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A novel circularly polarized (CP) antenna with wide angular coverage is presented. The proposed antenna is formed by a 45 ° slot cut in the center of a rectangular patch antenna and a square ring around it. It can achieve an impedance bandwidth of 110 MHz and a 3 dB axial ratio bandwidth of 25 MHz. For this design, very stable and symmetrical radiation patterns are obtained. The 3 dB axial ratio beamwidth for the antenna is 160 °, compared with the antenna that without the metal square ring, the antenna with square ring has 19 ° more 3 dB axial ratio beamwidth. This antenna has been successfully applied on passive keyless entry system on door lock. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:672–675, 2016

A bandwidth enhanced method of a low-profile substrate integrated waveguide (SIW) cavity-backed slot antenna is presented in this paper. Bandwidth enhancement is achieved by simultaneously exciting two hybrid modes in the SIW-backed cavity and merging them within the required frequency range. These two hybrid modes, whose dominant fields are located in different half parts of the SIW cavity, are two different combinations of the and resonances. This design method has been validated by experiments. Compared with those of a previously presented SIW cavity-backed slot antenna, fractional impedance bandwidth of the proposed antenna is enhanced from 1.4% to 6.3%, its gain and radiation efficiency are also slightly improved to 6.0 dBi and 90%, and its SIW cavity size is reduced about 30%. The proposed antenna exhibits low cross polarization level and high front to back ratio. It still retains advantages of low-profile, low fabrication cost, and easy integration with planar circuits.

Single fed low profile cavity backed crossed slot antennas for dual frequency dual linear polarization and circular polarization applications are first presented in this paper. By employing the substrate integrated waveguide (SIW) technique in the antenna designs, the low profile backed cavity structure can be realized by using only a single layer of low cost printed circuit board (PCB) substrate. A single grounded coplanar waveguide (GCPW) is employed as the feeding element to excite the TE 120 and TE 210 modes in the SIW cavity. A crossed slot structure is used as the radiating element in order to radiate the desired dual linearly or circularly polarized wave. From the measurement results, it is seen that these novel antennas retain the advantages of conventional metallic cavity backed antennas, including high gain, high front-to-back ratio (FTBR), and low cross polarization level (CPL). Furthermore, the proposed antennas also possess the advantages of low profile, light weight, low fabrication cost, and easy integration with planar circuits.

A novel design method of low profile cavity backed planar slot antenna has been described in this paper. The whole antenna including backed cavity and feeding element is completely constructed at a single substrate by using substrate integrated waveguide technique and grounded coplanar waveguide. An example with 1.7% bandwidth has been presented, which has 5.4 dBi gain, 16.1 dB front-to-back ratio and -19 dB maximum cross polarized radiation level with its total thickness less than lambda0/50. The proposed antenna keeps good radiation performance of conventional cavity backed antenna and has advantages of conventional planar antenna including low profile, light weight, easy fabrication with low cost and convenient integration with planar circuit.

A wideband 60GHz monopole on-chip antenna based on 0.18μm CMOS process with an artificial magnetic conductor (AMC) is presented. The structure of the proposed on-chip antenna consists of a circular ring-shaped monopole antenna fed by a 50Ω coplanar waveguide (CPW). Results show that the proposed circular ring-shaped monopole antenna mounted on AMC plane can offer higher gain, higher radiation efficiency and wider impedance bandwidth, while has a smaller antenna size.

The design of circularly polarized microstrip patch antenna (MPA) with wide axial ratio beamwidth working at 2.4GHz band is proposed. The wide axial ratio beamwidth is achieved by a 45° rotated slot cut in the center of the square MPA. By placing two back-to-back MPAs on intelligent door lock, the function of indoor-outdoor recognition has been successfully realized.

A circularly polarized antenna realized by a power divider fed cavity backed slot antenna is presented in this article.The cavity backed slot antenna is constructed on a single layer substrate by using substrate integrated waveguide (SIW) technique. A T-junction power divider with equal magnitude and 90° phase difference outputs is adopted as the parallel feed to excite the SIW backed cavity. Circularly polarized radiation can be generated when two orthogonal cavity modes are excited simultaneously in the backed cavity. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:107–109, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26482