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

2. SKA Overview

3. HIGH SENSITIVITY Attractive to all radio astronomers

4. WIDEBAND DETECTION OF A RADIO SIGNAL Technical Challenging

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 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

8. Kildal Feed

9. Constant Directivity

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

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

13. Trial Test on the Taper Slot Antenna Kagoshima University

15. UWB Low Noise Receiver

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

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

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

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

20. MMIC design 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. The coplanar wave-guide is expected to be low in the transmission loss.

21. Expected Performance Gain > 20dB @43GHzTrx < 25K @43GHz A circuit simulator shows the expected performance of the InP MMIC as indicated below.

22. 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

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

24. 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.

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

26. W49N on NRO 45m detected without frequency conversion Spectrum after frequency conversionDirect 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 spectrum order is inverted.

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

28. Trans. Reflection 50 GHz InP HBT AD Module

29. Frequency Conversion The 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 Direct Digital InP HBT Full Digital Receiver (2007?) Amplifier

30. 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