NASA's planned Aerosol, Cloud and Ecosystems (ACE) mission will provide RF measurements for studying the role of aerosols on cloud development. The space-borne radar requires a fixed-beam at W-band and a wide-swath (>100 km) scanning beam at Ka-band.The full scale antenna is comprised of a parabolic cylinder reflector/reflectarray with a fixed W-band feed and a Ka-band Active Electronic Scanning Array (AESA) feed. Cassegrain folded optics is employed to reduce the required mass, volume, mechanical complexity and cost. An innovative reflectarray design provides a focused low-loss pencil beam at W-band, and is RF transparent at Ka-band. The AESA transmit/receive (T/R) modules provide high RF output power and low noise figure.Several planar reflector/reflectarray prototypes were designed and fabricated to validate the novel reflectarray element/surface technology and design methodology. The measured W/Ka band reflector/reflectarray gains and patterns agree very well with predictions thereby confirming the viability of the full scale design.The proposed ACE dual-band reflector/reflectarray antenna system design, first described in [1][2][3][4][5], is shown in Figure 1. For Ka-band (35 GHz) operation, the parabolic cylinder reflector is fed by an AESA line feed located at the virtual focal line of the parabolic cylinder (Cassegrain optics) and ±10 degree azimuth beam steering is provided by electronically scanning the feed in one dimension (azimuth). Array fed offset reflector trades were performed using the COTS GRASP TM code, and a T/R module design was developed in parallel to meet radar performance requirements such as sensitivity and side lobes. System trades were used to develop a module design (shown in Figure 2) to meet critical requirements, while also addressing mechanical and thermal concerns. Four elements are needed in the elevation (vertical) plane to provide proper secondary reflector illumination taper and meet stressing sidelobe requirements.For W-band (94 GHz) operation, a horn feed source is located at a virtual focal point (Cassegrain optics with beam waveguide) as shown. A very thin single layer printed circuit reflectarray surface [6] (transparent at Kaband) provides azimuth and elevation focusing of the Wband energy to/from the main parabolic cylinder reflector [7][8][9][10][11][12][13][14][15][16]. The W-band reflectarray surface also provides a slight elevation displacement of the virtual focus that enables separation of the sub-reflectors and the feeds. This design retains co-alignment of the Ka and W-band beams. II. DUAL-BAND REFLECTOR/REFLECTARRAY DESIGN A. Reflectarray DesignReflectarrays combine the features of reflector and array antennas and typical designs employ a periodic lattice of printed circuit elements etched on one or more dielectric layers [7][8][9][10][11][12][13][14][15][16]. These designs can be fully passive (fixed beam) or active with tunable devices to provide phase shifting (scanned beam) [7,17]. Most reflectarrays are designed with array lattice spacings of ~λ/2 and cr...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.