Hi All,
in all the examples and in my own gnuradio Programm, there
is an unknown Peak in the FFT-Plot sink.
Here is the Screenshot:
http://img257.imageshack.us/img257/8017/nochstrender.jpg
How to avoid this ?
Wherefrom does this come ?
I attach my Program to this mail, but i think it is still ok.
I need this to measure the power of the noise.
Further on you see the noise has a wave form always in
the middle of the FFT-Plot, still when i watch another
spectrum. In the gnuraio example from Eric Blossom this
doesn't appear, but this example only use a sin-signal-source
not a usrp-source.
How to avoid this ?
I tried to change the decimation and the sample Rate,
but doesn't solved this.
Regards Markus
#!/usr/bin/env python
# encoding: utf8
"""
Title:Mehrfrequentes Impulsmessverfahren mit FPGA-
gestützten SDR-(Software definded radio)-Komponenten.
Beschreibung: Mit Hilfe dieses Programmes soll ein
mehrfrequentes Impulsmessverfahren entwickelt werden,
womit Teilentladungen an Hochspannungsisolationen
nachgewiesen werden können.
"""
__title__='Mehrfrequentes Impulsmessverfahren'
__author__='Markus Feldmann'
__version__='Diplom WS08/09 Ver.:2009-03-09-01'
__license__='GPL'
from gnuradio import gr
from gnuradio import usrp
from gnuradio.wxgui import fftsink2
from grc_gnuradio import usrp as grc_usrp
from grc_gnuradio import wxgui as grc_wxgui
from optparse import OptionParser
from usrpm import usrp_dbid
import sys
import time
import wx
class uebertragungschar_LF_RX(grc_wxgui.top_block_gui):
def __init__(self, options):
grc_wxgui.top_block_gui.__init__(self,
__title__+' - '+__author__+' - '+__version__)
##################################################
# DEBUG
##################################################
self.debug = options.debug
if self.debug is True:
print 'DEBUG: start debug modus.'
##################################################
# Parameters
##################################################
self.usrp_freq = options.usrp_freq
self.usrp_freq_min = options.usrp_freq_min
self.usrp_freq_max = options.usrp_freq_max
self.decim = options.usrp_decim
##################################################
# Variables
##################################################
self.middle_freq_fft_plot = self.usrp_freq
self.gain_usrp_source = 0
"""
The Argument options.dev must be converted into the intern
ID, so that we can select the device. The ID will be saved
in this variable:
"""
self.selected_device = None
##################################################
# Blocks
##################################################
# self.gr_complex_to_real_0 = gr.complex_to_real(1)
self.usrp_source = usrp.source_c(which=0, decim_rate=self.decim)
##################################################
# Further Variables
##################################################
"""
Because we do not know where the LF_RX(for example) is placed, we have
to search for it and select it.
First we have to get the intern ID. For example we search after LF_RX
and get an ID like (1, 0), this means the LF_RX is placed onto
side B and there at RXB.
(0, 0)-->side A/RXA
(0, 1)-->side A/TXA
(1, 0)-->side B/RXB
(1, 1)-->side B/TXB
After we found the device and got the intern ID, we select it.
"""
if options.device=='LFRX':
self.device_found = usrp.pick_subdev(self.usrp_source, (usrp_dbid.LF_RX,))
if self.debug: print 'DEBUG: <self.device_found> is ',self.device_found
self.selected_device = usrp.selected_subdev(self.usrp_source, self.device_found)
if self.debug: print 'DEBUG: <self.selected_device> is ',self.selected_device
elif options.device=='BasicRX':
self.device_found = usrp.pick_subdev(self.usrp_source, (usrp_dbid.BASIC_RX,))
if self.debug: print 'DEBUG: <self.device_found> is ',self.device_found
self.selected_device = usrp.selected_subdev(self.usrp_source, self.device_found)
if self.debug: print 'DEBUG: <self.selected_device> is ',self.selected_device
else:
print 'ERROR: You selected an illegal device named: ',options.device
parser.print_help()
sys.exit(1)
self.mux_value = usrp.determine_rx_mux_value(self.usrp_source,self.device_found)
if self.debug: print 'DEBUG: <self.mux_value>',self.mux_value
"""
We have to calculate the fftp_rate which is equal to the usrp_rate.
At adc_rate=64MS/s and decim=250 we get an usrp_rate of 256 kS/s
"""
self.usrp_rate = (self.usrp_source.adc_rate() / self.decim ) / 2
if self.debug: print 'DEBUG: <self.decim> is ',self.decim
if self.debug: print 'DEBUG: <self.usrp_source.adx_rate> is ',self.usrp_source.adc_rate()
if self.debug: print 'DEBUG: <self.usrp_rate> is ',self.usrp_rate
##################################################
# Futher Blocks
##################################################
# self.gr_throttle_0 = gr.throttle(gr.sizeof_float*1, self.usrp_rate)
self.usrp_source.set_mux(self.mux_value)
self.wxgui_fftsink2 = fftsink2.fft_sink_c(
self.GetWin(),
baseband_freq = self.usrp_freq,
y_per_div = 10,
y_divs = 8,
ref_level = 0,
sample_rate = self.usrp_rate,
fft_size = 512*2,
#fft_rate = 30,
ref_scale=11885000.0,# 11885000.0 oder 32768.0
average = True,
avg_alpha = None,
title = "FFT Plot",
size=(1024, 600),
peak_hold = False,
)
self.GridAdd(self.wxgui_fftsink2.win, 0, 0, 2, 4)
##################################################
# Controls
##################################################
self._usrp_freq_control = grc_wxgui.slider_horizontal_control(
window=self.GetWin(),
callback=self.set_usrp_freq,
label="Oszillatorfrequenz",
value=self.usrp_freq,
min=self.usrp_freq_min,
max=self.usrp_freq_max,
num_steps=1e3,
slider_length=1024,
)
self.Add(self._usrp_freq_control)
self._gain_usrp_source_control = grc_wxgui.slider_vertical_control(
window=self.GetWin(),
callback=self.set_gain_usrp_source,
label="Gain Usrp Source",
value=self.gain_usrp_source,
min=0,
max=20,
num_steps=100,
slider_length=200,
)
self.GridAdd(self._gain_usrp_source_control, 4, 0, 2, 1)
##################################################
# Connections
##################################################
self.connect((self.usrp_source, 0), (self.wxgui_fftsink2, 0))
#################################################
# Set Inital Value
#################################################
self.set_usrp_freq(self.usrp_freq)
self.set_gain_usrp_source(0)
self._gain_usrp_source_control.set_value(0)
def set_usrp_freq_min(self, usrp_freq_min):
self.usrp_freq_min = usrp_freq_min
def set_usrp_freq_max(self, usrp_freq_max):
self.usrp_freq_max = usrp_freq_max
def set_usrp_freq(self, freq):
self.usrp_freq = freq
"""
The usrp.tune command takes 4 arguments, first ist your <Usrp Source>
the second is Digital Down Converter Number mostly 0, followed by the
the selected device(for example our LFRX) ending with the target frequency
we are interesting in.
"""
usrp.tune(self.usrp_source, 0, self.selected_device, self.usrp_freq)
self.wxgui_fftsink2.set_baseband_freq(self.usrp_freq)
def get_usrp_freq(self):
return self.usrp_freq
def set_gain_usrp_source(self, gain_usrp_source):
self.gain_usrp_source = gain_usrp_source
self.selected_device.set_gain(self.gain_usrp_source)
if __name__ == '__main__':
parser = OptionParser()
parser.add_option("-e","--dev", dest="device", type="str", default='LFRX',
help="Replace <DEVICE> by 'LFRX' or 'BasicRX'.")
parser.add_option("-c","--decim", dest="usrp_decim", type="int", default='250',
help="Replace <USRP_DECIM> by the desired decimation Rate of the USRP(default is 250).")
parser.add_option("-f","--usrp-freq", dest="usrp_freq", type="float", default=1e6)
parser.add_option("-u","--usrp-freq-min", dest="usrp_freq_min", type="float", default=500.0e3)
parser.add_option("-o","--usrp-freq-max", dest="usrp_freq_max", type="float", default=10e6)
parser.add_option("-d", "--debug", action="store_true", default=False,
help="Start the debug modus.")
(options, args) = parser.parse_args()
tb = uebertragungschar_LF_RX(options)
tb.Run()
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