Concrete evaluation for cracks

any one on this forum kindly help in my project. i want to evaluate concrete slab for cracks in my project. For this purpose i crated a microstrip patch antenna on hfss using fr4 substate at 1.2 ghz freq in hfss.

q1) is microstrip good for concrete evaluation as other antennas are not available in my country?

q2) should i insert U slot to make wide band?

q3) how to find lengths of u slot when using fr4 substrate read many research papers could not find any formulas by hit and trial its not working.
the return loss required is -10 from where i can calculate bandwith but inserting U slot wont give the required return loss.

q4) After antenna is designed on hfss what should i do next as i have to implement on hardware also.

q)6our supervisor says we have to get resolution of concrete cracks how do we get resolution?

q)7 As project is not gpr. i want to have tx and rx antennas which should strike concrete and after reflection it should be received.

q)8 how should i give power to tx and rx antennas. should i use oscilloscope or any modules?

waitng for reply. (new sorry for my bad english).

I don't know much about the method you're using, so I cannot advise how to improve it. But it reminds me of seismic exploration by acoustic means.

Attach a sending transducer firmly. Send shock waves through the block, at various frequencies. Use one or more attached receiving transducers, to test for uniform echo response through the block.

A fracture within the block will result in non-uniform echo response.
Or, there will be two echo frequencies displayed.
Or, the pattern will differ in some way from that of a solid block.

BradtheRad said:

I don't know much about the method you're using, so I cannot advise how to improve it. But it reminds me of seismic exploration by acoustic means.

Attach a sending transducer firmly. Send shock waves through the block, at various frequencies. Use one or more attached receiving transducers, to test for uniform echo response through the block.

A fracture within the block will result in non-uniform echo response.
Or, there will be two echo frequencies displayed.
Or, the pattern will differ in some way from that of a solid block.

Click to expand...

As your task is difficult, first you should study e.g by Google if someone did ***** detection by RF.
I have studied how to measure concrete permittivity during the curing process but not the cracks.

As above, one known method is to hit concrete by a hammer and analyze sound response. There are commercial instruments using sound and ultrasound that can detect cracks.

To use RF, you should experiment with your antennas at 1.2 GHz. You must use a RF signal generator and a detector and test healthy and cracked concrete samples. There are some arrangements that can detect cracks, like differential, bridge, etc.
THere is no EASY solution but a hard work ahead. Good luck!

i see. can any one tell why my return loss is very low in this design. i want more then 10 db. can't find the problem. View attachment SA.rar