How to detect radar waves (x band)

Hi guys,

I am working on a project that requires radar wave detection. I have a source that emits with a wavelength of 31 mm and a frequency of 9.6 GHz. I am not only interested in detection but also in signal strength.
Is there a module that allows me detect these kind of radio waves (x band), or can I (easily) make one?

I found the Parallar x-band motion detector, but this works on 10.5 GHz, so I am not sure it will pick up my 9.6 source.

I am just getting started with radar, so any information is greatly appriciated.
Thanks for your help in advance!!

How sensitive does the receiver need to be ?

ie how much power are you transmitting power and what range do you need to detect, is the beam focussed etc

Thanks for your reply.

I didn't mention this initially because it sound kinda crazy, but I want to detect satellite radar signals, terrasar-x to be more specific. I am using this satellite for research and I want to know exactly when it passes over (and some other stuff).

So the distance to the transmitter is around 500km, but I expect the signal will be quite strong, because the return signal is measurable, so the signal is generally able to travel 500km back. The beam is highly focussed and has a size of 25x25 cm, at my measurement point.

Do you think this signal is easily detectable?

With the right equipment yes. As you pointed out, radar detectors have a much easier time of it than the radars themselves.

You can arrange for the satellite to shoot at your location?
So you work for the operator of the sat?
Don't you guys already have some fancy equipment that does what you want?

They are expensive.

Given that you are picking up a transmitted radar pulse there will be plenty of power.

You can build one yourself with a mixer diode and a bit of waveguide.

Be aware its a metal bashing job not a circuit board and solder.

Google on solfan module .

Here is another possibility
http://www.markimicrowave.com/M1R-0920-General-Purpose-Double-Balanced-Microwave-Mixer-P219.aspx

Edit the parallax unit appears to use a pcb aerial, frequancy is determined by layout so i doubt if it could be modified for your use.
Its an old design from the 80s developed by the ameteur 3 cm fraternity.

Iv just reread that thread and realised something.

It will only work once, when it passes over your house.

Its a mapping satellite and after it had a look it wont be back

Or are you trying to intercept the telemitry ?

With the beam width you described, it sounds like the chances of being directly in the path of the beam is minimal.
So the signal strength outside of the beam is likely to be much much lower than you imagined.

I think you would be better off posting to a Ham radio forum, as what you want to do, sounds similar to some of the Earth Moon Earth, stuff that used to be tried as a method of communication. Aka EME

But EME is on lower freqs from what I recall, I.e around 2ghz I think

wiredo:
So the distance to the transmitter is around 500km, but I expect the signal will be quite strong, because the return signal is measurable, so the signal is generally able to travel 500km back. The beam is highly focussed and has a size of 25x25 cm, at my measurement point.

Do you think this signal is easily detectable?

I can't believe that a radar signal can travel 500km and be focussed on an area of only 25cm x 25cm.
If it really is then you need to be very lucky to be in exactly the right place.
I would have though you were more likely to win the lottery than detect that signal

even if its 1km wide, detection would be difficult.

Even if you manage to detect the radar signal, what do you expect to gain from it?
You won't be able to see an 'image'. The image is built up from the reflections received by the satellite.
All you will be able to detect will be a series of pulses, or a carrier wave.

Doppler shift?

mix down from xband to around 1ghz and use

JohnLincoln:
I can't believe that a radar signal can travel 500km and be focussed on an area of only 25cm x 25cm.
If it really is then you need to be very lucky to be in exactly the right place.
I would have though you were more likely to win the lottery than detect that signal

Nope it will still have a gaussian distribution.

With SAR and DSP however the result of the distance measurment replicates the 25 by 25 cm resolution.

Total rocket science.

I guess the real information required is the minimum signal strength at the surface of the earth that will be required to receive.

It been a while since I was involved in any radio work, so I’m not sure what the units are.

is it DBm

Its probably calculatable, but you’d need to know the emitted power, and the antenna characteristics, as well as the attenuation over a 500km path (some of which would be through air), as well as the worst case distance between the centre of the transmitted power distribution and the receiver. etc

The key is the basic radar equation.

(and it is dBm, not DBm. The unit is decibels above 1 mW into 50 ohms.)

Thanks Keith

I was just cutting and pasting the url and didn't notice the case of the D was wrong :frowning:

I have played with X and K band microwave for a long time, with Gunn transceivers and with Dielectric-resonant Oscillators. Sometimes, I have exchanged the Gunn diode with a mixer diode in a cavity, just so it will receive, but this is really an old technology and I don't like to play with plumbing. I guess if I were to try and detect X-band today, I would use a patch antenna and a surface-mount detector diode, biased with 3 volts through a very large resistor to get the diode to its most sensitive detection range.. let me know if you want to pursue this and I could maybe draw out a simple design...

rogerClark:
Thanks Keith

I was just cutting and pasting the url and didn't notice the case of the D was wrong :frowning:

No problem, I forgot the /pedantic tag.

I think the 'm' is the important one. Not much call for dB relative to 1 Megawatt. 8^)

First of all, thanks for all the great responses!!

Second I want to clarify: I don't work for nasa/esa/dlr, I just sometimes request data (everyone can do that, for a fee). This type of satellite works by sending a signal and then measures how much of the signal returns. It does this for every 25x25 cm patch in a 2x3 km area. So regardless of my position I should be able to detect the signal. I want to detect this signal (and its strength), at one of these 25x25 cm pixels (I don't want to build a map).
I am not sure I can calculate the power on the ground, since there are many variables affecting this (and I might not be able to find values for all), so I would prefer to have a highly sensitive detection device, and then just try if it works (or is this unrealistic?). As to the suggestion to convert it from 9.6 to 1GHz data, I am not sure that would solve the problem, because it still requires capturing the 9.6 data.

@Muxtech, I really like your idea (as far as I understand it), a simple design would be great. Also do you have any idea how big the patch antenna would need to be, or do I have to calculate the power on the ground for that?

Thanks again for all your help.

9.6 10 1 ghz.

This is called down conversion and just the way recievers work.

Once at 1 ghz those devices are cheap and can decode just about any signal in software.

I know how to do the plumbing as i used to do it for a living.

Patch aerials, i have no idea how to do those.

Muxtech , id be very interested to see how that is done as well