Hi All,
I've been having problems sending a 25 Msym/s BPSK stream between two
USRP2's with XCVR2450 daughterboards. I've tracked it down to the Rx
circuitry limiting the passband to ~14 MHz when at least 20 MHz should
be available.
Sifting through the db_xcvr2450.c/db_xcvr2450.cc files, I think there
may be a bug which causes the baseband LPF in the MAX2829 device to
cutoff at 7.5 MHz instead of 9.5 MHz when the board is configured for Rx.
Referring to "LPF Register" on the MAX2829 datasheet, the old code...
static void
set_reg_lpf(struct db_xcvr2450_dummy *db){
int reg_lpf = (
(db->common->d_rssi_hbw<<15) |
(db->common->d_txlpf_bw<<10) |
(db->common->d_rxlpf_bw<<9) |
(db->common->d_rxlpf_fine<<4) | 7);
send_reg(reg_lpf);
}
...seems like it should read...
static void
set_reg_lpf(struct db_xcvr2450_dummy *db){
int reg_lpf = (
(db->common->d_rssi_hbw<<15) |
(db->common->d_txlpf_bw<<9) |
(db->common->d_rxlpf_bw<<7) |
(db->common->d_rxlpf_fine<<4) | 7);
send_reg(reg_lpf);
}
...to be set correctly.
Has anybody else had problems with this? I'm using
txrx_edk10.1_r11370.bin. I don't have Xilinx/EDK tools installed on my
setup, but if someone is willing to build a load with the fix, I can
test it out.
thanks,
Steve