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SCIENTIA SINICA Informationis, Volume 50 , Issue 12 : 1961(2020) https://doi.org/10.1360/SSI-2019-0199

Balanced dual-band superconducting filter using square ring loaded resonators with ultra-low insertion loss and common-mode noise suppression

More info
  • ReceivedSep 15, 2019
  • AcceptedNov 19, 2019
  • PublishedOct 21, 2020

Abstract

In this paper, a multi-mode square ring loaded resonator (SRLR) comprising a full-wavelength ring resonator and six open stubs is introduced. The resonant characteristics are discussed and analyzed using differential-mode (DM) and common-mode (CM) equivalent circuits. Compared to the conventional design, the proposed SRLR involves two advantageous modifications for high-order balanced structure. First, two pairs of open stubs on the four corners of the ring resonator provide more flexible control of the internal coupling between two SRLR units under DM excitation. In addition, the shorted H-shaped resonator is compact, which makes proposed structure suitable for high-order filter design with desired operating frequency and bandwidth. Second, one pair of open stubs is added to the ring resonator along the horizontally symmetric plane. We found that the proposed SRLR provides more design freedom for CM noise suppression without extra components or defected ground structure. In addition, the proposed SRLR topology structure is folded to avoid large circuit occupation. Based on our analyses, a fourth-order balanced dual-band bandpass filter was designed with two passbands operating at 2.2 GHz and 3.5 GHz with corresponding in-band insertion loss of 0.1 dB and 0.12 dB, respectively. The filter was fabricated using high-temperature superconductor (HTS) YBCO thin films on an MgO substrate. Good agreement between simulated and measured frequency responses was observed, which verifies the proposed structure and design method.


Funded by

国家自然科学基金重点项目(U1831201)

国家重点研发计划(2017YFE0128200)

陕西省国际科技合作计划项目(2019KW-003)

江西省自然科学基金重点项目(2017ACB20019)


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  • Figure 1

    (Color online) (a) Layout of the proposed multi-mode SRLR; (b) DM equivalent circuit; (c) CM equivalent circuit

  • Figure 2

    (Color online) (a) H-shaped DM equivalent circuit, its (b) odd-mode and (c) even-mode resonators

  • Figure 3

    (Color online) The first two DM resonant frequencies $f_{d1}$ and $f_{d2}$ versus $\theta_1$ and $\theta_2$ under condition of $\theta_2$ + $\theta_3$ = 90$^{\circ}$

  • Figure 4

    (Color online) (a) CM equivalent circuit, its (b) odd-mode and (c) even-mode resonators

  • Figure 7

    (Color online) Configuration of the proposed fourth-order balanced dual-band BPF

  • Figure 8

    (Color online) Coupling diagram of the balanced dual-band filter

  • Figure 9

    (Color online) (a) Proposed SRLR; (b) folded SRLR; (c) $S_{21}$ magnitude of the folded SRLR under DM and CM excitations

  • Figure 10

    (Color online) Coupling coefficients $M_{ij}$ as a function of (a) coupling gap g, where s= 0.56 mm or (b) coupling space s, where g= 0.16 mm

  • Figure 11

    (Color online) (a) The external quality factors Q$_e$ as a function of coupling length $L_{f1}$, where L$_{f2}$ = 1.95 mm and $w_{f}$ = 0.2 mm; (b) the external quality factors Q$_e$ as a function of coupling length L$_{f2}$, where $L_{f1}$ = 4.05 mm and $w_{f}$ = 0.2 mm

  • Figure 12

    (Color online) Simulated DM (${\rm~S}_{\rm~dd11}$ and ${\rm~S}_{\rm~dd21}$) and CM (${\rm~S}_{\rm~cc21}$) responses of the fourth-order balanced dual-band filter in Figure 7

  • Figure 13

    (Color online) (a) Two types of folded multi-mode SRLR; (b) their CM resonances

  • Figure 14

    (Color online) Configuration of the proposed balanced dual-band BPF with two dissimilar types of multi-mode folded SRLRs

  • Figure 15

    (Color online) Simulated results of the proposed balanced dual-band filter. (a) CM response (${\rm~S}_{\rm~cc11}$ and ${\rm~S}_{\rm~cc21}$) and (b) DM response (${\rm~S}_{\rm~dd11}$ and ${\rm~S}_{\rm~dd21}$)

  • Figure 16

    (Color online) Photograph of the fabricated fourth-order balanced dual-band HTS filter

  • Figure 17

    (Color online) Measurement and simulation results of the proposed filter. (a) CM response; (b) DM response

  • Figure 18

    (Color online) The enlarged scale of measurement and simulation results of the two passbands. (a) Passband 2.2 GHz; (b) passband 3.5 GHz

  • Table 1   Geometric parameters of the SRLR in Figure (b) (mm)
    Parameter Value Parameter Value Parameter Value Parameter Value
    L$_1$ 8.6 L$_5$ 0.875 L$_9$ 1.1 L$_{\textit{s}1}$ 0.55
    L$_2$ 1.6 L$_6$ 1.1 L$_{10}$ 3.2 L$_{\textit{s}2}$ 0.48
    L$_3$ 1.9 L$_7$ 2.125 L$_{11}$ 0.3 w$_1$ 0.3
    L$_4$ 1.6 L$_8$ 0.7 L$_{12}$ 1.75 w$_1$ 0.5
  • Table 2   Geometric parameters of filter in Figure (mm)
    Parameter Value Parameter Value Parameter Value Parameter Value
    L$_1$ 8.6 L$_5$ 0.875 L$_9$ 1.1 L$_{\textit{s}1}$ 0.55
    L$_2$ 1.6 L$_6$ 1.1 L$_{10}$ 3.2 L$_{\textit{s}2}$ 0.48
    L$_3$ 1.9 L$_7$ 2.125 L$_{11}$ 0.3 w$_1$ 0.3
    L$_4$ 1.6 L$_8$ 0.7 L$_{12}$ 1.75 w$_1$ 0.5
    s$_{12}$ 0.48 s$_{23}$ 0.55 s$_{34}$ 0.48 g$_{12}$ 0.08
    g$_{23}$ 0.15 g$_{34}$ 0.08 $L_{f1}$ 4.05 L$_{f2}$ 2.89
  • Table 3   Comparison of the proposed filter and the referenced works
    Ref. Center frequency (GHz)FBW (%) IL (dB) Circuit size ($\lambda\textit{g}\times\lambda\textit{g}$) Filter order In-band CM (dB) CM rejection level (center frequency $f_{d0}$)
    [9] 2.4/5.0 16.4/8.6 1.78/2.53 0.50 $\times$ 0.70 4 32/32 27 dB up to 3.27$f_{d0}$
    [10] 2.46/5.56 16.3/6.7 1.9/1.9 0.31 $\times$ 0.41 4 36/31 35 dB up to 7.06$f_{d0}$
    [11] 2.4/3.57 7.5/6.61 0.87/1.9 0.50 $\times$ 0.20 2 24/38 18 dB up to 1.88$f_{d0}$
    [12] 9.23/14.1 2.8/5.6 2.9/2.7 2.70 $\times$ 1.27 2 48/40 20 dB up to 1.65$f_{d0}$
    [13] 0.9/2.49 3.6/2.1 2.67/4.65 0.67 $\times$ 0.32 2 30/40 20.2 dB up to 5.56$f_{d0}$
    [14] 2.5/5.6 8.0/5.0 1.29/1.97 0.15 $\times$ 0.27 2 34.7/24.1 9.1 dB up to 2.8$f_{d0}$
    [15] 1.8/5.8 12.2/4.5 1.2/2.0 0.37 $\times$ 0.28 2 35/26 12 dB up to 4.7$f_{d0}$
    [16] 2.45/5.25 9.8/4.6 2.4/2.82 0.38 $\times$ 0.42 2 53/45 21.7 dB up to 3.64$f_{d0}$
    [17] 2.6/5.8 10.4/3.6 1.1/2.15 0.26 $\times$ 0.34 2 62/48 15 dB up to 3.07$f_{d0}$
    [18] 3.58/5.6 5.8/3.4 1.1/1.8 0.25 $\times$ 0.47 2 25/17 17 dB up to 1.82$f_{d0}$
    [27] 2.33/4.9 3.9/4.9 0.13/0.16 0.32 $\times$ 0.31 4 63/40 20 dB up to 2.58$f_{d0}$
    This work 2.2/3.5 2.7/3.8 0.1/0.12 0.50 $\times$ 0.33 4 74.9/67.4 20 dB up to 3.64$f_{d0}$