Real-time six-port reflectometer

An account is given of a six-port reflectometer able to make a single measurement in 2 ms and display the results in a Smith chart format suitable for the assessment of components with moving parts, such as tuning screws, sliding loads or resonant circuits. The system is based on a Z80-A (8-bit) microprocessor with algorithms written for 12-bit arithmetic. The assembled machine code takes up 1 k byte of the computer´s memory with a further 28 k bytes occupied with correction look-up tables for Schottky barrier diodes which measure power over a range of ¿50 dBm to +16 dBm. Demonstration photographs are presented of measurements on resonant circuits and also the effect of noise at low power levels.