A tri-section stepped-impedance resonator for cross-coupled bandpass filters

We report a new tri-section stepped-impedance resonator (SIR) that features a short and low-impedance section inserted in a two-section SIR. The inserted section not only makes the resonator more compact, but also enables the flexibility of introducing cross coupling in a filter configuration. Using the tri-section SIR, a cascaded triplet bandpass filter is demonstrated, featuring sharp roll-off at the high edge of the passband.     

横向双模双频滤波器设计

基于横向滤波器耦合结构,采用支节加载双模谐振器,设计了中心频率位于1.57 GHz(GPS应用)与2.4GHz(WLAN应用)的双频微带滤波器。由短路支节加载双模谐振器形成第一个通带,开路支节加载双模谐振器形成第二个通带,两个谐振器被输入/输出馈线隔离,每个通带的中心频率与带宽可以单独调节。测试结果表明:两个通带内的最小插损分别为2.18,1.35 dB,3 dB带宽分别为5.2%,6.8%,回波损耗均小于16 dB,三个传输零点分别位于1.28,2.08,2.71 GHz处。该滤波器具有尺寸小、带外选择性好等优点。     

Synthesis of cross-coupled resonator filters using an analyticalgradient-based optimization technique

We propose a general approach to the synthesis of cross-coupled resonator filters using an analytical gradient-based optimization technique. The gradient of the cost function with respect to changes in the coupling elements between the resonators is determined analytically. The topology of the structure is strictly enforced at each step in the optimization thereby eliminating the need for similarity transformations of the coupling matrix. For the calculation of group delays, a simple formula is presented in terms of the coupling matrix. A simple recursion relation for the computation of the generalized Chebychev filtering functions is derived. Numerical results demonstrating the excellent performance of the approach are presented     

频变交叉耦合带通滤波器的耦合矩阵综合研究

综合代表滤波器拓扑结构和特性的耦合矩阵是交叉耦合滤波器设计的重点。提出了一种基于广义特征值的优化综合方法,通过非线性最小二次求解,将耦合矩阵的广义特征值逼近至广义切比雪夫响应多项式传输函数零极值参考点,优化求解出带有频变交叉耦合带通滤波器的耦合矩阵。通过3个数值实例演示了该方法,并验证其有效性。这是对经典带通滤波器耦合矩阵综合方法的补充,为频变交叉耦合滤波器的设计建立了基础。     

A novel self-coupled dual-mode ring resonator and its applications to bandpass filters

A novel dual-mode ring resonator with self-coupled segments, called a self-coupled ring resonator, is proposed. The self-coupling between ring segments provides the same mode perturbation effect as the conventional methods of adding stub, cutting notch, or varying line impedance on the ring resonator. The mode perturbation and transmission-zero generation due to the self-coupling effect are analyzed with the even-odd mode theory. The self-coupled ring resonator can have the capacitive or inductive perturbation simply by controlling the impedance ratio and coupling coefficients of self-coupled sections. For both perturbation cases, the transmission zeros exist at even multiples of the passband center frequency, resulting in wide stopband range. Also, only for the capacitive perturbation case, two transmission zeros are found on both sides of the passband, which brings a pseudo-elliptic bandpass response. In comparison with the regular uniform ring resonator, the self-coupled ring resonator takes shorter ring length, giving the compact size feature when applied to a bandpass filter design. A 2.45-GHz low-temperature co-fired ceramic bandpass filter based on the self-coupled ring resonator was designed to verify the proposed theory.     

A design method of optical bandpass filters

A design method of optical bandpass filters which are composed of several resonators consisting of dielectric layers is discussed. The relation between the loaded Q of a resonator and the thickness of each layer is calculated by treating equivalently each layer as a segment of transmission line and represented on a chart. It becomes possible to design an arbitrary value of loaded Q by using the chart. Thus, an optical bandpass filter of required bandwidth and rejection characteristic can be designed by finding out the optimum thickness of each layer of the resonator which is the component of the filter     

交叉耦合带通滤波器的优化研究及仿真

第五代移动通信技术对系统的滤波性能有着更高的要求,所以滤波器的优化是保障系统性能的关键所在。首先通过对滤波器函数多项式的损耗分析,推导出各项滤波指标与谐振器无载Q值之间的函数关系,并在一定的拓扑结构中进行仿真验证。然后对每个谐振器无载Q值进行补偿仿真,通过采用高Q值谐振器的方法,使通带边频点的损耗及响应曲线得到改善,最终实现滤波器优化设计的目标。     

Universal curves for bandpass filters

Universal curves are presented which permit the determination of bandpass poles when band-edge frequencies and low-pass poles are known. These curves are also useful for band-reject filters.     

Frequency synthesis based on bandpass sigma-delta modulation

A PLL frequency synthesiser using a bandpass sigma-delta digital oscillator as the frequency reference is described. The system emphasises digital signal processing and allows the use of a wideband loop filter     

Compact hexagonal open-loop resonator bandpass filters using capacitive side-coupled stub and spurline technique

Compact quasi-elliptic bandpass filters using hexagonal open-loop resonators are presented. To miniaturise circuit size, a pair of capacitive side-coupled stubs and two pairs of spurlines are placed skilfully into the filter structure. The new filter operating at 1.65 GHz was analysed, simulated and fabricated. Good agreement between simulations and measurements verified the validity of the methodology. Moreover, the circuit size only occupies 21.1 x 14.1 mm2 (?0.21λg x ≅0.14λg).     

Zolotarev bandpass filters

Zolotarev rational functions may be used in certain bandpass filter applications for which two narrower passbands are required. Coupled-resonator low-pass prototypes for narrow bandpass filters based on even- and odd-degree Zolotarev functions are synthesized using a transformed variable. Compared to other filters, those with Zolotarev responses have sharper skirt selectivity, resulting in lower passband distortion     

Inductorless bandpass filters

The technique of designing inductorless filters by replacing the inductors in conventional LC filters with gyrators and capacitors is considered for the special case of the high-quality channel bandpass filters used in multiplex telephony. One particular gyrator circuit, which has been found to be very satisfactory, using two operational amplifiers and four resistors, is analyzed in some detail. The difficulties of simulating floating inductors are discussed, and ways of designing filters to avoid the necessity of such simulations are proposed. The dynamic range of a filter is defined and the factors controlling it are described. Detailed measured results of two specific channel filter designs are included.     

Integrated bandpass filters

The letter presents some new results associated with one bandpass (b.p.) filter configuration of the integrated uniform R0-C0KR0 structure consisting of two rectangular resistive films, one having per-unit-length (p.u.l.) constant series resistance R0 and the other KR0 (where K is a dimensionless constant), separated from each other by a dielectric film having p.u.l. constant shunt capacitance C0. It is shown that the output voltage in the b.p. region may be made almost constant for the load fluctuations in the wide range R0 ? Rt < ? (where Rt = load resistance) by selecting K ? 0.3. The range of variation of Rt producing constant output voltage in the b.p. region is found to be narrower for increasing value of K.     

10 Gbit/s timing recovery circuit using dielectric resonator and active bandpass filters

A clock recovery circuit that employs a dielectric resonator, designed for the 10.368 Gbit/s demonstrator of the R1051 RACE project is described. Experimental results have shown a jitter performance and sensitivity to detuning well within usual specifications for practical links. This circuit thus provides a very attractive low cost solution for multigigabit transmission.<>     

Dual-mode stepped-impedance ring resonator for bandpass filterapplications

It is well known that two orthogonal resonant modes exist within a one-wavelength ring resonator. In this paper, we focus on a ring resonator possessing an impedance step as a form of perturbation. A convenient analyzing method for obtaining the resonance characteristics of this resonator structure is presented. Furthermore, generation of attenuation poles obtained by the dual-mode ring resonator is discussed. In addition, a filter design method based on this resonator is explained, followed by experimental results, which prove the validity of the proposed design method     

Two network-frequency transformations for bandpass filters

The two unsymmetrical stopbands of a general parameter bandpass filter can be interchanged by a simple network transformation. Another simple network transformation scales the bandwidth of a narrowband filter while preserving all its shape factors. Both transformations preserve the minimum-inductance property.     

Maximum Q factors for bandpass filters

The letter gives curves that relate the Q factors of the maximum Q pole of a bandpass filter to the normalised bandwidth of the filter.     

Maximum Q-factors for symmetrical bandpass filters

The letter presents curves for the estimation of the maximum pole Q-factors for geometrically symmetrical Butterworth. Cheby?shev and elliptic bandpass filters.