A dual-layer multibeam conformal slot array antenna operating at a center frequency of 10 GHz is proposed in this paper. The antenna consists of a microstrip Rotman lens and a substrate-integrated waveguide (SIW) array of 10×10 radiating slots, which is axially mounted onto a cylindrical surface with a radius of 90 mm, i.e., 3λ ₀ . The Rotman lens feeds the slot array through the coupling slots in the broad sides of the SIWs. An improved design process is introduced for realizing a conformal Rotman lens for cylindrically conformal arrays. There are unique requirements for the phase distribution and phase compensation in cylindrically conformal applications. The Rotman lens and slot antenna are built and optimized in fullwave simulation software. To validate the proposed concepts, a conformal antenna prototype is implemented and measured. The experimental results demonstrate a scanning range of ±46°, with a -3 dB crossover level between adjacent radiation beams in the E-plane and a -20 dB sidelobe level in the H-plane. The measured and simulated radiation patterns of all the scanned beams are in good agreement. This type of multibeam conformal slot array has been theoretically and experimentally studied, and it demonstrated the potential for applications in aircraft, missiles, and high-speed vehicles.

A single-layer substrate integrated waveguide slot array is presented for use in low sidelobe applications. A compact three-level power divider is developed to provide the required phase distribution and enhanced co-phase bandwidth. Then, the Elliott’s design procedure is employed taking accurately into account both the external coupling and the high-order mode internal coupling. The measured radiation pattern and the frequency response are in very good agreement with design specifications and with simulated results provided by CST Microwave Studio. The measured sidelobe level at the center frequency is below $-$ 32.3 dB in the E-plane and below $-$ 33.8 dB in the H-plane for a design goal of $-$ 35 dB.

Rydberg atom, which exhibits a strong response to weak electric fields, is regarded as a promising atomic receiver to surpass sensitivity of conventional receivers. However, its sensitivity is strongly limited by the noise coming from both classical and quantum levels and how to enhance it significantly remains challenging. Theoretically, we strive to optimize the laser array and emphasize the significance of coherence among microwave signals, laser beams power uniformity in laser array for enhancing signal-to-noise ratio (SNR) and promoting the sensitivity to a new level. To enhance practical application mobility and integration, we propose two optimization schemes: six-port fiber-coupled vapor cell probe array and cascaded diffraction gratings. We maintain steady microwave signal coherence in the laser array by using identical vapor cells and positioning the probe lasers on the incident wave’s equal phase plane. Our findings reveal that the wavefront phase difference for the six-port fiber-coupled vapor cell array is 10 degrees, while the cascaded diffraction gratings show a 16 degree difference, with laser intensity uniformity reaching 90.4%. In our experiment, 4.6 dB SNR enhancement was achieved by utilizing the cascaded diffraction gratings to generate a 2×2 probe laser arrays compared to the performance of a laser beam, and it can be enhanced further just by adding more laser beams. In particular, a 2×2 laser array experimental verification yielded 19nv/cm/√Hz@8.57 GHz. More importantly, the intermediate signals of laser array maintain coherence. Therefore, SNR improvement is allowed even in detecting weak target signals amidst strong noise and clutter. The results could offer an avenue for the design and optimization of ultrahigh-sensitivity Rydberg atomic receivers and promote applications in cosmology, meteorology, communication, and microwave quantum technology.

The Elliott’s procedure for the design of planar waveguide arrays of longitudinal slots has been extended to the cylindrical conformal case. The presented procedure has been devised to deal with the most general case of a cylindrical conformal substrate integrated waveguide (SIW) longitudinal slot array with a dielectric cover. Both external and internal mutual coupling have been accurately and effectively taken into account. The results of the synthesis procedure have been validated using both Ansys HFSS simulations and experimental results, showing a good agreement with the design specifications.

Rydberg atom-based microwave(MW) atomic receiver is regarded as a promising atomic receiver to surpass sensitivity of conventional receivers. This article proposes a tunable Fabry–Perot(FP) cavity which locally enhances MW electric(E) field to improve measurement sensitivities. This FP cavity includes a 0.9947 reflection coefficient periodic metal slit structure and a reflective plate. In our experiment, 21 dB signal-to-noise ratio(SNR) enhancement is achieved by utilizing the FP cavity. Ultimately, the atomic receiver loaded with a FP cavity provides a sensitivity of 5nv/cm/ √ Hz@8.57 GHz that is the most advanced sensitivity known based on ¹³³ Cs resonant transition |44D _5/2 ⟩ → |45P ^3/2 ⟩. Since the FP cavity is different from the traditional closed cavity and split ring resonance mechanism, a large enhancement tunable frequency bandwidth of 4.8-12.2 GHz can be achieved by adjusting the plate spacing. Additionally, the FP cavity solves the direct coupling between the electromagnetic wave and resonator in the X-band, which provides mobility and flexibility. We take all the vapor cell walls refractive index and metal reflections into account as the resonance-based system is more sensitive to errors.

A slot array in substrate‐integrated waveguide (SIW) technology fed by a microstrip Rotman lens is proposed. This compact multibeam antenna is designed in two layers using a novel transition based on double‐stepped coupling slots on the broad wall of SIWs. Compared with a rectangular transverse coupling slot, this transition is broadband and its coupling power can be controlled for low‐sidelobe applications. The radiating part is a 10 × 10 slot array and the beam‐forming network can generate seven beams with good coverage from −30° to 30° in the azimuthal plane. To validate the proposed concept, an antenna prototype is implemented at 10 GHz. The frequency response and measured radiation patterns are in good agreement with simulated results provided by full wave simulation software. Experimental results show that the sidelobe level is lower than −21 dB for the central beam in both H and E planes and better than −18 dB for the edge beams.