PySDR: Low-Pass Filtering Out an Interferer
Companion to the Filters chapter of PySDR
- Author Marc
- Category Filters
- Blocks 13
- Connections 8
- File
filter/filters_lowpass_interference.grc
Blocks used
| Block | Module | Used |
|---|---|---|
| Low Pass Filter | GNU Radio | 2 |
| Noise Source | GNU Radio | 2 |
| QT GUI Range | GNU Radio | 2 |
| Add | GNU Radio | 1 |
| GUI Layout | GNU Radio | 1 |
| Note | GNU Radio | 1 |
| QT GUI Frequency Sink | GNU Radio | 1 |
| Signal Source | GNU Radio | 1 |
| Throttle | GNU Radio | 1 |
| Variable | GNU Radio | 1 |
Notes in this flowgraph
- Signal of interest: band-limited noise at 0 Hz Interferer at +10 kHz, plus a noise floor Drag cutoff below 10 kHz: the interferer drops below the old noise floor. Narrowing the transition width sharpens the edge, at the cost of more filter taps
Flowgraph source
filter/filters_lowpass_interference.grc
options:
parameters:
author: Marc
comment: ''
copyright: ''
description: Companion to the Filters chapter of PySDR
generate_options: qt_gui
id: PySDR__Low_Pass_Filtering_Out_an_Interferer
title: 'PySDR: Low-Pass Filtering Out an Interferer'
states:
coordinate: [10, 10]
rotation: 0
state: enabled
blocks:
- name: cutoff
id: variable_qtgui_range
parameters:
comment: ''
label: Low-pass cutoff (Hz)
min_len: '200'
orient: QtCore.Qt.Horizontal
rangeType: float
start: '500'
step: '100'
stop: '20000'
value: '3000'
widget: counter_slider
states:
coordinate: [760, 50]
rotation: 0
state: enabled
- name: samp_rate
id: variable
parameters:
comment: ''
value: '50000'
states:
coordinate: [100, 150]
rotation: 0
state: enabled
- name: transition
id: variable_qtgui_range
parameters:
comment: ''
label: Transition width (Hz)
min_len: '200'
orient: QtCore.Qt.Horizontal
rangeType: float
start: '200'
step: '100'
stop: '10000'
value: '1000'
widget: counter_slider
states:
coordinate: [1040, 50]
rotation: 0
state: enabled
- name: add
id: blocks_add_xx
parameters:
affinity: ''
alias: ''
comment: ''
maxoutbuf: '0'
minoutbuf: '0'
num_inputs: '3'
type: complex
vlen: '1'
states:
coordinate: [580, 320]
rotation: 0
state: enabled
- name: freq_sink
id: qtgui_freq_sink_x
parameters:
affinity: ''
alias: ''
alpha1: '1'
alpha10: '1'
alpha2: '1'
alpha3: '1'
alpha4: '1'
alpha5: '1'
alpha6: '1'
alpha7: '1'
alpha8: '1'
alpha9: '1'
autoscale: 'False'
average: '1.0'
axislabels: 'True'
color1: '"blue"'
color10: '"dark blue"'
color2: '"red"'
color3: '"green"'
color4: '"black"'
color5: '"cyan"'
color6: '"magenta"'
color7: '"yellow"'
color8: '"dark red"'
color9: '"dark green"'
comment: ''
ctrlpanel: 'False'
fc: '0'
fftsize: '1024'
freqhalf: 'True'
grid: 'True'
label1: Before
label10: ''
label2: After
label3: ''
label4: ''
label5: ''
label6: ''
label7: ''
label8: ''
label9: ''
legend: 'True'
marker1: '-1'
marker10: '-1'
marker2: '-1'
marker3: '-1'
marker4: '-1'
marker5: '-1'
marker6: '-1'
marker7: '-1'
marker8: '-1'
marker9: '-1'
maxoutbuf: '0'
minoutbuf: '0'
name: Before vs after filtering
nconnections: '2'
samp_rate: samp_rate
style1: '1'
style10: '1'
style2: '1'
style3: '1'
style4: '1'
style5: '1'
style6: '1'
style7: '1'
style8: '1'
style9: '1'
tr_chan: '0'
tr_level: '0'
tr_mode: qtgui.TRIG_MODE_FREE
tr_tag: ''
type: complex
update_time: '0.1'
width1: '1'
width10: '1'
width2: '1'
width3: '1'
width4: '1'
width5: '1'
width6: '1'
width7: '1'
width8: '1'
width9: '1'
ymax: '10'
ymin: '-100'
states:
coordinate: [1440, 320]
rotation: 0
state: enabled
- name: interferer
id: analog_sig_source_x
parameters:
affinity: ''
alias: ''
amplitude: '0.3'
comment: ''
frequency: '10000'
maxoutbuf: '0'
minoutbuf: '0'
samp_rate: samp_rate
type: complex
waveform: analog.GR_COS_WAVE
states:
coordinate: [260, 480]
rotation: 0
state: enabled
- name: noise_floor
id: analog_noise_source_x
parameters:
affinity: ''
alias: ''
amplitude: '0.02'
comment: ''
maxoutbuf: '0'
minoutbuf: '0'
seed: '1'
type: complex
states:
coordinate: [320, 620]
rotation: 0
state: enabled
- name: note_sig
id: note
parameters:
affinity: ''
alias: ''
comment: ''
note: "Signal of interest: band-limited noise at 0 Hz\n\nInterferer at +10 kHz, plus a noise floor\n\nDrag cutoff below 10 kHz: the interferer drops below the old noise floor. Narrowing the transition width sharpens the edge, at the cost of more filter taps"
states:
coordinate: [330, 40]
rotation: 0
state: enabled
- name: soi_noise
id: analog_noise_source_x
parameters:
affinity: ''
alias: ''
amplitude: '0.7'
comment: ''
maxoutbuf: '0'
minoutbuf: '0'
seed: '0'
type: complex
states:
coordinate: [10, 320]
rotation: 0
state: enabled
- name: soi_shape
id: low_pass_filter
parameters:
affinity: ''
alias: ''
beta: '6.76'
comment: ''
cutoff_freq: '2500'
decim: '1'
gain: '3'
interp: '1'
maxoutbuf: '0'
minoutbuf: '0'
samp_rate: samp_rate
type: fir_filter_ccf
width: '500'
win: window.WIN_HAMMING
states:
coordinate: [260, 260]
rotation: 0
state: enabled
- name: throttle
id: blocks_throttle2
parameters:
affinity: ''
alias: ''
comment: ''
ignoretag: 'True'
limit: auto
maximum: '0.1'
maxoutbuf: '0'
minoutbuf: '0'
samples_per_second: samp_rate
type: complex
vlen: '1'
states:
coordinate: [830, 330]
rotation: 0
state: enabled
- name: user_lpf
id: low_pass_filter
parameters:
affinity: ''
alias: ''
beta: '6.76'
comment: ''
cutoff_freq: cutoff
decim: '1'
gain: '1'
interp: '1'
maxoutbuf: '0'
minoutbuf: '0'
samp_rate: samp_rate
type: fir_filter_ccf
width: transition
win: window.WIN_HAMMING
states:
coordinate: [1150, 450]
rotation: 0
state: enabled
- name: wasm_gui_layout_0
id: wasm_gui_layout
parameters:
affinity: ''
alias: ''
columns: '12'
comment: ''
layout: '{"cutoff":[0,0,5,1],"freq_sink":[0,1,12,4],"transition":[7,0,5,1]}'
row_height: '60'
states:
coordinate: [1310, 70]
rotation: 0
state: enabled
connections:
- [add, '0', throttle, '0']
- [interferer, '0', add, '1']
- [noise_floor, '0', add, '2']
- [soi_noise, '0', soi_shape, '0']
- [soi_shape, '0', add, '0']
- [throttle, '0', freq_sink, '0']
- [throttle, '0', user_lpf, '0']
- [user_lpf, '0', freq_sink, '1']
metadata:
file_format: 1
grc_version: 3.11.0.0