In this letter, we design a circularly polarized (CP) waveguide aperture antenna with a wide axial ratio bandwidth (ARBW). The unit is composed of three waveguides with different rotation angles and width. The reflected and transmitted orthogonal electric fields are superimposed on the asymmetric plane of the rotating structure in each layer, which not only reduces energy reflection but also promotes the decomposition of the electric field with the same amplitude and the phase difference 90° in different rotating waveguides. Finally, a circularly polarized electric field is formed on the antenna's surface. The phase difference and amplitude difference of orthogonal electric field a e approximately 90° and less than 1.2 dB, respectively. In addition, the different width of the waveguide plays a role in impedance matching. A 2 × 2 array is fabricated and measured to verify the validity of the design. The measured results shows good agreement with the simulation. Measured impedance bandwidth of 37.9% (27.5-40.4 GHz), axial ratio (AR) bandwidth of 41.2% (27-41 GHz), and a gain of 15.7 dBi at center frequency have been obtained.

A novel ultrawideband circularly polarized (CP) phased array antenna was developed by combining the low-profile design of a stripline-to-slotline balun with the wide scanning characteristics of a tightly coupled dipole array (TCDA). This antenna boasts a low voltage standing wave ratio (VSWR) and low axial ratio (AR). To address the common-mode resonance issue, a circular slotline cavity was implemented as a four-stage series fan-shaped cavity. This design effectively extends the length of the short-circuit stub, enhancing the short-circuit impedance value and expanding the scanning bandwidth from 3:1 to 6.4:1. Notably, a rotating wide-angle impedance matching (WAIM) layer was introduced for the CP TCDA, marking the first time this approach has been employed. This innovation not only increased the number of matching network stages for achieving a low VSWR but also enhanced the consistency of the main polarization, reducing the cross-polarization ratio to achieve a low AR. The resulting 8 × 8 CP phased array antenna demonstrated exceptional performance, operating over a remarkable 6:1 bandwidth (2–12 GHz). It satisfies the criteria of Active VSWR<2.5 and AR<2.7 dB within a ±60° scanning range.

Due to the huge potential of application in the communications, electronic jamming, and radar fields, circularly polarized (CP) array antennas with wide axial ratio (AR) scanning performance at wide frequency bandwidth have received great attention. A wideband scanning CP planar array antenna built by new, tightly coupled dipole array (CP-TCDA) elements, which have achieved promising results in terms of both scanning AR bandwidth and angle range in all scanning planes, is presented in this paper. Based on the shorted transmission line model, a CP-TCDA element arranged along the ±45° direction is constructed, which can shift the middle-frequency scanning blind zone out of band and thus obtain a wideband scanning AR bandwidth. Furthermore, the proposed CP-TCDA element adopts four shorting pins and four square parasitic strips, which improve wide-angle CP performance for xz -plane and diagonal-plane scans, respectively. An $8\times 8$ left-handed CP planar array antenna based on the proposed CP-TCDA elements is designed and prototyped. The results show that the array antenna is able to operate over a 3:1 (4–12 GHz) overlapping bandwidth, and it meets the requirements of AR < 3 dB and active VSWR < 2.9 within a ±45° scanning angle range.

In this study, a novel broadband circularly polarised waveguide slot array antenna with a wide axial ratio bandwidth is designed. The circular polariser is excited by the waveguide radiation linear polarised antenna, whose end is bent by 90° and generates a circularly polarised electric field. The matching waveguide between the slot and the polariser improves impedance matching. Furthermore, the structure with the added waveguide changes waveguide impedance, which can be used to realise impedance matching, and reduces the spacing between the units. In this study, a 4 × 4 antenna array is fabricated. The measured results reveal that the array achieves −10 dB impedance bandwidth of 27% (11.15–14.63 GHz) and the 3 dB axial ratio bandwidth of 23% (11.48–14.52 GHz). An aperture efficiency higher than 71% is obtained, with the maximum gain of 22 dB. The antenna side lobes levels are less than −13 dB in the operating bandwidth.

In this paper, a wide‐angle beam scanning circularly polarized (CP) phased array element, which consists of a concentric tightly coupled dipole array (TCDA) element with a two‐layer parasitic ring structure and a wideband 90° phase shifter, is proposed. To solve the problem of the scanning blindness zone caused by a concentric layout, the grounded coupling patch for the traditional TCDA element is ‘split’ into a combination of a grounded parasitic ring and coupling patch. This combination structure can not only suppress the in‐band common‐mode resonance but also destroy the scanning blind zone mode formed by the dipole and grounded coupling patch. In addition, a two‐layer parasitic ring structure is introduced to obtain a wider axial ratio (AR) beamwidth relative to a single‐layer structure, so a wide‐angle beam scanning AR is realized. An 8 × 8 left‐handed CP planar array based on the proposed wide‐angle beam scanning CP elements is designed and prototyped. Results show that the array can operate over a 3.2:1 (3.75–12.0 GHz) overlapping bandwidth, meeting an AR < 3 dB in the main beam and an active voltage standing wave ratio <2.8 within a ±60° angle scanning range.

The sidelobe level (SLL) is an essential performance factor for satellite communication antennas. A low-SLL design can effectively suppress adjacent satellite interference. A low-SLL design method for a variable inclination continuous transverse stub (VICTS) antenna is proposed in this paper. The VICTS antenna is composed of three rotatable parts: a feeding plate, a radiation plate, and a polarization plate. The radiation plate comprises two groups of stubs with different radiation ratios. Combined with the nonlinear slow-wave structure attached to the feeding plate, the radiation ratio of the unit can be adjusted. The aperture field of the VICTS antenna using this method can be tapered in order to suppress the SLL. To verify the effectiveness of this method, the antenna prototype is fabricated and measured in a microwave anechoic chamber. The simulation and the measurement are in good agreement. The reflection coefficient of the antenna is kept below −15 dB and between 13.75 GHz and 14.5 GHz. When the radiation plate and the feeding plate rotate relative to each other, the pattern beam can be scanned from 5° to . In the scanning range, the typical SLL can reach −18 dB.