Baoping Ren

Compact and High Selectivity Tri-Band Bandpass Filter Using Multimode Stepped-Impedance Resonator

In this letter, a miniaturized tri-band bandpass filter (BPF) using a multimode stepped-impedance resonator (SIR) with a 0 ° tapped-feed structure is presented. The odd- and even-mode fundamental resonant frequencies and the first high-order resonant frequencies of the SIR are utilized to generate dual-mode dual-band response and the tapped side-coupled feed-lines construct an additional passband avoiding occupying extra size. Owing to the 0 ° tapped-feed structure and the intrinsic characteristics of the SIR, multiple transmission zeros are created to improve the selectivity of the filter. The bands of the designed tri-band BPF are located at 1.57 GHz (GPS application), 3.5 GHz (WiMAX application) and 5.8 GHz (WLAN application). Good agreement between the simulated and the measured results is observed.

Compact Dual-Band Bandpass Filter Using Quadruple-Mode Square Ring Loaded Resonator (SRLR)

A compact quadruple-mode square ring loaded resonator (SRLR) is proposed in this letter. Distinct mode splitting characteristics of the quadruple-mode SRLR are investigated and explained by using even- and odd-mode analysis. It results to excite four resonant modes which are applied to produce two pairs of transmission poles for dual-band bandpass filter (BPF) design. Based on the unique characteristics of the proposed SRLR, a miniaturized dual-band BPF operating at 2.45 GHz and 5.20 GHz for WLAN applications was designed and fabricated. Multiple transmission zeros are generated to improve the selectivity of the filter. Measurements are in good agreement with the simulations. Also, the circuit size occupies only 0.11λg×0.23λg, where λg is the guided wavelength at the center frequency of the first passband.

Quad-Band High-Temperature Superconducting Bandpass Filter Using Quadruple-Mode Square Ring Loaded Resonator

In this paper, a compact quad-band high-temperature superconducting (HTS) bandpass filter using a quadruple-mode square ring loaded resonator (SRLR) is introduced. The even- and odd-mode method is applied to investigate the equivalent circuits of the proposed quadruple-mode SRLR. The design graphs for the relationship of the parameters of electrical length and resonance performances are then set up. Based on the analysis above, four allocated resonant modes can be simultaneously excited and easily tuned. Meanwhile, multi-transmission zeros are created due to the different propagation paths of the square ring structure. Signal-interference theory is also adopted to explain the generating mechanism of transmission zeros. Moreover, a meander coupled-line technique is realized to adjust one uncertain resonant frequency to meet the target specifications of the designed quad-band filter. To verify this methodology, a second-order microstrip HTS filter operating at 2.45/3.5/5.2/5.8 GHz for wireless local area networks and worldwide interoperability for microwave access potential applications is designed using two quadruple-mode SRLRs. The quadruple-mode SRLRs are coupled with a pseudo-interdigital coupling structure for achieving the desired coupling degree conveniently, which also miniaturize the circuit size. This filter was fabricated on a 2-in-diameter 0.5-mm-thick MgO wafer with double-sided YBa2Cu3Oy thin films. The filter component was measured at the temperature of 77 K. Measured results agree with the theoretical results and show that the insertion losses in passbands are less than 0.3 dB, which exhibit superiority in midband insertion loss.

Dual-band high-temperature superconducting metamaterial structure based on multimode split ring resonator

In this Letter, a dual-band superconducting metamaterial structure with improved performance based on the proposed multimode split ring resonator (SRR) is proposed, which is constructed by two dual-mode SRRs and a high-impedance transmission line component. Also, its properties and equivalent circuit models are investigated by even- and odd-mode analysis. The mechanism producing four transmission zeros is discussed. To verify this design methodology, the dual-band superconducting metamaterial structure is designed and fabricated with a compact size of 10.6 mm × 13.75 mm. The insertion losses at each passband are 0.1 dB and 0.09 dB, respectively. Finally, measured results have a good agreement with simulations.

Compact Dual-Band HTS Bandpass Filter Using Spirally Asymmetric Stepped-Impedance Resonators

In this paper, a compact dual-band high-temperature superconducting (HTS) bandpass filter (BPF) is constructed by spirally asymmetric stepped-impedance resonators (SIRs) and a pair of parallel-coupled feed lines. The resonant characteristics of spirally asymmetric SIRs with one step discontinuity are investigated in the dual-band BPF design. Owing to its intrinsic characteristics and the multipath propagation effect, multiple transmission zeros are created to improve the selectivity of the passband and the rejection level of stopband. For demonstration purposes, a compact HTS filter operating at 2.4/5.8 GHz for wireless local area networks is fabricated. Measured insertion losses at each passband are 0.12 and 0.18 dB, respectively. A good agreement between the measurements and the simulations is observed, which verifies the circuit design methodology. Finally, the temperature dependence and the input-power dependence of microwave nonlinear properties of the dual-band HTS filter at each passband are also measured and analyzed. Measured results have a good agreement with simulations.

Dual-Band High-Temperature Superconducting Bandpass Filter Using Dual-Mode Hairpin Ring Resonator

A compact dual-band high-temperature superconducting (HTS) bandpass filter using a novel hairpin ring resonator (HRR) is presented in this paper. The proposed HRR that provides two controllable resonant modes can be applied to construct dual-band frequency response conveniently. The resonance mechanism of modes and coupling property between resonators are well investigated. Then, four identical HRRs are cascaded for achieving a high-performance dual-band filter. Finally, a fourth-order HTS filter centered at 1.9 and 2.6 GHz is successfully designed and fabricated on MgO substrate with YBCO thin films. The obtained filter has a compact size (occupies only 17.6 mm × 14 mm). The measured results show a high performance and agree well with the simulated ones.

Harmonic-Rejection Compact Bandpass Filter Using Defected Ground Structure for GPS Application

A miniaturized bandpass filter (BPF) using defected ground structure (DGS) resonator with the characteristic of harmonic rejection is developed in this paper. The second and third harmonics of the proposed BPF are rejected by the characteristic of stepped-impedance DGS resonator. Moreover, open stubs are established so that two adjustable transmission zeros can independently be created to extend the stopband and improve the rejection level. Finally, a second-order BPF, centered at 1.62 GHz with a stopband extended up to 5.6 GHz and a rejection level better than 20 dB, is designed and implemented for GPS application. A good agreement between simulation and measurement verifies the validity of this design methodology.

Quad-Band CPW-Fed Monopole Antenna Based on Flexible Pentangle-Loop Radiator

A novel low-profile monopole antenna fabricated on flexible substrate based on a pent angle-loop radiator is presented and investigated in this letter. The proposed antenna is designed to operate at GPS L2/Bluetooth/WiMAX/wireless local-area network frequency bands. To maintain the small size of the antenna element, an improved pent angle loop is adopted and the higher order modes are also utilized. Also, a pair of symmetrical V-shaped parasitic radiators and a modified rectangular ground plane of the coplanar-waveguide feeding structure are used to improve impedance matching at higher bands. The proposed antenna is fabricated on flexible substrate which can be easy to integrate in wireless systems. Its experimental results shows good agreement with the simulated results.

High-Order Dual-Band Superconducting Bandpass Filter With Controllable Bandwidths and Multitransmission Zeros

In this paper, a compact dual-mode hairpin ring resonator (HRR) with two controllable resonances is proposed to design high-order dual-band high-temperature superconducting (HTS) bandpass filters. Its noncoupled dual-mode resonant characteristics and the mechanism for inherent transmission zero (TZ) production are studied. Moreover, a general dual-path coupling scheme is introduced for high-order coupling realization and applied to the third-order and eighth-order dual-band filter design. Also, two coupling structures for the adjacent HRRs with different orientations are proposed to excite TZs between the passbands for high selectivity. Besides, dual-parallel input–output feeding structure is adopted to tune the external quality factors of the dual-mode HRR individually so that the two passband are realized easily using high-order structure. For demonstration, an eighth-order dual-band HTS filter both operating at 1.9 and 2.6 GHz for mobile communications application are designed and analyzed. Compared with the third-order one, the selectivity of the eighth-order filter has at least 4.2 times improvement and five TZs are produced for high band-edge selectivity. Finally, the eighth-order dual-band filter is fabricated on MgO substrate with YBCO thin films. Measured results agree well with the simulations and show the excellent performance with 0.12-dB minimum insertion loss and better than −75-dB rejection level up to 5 GHz. In addition, the nonlinear characteristics of the fabricated HTS filter is observed by experiment, which shows the temperature dependence of filter center frequency performance and microwave insertion loss.

Design of High-Temperature Superconducting Wideband Bandpass Filter With Narrow-Band Notch Resonators for Radio Telescope Application

This paper presents a compact wideband bandpass filter (BPF) integrating with two narrow-band notch resonators, for preventing the wideband communication system from interfering. The wideband filter adopts an asymmetric stub-loaded multimode resonator to obtain a bandwidth of 66.7%, with excellent passband fluctuation. In addition, two multiloop resonators are used to implement a 0.56% narrow-band. To illustrate its usefulness, a high-temperature superconducting wideband BPF with built-in narrow-band notch resonators is designed. It is fabricated on 20.8 mm × 16.15 mm YBCO films deposited on a 0.5-mm-thick MgO substrate with a relative permittivity ϵr of 9.78. The proposed wideband filter works at L-band, i.e., 1–2 GHz, and the return loss is greater than 19 dB. The notch-band resonator centered at 1.805 GHz provides more than 25 dB maximum attenuation for avoiding interferences from the global system for mobile communication. Finally, the circuit is measured, and the results agree well with the simulations.