White Paper US Naval Research on Phase Array Antenna Systems
White Paper US Naval Research on Phase Array Antennas
A 20-GHZ Active Receive Phased Array Antenna for
Navy Surface Ship Satellite Communications Applications
M. Chen*,
D. E. Riemer, D. N. Rasmussen, J. E. Wallace, H. J. Redd,
R. C. Ettorre,
D. B. Peterson, R N. Bostwick, and G. E. Miller
Boeing Phantom Works
Seattle,
WashingtonINTRODUCTION. Many current shipboard antennas, particularly those required for satellite coverage, are highly directional and require precise steering with heavy, expensive pedestals. The negative result is that they are expensive, add weight aloft compromising ship stability and add large radar reflecting surfaces that can dominate the radar cross section of the ship. The scope of this research effort was to design, fabricate and test a 255-element proof-of-concept active receive phased array antenna to demonstrate the practicality and performance of a two-dimensional electronically scanned phased array antenna for surface ship applications. The successful demonstration of thisantenna reduced the risk associated with the current development of a full-scale, low signature SATCOM antenna.
PERFORMANCE GOALS. The RF performance and the physical parameter goals of the antenna system are listed below.
Frequency: 20.2-21.2 GHz
Number of elements: 255
Scan Range: 0-50 deg elevation, Omni directional in azimuth
(full-scale): greater than 10.6 dBK at 50 deg of scan (requires 4096 elements)
Thickness: less
than 2 inches
Cooling: forced air
ANTENNA SYSTEM ARCHITECTURE. A cross section of the array architecture is shown in figure 1. The architecture is based upon previous internal and contracted work [1,2]. The RF energy is incident on the aperture from the right. A multi-layer wide angle mpedance matching (WAIM) structure provides environmental protections, a low loss aperture match and low axial ratio over the scan volume [3]. The radiating elements are dielectrically loaded, circular waveguides arranged in a triangular lattice that prevents grating lobe formation over the array scan volume. A pair of orthogonal, linearly polarized waveguide probes couple the RF energy from the waveguide to the receive module active electronics. The two linearly polarized components of the incident RF energy are then low noise amplified and combined using a hybrid combiner. Switches in the hybrid permit selection of right hand or left hand circular polarization. The two low noise amplifiers (LNA) and the hybrid are realized on a single monolithic microwave integrated circuit (MMIC). The combined signal is then low noise amplified and phase shifted. The second stage LNA and 4-bit phase shifter are realized on a second MMIC. Asilicon CMOS ASIC provides the interface between the beam steering control computer and the module phase shifter. The low noise amplified and phase shifted signal transitions out of the module onto a multilayer wiring board WLWB). A multi-conductor elastomeric connector is used to connect the dc power, RF output signal, clock and data traces of 'the module to those of the MLWB. The RF layer in the MLWB consists ofmultiple Wilkinson combiners that combine the 255 module outputs into a single RF output. Control of the modules is accomplished using digital sigmls on the data and clock lines to load the five control bits (four phase shift bits and one polarization select bit). The two MMIC chips and the CMOS ASIC are housed in a hermetic ceramic housing. Because the MMICs dissipate up to 200 mW, careful thermal design was necessary to ensure the MMIC chip back temperature did not exceed temperatures that would decrease the reliability of the devices [4]. The thermal energy generated in the MMICs is conducted through the module housing and the MLWB to a plate that also provides the necessary pressure to the elastomeric connectors to ensure reliable dc, logic and RF connection. The thermal design provides for a maximumof 3VC of temperature rise from the cooling air on the back of the pressure plate to the h4MIC chip back.
SUMMARY. In this paper we have described the successful development of an innovative and high performance active receive phased array antenna for use with satellite communications systems on the next generation of Navy surface ships. Development is now underway for delivery of a full-scale (4096 element, G/T=I 0.6 dEK) antenna, based upon the described technology, in mid 2000.
ACKNOWLEDGEMENTS. This work was performed under Navy SPAWAR contract N66001-97-C- 6002 (Ron Major, technical representative). Previous support by the Air Force Research Laboratory (John Turtle, technical representative) is also acknowledged.
REFERENCES:
[I] EHF Low Cost Active Phased Array, Contract F30602-95-C-0051 Final Report, US Air Force Research Laboratory Antenna Technology Branch, AFRL/SNHA, Hanscom AFB, MA, May 1998.
[2] E. J. Vertatschitsch, G.W. Fitzsimmons, “Boeing Satellite Television Airplane Receiving System
(STARS) Petjormance,” International Mobile Satellite Conference, Ottawa, Canada, June 6-8, I995[3] B. J. Lambelty, W. P. Geren, S. H. Goodman, G. E. Miller, K. A. Dallabetta, “ Wide-Angle Impedance Matching Suifacesfor Circular Waveguide Phased Array Antennas with 70-Degree Scan
