Gao-Le Dai

Novel Dual-Band Out-of-Phase Power Divider With High Power-Handling Capability

In this paper, we present a novel dual-band out-of- phase power divider with high power-handling capability. The proposed device consists of five ports including one input port, two output ports, and two extra ones, which are connected by the external isolation resistors. To obtain the out-of-phase feature between the two output ports, double-sided parallel-strip lines are employed, and a conductor plane is inserted in the middle of the substrate as a common ground. A set of closed-form design equations is developed for analysis of the novel design structure by using the rigorous even- and odd-mode analysis method. The analysis shows that the proposed power divider can operate at two frequencies of f1 and mf1 with a wide frequency ratio range at 1.62 <; m <; 3. Furthermore, the power operation analysis also illustrates that the new circuit is superior in high power-handling capability over the conventional dividers with internal isolation resistors. For verification, an example power divider with frequency ratios of 2.4:1 is implemented. Simulation and experimental results agree well, validating the proposed design methodology.

Novel Miniaturized Bandpass Filters Using Spiral-Shaped Resonators and Window Feed Structures

In this paper, we present a new class of miniaturized microstrip bandpass fllters with low-insertion loss, sharp-rejection and narrow-band performance. The proposed fllters are composed of two spiral-shaped resonators and rectangle window feed structures. Both back-to-back and interdigital combinations of the resonators are adopted to obtain the miniaturized fllter size. Compared to the traditional square loop bandpass fllter, the sizes are reduced by 82% and 80%. It is also found that there is a pair of transmission zeros located on each side of the passbands, resulting in high selectivity. To validate the proposed idea, two demonstration fllters with back-to- back and interdigital spiral-shaped resonators are implemented. The measured results exhibit good agreement with the full-wave simulation results.

Dual-Band Bandpass Filter Using Parallel Short-Ended Feed Scheme

In this letter, a compact dual-band (DB) bandpass filter based on parallel short-ended feed scheme is presented. Two sets of quarter-wavelength resonators operating at diverse frequencies are adopted to generate DB responses. A special feed scheme is proposed, which consists of two parallel short-ended strip branches. Each of them acts as a feed line of the respective resonator at one passband and a loading element at the other one. This scheme provides two independent transmission paths for RF signals. It is convenient to control the center frequencies of one passband, while the others remains unchanged. Source-load coupling is also employed to create four transmission zeros close to the passband edges, resulting in high skirt-selectivity. To verify the proposed idea, a topology is demonstrated. The measured results exhibit good agreement with the full-wave simulation results.

A BROADBAND OUT-OF-PHASE POWER DIVIDER FOR HIGH POWER APPLICATIONS USING THROUGH GROUND VIA (TGV)

In this paper, we present a broadband out-of-phase power divider with high power-handling capability. The proposed device consists of several sections of double-sided parallel-strip lines (DSPSLs), a mid-inserted conductor plane, and two external isolation resistors, which are directly grounded for heat sinking. A through ground via (TGV), connecting the top and bottom sides of DSPSLs, is employed. The special metal via is realized to short the isolation resistors at full-frequency band when the odd-mode is excited. Meanwhile, it can be ignored as the excitation is even-mode. This property is e-ciently utilized to improve the bandwidth. To examine the proposed power divider in detail, a set of closed-form equations are derived. Meanwhile, the power operation analysis illustrates that the proposed power divider is a good candidate for high power applications. The design charts show that the proposed device can support a wide frequency ratio range (1{1.7). Furthermore, broadband responses can be obtained when proper frequency ratios are adopted. For veriflcation, an experimental power divider operating at 1.25/1.75GHz is implemented. The measured results exhibit a bandwidth of 44.3% with better than 15dB return loss and 18dB port isolation is achieved.

A Dual-Band Unequal Wilkinson Power Divider Using Asymmetric Coupled-Line

In this paper, we present a novel scheme of unequal Wilkinson power divider operating at two arbitrary frequencies. The proposed power divider consists of two isolation resistors, two output matching transformers and two cascading asymmetric coupled-lines, which are used to achieve unequal power division. To investigate the proposed asymmetric coupled structure, in- and anti-phase (c/π-mode) analysis is adopted, instead of conventional even/odd-mode analysis. And analytical design equations are derived based on the transmission line theory. It is found that both frequency ratio and power dividing ratio can be adjusted, respectively. As a typical example, an experimental power divider with the power ratio of 2 : 1 is designed, fabricated and measured. The measured results show good agreements with the simulated ones.

An Investigation of Quarter-Wavelength Square-Spiral Resonator and Its Applications to Miniaturized Bandpass Filters

In this paper, we investigate both quarter-wavelength square-spiral resonator and its application to miniaturized bandpass filters. Using the commercial simulation software, we examine the coupling coefficients and external quality factor of the proposed structure. With different combinations of the proposed resonators, four miniaturized bandpass filters are designed. The sizes of the designed filters are reduced by 96%, 96.7%, 96.6% and 94.8%, compared to the traditional square loop bandpass filter. It is also found that the first spurious passband of the filters is increased up to near three times the fundamental resonant frequency, and the rejection level around twice the fundamental resonant frequency is kept below 20 dB. To validate the proposed idea, four experimental filters are designed, simulated and fabricated. Measured results are in good agreement with the theoretical predictions.

Simplified N-Sided Irregular Polygonal Ground Plane Cloak Created with Oblique Layered Isotropic Dielectrics

Although different coordinate transformations could be utilized to design invisibility cloaks, in this work, we propose a straightforward way to design arbitrary-shaped ground plane cloak, in which only the y-coordinate is transformed in a uniform linear manner within the cloak area. Based on the proposed general way, an arbitrary N-sided irregular polygonal cloak can be designed, which is made up of N blocks, and each block only requires a simple homogeneous anisotropic material. To realize the proposed cloaks, layered grating systems are utilized to implement the blocks and demonstrate the overall performance of cloaking. Each grating system is constructed by two kinds of alternating isotropic dielectrics, and the alignment angles are determined by effective medium theory. Three parameter settings of the layered grating system are utilized for TM wave cloaking and hybrid wave cloaking. Each proposed makeup block of the N-sided polygonal cloak consists of alternating isotropic dielectric layers, thus can lead to an easy practical fabrication.

A Microstrip Patch Array with Aperture-Coupled Feeding for Ka-Band Applications

A Ka-band microstrip patch antenna array with aperture-coupled feeding is presented in this paper. For a single element antenna, an impedance bandwidth (return loss < -10 dB) of 2 GHz is achieved at the central operating frequency of 30 GHz. A 2times2 array and a 4times4 array are simulated, and larger array with more elements is theoretically estimated. Potential applications of the designed Ka-band patch array include the satellite digital communications.

Time domain integral equation methods for analyses of transient radiation and scattering problems

A stable solver of the time domain integral equation (TDIE) methods with quadratic B-spline temporal basis functions (TBFs) for analyses of transient radiation and scattering problems is proposed. This TBF permits consistent approximations of the induced currents and charges, leading to proper representations of the fields contributed by both the vector and scalar potentials. This TBF also has the least support width among all the polynomial basis functions of the same order, generating most possible sparse system matrices. Numerical examples show that the proposed scheme is stable and accurate.

A novel FSS based on hybrid boundary condition cavity

In this paper, we present a novel bandpass frequency selective surface (FSS) with low passband insertion loss and good frequency selectivity. Each periodic cell consists of a special cavity with hybrid perfect electric conductor (PEC) and perfect magnetic conductor (PMC) boundary conditions, which are formed by four common metallic vias and the complementary slots etched on both top and bottom surfaces. By using approximated method, the novel cavity is numerically investigated and the frequencies of the main resonant modes are obtained. It is found that a two-pole pass band with sharp roll-off can be achieved due to the proper combination of the cavity and slots. The frequency response of the proposed FSS is also demonstrated and shows its insensitivity to incident angles and polarization etc.