Hi Folks,
I'm building a digital spectrum analyser (1Hz to 500Mhz) with a single input but I'd like to switch between multiple input channels (min 3).
Since ONE channel would be analysed at the time I don't see the reason why to complicate the design with multiple ADCs or mess with plugging/unplugging BNCs on the input side. I believe mechanical switches and relays can be forgotten here, so I am looking for a comfortable, low-noise, quality solution which would allow me to either manually or automatically switch between the signals. Actually the latter would be the best: if I could automate the channel selection by the analyser's FPGA.
An analysis would never be less than 1 sec and never takes longer than one minute.
Could you please point me where to start it?
Many thanks in advance
I'm building a digital spectrum analyser (1Hz to 500Mhz) with a single input but I'd like to switch between multiple input channels (min 3).
Since ONE channel would be analysed at the time I don't see the reason why to complicate the design with multiple ADCs or mess with plugging/unplugging BNCs on the input side. I believe mechanical switches and relays can be forgotten here, so I am looking for a comfortable, low-noise, quality solution which would allow me to either manually or automatically switch between the signals. Actually the latter would be the best: if I could automate the channel selection by the analyser's FPGA.
An analysis would never be less than 1 sec and never takes longer than one minute.
Could you please point me where to start it?
Many thanks in advance
Hey Mooly, thanks for the idea mate, that is precisely what I'd need!
Well I remember pin diodes in multiband UHF/VHF tuners... but as to using them from scratch... well you know as much me
Or you can get one of these: HP 59307A http://www.home.agilent.com/upload/cmc_upload/All/EPSG087121.PDF
Which change hands for less than $100 in ebay Agilent HP 59307A Dual VHF Switch SPQT Coaxial Switch DC to 500 MHz | eBay and are very high performance. You could lift the relay board out even and run it from your system. It would take a lot of work to get similar performance from pin diodes or a semiconductor switch.
Which change hands for less than $100 in ebay Agilent HP 59307A Dual VHF Switch SPQT Coaxial Switch DC to 500 MHz | eBay and are very high performance. You could lift the relay board out even and run it from your system. It would take a lot of work to get similar performance from pin diodes or a semiconductor switch.
I would suggest shielded relays if building from scratch, especially reed relays due to their low capacitance. You can even make your own budget coaxial relays with some reed relays, if you are able to remove the reed and wrap it in aluminium foil for shielding. You may need to consider termination of unused inputs depending on what you are connecting it to. If you are going to buy a module though then solid-state switches are better for low-power high-isolation applications like this.
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