(1)Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt &
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(2) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions VLF reception AM v.s PM Sound card SDR DVB-T: sampling resolution ? Conclusion References. Why ? Only when certain events recur in accordance with rules or regularities, as is the case with repeatable experiments, can our observations be tested – in principle – by anyone. We do not take even our own observations quite seriously, or accept them as scientific observations, until we have repeated and tested them. Only by such repetitions can we convince ourselves that we are not dealing with a mere isolated “coincidence”, but with events which, on account of their regularity and reproducibility, are in principle inter-subjectively testable.. K. Popper, The Logic of Scientific Discovery, (1935) p.23. 2 / 32.
(3) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions VLF reception AM v.s PM Sound card SDR DVB-T: sampling resolution ?. Why ? Only when certain events recur in accordance with rules or regularities, as is the case with repeatable experiments, can our observations be tested – in principle – by anyone. We do not take even our own observations quite seriously, or accept them as scientific observations, until we have repeated and tested them. Only by such repetitions can we convince ourselves that we are not dealing with a mere isolated “coincidence”, but with events which, on account of their regularity and reproducibility, are in principle inter-subjectively testable.. Conclusion References. K. Popper, The Logic of Scientific Discovery, (1935) p.23. An open-source GNSS software receiver allows to have full access to the signal processing and to make add-ons to the source code in order to obtain the desired GNSS reflectometry processing. L. Lestarquit & al., Reflectometry With an Open-Source Software GNSS Receiver: Use Case With Carrier Phase Altimetry, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (2016). 3 / 32.
(4) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. DCF-77 modulation schemes Radiofrequency wave s(t) = A(t) · cos(ω · t + ϕ(t)) ⇒ carrier frequency (Cs, from PTB), amplitude (1 s), phase modulation. J.-M Friedt & al.. Modulation and Coding Pseudo random noise phase shift keying of the carrier. Introductions VLF reception AM v.s PM Sound card SDR DVB-T: sampling resolution ? Conclusion References. Carrier, amplitude modulation and PRN are phase synchronous. Phase deviation ± 14.3° Chiprate 645.83 cps corresponding to 1.55 ms per chip. EFTS 2016 TT-2 A. Bauch. 41. Can we use this information to measure the delay between air (bouncing off the ionosphere) and surface waves ? 0 A.. Bauch, Time Dissemination II, EFTS2016. 4 / 32.
(5) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. Ionosphere altitude. J.-M Friedt & al. Introductions VLF reception AM v.s PM Sound card SDR DVB-T: sampling resolution ? Conclusion References. J.S. Belrose, The oblique reflecion of CW low-frequency radio waves from the ionosphere, in W.T. Blackband, Propagation of Radio Waves at Frequencies below 300 kc/s (1964), chapter 11. 0 Sudden Ionospheric Disturbances (SID) monitoring station at http://sidstation.loudet.org/data-en.xhtml 5 / 32.
(6) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions VLF reception AM v.s PM Sound card SDR DVB-T: sampling resolution ?. DCF-77 • 50 kW emitter in. Mainflingen, Germany, 370 km from Besançon • Carrier referenced to Cs. primary standard (PTB) • used to synchronize. radiofrequency-disciplined clocks. Conclusion. • 77.5 kHz: surface wave and. References. air wave bouncing off the ionosphere. 0 A. Bauch, P. Hetzel & D. Piester, Time and Frequency Dissemination with DCF77: From 1959 to 2009 and beyond, PTB Mitteilungen 119 (3), 2009 6 / 32.
(7) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. DCF-77 • 50 kW emitter in. GPS. Mainflingen, Germany, 370 km from Besançon. 1575.42 MHz km. J.-M Friedt & al.. • Carrier referenced to Cs. 20000. Introductions VLF reception. primary standard (PTB). ionosphere F−layer (300 km). AM v.s PM. • used to synchronize. Sound card SDR. ionosphere D−layer (50−90 km). DVB-T: sampling resolution ?. 1 41. Conclusion. ground/air ∆τ∼100 µs. Me. 370 km. 3k. m. km. 38. References. day/night ∆τ=95 µ s 77.5 kHz. DCF−77. radiofrequency-disciplined clocks. • 77.5 kHz: surface wave and. air wave bouncing off the ionosphere. 1: catm = c0 /1.000338 2: cgnd < cair : 0.5 µs @ 370 km 0 C. Hargreaves, ASF Measurement and Processing Techniques, to allow Harbour Navigation at High Accuracy with eLoran, MSc Univ. of Nottingham (2010) 7 / 32.
(8) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al.. Short antenna impedance and quality factor Coil + parallel capacitance for tuning antiresonance at operating frequency: V = 2π A·N·Eλ·cos(ϑ) × Q. Introductions VLF reception. 10/24/2016 3:16:58 PM 1311.6004K12-101582-pP. Trc3. AM v.s PM. Z11 Lin Mag 5 kΩ/ Ref 10 kΩ Cal. 1. 35000 30000. M4 M1. 25000. Sound card SDR. 20000 15000. DVB-T: sampling resolution ?. M3. M2. 10000 10 kΩ 5000 0. Bandpass Ref to Max Track Bandwidth 1.902000kHz Center 77.836191kHz Lower Edge 76.891000kHz Upper Edge 78.793000kHz Quality Factor (3dB) -----Quality Factor (BW) -----Loss -21751.4718dB M1 77.873000kHz 21.234kΩ M2 76.891000kHz 10.669kΩ M3 78.793000kHz 10.860kΩ M4 77.836000kHz 21.455kΩ. -5000. Conclusion. -10000 -15000. References. Ch2 Center 77.5 kHz Trc4. Pwr 0 dBm Bw 1 kHz. Span 20 kHz. Z11 Phase 20°/ Ref 0°Cal. 2. 100. M2 87.487000kHz -87.86° M3 78.784000kHz -60.82° M4 77.823000kHz -0.30 °. 80 60 40 20. 0°0. M4. -20 -40. M3. -60. M2. -80 -100. Ch2 Center 77.5 kHz. Pwr 0 dBm Bw 1 kHz. Span 20 kHz. Z11 indoor ⇒ need to locate the antenna outdoor to get rid of lab-generated noise ⇒ need to introduce impedance converting circuit (antiresonance = maximize voltage with no current flow) + prevent Q degradation 8 / 32 (http://www.qsl.net/dl4yhf/dcf77_osc/index.html).
(9) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al.. Short antenna impedance and quality factor Coil + parallel capacitance for tuning antiresonance at operating frequency: V = 2π A·N·Eλ·cos(ϑ) × Q. Introductions VLF reception AM v.s PM Sound card SDR DVB-T: sampling resolution ? Conclusion References. outdoor indoor ⇒ need to locate the antenna outdoor to get rid of lab-generated noise ⇒ need to introduce impedance converting circuit (antiresonance = maximize voltage with no current flow) + prevent Q degradation 9 / 32.
(10) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. Lock-in + oscilloscope signal reception Experiment1: phase of the carrier and amplitude modulation detection. J.-M Friedt & al. Introductions VLF reception. Cs 10 MHz SMC100. 77500. AM v.s PM Sound card SDR DVB-T: sampling resolution ?. computer. ethernet. lock in amplifier ref in phase mag CH1. CH2. digital oscilloscope. Conclusion References. Internal synthesizer quartz reference. • AM: 100 or 200 ms. long amplitude drop at the beginning of each second • ϕ: ∆ω · t + ϕ(t). 10 / 32.
(11) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. Lock-in + oscilloscope signal reception Experiment1: phase of the carrier and amplitude modulation detection. J.-M Friedt & al. Introductions VLF reception. Cs 10 MHz SMC100. 77500. AM v.s PM Sound card SDR DVB-T: sampling resolution ?. computer. ethernet. lock in amplifier ref in phase mag CH1. CH2. digital oscilloscope. Conclusion References. Synthesizer locked on Cs reference. • AM: 100 or 200 ms. long amplitude drop at the beginning of each second • ϕ: ∆ω · t + ϕ(t). 11 / 32.
(12) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. Lock-in + oscilloscope signal reception Experiment1: phase of the carrier and amplitude modulation detection. J.-M Friedt & al. Introductions VLF reception. Cs 10 MHz SMC100. 77500. AM v.s PM Sound card SDR DVB-T: sampling resolution ?. computer. ethernet. lock in amplifier ref in phase mag CH1. CH2. digital oscilloscope. Conclusion References. Amplitude+phase+raw data @ >200 kS/s. • AM: 100 or 200 ms. long amplitude drop at the beginning of each second • ϕ: ∆ω · t + ϕ(t). 12 / 32.
(13) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. Phase-modulated spectrum spreading • Phase demodulation cross-correlation peak: 120 periods at. J.-M Friedt & al. Introductions VLF reception AM v.s PM Sound card SDR DVB-T: sampling resolution ?. 77.5 kHz=1.55 ms/bit • 700 Hz bandwidth needed for phase modulation processing • 511 bit long PRN 1 : x 9 + x 5 + 1. in lfsr.dat 0000010001100001001110010101011000011011110100110111001000101000010101101001111110110010010010110111111001001 1010100110011000000011000110010100011010010111111101000101100011101011001011001111000111110111010000011010110 1101110110000010110101111101010101000000101001010111100101110111000000111001110100100111101011101010001001000 0110011100001011110110110011010000111011110000111111111000001111011111000101110011001000001001010011101101000 1111001111100110110001010100100011100011011010101110001001100010001000000001. • interpolate the PRN sequence to match sampling rate, and cross-correlate. Conclusion 4e+06. + parabolic fit of |xcorr ()| max. 3e+06 xcorr (a.u.). load l f s r . dat np =192000/59∗(120/77500) ; % f s ∗( Tprn /fDCF ) o l d P =0; f o r k =1: l e n g t h ( l f s r ) P=r o u n d ( k∗np ) ; i f ( l f s r ( k ) ==1) i l f s r ( o l d P +1:P)=o n e s (P−oldP , 1 ) ; e l s e i l f s r ( o l d P +1:P)=z e r o s (P−oldP , 1 ) ; endif o l d P=P ; end y c=x c o r r ( xp−mean ( xp ) , i l f s r −mean ( i l f s r ) ) ;. 2e+06. 1e+06. 0 0. 2. 4 time (s). 6. 8. 4e+06. 3e+06 xcorr (a.u.). References. 2e+06. 1e+06. 0 3.97. 3.98. 3.99 time (s). 4. 1 https://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_. 4/4.4_zeit_und_frequenz/pdf/5_1988_Hetzel_-_Proc_EFTF_88.pdf. 13 / 32.
(14) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions. Resolution gain by using phase rather than amplitude Oscilloscope: sampling rate=5 kHz, duration=50 s (250 ksamples=1.8 MB/chan/min) record phase+amplitude ⇒ cross-correlate PRN and phase 50-s acquisition. Zoom. 10000. 10000. 5000. 5000. 6000. VLF reception 0 -5000 -10000 30 40 time (s). 50. 60. -8000 0. abs(xcorr(ph,prn)). abs(xcorr(ph,prn)). 0. -6000. 0.5. 1 1.5 time (s). 2. 2.5. 1.85. 1.9. 1.95 time (s). 2. 2.05. 1.85. 1.9. 1.95 time (s). 2. 2.05. 800000. 800000 600000 400000 200000. 600000 400000 200000. 0. 600000. 400000. 200000. 0 0. 10. 20. 30 40 time (s). 50. 60. 0. 0.5. 1 1.5 time (s). 2. 2.5. Carrier phase. AM v.s PM cross-correlation 6000. 6000. 4000 <A>_{20}. 4000 <phase>. 2000 0. 2000 0 -2000 -4000. -2000. -6000 -8000. -4000 20. 40. 60. 80 time (h). 100. 120. 140. 200. 400. 600 800 sample number (5 kS/s). 1000. 1200. 1400. 200. 400. 600 800 sample number (5 kS/s). 1000. 1200. 1400. 10000 xcorr(phase,PRN). References. 20. 1e+06. <amplitude>. Conclusion. 10. 2000. -2000 -4000. -10000 0. DVB-T: sampling resolution ?. 0 -5000. abs(xcorr(ph,prn)). Sound card SDR. amplitude. amplitude. amplitude. AM v.s PM. 4000. 5000. 0. 600000. 400000. 200000. -5000 20. 40. 60. 80 time (h). 100. 120. 140. 14 / 32.
(15) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions VLF reception. Full SDR solution using gnuradio. 2. • Frequency translation and low-pass filter (lockin): Xlating FIR Filter • Once baseband is reached, decimate (low pass filter to prevent. aliasing and 1 in N) – here N=59 • (192000/59)/(77500/120) ' 5.0388 : 5 samples/bit • Sound card sampling frequency fluctuation ⇒ record GPS 1 PPS. AM v.s PM. f=192 kHz+df. Sound card SDR. sound card. DVB-T: sampling resolution ?. GPS 1 PPS. channel1 channel2. Conclusion. Cs 10 MHz SMC100. References. computer. 77500. lock in amplifier ref in phase mag CH1. ethernet. CH2. digital oscilloscope. • Sound card offset to nominal frequency: 1.15 Hz @. 77.5 kHz=15 ppm • Lack of continuity of the GNURadio oscilloscope output when. adding second (GPS) path ? 2 dsPIC-based. based DCF receiver: http://www.marvellconsultants.com/DCF 15 / 32.
(16) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. Full SDR solution using gnuradio • Frequency translation and low-pass filter (lockin): Xlating FIR Filter • Once baseband is reached, decimate (low pass filter to prevent. Introductions VLF reception AM v.s PM. aliasing and 1 in N) – here N=59 • (192000/59)/(77500/120) ' 5.0388 : 5 samples/bit • Sound card sampling frequency fluctuation ⇒ record GPS 1 PPS. Sound card SDR. exp(−j*f*t). exp(j*f*t). Pexp(−j*f*t). exp(j*f*t). Baseband. Conclusion References. 155−96=59 kHz. DVB-T: sampling resolution ?. 77,5+77,5=155 kHz. J.-M Friedt & al.. −fe/2 +fe/2 −96 −77.5 77.5 96 155 f (kHz) real signal => even spectrum. • Sound card offset to nominal frequency: 1.15 Hz @. 77.5 kHz=15 ppm • Lack of continuity of the GNURadio oscilloscope output when. adding second (GPS) path ? 16 / 32.
(17) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions VLF reception. Full SDR solution using gnuradio • Frequency translation and low-pass filter (lockin): Xlating FIR Filter • Once baseband is reached, decimate (low pass filter to prevent. aliasing and 1 in N) – here N=59 • (192000/59)/(77500/120) ' 5.0388 : 5 samples/bit • Sound card sampling frequency fluctuation ⇒ record GPS 1 PPS. AM v.s PM Sound card SDR DVB-T: sampling resolution ? Conclusion References. • Sound card offset to nominal frequency: 1.15 Hz @. 77.5 kHz=15 ppm • Lack of continuity of the GNURadio oscilloscope output when. adding second (GPS) path ? 17 / 32.
(18) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions VLF reception. Full SDR solution using gnuradio • Frequency translation and low-pass filter (lockin): Xlating FIR Filter • Once baseband is reached, decimate (low pass filter to prevent. aliasing and 1 in N) – here N=59 • (192000/59)/(77500/120) ' 5.0388 : 5 samples/bit • Sound card sampling frequency fluctuation ⇒ record GPS 1 PPS. AM v.s PM Sound card SDR DVB-T: sampling resolution ? Conclusion References. • Sound card offset to nominal frequency: 1.15 Hz @. 77.5 kHz=15 ppm • Lack of continuity of the GNURadio oscilloscope output when. adding second (GPS) path ? 18 / 32.
(19) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions VLF reception. Full SDR solution using gnuradio • Frequency translation and low-pass filter (lockin): Xlating FIR Filter • Once baseband is reached, decimate (low pass filter to prevent. aliasing and 1 in N) – here N=59 • (192000/59)/(77500/120) ' 5.0388 : 5 samples/bit • Sound card sampling frequency fluctuation ⇒ record GPS 1 PPS. AM v.s PM Sound card SDR DVB-T: sampling resolution ? Conclusion References. • Sound card offset to nominal frequency: 1.15 Hz @. 77.5 kHz=15 ppm • Lack of continuity of the GNURadio oscilloscope output when. adding second (GPS) path ? 19 / 32.
(20) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions VLF reception. Full SDR solution using gnuradio • Frequency translation and low-pass filter (lockin): Xlating FIR Filter • Once baseband is reached, decimate (low pass filter to prevent. aliasing and 1 in N) – here N=59 • (192000/59)/(77500/120) ' 5.0388 : 5 samples/bit • Sound card sampling frequency fluctuation ⇒ record GPS 1 PPS. AM v.s PM Sound card SDR DVB-T: sampling resolution ? Conclusion References. • Sound card offset to nominal frequency: 1.15 Hz @. 77.5 kHz=15 ppm • Lack of continuity of the GNURadio oscilloscope output when. adding second (GPS) path ? 20 / 32.
(21) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. Full SDR solution using gnuradio • Frequency translation and low-pass filter (lockin): Xlating FIR Filter • Once baseband is reached, decimate (low pass filter to prevent. J.-M Friedt & al. Introductions VLF reception AM v.s PM. aliasing and 1 in N) – here N=59 • (192000/59)/(77500/120) ' 5.0388 : 5 samples/bit • Sound card sampling frequency fluctuation ⇒ record GPS 1 PPS. Sound card SDR DVB-T: sampling resolution ? Conclusion References. • Sound card offset to nominal frequency: 1.15 Hz @. 77.5 kHz=15 ppm • Lack of continuity of the GNURadio oscilloscope output when adding second (GPS) path ? 21 / 32.
(22) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. Full SDR solution using gnuradio • Frequency translation and low-pass filter (lockin): Xlating FIR Filter • Once baseband is reached, decimate (low pass filter to prevent. J.-M Friedt & al. Introductions VLF reception AM v.s PM. aliasing and 1 in N) – here N=59 • (192000/59)/(77500/120) ' 5.0388 : 5 samples/bit • Sound card sampling frequency fluctuation ⇒ record GPS 1 PPS. Sound card SDR DVB-T: sampling resolution ? Conclusion References. • Sound card offset to nominal frequency: 1.15 Hz @. 77.5 kHz=15 ppm • Lack of continuity of the GNURadio oscilloscope output when adding second (GPS) path ? 22 / 32.
(23) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al.. Sound card SDR GNURadio is a python script generator, no need for a graphical interface 1 run periodically acquisition script 2 process resulting dataset using GNU Octave. Introductions VLF reception AM v.s PM Sound card SDR DVB-T: sampling resolution ? Conclusion References. Implementation using Octave of FIR+xcorr: xcorr (a, b) 6= xcorr (b, a) 0.001 0.0005 0 0. 5. 10. 15. 20. 25. 15. 20. 25. 15. 20. 25. time (s). phase (rad). 4 2. x=r e a d c o m p l e x b i n a r y ( f i l e n a m e ) ; d c f=r e a l ( x ) ; g p s=imag ( x ) ; f e =192 e3 ; t i m e = [ 0 : l e n g t h ( x ) −1] ’/ f e ; d c f=d c f .∗ e x p ( j ∗2∗ p i ∗(77500)∗t i m e ) ; l p f = f i r l s ( 2 5 0 , [ 0 720 790 f e /2]∗2/ f e , [ 1 1 0 0 ] ) ; d c f= f i l t e r ( l p f , 1 , d c f ) ; x=d c f ( 1 : 5 9 : end ) ; f e =192000/59;. 0 -2 -4 0. 5. 10 time (s). xcorr(phase,code). amplitude (a.u.). 0.002 0.0015. 400 300 200 100 0 0. 5. 10 time (s). [ y f , x f ]=max ( a b s ( f f t ( x−mean ( x ) ) ) ) ; x f=x f−l e n g t h ( x ) −1; d f=−x f / l e n g t h ( x )∗ f e ; l o=e x p ( j ∗2∗ p i ∗d f∗t i m e ) ; x=x .∗ l o ; xp0=mean ( a n g l e ( x ( 1 : 3 0 0 0 ) ) ) ; x=x.∗(− j ∗xp0 ) ; xp=a n g l e ( x ) ; y c=x c o r r ( xp−mean ( xp ) , i l f s r −mean ( i l f s r ) ) ; y c=y c ( f l o o r ( l e n g t h ( y c ) / 2 ) : end ) ; g g p s=g p s ( 1 : 5 9 : end ) ; 23 / 32.
(24) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al.. Sound card SDR GNURadio is a python script generator, no need for a graphical interface 1 run periodically acquisition script 2 process resulting dataset using GNU Octave. Introductions VLF reception AM v.s PM Sound card SDR DVB-T: sampling resolution ? Conclusion References. 1 minute acquisition (60 seconds), red=xcorr max. to 1 PPS interval, blue=parabolic fit max. to 1 PPS Getting rid of outliers: use median value + average of samples lying at median±5 a.u. 24 / 32.
(25) J.-M Friedt & al. Introductions VLF reception. Cs v.s sound card+GPS 3-day measurement xcorr-1PPS position. Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. 663 662.5 662 661.5 661. AM v.s PM. 20. 40. 60 time (h). 80. 100. 20. 40. 60 time (h). 80. 100. 20. 40. 60 time (h). 80. 100. Sound card SDR. Conclusion. <phase>. 30000 DVB-T: sampling resolution ?. 20000 10000 0 -10000. References. -20000. <amplitude>. 30000 20000 10000 0 -10000 -20000. σxcorr −1PPS (200samples) = 0.03 sample periods around time 60 h 192 kHz/59=3254 Hz=1/307 µs ⇒ σxcorr −1PPS = 9.2 µs∼2.8 km. 25 / 32.
(26) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. DVB-T v.s sound card • Sampling frequency > 150 kHz (we only need up to 200 kS/s) 2 : is 8 bit sufficient to detect air v.s ground wave ? SNR = 6.02 · B + 1.76 + 10 log10 (fs /(2 · fmax )) with B16→8 & fs × = 10. • Sampling resolution J.-M Friedt & al. Introductions VLF reception. P. AM v.s PM. antenna transfer function. Sound card SDR DVB-T: sampling resolution ? Conclusion References. f jammer. airgnd fs/2. Problems: • the zero-IF E4000 based DVB-T receivers are obsolete • the newer R820T(2) based receivers use non-zero (3.57 MHz) IF ⇒ bypass RF frontend (capacitive decoupling of I-/Q-) ⇒ make the RTL2832U believe it is operating at zero-IF 2 J.. 3. Mitola, Software Defined Radio Architecture, John Wiley & Sons (2000), p.293. 3 http://superkuh.com/rtlsdr.html 26 / 32.
(27) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. DVB-T 1 2. J.-M Friedt & al.. hardware modification: I+=DCF77, Q+=GPS 1 PPS software modification: librtlsdr4 : src/librtlsdr.c, l.1580 [...] found : f p r i n t f ( s t d e r r , " dev tuner ,% x - > % x \ n " , dev−>t u n e r t y p e , → ,→RTLSDR TUNER E4000 ) ; dev−>t u n e r t y p e=RTLSDR TUNER E4000 ;. Introductions VLF reception. /∗ u s e t h e r t l c l o c k v a l u e by d e f a u l t ∗/ dev−>t u n x t a l = dev−>r t l x t a l ;. AM v.s PM Sound card SDR DVB-T: sampling resolution ?. 3. Conclusion. replace gr-osmosdr source (complex=8 bytes/sample) with rtl sdr 1.92 MS/s during 1 minute=230 MB as char but 920 MB as float #! / b i n / s h w h i l e t r u e ; do r t l s d r −s 1920000 −n 115200000 /tmp/ d v b t . b i n nom=‘ d a t e +%s ‘ o c t a v e go .m > $nom . d a t mv 1 . e p s ${nom} 1 . e p s ; mv 2 . e p s ${nom} 2 . e p s ; mv 3 . e p s ${nom} 3 . e p s s l e e p 10 done. References. 4. low-pass & decimate to reach 192 kHz, mix and low-pass+decimate: f s =1.92 e6 ; b= f i r l s ( 1 2 8 , [ 0 2 e5 2 . 5 e5 f s /2]∗2/ f s , [ 1 1 0 0 ] ) ; % 1 . 9 2 MHz/128=15 kHz r e s . d d c f= f i l t e r ( b , 1 , d d c f ) ; d d c f=d d c f ( 1 : 1 0 : end ) ; f s=f s / 1 0 ; % LPF/ dec i m =192 kHz t i m e = [ 0 : l e n g t h ( d d c f ) −1] ’/ f s ; d d c f=d d c f .∗ e x p ( i ∗t i m e∗2∗ p i ∗77493) ; % frequency transposition b= f i r l s ( 1 2 8 , [ 0 750 800 f s /2]∗2/ f s , [ 1 1 0 0 ] ) ; % LPF/ d eci m d d c f= f i l t e r ( b , 1 , d d c f ) ; d d c f=d d c f ( 1 : 5 9 : end ) ; f s=f s / 5 9 ;% LPF/ d eci m =3.254 kHz t i m e = [ 0 : l e n g t h ( d d c f ) −1] ’/ f s ;. 4 https://github.com/steve-m/librtlsdr 27 / 32.
(28) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions. DVB-T Again, magnitude (AM) and phase (PM) demodulation functional, but now 1 PPS GPS signal identified with 520 ns resolution (10-fold improvement) 4 20 Hz LPF. Conclusion References. 10. 20. 30 time (s). 40. 50. 60. 2 1 0 -1 -2 -3. 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0. -4. 50 Hz LPF. 0. 10. 20. 30. 40. 50. 60. time (s). 500 0. amplitude (a.u.). DVB-T: sampling resolution ?. amplitude (a.u.). 0. 3 phase (rad). Sound card SDR. 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0. 10. 20. 30 time (s). 40. 50. 60. 20 GPS 1 PPS. 10 0 -10. xcorr(phase,code). AM v.s PM. amplitude (a.u.). blue=phase, red=linear fit, green=phase-lin. fit. VLF reception. 400 300 200 100. -20 -30. 0 0. 10. 20. 30 time (s). 40. 50. AM (20 Hz LPF), AM (50 LPF), GPS. 60. 0. 10. 20. 30. 40. 50. 60. 70. time (s). unwrapped phase, xcorr. Lower SNR ⇒ poorer cross-correlation peak location in time 28 / 32.
(29) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals J.-M Friedt & al. Introductions. DVB-T Again, magnitude (AM) and phase (PM) demodulation functional, but now 1 PPS GPS signal identified with 520 ns resolution (10-fold improvement). Sound card SDR. 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0. 0.8 20 Hz LPF 0.6 0.4 0.2. Conclusion References. 10. 20. 30 time (s). 40. 50. 60 0. 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0. -0.2. 50 Hz LPF. 0. 10. 20. 30. 40. 50. 60. 0. 10. 20. 30 time (s). 40. 50. 60. -0.2 0. amplitude (a.u.). DVB-T: sampling resolution ?. amplitude (a.u.). 0. 10. 20. 30 time (s). 40. 50. 60. 20 GPS 1 PPS. 10. -0.4 tDCF-tGPS (s). AM v.s PM. amplitude (a.u.). 0. VLF reception. 0 -10. -0.6 -0.8 -1 -1.2. -20 -30. -1.4 0. 10. 20. 30 time (s). 40. 50. AM (20 Hz LPF), AM (50 LPF), GPS. 60. GPS to DCF77 phase. Lower SNR ⇒ poorer cross-correlation peak location in time 29 / 32.
(30) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. Conclusion and perspectives • Ability to receive DCF-77 using active antenna • Ability to decode DCF-77 using a lock-in amplifier and decode. phase modulation. J.-M Friedt & al. Introductions VLF reception AM v.s PM. • Ability to decode DCF-77 using SDR with signal acquired from c !) sound card & DVB-T receiver (how come that ∆z 2·B • Consistent results between Cs+lockin or sound card+GPS 10-6. Sound card SDR. 400 delay (us). DCF77 v.s GPS. DVB-T: sampling resolution ?. 200. 10-7 0 -200. Conclusion. avar (s). -400 16-Dec 09h. References. date (day month hour). X-ray flux (GOES). 5e-07. 10-8 tuning fork. 10-9. 4e-07 3e-07. 10-10. 2e-07 1e-07 0 06-Nov 00h. 26-Nov 00h. 16-Dec 00h. 05-Jan 00h. 10-11 0 10. 101. 102. 103 104 time (s). 105. 106. 107. • Question: if ground wave is strongest, why does its phase vary with. day/night ? (waveguide model) • Question: separate ground and air wave (improve xcorr resolution) ? • Microcontroller based sampling for high resolution 1 PPS timing 30 / 32.
(31) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. Conclusion and perspectives • Ability to receive DCF-77 using active antenna • Ability to decode DCF-77 using a lock-in amplifier and decode. phase modulation. J.-M Friedt & al. Introductions VLF reception AM v.s PM. • Ability to decode DCF-77 using SDR with signal acquired from c !) sound card & DVB-T receiver (how come that ∆z 2·B • Consistent results between Cs+lockin or sound card+GPS. Sound card SDR. CA code double CA CA code+1 CA code+2 CA code+3 CA code+4 CA code+5. 400 delay (us). DVB-T: sampling resolution ?. 200. 1.2. 0. 1 cross-correlation (a.u). -200. Conclusion. -400 16-Dec 09h. References. date (day month hour). X-ray flux (GOES). 5e-07 4e-07. 0.8 0.6 0.4. 3e-07. 0.2. 2e-07 1e-07. 0 0 06-Nov 00h. 26-Nov 00h. 16-Dec 00h. 05-Jan 00h. -30. -20. -10 0 10 time offset (sample number). 20. 30. • Question: if ground wave is strongest, why does its phase vary with. day/night ? (waveguide model) • Question: separate ground and air wave (improve xcorr resolution) ? • Microcontroller based sampling for high resolution 1 PPS timing 31 / 32.
(32) Monitoring the ionosphere altitude variation with a sound card: software defined radio processing of DCF-77 signals. 1 P.-H. Kamp, A Cheap SDR Loran-C frequency receiver at. phk.freebsd.dk/AducLoran/AducLoran-0.3.pdf 2 ARRL Antenna Handbook, Chapter5 (Small Loop Antennas), 18th Ed. (1997) 3 S.M.F. Raupach & G. Grosche, Chirped Frequency Transfer: A Tool for. J.-M Friedt & al.. 4 Introductions. 5. VLF reception AM v.s PM. 6. Sound card SDR DVB-T: sampling resolution ?. 7. Conclusion References. 8 9 10 11. 12. Synchronization and Time Transfer, IEEE Trans. Ultrasonics, Ferroelectrics, and Freq. Control 61 (6), June 2014 chirped freq time transfer.pdf K. Davies, Ionospheric Radio, IET (1990) P. Dolea & al., In-situ Measurements Regarding LF Radio Wave Propagation using DCF77 Time Signal Transmitter, TELSIKS 2013 P. Hetzel, Time dissemination via the LF transmitter DCF77 using a pseudo-random phase-shift keying of the carrier, 2nd EFTF (1988) A.D. Watt & al., Worldwide VLF Standard Frequency and Time Signal Broadcasting, J. of Research of the National Bureau of Standards 65D (6), 1961 W.T. Blackband, Propagation of Radio Waves at Frequencies below 300 kc/s (1964) A. Bauch & al., Time and Frequency Dissemination with DCF77: From 1959 to 2009 and beyond, PTB Mitteilungen 119 (3), 2009 J.R. Johler, Propagation of the Low-Frequency Radio Signal, Proc. IRE (1961) D. Engeler, Performance analysis and receiver architectures of DCF77 radio-controlled clocks, IEEE Trans. on Ultrasonics, Ferroelectrics, and Freq. Control 59 (5), 2012 D. Piester, A. Bauch & al., Time and Frequency Broadcast With DCF77, Proc. 43rd PTTI Systems and Appliocations Meeting (2012). All references available on the Library Genesis, gen.lib.rus.ec 32 / 32.
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