As a common type of wireless communication antenna, the directivity of a glue stick external antenna directly affects its signal coverage and anti-interference capability. Optimizing directivity through structural design requires consideration of five dimensions: conductor rod shape, ground plane layout, introduction of parasitic elements, multi-band compatibility design, and environmental adaptability adjustments. These designs must balance electromagnetic theory and practical engineering constraints to achieve a balance between directivity and practicality.
The shape design of the conductor rod is the core of directivity optimization. Traditional glue stick external antennas often use a straight rod structure, with an omnidirectional or weakly directive radiation pattern, suitable for basic communication scenarios. To enhance gain in a specific direction, the conductor rod can be designed as a spiral or polygonal shape. A spiral structure alters the current path, causing radiated energy to superimpose in a specific direction, forming directional radiation; a polygonal structure adjusts the current phase in segments to reshape the radiation pattern. For example, in industrial IoT scenarios, devices with strong directional transmission requirements often use spiral glue stick external antennas, whose directivity improves signal penetration in the target area and reduces multipath interference.
The ground plane layout has a significant impact on directivity. The ground plane, serving as the reference point for the glue stick external antenna, directly influences the shape and size of its radiation pattern. Traditional glue stick external antennas often rely on the device casing or PCB board as the ground plane, but the limited area of such ground planes easily leads to pattern distortion. Optimization solutions include expanding the ground plane area or employing special shape designs. For example, in vehicle communication equipment, combining the glue stick external antenna with the metal roof of the vehicle, using the roof as an extended ground plane, can create vertical directional radiation, enhancing signal propagation between buildings. In portable devices, designing a ring or fan-shaped ground plane can adjust the horizontal directivity, adapting to complex indoor environments.
The introduction of parasitic elements is an advanced technique for improving directivity. Parasitic elements refer to conductor structures that are not directly fed; by coupling with the main radiator, they alter the current distribution, thereby adjusting the radiation pattern. For example, adding parasitic patches to the top or bottom of a glue stick external antenna can optimize directivity for dual or multi-band frequencies; adding parasitic elements to the sides of the glue stick external antenna can shape the radiation pattern, such as enhancing forward gain or suppressing backward radiation. This type of design is common in base station glue stick external antennas and military communication equipment. Through the collaborative work of multiple parasitic elements, precise coverage in complex environments can be achieved.
Multi-band compatible designs must consider both directivity and frequency band characteristics. Modern communication equipment often needs to support multiple frequency bands, such as 2.4GHz and 5GHz for Wi-Fi, and Sub-6GHz and millimeter waves for 4G/5G. The wavelength differences between different frequency bands lead to different directivity optimization strategies. For example, low-frequency bands require larger structures to achieve directional radiation, while high-frequency bands can achieve similar effects through miniaturization. Multi-band compatible designs for glue stick external antennas often employ stacked or nested structures, integrating radiators of different frequency bands onto the same carrier. Frequency bands are separated by frequency selective surfaces or filtering structures, and then the directivity of each band is optimized separately. For example, in industrial routers, dual-band glue stick external antennas, through a high- and low-frequency band separation design, can simultaneously achieve omnidirectional coverage at 2.4GHz and directional enhancement at 5GHz.
Environmental adaptability adjustment is a practical extension of directional optimization. In actual use, the directionality of glue stick external antennas is significantly affected by installation location, surrounding objects, and environmental factors. For example, metal objects near the glue stick external antenna can cause radiation pattern distortion, and high-temperature environments may alter material properties and affect performance. Optimization solutions include adopting adjustable directional designs, such as adjusting the angle of the glue stick external antenna through mechanical structures or switching different directional modes through electronic switches; and using environmentally resistant materials and protective structures, such as high-temperature resistant plastics and waterproof coatings, to ensure stable directionality in harsh environments. For example, in outdoor monitoring equipment, rotatable glue stick external antennas are used, with remote control adjustment of direction to adapt to different monitoring scenario requirements.
