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
phase_coherence.grc
Description: Binary data
#!/usr/bin/env python
##################################################
# Gnuradio Python Flow Graph
# Title: Top Block
# Generated: Thu Apr 23 14:46:22 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("mimo", 0)
self.uhd_usrp_source_0_0.set_time_source("mimo", 0)
self.uhd_usrp_source_0_0.set_subdev_spec("A:0", 0)
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_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_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_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("mimo", 0)
self.uhd_usrp_sink_0.set_time_source("mimo", 0)
self.uhd_usrp_sink_0.set_subdev_spec("A:0", 0)
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_0.set_samp_rate(self.samp_rate)
self.uhd_usrp_sink_0.set_samp_rate(self.samp_rate)
self.uhd_usrp_source_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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