Pin Wen

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.

Flexible CPW-Fed Fishtail-Shaped Antenna for Dual-Band Applications

A flexible fishtail-shaped antenna for WiMAX and X-band applications is presented in this letter. The proposed antenna is fed by a coplanar waveguide (CPW). Stepped-impedance lines that can provide smooth transitional impedance for improved impedance matching and broadband characteristics are also introduced. The antenna is printed on a 0.127-mm polytetrafluoroethene (PTFE) substrate and occupies a size of 25 × 50 mm 2. In the lower frequency band, the measured impedance bandwidth for | S11 | ≤ -10 dB is about 200 MHz from 3.4 to 3.6 GHz, while it is about 7 GHz from 7.4 to 14.4 GHz in the upper frequency band. In addition, the antenna demonstrates a low sensitivity to performance degradation due to bending effects, which makes it suitable for integration within portable devices.

Wideband and Low-Loss High-Temperature Superconducting Bandpass Filter Based on Metamaterial Stepped-Impedance Resonator

This paper presents a wideband and low-loss high-temperature superconducting (HTS) bandpass filter (BPF) using a composite right/left-handed (CRLH) stepped-impedance resonator (SIR). The filter resonates at 2.6 GHz for LTE2600 application. The structure is designed in an entirely printed circuit technology based on the CRLH theory and its equivalent circuit. For the same center frequency, fractional bandwidth and stop-band attenuation, the presented CRLH SIR BPF proves to surpass its conventional counterpart in terms of size without degradation in performance. The CRLH SIR BPF is also significantly more controllable in its dimensions and response due to the fact that more elementary parameters are available in the CRLH configuration. The proposed filter is simulated and measured, and the measurement results match well with the simulation results. Good properties of low in-band insertion loss, good out-band rejection, and compact size have been achieved and verified. Intermodulation distortion (IMD) and the transmission properties at different temperatures are used to investigate the nonlinearity of the HTS filter. IMD can also clarify the power-handling capability of the filter.

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.

Dual-Band High-Temperature Superconducting Hairpin-Resonator Bandpass Filter Based on Two Pairs of Nondegenerate Modes

In this letter, a compact dual-band high-temperature superconducting (HTS) hairpin-resonator bandpass filter based on a multimode resonator is proposed. This multimode resonator consists of two hairpin resonators loaded with a common T-shaped stub. The T-shaped stub excites one pair of nondegenerate modes for the inner hairpin resonator, whereas the combination of T-shaped stub and the inner hairpin resonator produces another pair of nondegenerate modes for the outer hairpin resonator. Moreover, the former generates the higher passband, and the latter produces the lower passband, which is controlled independently by the corresponding hairpin resonator. Finally, the proposed dual-band HTS filter was fabricated and measured. 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.

Band-Notched Ultra-Wideband Bandpass Filter Using Dual-Mode Resonator Loaded Slotline

In this article, a novel band-notched ultra-wideband (UWB) bandpass fllter based on hybrid microstrip/slotline structure is proposed. A quad-mode stubs-loaded slotline resonator is fed by two orthogonal microstrip lines and ultra-wideband bandpass characteristic is excited. A stub-loaded dual- mode microstrip resonator is externally loaded to the quad-mode slotline resonator, and a notched band with sharp roll-ofi characteristic is achieved. The circuit model for the dual-mode microstrip resonator loaded slotline is given and analyzed. The proposed fllter is designed and fabricated. Simulated and measured return losses are i12dB/i18dB and i18dB/i10dB in lower and higher passband. The return loss in the notched band is greater than 15dB.

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.