Which is better to reduce radar clutter? High or low frequency?

[pong lenis]

Not a highly technical question but anyway,

I read that lower frequency radar increases clutter,
but then also read that high frequency radar detects smaller objects better, so doesn't that mean high frequency radar increases clutter since it would get more unwanted reflections(from raindrops and such)?

 

[pong lenis]

It's been two weeks, still need an answer.

 

[serpretetsky]

I don't know much about radar, but i'll give a theory:
Using the rain example:
A high frequency radar, like you say, should pickup the individual details better. I'm not sure if there sensitive enough to pickup individual rain drops, but if the rain drops were instead very large ball bearings then I would think it should pick them individually.

A low frequency radar, might not see the balls, and be mostly unaffected by them, however, given dense enough "ball bearing" rain, eventually, the distance between the balls would be smaller then the wavelength of the low frequency radar. When this happens, the "rain" will effectively become a wall that the low frequency radar can no longer penetrate, while the high frequency still will. (think of a microwave mesh, you can see through the mesh with high frequency visible light, but low frequency microwaves cannot get through the mesh)

Again, this is a theory.

 

[lakedude]

I saw something about this on the television.

IIRC they were using higher frequency radar to get higher resolution images, the better to ferret out tornadoes and the like. Problem was penetration. The older low res radar gave a low resolution picture of the entire storm, while the new HD radar only showed the parts of the storm closest to the radar source because the HD radar did not penetrate.

Not sure but that seems like the opposite of what serpretetsky is saying and counter to my common sense. Like serp said you can see visible light in a microwave while the cooking waves get blocked.

This post has been from memory which is not 100% reliable. Must research and discover the truth!

Maybe the HD radar is not higher freq?

 

[pong lenis]

Yes the low frequency radars penetrated storms more than high frequency radars but provided lower resolution; weather radars use lower frequency to locate storms that are beyond other storms cause higher frequency radars can't reach them. I remember it, I read it a few days ago.

But still doesn't explain this:

Low Frequency Radars: Below 900 MHz the target radar cross section increases exponentially, however the increased radar cross section means that there is much more radar return from undesirable sources, such as cloud cover and rain

 

[GWestphal]

As a rule of thumb lower frequencies will have longer range and better penetration at the expensive of lower resolution than high frequency RF, but it is also highly material dependent some will absorb or reflect better or worse at different frequencies.

 

[A5]

In the context of weather radar, "clutter" can be all kinds of things, from bugs to birds to high humidity.

To answer the question, low frequency radars will see less of this clutter than high frequency radars.

The NEXRAD radar network in the US operates in the S band (around 3 GHz) but still has some issues with it. But most sources of clutter are pretty well characterized and can be filtered out with algorithms if needed.

There is talk of supplementing the NEXRAD system with a series of 10 GHz X Band radars to provide better information in the low altitudes, especially near the edges of NEXRAD range. The benefit of these radars is that they are smaller and cheaper than the LF main radars, especially when you aren't asking them to put out tons of power.

But still doesn't explain this:
Quote:
Low Frequency Radars: Below 900 MHz the target radar cross section increases exponentially, however the increased radar cross section means that there is much more radar return from undesirable sources, such as cloud cover and rain

This is saying that the required cross-sectional area for detection increases as the frequency of the radar decreases. So now instead of seeing the thing you want to see, you are only seeing broad strokes like "there is a cloud here" but aren't getting any detail on what is in the cloud. Everything with radars is a tradeoff between finding what you are looking for and being able to get rid of the stuff that you're not.

 

[pong lenis]

In the context of weather radar, "clutter" can be all kinds of things, from bugs to birds to high humidity.

To answer the question, low frequency radars will see less of this clutter than high frequency radars.

The NEXRAD radar network in the US operates in the S band (around 3 GHz) but still has some issues with it. But most sources of clutter are pretty well characterized and can be filtered out with algorithms if needed.

There is talk of supplementing the NEXRAD system with a series of 10 GHz X Band radars to provide better information in the low altitudes, especially near the edges of NEXRAD range. The benefit of these radars is that they are smaller and cheaper than the LF main radars, especially when you aren't asking them to put out tons of power.



This is saying that the required cross-sectional area for detection increases as the frequency of the radar decreases. So now instead of seeing the thing you want to see, you are only seeing broad strokes like "there is a cloud here" but aren't getting any detail on what is in the cloud. Everything with radars is a tradeoff between finding what you are looking for and being able to get rid of the stuff that you're not.

So what you're saying is lower frequency does NOT increase clutter, but simply makes targets indistinguishable from the clutter that persists despite the low frequency?
And low frequency reduces clutter then?