The Q factor of resonators containing transmission line sections and several capacitors

Relationships are obtained for determination of unloaded Q factor of microwave resonators tuned by several capacitors. New concepts are proposed for the variation of the Q factor of resonators during their tuning. It is proved that the unloaded Q factor of a composite resonator does not depend on the number of tunable capacitors with equal Q factor.     

Theoretical analysis of the coupling between whispering-gallery dielectric resonator modes and transmission lines

Whispering-gallery dielectric resonator modes coupled to one or two transmission lines form a millimetre-wave directional filter or a millimetre-wave stopband filter. The coupling is discussed and a formula for loaded Q is proposed.     

Basic transmission loss and delay spread measurements for frequencies between 430 and 5750 MHz

Impulse response radiowave propagation measurements from an urban area of Denver, CO, are described. The basic transmission loss and delay spread are used to characterize the mobile communications environment. These metrics are quantified using path loss slope and delay spread statistics. By analyzing the results versus carrier frequency, the relative propagation impairments at 430, 1350, 2260, and 5750 MHz are compared. It was found that the path loss slope increased on average by 11 dB/dec and the median delay spread decreased from 0.7 to 0.3 /spl mu/s over the decade of frequencies measured.     

A procedure for measuring the Q factor of and attenuation in microwave composite acoustic resonators

A procedure for measuring the Q factor of a microwave composite acoustic resonator is described. The resonator consists of a relatively thick crystal plate and a piezoelectric film with electrodes that is deposited on the plate. The procedure is based on mathematical processing of the array of measurement data on the coefficient of the electromagnetic-wave reflection from the resonator structure connected to a microwave reflectometer. Via this procedure, it is possible to obtain data on the Q factor at the resonance and antiresonance frequencies.     

基于FFT的传输线串扰时域响应分析与实验研究

基于传输线分布参数结点导纳方程和快速傅立叶反变换方法,仿真分析了传输线串扰电压响应及传输线参数和端接阻抗对串扰电压峰值的影响.发现在不考虑传输线终端负载电阻的电感影响时,仿真结果中振荡不明显,在考虑电感时仿真结果振荡较明显.基于实验室研究设备,对共地平行传输线间的串扰电压和电流进行了实验研究,并将部分实验结果与理论仿真结果进行了比较.结果显示:在考虑传输线终端负载电感时的仿真波形与幅度和测量结果的波形与幅度基本一致,仿真的脉冲宽度要大于测量脉冲宽度,仿真结果峰值略大于测量峰值.     

Directional coupler for gigahertz frequencies, based on the coupling properties of two planar comb transmission lines

The principles of operation are given for a directional coupler based on the coupling properties of two interleaved planar comb transmission lines. It is shown that this arrangement leads to a departure from a contradirectional coupling mechanism. Results are given for an X band ?3 dB coupler, and the performance and manufacturing methods are compared with those of other high-frequency coupler designs.     

Comments on the utilization of noise measurements for the characterization of electromigration in metal lines

Some of the problems connected with the characterization of electromigration by means of noise measurements are discussed in this paper. Some specific criticisms moved in the past toward the interpretation of the experimental data are also addressed. In particular, the question of the interpretation of the 1/ƒ² noise component is discussed. Finally, a set of rules are given which should be followed, both in the choice of the instrumentation and in performing the measurements, in order to obtain meaningful and reliable results.     

Long term noise measurements and median time to failure test for the characterization of electromigration in metal lines

The high sensitivity, which can be obtained by means of noise measurements, is especially useful for the characterization of the early stages of the electromigration phenomenon. In addition, with the noise being strictly dependent on the sample microstructure, it is obvious to expect that it can be used for monitoring the different stages of the degradation process. In this paper, the results obtained by performing noise measurements during lifetime tests are presented, with the aim of investigating the evolution of the electromigration noise during the entire life of the sample. Conventional Median Time to Failure (MTF) tests have been performed on samples belonging to the same set. One of the aims of this work is to investigate the possibility of establishing a new failure criterion based on noise measurement capable of providing, in a shorter time, the same type of information normally obtained from MTF tests.     

Analytic expressions for the reflection delay, penetration depth,and absorptance of quarter-wave dielectric mirrors

The authors analyze the operation of high-reflectivity quarter-wave (QW) dielectric mirrors at the band-stop center (Bragg) frequency, relevant for the design of small-cavity optoelectronic structures. The energy penetration depth concept is used to determine a first-order linear approximation for the reduction of the mirror peak reflectivity of the QE mirror as a function of the mirror material parameters and the number of layers. The expression can be applied in the limit of small loss. The mathematical analysis and expressions for the absorptance and the peak reflectivity of a dielectric mirror with weak material absorption are presented. The use of the results is illustrated for a typical vertical cavity surface-emitting laser structure     

Modified method for the analysis and design of microwave bandpass filters containing dielectric resonators

High-Q dielectric resonators having remarkable advantages such as compactness, light weight, temperature stability, and low cost have become very valuable elements for various microwave circuits. A modified Itoh and Rudokas model is proposed to analyse the field distribution and the coupling relations between dielectric resonators and microstrip lines based on the analysis results, a convenient procedure for designing microwave filters containing parallel coupled dielectric resonators is presented. Two experimental dielectric resonator filters are also fabricated to verify the calculation and the design procedure. The outcome demonstrates that the procedure provides good accuracy and saves design time.     

直线法分析一维非均匀矩形波导的传输特性

用直线法对一维非均匀矩形波导进行了分析,由传递矩阵获得了该波导不同模式的特征方程.以部分非均匀介质填充的矩形波导为例,对其色散特性和截止特性进行了数值计算和分析,验证了该方法的正确性.对研究非均匀波导问题有参考价值.     

Decision-directed PLL for coherent optical pulse CDMA systems inthe presence of multiuser interference, laser phase noise, and shotnoise

A digital decision-directed phase-locked loop (PLL) for use in optical pulse code-division multiple-access (CDMA) systems based on coherent correlation demodulation is proposed. PLL performance is affected by multiuser interference, laser phase noise and optical shot noise. The effect of these sources of interference and noise on PLL performance is evaluated based on a nonlinear model (the Fokker-Planck method) since a linear analysis yields large deviations between the analytical results and actual performance at low signal-to-noise ratios (SNRs). After describing the implementation of the PLL, the steady-state probability density function (pdf) of the phase estimator is derived. Numerical evaluation of the variance of the phase estimator is given for Gold codes. The linewidth requirements of the laser for an acceptable phase estimator variance and the value of the optimal loop bandwidth minimizing the impact of the interference and noise on the PLL are discussed     

Grating coupling elements for high-Q resonators and rectangular waveguides of the millimeter wave band

Techniques for electrodynamic-level calculation of slot-grating wideband coupling elements for single-mode waveguides are developed. New coupling devices that ensure the obtaining of a voltage standing-wave ratio of 1.6 in the entire tuning range of a resonator without readjustment of the coupling element are designed and tested experimentally. It is found that application of new coupling devices in resonators do not deteriorate the loaded Q factor of the resonator.     

Features of the coupling coefficients of planar stepped-impedance resonators at higher resonance frequencies and application of such resonators for suppression of spurious passbands

Features of the electromagnetic coupling coefficients between stepped-impedance resonators made of the sections of symmetric strip and microstrip transmission lines at higher resonance frequencies are investigated. It is found that, in stripline resonators, these coefficients are equal to zero at some coordinates of the jump of the characteristic impedance. A new method of expansion of the stopband of bandpass filters, which is based on suppression of the first spurious bandpass and frequency diversity of the main band and the second spurious bandpass is proposed. A Chebyshev bandpass filter with a center frequency of 2.45 Hz and a spurious band at 6.06 f ₀ is manufactured and tested to demonstrate the proposed method.     

A computation of the reflection and transmission coefficients for dielectric coated waveguides

A previously developed variational technique for finding the approximate solution to the electromagnetic field inside waveguides of varying shapes and containing non-uniform dielectric and magnetic materials is applied to the specific case of an axisymmetric waveguide containing three layers of different dielectric materials. The magnetic permeability is taken equal to unity. The method enables the problem to be reduced to a two point boundary value problem for a pair of second order, linear, ordinary differential equations. The values of the reflection and transmission coefficients obtained by this method are in good agreement with those derived from solving the partial differential equations for the field.     

串扰耦合的低频分析有效性及阻抗特性研究

从传输线模型出发，分析了二平行直导线间串扰的低频模型有效性，得出允许3dB误差的条件下，低频模型在工程计算串扰中的电学短线和频率足够小的具体限值；同时分析了端接阻抗大小对串扰耦合的影响。对电磁兼容性中的串扰耦合的工程应用有实际指导和参考意义。     

Performance of a TDM/TDMA portable radio link for interference,noise, and delay spread impairments

Presents the measured/simulated performance of a time division multiplexing/time division multiple access (TDM/TDMA) portable radio link for noise, interference and delay spread impairments. The radio link transmits short TDMA bursts of 82 symbols at 450 kbits/sec using 4QAM. This modulation is also referred to 4PSK, but phase shift modulation is constant envelope. Nyquist filtering of quadrature signal components yields quadrature amplitude modulation which, of course, also contains π/2 phase variations at the sampling instants. Demodulation is performed by a low-overhead digital coherent demodulator with 2-branch selection diversity. The port or base has two receivers for diversity but the portable or handset uses only a single receiver to perform selection diversity. Signal-to-noise ratio and signal-to-interference ratio performance of the link was measured for a stationary channel and for a channel with different fading rates. In a Rayleigh fading environment, increasing the fading rate causes only a small performance degradation. The results also show that selection diversity is effective against interference in a slow Rayleigh fading environment. A separate set of experiments were performed to measure the effects of delay-spread on the link. Selection diversity is effective in reducing the word-error ratio floor caused by frequency-selective fading. As a result, relatively high data rates can be supported by a multipath fading channel without using adaptive equalization. Thus, a portable radio communications system using low complexity hardware design incorporating selection diversity can achieve good performance     

Using S-parameter measurements to determine the threshold voltage, gain factor, and mobility degradation factor for microwave bulk-MOSFETs

In this paper, we present an extraction and characterization methodology which allows for the determination, from S-parameter measurements, of the threshold voltage, the gain factor, and the mobility degradation factor, neither requiring data regressions involving multiple devices nor DC measurements. This methodology takes into account the substrate effects occurring in MOSFETs built in bulk technology so that physically meaningful parameters can be obtained. Furthermore, an analysis of the substrate impedance is presented, showing that this parasitic component not only degrades the performance of a microwave MOSFET, but may also lead to determining unrealistic values for the model parameters when not considered during a high-frequency characterization process. Measurements were made on transistors of different lengths, the shortest being 80 nm, in the 10 MHz to 40 GHz frequency range.     

A simple procedure for measuring the Q factor of and attenuation in acoustic-resonators

A simple procedure for measuring the Q factor of piezoelectric and acoustic composite resonators operating in the microwave band is described. The procedure is based on measuring (in the near-resonance regions) the phase of the reflection coefficient of the electromagnetic wave reflected from a resonance structure connected to a microwave reflectometer.     

Circulating power, RF magnetic field, and RF current density ofshielded dielectric resonators for power handling analysis ofhigh-temperature superconducting thin films of arbitrary thickness

In the current quest for HTS films with negligible power effects at high RF power levels for wireless communications, accurate calculations of a maximum RF magnetic field H_max and of a maximum RF current density J_max flowing on the surface of superconducting films is necessary to allow for any sensible conclusions and comparisons. As the dielectric resonator method is used most frequently for investigation of HTS losses, the authors discuss in this paper a dependence of the circulating power and of a maximum RF magnetic field H_max on dielectric resonators' geometry as well as of the maximum RF current density J_max flowing on the surface of superconducting films on the films' thickness, for a general case of a resonator shielded in a metallic cavity. The authors' results demonstrate that under the same input power levels the same HTS films may be exposed to differing RF power level conditions, depending on the cavity to dielectric radius ratio and thickness of superconducting films. This means that there may be a significant discrepancy between calculated and real power handling capabilities of HTS films tested in different dielectric resonators unless correct formulas are used