Can wireless radios be joined by direct wire connection?

Question

I have an off the shelf device that uses 802.11 wireless for connectivity and nothing else. My system makes heavy use of wireless communications and I would like to incorporate this device into my system without further degrading the RF environment.

Is it possible to create a wired connection between the antenna connector of my device and the antenna connector of another device, and avoid poluting the RF environment with the communications between these two devices?

If so what are the requirements (line impedance or shielding, etc)?

Answer 1

It should be possible, I haven't done it with wifi but I have done it with 802.15.4. A few things to consider

1. too much signal may overload or even damage receivers. I would suggest putting a 20dB attenuator on each device (giving 40dB between any two devices) to keep the signal levels down.
2. Ideally the impedance of all components should match but it's more important for the attenuators to be matched to the cable than for the attenuators to be matched to the device. I doubt you will have any problems if you use standard 50 ohm components.
3. there may also in some cases be DC on antenna connections. It may be prudent to include a DC block in addition to the attenuator.
4. if you want more than two devices you will want splitters that pass signals from every port to every other port. When I last went shopping for splitters to do something like this I could not find any commercial splitters that were designed to do this. I ended up building a simple resistive splitter myself. More details of the splitter I built can be found in an appendix of my phd thesis https://www.escholar.manchester.ac.uk/uk-ac-man-scw:224292
5. the devices are likely to be fairly leaky of RF. While a cabled set up will result in less RF emissions than putting antennas on the devices there will almost certainly still be detectable RF emissions.

I would expect that provided you use reasonable quality coax designed for the frequency band in question (i.e. LBC240 or similar) that you will get far less RF leakage from the coax than from the devices.

Answer 2

Yes, you can do that, but:

• You will almost certainly need to add an attenuator between the two devices. In most RF systems, transmitters produce enough power to destroy receivers if directly connected. (The attenuator will work in both directions.) You should also reduce their transmit power settings, if any, for efficiency and to need less attenuation.

• There may be more leakage than you expect from parts of the device other than the antenna port, since usually that would not be a problem in the design. You may need to add shielding to achieve your goal.

• As you already noted, you need the appropriate impedance for the cable, and attenuator. This could be complicated if the two devices have antenna ports of differing impedances, but this is unlikely.

Answer 3

If you have the correct cables it would work, just like your traditional cable TV systems.

If you are connecting two 802.11 systems why not just forgo the "wireless" equipment entirely and just go with twisted pair Cat. 6 cable?