Superconducting Bandpass Filter Research Articles

K-band dual-band superconducting bandpass filter using uneven coupled SIRs and stub-loaded combining network

K-band dual-band superconducting bandpass filter using uneven coupled SIRs and stub-loaded combining network

Miniaturized Quadband High-Temperature Superconducting Bandpass Filter with a Wide Frequency Ratio

This paper presents a miniaturized quadband high-temperature superconducting (HTS) bandpass filter based on a multistub-loaded resonator. Owing to the symmetrical structure of the proposed resonator, the odd- and even-mode analysis method can be used to derive its resonance frequencies. First, the frequency ratio between passbands may be significantly changed by adjusting the impedance ratio and fold spacing of the resonator. Moreover, the proposed filter exhibits well-controlled center frequencies and bandwidths for the four passbands, resulting in a considerably enhanced design possibility of quadband bandpass filters. A low insertion loss within each band is obtained using HTS technology. Additionally, the proposed filter was etched on an MgO substrate with a thickness of 0.5 mm and combined with YBCO thin films for demonstration. The results obtained were highly consistent with those of the simulation, validating the effectiveness and viability of the proposed method.

A High-Temperature Superconducting Bandpass Dual-Mode Filter with Tunable Relative Bandwidth and Center Frequency.

This study proposes a high-temperature superconducting (HTS) bandpass filter with a continuously tunable bandwidth and center frequency. The proposed filter combines several gallium arsenide varactors and a dual-mode resonator (DMR). The even and odd modes of the DMR can be tuned simultaneously using a single bias voltage. The capacitive value of varactors in the circuit is tuned continuously under continuous voltage and frequency tunability. External couplings and the interstage can be realized using an interdigital coupling structure; a fixed capacitor is added to the feeder to improve its coupling strength. A low-insertion loss within the band is obtained using HTS technology. Additionally, the proposed filter is etched on a 0.5 mm-thick MgO substrate and combined with YBCO thin films for demonstration. For the as-fabricated device, the tuning frequency range of 1.22~1.34 GHz was 9.4%; the 3-dB fractional bandwidth was 12.95~17.39%, and the insertion loss was 2.28~3.59 dB. The simulation and experimental measurement results were highly consistent.

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 Compact Four-Pole Tunable HTS Bandpass Filter at VHF Band

This article presents a compact, low loss, wide tuning range, high temperature superconducting (HTS) bandpass filter at very high frequency (VHF) band. The filter consists of four zigzag open-loop resonators loaded with gallium arsenide (GaAs) varactors as tuning elements. Each resonator is biased independently. The filter circuit is fabricated on a 3-inch HTS thin film deposited on a LaAlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrate. The filter demonstrates a frequency tuning range of 73.2-118 MHz, which is a tunability of 48%, an insertion loss of 0.6-2.2 dB, and a 3-dB fractional bandwidth of 3.2-4.3%. Besides, the return loss of the filter is better than 16.6 dB in the whole tuning range, with slight adjustment of bias voltages for different resonators.

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 balanced tri‐band superconducting band‐pass filter using double square ring loaded resonators

This article presents a balanced tri-band superconducting band-pass filter (BPF) with controllable center frequencies (CFs) and fractional bandwidths (FBWs) using novel double square ring loaded resonators (DSRLRs). Due to the symmetrical structure of the proposed DSRLR, the differential mode (DM), and common mode (CM) equivalent circuits of the resonator are analyzed by using even- and odd-mode methods, and the resonant characteristics can also be obtained. With the proper design of the proposed DSRLR, the first three DM resonant frequencies are utilized to construct the three DM passbands, and their CFs can be adjusted by changing the lengths of the corresponding stubs. Then, the internal coupling between resonators can be controlled independently by the additional capacitive loading microstrip and the interdigital coupling structure. In addition, the so-called frequency dispersion technique is used to enhance CM suppression in the proposed balanced tri-band BPF by loading additional multiple stubs on the symmetry plane. Consequently, the proposed tri-band BPF can realize controllable CFs and FBWs with broadband CM suppression. Prototype balanced filters with CFs of 1.7/2.45/3.4 GHz and FBWs of 2.9%/3.2%/1.8% were designed, manufactured, and measured for verification. The experimental results agree well with the simulated ones.

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.

Balanced Dual-Band Superconducting Filter Using Stepped-Impedance Resonators With High Band-to-Band Isolation and Wide Stopband

A balanced dual-band and wide-stopband high-temperature superconducting (HTS) bandpass filter (BPF) with deep stopband rejection is designed using modified stepped impedance resonators (SIRs) in this brief. The center frequencies of the two differential-mode (DM) passbands can be controlled by adjusting two electrical length ratios of the proposed SIR, while keeping the third spurious frequency far away for wide-stopband design. An inherent common-mode (CM) suppression can also be obtained due to the discriminating CM resonant frequencies different from the DM ones. Multiple transmission zeros (TZs) are achieved to realize high passband selectivity and enhanced DM stopband by multipath coupling and shunt stubs loaded on the I/O ports. The proposed balanced dual-band filter operating at 1.78/4.0 GHz is eventually fabricated using HTS YBCO thin films on a MgO substrate, which can significantly lower the insertion losses. The circuit was measured at the temperature of 77 K, which shows maximum insertion losses of 0.42/0.37 dB and a DM stopband of 5.0f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sup> with 40-dB attenuation, respectively.

Wideband and wide stopband superconducting bandpass filter using asymmetric stepped‐impedance resonators connected to open stub

Wideband and wide stopband superconducting bandpass filter using asymmetric stepped‐impedance resonators connected to open stub

Sharp-selectivity in-line topology low temperature superconducting bandpass filter for superconducting quantum applications

This paper presents a new class of sharp-selectivity low-temperature superconducting filter that incorporates lumped element resonant couplings. Dependent on a novel synthesis approach, the proposed filter exhibits great advantages such as: (1) a very simple in-line topology (without any cross coupling), (2) extremely compact size based on lumped inductor-capacitor (LC) elements, and (3) multiple transmission zeros (TZs) independently generated and controlled (via each resonant coupling). To facilitate the physical implementation, a group of lumped element circuit models are detailed, where series LC units are adopted for both the resonators and the resonant couplings. Considering an in-line topology here, the entire filter layout is then designed by cascading the lumped models one after another. For verification, a 5th-order bandpass filter centered at 5 GHz, with 500 MHz bandwidth and 3 TZs, is designed, simulated, and tested at cryogenic temperature (4.2 K). Moreover, preliminary simulations of the presented filter in series with an on-chip rapid single-flux-quantum microwave pulse generator are discussed for superconducting quantum applications.

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.

Miniaturized High Temperature Superconducting Bandpass Filter Based on D-CRLH Resonators

In this paper, a novel high temperature superconducting (HTS) dual composite right/left-handed (D-CRLH) resonator is proposed, which is constructed by microstrip spiral coupled lines and microstrip high-impedance lines. Moreover, by using an equivalent circuit model and a admittance matrix method, the characteristics of the D-CRLH resonator is obtained and analyzed, which makes it suitable for implementing the miniaturized high-performance filter. For demonstration, a second-order D-CRLH bandpass filter is designed on a 0.5-mm-thick MgO wafer with double sided 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">7</sub> films. Multitransmission zeros are obtained in the stopband of the filter, improving the selectivity and stopband characteristics of the filter. Good agreement between the measurements and design goals can be observed.

Millimeter-Wave Ultra Wideband Multilayer Superconducting Filter

Ultra wideband (UWB) millimeter-wave filters are needed in the realization of analog front ends of superconductor digital receivers. In this paper, a multi-layer niobium-based superconducting bandpass filter operating over the frequency range 30-60 GHz is demonstrated for the first time. The filter is realized in a co-planar waveguide structure, where cross-overs in the multilayer structure are employed to reduce the filter size. The paper also illustrates how these cross-overs can be utilized to fine tune the filter performance. An 8-pole superconductor niobium-based filter with a size of 0.88 × 2.2 mm designed with a center frequency of 45 GHz and a bandwidth of 30 GHz has been developed, fabricated, and tested. The results demonstrate the feasibility of monolithically integrating UWB millimeter-wave filters with a superconductor receiver on single-chip.

Superconducting Filter Based on Split-Ring Resonator Structures

A design of high-temperature superconducting bandpass filter based on split-ring resonator (SRR) structures is presented in this paper. The SRR has been considered as a classical element for metamaterials and exhibits characteristics of subwavelength resonator, hence can aid in the compact design of filters. Filter has been simulated and optimized using Sonnet software. The measured results of the filter have good consistency with the simulated results and show good band pass characteristics. The center frequency of the filter measured at 70 K was 2.515 GHz, the rectangle coefficient was 1.22, and the insertion loss was 0.1 dB at the center frequency.

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.

Novel Tri-Band High-Temperature Superconducting Bandpass Filters Using Asymmetric Shunted-Line Stepped-Impedance Resonator (SLSIR)

In this paper, a tri-band high-temperature superconducting (HTS) bandpass filter (BPF) is proposed with a pair of asymmetric shunted-line stepped impedance resonators (SLSIRs). Compared with the conventional SIRs, the proposed asymmetric SLSIR has more degrees of freedom in controlling multi-mode operating characteristics. Moreover, design graphs for the relationship of electric characteristic parameters and the resonant frequency ratio are built and applied to multiband device design. For demonstration, a two-order tri-band HTS BPF is well designed with center frequencies of 1.575/2.4/3.5 GHz. The external quality factor and the coupling coefficient have also been analyzed to satisfy the bandwidth of the BPF. The designed filter is fabricated on the YBCO superconducting material and measured under superconducting conditions (at the temperature of 77 K). The measurement results are in good agreement with the simulation results, indicating that the insertion loss of the three passbands is about 0.1 dB, showing the advantage of in-band insertion loss.

A compact high-temperature superconducting band-pass filter with wide upper stopband

A novel hair-pin resonator(NHR) composed of interdigital capacitor and fractal resonator is developed, which not only has compact in size but also has no harmonics up to three times of the fundamental frequency. The results show that the equivalent capacitance introduced by the interdigital capacitor at the conventional hair-pin resonator terminal plays a major role in suppressing the spurious harmonics, whereas the equivalent inductance has no improved harmonic rejection ability. A miniature five-pole wide-band HTS bandpass microstrip filter has been designed and fabricated with this NHR on a double-sided MgO-based DBCO thin film. Measurement at 79.4K shows that the fabricated HTS filter has less than 0.11 dB insertion loss and better than 20 dB return loss in the passband, and an ultra high spurious passband at about 3.3f0. Moreover, the simulated and measured results are found in excellent agreement in wideband response.