Yusheng He

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.

A 12-Pole Narrowband Highly Selective High-Temperature Superconducting Filter for the Application in the Third-Generation Wireless Communications

An ultra-selective high-temperature superconducting bandpass filter was designed and fabricated to satisfy the demands of the third-generation wireless communications. This filter was designed to have 12-pole quasi-elliptic response with 4.68-MHz bandwidth in the third-generation communications band (a fractional bandwidth of 0.0023). Full-wave simulations were conducted by using Sonnet software. A novel, compact, and low radiation resonator with a high-quality (Q) factor value was developed to reduce the parasitical coupling. In order to satisfy the demand of high band-edge steepness, three pairs of transmission zeros at finite frequencies were introduced in the cascaded quadruplet coupling structure. The filter was fabricated on a 2-in-diameter 0.43-mm-thick sapphire wafer with double-sided YBCO films. The measurements showed that the passband center frequency (f0) of the filter is 2.038 GHz at 67 K with a midband insertion loss of 0.67 dB and the return loss better than 15 dB. The measured response of the filter also exhibited ultra-high band-edge steepness of 140-220 dB/MHz. Better than 60 dB of out-of-band rejections for frequencies very close to the band edge (|f-f0|>2.7 MHz), better than 90 dB at frequencies 7.5 MHz away from the center frequency and up to 100 dB of wideband rejections were achieved

A Wideband Superconducting Filter Using Strong Coupling Resonators for Radio Astronomy Observatory

A 12-pole wideband superconducting microstrip bandpass filter, which has a fractional bandwidth of 38% and a center frequency of 1455 MHz, is presented for the Miyun 50-m radio astronomy telescope, Beijing, China. A novel resonator, which can not only generate very large coupling, but also push its first spurious resonant peak away from the passband, is introduced. A new style interleaved coupling structure is proposed and successfully used in this study to realize the remarkably required strong coupling. To achieve high edge slope on the high side of the passband, as required, a single transmission zero was introduced. The filter was fabricated on a 36 mm times 30 mm times 0.5 mm double-sided YBa2Cu3O7 film deposited on an MgO substrate. The measured results showed that the filter had 0.05-dB minimum insertion loss, 0.08-dB passband ripple, and 23-dB return loss at a temperature of 40 K. The first spurious peak did not appear until 2632 MHz. The overall measured performance showed good agreement with the simulation.

A 24-pole high Tc superconducting filter for mobile communication applications

This paper presents a highly selective 24-pole Chebyshev HTS bandpass filter. The filter was designed at 1748 MHz centre frequency with 75 MHz bandwidth, which was suitable for the GSM base station. The filter was fabricated using double-sided YBCO films on a 3 in diameter, 0.43 mm thick sapphire substrate. The simulation of the filter performance was carried out using Sonnet software. A novel resonator structure was proposed. The resonator exhibited a very high Q value of about 30 000 at 77 K. The filter showed an excellent selectivity. At the band edge of the filter, the slope was about 17 dB MHz(-1). Out of the band, the rejection level is better than -90 dB.

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).

Superconducting filter with a linear phase for third-generation mobile communications

A linear phase filter using two cross- coupled quadruplet structures to achieve self- equalization was designed at 2012.5 MHz with 5 MHz bandwidth for a third- generation mobile communications system. This filter was fabricated using double- sided YBCO films on a 2 inch diameter, 0.5 mm thick MgO substrate. In the measurement, it showed good matching in the passband, with reflection better than - 15 dB. Moreover, the group delay variation is less than 50 ns over 89% of the filter bandwidth.

A HTS Bandpass Filter for a Meteorological Radar System and Its Field Tests

This paper presents recent progress of a high temperature superconducting (HTS) filter designed for a meteorological radar system (wind profiler) and its field tests results. The filter was designed to exhibit a ten-pole quasi-elliptic response with a fractional bandwidth of 0.35% in L band. It was fabricated using double-sided YBCO films on a 50-mm-diameter, 0.5-mm-thick MgO substrate. A HTS subsystem was assembled by connecting the filter with a cryogenic low noise amplifier (LNA), fixing them on a cryocooler and enclosing in a cryopackage. With the HTS subsystem substituting the corresponding conventional part (the conventional subsystem) of the wind profiler, two stages of experiments including field test were carried out. The first stage experimental results showed that while employing the HTS subsystem the sensitivity of the wind profiler improves 3.7 dB and the anti-interference ability improves 48.4 dB. The second stage experiment-field test results showed the improvement visually through the wind charts and wind profiles obtained in the field trial.

A Novel Quasi-Elliptic HTS Filter With Group-Delay Equalization Using Compact Quasi-Lumped Element Resonators in VHF Band

To produce a filter small enough to fit a 2-in wafer in the very high frequency (VHF) band while avoiding parasitic cross coupling among nonadjacent resonators, a novel quasi-lumped element resonator with interdigital capacitor, double-spiral inductor, and pad capacitor have been introduced. This resonator has not only a highly miniature structure but also a very weak far-field radiation. A ten-pole quasi-elliptic filter with group-delay equalization, which has a 7.1-MHz 1-dB passband and a center frequency of 257.5 MHz, is designed and fabricated on a 37.3 x mm x 30.1 x mm x 0.5 x mm LaAlO3 substrate. The measured results showed a 0.24-dB insertion loss, a 15-dB return loss, and a 70-dB out-of-band rejection. Moreover, the group delay variation is less than 50 ns over 70% of the 1-dB passband and the band where the phase error ripple is within plusmn5deg is more than 80% of the 1-dB passband. The overall experimental performance showed excellent agreement with the theory and simulation, which is a good proof of the advantage of our weak far-field radiation resonator. The result showed that the novel resonator is very suitable to fabricate narrowband ultrahigh frequency, VHF, or even lower frequency high-temperature superconductor filters on a 2-in wafer.

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.

An impedance matched phase shifter using BaSrTiO/sub 3/ thin film

We present a distributed phase shifter with an equal ripple return loss at its operation frequency range. The phase shifter is based on a periodic structure and consists of a coplanar waveguide (CPW) line periodically loaded with voltage-variable barium strontium titanate (BST) interdigitated capacitors. Measurements show that its return loss is better than -15dB at frequencies from direct current to 16GHz, and at 9.4GHz, its phase shift is 41/spl deg/ under 120-V applied bias voltage.