Open AccessArticle 3D Coverage Shaping of an On-Glass 5G NR N78 Monopole Using Open/Short-Circuited Stubs by Fei-Lung Wu Fei-Lung Wu SciProfiles Scilit Preprints.org Google Scholar Fei-Lung Wu was born in Taichung, Taiwan, on September 25, 1978. He received his B.S. degree in from [...] Read more 1, Jung-Sheng Liu Jung-Sheng Liu SciProfiles Scilit Preprints.org Google Scholar 1,*, Chia-Mei Peng Chia-Mei Peng SciProfiles Scilit Preprints.org Google Scholar 2, Li-Wei Kao Li-Wei Kao SciProfiles Scilit Preprints.org Google Scholar 2, Pei-Hsuan Ko Pei-Hsuan Ko SciProfiles Scilit Preprints.org Google Scholar 2 and I-Fong Chen I-Fong Chen SciProfiles Scilit Preprints.org Google Scholar 3 1 Ph.D. Program of Electrical and Communications Engineering, Feng Chia University, Taichung City 407102, Taiwan 2 Department of Communications Engineering, Feng Chia University, Taichung City 407102, Taiwan 3 Department of Information and Communication, JinWen University of Science & Technology, New Taipei City 231055, Taiwan * Author to whom correspondence should be addressed. Electronics 2026, 15(12), 2543; https://doi.org/10.3390/electronics15122543 (registering DOI) Submission received: 26 April 2026 / Revised: 31 May 2026 / Accepted: 1 June 2026 / Published: 9 June 2026 Abstract This paper presents a compact modified monopole antenna tailored for 5G NR on-glass automotive applications operating in the n78 band. The design overcomes 3D radiation pattern limitations inherent in conventional monopole and inverted-F antennas (IFAs). Unlike traditional structures where auxiliary branches serve impedance matching or grounding, this design integrates open- and short-circuited stubs with a coplanar waveguide (CPW) feed to eliminate discrete components. By utilizing a resonant mechanism distinct from IFAs, it enables precise control over the current distribution and phase on the radiator to achieve passive 3D beam shaping without active switches or arrays. This suppresses the inherent elevation null, enhancing upper-hemisphere radiation. A prototype operating from 3.3 to 3.6 GHz was fabricated on a flexible printed circuit (FPC) and verified on a glass substrate. This study focuses strictly on radiation characteristics at the antenna element level; to ensure a focused investigation on dielectric-antenna interactions, large-scale vehicle body scattering and full-scale vehicle integration are excluded from this scope. The results, including S-parameters, gain, total efficiency, and 3D patterns, demonstrate superior elevation coverage and comparable impedance performance under on-glass boundary conditions. The proposed methodology offers a high-feasibility, low-complexity, and cost-effective solution for passive 3D radiation control in on-glass 5G wireless links. 1. Introduction Recently, advanced radiation synthesis and aperture-field engineering techniques have been investigated to control electromagnetic wavefronts [ 22, 23]. For instance, the 3D-printed multi-faced metasurface metadevice reported in [ 22] utilizes a multi-layer transmissive birefringent co-polarized meta-atom framework to establish space-polarization wavefront control, generating highly directive beams with peak gains up to 13.5 dBi at 11.3 GHz. Concurrently, the low-profile ultrawideband antipodal Vivaldi antenna (AVA) array in [ 23] leverages element edge overlapping and shorted pin loading to achieve a broad broadside scanning range with peak gains scaling up to 18 dBi from 0.9 to 12 GHz. However, these advanced architectures require voluminous multi-faced geometries or dense multi-element array matrices with intricate feed networks, which are incompatible with thin-film lamination on automotive window glass where driver visibility and low profile are critical. Alternatively, simplified passive planar options using coupled parasitic patches [ 24] or arc-shaped defected ground structures (DGSs) [ 25] have been explored to enhance matching bandwidth across multi-bands. Nevertheless, these traditional planar antennas fundamentally retain the conventional omnidirectional radiation profile and fail to suppress the deep elevation null along the vertical direction. Consequently, developing a structurally simple, completely passive solution that shapes the 3D radiation volume to fill the axial blind spot remains a significant challenge. To address these requirements, this paper proposes a compact modified monopole antenna operating in the 5G NR n78 band, optimized for flexible printed circuit (FPC) lamination on automotive glass. Unlike traditional IFA-derived structures where auxiliary stubs serve as grounding lines, the proposed design treats the integrated open/short-circuited stubs as a distributed sub-wavelength reactive loading network. This mechanism perturbs the boundary current phase distribution to achieve passive 3D coverage shaping and suppress the vertical null, effectively replacing complex active electronic reconfiguration. To validate the configuration, an FPC prototype was fabricated and verified via Advanced Design System (ADS) circuit model analysis, full-wave electromagnetic simulations, and anechoic chamber measurements. The main contributions of this work are summarized as follows: A passive 3D coverage shaping technique for on-glass monopole antennas using open- and short-circuited stub loading to fill the traditional vertical blind spot. A quantitative lumped-element equivalent circuit interpretation that models the distributed reactive loading mechanism, distinguishing it from conventional IFA resonance. Experimental confirmation of controllable radiation pattern tuning and upper-hemisphere gain enhancement without relying on active components, arrays, or switches. A comprehensive benchmark analysis against state-of-the-art reconfigurable and passive configurations to highlight the design’s structural simplicity and coverage efficiency. 2. Antenna Configuration and Current-Path Analysis 2.1. Antenna Configuration and Equivalent Circuit Model The antenna architecture proposed in this paper is improved from a traditional monopole antenna, as shown in Figure 1a. It is designed to be implemented on an FPC for automotive glass installation. Furthermore, the proposed FPC antenna can be surface-mounted onto the automotive glass by employing either an optically clear adhesive (OCA) film layer commonly used in automotive window electronics, or a laminated dielectric adhesive layer standard in vehicular electronic modules. This design provides comprehensive 3D radiation coverage. The new-type antenna configuration is illustrated in Figure 1b. The optimized geometrical dimensions of the new-type antenna are summarized in Table 1. The height of the coplanar waveguide (CPW) feed is reduced from 21.25 mm to 15 mm. Meanwhile, the CPW spacing is adjusted, and one open-ended stub together with two short-circuited stubs, each with a width of 1 mm, is introduced. The monopole radiator width is also reduced from 14.4 mm to 7.2 mm, achieving a 50% size reduction. The resonant length of the antenna is determined by the total length of segments B + D. By reducing the radiator width from 14.4 mm to 7.2 mm, the antenna size is further miniaturized by 50% while maintaining operation within the 3.3 to 3.6 GHz band (|S11| ≤ −10 dB). The two short-circuited stubs, denoted as E and H, serve as key design parameters for impedance matching at the target frequency and for shaping the 3D radiation distribution. The CPW grounding areas are defined as K × I and K × N. In addition, the CPW gap is optimized in conjunction with one open-ended stub and two short-circuited stubs to achieve the target impedance bandwidth. The SMA connector employed in this work is only used for laboratory characterization. In practical applications, the antenna can instead be connected through flexible coaxial cables, embedded CPW feed lines, or conductive spring-contact structures integrated into the vehicle body. The proposed antenna design is intended for mounting on flexible printed circuit boards (FPC) on automotive glass. To theoretically validate this physical mechanism, the equivalent circuit model of the reference monopole is initially synthesized using lumped (RLC) elements, as shown in Figure 2a; Advanced Design System (ADS 2024 update 2.0) software is employed to optimize these lumped values, centering the primary resonance at 3.5 GHz. Physically, the inductive components (L) govern the resonant frequency offset, whereas the capacitive elements (C) dictate the impedance matching bandwidth. The verified circuit-level reflection coefficient S11 frequency response is illustrated in Figure 2b. Derived from a modified monopole configuration, the core mechanism of the proposed architecture relies on manipulating the surface current path via short-circuited stub parameters (G and H) to shape the 3D spatial radiation profile. To quantitatively validate this physical interpretation, the simplified circuit model of the classical monopole evolved into a distributed-loading circuit network representing the new antenna architecture, as shown in Figure 3a. The introduced open/shorted reactive paths are implemented via a shunt inductor (L) connected in parallel at the terminal boundary of the monopole impedance branch. The resulting ADS simulation response, shown in Figure 3b, demonstrates an excellent impedance matching profile centered at 3.5 GHz (|S11| ≤ −10 dB), which tightly aligns with the target design specifications. 2.2. Simulation Analysis Rather than relying on traditional resonance mode formation, the proposed antenna utilizes passive current path engineering. In contrast to conventional IFAs that radiate via a λ/4 resonance path established by the ground return loop, this architecture replaces the dependency on a singular dominant resonant pathway between the radiator and the ground. Instead, the introduced open- and short-circuited stubs function as distributed reactive loading elements that perturb both the amplitude and phase of currents in the vicinity of the feed and ground edges. Specifically, the short-circuited stubs (E and H) provide localized low-impedance paths that divert a portion of the return current from the CPW ground edges, forming multiple secondary current loops rather than a single dominant path. While the introduced stubs also contribute to impedance matching, an important role in this design is to influence current distribution and phase for radiation shaping. Meanwhile, the open-circuited stub behaves as a capacitive/inductive reactive element depending on its electrical length relative to the operating wavelength, contributing to phase compensation in the current distribution. When properly tuned (approximately sub-wavelength regime), these elements introduce controlled phase offsets between currents flowing on the monopole arm and those on adjacent ground boundaries. This phase perturbation can be interpreted as a shift in the effective current phase distribution along the radiator–ground system, which directly influences the far-field superposition pattern. As a result, the radiated fields from different current paths no longer combine symmetrically as in a conventional monopole. Instead, constructive and destructive interference occurs in specific elevation regions, leading to suppression of the intrinsic elevation null and redistribution of radiation toward the upper hemisphere. This mechanism can be interpreted as a passive spatial mode redistribution rather than simple impedance tuning. The simulated surface current distribution at 3.5 GHz as shown in Figure 4 confirms that the current is no longer concentrated along a single monopole axis but is distributed across the feed region, stubs, and ground edges with comparable magnitude. This distributed current network reduces feed-dominant radiation and enables more effective utilization of the surrounding conductive structure as part of the radiating aperture. Consequently, the observed gain enhancement is not solely due to improved impedance matching, but also due to increased effective radiating aperture and constructive field superposition in the desired spatial region. This explains the improved elevation radiation characteristics and higher realized gain compared to the reference monopole. Therefore, this behavior can be interpreted using transmission-line theory, where open- and short-circuited stubs introduce frequency-dependent reactive loading that modifies the local current phase and amplitude distribution. Table 2 presents a comparison of the simulated antenna gains of the reference monopole antenna and the new-type antenna at 3.5 GHz. After optimization, the new-type antenna achieves a simulated peak realized gain of 6.35 dBi, whereas the conventional monopole antenna exhibits 1.54 dBi, indicating a notable enhancement with redistributed radiation in the target band. From the frequency-dependent gain curves, the new-type antenna demonstrates a higher and more stable gain performance within 3.3 to 3.6 GHz, consistent with the design objective. Figure 4 illustrates the surface current distribution of the proposed antenna at 3.5 GHz. The simulation results indicate that the optimized design yields a more distributed current pattern around the feed and stub region, and both the radiation patterns and gain curves agree with the coverage shaping objective, thereby validating the effectiveness of the proposed approach. As shown in Figure 5, the reference monopole antenna’s adjacent operating bandwidths are approximately 0.49 GHz (3.19 to 3.68 GHz). By contrast, the new-type antenna exhibits a bandwidth of 0.66 GHz (3.14 to 3.8 GHz), a resonant frequency of 3.47 GHz, and a fractional bandwidth of 19%. The gray-shaded region in Figure 5 indicates the target 5G NR n78 operating band (3.3 to 3.6 GHz). The 3D radiation pattern of the reference monopole antenna exhibits a typical omnidirectional pattern with an elevation null, as shown in Figure 6. By contrast, the new-type antenna demonstrates a modified 3D radiation distribution, where the radiation toward the upper hemisphere is enhanced and the elevation null is mitigated. This characteristic aligns with on-glass vehicular installation, where stable upper-hemisphere coverage can be more beneficial than an idealized free-space omnidirectional pattern. 3. Measurement Results and Discussion 3.1. Measurement Setup |S 11| measurements were performed using a Keysight E5071C vector network analyzer (Keysight Technologies, Santa Rosa, CA, USA) based on the standard SOLT calibration procedure. Since the SMA to CPW conversion was already included in the actual feed structure, no additional de-embedding was performed. Radiation pattern measurements were conducted under far-field conditions in an ETS-Lindgren AMS-8500 OTA chamber (ETS-Lindgren, Cedar Park, TX, USA), as shown in Figure 7. To minimize the impact of cable radiation, spatial loss corrections were applied to the OTA anechoic chamber during measurements, including all connecting cables (e.g., SMA connectors and coaxial cables) and infrared laser alignment techniques. 3.2. Comparison of Simulated and Measured |S 11| The results of the new-type antenna fabricated prototype are shown in Figure 8. The measured results indicate that the operating band covers the gray-shaded region in Figure 8 indicates the target 5G NR n78 operating band (3.3 to 3.6 GHz), and the measured bandwidth exceeds the target bandwidth, extending to approximately 4.11 GHz. Although a slight ripple approaching −10 dB appears within the band, the measured |S 11| remains close to or below −10 dB. Compared with the simulated results, the measured |S 11| exhibits slightly degraded matching performance; nevertheless, the measured resonance frequencies are within the desired range of 3.3 to 3.6 GHz. 3.3. Comparison of Simulated and Measured 2D/3D Radiation Patterns For vehicle communication requirements, the radiation objective is not only impedance matching but also reliable upper-hemisphere coverage, since practical links to roadside units and base stations typically require usable radiation over a broad range of elevation angles. A classical monopole exhibits an omnidirectional azimuth pattern but often suffers from a pronounced elevation null along the vertical direction; this may result in coverage blind spots during actual transmission. To quantitatively characterize the proposed coverage shaping, we evaluate the 3D patterns using coverage-relevant metrics in addition to peak gain, including: (i) the elevation null depth (minimum realized gain within the elevation sector of interest), (ii) the main-lobe elevation tilt (peak direction in elevation), (iii) the half-power beam width (HPBW) in elevation, and (iv) the front-to-back ratio (F/B) for the dominant elevation lobe. At 3.5 GHz, the reference monopole shows a deep null around the vertical direction, whereas the proposed shorting-path-assisted structure noticeably mitigates this null and redistributes radiation toward the upper hemisphere. Specifically, the elevation null depth is significantly reduced, and the gain level in the upper hemisphere is improved compared to the reference monopole. These changes indicate that the proposed design transforms the inherent elevation null characteristic of traditional monopole antennas into a 3D radiation pattern more favorable for coverage, making it highly feasible for automotive glass installation. To explicitly demonstrate these improvements, a comprehensive quantitative comparison between the reference monopole and the new-type configuration is summarized in Table 3. As presented in Table 3, the reference monopole exhibits a severe radiation blind spot along its vertical axis (θ = 0 deg), where the realized gain degrades to approximately −15.2 dBi due to the nulling effect of the axial current distribution. In stark contrast, by introducing the optimized open/short-circuited stub configuration (measured in the directional mode), the upward radiation is substantially reinforced. The measured realized gain at θ = 0 deg increases dramatically to 1.35 dBi, achieving a quantifiable elevation null depth reduction of 16.55 dB compared to the reference baseline. Furthermore, the HPBW is successfully expanded from 60° to approximately 115°, effectively filling the traditional axial blind spot. In addition to pattern shape, realized gain and efficiency should be interpreted together. The new-type antenna achieves a measured peak realized gain of 4.99 dBi at 3.5 GHz in Table 4, and the corresponding total efficiency is 44.1% as shown in Table 5. Such efficiency levels are within a reasonable range for compact on-glass antennas, where dielectric loss and installation constraints typically limit radiation efficiency. This suggests that the observed gain enhancement is primarily associated with radiation redistribution (increased directivity toward desired elevation angles) rather than a purely efficiency-driven improvement. The difference between simulated and measured gain is mainly due to practical losses and measurement setup limitations; however, both results consistently demonstrate the same trend of improved elevation coverage. Such a coverage-oriented trade-off in the FPC design is justifiable for vehicle-to-everything (V2X) scenarios, as reducing elevation nulls to stabilize link performance takes precedence over achieving peak omnidirectionality. Overall, the consistent agreement between measured and simulated 3D radiation patterns confirms that the proposed compact modified monopole structure provides a practical solution for upper-hemisphere coverage shaping in 5G NR n78 automotive antennas. The radiation pattern reported in some on-glass monopole literature is typically omnidirectional. However, considering installation on automotive window glass, a coverage-shaped radiation distribution that reduces elevation nulls can be more suitable. Figure 9 compares the simulated and measured 3D radiation patterns. The new-type antenna exhibits a bidirectional characteristic in the elevation plane and compensates for the classical monopole’s elevation null. To provide a more detailed evaluation of the radiation characteristics, the simulated and measured 2D radiation patterns in the principal planes (the E-plane and H-plane) at 3.5 GHz are illustrated in Figure 10. As observed in the E-plane pattern, the proposed antenna successfully redirects radiation away from the vertical axis (θ = 0 deg), confirming the filling of the traditional monopole elevation null. The measured two-dimensional homopolarization pattern matches the simulated contour trend, verifying the passive overlay shaping mechanism. In the H-plane, the antenna maintains a stable, quasi-omnidirectional/broadside profile suitable for horizontal link stability. Minor deviations between the simulated and measured 2D traces are primarily attributed to cable scattering and the structural asymmetry introduced by the laboratory SMA connector setup, which aligns with the observed absolute gain discrepancies. The gain results are summarized in Table 4 and illustrated in Figure 11. The measured gain reduction of about 1.36 dB is attributed to a combination of SMA transition mismatch (around 0.05 dB), cable coupling effects (around 0.75 dB), finite ground reference differences, and dielectric constant variation in the glass substrate. These factors primarily affect absolute gain values but do not alter the overall radiation trend. Future platform-level integration with precise multi-layer laser lamination and automated micro-soldering jigs is expected to further eliminate these manufacturing tolerances. Despite the reduction in absolute gain, both simulated and measured results consistently exhibit the same elevation coverage redistribution trend. Although the present study focuses on antenna-level characterization on a glass substrate, practical vehicular platforms may introduce additional scattering and coupling effects due to metallic chassis structures and windshield curvature. Nevertheless, the presented results provide a useful baseline for evaluating the proposed passive coverage shaping mechanism prior to full-platform integration. Overall, the consistent agreement between measured and simulated 3D radiation patterns confirms that the proposed compact modified monopole structure provides a practical solution for upper-hemisphere coverage shaping in 5G NR n78 automotive antennas. Furthermore, a comprehensive performance comparison with recent radiation-control methodologies is summarized in Table 5 to highlight the unique merits of the proposed scheme. Unlike active pattern-reconfigurable designs [ 18, 19, 20] that offer steerable radiation agility but demand complex external DC biasing pathways, control circuitry, and RF switches, the proposed antenna relies entirely on passive current path engineering, minimizing fabrication costs and control circuit overhead. While advanced electromagnetic structures like the 3D-printed meta-surface platform [ 22] and the tightly coupled AVA array [ 23] achieve superior peak gains (up to 18 dBi) and excellent radiation/aperture efficiencies, they are inherently engineered for high-directivity beamforming or wide-angle scanning phased systems. The multi-layered 3D spatial structures or dense multi-port feeding networks required by these advanced systems present significant over-engineering and are incompatible with low-profile, thin-film lamination on automotive window glass. More importantly, the distinction between the proposed design and traditional passive planar configurations [ 24, 25] is highly apparent. Conventional structures implementing coupled parasitic slots [ 24] or arc-shaped DGS configurations [ 25] succeed in maintaining high efficiencies and establishing multi-band coverage. However, they strictly yield traditional omnidirectional fields and fail to suppress the vertical nulling characteristic. In stark contrast, our proposed FPC-modified monopole exhibits a calculated and targeted coverage-oriented trade-off. By treating the open/short-circuited stubs as a distributed sub-wavelength reactive loading network, the far-field superposition is altered to fill the traditional axial blind spot. Consequently, the proposed method retains the exceptional reliability, weather robustness, and design simplicity of a completely passive single-element framework while simultaneously providing the directional coverage shaping necessary for stabilized V2X link networks under glass-mounted environments. 4. Conclusions This paper proposes a compact FPC monopole antenna that incorporates shorted and open stubs alongside a coplanar waveguide (CPW) feed design. Optimized for 5G NR n78 automotive applications, the antenna is specifically engineered to enhance radiation distribution and elevation coverage for vehicular communications. In contrast to traditional Inverted-F Antenna (IFA) designs—which rely on resonant ground return paths or active switching components—the proposed architecture leverages a synthesis of open/shorted stubs and CPW feeding to achieve radiation control through current path engineering. By jointly optimizing the monopole geometry, CPW feed structure, and stub electrical lengths, the design enables phase-controlled current redistribution without forming a dominant λ/4 resonance. This mechanism mitigates the intrinsic elevation null of a classical monopole and redistributes radiation toward the upper hemisphere while maintaining impedance matching over 3.3 to 3.6 GHz. A 50% size reduction is achieved compared to the reference structure while preserving the target operating band. Both simulation and measurement results, including S-parameters, realized gain, radiation efficiency, and 3D radiation patterns, confirm that the proposed antenna provides improved elevation coverage with acceptable efficiency. Overall, the proposed approach demonstrates that passive current-path engineering provides an effective and low-complexity solution for coverage-oriented antenna design, particularly for on-glass vehicular installations where conventional omnidirectional radiation is not optimal. This work demonstrates an alternative approach to achieving radiation control without the added system complexity or the use of active components. The focus of this work is the antenna-level radiation behavior on a glass substrate rather than full-vehicle electromagnetic integration. Therefore, vehicle-body scattering effects, windshield curvature, and large-scale chassis interactions are not included in the present study. Full vehicular validation and platform-level integration will be investigated in future work. Author Contributions Conceptualization, F.-L.W. and J.-S.L.; Data curation, F.-L.W. and J.-S.L.; Writing—original draft, F.-L.W.; Methodology, J.-S.L.; Investigation, L.-W.K. and P.-H.K.; Validation, L.-W.K. and P.-H.K.; Supervision, C.-M.P. and I.-F.C.; Writing—review and editing, C.-M.P. and I.-F.C. All authors have read and agreed to the published version of the manuscript. Funding This research received no external funding. Data Availability Statement The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author. Conflicts of Interest The authors declare no conflicts of interest. References Federal Communications Commission (FCC). Office of Engineering and Technology Guidance on Certification of C-V2X Devices; KDB 511808 D01 C-V2X v02; FCC: Washington, DC, USA, 2025. 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Figure 1. ( a) Reference monopole and ( b) new-type antenna configuration. The blue and yellow-shaded regions represent the metallic layers on the front side, the green-shaded region denotes the bottom grounding plane on the back side, and the red circular indicator marks the explicit position of the CPW feed point. Figure 2. Equivalent circuit validation of the reference monopole baseline: ( a) Lumped RLC equivalent circuit network modeling the traditional monopole antenna, and ( b) compared input impedance |S 11| frequency response demonstrating the customized center resonance at 3.5 GHz. Figure 2. Equivalent circuit validation of the reference monopole baseline: ( a) Lumped RLC equivalent circuit network modeling the traditional monopole antenna, and ( b) compared input impedance |S 11| frequency response demonstrating the customized center resonance at 3.5 GHz. Figure 3. Equivalent circuit validation of the proposed current-shaping new antenna architecture: ( a) Evolved simplified lumped circuit incorporating a parallel shunt inductive element (L) representing the short-circuited stub loading paths, and ( b) Advanced Design System (ADS) circuit-simulated |S 11| frequency response verifying tracking optimization within the target bandwidth. Figure 3. Equivalent circuit validation of the proposed current-shaping new antenna architecture: ( a) Evolved simplified lumped circuit incorporating a parallel shunt inductive element (L) representing the short-circuited stub loading paths, and ( b) Advanced Design System (ADS) circuit-simulated |S 11| frequency response verifying tracking optimization within the target bandwidth. Figure 4. Simulated surface current distribution of the new-type antenna at 3.5 GHz, illustrating multi-path current distribution and phase-controlled radiation mechanism. The color gradient indicates the current magnitude in A/m, while the arrows represent the vector directions of the instantaneous surface currents. Figure 4. Simulated surface current distribution of the new-type antenna at 3.5 GHz, illustrating multi-path current distribution and phase-controlled radiation mechanism. The color gradient indicates the current magnitude in A/m, while the arrows represent the vector directions of the instantaneous surface currents. Figure 5. Reference monopole and new-type antenna configuration comparison of |S 11|. The horizontal yellow line represents the −10 dB impedance matching threshold, and the light blue shaded region denotes the targeted operating frequency band (from 3.3 GHz to 3.6 GHz). Figure 5. Reference monopole and new-type antenna configuration comparison of |S 11|. The horizontal yellow line represents the −10 dB impedance matching threshold, and the light blue shaded region denotes the targeted operating frequency band (from 3.3 GHz to 3.6 GHz). Figure 6. Comparison of 3D radiation patterns between the ( a) reference monopole and ( b) new-type antenna at 3.5 GHz. The conventional monopole exhibits a typical omnidirectional pattern with a pronounced elevation null, whereas the proposed antenna shows redistributed radiation toward the upper hemisphere and reduced null depth, consistent with the proposed current-path engineering mechanism. Figure 6. Comparison of 3D radiation patterns between the ( a) reference monopole and ( b) new-type antenna at 3.5 GHz. The conventional monopole exhibits a typical omnidirectional pattern with a pronounced elevation null, whereas the proposed antenna shows redistributed radiation toward the upper hemisphere and reduced null depth, consistent with the proposed current-path engineering mechanism. Figure 7. Measured radiated pattern in OTA chamber. Figure 7. Measured radiated pattern in OTA chamber. Figure 8. New-type antenna simulation and measurement results of |S 11|. The horizontal yellow line represents the −10 dB impedance matching threshold, and the light blue shaded region denotes the targeted operating frequency band (from 3.3 GHz to 3.6 GHz). Figure 8. New-type antenna simulation and measurement results of |S 11|. The horizontal yellow line represents the −10 dB impedance matching threshold, and the light blue shaded region denotes the targeted operating frequency band (from 3.3 GHz to 3.6 GHz). Figure 9. Comparison of 3D realized gain radiation patterns at 3.5 GHz: ( a) simulated reference monopole, ( b) simulated proposed antenna, and ( c) measured proposed antenna prototype. Figure 9. Comparison of 3D realized gain radiation patterns at 3.5 GHz: ( a) simulated reference monopole, ( b) simulated proposed antenna, and ( c) measured proposed antenna prototype. Figure 10. Comparison of simulated and measured 2D co-polarization radiation patterns of the proposed antenna at 3.5 GHz: ( a) E-plane (y-z plane), and ( b) H-plane (x-y plane). Figure 10. Comparison of simulated and measured 2D co-polarization radiation patterns of the proposed antenna at 3.5 GHz: ( a) E-plane (y-z plane), and ( b) H-plane (x-y plane). Figure 11. Simulated and measured realized peak gain curves of the proposed antenna as a function of frequency within the 5G NR n78 band. Figure 11. Simulated and measured realized peak gain curves of the proposed antenna as a function of frequency within the 5G NR n78 band. Table 1. Optimized values of new-type antenna. Table 1. Optimized values of new-type antenna. Code Length (mm) Code Length (mm) A 7.2 L 18.25 B 22.4 M 3.2 C 3.2 N 24.2 D 5.6 O 2.05 E 4.6 P 3.5 F 4.5 Q 10 G 3.5 R 1.2 H 2 S 1 I 23.5 T 1 J 3 U 0.9 K 15 V 0.3 Table 2. Comparison of antenna gain between reference monopole and new type. Table 2. Comparison of antenna gain between reference monopole and new type. Antenna Type Frequency Gain (dBi) Reference monopole 3.5 GHz 1.54 New type 6.35 Table 3. Quantitative comparison of radiation performance in the elevation plane at 3.5 GHz. Table 3. Quantitative comparison of radiation performance in the elevation plane at 3.5 GHz. Antenna Configuration Peak Realized Gain (dBi) Realized Gain at θ = 0 deg (Vertical Null) (dBi) Elevation Null Depth Reduction (dB) HPBW in Elevation (deg) Reference monopole ~2.15 −15.2 Baseline ~60 New type 4.99 1.35 16.55 ~115 Table 4. Simulated and measured antenna gain results of new-type antenna. Table 4. Simulated and measured antenna gain results of new-type antenna. New-Type Antenna Frequency Gain (dBi) Simulation 3.5 GHz 6.35 Measurement 4.99 Table 5. Comparison with recent radiation control antenna techniques. Table 5. Comparison with recent radiation control antenna techniques. Reference Operating Band (GHz) Peak Gain (dBi) Efficiency (%) Substrate/ Installation Mechanism Coverage Type Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. © 2026 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license. Share and Cite MDPI and ACS Style Wu, F.-L.; Liu, J.-S.; Peng, C.-M.; Kao, L.-W.; Ko, P.-H.; Chen, I.-F. 3D Coverage Shaping of an On-Glass 5G NR N78 Monopole Using Open/Short-Circuited Stubs. Electronics 2026, 15, 2543. https://doi.org/10.3390/electronics15122543 AMA Style Wu F-L, Liu J-S, Peng C-M, Kao L-W, Ko P-H, Chen I-F. 3D Coverage Shaping of an On-Glass 5G NR N78 Monopole Using Open/Short-Circuited Stubs. Electronics. 2026; 15(12):2543. https://doi.org/10.3390/electronics15122543 Chicago/Turabian Style Wu, Fei-Lung, Jung-Sheng Liu, Chia-Mei Peng, Li-Wei Kao, Pei-Hsuan Ko, and I-Fong Chen. 2026. "3D Coverage Shaping of an On-Glass 5G NR N78 Monopole Using Open/Short-Circuited Stubs" Electronics 15, no. 12: 2543. https://doi.org/10.3390/electronics15122543 APA Style Wu, F.-L., Liu, J.-S., Peng, C.-M., Kao, L.-W., Ko, P.-H., & Chen, I.-F. (2026). 3D Coverage Shaping of an On-Glass 5G NR N78 Monopole Using Open/Short-Circuited Stubs. Electronics, 15(12), 2543. https://doi.org/10.3390/electronics15122543 Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here. 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