高阶耦合模倒圆锥双重正弦同轴结构频率响应

为了形成带宽窄、品质因数Q高、选择性好的同轴布喇格反射器,提出一种倒圆锥型双重正弦同轴结构设计。基于耦合模式理论,在普通正弦槽结构的基础上,叠加刻蚀周期较小的辅助正弦分布,在导体内外壁上增加倒锥度,形成倒圆锥型双重正弦同轴布喇格结构。通过FORTRAN软件仿真得出,与普通正弦槽相比,倒圆锥型双重正弦同轴布喇格结构的工作模式和竞争模式的带宽更窄,品质因数Q得到提高,残余旁瓣现象得到抑制。同时,竞争模式的中心谐振频率点远离工作模式,带隙重叠进一步分离,频率选择性得到提高。该结构设计简单,方法合理,可以更好地分离工作模式和竞争模式,构建高品质因数Q、高功率的单一高次模谐振腔。     

Tunable combline filter with continuous control of center frequency and bandwidth

A new combline filter structure with a continuous tunability for both the center frequency and bandwidth is presented in this paper. The passband-width tunability is achieved by placing variable coupling reducers between the filter resonators. The coupling reducers, operating as bandwidth control subnetworks, are designed as detuned resonators made up of a line segment ending in a variable capacitor. The proposed filter structure is experimentally validated with the design, construction in suspended stripline technology, and characterization of a low-cost filter prototype for terrestrial digital video broadcasting receivers operating in the UHF band (470-862 MHz). Other relevant factors, such as the intermodulation distortion produced by the varactors used to control the bandwidth electronically or the power-handling performance of the constructed filter, are also discussed. The reconfigurable filter module described in this paper is very suitable for the design of flexible multifunction receiver subsystems simultaneously supporting signals with a different bandwidth.     

Digital bandpass and bandstop filters with variable center frequency and bandwidth

This paper presents a method of designing wave digital bandpass (BP) and bandstop (BS) filters whereby the center frequency and bandwidth can be independently controlled by simply changing the multiplier values. Also given are the canonic realizations for the BP and BS wave digital filters. This method of designing BP and BS wave digital filter results in a saving of coefficient registers.     

Phase shift bandwidth and scan range in microstrip arrays by the element frequency tuning

In this paper, the far-field phase shift properties of microstrip patch antennas are investigated. It is shown that, similar to reflectarrays, the resonant nature of microstrip patches can be used to change the phase of the radiated field. This phase change can be caused by the dimensional change of the microstrip patch, or by a reactive loading of its cavity such as an aperture on its ground plane. However, the available phase shift is limited by the antenna impedance bandwidth. The problem is initially investigated for conventional patch antennas, determining the available phase shift range. It is then studied for a wideband E-slot microstrip antenna, showing a considerably larger phase shift range. Then, a micro-electro-mechanical (MEM) based ground plane membrane, activated by an electrode from below, is proposed to adaptively generate and control the required phase shifts. It provides a low loss, continuously variable phase shifter that can be used at high frequencies for beam scanning in small arrays.     

泵浦激光频率漂移对光声稳频信号的影响

在CO2激光泵浦的气体太赫兹源中,泵浦激光的频率稳定性控制问题十分关键。针对基于光声效应的泵浦源稳频技术,理论分析和数值模拟了光声信号的探测条件(光声腔内气压、传声器灵敏度等)对微弱光声信号检测的影响,进而对探测条件进行了优化。在此基础上,进一步分析了泵浦激光频率在气体吸收谱线中心频率附近漂移时光声信号的变化规律。结果表明:在实际工作中,为了实现高精度的稳频,需要将光声腔的气压控制在低压范围内,并采用高灵敏度的光声传感器;当泵浦激光频率产生漂移时,利用探测到的微弱光声信号通过反馈系统可以精确地改变激光器的腔长,以实现高精度的光声稳频,且频率漂移范围可控制在MHz量级以内。     

Analysis of a high frequency and wide bandwidth active polyphase filter based on CMOS inverters

An active polyphase filter capable of high frequency quadrature signal generation has been analyzed. The resistors of the classical passive polyphase filter have been replaced by transconductors, CMOS inverters (F. Tillman and H. Sjöland, Proceedings of the Norchip Conference (pp. 12–15), Nov. 2005; Analog Integrated Circuits and Signal Processing, 50(1) 7–12, 2007). A three-stage 0.13 μm CMOS active polyphase filter has been designed. Simulations with a differential input signal show a quadrature error less than 1° for the full stable input voltage range for frequencies from 6 GHz to 14 GHz. Phase errors in the differential input signal are suppressed at least three times at the output. Corner simulations at 10 GHz show a maximum phase error of 3° with both n- and pMOS slow, in all other cases the error is less than 0.75°. The three-stage filter consumes 34 mA from a 1.2 V supply. To investigate the robustness of the filter to changes in inverter delay, an inverter model was implemented in Verilog-A. Linear c _in and g _in were used, whereas g _m , c _out , and g _out were non-linear. It was found that the filter could tolerate substantial delays. Up to 40° phase shift resulted in less than 1.5° quadrature phase error at the output.     

Measurement of intermediate frequency bandwidth of hot electron bolometer mixers at terahertz frequency range

We have developed a new experimental setup for measuring the IF bandwidth of superconducting hot electron bolometer mixers. In our measurement system we use a chopped hot filament as a broadband signal source, and can perform a high-speed IF scan with no loss of accuracy when compared to coherent methods. Using this technique we have measured the 3 dB IF bandwidth of hot electron bolometer mixers, designed for THz frequency operation, and made from 3-4 nm thick NbN film deposited on an MgO buffer layer over crystalline quartz.     

高频电磁波的透入深度

高频电磁波与导波介质的作用,涉及光纤通信、宇航通信等领域,这里将根据场论就高频电磁波（包含光频）的透入深度进行论述。这里的导波介质空间可视为没有自由电荷和传导电流的空间,根据麦克斯韦电磁场方程×Ｈ＝Ｄｔ×Ｅ＝Ｂｔ·Ｄ＝０·Ｂ＝０对于频...     

Influence of silicon doping density on vacuum field emission triode at high frequency range

Silicon FEA will affect the high frequency application of field emission tubes when it works at the microwave frequency range. This article shows that the electron emitting will be influenced by the majority carrier response time in semiconductor silicon. The surface capacitance and delay time of n-type and p-type silicon are calculated by using semiconductor theory. The result shows that the semiconductor conductivity will determine the maximum work frequency of device. The maximum work frequency (no considering other effects such as C_gc, g_m etc.) will be decreased from about 200 GHz to 2 GHz when the resistivity of p-type silicon is increased from 0.1 Ω · cm to 10 Ω cm.     

离子波纹场纵向电场分量对离子波纹激光的影响

通过非线性数值模拟，研究了离子波纹激光（ＩＲＬ）中离子波纹场的纵向电场分量对束－波互作用的影响。结果表明，离子波纹场的纵向分量对ＩＲＬ的工作状况具有较大的影响。其中互作用长度的选择是非常重要的     

Practical design considerations for a variable center frequency, constant bandwidth, and constant peak-value active filter

Frequency active filters are designed by treating the operational amplifier as ideal. Consequently, the actual circuit's performance may depart considerably from what is expected. This is demonstrated in the design of an active bandpass circuit. However, it is shown that good agreement results between the predicted and actual performance if the operational amplifier's frequency dependence and output resistance are taken into account. Expressions are derived for the pole shift caused by the nonideal amplifier. Subject to given constraints, quantitative results are given that establish an upper bound on the frequency of operation of the bandpass circuit.