X波段介质振荡器的设计与仿真

主要介绍了介质振荡器的设计理论,以及使用Agilent公司的ADS仿真软件进行X波段介质振荡器的设计和仿真。在设计过程中使用NEC公司的MESFET管NE71084作为振荡器的有源器件,利用介质谐振器实现了输出信号的稳频与反馈。给出仿真结果和输出信号相位噪声与功率的实际测试结果。测试结果表明,该方法可以有效地指导介质振荡器的设计过程,提高设计效率。     

X波段介质谐振器振荡器和缓冲放大器的研究

微波振荡器代表所有基本微波通信系统的能源来源。研究设计8．95GHz的低噪声砷化镓场效应管并联反馈介质谐振器振荡器,为了放大输出功率和提高负载牵引,在介质谐振器振荡器后一级加缓冲放大器,最终的输出功率是＋13．33dBm。测试证明输出信号的相位噪声偏离中心频率100kHz可达-116．49dBc／Hz,偏离中心频率10kHz可达-91．74dBc／Hz。     

Dielectric measurements in the X-band of mamma tissue from cattle

Dielectric measurements of mamma tissue from cattle were carried out by inserting it in the X-band waveguide. Comparing the experimentally obtained values of the attenuation constants in mamma, muscle and fat, the muscle content in mamma was determined.     

International intercomparison of horn gain at X-band

An international intercomparison of horn gain and polarization measurements at X-band has previously been completed. There were seven participating laboratories with the National Institute of Standards and Technology serving as the pilot laboratory. Two X-band pyramidal standard gain horns with a nominal gain of 22 dB served as the traveling standards. Quantities measured included on-axis fixed frequency gain at 8, 10, and 12 GHz, swept frequency gain between 8-12 GHz and polarization characteristics at the three fixed frequencies. All laboratories performed the fixed frequency-gain measurements. The swept-frequency and polarization measurements were optional, with four laboratories performing swept-frequency measurements and three laboratories measuring polarization. The results of the gain measurements generally agreed within the reported uncertainties which were of the order of 0.1 dB or less     

Modulation of room-temperature GaAs lasers at X-band frequencies

GaAs lasers operating at room temperature are directly modulated at X-band frequencies. A fast silicon avalanche photodiode is used to demodulate the laser light.     

X波段发卡型及其改进型宽带微带带通滤波器

采用发卡型及其改进型结构,在X波段设计了一组宽频带微带带通滤波器。发卡型结构是由二分之一波长的谐振单元变化为"U"结构而来,发卡改进型结构则是将发卡型的"U"结构拉直演变而来,其增加了电容缝隙耦合及开路支节数。仿真结果表明:该组滤波器绝对带宽为1.8GHz,带内损耗低于1.1dB,偏离中心频率-2.5GHz和+2.5GHz处,带外抑制分别大于30dB和48dB。采用理论分析与软件仿真相结合的方法,研究了两种滤波器的开路支节长度与中心频率的关系以及耦合间距对带宽的影响。实测数据与仿真结果一致性较好,验证了该设计的正确性。     

Modeling nonlinear distortion of ultra wideband signals at X-band

Nonlinear distortion in the adjacent channels of an X-band amplifier driven by an ultra-wideband digitally-modulated carrier is analyzed. Statistical properties of the input signal with a complex power series-based behavioral model of the amplifier are used to calculate the output power spectrum. Comparisons are made between measured and predicted adjacent channel power rejection for the X-band monolithic microwave integrated circuit.     

Design and performance of a new digital phase shifter at X-band

A new digital phase shifter design at X-band is presented. The phase shifter operates based on converting a microstrip line to a rectangular waveguide and thus achieving the phase shift by changing the wave propagation constant through the medium. As a proof of principle, a 3-b phase shifter has been designed and constructed using PIN diode switches. An average insertion loss of 1.95 dB and phase shift error of less than 4/spl deg/ at 10.6 GHz are achieved.     

X波段伪码调相连续波雷达地杂波分布特性仿真与分析

本文首先论述了伪码调相连续波雷达的特殊性,然后分析了一些典型地物杂波的统计特性,在此基础上,针对伪码调相连续波雷达在低俯视角情形时回波信号展宽的问题,提出了对码元回波幅度进行空间矢量迭加以得到实际回波信号的方法,通过计算机模拟,得到了迭加时实际回波的概率密度分布模型。     

Easy and accurate method for the characterisation of dielectric materials at X-band

A method of characterising dielectric materials at microwave frequencies is described. The technique overcomes the problem of airgaps in the commonly used `filled-cavity? technique. Results of measurements of the permittivity/temperature characteristics of both quartz and a titanium loaded composite dielectric with a negative slope are presented. The accuracy of the technique is described and a high degree of repeatability demonstrated.     

Comparison of radio transmission at X-band frequencies in suburban and urban areas

Measurements were made at a frequency of 11.2 GHz of the signal strength received by a fixed-base station from a mobile transmitter. Distributions of the instantaneous and rms signal levels are compared for data taken in New York City and suburban New Providence, N. J.     

X波段阶梯阻抗微带带通滤波器设计

设计了一款X波段的多模带通滤波器,并给出了仿真与实验结果。采用恒定阻抗枝节加载3个阶梯阻抗枝节的方式,构成滤波器的主体;利用表面电流分布图获得影响带内极点分布的枝节参数,通过调整阶梯阻抗枝节参数优化滤波性能。为实现更好的带外抑制能力,滤波器两端各串联一对平行耦合线,在14 GHz引入一个传输零点。实验测试结果显示,所设计滤波器的中心频率为9.76 GHz,带宽为2.4 GHz,30 dB/3 dB矩形系数为1.63,相对带宽为25%,带内插入损耗大部分小于1 dB,大部分回波损耗高于15 dB,与仿真结果较为吻合。     

High-power pulsed and c.w. silicon double-drift IMPATT amplifiers at X-band

The letter presents some reflection-amplifier results for Si double-drift pulsed and c.w. IMPATTs. Peak r.f. powers of up to 11.6 and 16.5 W with instantaneous (?1 dB) bandwidths ~20% at gains >6 dB have been obtained at 10 GHz with 1- and 2-diode combinations when bias modulated with a pulsewidth of 4 ?s and p.r.f. of 1 kHz. A 2-diode c.w. combination has given a power of 7 W (c.w.) at 10.7 GHz with a gain of 6.5 dB and instantaneous (?1 dB) bandwidth of 400 MHz.     

Some propagation experiments relating foliage loss and diffraction loss at X-band and UHF frequencies

Measurements of signal attenuation were made from a suburban hilltop base station to a mobile vehicle on several streets in the surrounding countryside. Measurements of signal strength were simultaneously made in the winter of 1971 at frequencies of 836 MHz and 11.2 GHz and then repeated in the summer to determine the effects of foliage. The presence of foliage reduced the received signal strength and the effect was more pronounced at X-band than at UHF. In cases where the shadowing obstacle was tree covered, signal levels at UHF might typically be 10 dB lower when the trees were in full leaf, whereas at X-band this additional loss could be as high as 20 dB. The experimental data was compared to values predicted by knife-edge diffraction and reasonable agreement was found.     

A broadband microwave radiometer technique at X-band for rain and drop size distribution estimation

Radiometric brightness temperatures below about 12 GHz provide accurate estimates of path attenuation through precipitation and cloud water. Multiple brightness temperature measurements at X-band frequencies can be used to estimate rainfall rate and parameters of the drop size distribution once correction for cloud water attenuation is made. Employing a stratiform storm model, calculations of the brightness temperatures at 9.5, 10, and 12 GHz are used to simulate estimates of path-averaged median mass diameter, number concentration, and rainfall rate. The results indicate that reasonably accurate estimates of rainfall rate and information on the drop size distribution can be derived over ocean under low to moderate wind speed conditions.     

Recent advances in device processing and packaging of high-power pulsed GaAs double-drift IMPATT's at X-band

High-power multimesa GaAs hybrid double-drift IMPATT's have been developed for pulsed operation at X-band. The diodes are fabricated from GaAs material grown by a novel "infinite" solution liquid phase epitaxial process. The use of specialized rapid thermal processing and packaging techniques has enabled the fabrication of high-power IMPATT oscillators that have delivered peak output powers of over 40 W with 20-percent efficiency under pulsed RF operation at X-band frequencies. The diodes are constructed with an integral heat sink and bounded with a Au-Sn eutectic solder in a microwave package.     

Optical and Dielectric Properties of Chalcogenide Glasses at Terahertz Frequencies

Terahertz time‐domain spectroscopy has been used to study the optical and dielectric properties of three chalcogenide glasses: Ge₃₀As₈Ga₂Se₆₀, Ge₃₅Ga₅Se₆₀, and Ge₁₀As₂₀S₇₀. The absorption coefficients α(ν), complex refractive index n(ν), and complex dielectric constants ?(ν) were measured in a frequency range from 0.3 THz to 1.5 THz. The measured real refractive indices were fitted using a Sellmeier equation. The results show that the Sellmeier equation fits well with the data throughout the frequency range and imply that the phonon modes of glasses vary with the glass compositions. The theory of far‐infrared absorption in amorphous materials is used to analyze the results and to understand the differences in THz absorption among the sample glasses.     

Dielectric Properties of Yttria Ceramics at High Temperature

Based on Clausius-Mosotti equation and Debye relaxation theory, the dielectric model of yttria ceramics was developed according to the dielectric loss mechanism. The dielectric properties of yttria ceramics were predicted at high temperature. The temperature dependence and frequency dependence of dielectric constant and dielectric loss were discussed, respectively. As the result, the data calculated by theoretical dielectric model are in agreement with experimental data.     

Measurement of Small Dielectric Losses in Material with a Large Dielectric Constant at Microwave Frequencies

A method is described for measuring dielectric losses at microwave frequencies in materials with a large dielectric constant. By observing a dielectric resonance in a sufficiently large sample, the loss tangent of the material can be obtained. Results on SrTiO/sub 3/, single crystals at 20 kMc are presented.     

X频段信标机的设计与实现

为满足船载X频段测控设备信道相位修正和伺服性能检查的需要,设计并研制了一款X频段信标机.首先,选用HMC765 LP6 CE芯片,利用频率合成技术设计了信源并通过通用串行总线(USB)实现了发射频率用户自定义;其次,针对安装平台面积小的限制,基于高频结构仿真器(HF-SS)设计了高次模微带天线并完成了仿真分析和指标优化;最后,完成了X频段信标机的工程实现并给出了硬件电路结构和软件程序设计方法.经测试,该信标机锁相效果良好,控制简便,性能可靠,满足用户使用要求.