Pharos matches a dynamic directional (beam shaping) radio on the air with another on the ground, with the two tracking each other for multi-mile range for video and telemetry. Coming to Kickstarter in 2-3 weeks.
The Pharos is a newly-developed smart antenna. Unlike conventional omni-directional antennas that waste energy in all directions, the Pharos concentrates the available power where you need it most. Working in conjunction with the Pixhawk autopilot (a version with its own autopilot is being also developed), the antenna activates the side facing your UAV, boosting reception and range. A second Pharos can also be used on the aircraft, quadrocopter or UAV, keeping ground control in aim at all times. The Pharos is also circular-polarized, granting immunity to polarization losses and multipathing signals, an optimum choice for challenging environments.
Air:
Ground:
Comments
Many users have addressed the 2.4GHz version and we plan to get into it. There are some challenges but solutions exist. Our main challenge is to keep the size small and comparable to the existing Pharos. Hugo is working on that.
In the meantime, there are good news. You can use the main controller board of the Pharos antenna and plug pretty much any antenna you wish. The controller operates from 10MHz up to 8GHz so it accepts pretty much all antennas. Now you can plug your own 2.4 GHz antennas. Power input limit is 1000mW so do not exceed that. Below is a picture of the antenna controller. The middle connector is the RF-in and the 4 corner connectors are the RF-out. We will also release Arduino and Teensy code that allows you to control the antennas activation sequence manually.
2.4GHz is in our plans for future development. We will tackle the technical challenge of keeping the same dimensions or close.
-Hugo
Antenna size is an issue, lower the frequency and your antenna gets bigger. However a slot antenna might work? Radio is all about the antenna and much less about the radio.
Do you intend to make additional pharos versions for other frequencies? 3DRs solo is using a single radio for video and telemetry just like the microhard radio does but in 2.4 ghz, not 5.8. This would be a no brainer if 2.4 freqs are supported.
MCX
You mentioned that you can remove the enclosure and place the 4 antennas at the 4 edges of the drone with 4 extension RF cables. What connectors do you use for the antennas?
@ Hugo, Yes, you’re right. The physical 360 yaw maneuver to determine the highest RSSI I mentioned above can be replaced with a digital cycling of the antennas every x seconds. This way you get a match faster heading determination towards HOME without needing to maneuver the frame a.k.a. smoother trajectory.
Right Hugo!
The pharos could also scan all antennas and compare their RSSI value. With the RSSI of the 3 best antennas, the direction of the GS can be triangulated. The drone then start moving in that direction and re-scan every few seconds to re-adjust trajectory.
-Hugo
@ Monroe King, That’s interesting. Like you said the multielement antenna was not build for this purpose but with some hacking (firmware related) I guess it’s possible. Let’s see:
If for example, you lose GPS, the GPS failsafe will put the drone in AltHold mode by default. Then a preprogramed 360 yaw turn can be programed as part of the GPS failsafe to determine the highest RSSI (towards the ground station). The highest RSSI will occur when one of the corresponding antennas faces the GS and it will determine a specific compass heading (not bearing as the bearing requires GPS location of the drone).
At that point, the FC (still in Alt Holt) issues this heading so the drone flies towards the generic location of the HOME point. This “modified RTL” is prone to wind drift as GPS location is not available but subsequent 360 yaw maneuvers can be preprogrammed to determine the highest RSSI every x seconds and refine the heading to HOME.
At the final stage when the drone is visible, the pilot can either take manual control or issue a LAND command as soon as the drone is close enough.
The process above is the fundamental direction finding principle based on RSSI. I never thought of this possibility and my thought process might have flaws but I think it’s doable. In our current set up we get readings of both the drone and GC RSSI. See the video on page 3. The RSSI readings are just below the artificial horizon.
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