Compensation of the phase flicker noise in a bipolar-transistor power amplifier

Relationships between the parameters of a bipolar-transistor (BT) common-base power amplifier, which provide compensation of the flicker component of the phase noise of the output signal during operation in the linear mode, are obtained. This effect is revealed in the microwave frequency band by means of numerical simulation. It is shown that after introduction of nonlinear parameters in the BT equivalent circuit, the effect persists in some vicinity of the compensation point calculated for the linear case.     

Pumped Schottky diodes with noise temperatures of less than 100 K at 115 GHz

New Schottky-barrier diodes, with an epitaxial layer thickness of < 1000 ? and doping 2.5×1016 cm?3, yield a mixer noise temperature of 98 K at 115 GHz. The diodes have a diameter of 1.8 ?m, and show repeatable performance. Measurements indicate negligible capacitance variation to at least +0.2 V. The noise temperature is competitive with values reported for Josephson and quasiparticle junctions.     

Flicker noise in GaAs MESFET X-band amplifiers in the temperature range 300 K to 2 K

We report measurements of the noise temperature of small-signal, low-noise X-band GaAs MESFET amplifiers from room temperature down to 2 K, at offset frequencies of several hundred hertz from the carrier and for input carrier powers from -40 to -20dBm. We observe a dramatic increase in the level of flicker noise as these devices are cooled to liquid helium temperatures, in marked contrast to the normally observed decrease in noise temperature of an unsaturated GaAs MESFET amplifier as it is cooled.     

Precision measurement method for cryogenic amplifier noise temperatures below 5 K

We report precision measurements of the effective input noise temperature of a cryogenic (liquid-helium temperature) monolithic-microwave integrated-circuit amplifier at the amplifier reference planes within the cryostat. A method is given for characterizing and removing the effect of the transmission lines between the amplifier reference planes and the input and output connectors of the cryostat. In conjunction with careful noise measurements, this method enables us to measure amplifier noise temperatures below 5 K with an uncertainty of 0.3 K. The particular amplifier that was measured exhibits a noise temperature below 5.5 K from 1 to 11 GHz, attaining a minimum value of 2.3 K/spl plusmn/0.3 K at 7 GHz. This corresponds to a noise figure of 0.034 dB/spl plusmn/0.004 dB. The measured amplifier gain is between 33.4 dB/spl plusmn/0.3 dB and 35.8 dB/spl plusmn/0.3 dB over the 1-12-GHz range.     

Quasi-optical measurement of carcinotron phase noise at 350 GHz

Phase noise of a single carcinotron operating at 350 GHz, at offset frequencies in the range 10⁵-10⁷ Hz, from the carrier has been measured. A quasi-optical analogue of the delay line frequency discriminator method was used, demonstrating a simple method capable of measuring phase noise in the (sub)mm region. The results obtained are of practical use in the design of phase locked systems, in the wavelength region used     

A study of flicker noise in MOS transistors operated at room and liquid helium temperatures

A study of flicker noise in MOS transistors operated in the linear and non linear regions at room and liquid helium temperatures is proposed. Besides, a theoretical analysis of the drain current noise characteristics is developed in the framework of the mobility fluctuation model as well as of the carrier number fluctuation model. It is shown experimentally that a close correlation between the drain current spectral density and the transconductance squared dependencies with gate voltage (or drain current) and drain voltage is observed in our devices both at room and liquid helium temperatures. Therefore, it is concluded that the carrier number fluctuation model is not only applicable to MOS devices operated at room temperature but also at liquid helium temperature in ohmic and non ohmic regimes. In addition, peculiarities of the drain current noise related to the appearance of a kink effect at liquid helium temperature in the saturation current characteristics are also discussed.     

Linearization technique using bipolar transistor at 5 GHz low noise amplifier

A CMOS low noise amplifier (LNA) used in wireless communication systems, such as WLAN and CDMA, must have low noise figure, high linearity, and sufficient gain. Several techniques have been proposed to improve the linearity of CMOS LNA circuits. The proposed low noise amplifier achieves high third-order input intercept point (IIP3) using multi-gated configuration technique, by using two transistors, the first is the main CMOS transistor, and the second is bipolar transistor in TSMC 0.18 m technology. Bipolar transistor is used to cancel the third-order component from MOS transistor to fulfill high linearity operation. This work is designed and fabricated in TSMC 0.18 m CMOS process. At 5 GHz, the proposed LNA achieves a measurement results as 16 dBm of IIP3, 10.5 dB of gain, 2.1 dB of noise figure, and 8 mW of power consumption.     

Noise properties of HTS Josephson mixers at 345 GHz and operating temperatures at 20 K

The authors report on the mixing properties of high-temperature superconductor bicrystal Josephson junctions at 345 GHz and high-operating temperatures. A variable backshort and E-plane tuner enabled the control of impedance matching between the junction and the RF environment. The local oscillator frequency and intermediate frequency were 345 and 1.4 GHz, respectively. The double-side band (DSB) mixer noise temperature and the conversion efficiency were determined using the hot/cold method. The authors observed that the noise temperature was strongly dependent on the matching conditions. The lowest noise temperatures were observed for tuner positions supporting the formation of a subharmonic step which appeared between the zeroth and first Shapiro step. At T = 20 K they obtained a lowest DSB mixer noise temperature of 1003 K and a conversion efficiency of -1.2 dB. They have investigated the dependence of the noise temperature on the operating temperature in detail. The impact of resonances on the device performance will be discussed.     

Measurement of the impulsive noise environment for satellite-mobileradio systems at 1.5 GHz

Noise amplitude distribution measurements relevant to satellite-mobile radio systems are reported. The rationale for the measurements is outlined and the choice of measurement parameters justified. The measurement equipment and measurement methodology are described in detail. Results characterizing the elevation angle distribution of impulsive noise are presented for rural, suburban and urban environments and also for an arterial road (U.K. motorway) carrying high density, fast moving traffic. Measurements of the levels of impulsive noise to be expected in each environment for high- and low-elevation satellite scenarios using appropriate antenna configurations are also presented     

Polarization of microwave noise source radiation in the 30 GHz to 300 GHz range

The radiation spectra of three microwave noise sources (C. P. Clare & Co., TN type series) have been compared to determine the frequency bandwidth and their polarization. A Lamellar Grating Fourier Transform spectrometer was used with a Helium cooled bolometer detector in the wavelength region of lmm to 10mm. The spectral regions were compared with the manufacturer's specifications and the results were in partial agreement. A secondary transmission region was observed to have an input current as well as a polarization dependence despite the directional output of the waveguide antenna.     

Design of on-chip 15-18 GHz ultra low noise amplifier

With rapid development communication system, high signal to noise ratio （SNR） system is required. In high frequency bandwidth, high loss, low Q inductors and high noise figure is a significant challenge with on-chip monolithic microwave integrated circuits （MMICs）. To overcome this problem, high Q, low loss transmission line characteristics was analyzed. Compared with the same inductor value of the lumped component and the transmission line, it has a higher Q value and lower loss performance in high frequency, and a 2-stage common-source low noise amplifier （LNA） was presented, which employs source inductor feedback technology and high Q low loss transmission line matching network technique with over 17.6 dB small signal gain and 1.1 dB noise figure in 15 GHz-18 GHz. The LNA was fabricated by WIN semiconductors company 0.15 μm gallium arsenide （GaAs） P high electron mobility transistor （P-HEMT） process. The total Current is 15 mA, while the DC power consumption is only 45 mW.     

Retrieval of crop biomass and soil moisture from measured 1.4 and 10.65 GHz brightness temperatures

Physically based land surface process/radiobrightness (LSP/R) models may characterize well the relationship between radiometric signatures and surface parameters. They can be used to develop and improve the means of sensing surface parameters by microwave radiometry. However, due to a lack in the skill to properly understand the behavior of the data, a statistical approach is often adopted. In this paper, we present the retrieval of wheat plant water content (PWC) and soil moisture content (SMC) profiles from the measured H-polarized and V-polarized brightness temperatures at 1.4 (L-band), and 10.65 (X-band) GHz by an error propagation learning back propagation (EPLBP) neural network. The PWC is defined as the total water content in the vegetation. The brightness temperatures were taken by the PORTOS radiometer over wheat fields through three month growth cycles in 1993 (PORTOS-93) and 1996 (PORTOS-96). Note that, through the neural network, there is no requirement of ancillary information on the complex surface parameters such as vegetation biomass, surface temperature, and surface roughness, etc. During both field campaigns, the L-band radiometer was used to measure brightness temperatures at incident angles from 0 to 50/spl deg/ at L-band and at an incident angle of 50/spl deg/ at X-band. The SMC profiles were measured to the depths of 10 cm in 1993 and 5 cm in 1996. The wheat was sampled approximately once a week in 1993 and 1996 to obtain its dry and wet biomass (i.e., PWC). The EPLBP neural network was trained with observations randomly chosen from the PORTOS-93 data, and evaluated by the remaining data from the same set. The trained neural network is further evaluated with the PORTOS-96 data.     

1.2～1.4 GHz 300 W宽带硅大功率双极晶体管研制

介绍了L波段300 W宽带硅微波脉冲大功率晶体管研制结果。采用大面积亚微米精细线条阵列加工技术、深亚微米浅结制备工艺技术、均匀热分布技术、双层金属化技术等工艺技术,研制出了L波段300 W宽带硅微波脉冲大功率晶体管。器件在1.2~1.4 GHz频带内,脉冲宽度150μs,占空比10%,工作电压40 V条件下,全频带内输出功率大于300 W,功率增益大于8.75 dB,集电极效率大于55%,并具有良好的可靠性。     

Diurnal dynamics of soil brightness temperatures observed at frequencies of 1.4 and 6.9 GHz in the processes of freezing and thawing

The results of experimental investigation and simulation of the diurnal dynamics of soil brightness temperatures at frequencies of 1.4 and 6.9 GHz at a nadir angle of 45° in cyclic processes of freezing and thawing are presented. By the remote radiometric method, the thickness of the freezing layer have been determined, and the effects of nonnisothermal moisture transfer in the surface soil layers have been discovered. It is found that the thickness of the transition layer, which is located between the frozen layer and the underlying soil, increases as the depth of freezing increases. It is shown that the hydrophysical characteristics of soils can be studied by the remote radiometric method.     

High-field autocovariance coefficient,diffusion coefficient and noise in InGaAs at 300 K

Electron diffusivity in In_(0.53)Ga_(0.47)As is calculated by the Monte-Carlo method. The auto-covariance coefficient and correlation time of velocity fluctuations, frequency dependence of diffusion coefficient and figure of merit for noise are studied. The results indicate that the limiting frequency of operation and noise in In_(0.53)Ga_(0.47)As Gunn diodes would be comparable to those of GaAs diodes.     

60 GHz与300 GHz频段航天器舱内通信信道特性

太赫兹(THz)技术有望在航天器舱体轻质化和舱内高容量传输需求方面发挥重要作用.本文构建了典型航天器舱内毫米波60 GHz与太赫兹300 GHz频段信道三维仿真模型,基于射线追踪法获取了两种典型发射机部署位置下的无线信道特性,提取并分析了路径损耗指数、阴影衰落因子、莱斯K因子、均方根时延扩展和角度扩展等关键信道参数,研究了发射机的部署位置对特定频段舱内信道的影响.结果表明：相同环境下,频率越高、路径损耗与莱斯K因子越大而时延扩展越小;相同频率下,发射机部署于舱内角落的信道特性优于部署于舱内上壁中央.本文所研究的无线信道特性将为未来复杂舱内环境下的太赫兹通信系统设计和部署提供启示.     

1.5GHz BiCMOS级间电感匹配低噪声放大器设计

在一个无线接收系统中，为了获得良好的总体系统性能，需要一个性能优越的前端，而低噪声放大器（LNA）就是前端的一个重要组成部分。     

A two-beam interferometer for dispersive reflection spectroscopy of solids in the far infrared at temperatures between 4 and 300K

A Fourier spectrometer has been developed for determining the optical constants of highly absorbing solids in the far infrared at temperatures down to 4.2K from measurements of their amplitude and phase reflection spectra. The spectrometer has been constructed almost entirely from commercially available components, and its performance is illustrated with measurements of the optical constants of NaCl at 6K.     

Hot electron noise in n-channel JFETs between 150 and 300°K

The noise parameter $\text{α}{}_{\mathrm{T}}\text{=}\text{S}{}_{\mathrm{I}}\text{(?)}\text{(4kTg}{}_{\mathrm{m}}\text{)}$ of n-channel JFETs was measured as a function of the voltage V_GS?V_P with the temperature T as a parameter between 150 and 300°K. It was found that α_T could be approximated by the formula $\text{α}{}_{\mathrm{T}}\text{? (}\text{300}\text{T}\text{)α}{}_{300}$, indicating the presence of hot electron effects.     

Hybrid Integrated Frequency Multipliers at 300 and 450 GHz

300- and 450-GHz band doublers and triplers using thin-film integrated circuits have been developed. The multipliers are built with a GaAs honeycomb-type Schottky barrier diode designed to have a high cutoff frequency and transitions from microstrip to rectangular waveguides. A 450-GHz band tripler delivered an output power of -11.2 dBm with a corresponding conversion loss of 19.4 dB. The output power of the 300-GHz band doubler was -3.6 dBm, and its minimum conversion loss was 10.7dB. The hybrid integrated frequency multipliers are useful as solid-state sources in the short-millimeter-wave and subrnillimeter-wave regions.