technical interests on the ska noriyuki kawaguchi national astronomical observatory of japan ska...
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Technical Interests on the SKA
Noriyuki Kawaguchi
National Astronomical Observatory of Japan
SKA WorkshopNovember 5, 2010
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SKA Overview
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HIGH SENSITIVITYAttractive to all radio astronomers
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WIDEBAND DETECTION OF A RADIO SIGNAL
Technical Challenging
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Wideband Receiver
• Octave band (4-8 GHz) is now common in mm- and submm- SIS receivers in their IF.
• Decade band (1-10 GHz or 2.5-25GHz) is attractive not only for the SKA but also for radio spectroscopy searching molecular line forest.
• Century band (200MHz-20GHz) is prospective in the next decade.
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Octave to Decade Band
• Radiator (antenna)– Reflectors are independent from the operating
frequency except for the surface accuracy.– Technically difficulties on the radio launcher.
• Receiver– Decade band LNA is commercial available.
• Digital Signal Processing– A high speed sampler makes possible to detect a radio
signal without making frequency down conversion.
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Self-Complementary AntennaMushiake’s Principle Z0=188.4 Ω
Input impedance is constant over a wide frequency range.
The “Self-complementary antenna” was originated and its constant-impedance property was discovered in 1948 by Y. Mushiake. Several years later, Professor V. H. Rumsey in the USA studied the antenna with log-periodic shape for the purpose of developing “Frequency-independent antenna” by making use of such a property of self-complementary antenna. For this reason, his antenna was actually “log-periodic self-complementary antenna”. In the meantime, his coworkers developed an extremely broadband practical antenna by modifying his original structure, and it advanced further to the log-periodic dipole array. These antennas which are derived from the original log-periodic self-complementary antenna structure are generally called “Log-periodic antenna” or “LP antenna”. It is well-known that these so-called “Log-periodic antennas” have extremely broadband property.
Please recall memories
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Kildal Feed
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Constant Directivity
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Quad Ridge Radiator
ETS/LINDGREN, 2GHz – 18GHz Double Ridge Horn
Bruns, IEEE EMC,45, 1, p.55, 2003
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Taper Slot Radiator
After Saito, Ricoh Technical Report, No.24, Nov. 1998
10GHz – 60GHz
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Trial Test on the Taper Slot Antenna
Kagoshima University
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UWB Low Noise Receiver
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Overview of Semiconductor Devices
4 Gsps,2bit( Matsumoto, Kawaguchi, 1995)
HBT
FET/HEMT
A/D Converter
Low Noise Amplifier
Memory,DSP
(Area Density)
Hig
h Sp
eed,
Low
Noi
se
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InP HEMT for LNA
Open
Short
HEMT
Source
Source
Drain
Gate
Active elements was evaluated on the test fabrication chips.
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The passive elementsThe passive elements for resistance, inductance and capacitance are evaluated at the cooled environment.
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Test Equipments
Vacuum Dewar
manipulator
Magnifier
Probe20K Stage
Test devices are mounted on a cooled stage to measure the electric performances.
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MMIC designThe active and the passive elements are assembled onto an InP substrate to form a MMIC of a 2-stage amplifier to be cooled down at 30 K or lower temperature.Two MMIC chips will be built into a 43-GHz LNA module.The MMIC chip is now under fabrication and become available soon in March 2008.
The coplanar wave-guide is expected to be low in the transmission loss.
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Amplifier Module
Waveguide-to-Microstrip-line conversion
Waveguide-to-Coplanar transition is requested for the new 43-GHz MMIC amplifier.
A GaAs MMIC amplifier currently used for VERA telescopes
Trx ~ 60K
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InP HBT technology
High speed A/D converter,
The highest sampling rate is 50GHz.
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3-bit 50-GHz AD chip
(3 mm × 3mm )
Comparator Encoder
Hope to free from frequency conversion with a high speed AD converter.
LNA outputs of 22-GHz and 43-GHz signal are to be digitized directly.
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A noise spectrum over 20-24GHzdetected with a 50-GHz sampler
20GHz 25GHz
Red Dots: RF Direct Digital SpectrumGreen Dots: Analog Spectrum
The first successful result in the world.
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W49N on NRO 45m detected without frequency conversion
Spectrum after frequency conversion Direct detection (20.480-24.576GHz)
LO=(16.85+3)-GHz signal converts a 22-GHz Signal to a 2.2-2.4GHz signal. The IF signal Is digitized at a speed of 8.192-GHz (over sampling), then Fourier transformed with 512K spectrum.
A 20.480-24.576GHz (BW=4.096GHz)signal is directly digitized at a sampling rate of 8.192GHz, then Fourier trans-formed with 512K spectrum. The spectrumorder is inverted.
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Ultra High Speed SamplerSampling jitter was evaluated.
0.2-psec jitter is observed.
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Trans.
Reflection
50 GHz
InP HBT AD Module
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Frequency ConversionThe Heterodyne Technology was established in 1918.
Direct Detection(1887)
Amplifier
Mixer, LO
Vacuum Tube Amp.(1906)Heterodyne Detection(1918)
Amplifier
A/D
Semiconductor Amplifier(1947)Digital Processing(1970 ~ )
Mixer, LO
Direct Heterodyne(+Analog)
Heterodyne(+Digital)
A/D
DirectDigital
InP HBTFull DigitalReceiver(2007?)
Amplifier
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Concluding Remarks
• Possible Japanese contributions– Low noise amplifier (InP HEMT MMIC)– High speed AD converter (InP HBT)
• No frequency conversion gives great merits to the SKA, simplifying the receiver.
– High speed computation (Massive Computing)
• Industry engagement in Japan– Preparing a proposal for the advance
instrumentation program by 2016