Enhancing Signal Integrity: Pass Notch Duplexers Demystified
Pass notch duplexers play a critical role in maintaining signal integrity within radio systems. Their primary function is to provide sufficient rejection of transmitter wideband noise and carrier signals to prevent desensitization of associated receivers. However, their effectiveness can vary depending on the specific configuration and presence of collocated transmitters and receivers. For instance, a standard pass notch duplexer may not offer sufficient isolation if there are other in-band transmitters or receivers nearby. In such cases, additional filtering may be necessary to safeguard both the repeater and other devices from interference.
Consider this: A pass notch duplexer passing 156.510 and notching its associated RX frequency of 154.710 is going to provide at best about 10 dB rejection at 156.090. This necessitates at least 75 dB decoupling between the repeater antenna and a collocated antenna to suppress transmitter wideband noise effectively. If not, then additional filtering is needed in the duplexer to protect a receiver from transmitter wide band noise.
Similarly, a pass notch duplexer that’s passing 156.090 and rejecting 156.390 will provide about 55 dB of rejection at 156.510. Here, about 30 dB decoupling between antennas or additional filtering is needed.
While pass notch duplexers are designed to protect associated receivers from their transmitters, any rejection of collocated transmitters or receivers is incidental. Comprehensive information, including antenna decoupling, is vital to assess desensitization accurately. Pass notch duplexers continue to serve as a crucial component in radio systems, but their effectiveness relies heavily on careful consideration of surrounding frequencies and potential interference sources. At EMR, we prioritize meticulous consideration of these factors. Our tailored solutions not only address standard requirements but also account for unique scenarios, ensuring optimal performance and reliability for our customers.
