3 ms·

Since the frequency can be adjusted based on the amount its stretched - such that in the 'short-squshed state its better for 'ground' users - and stretched for

Since the frequency can be adjusted based on the amount its stretched - such that in the 'short-squshed state its better for 'ground' users - and stretched for satellite comms -- could one of these be 'Funnel-shaped' so that you have a wide, but squished 'ground'section - and then it funnels to a stretched out length for satts? Or can you only have one frequency per form?

wildzzz 3y ago
It's not the frequency of the antenna that changes, it's the directivity of the emitted power. The resonant frequency is determined by the length of the metallic strips of the helix which determines how thick and tall the helix is. The angle of the helix when the strip lengths are fixed is what determines the directivity pattern, which is what they are adjusting here by squashing it down. If you tried to design an antenna that was good at both directions, you'd end up with an omnidirectional antenna which is exactly what the extended helical does. If you don't know where the receiver is, you build an omnidirectional antenna that will send power out in all directions. When you do know where the receiver is, you build a directional antenna that puts most of the power in a specific direction (and make sure the antenna is pointed that way). You can see the polar plots in Figure 8 in the article that shows two different plots, one with a flat shape that puts most power in the horizontal direction with little being directed backwards (extended helix). The next plot shows nearly all the power being directed to 0deg, meaning straight up (squashed helix). The next plots show that at 1.1GHz, the extended helix has a pretty flat gain between -100 and +100deg but the squashed helix has nearly 10dB gain at 0deg. There are other directional antennas that can get better gain at 0deg but they aren't flexible like this design. I could see this kind of design used for cellular modems mounted on vehicles. If you are within range of a tower, the antenna is in the extended state. If you are out of range, the antenna moves to a flattened state to try to reach a satellite capable of receiving cell communications. It could also be used in other applications where the extended state and is used to locate a signal but then once it's been detected, the antenna morphs to the flattened state and is pointed at the signal source. Extra gain means you can increase bandwidth of a digital signal.
- samstave 3y ago
  >>>*"the antenna moves to a flattened state to try to reach a satellite capable of receiving cell communications." Sounds just like what Starlink is going to need for the direct to cell service they just tested! But your point of mobile mounting this sounds pretty great, and obvious when its pointed out, actually. I hope this does good things. Hopefully its something that anyone can make and doesnt need to pay some high fee to benefit from.

wildzzz 3y ago

It's not the frequency of the antenna that changes, it's the directivity of the emitted power. The resonant frequency is determined by the length of the metallic strips of the helix which determines how thick and tall the helix is. The angle of the helix when the strip lengths are fixed is what determines the directivity pattern, which is what they are adjusting here by squashing it down. If you tried to design an antenna that was good at both directions, you'd end up with an omnidirectional antenna which is exactly what the extended helical does. If you don't know where the receiver is, you build an omnidirectional antenna that will send power out in all directions. When you do know where the receiver is, you build a directional antenna that puts most of the power in a specific direction (and make sure the antenna is pointed that way). You can see the polar plots in Figure 8 in the article that shows two different plots, one with a flat shape that puts most power in the horizontal direction with little being directed backwards (extended helix). The next plot shows nearly all the power being directed to 0deg, meaning straight up (squashed helix). The next plots show that at 1.1GHz, the extended helix has a pretty flat gain between -100 and +100deg but the squashed helix has nearly 10dB gain at 0deg. There are other directional antennas that can get better gain at 0deg but they aren't flexible like this design. I could see this kind of design used for cellular modems mounted on vehicles. If you are within range of a tower, the antenna is in the extended state. If you are out of range, the antenna moves to a flattened state to try to reach a satellite capable of receiving cell communications. It could also be used in other applications where the extended state and is used to locate a signal but then once it's been detected, the antenna morphs to the flattened state and is pointed at the signal source. Extra gain means you can increase bandwidth of a digital signal.

samstave 3y ago
>>>*"the antenna moves to a flattened state to try to reach a satellite capable of receiving cell communications." Sounds just like what Starlink is going to need for the direct to cell service they just tested! But your point of mobile mounting this sounds pretty great, and obvious when its pointed out, actually. I hope this does good things. Hopefully its something that anyone can make and doesnt need to pay some high fee to benefit from.