Browse Prior Art Database

Adjustable Lightning Protection Resonant Quarter Wave Stub

IP.com Disclosure Number: IPCOM000016662D
Original Publication Date: 2003-Jul-08
Included in the Prior Art Database: 2003-Jul-08
Document File: 3 page(s) / 1M

Publishing Venue

Motorola

Related People

Robin Tingey: AUTHOR

Abstract

Lightning stubs are implemented on the front end of various types of RF receiver to protect the rest of the equipment from damage in the event of a lightning strike on the Antenna. This article describes a lightning protection stub that has been built in such a way that its resonant frequency can be adjusted. This feature has been previously unavailable on earlier designs.

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Adjustable Lightning Protection Resonant Quarter Wave Stub

by Robin Tingey

Abstract

Lightning stubs are implemented on the front end of various types of RF receiver to protect the rest of the equipment from damage in the event of a lightning strike on the Antenna. This article describes a lightning protection stub that has been built in such a way that its resonant frequency can be adjusted. This feature has been previously unavailable on earlier designs.

Problem To Be Solved

When lightning strikes an antenna at a transceiver site (e.g. mobile phone network), it generally flows down the easiest path to ground. Most cell sites are fitted with lightning arrestor protection, which is usually implemented as a spark gap. This can still let through a major voltage surge, which is still large enough to do some real damage to sensitive electronics. Transmitters always transmit via an air dielectric filter or something similar and hence are protected that way from this surge. Some receivers have onboard filtering and are connected directly to the antenna cable and hence need additional protection. A quarter wavelength long shorted micro-strip stub etched into the PCB usually provides this protection. They are different from lightning arrestors in that they are frequency specific and as a short circuit offer greater protection. These lightning stubs need to be tuned carefully to the exact frequency. Any loading they introduce will cause mismatch losses on the receive path and reduce t...