# A Miniaturized RHCP Slot Antenna for Wideband Applications Including Sub-6 GHz 5G  
[PERSON]  
1 Department of Electrical Engineering, College of Engineering, University of Basarah, Basarah 61001, Iraq; [EMAIL_ADDRESS] (F.M.A. )1 Department of Electrical Engineering, College of Engineering, University of Basarah, Basarah 61001, Iraq; falih. surfaces for ISM and WiMax applications [8]. Multiband CP antennas were generated in [9; 10] by using a Minkowski fractal slot for many frequency bands [9], and a multiband ultra-high-frequency (UHF) antenna for RFID applications was presented in [10]. To generate wideband dual CP antennas, aperture-coupled stack patches were designed in [11]. The patches are fed by a hybrid coupler to obtain an axial ratio bandwidth (ARBW) of 29.1% extended along the range (4.7-6.3 GHz). In [12; 13], MIMO antennas were proposed. A four-element MIMO G-shaped monopole antenna was presented as a dual CP with an ARBW of 67.7% [12]. A wideband CP monopole antenna was proposed by using a co-planar waveguide (CPW)-fed approach [14; 15]. Broadband C-shaped CP monopole antennas were presented in [16; 17; 18]. In [19], a cross-shaped monopole antenna was designed to obtain an ARBW of 42.6%. Recently, a 2 \(\times\) 2 metasurface antenna array was proposed in [20] by using nonuniform slots to improve the ARBW to 61.75%. Wide-slot antennas have been designed to generate wideband CP as a radiating element due to their advantages of achieving a wider impedance BW, weak coupling with the nearby electric components, and ease of fabrication [21]. For these reasons, they have been adopted in this work. In [22; 23; 24], narrow-band CP slot antennas were proposed. An artificial magnetic conductor (AMC) reflector with a \(\Gamma\)-shaped microstrip line was proposed to feed the slot antenna in [22] to achieve an impedance BW of 40.78% and an ARBW of 39.02%. For 5G techniques, an air-filled substrate-integrated waveguide (AF-SIW) CP slot antenna array was proposed in [24] to obtain an antenna BW of 18.4% and an ARBW of 16.4%. An L-shaped slot antenna was proposed in [24] in which a square-loop sequential-phase feeding structure was used to feed the antenna to generate an impedance BW of 18% and an ARBW of 13.2%. In [25], a wide-slot antenna was proposed for an ultra-wideband (UWB) frequency range with two band notches. ARBWs equal to 55.0% and 29.3% were achieved in [26], which is a dual-wideband slot antenna and dual-sense CP with overall dimensions of 50 \(\times\) 50 \(\times\) 1.0 mm\({}^{3}\). Slot antennas that are fed by CPW were presented in [27; 28; 29; 30]. A circular slot in the ground plane was utilized for generating CP in [31; 32; 33]. For a digital cellular system, an asymmetric wide-slot antenna was presented in [34]. A broadband wide-slot antenna was proposed in [35] for the mid-band of 5G applications. In [36], a square-shaped open-loop feeding structure was utilized to feed a split-ring resonator slot antenna to achieve an impedance BW and ARBW of 10.48%. Irregularly shaped square-slot antennas were realized in [37; 38] with an inverted L-shaped and F-shaped microstrip feed, respectively. An antenna BW and ARBW approximately equal to 94.3% and 76.9%, respectively, were attained using an open-slot antenna [39]. A square-slot antenna with an L-shaped microstrip feed was designed to obtain an ARBW of 54.2% [40]. A square-ring slot antenna is fed by an L-shaped feedline to generate an ARBW of 3.7 GHz from 4.75 to 8.45 GHz [41]. An improved hybrid metasurface (IHMS) is utilized in a 2 \(\times\) 2 antenna array with four corner cut patches to achieve a wide ARBW of 2.85 GHz [42]. However, such metasurface-based designs often involve increased structural complexity, higher fabrication costs, and potential challenges in terms of scalability and integration. Moreover, recent advances in the use of metamaterial-inspired resonators for antenna miniaturization and wavefront control offer promising directions for future research.