This paper presents design and performance of a unique, low cost, miniature planar all MMIC W-band transceiver. The transceiver incorporates a planar 4-element circularly polarized patch antenna, a monopulse comparator, two receiver channels, one for the sum and the other for a selectable difference in either azimuth or elevation. Two PIN diode switches provide the TR and difference channel switching. Each receiver has a balanced LNA, an image rejectionhmage enhancement subharmonic mixer and an IF amplifier. Test circuits are included for system calibration and verification. The double sided transceiver uses an optimal arrangement of quartz, alumina, and LTCC for an overall size less than 1 inch diameter and 0.25 inch thick. The antenna cross pole isolation is typically 15 dB with a monopulse null depth of 25 dB. The receiver gain is 30 dB with a 25 dB image rejection. Introduction:
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...
This paper describes a novel dual-frequency shared aperture Ka/W-band antenna design that enables wide-swath imaging via electronic scanning at Ka-band and is specifically applicable to NASA's Aerosol, Cloud and Ecosystems (ACE) mission. The innovative antenna design minimizes size and weight via use of a shared aperture and builds upon NASA's investments in largeaperture reflectors and high technology-readiness-level (TRL) W-band radar architectures. The antenna is comprised of a primary cylindrical reflector/reflectarray surface illuminated by a fixed Wband feed and a Ka-band Active Electronically Scanned Array (AESA) line feed. The reflectarray surface provides beam focusing at W-band, but is transparent at Ka-band. I.
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