Arduino voltage standing wave meter based on Brett Killion's Network Analyzer design. See https://hackaday.io/project/10021-arduino-network-analyzer for his fabulous work!
This design improves on Brett's work by putting the Arduino, analyzer and bi-directional coupler on one PCB, thus eliminating one RF connector.
The AD9851 generates a sinewave upto 180 MHz which is filtered before being amplified. The wave is transmited via the directional coupler to the antenna under test. The reflected wave is guided by the Mini Circuits PDC-20 RF directional coupler to the AD8307 logarithmic amplifier. The ATMEGA328P-AU is there to read the reflected voltage and control the clock generator by I2C.
The voltage information is sent to a PC for further analysis/plotting.