I'm trying to find a way to measure SWR digitally. Generally SWR is measured with analogue equipments and it is not practical on self designed PCB. I did not find so much resource on how to do it digital way.
I have 10 Mhz hcmos oscillator which is filtered and converted to sine wave. The most simple idea which came to my mind was, connect PCB's sma output to also an ADC of uC in PCB design. I'm sure there should have been some more clever solutions.
Best Answer
To measure VSWR of a load accurately, you need to measure two things: The power outbound toward the load, and the reflected power returning from the load.
The reason for measuring the outward going power is that many generators will change their output capability slightly, depending on the reflections coming back from the load. For example, in your setup, the filter that's converting your 10 MHz square wave to a sine wave is likely to change it's characteristics depending on the effective load impedance it is seeing.
In order to measure the outward and inward-travelling signals separately, it's usual to use a directional coupler, or a combination of directional couplers.
You can buy a reasonably-specified pcb-mount directional coupler from a company like Mini-Circuits, or, particularly since you are interested only in 10 MHz or a narrow range of frequencies around it, you may be able to construct one(PDF link) yourslef.
Having separated the the forward and reverse signals, you should consider rectifying each one with an rf detector rather than sampling directly with a fast A/D. The detector will convert each signal to a "dc" level which can be sampled with a low-speed, low-cost A/D.