Electromagnetic Spectrum
Signals operating in the range of thirty to three hundred gigahertz provide high bandwidth for advanced communication and radar systems. At millimeter wave frequencies, the short wavelength requires extremely small and precise physical features on the circuit board. These signals are highly susceptible to atmospheric absorption and require line of sight for effective transmission.
Designers use specialized laminates with very low loss tangents to prevent the energy from being absorbed by the substrate.
Design Requirement
Transitions between different layers and the shape of the conductor traces must be optimized to prevent reflections and signal degradation. Working at millimeter wave frequencies necessitates the use of smooth copper foils to minimize the resistive losses caused by the skin effect. The dielectric thickness must be kept thin to avoid the propagation of unwanted modes in the transmission lines.
Automated optical inspection is performed to verify that every trace meets the strict dimensional tolerances required for these high energy signals.
Transmission Loss
Attenuation increases rapidly as the frequency rises, which limits the effective distance that the signal can travel without amplification. Managing the dielectric and conductor losses at millimeter wave frequencies is the primary challenge for hardware engineers. Circuit layouts are kept as compact as possible to reduce the length of the signal paths.
The performance of the final assembly is verified using high frequency probes and specialized test equipment that can handle the wide bandwidth of the signals.
