WBX for use in the USRP from Ettus research. Here mostly used with gnuradio. Based on board revision 2 (WBXv2).
First bandpass filter
The TX/RX port has a lowpassfilter. It is labeled FIL1 on the simple_gdb. RX2 does not have the filtering.
CW sensitivity is -130 dBM.
max 100 mW / +20 dBm
(as controllable from GRC)
Tx gain: 0 - 25 dB (step 0.05dB) Rx gain: 0 - 31.5 dB (step 0.5dB) Freq range: 68.75 Mhz - 2.2 Ghz
TX gain is set by PGA0. It is converted from decibels to volts and then sent to the AUX_DAC_A. This is connected to the VSET input of the Quadrature modulator (U501 = ADL5386)
In AGC (ALC) mode the VSET is combined with output from the internal log detector, and sent to the "Voltage variable attenuator" (VVA). The control voltage of the VVA is measured with the AUX_ADC_A.
Reading the VVA controle voltage in gnuradio companion
Put the snippet below in dboard.xml in the directory .grc_gnuradio and restart gnuradio_companion.
<?xml version='1.0' encoding='ASCII'?> <block> <name>dboard</name> <key>dboard</key> <category>Custom</category> <import>from gnuradio.uhd import dboard_iface</import> <make>$(id) = self.$(block_id()).get_dboard_iface(); </make> <param> <name>Block ID</name> <key>block_id</key> <value>my_block_0</value> <type>string</type> </param> <doc>Block ID points to a UHD USRP Sink</doc> </block>
Create a block type "Function Probe" with the following parameters:
|Block ID||wbx||The ID as given in the 'dboard' block.|
Block "Static Text" :
Create a block type "dboard" from the category "Custom" with the following parameters:
|Block ID||usrp_sink||this is the block id of the relevant usrp_sink|
I am wondering whether the FPGA puts the receive attenuator into attenuation mode during transmit when the receive antenna is TX/RX. If this does not happen, then this MGA62563 sees about 1mW of power through leakage from the T/R switch during full-power transmit (the isolation of the switch can be as low as 21dB), which means that it will generate about 20dBm of output, enough to blow out the MGA82563, if we are to believe its maximum absolute rating of 13dBm. During full duplex operation I think that the situation is better, because now MGA62563 sees the transmitter through two switches, or about 40dB of isolation.