• madengr
    16
    I have been making some videos:

    The first shows a coaxial short circuit has no inductance, thus the L0..L3 terms in the VNA cal standard are zero (unlike the open), at least for 3.5 mm. The 1.85 mm supposedly has a slight amount, probably due to machining tolerances. It shows where circuit intuition fails and why need to consider the TEM wave.



    The second uses EM simulation port field plots to size the wall for a microstrip short circuit, comparing the error to an ideal short. Again, properly terminating the (quasi) TEM wave.



    The third shows how to design a compact PCB inverted F antenna, and how it evolves from a monopole and inverted L. Uses 2.5D EM for the the design, then 3D for finite PCB effects, then exporting Gerbers. Covers some of the advanced features of Microwave Office, such as multi-layer PCB stackups, geometry creation rules, and simplification rules for meshing.

  • madengr
    16
    Video 4 shows how to use FlatCAM to process the Inverted F Antenna (IFA) gerbers into G-Code, which is then used on the PCB milling machine.



    Video 5 shows how to tune the IFA using a VNA, and discusses use of a calibration kit.



    Video 6 shows testing of the antenna by measuring C/N0 using a GNSS receiver module.
  • madengr
    16
    Video 7 details a coupled loop fixture designed to measure the quality factor (Q) of surface mount (SMT) resonators to 1 GHz.

    The fixture has adjustable loop spacing to null the magnetic coupling between the loops. The design and analysis is performed in Cadence AWR Microwave Office using the Axiem and Analyst electromagnetic simulators.

    The initial design has poor high frequency isolation due to common mode currents on the interconnects. The design is revised using EM simulation to show additional isolation may be achieved with the addition of ferrite loaded baluns.

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