A new balanced dual-band bandpass fllter with strong common-mode rejection is presented in this paper. Common-mode rejection is provided by a section of a periodic microstrip difierential line that behaves as a low-pass fllter under common-mode operation. In contrast, the difierential line exhibits very good all-pass behavior under difierential mode operation. This structure is combined with a difierential dual-band bandpass fllter based on embedded resonators. Simulations and experiments conflrm that the combined structure has good common-mode rejection within the passbands of the dual-band difierential fllter.

/pdf/dual-band-differential-filter-using-broadband-common-mode-5cchfj0d94.pdf

Dual-Band Differential Filter Using Broadband Common-Mode Rejection Artificial Transmission Line

A novel design of planar dual and triple narrow-band bandstop fllter is presented by adopting the proposed meandered slot defected microstrip structure (MS-DMS) and the simplifled spiral microstrip resonator (SSMR). Through this design, the stopbands of the dual- and triple-band bandstop fllters can be individually controlled and the improved spurious responses are achieved. First, the fundamental and the flrst spurious resonances of the MS-DMS and SSMR are analyzed to provide the design rules. Then, by utilizing the prominent stopband of the MS-DMS and the stopband produced by the SSMR coupled to main microstrip line, a dual narrow- band bandstop fllter is constructed before its design procedure is outlined. Based on above investigations, a triple narrow-band bandstop fllter is implemented by inserting extra SSMRs to another side of the main microstrip line of the dual-band fllter to generate a new stopband. To verify the aforementioned design concepts, a dual and triple narrow-band bandstop fllter are designed, simulated and tested. Both the simulation and measurement indicate that the fabricated fllters exhibit good stopband/passband performance and improved flrst spurious resonance. Moreover, these fllters are simple to design and quite compatible with planar fabrication technique, making them very attractive for practical applications.

/pdf/design-of-planar-dual-and-triple-narrow-band-bandstop-3v3u17iuih.pdf

Design of Planar Dual and Triple Narrow-Band Bandstop Filters with Independently Controlled Stopbands and Improved Spurious Response

Coupled-line and coupled three-line resonators are pro- posed to design dual-wideband bandpass fllters. Compared with the shorted and open stubs shunt at the same locations of the main line, in addition to saving the circuit area, these resonators provide alter- native ways to the design of dual-wideband fllters, with larger possible bandwidths and difierent frequency ratio of the two center passbands. The geometric parameters of the coupled-line and the coupled three- line structures are determined by deriving their equivalent circuits to a shunt open stub in parallel connection with a shunt shorted stub. To extend the upper stopband, a cross-shaped admittance inverter is devised to play the role of the 90-degree transmission line section at the center frequency and to create transmission zeros at the spurious passbands, so that the upper stopband of the fllter can be extended. It is a quarter-wave section with two open stubs of unequal lengths shunt at its center. For demonstration, two dual-wideband bandpass fllters operating at 900/1575MHz and 900/2000MHz are fabricated and measured. Measured results of the experimental circuits show good agreement with simulated responses.

/pdf/dual-wideband-bandpass-filters-with-extended-stopband-based-4fcwrrd6k3.pdf

Dual-Wideband Bandpass Filters with Extended Stopband Based on Coupled-Line and Coupled Three-Line Resonators

A novel dual-band filter based on split-ring resonators (SRRs) and double-slit complementary SRRs is presented. The size of the filter is small and the two passbands can be individually designed. The basic cell of the filter is presented and analyzed, and then the multistage dual-passband filter is achieved by cascading basic cells. The design graphs for external quality factors of the resonators at input and output stages and the coupling coefficient between the adjacent resonators are constructed. The design graphs are utilized to determine the proper geometric parameters of each filter stage for a given filter specification. As an example, a prototype three-stage Chebyshev filter with a fractional bandwidth (FBW) of 2% at 0.9 GHz and a FBW of 3% at 1.3 GHz is demonstrated. The prototyped filter has an equal ripple of 0.4 dB at both passbands. The measurements of the prototyped filter agree well with the simulation results. The center frequencies and the FBWs of the two passbands of the prototyped filter can be individually designed with more flexibility compared to dual-band filters that utilize resonances of higher order modes. The overall size reduction of the proposed filter can be as high as by a factor of 3 compared to that of edge-coupled microstrip filters.

Dual-Bandpass Filters With Individually Controllable Passbands

A novel miniaturized dual-band bandpass filter using two sets of short stub-loaded dual-mode resonators (SSLDMRs) is presented in this paper. It has been implemented with two parallel transmission paths for two specific passbands, which is convenient to design single-band independently. Each of them using the proposed SSLDMR results in respective passband. Meanwhile, it is easy to control the bandwidth of each passband by changing even-mode resonant frequency of the corresponding SSLDMR. Moreover, one set of SSLDMRs is embedded inside of the other one for the size compactness, which can further miniaturize the dimensions of the overall structure. To improve the selectivity and achieve a high out-of-band rejection, the source-load coupling is utilized to create four transmission zeros on either side of both passbands. The simulated and measured results are presented and show good agreement.

Miniaturized Dual-Band Bandpass Filter using Short Stub-Loaded Dual-Mode Resonators

A novel compact dual-band bandpass fllter using tri- section stepped impedance resonators (SIRs) is presented for Wireless Local Area Network (WLAN). SIRs and one stub between parallel couple line are employed to realize two satisfactory passbands. Meanwhile, one transmission zero is generated between the two passbands to achieve a high out-of-band rejection. Simulated results show that two central frequencies are located at desired 2.4 and 5.2GHz with 3dB fractional bandwidths of 6.3% and 3.4% respectively. The measured results are in good agreement with the simulated ones.

/pdf/compact-dual-band-bandpass-filter-using-folded-sir-with-two-2n7u1wz19f.pdf

Compact dual-band bandpass filter using folded sir with two stubs for wlan

The utility model relates to a miniaturized built-in mobile phone antenna with a triband characteristic. The antenna takes the shape of cuboid; a solid support medium of the cubic antenna is arranged in the antenna; a metal radiator of the antenna is coated and etched on the upper, the lower, the front and the rear continuous outer surfaces of the solid support medium in a bending manner; the left and the right outer surfaces are not coated with any metal coating; the metal radiator is formed by six metallic sections; and the antenna adopts a 50 ohm coaxial cross-feeding manner to feed. The miniaturized built-in mobile phone antenna has the advantages of simple structure, easiness in processing, high processing precision and low processing cost; and compared with a conventional built-in mobile phone antenna, the novel built-in antenna provided by the utility model has not only compact volume favorable for both miniaturization and ultra thinness of a mobile phone, but also good triband characteristic under the premise of ensuring that the performance index meets the practicability.

Xiaohuan Wu

Papers

Compact dual-band bandpass filter using folded sir with two stubs for wlan

Miniaturized built-in mobile phone antenna with triband working characteristic