Noritsugu Shiokawa

7 GHz-Band Quasi-Elliptic Function Narrow-Band Superconducting Filter on Sapphire Substrate

We have developed a 7 GHz band superconducting 8-pole quasi-elliptic function filter on sapphire substrate. To realize a high Qu microstrip line resonator at 7 GHz band, the structure was used for a resonator so as to suppress the radiation, which consists of two adjacent radiation points with opposite phase. Also, the radiation decreased in proportion to odd times of half-wavelength. Hairpin microstrip line resonator with 1.5 times wavelengths realized sharp-cut filter characteristic by both high Qu and transmission zeros. Measured center frequency of the 8-pole quasi-elliptic function filter agreed with the designed value. Given these features, a superconducting filter with a sharp skirt characteristic for next-generation RF applications is expected to be realized by applying these filters

Ultra-narrowband HTS filter with 2.5-wavelength hairpin resonators in 7 GHz band

We have developed an ultra-narrowband high-temperature superconducting (HTS) filter with a fractional bandwidth of 0.14% in the 7 GHz band. To realize a filter with which a narrow bandwidth and low insertion loss are compatible, resonators with high unloaded Q (Qu) value are required. Hairpin microstrip resonators with 2.5 times wavelength were adopted to suppress the radiation loss and realize a high Qu value. With both the hairpin resonators and transmission zeros supplied by an 8-pole quasi-elliptic function filter construction, designed filter properties were realized. Next-generation RF applications are expected to be realized by applying these filters.

Narrow-Band Filter for Transmitter of Radar Application

We have proposed narrow-band filter for transmitter of Radar application. A transmitting hybrid filter consists of superconducting resonators and conventional cavity. Novel hybrid filter structured with sandwich in superconducting resonators between two cavities realizes low power concentration in superconducting resonators. Compatibility of the high power handling capability and the sharp skirt feature is possible by this filter. As a result, power handling capability for the hybrid filter was obtained 537 W. Given these features, the transmitting signal with low spurious and the high density carrier frequency assignment for next-generation Radar applications is expected to be realized by applying these filters.

Low-profile high-sensitivity sub-array module with HTS filters for an active phased array antenna

We have developed a low-profile high-sensitivity sub-array module for an active phased array antenna. By using this sub-array module, a low noise receiving antenna can be easily available for wireless applications such as radar systems, communication systems, and so on. In this paper, we describe the new 16 elements S-band multichannel receiving sub-array module using high-temperature superconducting (HTS) filters as a key component for an active phased array antenna. Each receiving channel correspond to an antenna element consists of a HTS filter, a low noise amplifier (LNA), and interface circuits. In the sub-array module, 16 channel circuits are contained within a 200 mm×240 mm×30 mm vacuum chamber and cooled by a small cooler to 77 K. By using HTS filters and the cooler, feed-line loss and internal noise can be substantially reduced. Therefore, high sensitivity for an active phased array antenna can be realized. Additionally, radio wave interferences can be suppressed effectively by sharp frequency selectivity of the HTS filter with high-Q factor.

High-sensitivity receiving sub-array module with HTS filters for an active phased array antenna

We have developed a high sensitivity receiving sub-array module for an active phased array antenna. By this sub-array module, a low noise receiving antenna can be easily available for wireless applications such as communication systems, radar systems, and so on. In this paper, we describe the 16 elements S-band multichannel receiving sub-array module using high-temperature superconducting (HTS) filters as a key component for an active phased array antenna. Each receiving channel correspond to an antenna element consists of a limiter, a HTS filter, a low noise amplifier (LNA) and interface circuits. In the sub-array module, 16 channel circuits are contained within a 200 mm × 240 mm × 100 mm vacuum chamber and cooled by a common stirling cooler to 77 K. By using HTS filters and the cooler, feed-line loss and internal noise can be substantially reduced. Therefore, high sensitivity for an active phased array antenna can be realized. Additionally, radio wave interferences can be suppressed effectively by sharp frequency selectivity of the HTS filter with high-Q factor.

Ultra-narrow band tunable superconducting filter with constant bandwidth and same transmission zero points

We have proposed an ultra-narrow band tunable superconducting filter with constant bandwidth and same transmission zero points for X-band RF applications. This tunable filter tuned center frequency by dielectric rods with actuator. At the same time, coupling coefficients and external Q of the filter change with individual gradient. This filter realized constant bandwidth and same transmission zero points by means of position at coupling microstrip line. The developed tunable superconducting filter has 4-pole elliptic function response for sharp skirt characteristic. Tuning range was between 9700 MHz and 9800 MHz for weather radar. Also, this filter had fractional bandwidth of 0.04%.

Narrow-band superconducting hybrid filter for 100kW transmitter of X-band radar application

We have proposed narrow-band transmitting hybrid filter which puts on the output of the 100kW klystron amplifier for X-band radar application. A transmitting hybrid filter consists of superconducting resonators and conventional cavities. Novel hybrid filter structured with two cascade connections of reflection-type cavities, reflection-type superconducting resonators, and open-stub realizes low power concentration in superconducting resonators. Compatibility of the high power handling capability and the sharp skirt feature is possible by this filter. As a result, power handling capability for the hybrid filter was obtained 100 kW. Also, this filter had fractional bandwidth of 0.055%. Given these features, the transmitting signal with low spurious and the high density carrier frequency assignment for next-generation Radar applications is expected to be realized by applying these filters.

Superconducting sub-array module as T/R module for X-band active phased array antenna

We have developed a high-sensitivity superconducting sub-array module for an X-band active phased array antenna. This sub-array module can be assumed as a multichannel T/R module with 16 antenna elements. And the module also includes 16 transmitting (TX) channels and 16 receiving (RX) channels with high-Tc superconducting (HTS) filters. By means of this sub-array module, a high-sensitivity antenna can be easily available for wireless applications such as communication systems and radar systems. In this paper, we describe the newly developed X-band superconducting sub-array module that is applicable as a key component for an active phased array antenna. In particular, each Rx channel contains a cryogenic circuit that mainly consists of HTS filters and a low-noise amplifier (LNA) cooled at 77 K for low insertion loss and low internal noise. 16 cryogenic circuits are contained within a 100 mm×100 mm×36.5 mm vacuum chamber and cooled by a small cooler. By using HTS filters and cooling, noise temperature of the RX channels was reduced to less than 60 K and naturally the high-sensitivity X-band sub-array module was realized. Additionally, the features of the sub-array module, such as low amplitude deviation and good phase linearity, indicated that both TX channels and RX channels were appropriate for an active phased array antenna.

L-band small high-sensitivity microwave receiver module using superconducting filter

We have developed an L-band small high-sensitivity microwave receiver module using a superconducting filter. An L-band superconducting filter for a small microwave receiver module is designed as a four-pole elliptic function filter. The resonator uses a stepped-impedance hairpin microstrip line resonator. The developed superconducting filter uses high-Tc superconducting material, YBCO. The fabricated superconducting filter had a low insertion loss of 0.1dB. We have fabricated a small microwave receiver module in which the designed filter is mounted in a cryocooler. The volume of the fabricated module was 2 liters. In addition, the noise figure of the microwave receiver module was 0.5dB. We have demonstrated the receiver module with high sensitivity and small size.

Superconducting narrow-band filter for 2 GHz-band transmitter

We have developed a superconducting microstrip resonator for the narrow-band transmitting filter application, in order to achieve both high power handling capability and high unloaded Q value. For the superconducting microstrip resonator, it is necessary to suppress the radiation loss of the resonator in order to achieve high unloaded Q value and to reduce the maximum current density in the resonator to achieve high power handling capability, too. Therefore, by adopting an interdigital resonator consisting of two coupled comb resonators, we have reduced current density and suppressed the radiation loss. Using the interdigital resonators, we have fabricated an 8-pole pseudo-elliptic function filter that has about 2.0 GHz center frequency and 0.975% fractional bandwidth, and evaluated the power handling capability. As a result, we have confirmed that the power handling capability of the filter exceeds 40 W.