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Rotman Lens

en.wikipedia.org

11–20 of 49 posts

Re: Rotman Lens

#11
post #2

If I understand correctly, is the application of this to quickly switch the direction of sending/receiving? Are there any other applications?

It creates pancake beams so you would usually use a separate Rx and Tx orthogonal to each-other to do imaging.

Re: Rotman Lens

#12
post #2

If I understand correctly, is the application of this to quickly switch the direction of sending/receiving? Are there any other applications?

Basically, it lets you steer a beam very precisely in an arbitrary direction, as if you were physically rotating the transmitting antenna.

Usually you'd need to rotate the antenna or else use a large number of controllable phase-shifting elements to send an output beam in the desired direction. But a Rotman lens lets you use a small number of phase shifting elements to merge a small number of source beams (still > 1, though) into a single precisely-steered output beam.

Re: Rotman Lens

#14
post #2

If I understand correctly, is the application of this to quickly switch the direction of sending/receiving? Are there any other applications?

No, this is to concentrate the radio waves into a desired shape. Stronger in this direction, weaker than that. Think of it very vaguely like a parabolic mirror on a flashlight directing the light vs a naked light bulb putting light out in all directions. (this is a bad metaphor for what's going on but it's the basic idea of the goal) To change the direction you have to physically move the antenna OR have an active ph…

It does do directional steering. No active array components or physical movement are needed.

> If the output ports are connected to individual antennas in an antenna array, this allows shaping the beam in different directions by switching which input port the signal is sent to.

From TFA.

Presumably the geometrical shape of the lens is dictated by solving for useful phase shifts for different input points. Otherwise you could just use a bunch of delay lines.

I wonder if anybody's ever designed a 3D version of this. You might get a wider range of inputs, or more precise steering, by shaping the delays on a non-Euclidean (curved) surface (like a sphere or a saddle).

Re: Rotman Lens

#15
post #2

If I understand correctly, is the application of this to quickly switch the direction of sending/receiving? Are there any other applications?

If you monitored all the inputs simultaneously instead of switching, you could make a low-tech radio-wavelength camera. Presumably with less SNR per "pixel" than you'd get from monitoring just one input though.

Re: Rotman Lens

#17

The type of old school black magick engineering Claude could never.

Oh I dunno. I made a mm-wave radar with a Rotman lens using a generative loop between Python, Rhino, and EM simulation. Pretty sure AI could cook that up.

How was it generative, generative AI?

Re: Rotman Lens

#18

Earlier quoted context omitted.

No, this is to concentrate the radio waves into a desired shape. Stronger in this direction, weaker than that. Think of it very vaguely like a parabolic mirror on a flashlight directing the light vs a naked light bulb putting light out in all directions. (this is a bad metaphor for what's going on but it's the basic idea of the goal) To change the direction you have to physically move the antenna OR have an active ph…

It does do directional steering. No active array components or physical movement are needed. > If the output ports are connected to individual antennas in an antenna array, this allows shaping the beam in different directions by switching which input port the signal is sent to. From TFA. Presumably the geometrical shape of the lens is dictated by solving for useful phase shifts for different input points. Otherwise y…

>It does do directional steering. No active array components or physical movement are needed.

By... plugging and unplugging antenna elements?

It makes a fixed directional antenna element array which is configurable to a small degree by choosing which antenna elements to connect and their spatial arrangement.

The radiation pattern can only change by physically plugging or moving antenna elements.

Re: Rotman Lens

#19
> The principle was first published by Walter Rotman and R. F. Turner in 1963

Astonishing nominative determinism there

Re: Rotman Lens

#20

Earlier quoted context omitted.

It does do directional steering. No active array components or physical movement are needed. > If the output ports are connected to individual antennas in an antenna array, this allows shaping the beam in different directions by switching which input port the signal is sent to. From TFA. Presumably the geometrical shape of the lens is dictated by solving for useful phase shifts for different input points. Otherwise y…

>It does do directional steering. No active array components or physical movement are needed. By... plugging and unplugging antenna elements? It makes a fixed directional antenna element array which is configurable to a small degree by choosing which antenna elements to connect and their spatial arrangement. The radiation pattern can only change by physically plugging or moving antenna elements.

It can be changed electronically and is commonly used that way in LTE and Wi-Fi implementations of Beamforming.
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