An adjustable filter that can prevent interference in the range 600 MHz to 6 GHz | Hacker News Reader

An adjustable filter that can prevent interference in the range 600 MHz to 6 GHz

blog.seas.upenn.edu

Not quite: "As a result, the new filter can be tuned to any frequency between 3.4 GHz and 11.1 GHz..."

The 600 MHz to 6 GHz referred to currently used communication frequencies.

I was referring to the interferences range where the filter can work, not where it can be tuned. If I correct understood.

The 600-6GHz range is a rough approximation for some of the most used bands in telecommunications, e.g. Wi-Fi and 5G NR FR1. It's worth noting that the article explicitly mentions that this filter will be useful for FR3, which is "7 GHz to 24 GHz". They do not claim full 600 MHz-6 GHz operation, and as the previous poster noted, the filter was demonstrated from 3.4-11.1 GHz.

More critically: you want to be very very careful about trying to extrapolate this filter down to lower frequencies. We're dealing with "weird physics" here. I am not an expert on spin-wave devices by any means, but a guy in my lab during grad school was working with them, so I do know that the resonant frequencies of the spin-waves are a function of the magnetic bias and the material. The researchers here are tuning the filter by tuning the magnetic bias. Someone more knowledgeable can correct me, but I believe YIG would have trouble propagating spin-waves down at 600 MHz, and so this kind of filter would not be practical.

The main innovation here seems to be the elimination of a bias electromagnet that consumes a constant current to generate a desired amount of magnetic flux.

These apparently can consume 250 milliamp, if my quick Google is right.

Here's a paper[1] that might be how they are doing it.

[1] https://ieeexplore.ieee.org/document/7529113

This kind of work sounds potentially (?) important for continuing to improve network technology. Unfortunately I don't have the background to understand why it works in the slightest.

However, it reminded me of an older approach to signal filtering that I just recently learned about: the superheterodyne radio receiver. It's a simple idea that enabled us to build cheap, tunable radios. YouTube video if you're curious: https://www.youtube.com/watch?v=hz_mMLhUinw. Definitely an accessible introduction to a neat trick in signal processing!

I wonder if you could use this to overcome electronic warfare jamming of gps.

No, this is about preventing unwanted jamming/interference by a transmitter on frequencies it isn't intending or needing to transmit on as part of the design phase of a product. Overcoming intentional jamming is an entirely different ballgame.

There’s a lot of strategies for this but a basic one is using direction find on the jammer. then electronically or manually moving antenna nulls (bad spots of a directional antenna) to face the jammer(s) which would then increase the gain for directed non-jammer areas.

GPS is a very low amplitude signal that can easily be jammed. Dropping WP (white phosphorus) or a missile on the suspected jammer would be a better bet.

> Dropping WP (white phosphorus)

"Your GPS jammer prevented my war crime so here's a bigger war crime." - The good guys

The use of WP against military targets is not prohibited. A jammer is a military target. As long as it's not causing undue damage to civilians, this is not a war crime.

I don't understand the expected military effect of white phosphorus on a RF jammer though…

You don't understand the expected effect of very hot, inextinguishable fire on an electronic device?

Why do you expect the electronic device to be within reach of the phosphorus in the first place?

The antenna would[1], but the valuable electronics has no reason to be left outside, and practically any amount of concrete, rock or even dirt would protect it from WP.

Also, from your description you're probably confusing WP with termite, which is different (but would be equally inefficient again EW devices for the same reason).

[1]: and with WP you're likely going to just damage the wires and not the antenna itself

I agree, I would rather do plain old HE over WP for a jammer. But either case would not qualify for a war crime.

Depends how close they are from the civilian population, as always.

At least with HE you can limit the damage to the particular place that holds the device, when I'm not familiar with any use of white phosphorus through precision munition (I'm far from a munition expert though, so I may be wrong here).

It might be cool, but I wasn’t able to find price comparison to existing technologies. The modules containing dozens of specified filters are dirt cheap. Since band frequencies for 5G are known no fine tuning needed. Also no fab wants exotic materials and a new process.

Yes, this article is marketing. They've just made a prototype smaller filter.

YIG filters have been around for decades. They are electrically tunable. However, they are slow to change frequency and can have an odd phase response.

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