DIY Horn Antenna for the Wi-Fi Band (2.45 GHz)

In this tutorial we will construct a horn antenna for the Wi-Fi band at 2.45 GHz from a sheet of brass. All fabrication steps are explained and measurement results are provided in the last step. The results from a 3D electromagnetic simulation, such the Gain or the Radiation Pattern of this antenna are available here : http://kavea.free.fr

Step 1: Tools and Materials

To build this antenna you will need:

• 1 mm thick sheet of brass or copper
• SMA connector
• 1 mm diameter copper wire
• soldering iron (min 50 W)
• dremel or something similar to cut the sheet
• drill

Step 2: Cutting the Sheet of Brass

In this step you will have to cut out 7 parts of the antenna from a sheet of brass. To do this, use a dremel or similar grinding tool. As usually, pay attention on protection of your eyes and the face since grinding discs can brake. Dimensions (in mm) of each part is visible on the photo.

Step 3: Soldering

To solder obtained parts you should have a good soldering iron or better a soldering station with a power of 50 W or more. Use a point soldering at the beginning in order to slightly join all parts together. When it's done you can solder all joints.

Step 4: Adding an Excitation Monopole

In the last step you will need to build a small monopole. To do this solder an SMA connector to a copper wire in order to get a whole length of 3 cm (see photo, but pay attention on the optical effect, the length is exactly 3 cm !).Then drill a hole of 6 mm diameter 31 mm away from the rear part of the horn (see photo), then solder the monopole.

Step 5: Measurements

Here we provide measurement results for the SWR and the S11 parameter. As we can see from the photo, obtained antenna have a bandwidth (@ SWR=2) between 2.34 GHz and 2.62 GHz.

Comments

[tytower]

So what is the exact length of antenna you used? You say 3 cm but in your picture it looks longer by a few mm . length is critical to results so exactly how long was your test antenna? Additionally what is the basis of your measurement to position the antenna away from the sides? Can you give the source of these measurements please ?

[kavea]

The monopole is exactly 3 cm length, it seems to be longer because of the optical effect ;) Can you clarify your question about measurements ? You are talking about the physical dimensions or the S parameters measurements ?

[tytower]

I mean how do you calculate exactly where to position the antenna relative to the front back and sides?

[tytower]

Oh and I meant to thank you for putting this up . I intended to make one but did not know where to start.

[tytower]

Also if I use alloy sheet will that work also?

[ducatidragon916]

I used galvanized sheet metal and used solder to attach together. it worked fine for my application and then painted the exterior black for cosmetics and it looked manufactured.

[kavea]

Your welcome! The monopole should be placed 31 mm from the back and at the middle from the sides i.e. at 43 mm (86 / 2). This position has been optimized in the 3D FEM solver, but theoretically it's lambda/4 from the back . Any metal sheet will work if you respect the internal dimensions of the horn, an other point is the poor conductivity of some alloys which can lower the gain. And not all alloys are solderable. The best choice still copper, but more expensive than brass.

[syedadsh7.1]

Will the dimensions remain same if we construct it for different frequency let say 5.15Ghz?

[ducatidragon916]

You will need to recalculate with the new frequency the new dimensions. It would be roughly double frequency then roughly half the dimensions......

[kavea]

No, dimensions are frequency dependent

[yshivu]

Nice explaination ....but how can we set the frequency of the horn antenna.

[tytower]

Aditionally . If I use finer copper wire to construct the antenna would I not get a sharper bandwidth?

[kavea]

Yes, the diameter of the wire will change the BW but also the central frequency. However 1mm +/- 0.5mm will not affect a lot the result.

[martis2580]

Which software do you use to simulate horn antenna?

[dthurston1]

Nicely done... so the next question .... how does one deal w/dual band wi-fi ...? Diplexer?

DT

[kavea]

In practice a wifi antenna is made to be matched at both 2.45 GHz and 5 GHz (laptops etc). For home purposes it can be done with horn type antennas since it can provide very broadband response. In these two cases you dont need anything. However if you have two different antennas, one for 2.45 and other for 5 GHz band you will need a switch or a diplexer to isolate two antennas. Otherwise their impedances will be seen in parallel from the receiver.

[dthurston1]

Settles that ...

Any comments on mounting and direction ?

DT

[kavea]

Nothing special, as usually do not put it near metallic objects and respect the polarization (usually vertical so put the antenna like on first image, connector up or down)