parallel plate regions. In these regions the parallel plate waveguide Green's functions are used to simplify the modelling of the excitation problem. The second novel aspect of the work is in the treatment of these Green's functions, to smooth their behaviour, and to improve their convergence. Several numerical results are presented to demonstrate the usefulness of the algorithms proposed. Also, several results for inductive microwave devices are presented to show the practical value of the approach.     

Characterizing ultrasonic transducers using radiation efficiency and reception noise figure

Transducer performance is considered separately for transmission and reception operations. The transmission operation is traditionally characterized by its traditional transfer function. Using a Thevenin source, the transfer function may be scaled to become the absolute radiation efficiency. Transmission lines are accurately modeled, and a matched impedance design is recommended. The reception operation also is characterized by its traditional transfer function. However, reception sensitivity is defined as the signal-to-noise ratio achieved by the combined transducer, transmission line, and preamplifier. The thermal noise arises from the media and other noise sources contributed by the transducer, transmission line, and preamplifier. An absolute sensitivity measure is defined as the acoustic noise figure, which is the sum of individual transducer and preamplifier noise figures. The transducer noise figure is independent of the receiver load impedance and depends critically on dissipative loss. Preamplifier noise figure performance requires noise matching to the transducer. High performance design methods are presented that incorporate transmission lines, which include loss. Modeled examples are used to demonstrate performance.     

Topology optimization of metallic devices for microwave applications

In electromagnetic optimization problems of metallic radio‐frequency devices, such as antennas and resonators for wireless energy transfer, the volumetric distribution of good conductors, e.g. copper, has been known to cause numerical bottlenecks. In finite element analysis the limiting factor is the skin depth, which calls for highly refined meshing in order to capture the physics. The skin depth problem has therefore prohibited the application of topology optimization to this class of problem. We present a design parameterization that remedies these numerical issues, by the interpolation of Maxwell's equations and a fictitious element impedance condition. The validity of the proposed design parameterization is confirmed by several numerical examples. Copyright © 2010 John Wiley & Sons, Ltd.     

一种实现目标定位与跟踪的新方法

本文介绍了一种采用圆周阵对目标声源进行被动定位和跟踪的方法，与线阵不同，圆四可对目标进行全方位跟踪，且测距精度不受目标方位变化的影响，文中给出了圆周阵的测距，测向公式，并从理论上分析了测距性能，计算机仿真结果验证了理论分析的正确性。     

Spectroscopic methods for noise levels in semiconductor materials and devices

Conclusions Theoretical relationships have been derived that associate the characteristics of modulated GR-noise with the parameters of the various kinds of levels located in an SCR. These relationships can be utilized to calculate the modulated GR-noise in a broad class of devices and structures. It has been shown that an essential role may be played in the formation of this noise by the fluctuations that accompany the adherence of current carriers in a narrow region of a SCR. It is revealed that during the flow of large collector currents in transistors or of large photocurrents in photodiodes the role of adherence noise from minority carriers, as well as of recombination noise, is increased. Two different kinds of methods for barrier-noise spectroscopy of the levels are proposed.The materials in the article were presented at the 6th All-Academic School for Standardization and Metrological Problems.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 59–61, March, 1990.     

A study of noise phenomena in microwave components using an advanced noise measurement system

A novel 9 GHz measurement system with thermal noise limited sensitivity has been developed for studying the fluctuations in passive microwave components. The noise floor of the measurement system is flat at offset frequencies above 1 kHz and equal to -193 dBc/Hz. The developed system is capable of measuring the noise in the quietest microwave components in real time. We discuss the results of phase and amplitude noise measurements in precision voltage controlled phase shifters and attenuators. The first reliable experimental evidences regarding the intrinsic flicker phase noise in microwave isolators are also presented.     

Ultra low-noise preamplifier for low-frequency noise measurementsin electron devices

The design and realization of an ultra-low-noise, high-input-impedance amplifier for low-frequency noise measurements in electronic devices is presented. Special care is devoted to the solution of typical problems encountered in the design of low-noise low-frequency equipment, such as power supply noise and temperature fluctuations. The ultra-low-noise preamplifier has a bandwidth of over seven decades with a low-frequency roll-off of 4 mHz. The noise characteristics obtained are sensibly better than those of commercial preamplifiers commonly adopted in low-frequency noise measurements. The application of this preamplifier to the realization of standard 1/f^γ noise generators is presented     

Novel interferometric frequency discriminators for low noise microwave applications

New configurations of interferometric frequency discriminators (FD) for frequency stabilization of microwave oscillators are examined. The new FDs are arranged in single directional (SD) (patented), bidirectional (BD) (patent pending), and dual reflection (DR) (patent pending) configurations. In the SD configuration, the signals reflected off and transmitted through the resonator separately pass through different arms of the interferometer. In the BD configuration, microwaves pass in both directions through each arm of the interferometer. In the DR configuration, microwaves are reflected from the resonator as well as the compensating arm. The FD sensitivity is compared with that for the conventional interferometric FD and found to be 6 dB greater in the BD configuration. Because no circulator is required within the interferometer in either the BD or the DR FD, the discriminator's phase noise floor is not limited by the circulator contribution     

High-throughput microwave synthesis and characterization of NiO nanoplates for supercapacitor devices

In order to produce economically viable supercapacitor devices for electrical energy storage, low cost, and high throughput methods must be developed. We developed a microwave based synthesis for the formation of β-Ni(OH)₂ for the formation of nickel oxide nanoplates. These nanoplates have shown excellent properties as pseudocapacitive devices with high-specific capacitance. Novel to this article is the use of a microwave reactor which enables a growth process of only 10 min in duration as compared to previous reports requiring a 24 h period. The resulting NiO nanoplates were fully characterized by electron microscopy, electron diffraction, energy dispersive X-ray spectroscopy, UV–Vis spectroscopy, thermo gravimetric analysis, and surface area and porosity measurements. Nanoplates formed using the microwave reactor is similar to those formed by hydrothermal processes. NiO-single walled carbon nanotube composites were made without any binder and the specific capacitance was measured using charge discharge techniques.     

Eu–Co substituted Sr-hexaferrites for recording media and microwave devices

Journal of Materials Science: Materials in Electronics - Among ferrites materials, M-type hexaferrites are very important due to their excellent technological applications. In the present...