Re: [Discuss-gnuradio] [USRP-users] Phase alignment for multiple USRP

[Michael West]

Hi Jack,

The set/clear_command_time() functions have a parameter for the mboard that defaults to 0 in gr-uhd.  Try adding calls for the other mboard.  Also, if using frequencies between 500 MHz and 950 MHz on the UBX, you need to add "dboard_clock_rate=20e6" to the device arguments.

Regards,

Michael

On Fri, Jun 16, 2017 at 10:06 AM, Jack Yang via USRP-users <address@hidden> wrote:

I am trying to build a coherent phase array receiver. I am using two X310 with four UBX-160 and a ocotoclock (10MHz and 1PPS) to have 4 Rx coherent receiver. However, every time when the machine is on, the phase offset between each receiver is aways random. I used the python to write my system and I have the following setups. Could anyone give some hint or suggestion how to make coherent phase arrayed receiver work without non-consistent phase offset every time?

Many thanks for your time!

All Best,

Jack

"""

        self.uhd_usrp_source_0.set_clock_source('external', 0)

        self.uhd_usrp_source_0.set_time_source('external', 0)
        self.uhd_usrp_source_0.set_subdev_spec('A:0 B:0', 0)
        self.uhd_usrp_source_0.set_clock_source('external', 1)
        self.uhd_usrp_source_0.set_time_source('external', 1)
        self.uhd_usrp_source_0.set_subdev_spec('A:0 B:0', 1)
        self.uhd_usrp_source_0.set_samp_rate(samp_rate)
        self.uhd_usrp_source_0.set_time_unknown_pps(uhd.time_spec())

        cmd_time = uhd.time_spec_t(0.1) 
        timenow = self.uhd_usrp_source_0.get_time_now()

        self.uhd_usrp_source_0.set_command_time(timenow + cmd_time)           self.uhd_usrp_source_0.set_center_freq(freq, 0)

        self.uhd_usrp_source_0.set_gain(gain, 0)
        self.uhd_usrp_source_0.set_antenna('TX/RX', 0)
        self.uhd_usrp_source_0.set_center_freq(freq, 1)
        self.uhd_usrp_source_0.set_gain(gain, 1)
        self.uhd_usrp_source_0.set_antenna('TX/RX', 1)
        self.uhd_usrp_source_0.set_center_freq(freq, 2)
        self.uhd_usrp_source_0.set_gain(gain, 2)
        self.uhd_usrp_source_0.set_antenna('TX/RX', 2)
        self.uhd_usrp_source_0.set_center_freq(freq, 3)
        self.uhd_usrp_source_0.set_gain(gain, 3)
        self.uhd_usrp_source_0.set_antenna('TX/RX', 3)
        self.uhd_usrp_source_0.clear_command_time()

"""

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