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FIDA3: A Novel Active Array for the Mid-SKA

FIDA3: A Novel Active Array for the Mid-SKA. O. García-Pérez FG-IGN oscar.perez@oan.es J.A. López-Fernández, D. Segovia-Vargas, L.E. García-Muñoz, V. González-Posadas, J.L. Vázquez-Roy, J.M. Serna-Puente, E. Lera-Acedo, T. Finn, R. Bachiller and P. Colomer. Overview.

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FIDA3: A Novel Active Array for the Mid-SKA

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  1. FIDA3: A Novel Active Array for the Mid-SKA O. García-Pérez FG-IGN oscar.perez@oan.es J.A. López-Fernández, D. Segovia-Vargas, L.E. García-Muñoz, V. González-Posadas, J.L. Vázquez-Roy, J.M. Serna-Puente, E. Lera-Acedo, T. Finn, R. Bachiller and P. Colomer

  2. Overview • Introduction • FIDA3 prototype • Radiating structure • Bunny-ear antennas • Scan anomalies • Array measurements • Amplifiers • LNA design 1 • LNA design 2 • Conclusions

  3. Introduction • FIDA3 (FG-IGN Differential Active Antenna Array) is an active array prototype developed by the FG-IGN for the task DS4-T4 of the SKADS project. • It should meet the next requirements: • Bandwidth: 300MHz-1000MHz • Low cost • Dual polarization • Scanning capabilities up to +/-45º • Noise temperature as low as possible • The proposed solution provides the next advantages: • Dielectric-free antennas: avoid the losses and cost of the substrate • Differential feeding: avoids the losses and bandwidth limitations of passive baluns

  4. FIDA3 prototype Antennas Low noise amplifiers Feeding network Box structure

  5. Bunny-ear antennas • Bunny-ear antennas: • Similar band to classical Vivaldi antennas. • Better performance at lower frequencies. • Easy to manufacture. • 150 ohm reference impedance (in diff. mode). • Simulation of an infinite array with HFSS. • Differential feeding: avoids the losses and the bandwidth limitations of a passive balun. • No substrate: reduces cost and potential losses.

  6. Resistors Anomalies: Scan anomalies • Scan anomalies appear due to the propagation of common-mode currents. • The even-mode currents can be dissipated by connecting two resistors (3kΩ) between the feeding lines and GND, and therefore the anomalies disappear. • Optimized design: VSWR<2.5:1, scanning up to 45º. • Extra noise contribution lower than 10K. • IEEE TAP accepted for publication.

  7. Array measurements • Array tile: 32 elements per polarization. • Passive baluns to convert from differential to single-ended mode. • Active impedance calculated from the measured S-param of the array. • Reference impedance: 150Ω (diff.) • Good measured results. Center element - scanning 32 elements - broadside

  8. DLNA design 1 (I) Differential LNA #1: • Avago PHEMTs: ATF34-143 • Hot/cold test at ASTRON. • Good results for 150Ω source impedance: • T<52K • G>26dB Low Noise PHEMTs ATF34-143 (Avago Tech.) Noise Gain

  9. Active antenna impedance Active antenna impedance Actual LNA Z0=150Ω Z0 Z0 Z0 Z0 Z0=150Ω Noise Z0=150Ω DLNA design 1 (II) Mismatching effects: Collaboration FGIGN-ASTRON • Poor |s11| due to the high input impedance provided by the FET in the lower part of the band. • Mismatching effects over the active antenna impedance. • Critical noise increase. S11

  10. DLNA design 2 (I) Differential LNA #2: Collaboration FGIGN-ASTRON • Avago PHEMTs: ATF34-143 • Inductive degeneration. • Good results for 150Ω source impedance: • T<40K • G>26dB Low Noise PHEMTs ATF34-143 (Avago Tech.) Noise Gain

  11. Active antenna impedance Active antenna impedance Actual LNA Z0=150Ω Z0=150Ω Z0 Z0 Z0 Z0 Noise DLNA design 2 (II) Mismatching effects: Collaboration FGIGN-ASTRON • |s11|<-6dB • The mismatching effects over the active antenna impedance are not critical. • Good noise performance in the band of interest. Z0=150Ω S11

  12. Conclusions • The design of an active array receiver for the 300MHz-1000MHz frequency range of the Square Kilometre Array (SKA) radio-telescope has been presented. • The proposed solution provides the next advantages: • Dielectric-free structure: reduces the cost and the losses • Differential feeding: avoids the use of a passive balun • Reduced number of LNAs/m2 (~ 70.86 lna/m2) • However, some limitations appear due to its differential nature: • Scan impedance anomalies • Noise characterization of differential LNAs • Good measured results: • Scanning capabilities up to 45º with acceptable active reflection coefficient. • LNA noise temperature lower than 40K for 150Ω source impedance. • Finally, the matching condition effects between the antenna and the LNAs are analyzed: • The LNA input reflection coefficient should be well matched to the antenna impedance. • If not, the active antenna impedance will be mismatched, and the noise of the receiver may increase. • Future lines: System integration and hot/cold tests with the active array tile.

  13. Contributions [1] E. Lera-Acedo, L.E. Garcia-Muñoz, V. Gonzalez-Posadas, J.L. Vazquez-Roy, R. Maaskant, D. Segovia-Vargas, “Study and design of a differentially fed tapered slot antenna array”, IEEE Trans. Antenn. Propag., 2009. accepted [2] O. Garcia-Perez, D. Segovia-Vargas, L.E. Garcia-Muñoz, J.L. Jimenez-Martin, V. Gonzalez-Posadas , “Design, characterization and measurement of broadband differential low noise amplifiers for active differential arrays”, IEEE Trans. Microw. Theory Tech., 2009. submitted

  14. FIDA3: A Novel Active Array for the Mid-SKA THANKS O. García-Pérez FG-IGN oscar.perez@oan.es J.A. López-Fernández, D. Segovia-Vargas, L.E. García-Muñoz, V. González-Posadas, J.L. Vázquez-Roy, J.M. Serna-Puente, E. Lera-Acedo T. Finn, R. Bachiller, P. Colomer

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