Transcript Technical Interests on the SKA

SKA Workshop
November 5, 2010
Technical Interests on the SKA
Noriyuki Kawaguchi
National Astronomical Observatory
of Japan
SKA Overview
Attractive to all radio astronomers
HIGH SENSITIVITY
Technical Challenging
WIDEBAND DETECTION OF A
RADIO SIGNAL
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.
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.
Self-Complementary Antenna
Mushiake’s Principle Z0=188.4 Ω
Please recall memories
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 selfcomplementary antenna. For this reason, his antenna was actually “log-periodic selfcomplementary 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 logperiodic 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.
Kildal Feed
Constant Directivity
Quad Ridge Radiator
ETS/LINDGREN,
2GHz – 18GHz
Double Ridge Horn
Bruns, IEEE EMC,
45, 1, p.55, 2003
Taper Slot Radiator
10GHz – 60GHz
After Saito, Ricoh Technical Report, No.24, Nov. 1998
Trial Test on the Taper Slot Antenna
Kagoshima University
UWB Low Noise Receiver
Overview of Semiconductor Devices
FET/HEMT Low Noise Amplifier
HBT
High Speed, Low Noise
A/D Converter
４Gsps,2bit
（ Matsumoto, Kawaguchi,１９９５）
Memory,
DSP
(Area Density)
InP HEMT for LNA
Active elements was evaluated on the test fabrication chips.
HEMT
Open
Drain
Short
Source
Source
Gate
The passive elements
The passive elements for resistance, inductance and
capacitance are evaluated at the cooled environment.
Test Equipments
Test devices are mounted on a cooled stage to measure
the electric performances.
Magnifier
20K Stage
Probe
Vacuum
Dewar
manipulator
MMIC design
The coplanar wave-guide is expected to
be low in the transmission loss.
The 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 43GHz LNA module.
The MMIC chip is now under fabrication
and become available soon in March 2008.
Amplifier Module
Waveguide-to-Coplanar transition is requested for the new 43-GHz MMIC
amplifier.
Waveguide-to-Microstrip-line conversion
Trx ~ 60K
A GaAs MMIC amplifier currently used for VERA telescopes
InP HBT technology
High speed A/D converter,
The highest sampling rate is 50GHz.
3-bit 50-GHz AD chip
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.
(3 mm × 3mm）
A noise spectrum over 20-24GHz
detected with a 50-GHz sampler
The first successful result in the world.
Red Dots: RF Direct Digital Spectrum
Green Dots: Analog Spectrum
20GHz
25GHz
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 22GHz Signal to a 2.2-2.4GHz signal. The
IF signal Is digitized at a speed of 8.192GHz (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 transformed with 512K spectrum. The spectrum
order is inverted.
Ultra High Speed Sampler
Sampling jitter was evaluated.
0.2-psec jitter is observed.
InP HBT AD Module
Trans.
Reflection
50 GHz
Frequency Conversion
The Heterodyne Technology was established in 1918.
Direct
Heterodyne
(+Analog)
Amplifier
Heterodyne
(+Digital)
Direct
Digital
Amplifier
Amplifier
A/D
Mixer, LO
Direct
Detection
(1887)
Vacuum Tube Amp.
(1906)
Heterodyne Detection
(1918)
A/D
Mixer, LO
Semiconductor
Amplifier
(1947)
Digital Processing
(1970 ～)
InP HBT
Full Digital
Receiver
(2007?)
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