Switch RF signal - Page 1
Forum section: electronics / rf-microwave

author: atom78
author_rank: Newbie
timestamp: August 20, 2018, 01:44:02 am
content: Hey guys,I need to switch a 400-690 MHz signal. The signal is received in an antenna and go through the coaxial cable. The idea is switch the signal, turning it on and off (letting it pass or not) as necessary. I´m using a microcontroller, and I think in doing it with an optoacoupler or a transistor as switch. Anyone know some model of this components that can work well at this level of frequency?Thanks!

author: vk6zgo
author_rank: Super Contributor
timestamp: August 20, 2018, 02:02:14 am
content: Quote from: atom78 on August 20, 2018, 01:44:02 amA PIN diode may do a better job.

author: xaxaxa
author_rank: Regular Contributor
timestamp: August 20, 2018, 03:57:00 am
content: BGS12PL6 is what I use for general purpose antenna switching; it only needs a 3.3V power and control signal. If you want to do SP1T you need to terminate one of the ports with a 50ohm resistor.

author: atom78
author_rank: Newbie
timestamp: August 21, 2018, 03:32:20 am
content: Quote from: xaxaxa on August 20, 2018, 03:57:00 amI didn´t know this chip, it will be much easier than use a transistor or PIN diode. I will look for it and try to work with, thank you very much!

author: rf-fil
author_rank: Regular Contributor
timestamp: August 21, 2018, 04:55:41 am
content: You didn't specify any performance requirements. RF power level? Acceptable loss? Switching time? Power consumption? Isolation in off state?* PIN diodes --> moderate loss, larger power consumption (depends on RF power level being switched), somewhat unique (hard to get) diodes, large RF power handling, larger overall size, moderate linearity.* RF CMOS switches --> abundant (Digikey or any other supplier), low loss, low cost, various packages, nearly zero power consumption, power handling up to about 5W, RX only (<10dBm) chips are very cheap, excellent linearity.* Relays --> range of RF power handling up to huge powers, larger size, can be very expensive for the very high power coaxial relays, but only a few bucks for <1GHz moderate power level SMD relays, excellent linearity.Of the above 3, PIN diodes require the most RF design knowledge to do properly. Not the best choice unless you have to.Using NPN transistors or optocouplers for RF switching at the frequency you specified is nonsense.

author: hwalker
author_rank: Contributor
timestamp: August 21, 2018, 11:34:43 pm
content: An alternate solution is to consider searching on eBay for coaxial rf switches. I usually mount how ever many I need in a "BUD" box, with the control lines connected to bannana plugs that are in turn connected to microcontroller ports. Its a flexible and re-usable setup. The switches can usually be had second hand from 10 - 20 dollars depending on upper frequency range.-Herb

author: Wolfgang
author_rank: Super Contributor
timestamp: August 23, 2018, 12:10:30 pm
content: Hi,a PIN diode switch is elegant. I made one myself with discrete diodes, like here:https://electronicprojectsforfun.wordpress.com/rf-module-gallery/rf-switches/an-rf-pin-diode-switch/but you could use single chip solutions with better results nowadays.If you have very stringent requirements, you probably have to go to coaxial mechanical switches. On eBay you could some for 10-20€ used. They outperform all aother types of electronic switches

author: salbayeng
author_rank: Frequent Contributor
timestamp: August 30, 2018, 09:19:52 am
content: minicircuits make a range of PIN switch moduleshttps://ww3.minicircuits.com/WebStore/Switches.html