narrow beamwidth low sidelobe for detection application

[kae_jolie]

I need to know if a narrow beamwidth with low sidelobe array would help in the detection of objects like tumors beneath skin or in the detection of objects under ground for Ground Penetrating Radar (GPR).

Also, how would the scan angle (wide or narrow) aid in the detection of such object? I am trying to detect breast tumors using a phased array antenna and I am not sure if a narrow or wide beam with low or high sidelobe would improve the detection and why?

Please elaborate with references, if possible.

Thank you.

 

[chuckey]

As you use the same aerial for transmit and receive, reducing the beam width, should give you better resolution and higher gain on both transmit and receive. As this is for medical use, the beam must be very small (>10mm diam?), so side lobes can be eliminated by firing the main beam through a hole surrounded by a material that is lossy at your working frequency. At a place where I worked a satellite transmission dish was actually put in a deep hole and surrounded by a large earth bank to reduce side lobes that would have interfered with a telecomms microwave site a couple of miles away.
Frank

 

[kae_jolie]

thanks, Frank. Why would a narrower beamwidth give me better resolution, though? Also, I will be using a UWB antenna so I am not sure how the idea about using a slit to eliminate sidelobes would work with that. Also, what role, if any, would the scan angle play in the detection process?

Did you do remote sensing applications at the satellite place you worked at?

Thanks.

 

[tony_lth]

Pu in a deep hole, that is very interesting. I am just curious about how deep it is? And surrounded by earth, how much attenuation for the side lobe?
I appreciate for any comments. Thanks.

 

[chuckey]

The dishes were 6m diam, giving about 8m from the base to the top of the dish. The top of the dish was about 2m below the top of the earth bank.
"Did you do remote sensing applications at the satellite place you worked at?" I am not sure what you mean. I was involved in the remote control of the whole kit, from the mains supply, air conditioning kit, input signal selection and transmitters to the error of the dish pointing system, - which was about .01 degrees. It was one of the biggest uplink sites in the UK - about 40 dishes/ 80 services.
Frank

 

[jiripolivka]

Detecting tumors in a breast (or other) living tissue is a grave problem. If you think about using a phased array, you should also know that there are two important problems to solve;

Transition from air into the tissue is a difficult boundary, air with the permittivity of 1, and tissue having 20-100 (water has ~81).
Tissue complex permittivity is not only high but irregular (and living tissue has moving sections), so no phasing can be achieved.
Maybe you know the interferometer attempts by Leroy's group in 1980s. On phantoms it worked, in a real tissue, it did not.
Good luck!

 

[biff44]

I am sure that multiple antenna array would help. However, I suspect that a better processing approach would be to treat each antenna as independent, and use them to form a MIMO type system. You could use some training sequence to figure out the "multipath" effects inside of the human tissue, even if it is moving.