Multi-Band Mobile Antenna DeficienciesMobile antennas are available in many physical forms, and the designer enjoys a profession full of creative opportunities and challenges, recently accelerated by advancements in electromagnetic simulation/solution software. The designer virtually pursues their craft with apparent endless bounds. New challenges continue to load the development cycles, and keeping pace with new radio configurations can be overwhelming. Every new design includes trade-offs and compromises in performance. Realized gain, impedance match, directivity and aperture size typically limit optimized results. Optimization is often accomplished in narrow band antenna design, however when broad banding and multi-banding an antenna, the design criteria changes significantly. The antenna’s physical aperture must now support the required directivity and match efficiency for wider bandwidths and multi-frequency operation. Many times, the compromises are too great to achieve the required gain and system coverage, resulting in significant performance degradation. Impedance mismatches in the form of high input VSWR and poor directivity in the radiation pattern are direct results of these broadband/multi-band antenna designs, attempting to solve the radio OEM’s system requirements. Of course, all of this has to be integrated to include many types of installations with varying vehicle sizes presenting a multitude of ground plane configurations.
Most antenna manufacturers are clearly aware of these highly compromised designs, and continue their pursuit to resolve the inherent design deficiencies. Rest assured, there will come a time when mature, sophisticated design solutions will be available. However, while this evolutionary process unfolds, first responders and safety forces require immediate solutions to provide efficient interoperable coverage with their various wide band and multi-band systems currently being deployed.
Duplexed Antenna SolutionsTo meet the immediate system coverage requirements, E/M Wave is providing an efficient, fundamental solution incorporating a highly efficient, low insertion loss duplexer, EM-MBD41000-NJ. A duplexed configuration provides full duplex operation (transmit and receive) for two or more operational bands by splitting the signal between VHF and UHF/700-800 MHz bands. The duplexer augments splitting a single radio output into two separate channels, feeding two independently located antennas, with desired directivity and VSWR match. Each antenna can be chosen as a wide or narrow band type, required by the RF system with the key advantage of providing efficient single band performance with high directivity and gain. The antenna performance is critical to achieving the total RF system performance, and by incorporating a low insertion loss, wide band, high isolation duplexer, system engineers can now move forward to provide reliable, high performance wireless communications within statewide, multi-state or larger territorial coverage regions. Additionally, E/M Wave provides a full tri-band solution using the EM-MBD41000-NJ duplexer. A typical tri-band mobile antenna system is accomplished by incorporating the EMFLX-M10008-WB Wide Band VHF antenna on the VHF output port and the dual band EM-M22001 UHF/700-800 MHz on the UHF/700-800 MHz port. This configuration accommodates simultaneous operation for 144-174/450-520/746-870 MHz systems. Additional duplexed antenna configurations are available from E/M Wave, and can be referenced within the attached duplexer antenna configuration matrix.
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