Computer-aided diagnosis and tuning of cascaded coupled resonatorsfilters

A model for the determination of the individual resonant frequencies and inter-resonator couplings of a system consisting of cascaded coupled resonators is presented. Measuring or computing the phase of the reflection coefficient of short-circuit terminated networks synthesizes all the inter-resonator couplings and resonant frequencies. The loading effect on the last resonator due to the unknown position of the short-circuit reference plane is accurately accounted for by a systematic method. A deterministic finite steps tuning method based on the model is developed. The method is proven successful experimentally and the noniterative nature of the method makes fully automatic tuning of filters possible     

High-efficiency resonant coupled wireless power transfer via tunable impedance matching

For magnetic resonant coupled wireless power transfer (WPT), the axial movement of near-field coupled coils adversely degrades the power transfer efficiency (PTE) of the system and often creates sub-resonance. This paper presents a tunable impedance matching technique based on optimum coupling tuning to enhance the efficiency of resonant coupled WPT system. The optimum power transfer model is analysed from equivalent circuit model via reflected load principle, and the adequate matching are achieved through the optimum tuning of coupling coefficients at both the transmitting and receiving end of the system. Both simulations and experiments are performed to evaluate the theoretical model of the proposed matching technique, and results in a PTE over 80% at close coil proximity without shifting the original resonant frequency. Compared to the fixed coupled WPT, the extracted efficiency shows 15.1% and 19.9% improvements at the centre-to-centre misalignment of 10 and 70 cm, respectively. Applying this technique, the extracted S₂₁ parameter shows more than 10 dB improvements at both strong and weak couplings. Through the developed model, the optimum coupling tuning also significantly improves the performance over matching techniques using frequency tracking and tunable matching circuits.     

Sequential tuning of microwave filters using adaptive models and parameter extraction

This paper describes a sequential procedure for computer-aided tuning and diagnosis of multiple-coupled resonator filters. The method is based on a sequential parameter estimation and a systematic tuning procedure and employs three different filter models. A detuned model represents the initial status of the filter after a well-defined detuning procedure. The target filter is described by an ideal model, whereas the actual state of the filter at each tuning step is represented by a coarse adaptive model. The goal of the procedure is the convergence of the coarse model to the ideal model and will be obtained by systematically centering resonant frequencies and coupling coefficients. Practical examples comprising low- and high-degree filters confirm the effectiveness of the proposed approach in both tuning and fault diagnosis.     

可调频矩形帖片天线的研究

本文首次采用有限元法对有调谐销钉的可调频薄基片矩形贴片微带天线的谐振频率和输入阻抗进行了计算,谐振频率的计算结果与实验结果符合很好.该方法原则上适合于任意数目调谐销钉置于任意位置的情形.可能会是处理带调谐销钉的最有效的方法.     

10 GHz LC-tuned VCO with coarse and fine frequency control

The authors present a monolithic 10 GHz voltage-controlled oscillator (VCO) using an LC resonant circuit for tuning. The basic approach for designing this fully differential VCO will be described, followed by practical modelling considerations, and an explanation of experimental results. Two methods of tuning the resonant frequency will also be addressed with respect to their impact on circuit performance     

Mode selection in doubly-resonant optical parametric oscillators

By using a computer model to calculate the threshold for each signal and idler mode-pair in doubly resonant optical parametric oscillators, we investigate the effects of the three principal tuning parameters (temperature, cavity length, and pump wavelength) on the mode selection. Through consideration of type I and type II noncritical phase-matched geometries for lithium triborate optical parametric oscillators, we illustrate that the tuning behavior depends on the difference between the refractive indexes experienced by the signal and idler fields     

Simulation study of compact quantising circuits usingmultiple-resonant tunnelling transistors

The authors have applied a simple modelling approach for multiple resonant tunnelling transistors (mRTTs) which includes four resonant tunnelling diodes (RTDs) within the transistor structure. Unique features of this model, corresponding to device features compatible for integrated circuits, allow far tuning and matching the devices for optimum circuit performance. Two circuits are presented for analogue to quaternary conversion with analysis of their transfer characteristics; this analysis is consistent with the simulation results and implies that circuits of physical devices may be successfully implemented     

微波化学谐振腔的模式抑制研究

对一种微波化学反应腔及其中的圆柱腔如何实现单模谐振和调谐进行了研究,得到了不会因为置入材料的不同而产生失配的新型系统结构。在腔体和系统设计中,谐振腔由谐振腔主体、谐振腔上盖和谐振腔下盖组成,谐振腔下盖通过电机升降实现上下移动,由此改变腔体的谐振频率,实现了2.2~2.6 GHz 的调谐范围。利用标量函数法分析扇形腔的场结构,根据目标模式的分布特点提出了多种干扰模式净化技术,最后得到了频率范围为2.2~2.6 GHz 的单模谐振腔。     

Wide-Range Varactor-Tuned Terahertz Oscillator Using Resonant Tunneling Diode

We propose a wide-range varactor-tuned terahertz oscillator using a resonant tunneling diode (RTD) and estimate the tuning range. In a slot antenna, a varactor diode is placed in parallel with an RTD and can be operated with different bias voltages. Frequency tuning is possible by changing the varactor-diode capacitance with the bias voltage. A wide frequency tuning range >200 GHz (500 to 740 GHz) is obtained with an oscillator with a 20-μm-long antenna, 1.3-μm² RTD mesa, and 16-μm² varactor-diode mesa by electromagnetic-field analysis including a varactor-diode model.     

Nonlinear modeling and analysis of resonant inverter tuning loops with voltage-pump phase-frequency detector

In this paper, a nonlinear model for large signal analysis of resonant inverter (RI) tuning loops with voltage-pump phase-frequency detector is presented. The proposed model employs the resistance multiplication approach, applicable for the circuits containing periodically operated switch. The generic model is valid for both positive and negative phase error values with slight differences. Transient and stability analysis of an RI tuning loop is carried out by employing the presented model. Time-domain expressions for any initial condition are derived as the result of transient analysis. On the other hand, stability analysis reveals the conditions that make the overall system stable. Experimental results, which confirm the theoretical study, are obtained.     

Analysis of Annular Ring Microstrip Antenna with Air Gap and Uniaxial Substrate Superstrate Layers

Analysis of superstrate loaded, air gap tuned annular ring microstrip antenna is performed and effects of air gap tuning on the resonant frequency are investigated. Results obtained indicate that due to air gap tuning, resonant frequency can be incrementally or decrementally changed depending on the adjustment of anisotropy ratio of substrate and superstrate layers. Results can be used to obtain tunable, wideband antenna operation.     

Frequency agile slot-fed patch antenna

The authors present an original application of a slot-fed patch antenna. Voltage controlled tuning varactors are connected across the radiating edges of the patch antenna and the resonant frequency can be adjusted in a large frequency band (up to 1 GHz) while the impedance matching remains good. Results based on the transmission line model are compared with measurements     

Compensation of superstrate effects on the resonant behavior of themicrostrip ring structure by using an air-gap control

In this paper, spectral-domain analysis is utilized to investigate the possibility of compensation of superstrate shielding effects on the resonant behavior of the microstrip ring structure by means of an adjustable air-gap inserted between the substrate and the ground plane. In order to provide the desired amount of tuning, the adjustment of the proper gap thickness is discussed for various structural parameter cases. It is shown that the resonant frequency shift due to superstrate shielding can be compensated, the resonant bandwidth and, hence, the electromagnetic interference can be directly controlled resulting of the proposed tuning scheme     

Design of reconfigurable slot antennas

In this paper the design of a compact, efficient and electronically tunable antenna is presented. A single-fed resonant slot loaded with a series of PIN diode switches constitute the fundamental structure of the antenna. The antenna tuning is realized by changing its effective electrical length, which is controlled by the bias voltages of the solid state shunt switches along the slot antenna. Although the design is based on a resonant configuration, an effective bandwidth of 1.7:1 is obtained through this tuning without requiring a reconfigurable matching network. Four resonant frequencies from 540-890 MHz are selected in this bandwidth and very good matching is achieved for all resonant frequencies. Theoretical and experimental behavior of the antenna parameters is presented and it is demonstrated that the radiation pattern, efficiency and polarization state of the antenna remain essentially unaffected by the frequency tuning     

数字解调自激励频率调制原子力显微镜

研制了以石英音叉探针作为力传感器的频率调制原子力显微镜（FM-AFM）。利用石英音叉具有压电特性且品质因数高的特点,采用正反馈回路控制石英音叉自激振动于实时共振频率处,通过反馈回路中设置自动增益控制环节控制石英音叉振幅恒定;以简单的标定方法,由流经石英音叉的电流定量计算出石英音叉探针的振动幅度;设计了基于现场可编程逻辑...     

Phase detector for tuning circuit of resonant inverters

The tuning circuit in a resonant inverter determines the inverter frequency and makes it track the load resonant frequency. Current phase detectors have some serious drawbacks for this application. A new phase detector circuit is presented which can overcome these drawbacks.     

A Wide Tuning Range Voltage Controlled Oscillator Using Common-Base Configuration and Inductive Feedback

Usually the tuning range of voltage controlled oscillator (VCO) is much narrower than the possible resonant frequency range of the tank at different tuning voltages. In this letter we analyze the traditional common-base type VCO, give a simple but useful insight about the mechanism behind the topology, and verified the conclusions with a 2 mum heterojunction bipolar transistor (HBT) VCO. The results show that with the CB configuration, proper feedback inductor and wide tuning range varactor, the tuning range can be almost the same as the resonant frequency range of the tank at different tuning voltages. A wideband voltage controlled oscillator using a commercial 2 mum HBT technology is designed, fabricated and measured. The varactor with wide range of capacitance is used to achieve 53.33% measured tuning range from 9.46 to 16.34 GHz. The measured phase noise at 1 MHz offset is between -90 and -102 dBc/Hz. The total chip size is 1 mm² including all testing pads, while the core area is 0.64 mm². The VCO is suitable for wideband application such as in measurement equipment or astronomical exploring telescopes.     

Tunable Liquid Crystal-Resonant Grating Filter Fabricated by Nanoimprint Lithography

We demonstrate a tunable filter consisting of a subwavelength resonant grating filter cladded by a liquid crystal cell. The resonant wavelength of the grating filter is tuned by electrically varying the refractive index of the liquid crystal. A tuning range of around 20 nm has been achieved.     

Tuning stubs for microstrip-patch antennas

A practical method for the simultaneous tuning, of both the resonant frequency and reflection coefficient, of a coaxially fed rectangular-microstrip patch is described. The use of two tuning stubs allows independent adjustment of the effective patch length and the effective position of the feed point. The effective length determines the resonant frequency of the patch, while the effective position of the feed point determines the input impedance. It is demonstrated that the method allows the adjustment of the feedpoint reflection coefficient of a patch to less than -60 dB, at a frequency which is within 0.005% of specification     

Tunable circular patch antennas

A method to control the resonant or operating frequencies of circular patch antennas has been investigated experimentally and theoretically. It consists of the placement of passive metallic or tuning posts at approximate locations within the input region of the antenna. Comparison of measured and analytical results seems to establish the validity of a theoretical model proposed to determine the input performance of such circular patch antennas.