Novel Ultra-Compact Quad-Channel Diplexer Using Divided Microstrip Coupled Lines for IoT, Multi-Service Wireless, and 5G Networks

The rapid expansion of the Internet of Things (IoT) necessitates advanced communication
technologies that can efficiently manage diverse frequency requirements and ensure reliable connectivity
across various applications. This paper presents the design and analysis of a microstrip 4-channel diplexer
with resonance frequencies of 700 MHz, 1.39 GHz, 2.366 GHz, and 2.9 GHz. Strategically designed to
support low-power wide-area networks (LPWAN), smart device connectivity, and high-speed data transfer,
this versatile diplexer addresses the critical demands of modern wireless communication systems in sectors
such as smart cities, healthcare, and industrial automation. The innovative quad-band diplexer achieves
remarkably Minimal insertion losses of 0.52 dB, 0.14 dB, 0.33 dB, and 0.15 dB across its four passbands,
along with enhanced harmonic suppression for superior signal integrity and reduced interference. Its ultracompact structure, measuring only 0.0028λg², allows for easy integration into space-constrained
environments. The use of novel, divided microstrip coupled lines significantly enhances performance while
minimizing size, indicating that this diplexer can greatly improve the efficiency and reliability of wireless
communication systems, paving the way for advanced multi-band operations and meeting the demands of
modern multi-service and 5G networks.