Dual-band shared aperture reflector/reflectarray antenna: Designs, technologies and demonstrations for nasa's ACE radar

Abstract

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...

Spaceborne Cloud and Precipitation Radars: Status, Challenges, and Ways Forward

“…Both concepts adopt advanced signal generation and processing schemes to achieve the desired radar sensitivities, resolutions and Doppler accuracies. In WiSCR (Hand et al., 2013; Racette et al., 2011) an AESLA for Ka band is combined to a W/Ka band reflectarray main reflector to enable use of CloudSat heritage technology at W band. The reflectarray technology enables collocated beams for all frequency bands with capability to support either fixed nadir or scanning W band beams, and wide swath at Ka band.…”

Using Active Remote Sensing to Evaluate Cloud-Climate Feedbacks: a Review and a Look to the Future

“…Beyond this, the cloud feedback decomposition into K c and C allows us to examine cloud-circulation coupling using longer data records. Furthermore, with the technological advances of the last decade [67][68][69][70][71][72][73] and our increasing understanding of how to exploit multi-instrument, multi-frequency active and passive synergy that began with the A-Train, the observational community is well positioned to address the aerosol-cloud-precipitation processes that presently drive the large uncertainty in ECS.…”

A compact feed horn with wide‐distributed operating bands of Ku/Ka/W

“…Thereby, the length of feed horn L is 70.5 mm according to formula (4) for conical horn, and the θ is about 9.7 according to formula (5). Secondly, determine the approximate range of two apertures' position D to couple TE 11 mode in common cavity, and the distance D1 is ranging from 16 to 19.2 mm (at 35 GHz), D2 is between 35.1 and 42 mm (at 16 GHz) according to formula (3). As for the final parameters of position D1 and D2 are set by parametric analysis according to different working frequency, the parametric analysis results about s22 and s33 are shown in Figure 2 With proper choice of parameter in simulation, it is possible to obtain capacitive surface impedance inside the horn at all two frequencies, and the final dimension of this feed horn are listed in Table 1.…”

“…To the best knowledge of us, there are mainly three common methods to realize multiband-characteristics for a reflector antenna: using multiple off-set horns or active electronically scanned arrays reflected by respective sub-reflectors, [2][3][4] adopting frequency selective surfaces (FSS) as its sub-reflectors [5][6][7] with two horns placed to both sides of it, and employing only a single multiband feed horn [8][9][10][11][12][13][14][15][16][17] in a reflector antenna. Comparing with the former solutions, designing a multiband horn comes to a more suitable candidate in the demand for simplicity.…”