Replacing traditional duplexers with circulator and filter combination schemes is an advanced RF transceiver isolation optimization technology, widely used in high-performance communication and radar transceiver systems. Traditional integrated duplexers integrate transmitting and receiving filtering functions in a single device, with the advantages of simple structure and low cost, but have inherent limitations such as poor out-of-band suppression, narrow isolation bandwidth, and poor anti-interference ability. The circulator-filter combo scheme separates the transceiver isolation and frequency filtering functions, using the unidirectional transmission characteristic of the circulator to realize transceiver signal isolation, and using high-performance filters to complete precise frequency screening, achieving better transceiver isolation and anti-interference performance than traditional duplexers.

The core working principle of the combo scheme relies on the non-reciprocal transmission characteristics of RF circulators. The circulator can control the unidirectional flow of RF signals, isolating high-power transmitting signals from low-power receiving signals and preventing transmitting signal leakage from interfering with the receiving link. The matched high-performance band-pass or band-stop filters further filter out out-of-band clutter, harmonic interference, and spurious signals in the transmitting and receiving links, purifying the signal spectrum. The separated structural design enables the circulator and filter to be independently optimized for performance, breaking the performance bottleneck of integrated duplexers in wideband, high-isolation, and low-insertion-loss scenarios.

This replacement scheme has significant performance advantages in high-sensitivity transceiver systems. It can achieve higher transceiver isolation (exceeding 60dB) and wider operating bandwidth, effectively solving the problem of receiver sensitivity degradation caused by transmitter signal leakage. In addition, the combo scheme has stronger adaptability to multi-band and wideband systems, and can flexibly match filters of different frequency bands according to system requirements. Although the modular combination structure has a slightly larger volume and higher cost than integrated duplexers, its excellent performance and adjustable flexibility make it the mainstream solution for high-end 5G base stations, aerospace transceivers, and precision radar systems, gradually replacing traditional duplexer applications in high-performance scenarios.