Version 8 (Dimitrios Symeonidis, 02/21/2010 04:41 pm)
h1. USRP Daugherboard: [[UsrpDBoardDBSRX|DBSRX]]
+RX+: 800MHz - 2.4GHz
This section contains a collection of notes regarding the DBSRX daughterboard.
The frequency range and maximum and minimum bandwidth given in the MAX2118 is different from the one stated in the datasheet from www.ettus.com. Matt Ettus explains the differences:
h3. 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.
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.
h2. Block Diagram
Nice Block diagram produced by Gregory W Heckler.