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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.

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Technical Interests on the SKA

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  1. SKA Workshop November 5, 2010 Technical Interests on the SKA Noriyuki Kawaguchi National Astronomical Observatory of Japan

  2. SKA Overview

  3. Attractive to all radio astronomers HIGH sensitivity

  4. Technical Challenging Wideband detection of a Radio signal

  5. 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.

  6. 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.

  7. Self-Complementary Antenna Mushiake’s Principle Please recall memories 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.

  8. Kildal Feed

  9. Constant Directivity

  10. Quad Ridge Radiator ETS/LINDGREN, 2GHz – 18GHz Double Ridge Horn Bruns, IEEE EMC, 45, 1, p.55, 2003

  11. Taper Slot Radiator 10GHz – 60GHz After Saito, Ricoh Technical Report, No.24, Nov. 1998

  12. Trial Test on the Taper Slot Antenna Kagoshima University

  13. UWB Low Noise Receiver

  14. Overview of Semiconductor Devices FET/HEMT Low Noise Amplifier HBT A/D Converter ４Gsps,2bit （ Matsumoto, Kawaguchi,１９９５） High Speed, Low Noise Memory, DSP (Area Density)

  15. InP HEMT for LNA Active elements was evaluated on the test fabrication chips. HEMT Open Drain Short Source Gate Source

  16. The passive elements The passive elements for resistance, inductance and capacitance are evaluated at the cooled environment.

  17. Test Equipments Test devices are mounted on a cooled stage to measure the electric performances. Magnifier 20K Stage Probe manipulator Vacuum Dewar

  18. 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 43-GHz LNA module. The MMIC chip is now under fabrication and become available soon in March 2008.

  19. 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

  20. InP HBT technology High speed A/D converter, The highest sampling rate is 50GHz.

  21. 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）

  22. A noise spectrum over 20-24GHzdetected with a 50-GHz sampler The first successful result in the world. Red Dots: RF Direct Digital Spectrum Green Dots: Analog Spectrum 25GHz 20GHz

  23. W49N on NRO 45m detected without frequency conversion Spectrum after frequency conversion Direct detection (20.480-24.576GHz) A 20.480-24.576GHz(BW=4.096GHz) signal is directly digitized at a sampling rate of 8.192GHz, then Fourier trans- formed with 512Kspectrum. The spectrum order is inverted. LO=(16.85+3)-GHzsignal converts a 22-GHz Signal toa 2.2-2.4GHz signal. The IF signal Is digitized at a speed of 8.192-GHz (over sampling), then Fourier transformed with 512Kspectrum.

  24. Ultra High Speed Sampler Sampling jitter was evaluated. 0.2-psec jitter is observed.

  25. InP HBT AD Module Trans. Reflection 50 GHz

  26. Direct Detection (1887) Frequency Conversion The Heterodyne Technology was established in 1918. Heterodyne (+Analog) Heterodyne (+Digital) Direct Direct Digital Amplifier Amplifier Amplifier A/D A/D Mixer, LO Mixer, LO Semiconductor Amplifier (1947) Digital Processing (1970 ～) InP HBT Full Digital Receiver (2007?) Vacuum Tube Amp. (1906) Heterodyne Detection (1918)

  27. 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

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