Ke-Li Wu

A compact second-order LTCC bandpass filter with two finite transmission zeros

A novel implementation and associated design formula for a compact low-temperature cofired ceramics (LTCC) lumped-element second-order bandpass filter are proposed in this paper. The filter schematic that provides two finite transmission zeros is well known. It is shown in the paper that the filter schematic is built on a pair of conventional inductive coupled resonator tanks with a feedback capacitor between input and output. While revealing its working mechanism both graphically and mathematically, a simple design procedure for such a compact filter is also given. The proposed filter has been implemented in a six-layer ceramic substrate using LTCC technology, showing promising application potentials in miniaturized mobile terminals and Bluetooth RF front-ends. The measured results agree very well with the full-wave electromagnetic designed responses.

A dispersive boundary condition for microstrip component analysis using the FD-TD method

A dispersive absorbing boundary condition (DBC) which allows the dispersion characteristics of waves to be used as a criterion for designing absorbing boundary conditions is presented. Its absorbing quality is superior to that of the presently used Murs first-order boundary condition for microstrip component analysis, and its implementation is much simpler when compared to that of the super boundary condition treatment. Due to the significant performance improvement of the new boundary condition, the memory requirement can be reduced greatly when applying this boundary condition to microstrip component analysis. >

A compact 2-D full-wave finite-difference frequency-domain method for general guided wave structures

A compact two-dimensional (2-D) full-wave finite-difference frequency-domain method is proposed for the analysis of dispersion characteristics of a general guided wave structure. Because the longitudinal field components are eliminated in the proposed method, only four transverse field components are involved in the final resulting eigen equation. This feature considerably reduces the required CPU time as compared to the existing approaches by which six field components are comprised. Additionally, unlike other 2-D finite-difference schemes that determine the eigenfrequency for a given propagation constant, the new method finds the propagation constant /spl beta/ for a given k/sub o/ (frequency). The new method has been verified by examining the computed results of a number of typical guided wave structures with the published results. Very good agreement is achieved.

Accurate characterization of planar printed antennas using finite-difference time-domain method

The finite-difference-time-domain method (FD-TD) is used to characterize complex planar printed antennas with various feed structures, which include coaxial probe feed, microstrip line feed, and aperture coupled feed structures. A coaxial probe model is developed by using a three-dimensional FD-TD technique. This model is shown to be an efficient and accurate tool for modeling coaxial line fed structures. A novel use of a dispersive absorbing boundary condition is presented for a printed antenna with a high dielectric constant. All the numerical results obtained by the FD-TD method are compared with experimental results, and the comparison shows excellent agreement over a wide frequency band. >

An LTCC balanced-to-unbalanced extracted-pole bandpass filter with complex load

In this paper, the fundamental characteristics of a novel third-order RF balanced-to-unbalanced filter, namely, a balun filter, for integrated RF module applications are presented. This center-tapped transformer-based new device works concurrently as a balun, an extracted-pole bandpass filter, and a matching network. As coupled resonant tanks are employed to perform the balun type of operation, traditional coupled-resonator filter theory can thus be used to design and analyze such a new device. Moreover, an extracted-pole technique is used not only for creating a transmission zero, but also provides a capability to match the filter with a complex load. In addition to providing a simple design procedure for the device, its working mechanism is also revealed mathematically. Specifically, return-loss sensitivity with respect to each resonator admittance and complex load matching capability are discussed in details. This balun filter has been implemented in a multilayered low-temperature co-fired ceramic substrate, demonstrating its promising potentials in miniaturized RF front-end modules. Experimental measurements are also presented to validate the theory and computer simulations.

A Dual-Band Coupled-Line Balun Filter

In this paper, a new type of device called dual-band coupled-line bandpass balun filter is presented. Based on the traditional coupled-line filter theory and Marchand balun configuration, a new device with both filter-type, as well as balun-type characteristics is proposed. The new device utilizes -type transmission-line stepped-impedance resonators to achieve a dual-band operation. Besides providing a simple design procedure for the device, its working mechanism is also revealed mathematically. A prototype balun filter operating at 2.4 and 5.8 GHz has been realized using traditional printed circuit board technology to validate the proposed concept and theory, showing promising application potentials for future multiband RF wireless transceiver modules. Experimental measurements show good agreement with analytical and computer simulations.

A novel broadband microstrip-fed wide slot antenna with double rejection zeros

A novel broadband microstrip-fed slot antenna with double rejection zeros is proposed and developed by constructing simultaneously a wide-slot radiator and a quarter-wavelength microstrip line resonator. A comprehensive explanation of its operating principle is given by using an equivalent two-pole filtering network, in which the radiation resistance is perceived as the output impedance. Extensive numerical results are then obtained using a commercial electromagnetic simulator to demonstrate its attractive broadband feature. Finally, a few antenna samples are designed, fabricated, and measured to verify the predicted performance. Experimental results exhibit that the bandwidth of this proposed antenna configuration is significantly increased, by up to 32.0%, as compared to 9.0% for its traditional counterpart.

Multilayer LTCC bandpass filter design with enhanced stopband characteristics

Lumped-element bandpass filter structures with enhanced stopband rejection targeted for low temperature co-fired ceramic (LTCC) implementation are proposed. Design equation formulations that take into account the effect of the transmission zeros are presented. For demonstration, RF filters operating at 2.4 GHz are fabricated and characterized. Both simulation and measurement results are shown for comparison.

Fast finite-difference time-domain analysis of resonators using digital filtering and spectrum estimation techniques

The use of digital filtering and spectrum estimation techniques for improving the efficiency of the FD-TD algorithm in solving eigenvalue problems is discussed. The great improvement of the efficiency of the method is demonstrated by means of both numerical and measurement results. In addition, several improvements to the present FD-TD method for eigenvalue analysis are presented. These include the analysis of open dielectric resonators and the extraction of the resonant frequencies from the FD-TD results. The result for the open dielectric resonator analysis is validated using measured data. >

A Direct Synthesis Approach for Microwave Filters With a Complex Load and Its Application to Direct Diplexer Design

This paper presents a direct synthesis approach for general Chebyshev filters terminated with a complex load. The new approach is based on the fact that the polynomial functions for synthesizing the filters are composed for any matched loads. By normalizing the polynomial functions with assumed complex matched load impedance by a real reference load impedance using power waves normalization, a set of new polynomial functions for the same filter, but with real load impedance, can be formulated, from which the coupling matrix for the physical filter design can be obtained using a standard direct filter synthesis approach. This new direct synthesis approach can find many applications. A practical application is the direct diplexer design with a realistic junction model being taken into account. With the diplexer design is concerned, a fast-converged iterative scheme is proposed. The effectiveness and the validation of the proposed scheme are demonstrated by two design examples