I study SDR using USRP1 and I always start from Hardware.
USRP Daugherboard: BasicRX¶
http://gnuradio.org/redmine/projects/gnuradio/wiki/UsrpDBoardBasicRX
Specifications
RX: 1MHz - 250MHz
TX: N/A
The BasicTX and BasicRX are designed for use with external RF frontends as an intermediate frequency (IF) interface. The ADC inputs
and DAC outputs are directly transformer-coupled to SMA connectors
(50Ω impedance) with no mixers, filters, or amplifiers.
The BasicTX and BasicRX give direct access to all of the signals on the daughterboard interface (including 16 bits of high-speed digital I/O, SPI and I2C buses, and the low-speed ADCs and DACs), and as such are useful for developing your own daughterboards or custom FPGA designs.
NOTE: It is possible for the BasicRX board to go down to 100kHz, but YMMV.
Subdevices¶
This clarification is very important:
While the BasicRX has two antennas (A and B), the driver presents 3 subdevices: 0, 1 and 2.
Subdevice0 is the antenna A, Subdevice1 is the antenna B. You can use both subdevice 0 and 1 at the same time on two different ddc inputs and tune them separately. These subdevices are used as real inputs, and the Q inputs to the ddc are set to zero.
The third possibility is to use subdevice2 which treats the antenna A and B as a single complex input (I and Q), and connects them to the I and Q inputs of the DDC input0. When using subdevice2, you cannot use subdevice 0 and 1.
(Thanks to Josh Blum for the clarification)
I always have a question what is the DDC input0. So,I find a descriptive picture on FPGA
Yeah, you see it......DDC0 is the DDC input0.
