Daughterboards
On the mother board there are four slots, where you can plug in up to 2 RX basic daughter boards and 2 TX basic daughter boards or 2 RFX boards. The daughter boards are used to hold the RF receiver interface or tuner and the RF transmitter. There are slots for 2 TX daughter boards, labeled TXA and TXB, and 2 corresponding RX daughter boards, RXA and RXB. Each daughter board slot has access to 2 of the 4 high-speed AD / DA converters (DAC outputs for TX, ADC inputs for RX).
This allows each daughter board which uses real (not IQ) sampling to have 2 independent RF sections, and 2 antennas (4 total for the system). If complex IQ sampling is used, each board can support a single RF section, for a total of 2 for the whole system. Normally, we can see that there are two SMA connectors on each daughter board. We usually use them to connect the input or output signals. No anti-alias or reconstruction filtering is provided on the USRP motherboard. This allows for maximum flexibility in frequency planning for the daughterboards.
Every daughterboard has an I2C EEPROM (24LC024 or 24LC025) onboard which identifies the board to the system. This allows the host software to automatically set up the system properly based on the installed daughterboard. The EEPROM may also store calibration values like DC offsets or IQ imbalances. If this EEPROM is not programmed, a warning message is printed every time USRP software is run.
Each TX daughterboard has a pair of differential analog outputs which are updated at 128 MS/s. The signals (IOUTP_A/IOUTN_A and IOUTP_B/IOUTN_B) are current-output. Also Each RX daughterboard has 2 differential analog inputs (VINP_A/VINN_A and VINP_B/VINN_B) which are sampled at a rate of 64 MS/s.
Basic TX/RX Daughterboards
Each has two SMA connectors that can be used to connect external up/down tuners or signal generators. We can treat it as an entrance or an exit for the signal without affecting it. Some form of external RF front end is required. The ADC inputs and DAC outputs are directly transformer-coupled to SMA connectors (50? 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). Each of the Basic TX/RX boards has logic analyzer connecters for the 16 general purpose IOs. These pins can be used to help debugging your FPGA design by providing access to internal signals.
Low Frequency TX/RX Daughterboards
The LFTX and LFRX are very similar to the BasicTX and BasicRX, respectively, with 2 main differences. Because the LFTX and LFRX use differential amplifiers instead of transformers, their frequency response extends down to DC. The LFTX and LFRX also have 30 MHz low pass filters for anti-aliasing.
TVRX Daughterboards
This is a receive-only daughter board. It is a complete VHF and UHF receiver system based on a TV tuner module. The RF frequency ranges from 50MHz to 860MHz, with an IF bandwidth of 6MHz.
All tuning and AGC functions can be controlled from software. Typical noise figure is 8 dB. This board is the only USRP daughterboard which is NOT MIMO capable.
DBSRX Daughterboards
Similar to the TVRX board, this is also a receive-only. It is a complete receiver system for 800 MHz to 2.4 GHz with a 3 -5 dB noise figure. The DBSRX features a software controllable channel filter which can be made as narrow as 1 MHz, or as wide as 60 MHz. The DBSRX is MIMO capable, and can power an active antenna via the SMA.
RFX Daughterboards
The RFX family of daughterboards is a complete RF transceiver system. They have Independent local oscillators (RF synthesizers) for both TX and RX which enables a split-frequency operation. Also, it has a built-in T/R switching and signal TX and RX can be on same RF port (connector) or in case of RX only, we can use auxiliary RX port. Most boards have built-in analog RSSI measurement. All boards are fully synchronous design and MIMO capable. For RFX daughterboards RF frequency range, check: Ettus Research
For detailed reference and images, check the List of USRP daughterboards
