O. García-Pérez (FG-IGN) 1FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 FIDA3: A Novel Active Array for the Mid-SKA O. García-Pérez FG-IGN 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

O. García-Pérez (FG-IGN) 2FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 Overview Introduction FIDA3 prototype Radiating structure –Bunny-ear antennas –Scan anomalies –Array measurements Amplifiers –LNA design 1 –LNA design 2 Conclusions

O. García-Pérez (FG-IGN) 3FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 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

O. García-Pérez (FG-IGN) 4FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 FIDA3 prototype Antennas Box structure Feeding network Low noise amplifiers

O. García-Pérez (FG-IGN) 5FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 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.

O. García-Pérez (FG-IGN) 6FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 Scan anomalies Anomalies: Resistors 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.

O. García-Pérez (FG-IGN) 7FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 Array measurements Center element - scanning32 elements - broadside 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.

O. García-Pérez (FG-IGN) 8FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 DLNA design 1 (I) Differential LNA #1: Avago PHEMTs: ATF Hot/cold test at ASTRON. Good results for 150Ω source impedance: –T<52K –G>26dB Low Noise PHEMTs ATF (Avago Tech.) Noise Gain

O. García-Pérez (FG-IGN) 9FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 DLNA design 1 (II) Mismatching effects: Collaboration FGIGN-ASTRON Poor |s 11 | 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. Z 0 =150Ω S 11 Noise Z 0 =150Ω Z0Z0 Z0Z0 Z0Z0 Z0Z0 Active antenna impedance Z 0 =150Ω Active antenna impedance Actual LNA

O. García-Pérez (FG-IGN) 10FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 DLNA design 2 (I) Differential LNA #2: Collaboration FGIGN-ASTRON Avago PHEMTs: ATF Inductive degeneration. Good results for 150Ω source impedance: –T<40K –G>26dB Low Noise PHEMTs ATF (Avago Tech.) Noise Gain

O. García-Pérez (FG-IGN) 11FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 DLNA design 2 (II) Mismatching effects: Collaboration FGIGN-ASTRON |s 11 |<-6dB The mismatching effects over the active antenna impedance are not critical. Good noise performance in the band of interest. Noise S 11 Z 0 =150Ω Z0Z0 Z0Z0 Z0Z0 Z0Z0 Active antenna impedance Z 0 =150Ω Actual LNA Active antenna impedance

O. García-Pérez (FG-IGN) 12FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 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/m 2 (~ lna/m 2 ) 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.

O. García-Pérez (FG-IGN) 13FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 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., 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., submitted

O. García-Pérez (FG-IGN) 14FIDA3 Wide Field Astronomy and Technologies for the SKA, Limelette, 4-6 November 2009 THANKS FIDA3: A Novel Active Array for the Mid-SKA O. García-Pérez FG-IGN 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