What’s a TDC?
A time-to-digital converter (TDC) is sort of a stopwatch measuring the elapsed interval between two occasions with picosecond precision, changing this right into a digital worth for post-processing. Many house functions require time-of-flight measurements to calculate distance, delay, or velocity. For instance, an in-space servicing, meeting, and manufacturing (ISAM) spacecraft wants to find out exactly the relative location of particles earlier than initiating rendezvous and retrieval operations. Equally, space-domain consciousness should perceive the proximity and trajectory of different orbiting objects to evaluate any potential menace.
A TDC receives two inputs: a begin sign (or edge) to mark the start of the time interval to be measured, and a cease pulse. The delay between these is transformed to a digital quantity for post-processing. Completely different architectures are usually used to implement the logic, e.g., counters, delay strains, or a time amplifier.
Time-to-digital conversion is a method utilized in space-based LiDAR methods to measure the time taken for a light-weight pulse to journey to and from an object to calculate its distance. A LiDAR emits a laser pulse in the direction of a goal, which displays off the latter’s floor, returning to the sensor. The TDC begins counting when the heartbeat is transmitted, stops when it’s detected by the receiver, and utilizing the pace of sunshine, the gap is calculated as:
the place c is the pace of sunshine and t is the time-of-flight.
TDC in LiDAR
For instance, LiDAR is utilized by some Earth-Commentary operators to measure altitude and floor modifications over time, to, for instance, monitor vegetation top, ice sheet or glacier thickness and soften, sea-ice elevation or relative sea degree. Spaceborne LiDAR altimetry is able to centimetre-level vertical precision and is illustrated in Determine 1.
Determine 1 Using TDC in space-based LiDAR functions. Supply: Rajan Bedi
Equally, a TDC is utilized in mass spectroscopy to measure how lengthy it takes ions to journey from a supply to a detector. This time-of-flight info is used to calculate the mass-to-charge ratio (m/z) of ions, and for the reason that kinetic vitality given to all ions is identical, time-of-flight is immediately associated to their mass as follows:
the place t is the time of flight, ok a calibration fixed, m the ion mass and z the ion cost.
TDC in mass spectroscopy
Area-based mass spectroscopy has many functions to establish and quantify chemical composition by measuring the mass-to-charge ratio of ions. For instance, Earth Commentary and house climate monitor the make-up of the Earth’s ionosphere and magnetosphere, together with photo voltaic wind particles. Area science analyses the chemical construction of planetary atmospheres, lunar and asteroid floor composition, in addition to soil or ice samples to detect natural molecules and potential indicators of life. Time-of-flight mass spectroscopy is illustrated in Determine 2.
Determine 2 Using TDC in time-of-flight mass spectroscopy. Supply: Rajan Bedi
TDC in optical communications
Optical communication is more and more getting used to transmit knowledge wirelessly between orbiting satellites, corresponding to intersatellite hyperlinks, or hyperlinks from the bottom to a spacecraft. Excessive-throughput payloads at the moment are utilizing fibre to ship knowledge inside sub-systems to beat the bandwidth, loss, mass ,and EMI limitations of conventional copper communications.
TDCs are used to detect when photons arrive, for timing-jitter evaluation to forestall degradation of system efficiency, clock restoration, and synchronization for aligning and decoding incoming knowledge streams, as proven in Determine 3.
Determine 3 Using TDC and fibre-based optical communications inside a payload. Supply: Rajan Bedi
TDC to calculate absolute time
TDC can also be used to calculate absolute time with the assistance of satellite tv for pc navigation for functions corresponding to quantum key distribution over lengthy distances. Each the transmitter and the receiver use GNSS-disciplined oscillators to synchronize their native system clocks to a worldwide time reference corresponding to UTC or GPS time. A exact timestamp (Toccasion) may be calculated as:
the place TGNSSepoch is absolutely the time of the final GNSS PPS sign, e.g., 14:23:08 UTC, N is the variety of clock cycles for the reason that PPS, Tclk is the clock interval, and tpositive is the sub-nanosecond positive time from interpolation.
For instance, if the TDC counts 8,700 clock cycles with a interval of 1 ns and tpositive = 0.217 ns, the ensuing timestamp may be calculated as:
The system idea primarily based on optical communications is illustrated in Determine 4.
Determine 4 Using TDC to calculate absolute time for quantum key distribution. Supply: Rajan Bedi
MAG-TDC00002-Sx TDC
Magics Applied sciences NV has simply launched a rad-hard TDC for house functions: the MAG-TDC00002-Sx is proven in Determine 5 and may measure time delays with picosecond precision, changing this to a digital worth for publish processing. The machine gives an SPI slave interface to connect with FPGAs/MCUs for configuration and read-out of the elapsed time.
Determine 5 Magics’ TDC00002-Sx, Rad-Arduous TDC that may measure time delays with picosecond precision. Supply: Magics Applied sciences NV
The MAG-TDC00002-Sx operates from a core voltage of 1.2 V, and its I/O may be powered from 1V8 to 3V3. The machine consumes 20 mW (typical) and has a specified working temperature from -40°C to 125°C. The MAG-TDC00002-Sx is available in a 17.9 x 10.8 mm, 28-pin, airtight, ceramic COIC bundle.
The structure of the MAG-TDC00002-Sx and an software drawing are proven in Determine 6: following power-up and initialization (lock) of the inner PLL, the TDC enters an IDLE state. When the machine is configured, a pulse is generated on the TRIGGER output, and the TDC modifications to a LISTEN mode. On this state, the inner 1.25-GHz counter is operating and might be sampled on receipt of exterior begin and cease alerts. The values are saved to their corresponding registers, and each coarse and positive measurements may be learn out through SPI to calculate time-of-flight.
The MAG-TDC00002-Sx has computerized, inside self-calibration, which corrects for drifts attributable to course of, voltage, temperature, and radiation degradation.
Determine 6 The structure and software drawing of MAG-TDC00002-Sx. Supply: Magics Applied sciences NV
For example, a time-of-flight measurement between a single begin and cease occasion resulted within the following MAG-TDC00002-Sx register knowledge:
START BIN DEL = 121
STOP BIN DEL0 = 28
START BIN CAL PERIOD = 110
STOP BIN CAL PERIOD0 = 110
START BIN CAL OFFSET = 8
STOP BIN CAL OFFSET = 9
START CNT VAL L = 4
START CNT VAL H = 0
STOP CNT VAL L0 = 14
STOP CNT VAL H0 = 0 The calculation of time-of-flight is:
By way of radiation hardness, the MAG-TDC00002-Sx has a specified SET/SEU tolerance of 60 MeV·cm2/mg and a total-dose immunity > 100 kRad (Si) / 1 kGy (Si). Radiation stories and ESCC9000 qualification are anticipated in Q3 of this yr, and EM and EQM components may be ordered as we speak. The machine is European and ITAR-free, which is advantageous when you’ve got import/export considerations!
MAG-TDC00002-Sx analysis package
To prototype and de-risk the MAG-TDC00002-Sx, an analysis package is offered comprising a base board and a TDC PCB as proven beneath. The latter suits on prime of the previous utilizing the socket headers, and the bottom board connects to a PC utilizing a USB Sort-C cable as proven in Determine 7.
Determine 7 MAG-TDC00002-Sx analysis package with a base board and TDC PCB. Supply: Magics Applied sciences NV
The analysis package comes with software program that communicates with the bottom board utilizing SCPI instructions to configure and use the MAG-TDC00002-Sx as proven in Determine 8.
Determine 8 A screenshot of MAG-TDC00002-Sx analysis package software program utilizing SCPI instructions to configure the machine. Supply: Magics Applied sciences NV
The rad-hard TDC is well-suited for producers of Earth-Commentary LiDAR devices, space-science mass spectrometers, ISAM/space-domain consciousness proximity detectors or high-throughput optical communications transceivers for calculating time-of-flight. The MAG-TDC00002-Sx will also be used to calculate absolute time for functions corresponding to safe quantum key trade through satellite tv for pc.
Additional details about Magics’ MAG-TDC00002-Sx might be shared in a webinar to be broadcast on 22nd Could, and you’ll register utilizing this hyperlink.
Dr. Rajan Bedi is the CEO and founding father of Spacechips, which designs and builds a spread of superior, AI-enabled, re-configurable, L to Okay-band, extremely high-throughput transponders, SDRs, Edge-based on-board processors and Mass-Reminiscence Items for telecommunication, Earth-Commentary, ISAM, SIGINT, navigation, 5G, web and M2M/IoT satellites. The corporate additionally gives Area-Electronics Design-Consultancy, Avionics Testing, Technical-Advertising and marketing, Enterprise-Intelligence and Coaching Providers. (www.spacechips.co.uk).
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