Waveguide phase shifters are important RF and microwave circuit components widely used in radar, communications, and electronic warfare systems. Different waveguide phase shifter types can achieve electromagnetic wave phase adjustment to meet the needs of various application scenarios. This article will introduce several common types of waveguide phase shifter types and their working principles, and discuss their advantages and disadvantages.
Ferrite waveguide phase shifters are a type of phase shifter based on ferrite materials. Their working principle involves introducing a ferrite material into the waveguide and using an external magnetic field to change its magnetic permeability, thereby affecting the phase velocity of the electromagnetic wave and achieving phase shift. These phase shifters can be categorized into types such as circulator phase shifters, dual-mode phase shifters, and rotating field phase shifters.
Among them, the structure of the circulator ferrite phase shifter is relatively simple. It sets a ring-shaped ferrite in the center of the broad side of a rectangular waveguide with a magnetizing wire at the center. When a sufficiently large pulse current passes through the wire, the external magnetic field will cause the ferrite to saturate, generating different magnetic permeabilities, and ultimately achieving phase shift. Ferrite waveguide phase shifters have high power capacity and low insertion loss, making them suitable for passive phased array radar systems and other applications.
Despite their excellent performance in some fields, ferrite waveguide phase shifters are large in size and slow in response speed, making them unsuitable for high-speed millimeter-wave radar requirements. This is also the reason they are not suitable for airborne and spaceborne radar applications.
Semiconductor PIN diode waveguide phase shifters are a widely used type of digital phase shifter. This type of phase shifter mainly achieves phase shift by switching the PIN diode between forward and reverse bias states, thus realizing the connection or disconnection of the transmission line. Common circuit structures include switched-line phase shifters, loaded-line phase shifters, and reflection-type phase shifters.
PIN diode phase shifters have the primary advantages of fast working speed and easy adoption of digital signal control, making them especially suitable for application scenarios requiring rapid switching and precise control. However, this type of waveguide phase shifter has low power capacity and tends to produce insertion loss and resonance phenomena in high-frequency microwave ranges.
To address these issues, designers often optimize the structure of the phase shifter and the electrical length of the diode to reduce the impact of resonance. Additionally, although PIN diode waveguide phase shifters face some technical challenges during high-power transmission, their low cost and simple control still make them one of the commonly used waveguide phase shifter types.
With the development of microwave technology, gallium arsenide (GaAs) integrated circuit-based MMIC (Monolithic Microwave Integrated Circuit) waveguide phase shifters have gradually emerged. Gallium arsenide MMIC phase shifters exhibit excellent performance in the L-band, C-band, and other low-frequency microwave bands, making them particularly suitable for application scenarios requiring small size and high integration.
Gallium arsenide MMIC waveguide phase shifters typically adopt a reflective structure, achieving phase shift through the reflection transmission of microwave signals. Coupling lines generally use the form of microstrip lines or coplanar waveguides, where the distribution parameters of capacitance and inductance play a crucial role. Despite the higher insertion loss and limited power capacity in high-frequency microwave bands, their mature manufacturing process and strong temperature stability make them widely used in communication and microwave sensor fields.
RF MEMS (Radio Frequency Microelectromechanical Systems) phase shifters are a type of phase shifter based on MEMS technology, offering excellent performance like low loss and low power consumption. RF MEMS waveguide phase shifters achieve phase shift by changing the size of the loading capacitance in parallel with the transmission line, typically being digital phase shifters.
Different waveguide phase shifter types have their respective advantages in different application scenarios. By reasonably selecting and designing different waveguide phase shifter types, users can achieve optimal performance in specific application scenarios.