Omni-directional Dual-Band Patch Antenna for the LMDS and WiGig Wireless Applications

A R T I C L E I N F O A B S T R A C T Article history: Received: 20 September, 2018 Accepted: 16 November, 2018 Online: 23 December, 2018 In this paper an omnidirectional dual band monopole antenna at 28 GHz and 60 GHz which is fit for indoor and outdoor wireless applications is developed. The proposed antenna consists of two rectangular patches with a T folded patch. The design, analysis, and optimization processes through this article are executed by the numerical method, Finite Element Method (FEM) and verified with another numerical method, Finite integration Technique (FIT). Good agreement between the results by these two simulators is obtained. The proposed antenna has achieved dual bands with omnidirectional patterns. The first band at 28 GHz is extended from 27.5 GHz to 28.958 GHz with 5.1 % bandwidth and total efficiency of more than 93% along the entire band which serves the LMDS band. The second band at 60 GHz is extended from 45.2 GHz to 84.4 GHz which serves the WiGig band with bandwidth of 60.6% and total efficiency of 85.5% along the entire band. The proposed antenna performance makes it a good candidate for the fifth generation (5G) applications.


Introduction
This paper is an extension of work originally presented in ACES [1]. More analysis and parametric studies have been done. The average data per person uses in telecommunication is rapidly increases over the past three decades [2]. This increase is more noticeable mostly with the outgrowth of the wireless communications. The main requirements for wireless communications are the ability to develop a low-cost, light-weight, and low-profile antennas to maintain good performance along a large bandwidth [2].
The shortage in the available global bandwidth has stimulated the reconnaissance of the under-utilized millimeter wave frequency band for the future wireless communications [3].
Multiband antennas have massive applications in millimeter band applications. A various techniques in the literature have been developed for multiband microstrip antennas as in [4][5][6][7][8][9][10][11][12]. For instance, a multilayer GaAs is described in [4] to achieve a multiband antenna operating at 35 GHz. In [5], two bands with less than 1.2% bandwidth with gains of -9 dBi and 1 dBi at 24 GHz band and 60 GHz band respectively is presented. A dual band antenna at 41 GHz / 52.2 GHz using a meta-resonator with pair of split ring resonators is introduced in [6] with bandwidth of 2 %, gain of 3.76 dBi, and efficiency of 71%. In [7], two different modes are obtained to get a dual band at 58 GHz and 77 GHz with gains of -2 dBi and 0.3 dBi, respectively. The achieved bandwidths at both bands are nearly 6%. A dual band centered at 24.5 and 35 GHz has been presented in [8] with only 1% bandwidth and less than 2.8 dBi gain using liquid crystal polymer. A coplanar hybrid dual band antenna at 83 GHz / 94 GHz with a slot in feeding line has been developed in [9]. In [10] an antenna array with Electromagnetic Band Gap [EBG] structure was used to develop a dual band at 28 / 38 GHz with bandwidth of less than 5.8%. A three layers of substrates have been used in [11] to design a Fabry-Perot cavity antenna operates at 36 GHz with high gain. In [12], Lshaped slots have been used to obtain a dual band 28 / 38 GHz slotted patch antenna.
In this paper, the design, optimization, and simulation of a monopole planar antenna are introduced. The antenna is optimized to operate at Ka _ band (28 GHz) for Local Multipoint Distribution Service (LMDS) which currently investigated for the fifth generation mobile cellular [13], and the V _ band (60 GHz) for Wireless Gigabit Alliance (WiGig) applications [14]. This paper is organized into four sections. Section 1 covers the introduction and literature review. Antenna structure and design is introduced in section 2. Parametric study of a dual band Lp Lbottom omnidirectional pattern circularly polarized wideband antenna is presented in section 3. The simulation results are investigated in Section 4. Finally, the conclusion is presented in section 5. Figure 1 shows the antenna geometry in perspective and top view. The proposed antenna patch consists of a T-folded shape with two rectangular patches and partially grounded [15]. The antenna gives wide bandwidth with improved antenna performance. The patch mounted on substrate FR-4 with a relative permittivity of 4.4. Figure 2 illustrates the whole antenna dimensions. The substrate dimension is W s by L s and the partial ground is W s by L g . The dimensions of T-folded are L top , L fold , L t W t for top length, folded side length, mid length, and mid width. The two patches have dimensions of W p by L p .

Antenna Geometry and Design
In the formulas, h represents the substrate height, w represents the TL width, and reff  represents the effective relative permittivity.

Parametric Study
The effect of varying antenna dimensions L fold , L top , L bottom , L P , W P , and L t using HFSS are shown in figures 3 to 8. The dimensions of the substrate, ground, and feeder are kept unchanged. With increasing L top of the horizontal part of T-shaped, the lower resonant frequency is decreased with same bandwidth whereas the upper bandwidth is decreased as shown in Figure 3.    As the length of rectangular patch L P increases, the upper and lower resonant frequency are decreased but the antenna matching becomes worse. Lower bandwidth is increases whereas the upper bandwidth is decreases as shown in Figure 6. Figure 7 illustrates the return loss varies with L fold . As L fold increases the lower resonant frequency decreases while upper resonant frequency unchanged whereas the lower bandwidth is not affected, the upper bandwidth is a little decreases as shown in Figure 7. With increasing L t , the lower and the upper resonant frequencies are not affected whereas the upper bandwidth is decreases, the lower bandwidth is unchanged as shown in Figure 8.

Antenna Simulation Results
The antenna dimensions are optimized to obtain an Omnidirectional radiation patterns with acceptable performance at 28 GHz and 60 GHz. Table 1 contains the optimized dimensions for the proposed antenna in order to have a dual band.
The optimized antenna is simulated using two simulators based on FIT [17] and FEM [18] in order to validate the results. The S 11 for the proposed antenna using FEM and FIT is shown in Figure 9. The FEM gives a better matching than FIT and the small deviation in the 60 GHz band is due to the different mesh sizes. As can be noted from Figure 9, the antenna well matched over the two bands and the impedance bandwidth for which S 11 ≤ -10 dB in 28 GHz band is extended from 27.52 GHz to 28.96 GHz which   The antenna resonates at 28.24 GHz with 1.44 GHz bandwidth (5.1 %) and at 64.76 GHz with wide bandwidth of 39.24 GHz (60.6%). The VSWR is shown in Figure 10 with VSWR ≤ 2 using FIT and FEM in the entire bandwidths of both bands. The antenna real and imaginary input impedance for the proposed antenna is illustrated in Figure. 11. As can be noted from Figure 11, the antenna is well matched to 50 Ω TL since the real part of the input impedance is approximately 50 Ω while the imaginary part tends to zero along the entire bandwidths of both bands.
The radiation patterns at 28 GHz and 60 GHz are illustrated in Figure 12. The directivity pattern at 28 GHz with D o of 2.28 dBi is illustrated in Figure 12(a) and at 60 GHz with D o of 3.41 dBi is shown in Figure 12(b). The total antenna efficiency along the lower band is 93 % while along the upper band is 85.5 %.

Conclusion
In this paper, antenna with two rectangular patches and a Tshaped folded patch is designed, optimized, and simulated. The antenna exhibits two bands resonate at 28.24 GHz and 64.76 GHz with bandwidths of 1.44 GHz (5.1%), and 39.24 GHz (60.6%) respectively. The lower band (Ka-band) is suitable for LMDS while the upper band (V-band) with wideband is suitable for WiGig. The omnidirectional radiation pattern is obtained using partial ground plane with maximum directivities of 2.28 dBi and 3.414 dBi at the two bands respectively. The total efficiency along the entire lower and upper bands exceeds 85% which can be used in the fifth generation applications.