Comparative Investigation of Spatial Filtering Techniques for Ground Plane Removal in PEC-Based Automotive Measurements

Experimental comparison of absorber and conductive floor automotive near field antenna measurement systems

“…Second, measuring the free-space response is often a requirement because, as shown in [6,7], it allows for a straightforward emulation of vehicle responses over any type of ground (eventually including PEC as shown in [7]). As shown in [9], the same any-ground emulations from measurement performed in PEC conditions are instead much more complex and, in many cases, they do not allow to properly approximate the wanted ground response. Nevertheless, it should also be pointed out that in some cases, the PEC response is directly considered a good approximation of some driving grounds, such as wet asphalts.…”

“…2 (bottom-center); performed in the lower frequency range (84-500 MHz). In this case, the raised measurements have been performed to verify if the expected deterioration of performance caused by the poor reflectivity of the 18-inch absorbers at lower frequencies can be improved by increasing the electrical separation of the vehicle from the ground and applying a spatial filtering in a post-processing step (see [9,13] for more details). Such raised measurements have not been performed above 500 MHz because of the well-established behavior of the 18-inch absorbers at such frequencies.…”

“…In this case, the interaction with the conductive floor is more evident with respect to the measurement performed at 210 MHz, resulting in a vertical pattern with a significant ripple. It should be noted that the interaction with a PEC floor can also be largely mitigated by applying a spatial filtering [9,13]. Such mitigation is more effective at higher frequencies (e.g.…”

“…The availability of the free-space response also enables easy emulation of car behaviors over realistic automotive floors with commercially available tools [6][7][8]. As described in [9], such emulations are more complex when a conductive ground is used, and such types of floors are a good approximation of realistic grounds (such as asphalts) only in a limited number of situations. Moreover, conductive ground measurements suffer from a relevant interaction between the conductive floor and the measurement system; thus, the quality of the measurements could be degraded, especially at lower frequencies.…”

“…For these reasons, they have been also included in this analysis. To deal with the poor reflectivity of the 18-inch absorbers at a lower frequency, the scaled measurements are also performed with the vehicle raised from the floor; spatial filtering [9,13] is then applied to measured data in post-processing to mitigate the effect of the interaction with the floor.…”