Daniel Estévez

@destevez.net

680 Followers 67 Following

Everything space & RF. Amateur radio operator (EA4GPZ / M0HXM). PhD in Mathematics from Univ. Autónoma de Madrid. he/him

A screenshot of a GNU Radio GUI showing the spectrum and constellation of the signal.
A plot that shows the loop bandwidth relative error in terms of the normalized loop bandwidth. The error tends to zero when the loop bandwidth tends to zero, and it is already around 0.01% for a loop bandwidth of 0.1.
A plot of space packet APIDs received over time by Bochum
A screenshot of a GNU Radio flowgraph GUI demodulating the signal from Tianwen-2, which has rather high SNR.
A trace shown in the Perfetto UI that shows that the processor performs 8 cycles of vector instructions and then stalls waiting for memory for one cycle.
A screenshot of the Perfetto UI that shows an execution trace. We measure how many cycles it takes to execute each C++ kernel call.
The assembly code for a C++ kernel that performs some 8x8 times 8x8 matrix multiplications. The architecture is VLIW and there are loop registers for hardware-controlled iteration. The main loop is just two instructions that are simultaneously loading data from memory with two load units and performing matrix multiply-accumulate with the vector unit.
A diagram that shows an array of compute tiles and their local memories. Data interconnections between the tiles are shown, including connection of each tile to an array-wide AXI-Stream interconnect, direct memory connections between adjacent tiles, and a cascade connection for accumulator values.
A wireshark listing that shows the decoded MAC PDUs in the uplink and downlink recordings. This shows how the V16 beacon connects to the RRC and sends a control plane service request. The same kind of traffic happens twice.
A constellation of a typical NPDSCH transmission sent to the V16 beacon. There are many symbols which are too large because they are corrupted by interference from other cells. Still, the transmission can be decoded.
A plot of the NPSS amplitude classified by the system frame number modulo 4, since that is how the beaming pattern is organized. There are interference fringes that are caused by different eNBs not having exactly the same carrier frequency due to their disciplination.
An inspectrum waterfall that shows an NB-IoT uplink carrier and an NB-IoT downlink carrier aligned in time. The uplink carrier is sending NPRACH and then an NPUSCH containing an RRC connection request. The downlink has signals from many cells, and it is replying to the NPRACH, although it is barely visible.
A plot of the orbital parameters for Tianwen-1 for the last 4 years.
A series of plots showing the evolution of orbital parameters over time. The data up to 2025-12-22 is based on decoded telemetry. The data afterwards is propagated.
A panel with four plots. Each row corresponds to one of the two spacecraft. The first column shows the rotation rate corresponding to some quaternions. The second column shows what appears to be gyroscope telemetry. We see a good match between the quaternions and the gyroscopes.
A Wireshark screenshot where we see packet analysis on a data transmission done with CSP and RDP.
A screenshot of a terminal where we can see csp-iperf running and showing TX and RX rates and packet counts, round trip time measurements, and number of lost packets.
A waterfall of the uplink transmissions of a beacon when it first begin transmitting. This is the message exchange that is needed to register the beacon in the cell network.
The list of decoded MAC PDUs shown in Wireshark. The main interest is the RRC connection setup complete message, which contains a control plane service request NAS message that embeds the beacon message.
A waterfall of the uplink of a V16 beacon. We can see an m-FSK signal that is the NPRACH, and then some single-tone and multi-tone NPUSCH transmissions.
A plot of the cross ambiguity function of a GPS signal. We see a vertical streak that spans almost 700 Hz. This is caused by the receiver frequency drifting during the 300 ms integration that is used to make this plot.
An image showing the cross ambiguity function of a GPS signal. The correlation peak has high SNR and is clearly visible.
Some log messages extracted from the telemetry: /mnt/mmc0/logs/compton/inv_sts/inv_sts-1763132730.mtc.gz /mnt/mmc0/logs/compton/inv_eps/inv_eps-1762763341.mtc.gz /mnt/mmc0/logs/compton/inv_cdh_spoc_misc/inv_cdh_spoc_misc-1762770516.mtc.gz E_CMD_HIST: [ OK ] EPS_SPOC_DIO_ST_OCP_EN ENABLE_STATE=[0, Off] E_CMD_HIST: [ OK ] CDH_SPOC_IO_GPIO_STATE_SET IDX=[109] STATE=[0, E_Low] E_CMD_HIST: [ OK ] FJ_ABORT, Proc: CommsFallback E_INFO: set_st_power_state: End sequence E_CMD_HIST: [ OK ] MISC_SYSTEM, STRING: echo 'WAIT(2)' >> /tmp/BackorbDownload.fj E_CMD_HIST: [ OK ] MISC_SYSTEM, STRING: sed -i '$d' /tmp/BackorbDownload.fj E_CMD_HIST: [ OK ] MISC_SYSTEM, STRING: rm /tmp/*_files_list.txt E_CMD_HIST: [ OK ] MISC_CONFIG_PARSE, String: tlm_master.set_apid_freq(620, 0.05); E_CMD_HIST: [ OK ] FJ_START_ABS, Time: 1763146080.000000, File: CommsFallback, Args: E_CMD_HIST: [ OK ] FJ_START_REL, Seconds: 3600.000000, File: DisableComponents, Args: STA E_CMD_HIST: [ OK ] FJ_START_REL, Seconds: 0.000000, File: BackorbInit, Args: E_CMD_HIST: [ OK ] MISC_SYSTEM, STRING: echo PROC BackorbDownload > /tmp/BackorbDownload.fj E_CMD_HIST: [ OK ] MISC_SYSTEM, STRING: echo \'CMD "MISC_SYSTEM" ("gzip -c -f -k /tmp/BackorbDownload.fj > /tmp/BackorbDownload.gz")\' >> /tmp/BackorbDownload.fj E_WARNING: LoadProc (File: FJExecute.cpp Line: 1205): Procedure found in working directory, executing: /tmp/BackorbDownload.fj E_INFO: SetThermostatMode: Setting thermostat 'EESA' to mode ClosedLoop E_INFO: SetThermostatSetpointsClosedLoop: new setpoints for ON -35.000000 deg C. OFF -30.000000 deg C.
A waterfall of the ESCAPADE-Gold telemetry signal. It shows that there are significant changes in power over time. There is a gap caused by a problem with the recording. The signal resumes at a slower data rate after the gap.
The release changelog. Update Maia SDR to v0.12.0. Updates dependencies. Update IQEngine to latest main. Add IPv6 link-local address fe80::1/64 to simplify connecting to the Pluto by ssh before the IPv4 network is configured (for instance this can be used in Android devices that use an address of the form 10.xxx.yyy.zzz/24, which is not covered by the ipaddrmulti feature) Include IP from fw_printenv ipaddr in the Subject Alternative Names of the maia-httpd SSL certificate.
A screenshot of Inspectrum that shows a waterfall containing multiple packets. Each packet is bounded with an annotation. There are also annotations for reply packets, which are not visible in the waterfall. The mouse is hovered over one packet, and the tooltip shows a dump of an IPv4 ping packet generated with Scapy.
A formula of the symbol error rate for m-FSK. It is a summation with m - 1 terms that contains a binomial coefficient and an exponential term that depends on the Es/N0.
A simulation of a setup timing violation. A data transition from zero to one is done increasingly close to the clock rising edge. We can see the corresponding outputs in traces of different colours. As the data transition approaches the clock edge, the output delay increases a lot, until the new data is no longer captured.
A simulation of output delay. Two clock cycles are simulated, and the data input first is one and then is zero, so we can see how the input data propagates to the output after the clock rising edge. Different process corners are shown with different colours in the flip-flop output voltage trace, so we can see the difference between the fastest and slowest corners.
Two ASIC cells. The one on the top, which is the flip-flop I have designed is half as tall as the one on the bottom, which is the equivalent cell from the standard library. My flip-flop is also slightly narrower. There is a large difference between the transistor size in both cells, and also the amount of room available to route all the signals. The standard cell can route everything in one metal layer, while my flip-flop needs three metal layers.
A photo of an assembled PCB. It is a small board with an SMA connector, a few surface mount chips, a pin header, and tiny 0402 passives.
A false colour image that shows short wave infrared in red, near infrared in green and visible green in blue. Vegetation looks green or bright green, depending on density. The burnt area looks red, except for some surviving vegetation which can still be seen in green.
A false colour image that shows vegetation surviving the fire in green, vegetation lost by the fire in magenta and burnt areas of low vegetation in blue. In green we can see the parks in Tres Cantos, and the creeks and forests highlighted. In magenta we see a large part of the Monte de Viñuelas woodland, which has been burnt severely, as well as some creeks badly affected by the fire. In blue there are areas of dry grass pastures that have burnt, mostly outside of Monte de Viñuelas and northeast of Tres Cantos. There are spotty blue-green areas in the eastern part of Monte de Viñuelas, showing partial fire affectation with trees surviving.
A satellite image on a cloudless day a few days before the fire. It is shown for comparison.
An animated GIF that toggles between two satellite images of the same area. One was taken on a cloudless day some days before the fire. The other one is from the day after the fire. There are some clouds, but most of the burnt area can be seen through a break in the clouds.
The changelog of the release: Added Added callsign to deframer options Basic support for SigMF input CSP Address Filter block CSP ZMQ blocks Frame counter block Mobitex-NX deframer Support for JINJUSAT-1B Support for Hex20 Nila Support for NUSHSAT-1 Support for TEVEL2 satellites Telemetry decoder for TUBiX20 (TUBIN) Time-dependent delay block Time synchronization tag to Doppler correction block U482C encoder block Uplink argument to tle_to_doppler_file.py example Fixed Callsign '-' handling in Check AX.25 Address Packet size bug in AX100 deframer pybind11 bug in swap_header Timezone handling in PDU to KISS Changed Added callsign in SatYAML to BEESAT-1,-9, TUBIN, NanoFF-A,-B, and TechnoSat Improved version printout in gr_satellites CLI app Updated AX.25 packet radio examples Use GNU Radio crc_check in GNU Radio >= 3.10
An inspectrum waterfall that shows a 100 MHz 5G cell that is rather busy. We can see 7 SSB repetitions, and mostly empty uplink slots, since this is a TDD band.
A photo of a small PCB with an SMA connector connected to an attenuator, two leads to supply power, a green LED, and a bunch of surface mount components, including three QFN chips.
A diagram taken from the ICD that shows how the TESLA chain renewal happens in two steps. In the first step, the KROOTs for both chains are transmitted alternatively and the chain and pubkey status is end-of-chain. In the second step, the system transitions to using the new chain.
A plot of the value of the FLL frequency accumulator during lock-in. The legacy GNU Radio loop filter and the new fixed loop filter are compared. Both converge almost at the same time, but the legacy filter has more noise after convergence.
A plot of the discriminant curves of the GNU Radio and Remez band-edge filters obtained via simulation. They are compared with the slope given by the theoretical gain at zero error.
A plot that compares the GNU Radio FIR filter, which extends the ideal quarter-sine band-edge to a half-sine, and a Remez design, which has more ripple but a narrower transition down to zero.
A plot of the spectrum of an RRC waveform and ideal band-edge filters. The band-edge filters are equal to the derivative of the RRC, so they are non-zero only in the roll-off region.
A screenshot of a GNU Radio GUI where we can see the soft symbols in the time domain and the output of a G3RUH descrambler. The descrambler output is all zeros.
A screenshot in Wireshark that shows part of the SIB1 message parsed out. The PCAP file also contains the MIB transmission from the PBCH, which happen every 10 ms.
A plot of the LLRs after the first LDPC decoder iteration. Many punctured bits are still not solved and have an LLR of zero.
A waterfall of the IQ recording, which shows annotations marking the PDSCH, and other transmissions such as the PDCCH, the PSS, SSS and PBCH, and the CSI-RS.
A plot of the output LLRs of Polar decoding for a DCI candidate size of 34. Some LLRs are very close to zero, which means that decoding has failed.
A table from an online calculator that shows how CCEs are mapped into REGs by forming REG bundles and applying a permutation.
A constellation plot of the two symbols of the PDCCH. It shows a QPSK constellation for the data and a wipe-off pilot signal for the DM-RS.
A waterfall of a 5G downlink signal. We can see the PBCH/SS block on the left, then a PDCCH transmission split into two segments in frequency, a PDSCH transmission immediately afterwards (which is the SIB1), and finally a CSI-RS which is sparse in frequency.
A screenshot of the GUI of a GNU Radio flowgraph. Several plots that show the behaviour of the Time-dependent Delay block can be seen. These include a plot of the phase versus frequency of the correlation of a delayed AGWN with the original AWGN, a plot of time-domain pulses with tags passing through the delay, and plots of the spectrum of a CW carrier passed through the delay, which gets slightly shifted in frequency due to the delay-rate.
A plot with the same title as before: Frequency difference between Bochum and Dwingeloo (with Doppler for Mare Crisium subtracted). The curve is now different. It is a noisy ramp that increases from -1.75 Hz to 0.75 Hz.
A plot of the frequency difference between Bochum and Dwingeloo, with the Doppler for Mare Crisium subtracted. The plot looks like a noisy sinusoidal curve with an offset of 55 Hz and an amplitude of 0.5 Hz.
A 55x25 mm PCB with two SMA connectors (one optional for a 10 MHz reference).
A plot of the power spectral density of the signal as received in Stockert and Dwingeloo. The plot is normalized so that the noise has mean zero and standard deviation one, so the detection values in sigmas can be read directly. There is a continuous trace showing the measurement of the PFB spectrum analyzer with 0.5 Hz bins, and a dashed trace that is a moving average of 5 of these bins.
A plot of the frequency response of 3 bins of a polyphase filterbank. The polyphase filterbank is oversampled by a factor of 2 in frequency, so the bins overlap by 50%. The non-coherent sums of the bins are also show. The response of these sums is flat even in the edges of the bins, since the skirts of the filter have been adjusted to achieve this.
A plot of a model of Doppler spread for the radar reflection. It looks roughly like a bell shape curve with a width of about ±1 Hz.
A plot of the radar scattering angle on the surface of Venus. The plot is an orthographic projection centred on the sub-radar point at 9.5º S, 13.8º W. The back side of Venus is not illuminated by the radar.