Mitigating Board Noise Desense in Cellular Hardware Radiators
Mitigating board noise desense requires unbroken ground planes, filtered switching stages, and RF shielding cans to preserve receiver sensitivity margins.
Stripline Routing
Meaning
A printed circuit board trace embedded in an internal layer between two continuous reference planes provides superior electromagnetic shielding compared to surface microstrip traces. Employing stripline routing decreases radiated emissions and isolates sensitive signal traces from external rf noise. Layout engineers select this configuration to achieve controlled impedance and minimize crosstalk in high-density multi-layer boards, especially in the vicinity of sensitive radio frequency transceivers.
Signal Layering
Internal routing isolates signal currents from neighboring layers through the shielding effects of the reference planes. When executing stripline routing, the signal is sandwiched between two ground layers, preventing unwanted energy from escaping the board. This arrangement reduces the necessity for additional shield cans in space-constrained designs.
Impedance Control
Calculations for trace impedance depend on the distance between the signal trace and both reference planes. Layout software tools use these distances, along with the trace width and dielectric constant, to calculate the correct geometry for stripline routing. Maintaining a uniform trace width along the routing path avoids impedance mismatches and minimizes signal reflection.
Board Stackup
High-density circuit boards require careful planning of the layer allocation. The choice to use stripline routing increases the total layer count of the pcb stackup, which adds to the fabrication cost. However, the improved signal integrity and reduced emissions justify the additional expense for high-performance rf devices.