My personal TODO list.

Todo

Short Term

• Investigating a Fuse-GDT-TSS protection circuit.

  • Abstract: A series fuse in parallel with a Gas Discharge Tube (GDT) or Thyristor Surge Suppressor (TSS) is useful for protecting a port from overvoltage. But its effectiveness and signal integrity impacts on high-speed data lines need to be tested and measured. A custom high-voltage pulse generator must be designed to evaluate effectiveness, full S-parameters measurements are needed to quantify signal integrity impacts.
  • Difficulty: Medium.
  • Planned: 2022-06-19 18:46:30+00:00
  • Updated: 2022-07-20 01:58:28+00:00
  • Status:
    1. First test board received, initial S-parameters data gathered. As expected, there’s a large signal integrity impact. Additional board submitted for impedance tuning, I still need to design an HV pulse generator to evaluate protection effectiveness (2022-06-30 09:08:07+00:00).
    2. A prototype, makeshift HV pulse generator has been constructed, and this provided quite a lot of insightful experimental data. However, this is insufficient, a proper impulse generator still needs to be designed. (2022-07-20 01:58:28+00:00)
  • Project Log: Link

• Designing a 8/20 μs high-voltage impulse generator

  • Abstract: In order to test the performance of surge protection circuits, a makeshift HV pulse generator has been previously constructed (simply dischanging a 200 V, 22 μF capacitor via an SCR), and this provided much insightful experimental data. However, a more advanced HV impulse generator is needed beyond an improvised, quick-and-dirty circuit, which can only provide limited engineering values. The new generator would generate a 8/20 μs current surge (a.k.a. 1.2/50 μs voltage surge) according to IEC 61000-4-5, the most widely used international and industrial standard for testing devices under pulsed power and surges. This particular design is expected to be capable of producing surges up to 1500 volts - sufficient to test devices up to and slightly beyond Level 2.
  • Difficulty: Medium.
  • Planned: 2022-07-13 14:31:02+00:00
  • Updated: 2022-09-16 01:35:13+00:00
  • Status:
    1. The first generator breadboard prototype has been successfully tested (2022-08-11 13:55:26+00:00).
    2. Now I’m designing a 1 kV HV power supply (2022-09-12 22:54:05+00:00).
    3. I’ve successfully generated The first 1000 V, 500 A impulse (2022-09-16 01:35:13+00:00).
  • Comment: I’d just like to interject for a moment. What you’re referring to as a “8/20 μs surge”, is in fact, a 1.2/50-8/20 μs surge, or as I’ve recently taken to calling it, the output from a 1.2/50 µs combination wave generator. The 8/20 μs waveform is not a surge unto itself, but rather just the generator’s short-circuit current output as defined by IEC 61000-4-5. It’s normally generated in combination with the 1.2/50 µs open-circuit voltage waveform. All the so-called “8/20 μs wave” is really the “1.2/50-8/20 μs” combination wave…
  • Project Log: Link and Link

• Finalizing the design of the High-Speed USB galvanic isolator board.

  • Abstract: A prototype board for high-speed USB galvanic isolation has been designed, but the initial version has a bug. The next version should be designed with a new power multiplexer circuit and the protection circuit based on the results from the Fuse-GDT-TSS tests.
  • Difficulty: Medium.
  • Planned: 2022-06-19 18:46:30+00:00
  • Project Log: Link

• Finalizing the design of the USB 3.0 over fiber optics isolation & extension board

  • Abstract: A prototype of transmitting a USB 3.0 signal over fiber optics has already been designed and shown to work, within the limitation of the quick and dirty method. A revised redesign is needed to convert it to a presentable project and a concept demo on the web.
  • Difficulty: Medium.
  • Planned: 2022-06-19 18:46:30+00:00

Long Term

• An automatic USB device tester

  • Abstract: To facilitate the testing of USB devices, an automatic USB device tester needs to be designed. It should be at least capable of automatic power cycling, switching the High-Speed and Super-Speed data lines.
  • Difficulty: Low.
  • Planned: 2022-06-19 18:46:30+00:00

• A T/R or multiplexing switch for the NanoVNA

  • Abstract: The NanoVNA is a 1.5-port (or three-receiver) VNA only capable of measuring a device in one direction. When testing a non-reciprocal or non-symmetric device, tedious connections and reconnections are required. A similar problem exists when testing a multi-port device. It should be possible to use an external multiplexer circuit to automate this process. The calibration process can be messy and with lower accuracy than a direct connection, but shouldn’t degrade by too much since the multiplexer itself can be de-embedded using its own S-parameters.
  • Difficulty: Low.
  • Planned: 2022-06-19 18:46:30+00:00

• Designing a leveled sine-wave generator

  • Abstract: A “leveled sine-wave generator” is a special equipment for oscilloscope and RF power probe calibration. It can output a sine wave with an accurate amplitude (power) higher than all general-purpose lab signal generator, around 0.3 dB and can be lower. It’s extremely rare to see one outside a calibration lab. But it’s conceptually simple - sampling its the output power using an external “output head” and feeding the signal back to the Automatic Level Control circuit. Back in the 1970s, Tektronix did it with a diode peak detector in the legendary SG503 & SG504. Replicating its technology today would be a notable contribution to the amateur electrical metrology (“voltnuts”) community.
  • Difficulty: High.
  • Planned: 2022-01-31 17:20:17+00:00
  • Updated: 2022-05-07 18:35:40+00:00
  • Status: Experiments were attempted to replicate this design, 20% complete, but interrupted by a yet-to-be-repaired equipment fault.
  • Project Log: Link

• Method for Measuring output VSWR for an active levelled signal generator

  • Abstract: In RF calibration, knowing the output impedance (or reflection coefficient, or VSWR) of a signal generator is extremely important. However, since the output of a leveled sinewave generator is actively regulated via feedback, it’s a nonlinear circuit and cannot be measured with standard methods. The Federal Office of Metrology in Switzerland has proposed a new method using a directional coupler, multiple delay lines and solving nonlinear least-square equations on a computer. However, a detailed write-up in article form on this technique and a comparison with other methods don’t exist. Replicating the experiment and writing a blog post would be useful to to the online radio/microwave community.
  • Difficulty: Medium.
  • Planned: 2022-04-14 23:21:18+00:00
  • Updated: 2022-05-07 18:35:40+00:00
  • Status: Experiment has been successfully replicated! But I still need to do a comparison with other methods, but it was interrupted by a yet-to-be-repaired equipment fault.
  • Project Log: Link and Link

• Comparison of free and open source transmission line characteristic impedance calculators

  • Abstract: In radio and high-speed digital electronics design, calculating the characteristic impedance of a transmission line on a printed circuit board is of critical importance. The industry standard calculator, Si9000, is not just proprietary but also with a licensing fee of many thousand dollars. In the free world, many calculators exist, from the simple program based on closed-form formulas such as transcalc (integrated in Qucs and KiCad), to 2D field solvers like ATLC and TNT-MMTL, to full-wave 3D E&M field solvers like openEMS and MEEP. It would be insightful to compare their results for common transmission line structures.
  • Difficulty: Very High.
  • Planned: 2022-06-11 12:44:11+00:00

Done

• Three-Receiver VNA SOLT calibration documentation for scikit-rf.

  • Abstract: scikit-rf is a free and open source Python library for performing RF engineering calculations. Currently, its documentation on SOLT calibration for the three-receiver VNA architecture is lacking, which is confusing for new users.
  • Difficulty: Low.
  • Planned: 2022-06-17 22:52:31+00:00
  • Updated: 2022-06-19 18:33:57+00:00
  • Status: Done. Relevant clarifications have been included in v0.23.0, although I still plan to write more documents in the future.