In this communication, the design of a circularly polarized perforated gradient index flat lens antenna with directive beam-steering properties is presented for millimeter-wave applications at W- band (75 – 95 GHz). The dielectric lens, fed by an open-ended square waveguide located in the lens focal plane, enhances the radiation in a particular direction, generating a high-directivity beam with planar wavefront. The integration of a dielectric polarizer with the lens allows the conversion from a linearly polarized incident wave to a circularly polarized emitted wave over the whole bandwidth. Horizontally and vertically polarized waves, achieved by the excitation of the fundamental square waveguide TE01 and TE10 modes are transformed to left-hand circularly polarized and right-hand circularly polarized waves, respectively. A ±30° scan range in both azimuth and elevation planes is demonstrated for the whole frequency range, attained by displacing the feed along the focal plane of the lens. Lens and polarizer are manufactured as a single piece by stereolithography 3D printing technology with Form 3 Formlabs 3D-printer. Measured results show maximum measured directivity values that range from 23.5 to 23.8 dB, a remarkable circular polarization purity as a wide axial ratio bandwidth of 20.58% (< 3 dB), from 77.5 GHz to 95 GHz, is achieved for the principal beam steers and an aperture efficiency for broadside beam direction between 90.32% and 57.34% in the frequency band of interest.

This paper presents the calibration process involved in a planar active phased array antenna operating in the K-band (17.7–20.2 GHz). The array consists of eight columns, each containing a 1 × 8 subarray of patch antennas. To enhance the antenna bandwidth, a double-stacked patch structure is employed. We analyze the challenges encountered when measuring active antennas. Additionally, we discuss the solutions and calibration techniques used to improve the array performance. Finally, we present the results of the optimal calibration approach, comparing simulated and measured data, both with and without calibration, to evaluate the improvements achieved.

This paper presents a system architecture to accomplish over-the-horizon communications with medium-sized unmanned aerial vehicles (UAV) in order to enhance its autonomy and maximum range. This architecture is based on using a second UAV as a communication relay with a compact active circular array with separated transmitting and receiving elements at C band. The designed active feeding network provides switching capabilities in order to selectively activate these elements depending on the desired direction of the antenna beam, achieving maximum equivalent isotropic radiated power (EIRP) in transmission and maximum antenna gain in reception. In this way, a bidirectional long-range link for telemetry, telecommand and high-resolution video can be deployed between UAVs providing high quality of service, reliability and moderate data throughput at an affordable cost. Based on measurements of a manufactured prototype, the maximum range of the deployed air-air link using the designed system is estimated in 20 km, considerably increasing the performance of current systems based on the use of omnidirectional antennas onboard UAVs.

This paper comprehensively examines the non-idealities inherent in commercially available beamformers and explores their implications in the calibration procedures for phased array antennas. The non-ideal nature of the beamformer is meticulously modeled and assessed through extensive S-Parameter measurements to discern its impact on analyzed excitation retrieval methods. The Rotating-element Electric-field Vector (REV) and Control Circuit Encoding (CCE) methods are simulated using a synthetic array with spherical wave expansion driven by output coefficients measured from the beamformer. Simulations are executed to compare the REV method with a Selective-REV variant, designed to enhance coefficient prediction accuracy by leveraging a priori knowledge of phase-shifter amplitude deviations. Additionally, amplitude, phase, and complex CCE encodings are employed to determine the encoding technique that best accommodates beamformer non-idealities. Finally, anechoic chamber measurements assess the pattern prediction capabilities of the analyzed methods, and an iterative calibration scheme is proposed to compensate for the studied beamformer errors due to its behavior.

This paper presents the measurement setup and methodology used to characterize the G/T performance of active antennas in an anechoic chamber using three different measurement techniques. First, a standard gain horn (SGH) and a commercial amplifier were employed to evaluate the G/T ratio using three different methods. The results were then compared with the theoretical G/T value, calculated from the known gain of the SGH and the noise figure (NF) of the amplifier, to validate the accuracy of the proposed measurement approaches. After the validation stage, the proposed methodology was applied to an 8 × 8 lineal phased array antenna operating in the 17.7–20.2 GHz SATCOM reception band. The G/T parameter was evaluated using the three measurement methods over a wide angular range, from −35° to +35°. Furthermore, a comprehensive uncertainty analysis was carried out for each measurement method, considering the main factors affecting the accuracy of the G/T estimation. This analysis enabled a systematic comparison of the three methods in terms of measurement performance, repeatability, and uncertainty, providing a more robust assessment of their applicability for the characterization of active phased array antennas.