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 and external coupler. The AD9851 generates a sinewave upto 180 MHz which is filtered before being amplified. The wave is transmitted 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 ATMEGA16U4 is there to read the reflected voltage and control the signal generator by I2C. The voltage information is sent to a PC for further analysis/plotting.