In modern microwave and millimeter-wave systems, especially in high-end applications such as phased array radar, satellite communications, and 5G/6G base stations, precise control of signal phase is crucial. As a fundamental passive component in waveguide transmission systems, the core function of a waveguide phase shifter is to precisely adjust the phase of electromagnetic waves without altering the signal amplitude. Crucially, these phase shifters rely entirely on physical structures rather than active devices like transistors or diodes for control, yet still achieve extremely high phase accuracy and stability.1. Phase Control Principle Based on Physical Path Length VariationWhen an electromagnetic wave propagates in a waveguide, its phase is proportional to the propagation path length. Waveguide phase shifters utilize this fundamental principle, changing the effective electrical length of the signal through mechanical or structural means to achieve phase shifting. Typical implementations include: movable metal diaphragms, sliding short-circuit pistons, rotating stepped impedance sections, or tunable screw arrays. For example, in reflective phase shifters, the round-trip path between the incident and reflected waves is altered by adjusting the position of the short-circuit path, resulting in a controllable phase shift. In transmission-type designs, discrete or continuous phase changes are achieved by inserting delay segments of different lengths or switching multi-path channels. Since these controls are based entirely on precise geometric changes and require no external power supply or semiconductor devices, they inherently possess high power tolerance and long-term stability.
