Odd-Mode-Excited Tire-Wheel Assembly for Tire Pressure Monitoring Systems

A design methodology based on an odd-mode excited tire-wheel assembly is presented for tire pressure monitoring systems. The tire-wheel assembly is investigated using the finite-integration technique-based simulator CST Microwave Studio. Numerical investigations using a pair of electrically small dipoles inside the tire-wheel assembly show that the odd-mode excitation provides in-phase magnetic currents of standing waves along the angular direction on both sides of the tire-wheel assembly, resulting in the strong radiation in the plane normal to its axis. It is also shown that the odd-mode is excited by an electrically small loop antenna that has the aperture normal to the angular direction to enhance the magnetic coupling. The validity of the numerical investigations is confirmed by the measurements of a commercially available tire-wheel assembly at 434 MHz, where a loop antenna is installed into a transmitter. The effectiveness of the odd-mode excitation is numerically confirmed in a car body model having the tire-wheel assemblies rotated on the ground.