# A Patch/Dipole Hybrid-Mode Antenna for Sub-6 GHz Communication
## 1 Introduction  
Microstrip antennas are popular structures for a shared aperture due to their low mass and ability to be easily integrated with the feeding network [1], which are suitable for micro base station applications for persuasive fifth generation communication. Dipoles and microstrip patches were interlaced in [2] to realize a bandwidth of 8.9% in the S-band and 17.0% in the X-band, with a frequency ratio of 1:3. A dual-band dual-polarized antenna was introduced in [3], where a parasitic patch was stacked over a driven patch. In this way, each polarization could share one feeding network, which contributed to the reduction of the feeding networks and input ports. Therefore, the antenna had two operating bands, respectively covering the C-band from 5.05 to 5.30 GHz and the X-band from 9.60 to 10.30 GHz.  
Both the patch and dipole have a small bandwidth within a limited profile. A common method is to shape the patch or slot for broadening the bandwidth. Two conventional quarter-wave patch antennas with an L-slit and U-slot were implemented and compared in [4], which achieved impedance bandwidths of 45.0% and 53.0%, with profiles of less than 0.13 \(\lambda_{0}\) and 0.11 \(\lambda_{0}\), respectively. Here, \(\lambda_{0}\) is the wavelength in the free space at the center of the operating frequency. However, an increase in bandwidth using slotting techniques is always at a sacrifice of antenna gain. Therefore, how to keep a large bandwidth and a high gain at the same time is an attractive issue for a compact element.  
A magneto-electric (ME) dipole antenna was proposed in [5], where an obtuse-triangular structure was used as a magnetic dipole. The ME dipole could reduce the profile to 0.097 \(\lambda_{0}\), maintaining a stable gain of 9.2 \(\pm\) 1.1 dBi and achieving an impedance bandwidth of 28.2%. Hybrid mode is another promising candidate through sequentially exciting the adjacent modes in the interested band [6]. Two adjacent modes could be simultaneously excited by a crossed bow-tie dipole and an octagonal-ring antenna [7]. It retains the advantages of a low profile, broad bandwidth, and stable radiation pattern.  
Similarly, the hybrid mode with sidewalls for the lower ultra-wide band was proposed in [8], in which the patch mode and slot mode were sequentially excited in a shared aperture. This antenna could cover a frequency band from 3.00 to 4.99 GHz and maintain a minimum gain of 9.0 dBi with a projection area of 1.09 \(\lambda_{0}\times 1.04\)\(\lambda_{0}\) and a profile of 0.13 \(\lambda_{0}\).  
This paper is an extension of the conference paper [9], where mode analysis is detailed to demonstrate the mode hybridization. In conjunction with a tapered feeding line, a broadband balun is designed to convert the single feeding to differential feeding. In this way, the complexity of the feeding method is reduced when compared with the hybrid mode antennas [7; 8]. The low-cost substrate used can also help to reduce the cost of this antenna and therefore support the dense deployment for micro base station applications. The frequency bands of n77 (3300-4200 MHz), n78 (3300-3800 MHz), and n79 (4400-5000 MHz), specified by the Third Generation Partnership Project (3 GPP) for 5G communication, are covered by the proposed antenna for Sub-6 GHz communication [10].