For dual-band dual-polarized synthetic aperture radar (SAR) applications a compact low-profile design is investigated. The operating frequencies are in the L and C-bands, centered about 1.275 and 5.3 GHz, respectively. Since the C-band frequency is larger by a factor of four, its array elements and inter-element separations are smaller by the same ratio. Thus, to allow similar scan ranges for both bands, the L-band elements are selected as perforated patches to enable the placement of C-band elements within them. Stacked-patch configurations were used to meet the bandwidth requirements, especially in the L-band. The C-band element was designed numerically, but the perforated L-band one required final experimental optimization. Also, in the latter case of L-band, a balanced transmission line feed was used to minimize cross polarization. For the C-band elements, slot coupling was used and, to simplify the feed, symmetric parasitic slots were incorporated to minimize cross polarization. No vertical connections were utilized, and electromagnetic couplings resulted in a compact low-profile design, with an electrically and thermally symmetric geometry.

Dual-band dual-polarized perforated microstrip antennas for SAR applications

The growing complexity of satellite and mobile communication systems means that there are increasing needs for antenna arrays with multiple-beam capability. Conventional beamforming-network (BFN) configurations can be realized by different types of transmission lines, such as a microstrip line or waveguide. However, each of these has its own obvious defects. As part of a new generation of high-frequency integrated circuits, called substrate integrated circuits (SICs), substrate-integrated-waveguide (SIW) technology combines the benefits of both planar transmission-line and non-planar-waveguide technologies. It presents an excellent solution for the design and implementation of high-frequency beamforming networks, including for use at millimeter wavelengths. This paper overviews the state-of-the-art of substrate-integrated-waveguide techniques in the design and realization of innovative beamforming networks, and multibeam antenna arrays for low-cost satellite and mobile systems. Different classes of substrate-integrated-waveguide-based structures are theoretically and experimentally studied and demonstrated, to offer unprecedented performance and opportunities for specific space-and ground-based applications.

Substrate-Integrated-Waveguide Beamforming Networks and Multibeam Antenna Arrays for Low-Cost Satellite and Mobile Systems

In this letter, a double layer Blass matrix based on substrate integrated waveguide (SIW) technology is proposed. A prototype of 4 times 16 Blass matrix is implemented, fabricated and measured with SIW slot antennas installed at the output ports. The measured data are in good agreement with the simulated results. At 16.1 GHz, the measured Side Lobe Level of all individual beams is less than -12 dB. Compared with the conventional waveguide construction, this type of Blass matrix possesses the properties of lower cost, easier fabrication and low profile.

A Double Layer Substrate Integrated Waveguide Blass Matrix for Beamforming Applications

A quasi-planar leaky-mode antenna employing the second higher order leaky mode of even symmetry in its leaky-wave regime has been proposed for a new antenna configuration consisting of a microstrip and a coplanar waveguide (CPW) on both sides of the substrate. The new antenna, also known as the micro-CPW antenna, is directly fed by a CPW line without matching circuit. One particular K-band antenna of 36 mm long [about 2.7 free-space wavelengths (/spl lambda//sub 0/) at 22.1 GHz] shows 5.3% impedance bandwidth for VSWRs less than 2.0 for frequencies between 21.927-23.110 GHz, 11.0-dB antenna gain, and 90.02% efficiency. Detailed analyses show that the dual-beam antenna is linearly polarized along two slanted lines, which lie in the longer axes of the ellipses that approximate the radiation contours. Both theoretical and experimental data for the micro-CPW antenna agree very well for the particular design. The proposed micro-CPW antenna is suitable for active integrated antenna integration at higher microwave and millimeter-wave frequencies.

https://ir.nctu.edu.tw:443/bitstream/11536/30747/1/000086498800020.pdf

A dual-beam micro-CPW leaky-mode antenna

A novel design method for lossy Blass matrix beam-forming networks is presented. Compared to those formerly developed (W.R. Jones and E.C. DuFort, 1971), (S. Mosca et al., 2002), the new method allows the design of such circuits to generate an arbitrary number of simultaneous beams oriented in arbitrary positions. This is obtained by means of an equivalent circuit approach to compute the transmission parameters of the Blass matrix. The method has been applied to the design of a specific multi-beam waveguide application, which required the development and characterization of a novel waveguide cross coupler. Experimental results confirm the accuracy of the method showing high performance for all beams in terms of beam position, side lobe level and efficiency.

A novel design method for Blass matrix beam-forming networks

The authors describe the design process and test results of a dual beam array antenna model. The objective of this ESA funded program is to study the realization of dual beams in a waveguide slotted array of the ERS-1 SAR type (10 m*1 m). The experimental model is 1 m*1 m and comprises 24 slotted waveguides and a Blass matrix feed network. The synthesis and design of the array and Blass matrix is described. Calculated and measured results of the experimental model are presented. The key component in the Blass matrix is a crossguide coupler. The authors present a novel design of a crossguide coupler which makes it possible to realize very tight coupling. >

http://ieeexplore.ieee.org/iel3/1216/3116/00098301.pdf

A dual beam slotted waveguide array antenna for SAR applications

The application of a multibeam slotted waveguide antenna for a synthetic aperture radar (SAR) in space is discussed. The feasibility of a dual-beam SAR antenna using ERS-1 technology has been shown. Some predicted and measured results of a dual-beam slotted waveguide antenna are presented and a very good agreement has been found. A multiport scattering matrix for the feed network has been derived for both dual and triple-beam antenna designs. >

M. Bonnedal

Papers

A dual beam slotted waveguide array antenna for SAR applications

Multiple beam slotted waveguide antenna for spaceborne synthetic aperture radar