I am trying to recreate the transmit part of the HB100 doppler radar. I know what oscillator we have to use but when I look a the PCB board I am totally stumped as I am not sure what resistor capacitor stub size they have used. ANywyas to back track and create a PCB baord from the tear down.
Hi @vidhugop,
You want to replicate a $4.90 circuit to use in your own design? Not sure what you mean with “what size” since that is easily measured with calipers, but I would guess that you’re uncertain about what values of components they have used? If so, you should get a LCR meter to check this. I have this simple one from Ebay and it’s quite good. Desolder each component before measuring 
As @jensa mentions, you can measure the component values using something like an LCR-meter. I’m not sure if that is of any help unfortunately.
I’m not familiar with the module, but a quick search shows it’s an X-band device. At such high frequencies, the paracitics of the components are significant. E.g. a capacitor if the same value, but not the exact same chip, will have vastly different properties.
I assume the device uses a fair bit of distributed elements, as opposed to lumped components. If this is the case, then you can simply measure the geometry on the PCB. With such a high frequency, a few millimeters offset on the geometry will give vast differences in the circuit behavior.
I’ll reccomend taking a look at David M. Pozar, microwave engineering (book).
If you have some pictures of the circuit, we’ll likely be able to come with better suggestions.
You’ll probably need a VNA, a signal generator and a spectrum analyzer if you want to recreate the device and obtain sufficient performance.