Many times the measured results of antenna matches with simulated but sometimes measured results do not match with simulated and sometimes measured results do not match at higher frequencies. Plz specify some causes of mismatching for both the conditions.
It is so that the simulation model is an approximation of the real structure. At lower frequencies the small deviations will have negligible effects on the electrical performance of the antenna while the same deviation has a greater effect on the performance. As an example, the resonance frequency at lower frequency will be less sensitive to the dimension tolerances and the parasitic effects.
It is the relative effects of fabrication tolerances at different frequencies.
Best wishes
When it doesn't match it is often because the model is not the same as the actual antenna. Differences such as at solder joints and line edges are more significant at higher frequencies. Circuit boards vary from each other in thickness and dielectric constant so the values used in simulation won't be quite the same as built, either.
Simulated results may vary slightly from reality, too, just because the solvers are not perfect, but they are much better than they used to be 40 years ago, and are not usually far off if the model is correct.
It is necessary to use a suitable method - time domain or frequency domain for instance - so that the solver can be used to its full accuracy and converge, and to use a fine enough mesh to get the currents accurate, but not too fine so that mathematical errors build up. All of these tend to give higher errors at higher frequencies.
firstly the substrate thickness and its permittivity may not be same as taken during the antenna designing in software tool. it may be different for different manufacturer also the permittivity may not be uniform throughout the substrate. this is main cause of mismatching in results. secondly antenna with larger dimension may cause very little mismatch as compare to smaller dimension. because small alteration in dimension would not shift the antenna disastrously. third, non calibrated testing equipment and the environment of testing is also affect the performance.
It is due to discontinuties present in the structure being simulated which are not considered while simulating
Dear Researcher Ashwini Kumar,
In the virtual model, I suggest that you import the connector model directly (manufacturer data) and insert it in your virtual simulation. It is main cause of mismatching in results in Very high frequency, Ultra high frequency and Super high frequency . I suggest you use CST, HFSS or FEKO in your simulation and refine the mesh. They have good results.
Hello Sir, Ashwini Kumar . It is mainly due to fabrication tolerances. as at high frequencies, size is very small of the order of 10mm or lesser. if there is a little bit variation in the parameters of the structure it results changes in S11. Sometimes proper matching of the feed line with the connector is not done and we face the variation in simulated and measured results.
in addition to connector and tolerance issues you may get reflections from the wall of the lab (and your body if you stand near by) unless you do the measurement in an anechoic chamber or really on the roof of some building to approach free space surroundings
It is so that the simulation model is an approximation of the real structure. At lower frequencies the small deviations will have negligible effects on the electrical performance of the antenna while the same deviation has a greater effect on the performance. As an example, the resonance frequency at lower frequency will be less sensitive to the dimension tolerances and the parasitic effects.
It is the relative effects of fabrication tolerances at different frequencies.
Best wishes
Dear Ashwini Kumar , it is a good question. What kind of antenna do you want to measure? Considering microstrips antenna, besides the suggestions given by the researcher Kenedy Marconi , I would suggest a characterization of the parameters of substrate used in the manufacturing of the antenna, as for example, the dielectric constant. Another possibility is to use a substrate with precise information given by the manufacturer.
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