Radio Frequency (RF) & Wireless Design

You would use an RF device called an "RF Hybrid Ring Coupler" also called a "Rat-Race Coupler" :

https://en.wikipedia.org/wiki/Rat-race_coupler

You could also use a "Magic-Tee" but it suffers from large size, cost, and matching the structures :

https://en.wikipedia.org/wiki/Magic_tee

Richard Barber has created a 'Magic Tee' :

Grabcad model

WR-10 Magic Tee Waveguide

Size WR-10 microwave radio waveguide magic tee radar component

Also if you want to use two different frequencies and just for receiving, then you can also use a simple and common DIPLEXER, which was common for TV sets back in the 50's thru 90's with VHF and UHF antennas :

https://en.wikipedia.org/wiki/Diplexer

This is NOT to be confused with a DUPLEXER, which is used to switch between transmitter and receiver operations : https://en.wikipedia.org/wiki/Duplexer

This is a synopsis of both :

https://www.rfcafe.com/references/electrical/ew-radar-handbook/circulators-diplexers.htm