Kei Satoh

Cryogenic receiver front-end with sharp skirt characteristics

This paper presents an experimental cryogenic receiver front-end (CRFE) with sharp skirt characteristics for mobile base stations. The CRFE comprises a high-temperature superconducting filter, a cryogenic low-noise amplifier, and a highly reliable cryostat that is very compact. The major characteristics of the proposed CRFE measured at 70 K are a centre frequency of 1.95 GHz, passband width of 20 MHz, sharp selectivity of 20 dB/100 kHz, 1.4 dB ripple, 31.3 dB average passband gain, and average passband equivalent noise temperature of 47.9 K. The CRFE weighs 19 kg and occupies 35 l. Random failure of the cryostat is also evaluated by a continuous operation test using four identical ones simultaneously. The cryostat used in the CRFE has a high reliability level of over five years of continuous maintenance-free operation.

The 2 GHz high temperature superconducting receiver equipment for mobile communications

Abstract An ultra low noise and highly selective, experimental 2 GHz band cryogenic receiver front end (CRFE) has been newly developed for mobile communication base stations. It utilizes a high- Q superconducting filter, a very low noise cryogenic amplifier, and a highly reliable cooler that is very compact. The equivalent noise temperature ( T eq ) of the CRFE is less than 50 K (0.69 dB of NF). According to current device data, T eq of normal temperature front ends in the 2 GHz band is typically 300 K (3 dB of NF). Thus, the improvement in sensitivity on mobile communication base station reception is estimated at 250 K (2.31 dB). If the CRFEs apply to W-CDMA base station receptions instead of normal temperature front ends, it is impossible to expand the coverage of a base station by about 70%. Alternatively, the capacity in W-CDMA system is able to increase by 10–160%. Furthermore, the transmission power of the user equipment can be reduced in proportion to the NF improvement.

New CPW Quarter-Wavelength Resonator with Open Stubs for Multipole Dual-Band Bandpass Filter

This paper proposes a newly developed CPW quarter-wavelength resonator with open stubs for use in a multipole dual-band bandpass filter. The proposed resonator has odd- and even-mode resonant frequencies that are configured using the space between the center conductor and the open stubs. It is easy to configure independently the odd- and even-mode coupling coefficients because the two resonant modes have different current density distributions. We design and fabricate a four-pole Chebyshev 2.0-/3.5-GHz band bandpass filter to investigate the validity of the proposed resonator. The proposed resonator is suitable for use in a multipole dual-band bandpass filter.

A Miniaturized High Temperature Superconducting Bandpass Filter Using CPW Quarter-Wavelength Spiral Resonators

A novel compact high temperature superconducting BPF is developed by using coplanar waveguide quarter-wavelength spiral resonators. The filter is a 5-pole Chebyshev BPF with a midband frequency of 5.0GHz and an equal-ripple fractional bandwidth of 3.2%. The CPW spiral resonator is made as small as 1.02times2.1mm2. As a result, the 5-pole filter occupies an area of only 7.65x2.11mm2, less than one-third that of a newly reported CPW interdigital filter. The filter is fabricated by using 0.5mum YBCO film deposited on an MgO substrate. No bond-wire air-bridges are used and no post-tuning is made in the experiment. The measured filtering characteristics agree well with EM simulations and show low passband insertion losses in spite of the small size of the filter

Compact 2.4-/2.9-GHz band parallel-planar bandpass filter

This paper proposes a compact dual-band bandpass filter (DBPF) based on a parallel-planar architecture where resonators are formed on the opposite sides of each substrate. The proposed architecture enables dual-band operation without an appreciable change in the volume of the DBPF and yields design freedom for the resonant frequencies by adjusting the distance between the substrates. A 2.4-/2.9-GHz band DBPF is fabricated using YBCO film deposited on a MgO substrate with a coplanar waveguide structure to investigate experimentally dual-band operation. The measurement results agree with those of the simulation.

An integrated configuration of antennas and filters for front-end module in massive-MIMO transmitter

This paper presents an integrated configuration of patch antennas and low-profile filters for a front-end module in a Massive-MIMO transmitter on 5G era. It is very important for the Massive-MIMO transmitter to build thin and light-weight equipment from the viewpoint of easy installation. However, in general, conventional filters used in base station transmitters are large and heavy-weight, which prevents the Massive-MIMO transmitter from achieving its compact-sized configuration. This paper employs a substrate integrated waveguide (SIW) filter which can provide thin structure combined with antennas using the same substrate material. This paper evaluates the proposed configuration by computer simulation including SIW filters and patch antennas in order to reveal the directivity degradation by the SIW filters. There is almost no degradation with regard to the directivity of the proposed configuration as an array antenna. These investigation results show a key-way to configure the Massive-MIMO transmitter that can offer advantages in low-profile and light-weight.

High-temperature superconducting coplanar-waveguide quarter-wavelength resonator with odd- and even-mode resonant frequencies for dual-band bandpass filter

This paper presents a high-temperature superconducting coplanar-waveguide quarter-wavelength resonator that has two different resonant modes for use in a dual-band bandpass filter (DBPF). An RF filter with multiple passbands such as the DBPF is a basic element that is expected to achieve broadband transmission by using separated frequency bands aggregately and simultaneously in future mobile communication systems. The proposed resonator has a folded center conductor and two open stubs that are aligned close to it. The odd- and even-mode resonant frequencies are configured using the space between the folded center conductor and the open stubs. It is easy to configure the odd- and even-mode coupling coefficients independently because the two resonant modes have different current density distributions. Consequently, a DBPF with two different bandwidths can be easily designed. This paper presents three design examples for a four-pole Chebyshev DBPF with different combinations of fractional bandwidths in order to investigate the validity of the proposed resonator. This paper also presents measured results of the DBPF based on the design examples from the standpoint of experimental investigation. The designed and measured frequency responses confirm that the proposed resonator is effective in achieving DBPFs not only with two of the same bandwidths but also with two different bandwidths.

Experimental Evaluation of Man-Made Noise for Cryogenic Receiver Front-End

A cryogenic receiver front-end (CRFE) is anticipated to be an effective way to achieve efficient frequency utilization and to improve the sensitivity of mobile base station receivers. The CRFE comprises a superconducting filter, a cryogenic low- noise amplifier, and a highly reliable cryostat. Evaluating man- made noise as well as thermal noise is indispensable in order to investigate the effect of employing the CRFE. This paper presents measured results of man-made noise in urban and suburban areas in the 2-GHz band when applying the amplitude probability distribution method. The measured results suggest that the contribution of man-made noise in the 2-GHz band can be ignored as far as the Wideband Code Division Multiple Access (W-CDMA) system is concerned. The man-made noise is also measured in the VHF-band for comparison with the 2-GHz band environment.

A 5-GHz band coplanar-waveguide high temperature superconducting filter employing T-form open gap

This paper presents a coplanar-waveguide (CPW) high-temperature superconducting (HTS) filter that has a T-form open gap as an input/output coupling structure to reduce the fluctuation in filter characteristics caused by dimension errors originating from the manufacturing processes of the filter. Numerical and experimental investigations based on a 5-GHz band CPW HTS filter confirm that T-form structure suppresses the fluctuation to a level lower than the existing structure. The fabricated filter has a center frequency of 5.006 GHz, a 3.5% (175 MHz) equal ripple bandwidth, a 0.11-dB ripple, and a 0.11-dB average insertion loss, all measured at 60 K.

A novel compact high temperature superconducting CPW bandpass filter

A novel high temperature superconducting interdigital bandpass filter is proposed by using coplanar waveguide quarter-wavelength resonators. The CPW resonators are arranged in parallel, and consequently the filter becomes very compact. The filter is a 5-pole Chebyshev BPF with a midband frequency of 5.0GHz and an equal-ripple fractional bandwidth of 3.2%. It is fabricated using a YBCO film deposited on an MgO substrate. The measured filtering characteristics agree well with EM simulations and show a low insertion loss in spite of the small size of the filter.