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Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Assembling an FM Receiver Like Blazes
by GNU Radio
Albert Chun-Chieh Huang
January 21, 2013
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
About the Author
He is both a programmer and a communication engineer.He learned Python in 2000 and has used it extensively onimproving his workflow ever since. He has been working incommunication IC industry for more than eight years. Hisinterests include communication engineering andengineering communication, which consists of fields fromphysical layer to MAC layer as well as typesetting.
Blog: Random Notes,http://alberthuang314.blogspot.com/
LinkedIn:http://www.linkedin.com/in/alberthuang314
Email address: alberthuang314 AT gmail DOT com
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Outline
1 GNU Radio Revisited
2 FM Receiver Architecture
3 GNU Radio Companion
4 Digital Signal Processing
5 Concluding Remarks
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
GNU Radio Revisited
In the previous talk, we introduced both software-definedradio and GNU Radio.
http://goo.gl/tQK0W
GNU Radio
is a free & open-source software development toolkit thatprovides signal processing blocks to implement softwareradios.primarily written in Python with performance-critical signalprocessing components written in C++ [1].C++ classes are wrapped by SWIG [2].
You can get NT$900 software-defined radio platform withRTL2832U-based DVB dongles.
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
FM Broadcasting
Pioneered by Edwin Howard Armstrong (1890–1954) in1936.
FM broadcasting has better quality than AM broadcasting.
AM still has its important role in aircraft communicationbecause audio quality in AM is linearly porportional toSNR, while FM is not.
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Frequency Modulation
http://en.wikipedia.org/wiki/File:Amfm3-en-de.gif
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Frequency Domain Concept
Time Domain
0 1 2 3 4-2
-1
0
1
2
1 second
Frequency Domain
0 1 2 3 40
1
2
3
4
Frequency
Magnitude
2 Hz
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Frequency Domain: Single-Sided v.s. Double-Sided
0 1 2 3 40
1
2
3
4
Frequency
Magnitude
2 Hz
-3 -2 -1 0 1 2 30
1
2
3
4
Frequency
Magnitude
2 Hz-2 Hz
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
FM Broadcasting Spectrum
0 1 2 3 4 5 6 7 8 9 100
1
2
3
4
5
0.03 15 23 38 53 Frequency (kHz)
MonoL+R
19 kHzstereopilot
Stereo L-R(DSB-SC)
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
What Is a Mixer?
I'm a building with an elevator
Entrance
Exit
I'm EM wave, a.k.a. passband signal.
BW
BW
Carrier FrequencyI'm
baseband signal now!
This building with an elevator
is mixer!
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Direct Conversion Receiver
-1 0 1 2 3 4 5 6 7 8 90
1
2
3
4
5
Mixer
Local Oscillator = Carrier Frequency, i.e. Fc
Input Signal(Passband) Baseband signal
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Superheterodyne Receiver
-1 0 1 2 3 4 5 6 7 8 90
1
2
3
4
5
Mixer
bInput Signal
PassbandDemodulatorIF
Intermediate Frequency
b
LO = Fc + IF
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Superheterodyne v.s. Direct Conversion
Direct conversion is a straighforward receiver architecture.
Superheterodyne receiver architecture was invented byEdwin Howard Armstrong (1890–1954) in 1918.
Superheterodyne
is more complexhas much better performance
In modern digital communication, direct conversion iswidely employed due to its simplicity.
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Elonics E4000 Receiver Architecture
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
GNU Radio Companion
Written in Python, GTK, LXML, and Cheetah
Useful to build a communication system in a visualizingway
Ready to execute after GNU Radio is installed
% gnuradio-companion
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Building FM Receiver by GNU Radio Companion
Required Components w.r.t. Signal Flow
RTLSDR SourceWBFM Receive PLLMultiply ConstantAudio Sink
Auxiliary Components
WX GUI Scope SinkWX GUI FFT Sink
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Glue Components Together
Clicking an output port followed by an input port willmake a connection
Building signal flow: RTLSDR Source → WBFM ReceivePLL → Multiply Constant → Audio Sink
Save, Generate, and Execute!
Download above GRC file from http://goo.gl/Uu1W1
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Seeing Is Believing!
How can we know where the problem is?
WX GUI Scope Sink can help you to observe time domainsignals.
WX GUI FFT Sink can help you to observe frequencyspectrum.
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
FM Receiver with Scope and Spectrum Analyzer
Add WX GUI Scope Sink before audio sink
Set sampling rate to 2x more than 48kHzAdjust X width
Add WX GUI FFT GUI Sink after RTLSDR sink
Set sampling rate to 2MHzSet FFT size to 512
Download above GRC file from http://goo.gl/ym1Og
Sounds noisy, huh?
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Filtering
Filtering is to cancel or reduce signals you don’t want, likenoise or other’s signal.
Cutoff frequency
Highest frequency of passband for a low pass filterLowest freqeuncy of passband for a high pass filter
Transition region
Region between cutoff frequency and stop band
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Frequency Response
200 300 400 500 600 700 800 900 1000Wavelength (nm)
-30
-20
-10
0
10
20
Transm
ittance
(dB)
Transmittance for Circular Polarizers
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Filtering in GNU Radio Companion
Add low pass filter after RTLSDR sink
Set Sampling rate to 2MHz to match RTLSDR sinkSet cutoff frequency to 120kHzSet transition region to 50kHz
Wider transition region has lower computing complexity
Leave others untouched
Download GRC file from http://goo.gl/JLnG1
Sounds a little better? Let’s see.
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Observing Signals Before/After Filters
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Concluding Remarks
GNU Radio Companion provides very easy and intuitiveway to create digital signal processing chain!
There are many already-existed components to let usexperiment communication systems by trial-and-error!
We don’t have to write one line of code to build an FMreceiver!
Don’t wait to have fun on communication systems byinstalling GNU Radio tonight!
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
Q & A
Assembling an
FM Receiver
Like Blazes
by GNU Radio
Albert
Chun-Chieh
Huang
GNU Radio
Revisited
FM Receiver
Architecture
GNU Radio
Companion
Digital Signal
Processing
Concluding
Remarks
References
References
GNU Radio Project Wiki, [Online]. Available:http://gnuradio.org/redmine/projects/gnuradio/wiki
SWIG - Simple Wrapper and Interface Generator,[Online]. Available: http://swig.org.