RSPA1 : Sampling rate vs Bandwidth

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RSPA1 : Sampling rate vs Bandwidth

Postby Hayfa » Mon May 20, 2019 1:02 pm

I would like to know if in the case of the RSPA1 receiver the used sample rate is different from the the bandwidth (When i used other types of receivers , the rtl-sdr for example, these two value are equal).
In the case that the sample rate and the bandwidth must be equal, am i limited to the values enumerated in the API (200k, 300k, 600k, 1536k, 5000k, 6000k, 7000k, 8000k)?
I'm asking this question because according to the RSPA1 gnuradio block , i can select the bandwidth from a limited list of values while i still can choose a different sample rate .
RSPA1 Gnuradio source block
RSPA_gnuradio_sourceblock.PNG (63.9 KiB) Viewed 747 times
Last edited by Hayfa on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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Re: RSPA1 : Sampling rate vs Bandwidth

Postby sdrplay » Fri Jun 07, 2019 5:54 am

The sample rate and IF bandwidth are two different things but they have a relationship to each other.

All RSPs support an arbitrary native sample rate of anywhere between 2 and 10 MHz

The RSPs also have fixed IF bandwidth values of 200, 300, 600, 1536, 5000, 6000, 7000 and 8000 kHz

The general rule is that the sample rate shouldn't be less than the IF bandwidth. You will see some attenuation of the signal outside of the IF bandwidth so it makes sense to use some values such as...

sample rate of 2 MHz and IF BW of 1536 kHz
sample rate of 5 MHz and IF BW of 5000 kHz

what doesn't make sense is to select these values as you will see a large portion of the spectrum attenuated...

sample rate of 2 MHz and IF BW of 300 kHz
sample rate of 5 MHz and IF BW of 1536 kHz

If decimation is used then the same rule applies...

sample rate of 2 MHz with decimation of 2 to give a final sample rate of 1 MHz, so the sensible IF BW to use is 600 kHz

Most of the time applications will link the two parameters and pick a sensible IF BW depending on the final sample rate or visa versa.

Hope that makes sense.

Best regards,

SDRplay Support

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