isolator and circulator are core passive devices developed based on the ferrite gyromagnetic effect in microwave RF systems, as well as key basic components for realizing unidirectional signal transmission, port electromagnetic isolation and microwave link voltage stabilization protection in microwave engineering. Different from low-frequency RF devices, isolators and circulators are specially designed for the high-frequency signal transmission characteristics of microwave frequency bands, adapting to microwave working frequency bands ranging from hundreds of megahertz to tens of gigahertz. They are widely used in core scenarios such as microwave communication, satellite transmission, radar detection, microwave testing and industrial microwave equipment, serving as essential devices to ensure the pure transmission of high-frequency signals, avoid link interference and improve the overall operational stability of microwave systems. From the perspective of microwave technology, the high-frequency transmission characteristics, microwave impedance matching, high-frequency loss characteristics and microwave anti-interference capability of the two types of devices directly determine the transmission efficiency and working accuracy of the entire microwave system, and act as the core basis for microwave circuit design, equipment selection and system commissioning.

　　From the perspective of microwave transmission principles, isolator and circulator rely on the anisotropic gyromagnetic properties of ferrite materials to break the bidirectional transmission law of conventional microwave devices and realize the directional transmission of microwave signals, which is their core advantage in adapting to high-frequency microwave working conditions. Microwave band signals feature short wavelength and extremely high frequency. During transmission, they are easily affected by load mutation, link mismatch and external electromagnetic clutter, resulting in signal reflection, waveform distortion, power oscillation and other problems. Ordinary passive devices cannot effectively block microwave-level reverse interference. As two-port microwave devices, isolators are mainly used for lossless forward transmission and thorough reverse isolation of microwave signals, which can accurately absorb reflected waves of microwave links and protect precision core components such as microwave power amplifiers and high-frequency transceiving chips. As three-port directional devices, circulators can complete the transceiving shunting and port isolation of microwave signals according to fixed circular logic, which is perfectly suitable for the integrated transceiving working requirements of microwave radar and dual-way microwave communication systems.

　　Microwave loss and high-frequency impedance matching are the core indicators for evaluating the microwave adaptation performance of isolator and circulator. High-frequency microwave signals are extremely sensitive to device insertion loss, and tiny loss will greatly reduce the radiation efficiency and transmission distance of microwave systems. Precisely calibrated for microwave frequency bands, high-quality isolators and circulators have ultra-low high-frequency insertion loss, which can maximize the retention of effective microwave signal power and avoid invalid loss of high-frequency energy. Meanwhile, the devices strictly follow the 50Ω standard impedance design for microwave systems with balanced impedance matching in the full microwave frequency band, which can eliminate common faults of microwave links such as high-frequency signal reflection, standing wave superposition and circuit self-excitation, and ensure complete microwave signal waveform and pure spectrum. Due to high-frequency process defects, ordinary devices are prone to sharply increased loss and impedance mismatch under microwave working conditions, which seriously damage the operational stability of microwave systems.

　　In microwave engineering applications, the high-frequency anti-interference capability and working condition adaptability of isolator and circulator are crucial. The electromagnetic environment of microwave scenarios is complex, and interleaved superposition of multi-band microwave signals easily causes adjacent-frequency interference and intermodulation interference. With excellent reverse isolation and directional transmission characteristics, isolators and circulators can accurately filter microwave clutter interference, realize electrical isolation between ports, and solve the problem of mutual interference between microwave transceiving signals. In addition, the devices have outstanding high-frequency power stability and temperature adaptability. Under the long-term high-frequency and high-power operating conditions of microwave equipment, the parameters have no obvious drift, which can continuously ensure the stable operation of microwave links and effectively reduce the failure probability and operation and maintenance costs of microwave equipment, making them indispensable core passive devices for various modern microwave systems.