Dual-band High-temperature Superconducting Research Articles

Balanced Dual-Band HTS BPF With Controllable Frequency Ratio and Transmission Zeros Using Mixed Cross-Coupling

In this brief, a fourth-order balanced dual-band high temperature superconducting (HTS) bandpass filter (BPF) is presented based on modified stub-loaded resonators (SLRs). Firstly, the differential mode (DM) and common mode (CM) resonant characteristics of the modified SLRs are analyzed. Under DM operation, two types of mixed cross-coupling topologies are constructed by placing the spiral modified SLRs and their DM equivalent structures in an appropriate way. Then, a dual-band response with controllable center frequencies, bandwidths, and transmission zeros (TZs) is achieved. Under CM operation, an effective CM suppression circuit is proposed for improving the in-band CM suppression level. Finally, for verification, a fourth-order balanced dual-band HTS BPF with center frequencies of 3.494/4.797 GHz and insertion loss of 0.26/0.21 dB is designed and fabricated on MgO substrate with double-sided YBCO thin films. The measured results agree well with the simulated ones, and the BPF shows the attractive features of low insertion loss and good out-of-band rejection.

High-Order Balanced Dual-Band HTS BPF With Flexible Frequency Ratio and Sharp Rejection Skirts

In this article, a new class of high-order balanced dual-band high-temperature superconducting (HTS) bandpass filter (BPF) based on modified multimode stub-loaded resonators (SLRs) is presented. First, a detailed theoretical analysis of the multimode SLRs is provided to obtain insight into their frequency response characteristics under the differential-mode (DM) and common-mode (CM) operations. Specifically, the SLRs under the DM operation are designed to generate their second and third resonant modes in the two specified passbands, and they are sequentially cascaded by alternate <inline-formula> <tex-math notation="LaTeX">$J$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> inverters for sharp rejection skirts. Following that, the working mechanism of the CM rejection of the resonator is investigated for achieving good CM suppression performance for this filter. Finally, for experimental validation, an eighth-order prototype filter is designed and fabricated on the MgO substrate with double-sided YBa2Cu3Oy (YBCO) thin films. Good agreement between measured and simulated results is obtained, and the filter is at the same time with low insertion loss, flexible frequency ratio, sharp rejection skirts, and good CM suppression level.

A 14-Pole Dual-Band High Temperature Superconducting Filter Including Narrow Bandstop Notches

A 14-Pole Dual-Band High Temperature Superconducting Filter Including Narrow Bandstop Notches

Design of Dualband Bandpass High-Temperature Superconducting Filter With Group Delay Equalization

A novel dualband high-temperature superconducting (HTS) bandpass filter is proposed with group delay equalization for 5G emergency communication receivers with N41 and N79 bands in this paper. The dual-folded stub-loaded stepped impedance resonator (DSLSIR) is applied to realize dualband performance. The proposed DSLSIR has miniaturized circuit size and more design freedom to independently adjust the two designed center frequencies, comparing with other reported DSLSIRs. Two cross-coupling transmission lines are added at the top and bottom parts of the cascaded sixth-order filter with DSLSIRs to flatten the group delay of the passband at both bands. A dualband bandpass HTS filter etched on the YBCO superconducting material is fabricated to verify the proposed design method. The measurement is actualized at the temperature of 77 K to make YBCO microstrip lines perform superconducting features. The results show that the first center frequency is 2.595 GHz with 6.2% bandwidth for N41 band and 0.3 dB insertion loss while the second center frequency is 4.85 GHz with 2% bandwidth for N79 band and 0.4 dB insertion loss. Meanwhile, the group delays at the N41 and N79 bands keep 2 ns fluctuations in the 60% passband. The agreement between the measured and simulated results indicates that the proposed dualband bandpass HTS filter with low insertion loss, sharp roll-off skirt and flat group delay is a promising candidate for emergency communication receiver.

Compact narrowband high-order dual-band superconducting bandpass filters using stub-loaded double-folded resonators

Compact narrowband high-pole dual-band high-temperature superconducting (HTS) bandpass filters (BPF) have been developed that use newly developed stub-loaded double-folded microstrip resonators. The resonators have a weak coupling property that enables the distance between resonators to be reduced and that suppresses unwanted nonadjacent coupling. Moreover, it enables independent control of the resonant frequencies of the first and second passbands. Additional microstrip lines and a dual-feeding structure are introduced to enable flexible adjustment of the internal and external couplings of the two passbands. A prototype ten-pole dual-band HTS BPF operating at 1.5 and 2.0 GHz was designed and constructed. The filter for both passbands has a 1% fractional bandwidth and was fabricated using YBa2Cu3Oy thin film on an Al2O3 substrate. The measured frequency responses of the filter were in good agreement with the simulated ones. These results demonstrate that the compact filter has high selectivity, low insertion loss, and good stop-band rejection.

Design of High-Temperature Superconducting Dual-Band Filter With Multiple Transmission Zeros

A multiorder dual-band high-temperature superconducting (HTS) bandpass filter (BPF) with multiple transmission zeros (TZs) is designed in this paper. The theoretical characteristics of the introduction of TZs by the electric and magnetic mixed coupling and the cascade quadruplet (CQ) cross-coupling structures are analyzed, respectively. These two methods can be applied to the design of the multimode compact dual-band HTS BPF with controllable central frequency, bandwidth, and TZs. For demonstration, a Y-shape tunable resonator structure, which can simultaneously implement the internal electric and magnetic mixed coupling, and the external cross coupling are constructed to achieve the proposed dual-band BPF. The external quality factors required by the two passbands and the feasibility of independently adjusting the coupling strength between adjacent resonators are analyzed. Finally, a six-order dual-band HTS BPF with the center frequencies of 1490 (bandwidth of 40 MHz) and 2340 MHz (bandwidth of 80 MHz) is designed and fabricated on the double-sided YBCO/MgO/YBCO HTS thin films with the size of 17.2 mm × 14.7 mm (0.20 λg × 0.17 λg), and there are multiple of TZs located outside the two passbands, respectively. The out-of-band rejections are greatly improved to 70 and 80 dB due to these TZs, which fully exhibits the advantages of the proposed dual-band BPF. The measured results are in good agreement with the simulated ones.

Compact Dual-Band HTS Bandpass Filter Using Coplanar Waveguide Short-Circuited Stub-Loaded Ring Resonator

A compact coplanar waveguide (CPW) dual-band high-temperature superconducting (HTS) bandpass filter using a short-circuited stub-loaded ring resonator (SC-SLRR) is introduced in this paper. The equivalent circuit of the SC-SLRR is built and its resonant formulas are presented. The relationship between the parameters of electrical length and resonant performances are deduced. Resonant modes of the proposed resonators can be simultaneously excited and easily tuned for a dual-band application. To verify this methodology, a second-order CPW HTS dual-band bandpass filter operating at 2.36/4.93 GHz is designed. This filter is implemented on a 0.5-mm thick MgO wafer with a one-sided YBa 2 Cu 3 O 7 film, and it has the compact size of 0.146λg × 0.083λg. Measured results agree well with the simulated ones, which show that the minimum insertion losses of both bands are less than 0.15 dB.

Differential Dual-Band Superconducting Bandpass Filter Using Multimode Square Ring Loaded Resonators With Controllable Bandwidths

In this paper, a fourth-order dual-band high-temperature superconducting (HTS) differential bandpass filter (BPF) with controllable midband frequencies and bandwidths is developed by using modified multimode square ring loaded resonators (SRLRs). The differential-mode (DM) bisection and common-mode (CM) bisection of the modified SRLR are analyzed by using the even- and odd-mode method twice, and the corresponding resonant properties are obtained. With a proper design of the modified SRLR, two lowest DM resonances are chosen to construct two DM passbands with high in-band CM suppression. The DM resonances can be adjusted flexibly after adding tunable patches to the square ring. Meanwhile, the internal coupling between two modified SRLRs can be controlled separately by using two geometrical parameters. Consequently, the proposed dual-band BPF can achieve independent control of both the midband frequencies and the bandwidths of its two passbands. Moreover, a wideband CM suppression is realized by a combined use of an appropriately selected feeding structure and a frequency discrepancy technique. A fourth-order dual-band differential BPF is designed with two passbands operating at 2.325 and 4.900 GHz, respectively. The filter is fabricated using HTS YBCO thin films on a MgO substrate. Good agreement between the simulated and measured frequency responses are observed, verifying well the proposed structure and design method.

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.

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.

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 Quint-Mode Stub-Loaded Resonators

Two dual-band high-temperature superconducting (HTS) bandpass filters (BPFs) using quint-mode stub-loaded resonators are presented. The quint-mode resonator is formed by loading four open-circuit stubs in shunt. By properly adjusting the lengths of the resonator, three transmission zeros separate five resonant frequencies into two groups. The first three resonant frequencies form the first passband. The two other frequencies are combined to create the second passband. In addition, a novel approach is proposed to extract the external quality factor Qe based on the group delay of S21. A magnetic coupling is introduced to adjust external coupling to meet the desired external Qe. The first filter prototype is initially designed and implemented to verify the theory. Afterward, the second filter is constituted by introducing an additional half-wavelength resonator, resulting to improve the isolation between two desired passbands. Finally, two HTS BPFs are fabricated, and measured results agree well with theory.

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.

Dual-Band Superconducting Bandpass Filter Using Quadruple-Mode Resonator

A dual-band high-temperature superconducting (HTS) bandpass filter (BPF) using a quadruple-mode resonator is realized in this paper. The resonator consists of a half-wavelength uniform impedance resonator, an open stub in a symmetrical plane, and two spiral open stubs at the two sides of the symmetrical plane. Distinct characteristics of the quadruple-mode resonator are investigated by using even/odd mode theory, and the design graphs are given to analyze the dual-band filter. A dual-band HTS BPF with central frequencies of 1.8 GHz for GSM applications and 2.4 GHz for wireless local area network applications is designed using the proposed quadruple-mode resonator, which is fabricated by depositing YBCO films on a 0.5-mm-thick MgO substrate. Its size occupies only 13 mm × 17 mm. Measured results demonstrate that an insertion loss within the passbands is less than 0.25 dB. In addition, a transmission zero is achieved in-between two passbands, and two transmission zeros are realized in the upper stopband of the higher passband, which improve the skirt selectivity and stopband characteristics of the filter.

Design and performance of dual-band high temperature superconducting filter

In this paper, a dual-band high temperature superconducting (HTS) filter with 14-pole and 3 cross couplings is presented. The equivalent model, theoretical result, coupling matrix, and the simulated result of the filter are demonstrated. The desired filter is designed and fabricated using double-sided DyBa2Cu3O7 thin films on MgO wafer 2 inches in diameter and 0.5 mm in thickness. The filter has two passbands with frequencies 1920–1940 MHz and 1960–1980 MHz respectively, and insertion loss less than 0.2 dB. The measurement results show that the response of practical filters is in good agreement with that of simulated results and theoretical analysis, with the group delay variation being less than ±20 ns over 90% of the filter bandwidth for the two passbands.

Quarter-Wavelength Stepped-Impedance YBCO Resonators for Miniaturized Dual-Band High-Tc Superconducting Filters

A dual-band high-temperature superconducting (HTS) bandpass filter (BPF) is proposed for wireless local area network applications. Using quarter-wavelength stepped-impedance resonators, the designed filter can be miniaturized and shows a dual-band response. The simulation results show the dual-band feature of two passbands at 2.4 and 5.2 GHz, each with a minimum in-band insertion loss of about 0.02 dB. The filter was made out of patterned double-sided deposited YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> (YBCO) films integrated with a gold-coated housing. The realized HTS BPF shows two passbands at 2.41 and 5.24 GHz with minimum insertion losses of 0.86 and 1.97 dB, respectively. The measured results show a good HTS BPF performance. Moreover, the temperature-dependent center frequencies can be well described by the modified two-fluid model based formulas, indicating that the frequency shift in HTS BPF is dominated by the temperature dependence of the magnetic penetration depth.