1. Bandpass Filtering
The diplexer typically consists of two bandpass filters: one for the transmit (Tx) frequency band (e.g., 435-455MHz) and another for the receive (Rx) frequency band (e.g., 460-480MHz). These bandpass filters allow signals within their respective frequency ranges to pass through while attenuating signals outside these bands. This effectively isolates the transmit and receive signals, preventing interference between them. For example, a diplexer may achieve isolation of 30 dB or higher between its low and high ports, which is sufficient for most applications.

2. High Isolation Design
Cavity filters are commonly used in cavity diplexers due to their high Q factor and excellent selectivity. These filters provide high isolation between the two frequency bands, minimizing signal leakage from the transmit band to the receive band and vice versa. High isolation reduces the risk of interference between the transmit and receive signals, ensuring stable communication system operation. Some diplexer designs, such as high-rejection cavity duplexers, can achieve very high isolation levels. For instance, a high-rejection cavity diplexer can provide isolation levels of 80 dB or higher, effectively suppressing interference.

3. Impedance Matching
The diplexer incorporates impedance matching networks to ensure good impedance matching between the transmit and receive channels and the antenna or transmission line. Proper impedance matching reduces signal reflections and standing waves, thereby minimizing interference caused by reflected signals. For example, the diplexer's common junction is designed to achieve excellent impedance matching, ensuring that the input impedance at the transmit frequency is 50 ohms while presenting a high impedance at the receive frequency.

4. Space Segmentation
In co-site communication systems, diplexers can be combined with other techniques such as antenna directionality, cross-polarization, and transmit beamforming to achieve further suppression of signal interference in the propagation domain. For instance, using directional antennas in conjunction with diplexers can enhance isolation between the transmit and receive antennas, reducing the likelihood of mutual interference.

5. Compact Structure
Cavity diplexers feature a compact structure, allowing them to be integrated with antennas or other components. This integration reduces the overall system size and complexity while minimizing interference risks. For example, some diplexer designs incorporate filtering capabilities into the common junction, simplifying the structure while maintaining high performance.

The 435-455MHz/460-480MHz Cavity Diplexer employs bandpass filtering, high isolation design, impedance matching, space segmentation, and other technologies to effectively handle signal interference in LMR systems. This ensures that the transmit and receive signals operate independently without mutual interference, improving the reliability and stability of communication systems.