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Ultra-wideband step notch array using stripline feed

Published in:
IEEE Antennas and Propagation Society Int. Symp., 2007 Digest, 9-15 June 2007, pp. 3361-4.

Summary

Electronically scanned array (ESA) antennas capable of efficiently radiating over an octave of bandwidth provide system designs with more flexibility in multiple mode operation. Communication and radar bands occupy different frequency allocations and the growing research in Ultra-Wideband (UWB) communications make the use of a single ESA to cover these frequencies an area of interest. Array antennas constructed of tapered-slot antennas and TEM horns have been investigated and shown to operate successfully over an octave bandwidth. These antennas use vertical feeds which make them optimal for brick architectures, but less than desirable for tile architectures. Conventional notch antennas require a feed extending vertically away from the notch antenna which makes a flat 2-D connection between antennas difficult. In this work an Ultra-Wideband Step Notch Array (UWSNA) was designed for ESA applications. The array operates over a 6-12 GHz range using a flat, tile-based 2-D feed network making this array optimal for conformal applications with a minimum of vertical distance. Simulation results and measurements on a small prototype demonstrate the concept.
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Summary

Electronically scanned array (ESA) antennas capable of efficiently radiating over an octave of bandwidth provide system designs with more flexibility in multiple mode operation. Communication and radar bands occupy different frequency allocations and the growing research in Ultra-Wideband (UWB) communications make the use of a single ESA to cover these...

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Design of overlapped subarrays using an RFIC beamformer

Published in:
IEEE Antennas and Propagation Society Int. Symp., 2007 Digest, 9-15 June 2007, pp. 1791-4.

Summary

Electronically scanned arrays require a minimum number of controls, Nmin, given by the number of orthogonal beams that fill a prescribed scan sector. Most practical antenna arrays require considerably more than Nmin control elements, but overlapped subarray architectures can approach this theoretical limit. Figure 1 shows a block diagram of an overlapped subarray architecture. The overlapped subarray network produces a flattopped sector pattern with low sidelobes that suppress grating lobes outside of the main beam of the subarray pattern. Each radiating element of the array is connected to multiple subarrays, creating an overlapping geometry. It is possible to scan one beam, or a fixed set of contiguous beams, over the main sector of the subarray with a set of Nmin phase shifters. Alternatively, digital receivers can be connected to the Nmin subarrays and multiple simultaneous beams can be formed digitally. Digital subarray architectures using a combination of element level phase shifters and subarray level receivers makes it possible to scan multiple beam clusters over all space. The conventional approach to the design and manufacturing of the overlapped subarray network shown in Figure 1 is challenging and costly due to the complexity of the microwave network. However, the design of the overlapped subarray beamformer using Radio Frequency Integrated Circuits (RFIC) represents a novel approach for implementing an efficient trade-off between the agility and capability of fully digital arrays and the cost effectiveness of analog arrays.
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Summary

Electronically scanned arrays require a minimum number of controls, Nmin, given by the number of orthogonal beams that fill a prescribed scan sector. Most practical antenna arrays require considerably more than Nmin control elements, but overlapped subarray architectures can approach this theoretical limit. Figure 1 shows a block diagram of...

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SiGe IC-based mm-wave imager

Published in:
2007 IEEE Int. Symp. on Circuits and Systems, 27-30 May 2007, pp. 1975-1978.

Summary

Millimeter-wave radiation and detection offers the possibility of detecting concealed weapons. Passive imaging measures the mm-wave radiation emitted from target objects. A passive mm-wave imager and the designs affecting the overall system performance are discussed. With low power receiver architecture and SiGe ICs, a focal plane based full staring array is feasible and can provide a high thermal resolution, ~1.1K at >10Hz frame rate.
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Summary

Millimeter-wave radiation and detection offers the possibility of detecting concealed weapons. Passive imaging measures the mm-wave radiation emitted from target objects. A passive mm-wave imager and the designs affecting the overall system performance are discussed. With low power receiver architecture and SiGe ICs, a focal plane based full staring array...

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Design considerations and results for an overlapped subarray radar antenna

Summary

Overlapped subarray networks produce flattopped sector patterns with low sidelobes that suppress grating lobes outside of the main beam of the subarray pattern. They are typically used in limited scan applications, where it is desired to minimize the number of controls required to steer the beam. However, the architecture of an overlapped subarray antenna includes many signal crossovers and a wide variation in splitting/combining ratios, which make it difficult to maintain required error tolerances. This paper presents the design considerations and results for an overlapped subarray radar antenna, including a custom subarray weighting function and the corresponding circuit design and fabrication. Measured pattern results will be shown for a prototype design compared with desired patterns.
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Summary

Overlapped subarray networks produce flattopped sector patterns with low sidelobes that suppress grating lobes outside of the main beam of the subarray pattern. They are typically used in limited scan applications, where it is desired to minimize the number of controls required to steer the beam. However, the architecture of...

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Circuit-fed tile-approach configuration for millimeter-wave spatial power combining

Published in:
IEEE Trans. Microw. Theory Tech., Vol. 50, No. 1, Part 1, January 2002, pp. 17-21.

Summary

In this paper, a circuit-fed spatially combined transmitter array is described for operation at 44 GHz. The array contains 256 elements where each element consists of a monolithic-microwave integrated-circuit amplifier and a circularly polarized microchip patch antenna. The array is constructed using 16-element tile-approach subarrays. Each subarray is a two RF-level (three-dimensional) multichip module containing integrated microstrip patch antennas. The basic construction of the transmitter array resembles tile-approach phased arrays; however, the implementation has been tailored for the power-combining application. The peak performance at 43.5 GHz is equivalent isotropic radiated power of 40.6 dBW (11570 W), effective transmitted power (Peff) of 5.9 W, dc-to-RF efficiency of 7.3%, and system gain of 35 dB.
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Summary

In this paper, a circuit-fed spatially combined transmitter array is described for operation at 44 GHz. The array contains 256 elements where each element consists of a monolithic-microwave integrated-circuit amplifier and a circularly polarized microchip patch antenna. The array is constructed using 16-element tile-approach subarrays. Each subarray is a two...

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Comparison of two flat reflector-type designs for dual-polarization, dual-band operation

Published in:
IEEE Antennas and Propagation Society Int. Synp. 2001 Digest, Vol. 2, 8-13 July 2001, pp. 288-291.

Summary

The parabolic reflector remains an essential antenna for high-gain applications. This is a result of its desirable characteristics based on geometric optics. These include relative frequency independence for sufficiently large apertures and high aperture efficiency. However, the parabolic reflector occupies a large volume. This may be aesthetically unappealing on the sides of buildings and structures. Also, from a mobile user perspective, a desirable characteristic is having a large aperture during operation while having a small volume when packed away and not in use. The parabolic reflector is typically constructed of multiple petals for mobile uses, but it does not pack into as small a volume as a flat, thin antenna would due to the curvature of the paraboloid. Therefore, the primary goal of the antennas studied in this work is developing flat reflector antennas to utilize the advantages of large reflector apertures while remaining capable of packing into a small volume. In addition, system requiremenls dictated dual-band, dual-polarized operation. Two flat reflectors are compared: a reflectarray and a zoned reflector. While each design is inherently narrow-band, methods of achieving dual-band operation were employed.
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Summary

The parabolic reflector remains an essential antenna for high-gain applications. This is a result of its desirable characteristics based on geometric optics. These include relative frequency independence for sufficiently large apertures and high aperture efficiency. However, the parabolic reflector occupies a large volume. This may be aesthetically unappealing on the...

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Accurate modeling of dual dipole and slot elements used with photomixers for coherent terahertz output power

Summary

Accurate circuit models derived from electromagnetic simulations have been used to fabricate photomixer sources with optimized high-impedance antennas. Output powers on the order of 1 uW were measured for various designs spanning 0.6-2.7 THz. The improvement in output power ranged from 3 to 10 dB over more conventionally designed photomixers using broad-band log-spiral antennas. Measured data on single dipoles, twin dipoles, and twin slots are in good agreement with the characteristics predicted by the design simulations.
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Summary

Accurate circuit models derived from electromagnetic simulations have been used to fabricate photomixer sources with optimized high-impedance antennas. Output powers on the order of 1 uW were measured for various designs spanning 0.6-2.7 THz. The improvement in output power ranged from 3 to 10 dB over more conventionally designed photomixers...

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MEMS microswitches for reconfigurable microwave circuitry

Summary

The performance is reported for a new microelectromechanical structure (MEMS) cantilever microswitch. We report on both dc- and capacitively-contacted microswitches. The dc-contacted microswitches have contact resistance of less than 1 ohm, and the RF loss of the switch up to 40 GHz in the closed position is 0.1-0.2 dB. Capacitively-contacted switches have an impedance ratio of 141:1 from the open to closed state and in the closed position have a series capacitance of 1.2 pF. The capacitively-contacted switches have been measured up to 40 GHz with S(21) less than -0.7 dB across the 5-40 GHz band.
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Summary

The performance is reported for a new microelectromechanical structure (MEMS) cantilever microswitch. We report on both dc- and capacitively-contacted microswitches. The dc-contacted microswitches have contact resistance of less than 1 ohm, and the RF loss of the switch up to 40 GHz in the closed position is 0.1-0.2 dB. Capacitively-contacted...

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Combining-efficiency X-band spatial power-combined array using a multilayered packaging architecture

Author:
Published in:
IEEE Trans. Microw. Theory Tech., Vol. 48, No. 10, October 2000, pp. 1769-1771.

Summary

The design of a high combining-efficiency spatial power-combined array is described in this paper. A multilayered stacked stripline architecture enables a compact stable design. An array incorporating antenna active impedance and proper amplifier matching is measured with a combining efficiency of 87%, radiating 6.8 W of an available 7.8 W into the ideal uniformly illuminated array directivity at 10.1 GHz.
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Summary

The design of a high combining-efficiency spatial power-combined array is described in this paper. A multilayered stacked stripline architecture enables a compact stable design. An array incorporating antenna active impedance and proper amplifier matching is measured with a combining efficiency of 87%, radiating 6.8 W of an available 7.8 W...

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MEMs microswitch arrays for reconfigurable distributed microwave components

Summary

A revolutionary device technology and circuit concept is introduced for a new class of reconfigurable microwave circuits and antennas. The underlying mechanism is a compact MEMs cantilever microswitch that is arrayed in two-dimensions. The switches have the ability to be individually actuated. By constructing distributed circuit components from an array, the individual addressability of the microswitch provides the means to reconfigure the circuit trace and, thus, provides the ability to either fine-tune or completely reconfigure the circuit element's behavior. Device performance can be reconfigured over a decade in bandwidth in the nominal frequency range of 1 to 100 GHz. In addition, other circuit-element attributes can be reconfigured such as instantaneous bandwidth, impedance, and polarization (for antennas). This will enable the development of next-generation communication, radar and surveillance systems with agiIity to reconfigure operation for diverse operating bands, modes, power levels, and waveforms.
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Summary

A revolutionary device technology and circuit concept is introduced for a new class of reconfigurable microwave circuits and antennas. The underlying mechanism is a compact MEMs cantilever microswitch that is arrayed in two-dimensions. The switches have the ability to be individually actuated. By constructing distributed circuit components from an array...

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