1. 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

2. 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

3. 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

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

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

6. 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

7. 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

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

9. 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

10. 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

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