Thermal Noise source for Microwave radiometer

Hi Guys..

I'm designing a microwave radiometer and I want to design a thermal noise source model in ADS as an input source to radiometer system. My radiometer is designing to detect hot spots inside a dielectric material and for simulating the radiometer in ADS, I need to design a thermal noise source represent these hot spots....So, I need your help to give me some ideas for modeling like this source.

Thanks in Advance

Can you, please, indicate what is your radiometer operation frequency?
In my experiments I have used low-cost satellite LNBs at 11 GHz; at that frequency, e-b diode of a RF SMD transistor can be used as a good noise source with ~30 dB ENR, for free. I used similar setup to measure sand moisture on sand moving on a conveyor belt as well as I built small radio telescopes with satellite LNBs; I use the SMD e-b diodes as calibration noise sources.

jiripolivka said:

Can you, please, indicate what is your radiometer operation frequency?
In my experiments I have used low-cost satellite LNBs at 11 GHz; at that frequency, e-b diode of a RF SMD transistor can be used as a good noise source with ~30 dB ENR, for free. I used similar setup to measure sand moisture on sand moving on a conveyor belt as well as I built small radio telescopes with satellite LNBs; I use the SMD e-b diodes as calibration noise sources.

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Hi Jiripolivka,

The frequency range for my radiometer is between 10 to 12 GHz...please I need your help to design my radiometer...could you please tell me which type of radiometer (TPR, Dicke or correlation) did you design for moisture measurement... and did you simulate your radiometer in ADS?

Regards
Raed

I have developed a number of various radiometers, at 4, 11, 12 and 33 GHz, for various purposes. For demonstrations of solar radio noise and lunar noise (with 1-ft parabolic dishes), to study water emission from atmosphere, and to make industrial sensors of sand moisture.
For some applications like solar noise or sand moisture, the total-power radiometer circuit is good enough. To detect weaker noise temperatures, Dicke system was used, to stabilize the radiometer.
To measure sand moisture (and also wood planks, chips, rice, etc.), I have used the "active radiometry" principle I invented: a "probing signal" is generated from an electronic noise radiator towards the radiometer, and the tested object or sand stream is located between them. The insertion loss was found to correspond to sand moisture, and the use of the noise field effectively removed any interference, so the sand or other objects under test can move freely, e.g. on a conveyor.
To improve resolution and to increase the loss range I use a keyed noise source, and an active video filter after the radiometer; the antennas can be separated by > 1 ft while the detectable loss exceeds 20 dB. The radiated noise level is measured in picowatts, so there is no "dangerous" radiation, nor interference.

Added after 10 minutes:

To Raed-microwave:

If I understand well your project, you have a block of a dielectric material and you need to detect "hot spots" in it. In medicinal research we call such a structure "phantom". It is usually made from a gel simulating a human tissue, and the "hot spots" can be introduced by hot water flowing through a plastic tube (to not affect the microwave probing signal).
I have used 4 and 12 GHz radiometers in a similar situation. My radiometers used the Dicke principle, with mechanical attenuators chopping the input noise. I also developed a "matrix" scanner, with a mechanical waveguide switch. So I scanned the radiating temperature coming from various adjacent spots on phantom surface. By this I was able to resolve several Kelvins by my radiometers while the input matrix had to touch phantom surface for the best results (applicators).
The purpose of my experiments was to detect breast tumors but the success was limited due to the complexity and inherent loss in the living tissue. What seemed good in phantoms did not work in a real human sample.
Let me know what advice I can offer you for your project.