What is a Patch Cable?
A patch cable, or patch lead, is a short and flexible coaxial cable designed to connect a larger feeder cable to a user device.
In the case of 4G mobile broadband, traditionally modems have used either a TS-9 or CRC9 connector. These are simple, push-on RF interfaces which provide reasonably good performance up to about 3 GHz, making them suitable for 3G and 4G frequencies.
Industrial 4G modems use the more robust SMA connector as the larger thread-on / screw-on interfacing provides far more mechanical durability.
Both consumer and industrial 4G modems provide two external antenna connectors for the attachment of 2x2 MIMO antennas.
It should of course be noted that modern 4G and 5G modems have evolved far beyond 2x2 MIMO technology and as such many no longer provide the option to connect external antenna. This is due to the fact modern 4G networks use 4x4 and Massive MIMO, making it impractical to connect the required number of antennas. 5G also uses frequencies that ordinary coaxial connections cannot handle. mmWave 5G requires waveguide interfaces, a technology far too impractical and costly to support.
Patch cables are of course not limited to mobile connectivity. Many other technologies such as WiFi and point to point wireless use short patch cables to interconnect active and passive components.