Phase Shifting RF-Signal(s) for direction finding using sum/diff

Thread Starter


Joined Jan 26, 2022
Hello guys!

I am not sure if i am in the right forum, but i'll try here anyways.

I am currently working on a direction finding system and have decided to use a 2x2 array using patch antennas. The antenna array will be mounted on a robot arm and the system is described in this thread

Using this antenna constructuion i will need to phase shift one of the patches to get a defined null. We are planning on switching between the null by summing them in diff (Δ) and sum (Σ) to validate and level the direction of the antenna. I have currently ordered a digital switch with 4 SMA-inputs and are planning on designing the PCB-layout.

For now, i have planned on modifying the feed-line by extending it by 1/2 wavelength to brute force the phase shift. But this option makes it hard to have reliable sum/diff measurements. The switch does not measure concurrently and will sequentially switch between all 4 antennas. In other words, we have to do the arithmetic operation digitally, and were not sure if it is even possible to obtain a null using this method, if the signals has to be combined by an analog coupler.

My questions are:
  • I have looked into hybrid couplers, but they are really expensive. So are there any other methods we can use to phase shift the I/O signal 180 degrees?
  • Is it possible to create the defined null (link below for method) while processing the data digitally with the microcontroller that receives the data.
  • Do you have any tips on useful couplers (as i assume you will need to be familiar with the marked to find one)

Method using sum/diff