ANITA antennas Frequency range: 200-1200MHz Dual polarization needed Low end dominated by VHF noise, impacts antenna size High end rolls off due to ice attenuation, digitizer limitations Dual polarization needed Coverage: horizon to horizon desired 2p sr  need moderate gain (=directivity) or we get too many antennas Aeff = (4 p G) / l2 so collecting area and gain are linked Choose ~20-40 antennas with 7-10 dBi of gain May add other special purpose single antennas—eg, discone at base Construction: PC board techniques attractive, but only if antenna is 2D Testing Need to build up capabilities 9/17/2018 P. Gorham

ANITA antenna configuration Proposed antennas: log-periodic zigzag, ~60 deg. overlapping beams But size shown is probably not consistent with frequency coverage Antenna clusters may also be relocatable above or below… Important for pulse interferometry force only upcoming pulses 9/17/2018 P. Gorham

Log-periodic antennas Set of interacting dipoles those near l/2 are active (resonant), shorter have capacitive reactance, longer have inductive reactance Phases add to cause elements fwd of active to focus radiation toward the active region, elements aft of active to reflect back into the active region Gain improves over dipole, antenna becomes end fire  6-12 dBi 9/17/2018 P. Gorham

LPDA Beam patterns Co-planar 1000 MHz 200 MHz 500 MHz Cross- planar 9/17/2018 P. Gorham

Examples of LP antenna fields Hall-probe measurements Active region shifted by PCB dielectric 9/17/2018 P. Gorham

Prototype antenna tests Crossed Log periodic dipole array (Microstar antennas) Good response over required BW, excellent cross-pol rejection Crossed Log periodic trapeziodal tooth PCB antenna (built ½ scale assuming no dielectric frequency shift) Very good response, also some evidence for dielectric shift, but only –10 dB Xpol 9/17/2018 P. Gorham

Log periodic zigzag antennas Allen Telescope Array feed studies LPZZ gives higher gain than LPDA analogous to pair of phased LPDAs does PCB dielectric help size? 9/17/2018 P. Gorham

Options for single broad-beam antenna Could be deployed to drop down below the main gondola after launch 9/17/2018 P. Gorham

ANITA antenna issues RF interference? How to properly calibrate? Studies suggest Antarctica is extremely quiet, but we need our own measurements How to properly calibrate? Askaryan pulse spectrum: unique bandwidth, coherence, polarization Best would be calibration with accelerator showers Phase distortion from log-periodics? Needs to b e carefully measured for trigger bandwidth Can be corrected offline for full bandwidth 9/17/2018 P. Gorham

Summary Antenna development well underway need to involve some (JPL or other) pundits for more subtle issues time to consider any innovations is now—need to freeze design soon overall geometry changes (separated clusters) offer great potential 9/17/2018 P. Gorham

LPDA measurements on prototype 9/17/2018 P. Gorham