Ka Ming Mak

Bio: Ka Ming Mak is an academic researcher from City University of Hong Kong. The author has contributed to research in topics: Patch antenna & Microstrip antenna. The author has an hindex of 8, co-authored 16 publications receiving 546 citations.

A Circularly Polarized Antenna With Wide Axial Ratio Beamwidth

Abstract: A novel circularly polarized (CP) antenna with wide angular coverage is presented. The proposed antenna is formed by two bowtie patch antennas and two electric dipoles. It can achieve an impedance bandwidth (SWR < 1.6) of 41% and a 3-dB axial ratio bandwidth of 33%. For this design, very stable and symmetrical radiation patterns are obtained. In the axial ratio passband, the 3-dB beamwidth is 85degplusmn2deg with a gain of 6.3 dBi plusmn0.3 dBi. The cross polarization is lower than -15 dB over a wide range of angles. For the entire half-power beamwidth, the axial ratio can be kept below 3 dB.

On the Use of U-Slots in the Design of Dual-and Triple-Band Patch Antennas

Abstract: The general method of using U-slots to design dual- and triple-band patch antennas is described. In this approach, one starts with a broadband patch antenna, which can consist of one or more patches. When a U-slot is cut in one of the patches, a notch is introduced into the matching band, and the antenna becomes a dual-band antenna. If another U-slot is cut in the same patch or in another patch, a triple-band antenna results. This method is applied to the L-probe-fed patch, the M-probe-fed patch, as well as the coaxially fed and aperture-coupled stacked patches. It is found that the patterns and gains of the dual-and triple-band antennas are similar to those of the original broadband antenna. Because the band notches introduced by the U-slots occur within the bandwidth of the antenna without slots, this method is suitable when the frequency ratios of the adjacent bands are small, usually less than 1.5.

Circularly Polarized Patch Antenna for Future 5G Mobile Phones

Abstract: A circularly polarized patch antenna for future fifth-generation mobile phones is presented in this paper. Miniaturization and beamwidth enhancement of a patch antenna are the two main areas to be discussed. By folding the edge of the radiating patch with loading slots, the size of the patch antenna is 44.8% smaller than a conventional half wavelength patch, which allows it to be accommodated inside handsets easily. Wide beamwidth is obtained by surrounding the patch with a dielectric substrate and supporting the antenna by a metallic block. A measured half power beamwidth of 124° is achieved. The impedance bandwidth of the antenna is over 10%, and the 3-dB axial ratio bandwidth is 3.05%. The proposed antenna covers a wide elevation angle and complete azimuth range. A parametric study of the effect of the metallic block and the surrounding dielectric substrate on the gain at a low elevation angle and the axial ratio of the proposed antenna are presented.

Polarization Reconfigurable Circular Patch Antenna With a C-Shaped

Abstract: Polarization reconfigurable circular patch antenna with a C-shaped slot is proposed in this communication. It is demonstrated that by introducing a reconfigurable C-shaped slot in a circular patch antenna, the polarization of the radiation of the antenna, operating either in a linearly or circularly polarized mode, can be switched effectively. It is switched between vertical and horizontal polarizations for a linearly polarized mode and switched between left hand circularly polarization and right hand circularly polarization for a circularly polarized mode. The polarization reconfigurable characteristic is realized by controlling the states of the two switching diodes mounted over a concentric circular slot incorporated on the patch, so as to vary the orientation of the C-slot. Prototypes of both linear polarization and circular polarization designs were developed and the performances were validated against measurements. Both antennas exhibit over 20% impedance bandwidth (standing wave ratio (SWR) < 2) and perform broadside radiation over the operating band. The 3-dB axial ratio bandwidth for the circularly polarized case is 4%.

A 5G Wideband Patch Antenna With Antisymmetric L-shaped Probe Feeds

Abstract: A dual-polarized patch antenna element fed by a pair of antisymmetric L-shaped probes is proposed. The designed twin L-shaped probe feeding structure is able to introduce feed capacitance to the antenna for broadband operation. The lengths of the two L-shaped probe feeds are identical, but the feeds are antisymmetric. This feeding design can minimize the unwanted radiation from the probe effectively. The dual-polarized antenna can be operated in the frequency band 1580–2750 MHz, which covers the current mobile communication systems, 3G and 4G and higher band frequencies. A prototype with dual slanted ±45° polarization has been fabricated for validation. Both the simulation and measured results show that the proposed antenna has wide bandwidth of 54% (SWR < 2) with desirable directional radiation patterns in the vertical and horizontal planes, as well as high isolation better than −30 dB between the two input ports.

Eight-Port Orthogonally Dual-Polarized Antenna Array for 5G Smartphone Applications

Abstract: A dual-polarized hybrid eight-antenna array operating in the 2.6-GHz band (2550–2650 MHz) for 5G communication multi-input multi-output (MIMO) operation in the smartphone is presented. The proposed hybrid antenna array elements are symmetrically placed along the long edges of the smartphone, and they are composed of two different four-antenna array types (C-shaped coupled-fed and L-shaped monopole slot) that exhibit orthogonal polarization. Therefore, coupling between the two antenna array types can be reduced, and the MIMO system performances are enhanced. A prototype of the proposed eight-antenna array is manufactured and measured. A good impedance matching (10 dB return loss or better), desirable cross-polarization discrimination (better than 15 dB), and an acceptable isolation (better than 12.5 dB) are obtained. Envelope correlation coefficient and channel capacity are also calculated to evaluate the MIMO performances of the proposed antenna array.

Microstrip Patch Antennas

Abstract: Introduction Review of Some Background Materials General Formulation of the Cavity Model Characteristics of the Rectangular Patch Characteristics of the Circular Patch The Annular-Ring and the Equilaterial Triangular Patch Introduction to Full Wave Analysis of Microstrip Antennas Some Methods of Tuning the Resonant Frequencies of Patch Antennas Broadbanding Techniques Size Reduction Techniques Dual and Multi-Band Designs Dual Polarized Patch Antenna Designs Circular Polarization Microstrip Arrays

Solving the 5G Mobile Antenna Puzzle: Assessing Future Directions for the 5G Mobile Antenna Paradigm Shift

Abstract: Advances in antenna technologies for cellular hand-held devices have been synchronous with the evolution of mobile phones over nearly 40 years. Having gone through four major wireless evolutions [1], [2], starting with the analog-based first generation to the current fourth-generation (4G) mobile broadband, technologies from manufacturers and their wireless network capacities today are advancing at unprecedented rates to meet our unrelenting service demands. These ever-growing demands, driven by exponential growth in wireless data usage around the globe [3], have gone hand in hand with major technological milestones achieved by the antenna design community. For instance, realizing the theory regarding the physical limitation of antennas [4]-[6] was paramount to the elimination of external antennas for mobile phones in the 1990s. This achievement triggered a variety of revolutionary mobile phone designs and the creation of new wireless services, establishing the current cycle of cellular advances and advances in mobile antenna technologies.

Crossed Dipole Loaded With Magneto-Electric Dipole for Wideband and Wide-Beam Circularly Polarized Radiation

Abstract: A crossed dipole that is loaded with a magneto-electric dipole to produce the wideband and wide-beam circularly polarized radiation characteristics is proposed. The crossed dipole is incorporated with double-printed vacant-quarter rings to feed the antenna. The antenna is backed by a metallic cavity to provide a unidirectional radiation pattern with a wide axial-ratio (AR) beamwidth and a high front-to-back ratio. Experimental results showed that the prototype with an overall size of $120\times 120\times30.5~\hbox{mm}^3$ has a $\vert { S}_{11}\vert bandwidth of 1.274–2.360 GHz and a 3-dB AR bandwidth of 1.39–1.82 GHz. The antenna showed a right-hand circular polarization (CP) radiation with a very wide 3-dB AR beamwidth ( $>165^{\circ}$ ) and a high radiation efficiency ( $ > 94\%$ ) within the operational bandwidth.

Single-Layer Single-Patch Dual-Band and Triple-Band Patch Antennas

Abstract: Recently, it was shown that a dual- or triple-band patch antenna can be designed by cutting U-slots in the patch of a broadband antenna, and the method was applied to the L-probe fed patch, the M-probe fed patch, coax-fed stacked patches, and aperture coupled stacked patches. All these cases involve either a rather complicated feed, or more than one patch, or more than one layer. In this communication, this method is applied to a broadband U-slot patch antenna. When one additional U-slot patch is cut in the patch, a dual-band antenna results. When two additional U-slot patches are cut in the patch, a triple-band antenna results. The advantages of the resultant configurations are (1) the feed is simple and (2) the structures remain single-layer and single-patch. Both simulation and measurement results are presented to demonstrate the feasibility of this design.