Yongbo Bian

A Compact HTS Duplexer for Communication Application

A compact L-band high temperature superconducting (HTS) microstrip input duplexer for satellite communication application has been developed. The duplexer has two output channels with center frequencies at 1200 and 1250 MHz, respectively. It was fabricated on a single piece of 2-in double-sided YBCO thin film on LaAlO3 substrate with a dimension of 26 × 42 mm. The duplexer consists of a T-junction and two bandpass filters, i.e., a ten-pole filter and an eight-pole filter for the two transmission channels, respectively. Both of the two HTS bandpass filters were specially designed to suppress the second-harmonic spurious passband. Moreover, an HTS bandstop filter is added to the duplexer to improve the out-of-band rejection at a special frequency band. As a result of the preceding special designs, in addition to a very low insertion loss (0.2 dB), considerably sharp band edge (21 dB/MHz), and good voltage standing wave ratio (better than 1.4:1), much deeper out-of-band rejection (more than 75 dB) can be realized in a much wider frequency range, i.e., up to 3 GHz, which is almost three times above the center frequency of the passbands. Although all the elements of the duplexer are integrated within a single-piece YBCO film and the layout is compact, excellent isolation (higher than 80 dB) between the two channels has still been achieved.

8-GHz Narrowband High-Temperature Superconducting Filter With High Selectivity and Flat Group Delay

This paper reports a development of a narrowband high-temperature superconducting filter with both high selectivity and flat group delay. The filter has a center frequency of 8.625 GHz and a 3-dB bandwidth of 42 MHz (a fractional bandwidth of 0.49%). In order to achieve both high band-edge steepness and excellent group-delay flatness, we introduce a 14-resonator quasi-elliptic function response with three pairs of transmission zeros (one pair for high selectivity and two pairs for flat group delay) in the cascaded quadruplet coupling structure. We also develop a novel low radiation resonator (double-folded resonator) to reduce the parasitic coupling and meet other requirements for the 8-GHz filter. The filter was fabricated on a 2-in-diameter 0.5-mm-thick MgO wafer with double-sided YBCO films. The measured results show a midband insertion loss of 1.6 dB and a return loss better than 15.5 dB. Band-edge steepness reaches over 11.7 dB/MHz at both the high- and low-frequency edges. The 60-dB rectangle ratio is less than 1.25. The out-of-band rejection is over 70 dB at 5.98 MHz from the 3-dB band edge. The variation of group delay is less than 23 ns over 33 MHz (78.5% of 3-dB bandwidth), and less than 30 ns over 34.5 MHz (82% of 3-dB bandwidth).

A 12-Pole K-Band Wideband High-Temperature Superconducting Microstrip Filter

A 12-pole wideband high-temperature superconducting (HTS) microstrip bandpass filter is reported in this paper. The filter has a center frequency of 23 GHz and a bandwidth of 4.2 GHz. The filter was fabricated on a 2-in-diameter 0.25-mm-thick MgO wafer with double-sided YBCO films. Both edge and end coupling structures were employed in this paper to achieve the desired bandwidth. An insert coupling structure was used for input/output coupling to realize the remarkably strong coupling. A microwave-absorbing material was used to eliminate cavity resonances. The measured results show a midband insertion loss of 1.3 dB, a return loss better than 9.5 dB and an out-of-band rejection of over 55 dB on both sides of the passband.

A Tunable High Temperature Superconducting Bandpass Filter Realized Using Semiconductor Varactors

This paper presents a semiconductor varactor tuned four-pole bandpass filter. The filter was designed to have a constant fractional bandwidth of 3% and was tuned with single control voltage. The design methods of how to keep coupling coefficients constant and to make all the resonators tuned synchronously are described in details. The filter was built on a two-inch double-side high temperature superconducting film. The center frequency of the filter can be tuned from 430 to 720 MHz with the direct voltage up to 20 V. The return loss is better than 10 dB in the whole tuning range. Insertion loss is in a range of 0.8~3.8 dB with 3 dB fractional bandwidth about 3%.

A Narrow Band Dual Mode HTS Patch Filter With High Power Capability

A novel structure is presented to optimize the design of narrow band dual mode patch filters. Using this method, a narrow band dual mode high power HTS filter with center frequency 2.015 GHz, fractional bandwidth less than 0.35%, return loss greater than 20 dB, near band-edge rejection close to -45 dB, and insertion loss less than 0.2 dB has been designed and fabricated. The filter can work at a power of 11.7 W without obvious deterioration of its transmission response.

Novel Design of Band-Pass Waveguide Filter With HTS E-Plane Insert

In this paper, the idea of a band-pass filter (BPF) with HTS E-plane insert in the cross waveguide is implemented in Ka-band. The advantage of this approach is to solve the problem of mounting HTS insert into the body of the metal waveguide in order to ensure good electrical contact. A three-step method for the synthesis and design of such a filter is proposed and implemented. The method includes synthesis of the normalized prototype filter, sequentially iterative synthesis of filter geometry, and the final synthesis with optimization using numerical electrodynamic analysis of the entire geometry. It is shown that for the narrowband BPF, resonance windows in the E-plane insert should be performed with accuracy better than ±0.2 μm. The characteristics of such filters are expected better or not worse than their counterparts on the basis of rectangular waveguides, but at less stringent conditions of fastening HTS insert in the body of the waveguide. For fabricating the BPF, epitaxial HTS YBa2Cu3 O7-δ films sputtered on both sides of MgO single crystal dielectric substrate of 0.5 mm thickness were used. The difference between losses in the produced filter and its simulated sample is explained with insufficient accuracy of making resonance windows in the HTS insert.

On possibily of creating HTS microstrip quasi-optical resonator

The authors present the preliminary results on simulation and experimental study of K-band HTS (high-Tc superconductor)-based microstrip quasi-optic resonator. The resonator is the developing result of the proposed earlier microstrip quasi-optic resonator based on normal metal disk on dielectric substrate. The applied aspects of HTS quasi-optic resonator are discussed briefly.

Varactor-Tuned Narrow-Band High Temperature Superconducting Notch Filter

A tunable narrow band high temperature superconducting (HTS) notch filter is presented. HTS folded square open loop resonator loaded with hyper-abrupt GaAs varactor is used to reach high tunability and avoid the via-hole grounding. Measured results show that the notch frequency can be tuned from 286 to 485 MHz (tuning range of 51.6%), and the attenuation from 26 to 70 dB when the bias voltage of the varactors is from 1 to 20 V. The -3 dB bandwidth is between 6.9 and 7.9 MHz, and the out-of-band insertion loss is less than 0.2 dB. Furthermore, the reliability of manufacture techniques of the filter is proved by mechanical vibration and shock tests.

A tunable high temperature superconducting bandpass filter using semiconductor varactors

A narrow band 4-pole varactor tuned high temperature superconducting (HTS) filter was design and fabricated. The center frequency of the filter can be tuned from 430 MHz to 720 MHz with a direct voltage up to 20V. The return loss is better than 10 dB in the whole tuning range. Insertion loss is in a range of 0.8~3.8 dB with 3dB fractional bandwidth about 3%.

Whispering gallery mode resonator unit for low phase-noise oscillators

Whispering gallery mode resonator unit for low phase-noise oscillators was designed and tested at room and low temperatures. Use of the E-plane filter and optimization of the unit of coupling the resonator with microstrip transmission line allowed us to separate the operating EH1111 mode for the purpose of steady operation of the oscillator at 29.4 GHz. The obtained dependence of the resonator external Q-factor on the resonator height over a microstrip transmission line allows foretelling the transmission coefficient depending on the resonator height over a microstrip line that gives the chance to simplify process of the oscillator tuning, especially at low temperatures.