View Full Version : X-Band Motion Detector-narrow field

Jeff R
02-21-2010, 10:47 AM
Hello, could an aperture like barn doors (or some type of waveguide) be used to narrow the field or spot that is detected for the X-Band Motion Detector?
I would like to use this to detect if an object passes through a narrow area such as a car entering a driveway using the X-Band Motion Detector mounted high above.
Or, to detect birds passing through an area.
Thank you, Jeff

02-21-2010, 05:45 PM
Not sure if this will help or not, but I had a problem with limiting my motion detector to a certain area. To limit the line of sight I used a small piece of pipe and put the motion detector inside of it. I havent tested it on longer lengths of pipe but a 2 inch piece works very well.

02-22-2010, 04:07 AM
I belive that you could limit the area, but it might be complicated. on the shop page for the x-band detector it says it can detect movements on the other side of a wall.

Ron Czapala
02-22-2010, 06:24 AM
It detects me moving thru 2 inside walls across a hallway! I also wondered about focusing it. Not sure if a metal tube or maybe a parabolic dish might be a way to make it more directional...

Jeff R
02-22-2010, 08:25 AM
I was thinking of using 2 flat parallel aluminum fins to narrow the field.

Ron Czapala
02-22-2010, 08:45 AM

I'd be interested in your result. I wonder if angled outward might be better - not sure if the waves might bounce back and forth if they are parallel.

Trial and error might be the best approach...

Jeff R
02-22-2010, 11:59 AM
I haven't bought the sensor yet.
Still in the brainstorming process.

02-23-2010, 08:46 PM
A couple things to try.
A horn antenna might help with directionality.
Part of my wonders about putting some parasitic elements in front of it to draw out the beam.

You could use a parabolic dish and then built up an edge around it...then stick something on that edge to absorb/refract the RF (called a clutter shield)..this would limit what would spill over the side of the dish and reduce side-lobes.


What's the best thing to do in a lightning storm? "take a one iron out the bag and hold it straight up above your head, even God cant hit a one iron!"
Lee Travino after the second time being hit by lightning!

11-28-2011, 06:21 PM
Feeding a dish or a horn antenna with the existing patch antenna on the module creates many other technical issues. Try it, but don't be disappointed if it doesn't work well.

To limit the field of view, put the unit into a metal pipe. This creates swr and reflection/return loss issues, but it will limit the field of view.

A more technically correct solution is to use a coffee can or similar metal tube/pipe with end cap, but to line the back and sidewalls with microwave absorbing material. Using the absorbing material prevents/minimizes swr and return loss issues which will upset the proper operation of the microwave mixer inside the rf module.

The rf module is very quick and dirty with respect to design and functionality. So, don't get to carried away with improving it....some mods might make it perform even worse than it does already::>