Executing Class Two Permissive Changes for Substituted Host Antennas
Substituted host antennas qualify for Class II Permissive Changes only when peak gain stays below certified limits and radiative physical structure remains identical.
Peak Directivity
Meaning
Maximum ratio of the radiation intensity in a given direction to the average radiation intensity is measured across all directions. Peak directivity measures the ability of an antenna to concentrate its emitted energy into a narrow beam rather than spreading it equally in a sphere. This value is calculated at the specific orientation where the signal is strongest, providing a benchmark for the antenna’s efficiency in point-to-point communication.
It is a fundamental parameter for link budget analysis in satellite and long-range radio systems.
Antenna Geometry
Physical design and the arrangement of radiating elements determine how sharply the signal is focused. High peak directivity is achieved through the use of parabolic dishes or phased arrays that align the phase of the electromagnetic waves. If the geometry is altered by even a few millimeters, the focus of the beam shifts.
This sensitivity requires precise manufacturing tolerances for the antenna housing and its mounting brackets.
System Integration
Orientation of the device within its final enclosure affects the usable signal strength for the end application. Engineers optimize the peak directivity to ensure the radio energy is directed away from the user and toward the receiver. In smart devices, this often involves placing the antenna on the edge of the board to minimize the shadow cast by the battery.
When the peak directivity is too low, the device requires more power to maintain a stable connection, which drains the battery faster.
Comparative Calculation
Relationship between this value and the total gain includes the losses within the antenna structure itself. While peak directivity describes the concentration of energy, the actual gain accounts for the efficiency of the material and the connectors. A high directivity value does not guarantee a strong signal if the internal resistance of the antenna is high.
Designers use both figures to determine if the selected antenna is suitable for the target range of the product. These calculations prevent the overestimation of link stability in real-world deployments.