Measuring Polymer Radome Transmission Loss at Millimeter Wave Frequencies
Polymer radome transmission loss at mmWave frequencies depends on dielectric loss tangent and wall thickness precision to maintain regulatory EIRP compliance.
Quasi Optical Measurement
Meaning
High frequency electromagnetic waves behave similarly to light, which allows for the use of lenses and mirrors to manipulate signal paths. This technique of quasi optical measurement is used primarily in the millimeter wave and terahertz bands because waveguides or cables are too lossy. It enables the characterization of materials and antennas in a setup that mimics the free space environment.
Beam Steering
Corrugated horns and dielectric lenses focus the radio energy into a narrow beam that can be precisely directed. Within a quasi optical measurement system, the signal travels through the air and is reflected by curved surfaces to reach the receiver. This approach replaces the waveguides used in lower frequency bands and eliminates physical connectors that would introduce unwanted reflections.
The alignment of these optical components must be perfect to ensure the beam lands on the center of the detector.
Sample Characterization
Testing the properties of a new polymer involves placing a flat sheet of the material in the path of the focused beam. The quasi optical measurement setup records how much energy is reflected and how much is transmitted through the sample. By analyzing these values, a computer can calculate the complex permittivity and the loss tangent of the plastic.
This method is non-destructive and can handle samples of various sizes.
System Integration
Designers of radar modules use these measurements to verify the performance of the integrated package. Data from a quasi optical measurement confirms that the antenna gain and beamwidth meet the design targets before the unit is installed in a vehicle. The results are used to refine the software models of the radio environment.