2007/6/27, Matt Ettus <[EMAIL PROTECTED]>:
Trond Danielsen wrote: > Hi, > > I have a small question regarding the frequency range and bandwidth of > the DBSRX daughterboard from www.ettus.com. According to the > daughterboard datasheet [1] the frequency range is from 800 to 2400 > MHz, and the adjustable bandwidth is from 1 to 60 MHz. However, the > datasheet for the MAX2118 [2] states a frequency range from 925 to > 2175 MHz, and the adjustable LP filter BW is 4 to 33 MHz. > > If someone could provide some information that would enlighten me on > these matters I would be most grateful.Frequency Range: The MAX2118 datasheet says that it covers 925 to 2175 MHz. They spec that because it is the range that their typical customer needs (for small satellite dish IFs). However, I have never found one which doesn't work to the larger 800 MHz to 2400 MHz range. Maxim guarantees 925 to 2175, I guarantee the larger range. Bandwidth: When Maxim states that their maximum LPF bandwidth is 33 MHz, they mean one-sided bandwidth (i.e. 0 to 33 MHz). Since it is used in a direct conversion IQ system, that actually gives a 66 MHz bandwidth (-33 MHz to +33 MHz). Since that is beyond nyquist for our ADC, I spec to 60 MHz (+/- 30 MHz). On the low end, they specify 4 MHz, which is really 8 MHz (+/-4 MHz) of RF bandwidth. The filter is actually capable of going to a much narrow frequency, but it is outside of Maxim's specs, since nobody in the small satellite dish market cares about less than 8 MHz of BW. So I spec that it goes down to 1 MHz wide. It should be noted that when you go below 4 MHz wide (2 MHz in Maxim-speak) that your noise floor will rise a bit and phase noise may also rise. Matt
Hi, Thank you very much for the clarification! I will add this information to the wiki, just in case anyone else wonders about the same. -- Trond Danielsen _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
