I am a research scholar, working on wearable antenna design for wireless and biomedical application. I have 2 questions.
1. simulations are being done for some designs and obtaing gain less than 7dB for all my designs(slotted patch with partial ground plane). In on-body scenario, this simulated 7dB may decrease. so i want to know the value of gain in practical wearable environment (especially in WBANs).
2. In some cases, i am getting -ve gain and directivity or -ve value for radiation efficiency with good S11 value (-30 to -40dB). I unable to find the solution for this. Here, substrate material is polyimide.
Dear Nageswara RAO Regulagadda
Your antenna must satisfy the following requirements:
It must be low loss such that you achieve the highest loss efficiency
It must radiate in the half space out of the body
So, you have to close the ground plane to suppress the radiation in the direction of the body.
So, you have to the suitable material to avoid the polarization loss in the material.
If you display your S11 curve one can see how far your material is lossy!
Best wishes
What the dielectric constant value for polyamide as used in patch antenna.
Dear Nageswara RAO Regulagadda
Your antenna must satisfy the following requirements:
It must be low loss such that you achieve the highest loss efficiency
It must radiate in the half space out of the body
So, you have to close the ground plane to suppress the radiation in the direction of the body.
So, you have to the suitable material to avoid the polarization loss in the material.
If you display your S11 curve one can see how far your material is lossy!
Best wishes
Hi Nageswara,
Based on my understanding and experience:
1. A 7dB gain antenna, which should be a directional antenna, can not bring back the same when you make the sample, it is also possible you have read the peak gain, or directivity, fo to check realized gain at the specified frequency point you want. if not a directional out word the body, I am afraid if you get back gain similar to dipole that will be a bonus. When you put this antenna on the human body or tissue, no matter it is homogenous or voxel the performance drops a lot. for omnidirectional and on Body if you get back 0 dB gain, it would be cool. if directional getting 2 dB is good, however, this is not a standard.
2. Human body is a lossy medium, when loss added to the substrate loss no matter what substrate you are using, the body tissue helps in impedance matching, this means, the return loss value really makes you happy, However, the lossy body is a good absorber, and it is expected to get - value for Gain, directivity, and efficiency less 10% total one. if it is a directional antenna and the design is good, you may get around 20 % radiation efficiency. good luck
FR4 epoxy in one case and got the directional pattern and in another the dielectric is Rogers/RT duroid 5880 with thickness 1.6mm
@Nageswara RAO Rengulagadda.
For Wearable purposes you need to have dielectric that are flexible in operation for body loading. The hard substrates are not compatible for Wearable applications.
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