WBX daughterboard

Revision as of 10:33, 13 May 2010

This is a recent USRP transceiver daughterboard, released in January 2010. It can cover frequencies from 50MHz to 2.2GHz for reception or transmission (max announced power ~100mWatts).

This makes it the ideal board to cover broadcast frequencies. It was used successfully to generate DAB or FM signals.

Introduction

We immediately purchased several units and try them ! The main feature of this board is the wide coverage, from 50 MHz until 2.2 GHz ! It include 2 RF ports One for RX and TX the second for RX only. The card provide filter, LNA...

Using the updated version of the CRC-Dwap player (frequency offset etc.) we achieved to get a clean signal up to 10 mW on the band 3. Playing with the gain allow us to trim from 1 uW (g = 0) to 10 mW (g = 20)

Pay attention that you need to run the branch 3 of GNU Radio (we run 3.3.x) to use this board otherwise it will not be recognized on your system.

Test with DAB modulator

The measurement is done under the same conditions as for the Basic TX and modified RFX400 (See Example of RF amplifier for DAB) Using CRC MMBTools. The output = 8 mW

The WBX output without any additional filtering, the picture show the spectrum starting at 0 Hz until 3 GHz : We clearly see the upper harmonics...

Then the same with one filter cell :

Looks good !

Now a closer look on the OFDM group : No LO Leak and image frequency.

On a 2 Mhz channel slot, checking the signal envelope :

Using this board with external filters and feeding the amplifier, we achieve a good linear 15 Watt output.

Simulating the reception of two DAB multiplex with the antenna near the transmitter dummy load (a few cm) : Receiving the public service (left signal, SFN from a transmitter located on a mountain at 30 Km and a second one from the city center at the TV tower at 6 Km). On the right picture area the leak from the dummy load. At the time of the photo 15 Watts was feed to the dummy load.