#533 – Microwave measurement with Joel Dunsmore

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Welcome, Joel Dunsmore!

Joe worked on the HP 8753 and also wrote The Handbook of Microwave Component Measurement (now in its 2nd edition)

• APC-7 connectors
• HP 8753 was one of the first pieces of test equipment to ship with a microcontroller (a washing machine controller!)
• Error correction in a VNA
• What is a Vector Network Analyzer (VNA)?
• VNAs are great for impedance measurement and antenna measurement. They can measure phase angle, which a scalar network analyzer cannot.
• ADS simulator (Microwave Linear Simulator)
• DANL – Displayed Average Noise Level
• Measuring and correcting
• David Root
• X Parameter
• VNA Calibration 
  • Open, short, and load
  • offset open and offset load
• Fringing capacitance
• Squeezing the cable changes the dielectric constant
• Correcting for bad TV cables
• Combline conductors
• Getting intuitive feel
• 5G system vs ham radio
• Cable cost for high-end measurements
• Keysight VNAs go up to 72 GHz
• Above 70 GHz there are head units
• Above 30GHz it’s referred to as “mm wave” (millimeter wave)
• Who is using 100 GHz? Most satcom is 50 GHz
• Losses in space are lower
• Beamforming is required at such high frequencies
• Starlink teardown
• Phased array antenna
• Professor Gabriel Rabiiz at UCSD
• What’s inside the box?
  • CW signal
  • Swept wave
  • Signal separator or reflectometer
  • directional coupler
• PNA 0-70 GHz
• The key is to try to make a pure signal
• Modern test equipment should measure everything
• Network vs spectrum analyzer
• Hardware swept filter
• Digital filter techniques
• Alan Wolke video about using a scope as a VNA
• Noise / Noise figures
• Make it cold
• Phase noise or jitter
• Driving away from cell tower
• The crystal in the phone is slightly different from the tower
• Multipath
• MIMO
• PXI form factor
• 64 calibration elements put on by a robot (!)
• “little badnesses stack up so fast”
• For million dollar customer problems, Joel gets to be the fixer
• Drifting
• Solving a 50 Hz vs 60 Hz problem
• Microwave components measurements book
  • 1st edition released in 2009
  • 2nd edition released in 2019
• Why are things changing?
• Noise figure analyzer
• Premeasure stuff
• QAM measurements
• Automatic fixture removal
• Higher port counts are more common. Joel gave a presentation on multiport and multi-site optimization.
• Measuring a differential amplifer
• 32 port system for mimo test set
  • n*n-1/2
  • n*((n-1)/2)
• 12 port testers are popular
• Tom Lee
• 6 steps you need to do
• First thing to do with a VNA is try it without any calibration
• Have a regular test setup: Tape thing down
• NIST
• The official reference of impedance is distance
• Calibration from an instrument side is the cal sticker (meets spec on the sheet)
• Load calibration is error correction
• Who is doing the most complex things?
  • Mil / Aero is top tier
  • Cell towers are next
  • Then handsets

Many thanks to Joel and Shamree for making this appearance possible and for donating the books for our giveaway. Joel regularly monitors and responds to comments on the Keysight forum, so that’s a good way to get ahold of him. If you’d like to be entered for the chance to win a copy of the 2nd edition of Joel’s book, please fill out the survey via this link or using the form below. You must include your email address in order to be entered, but it will only be used for the contest.