Managing Dielectric Loading Shifts in Encapsulated Dual Band Antenna Assemblies
Encapsulating dual band antennas requires pre-tuning trace geometry to offset lower band and upper band dielectric loading shifts before molding.
Cross Polarization Rejection
Meaning
Angular discrimination in dual-polarized antenna systems defines the ability of a transducer to separate signals based on their electromagnetic orientation. Higher cross polarization rejection ensures that a signal intended for a vertical port does not leak into the horizontal port of the same antenna. It is measured in decibels as the ratio of the co-polarized signal level to the cross-polarized signal level.
Antenna Isolation
Physical separation between orthogonal elements and the symmetry of the radiating structure determine the baseline performance of the device. Poor cross polarization rejection results in inter-symbol interference because the receiver cannot clearly distinguish between the two data streams. This is especially problematic in multiple-input multiple-output systems where spatial multiplexing relies on clean channel separation.
Interference Impact
Multipath propagation in dense urban environments can degrade the effective signal quality even if the antenna itself has high ratings. High levels of cross polarization rejection help maintain the integrity of the communication link by filtering out depolarized reflections that arrive from unintended angles. This allows for more stable modulation schemes and higher data throughput in challenging radio environments.
System Qualification
Verification of this metric occurs during the final assembly testing of a smart device inside an anechoic chamber. The cross polarization rejection must be measured across the entire operating frequency range because the isolation often drops at the edges of the band. Mounting the antenna near metallic enclosures or large batteries can distort the radiation pattern and measurably reduce the measured rejection levels compared to the datasheet of the standalone component.