I followed the suggestions and plotted the received baseband signal in the IQ constellation. The phase offset of the baseband received by the two RX antennas are still not constant... Attached are the update flow graph and python program. Would be great if you can take a look again. Thanks.
On Thu, Apr 23, 2015 at 3:06 PM, <mle...@ripnet.com> wrote: > If you have the Octoclock-G connected to both units, then you don't need > to use the MIMO cable. > > Make sure that both mboards have "external" for both the reference clock > and pps selections, and that "device time" is set to "unknown PPS" for both > of them. > > > > > On 2015-04-23 14:49, Pengyu Zhang wrote: > > Hi, > > I am working on phase coherent reception using 2 USRP N210s where each is > mounted with a SBX. The 2 N210s are connected via a MIMO cable. 10MHz > reference clock and PPS are generated by an OctoClock-G and are fed into > each N210. In this experiment, a TX antenna transmits a constant signal to > 2 RX antennas. I want to obtain coherent phases at the 2 RX antennas. > Attached is the flow graph I am executing. It seems that I cannot achieve > coherent phase at the 2 Rx antennas. Any suggestions? Thanks. > > Pengyu > > _______________________________________________ > Discuss-gnuradio mailing > listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
mimo_signal.grc
Description: Binary data
#!/usr/bin/env python
##################################################
# Gnuradio Python Flow Graph
# Title: Top Block
# Generated: Thu Apr 23 15:10:01 2015
##################################################
from gnuradio import analog
from gnuradio import blocks
from gnuradio import eng_notation
from gnuradio import gr
from gnuradio import uhd
from gnuradio import wxgui
from gnuradio.eng_option import eng_option
from gnuradio.filter import firdes
from gnuradio.wxgui import scopesink2
from grc_gnuradio import wxgui as grc_wxgui
from optparse import OptionParser
import time
import wx
class top_block(grc_wxgui.top_block_gui):
def __init__(self):
grc_wxgui.top_block_gui.__init__(self, title="Top Block")
_icon_path = "/usr/share/icons/hicolor/32x32/apps/gnuradio-grc.png"
self.SetIcon(wx.Icon(_icon_path, wx.BITMAP_TYPE_ANY))
##################################################
# Variables
##################################################
self.samp_rate = samp_rate = 1000000
##################################################
# Blocks
##################################################
self.wxgui_scopesink2_1 = scopesink2.scope_sink_f(
self.GetWin(),
title="amp scope",
sample_rate=samp_rate,
v_scale=0,
v_offset=0,
t_scale=0,
ac_couple=True,
xy_mode=False,
num_inputs=2,
trig_mode=wxgui.TRIG_MODE_AUTO,
y_axis_label="Counts",
)
self.Add(self.wxgui_scopesink2_1.win)
self.uhd_usrp_source_0_0 = uhd.usrp_source(
device_addr="addr=192.168.10.3",
stream_args=uhd.stream_args(
cpu_format="fc32",
channels=range(1),
),
)
self.uhd_usrp_source_0_0.set_clock_source("external", 0)
self.uhd_usrp_source_0_0.set_time_source("external", 0)
self.uhd_usrp_source_0_0.set_subdev_spec("A:0", 0)
self.uhd_usrp_source_0_0.set_time_unknown_pps(uhd.time_spec())
self.uhd_usrp_source_0_0.set_samp_rate(samp_rate)
self.uhd_usrp_source_0_0.set_center_freq(915000000, 0)
self.uhd_usrp_source_0_0.set_gain(10, 0)
self.uhd_usrp_source_0_0.set_auto_dc_offset(0,0)
self.uhd_usrp_source_0_0.set_antenna("RX2", 0)
self.uhd_usrp_source_0_0.set_bandwidth(2000000, 0)
self.uhd_usrp_source_0 = uhd.usrp_source(
device_addr="addr=192.168.10.2",
stream_args=uhd.stream_args(
cpu_format="fc32",
channels=range(1),
),
)
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", 0)
self.uhd_usrp_source_0.set_time_unknown_pps(uhd.time_spec())
self.uhd_usrp_source_0.set_samp_rate(samp_rate)
self.uhd_usrp_source_0.set_center_freq(915000000, 0)
self.uhd_usrp_source_0.set_gain(10, 0)
self.uhd_usrp_source_0.set_auto_dc_offset(0,0)
self.uhd_usrp_source_0.set_antenna("RX2", 0)
self.uhd_usrp_source_0.set_bandwidth(2000000, 0)
self.uhd_usrp_sink_0 = uhd.usrp_sink(
device_addr="addr0=192.168.10.3",
stream_args=uhd.stream_args(
cpu_format="fc32",
channels=range(1),
),
)
self.uhd_usrp_sink_0.set_clock_source("external", 0)
self.uhd_usrp_sink_0.set_time_source("external", 0)
self.uhd_usrp_sink_0.set_subdev_spec("A:0", 0)
self.uhd_usrp_sink_0.set_time_unknown_pps(uhd.time_spec())
self.uhd_usrp_sink_0.set_samp_rate(samp_rate)
self.uhd_usrp_sink_0.set_center_freq(915000000, 0)
self.uhd_usrp_sink_0.set_gain(10, 0)
self.uhd_usrp_sink_0.set_antenna("TX/RX", 0)
self.uhd_usrp_sink_0.set_bandwidth(2000000, 0)
self.blocks_float_to_complex_0 = blocks.float_to_complex(1)
self.blocks_file_sink_1 = blocks.file_sink(gr.sizeof_gr_complex*1, "/home/vijaykp/rx2_", False)
self.blocks_file_sink_1.set_unbuffered(False)
self.blocks_file_sink_0 = blocks.file_sink(gr.sizeof_gr_complex*1, "/home/vijaykp/rx1_", False)
self.blocks_file_sink_0.set_unbuffered(False)
self.blocks_complex_to_mag_0_0 = blocks.complex_to_mag(1)
self.blocks_complex_to_mag_0 = blocks.complex_to_mag(1)
self.analog_sig_source_x_1 = analog.sig_source_f(samp_rate, analog.GR_CONST_WAVE, 1000, 0.5, 0)
##################################################
# Connections
##################################################
self.connect((self.blocks_complex_to_mag_0, 0), (self.wxgui_scopesink2_1, 0))
self.connect((self.uhd_usrp_source_0, 0), (self.blocks_complex_to_mag_0, 0))
self.connect((self.blocks_complex_to_mag_0_0, 0), (self.wxgui_scopesink2_1, 1))
self.connect((self.uhd_usrp_source_0_0, 0), (self.blocks_complex_to_mag_0_0, 0))
self.connect((self.uhd_usrp_source_0, 0), (self.blocks_file_sink_0, 0))
self.connect((self.uhd_usrp_source_0_0, 0), (self.blocks_file_sink_1, 0))
self.connect((self.analog_sig_source_x_1, 0), (self.blocks_float_to_complex_0, 0))
self.connect((self.analog_sig_source_x_1, 0), (self.blocks_float_to_complex_0, 1))
self.connect((self.blocks_float_to_complex_0, 0), (self.uhd_usrp_sink_0, 0))
# QT sink close method reimplementation
def get_samp_rate(self):
return self.samp_rate
def set_samp_rate(self, samp_rate):
self.samp_rate = samp_rate
self.wxgui_scopesink2_1.set_sample_rate(self.samp_rate)
self.analog_sig_source_x_1.set_sampling_freq(self.samp_rate)
self.uhd_usrp_source_0.set_samp_rate(self.samp_rate)
self.uhd_usrp_source_0_0.set_samp_rate(self.samp_rate)
self.uhd_usrp_sink_0.set_samp_rate(self.samp_rate)
if __name__ == '__main__':
import ctypes
import os
if os.name == 'posix':
try:
x11 = ctypes.cdll.LoadLibrary('libX11.so')
x11.XInitThreads()
except:
print "Warning: failed to XInitThreads()"
parser = OptionParser(option_class=eng_option, usage="%prog: [options]")
(options, args) = parser.parse_args()
tb = top_block()
tb.Start(True)
tb.Wait()
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