UWB radar experts: Please, I need your advice ...

Hi to all,

I'm involved in a simple design of an UWB radar for short range motion detection (less than 30m). I wish to avoid the patch antenna design and I've found a provider that offers Patch Antennas from 3.5 to 5.9 GHz but in the list of applications there is not UWB.

I list a summary of the antennas and the recommended aplications from the provider:

? 3.5 GHz 8 or 14 dBi Patch Antennas for 802.16e, WiMAX
? 4.9 GHz 11 dBi Patch Antennas for US Homeland Security & Public Safety Program
? 5.3 GHz 8 or 11 dBi Patch Antennas for 802.11a, WiFi
? 5.4 GHz 8 or 11 or 22 dBi Patch Antennas for 802.11a, WiFi, RLAN, FWA, WiMAX
? 5.8 GHz 8 or 11 or 19 dBi Patch Antennas for 802.11a, ISM, UNII, WiFi, Mesh Networks

? 4.4 GHz to 5.5 GHz 8 dBi Broadband Patch Antenna
- Homeland Security
- Public Safety Services: Fire, Police, Security
- Rapid Deployment Installations
- Large Scale WLL
- Personal Area Network (PAN)
- WLAN / Hot Spot
- WLAN / On-Scene Incident Command
- 5.3 GHz Band Applications
- IEEE 802.11a Wireless LAN
- WiFi

? 5.1 GHz to 5.8 GHz 22 dBi Broadband Patch Antenna
- 5.3 GHz Band Applications
- 5.4 GHz Band Applications
- Unlicensed European 5.4 GHz Band Applications
- IEEE 802.11a Wireless LAN
- WiFi Systems
- WiMAX Technology
- 5.8GHz UNII applications
- 5.8GHz ISM applications
- 5.8GHz Wireless LAN systems
- 5.8GHz WiFi application
- 5.8 GHz Wireless Video Systems

? 5.1 GHz to 5.9 GHz 8 dBi Broadband Patch Antenna
- 5.3 GHz Band Applications
- 5.4 GHz Band Applications
- Unlicensed European 5.4 GHz Band Applications
- IEEE 802.11a Wireless LAN
- WiFi Systems
- Radio Local Area Networks (RLAN)
- Fixed Wireless Access Systems (FWA)
- WiMAX Technology
- 5.8GHz UNII applications
- 5.8GHz ISM applications
- 5.8GHz Wireless LAN systems
- 5.8GHz WiFi application
- 5.8 GHz Wireless Video Systems

? 5.4 GHz to 5.8 GHz 19 dBi Broadband Patch Antenna
- 5.4 GHz Band Applications
- Unlicensed European 5.4 GHz Band Applications
- IEEE 802.11a Wireless LAN
- WiFi Systems
- Radio Local Area Networks (RLAN)
- Fixed Wireless Access Systems (FWA)
- WiMAX Technology
- 5.8GHz UNII applications
- 5.8GHz ISM applications
- 5.8GHz Wireless LAN systems
- 5.8 GHz Wireless Video Systems

My questions are:

a) Can I use any of these antennas to my design?
b) If the previous question is afirmative, Are the broadband models better than the one band?


Thanks in advance,

I would start by defining the requirements for the antenna

center frequency
bandwidth
gain
SLL
s11

size
power capacity (might be an issue with a redar)
feed

etc.


With those parameters in hand it then makes sense to look at the anyennas you list to see if any of them are useful. Just a warning patch antennas are not generally particularly broadband and will often not work well in a UWB application. There are exceptions.

Hi Azulykit,

Thank you for your fast answer. Well, I don't know some of your questions but I need that de prototype works some meters, after, I will look for good performances.

Tipically 5.8 GHz, but I can change it from 3.1 to 5.9 GHz
In UWB, BRF>25% of fc, so for [quote]fc=5.8 GHz BRF>5.8/4 = 1.45 GHz
That's a prototype for less of 30m so initially any gain will be good
I don't know what's this
I don't know what's this

No problem, that's a prototype
Micropulse Peek Power 2W, average power 2mW
Mmmm, I know the concept "patch feed" if you say that, I think I don't need to know it but if there is another concept...


Well, that comment answer my second question because you can see that there are some model calified as "Broadband Patch Antenna"

Tell me more comments, please,

Mmmmmm, hi guys, Really there are not UWB experts in this forum?

Please, I need your advice!

Patch antennas are narrow band and will not pass the UWB pulses. You will be stuck with a wideband antenna such as a horn (medium gain) alone or a horn feeding a parabolic reflector (high gain) or an equalangular spiral (low gain).

At lower frequencies you may be able to use a log periodic antenna.

Thanks, flatulent,

If you see my previous list of possible patch antenna candidates, there are some that are calified as "broadband", so, for instance, if I use the 4.4 GHz to 5.5 GHz 8 dBi Broadband Patch Antenna at a center frequency of 4.95, I will have a bandwidth of 1.1 GHz that I think is enough for an UWB Radar application.
That's right?

You need to use an antenna several octaves wide for best results. The antenna you identified will be a good first one to try while you are identifying the wider bandwidth ones. One criteria is the accuracy of the distance you need.

Generally, the inverse of the bandwidth will give you the time resolution limits. Your electronics may also be a time resolution limit.

Patch antenna may work well in your band. Please check BMS web site, they are selling such antenna.

Best regards

The basic attribute of the UWB-aerial have a working strip of frequencies, for example from 0.5 up to 7 GHz.
(I am not expert UWB)

FCC determine UWB as at least 500 MHz wide signal or at least 20% bandwidth. But FCC is considering to change the minimal bandwidth limit to 450 MHz or even less. Definitely, your application can be considerate as UWB. Regarding the possibility to use patch antenna for your band 4.4-5.5 GHz I think that is is not a problem to design such antenna or buy it. You may expect it to be approximately a square with about 2 inches size and have a gain of 8 dB or so. It should be good enough for short range applications.

Best regards

For a radar application like this my first thought would be to try one of the variations of an exponential slot. Look up Vivaldi antennas. They are somewhat directive, relatively easy to build and can cover several octaves so bandwidth is usually not an issue.

Exponential horn antennas are also common with bandwidths from 2 through 18 GHz. ETS/Lundgren has one available and there are other sources for similar antennas. Anticipate gain on the 10 to 12 dBi range and an antenna that has an aperture around 5" by 7" and about 9" long. That is another good option and it can be purchased. Instant gratification. It does not get better than that. This horn is probably even better than the exponential slot as a solution.

I see no power issue with the levels you cite. You are unlikely to cause these antennas grief. The horn and Vivaldi also do not have the potential for group delay problems that you may see in other more conventional broadband antennas. I do not have direct experience with LPD in an ultra wideband radar context (I have used them elsewhere extensively) but I regularly see warnings in the literature that they can be quite dispersive.

If you go into the FCC part 15 subpart F stuff make sure you are looking at the sections that relate to radar applications.

Another thought, if you are considering an array based solution I would look at the feed structure carefully to make sure that it is a corporate rather than series feed. The beam forming needs to be time delay based rather than phase delay based. Look at the 18 dBi patch array you cite as a candidate in this context.

For UWB applications
I have seen people using Pyramidal HORN, ROD antennas.
The frequency they used was 5.8GHz because this comes in ISM band.
U can find tutorials & design programs for Horn on this forum.

Abhishekabs

Added after 5 minutes:

In 5.8GHz band +/- 75 MHz shift is allowed.