Author Topic: Advice on SDR architectures for low noise L-Band reception?  (Read 708 times)

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Offline rwgast_lowlevellogicdesin

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Advice on SDR architectures for low noise L-Band reception?
« on: March 31, 2017, 05:54:19 pm »
So I want to build a receiver specifically for use with radio astronomy and hobby deep space network experimentation. Ive noticed a lot of guys out there doing satcom and such are using nice direct conversion  HF SDRs with down converters in front. So this got me thinking if someone were to build an SDR from scratch for low noise microwave reception what would be the best route? I two different thoughts and Im not really sure wich path to follow or if either is the best way.

First idea is kind of a dual conversion unit. The idea is to build a highly capable 1-50mhz or so HF SDR and use it primary as an IF for an L-Band/10.6ghz down converter. This route allows one to use a lot of quality stuff not available at microwave frequencys, and much easier filtering. Ive never seen anyone do it but I was thinking that using two H-Mode mixers like these https://www.sv1afn.com/fsa3157hmodemm.html would make for a killer quadrature detector which would then pipe in to a 16 or 24bit high speed adc and off to the DSP stage. And of coarse in front of the basically HF SDR one would switch in high quality down conversion units for each band.

The second idea, and im not even sure if it would work would be to make a direct conversion unit that covers 1420-1700mhz or maybe make a few different tayloe detectors, one for each microwave frequency. From what I understand the center frequency the tayloe detects is equal to the speed at witch the I,q,i-,q- are switched at? So how could one switch the detector at microwave frequency's? Then obviously pipe that straight in to a hi res hi speed ADC.

So im not really sure which route is going to be the best to start down, I know doing something may get pretty pricey but thats not really the concern here its designing the SDR possible for space use without using JPLs crazy cryogenic ruby pre amps and active super conductor based mixers etc etc...
 


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