A novel technique for designing ultrabroadband radar cross section (RCS) reduction surfaces using artificial magnetic conductors (AMCs) is proposed in this paper. This technique overcomes the fundamental limitation of the conventional checkerboard design where the reflection phase difference of (180±37)° is required to achieve 10-dB RCS reduction. Initially, a planar surface for broadband RCS reduction is designed with two properly selected AMCs in a blended checkerboard architecture. A 10-dB RCS reduction is observed for more than 83% of the bandwidth (3.9–9.45 GHz) with this blended checkerboard design. After modifying the blended checkerboard design using the proposed novel technique, the 10-dB RCS reduction bandwidth increased to 91% fractional bandwidth (3.75–10 GHz) as the criteria of (180 ± 37)° reflection phase difference is no longer required. Measured data show an excellent agreement between the predicted, simulated, and measured data. Bistatic performance of the surface at various frequencies is also presented. Key steps for designing ultrabroadband RCS reduction checkerboard surface are summarized.

Novel Design of Ultrabroadband Radar Cross Section Reduction Surfaces Using Artificial Magnetic Conductors

Microelectromechanical systems (MEMS) technology has the potential of replacing many of the radio frequency (RF) components used in to day's satellite communication systems. In many cases, such RF MEMS components would not only substantially reduce size, weight, and power consumption, but also promise superior performance when compared to that of current technologies. The benefits of MEMS technology be come more pronounced for switch matrices because there is a large number of switching elements and, therefore, any size and mass reduction would have large overall impact. Though there has been some controversy on the reliability and lifetime of RF MEMS switches, significant improvements have been made and RF switches with billions of switching cycles have been demonstrated. This article describes the potential applications of RF MEMS switch matrices in the satellite industry, where mass reduction and performance improvement is crucial.

RF MEMS Satellite Switch Matrices

Here, a new thermally actuated latching wideband RF microelectromechanical systems (MEMS) switch is presented. The switch employs two thermal actuators connected to two thin metal arms which serve as signal lines of coplanar waveguide switch. The actuators pull the thin arms sequentially, and latch the switch. The switch can be actuated on and off by using either short voltage or current pulses. Using a dielectric bridge (nitride) as an interface between the actuators and the thin arms, the RF circuitry is separated from DC actuators, allowing wide-band operation. The switch demonstrates an excellent wideband RF performance with an insertion loss of better than 0.3 dB up to 20 GHz and better than 0.8 dB up to 40 GHz. The return loss and isolation of the switch is better than 20 dB for the entire frequency band. The switch also has a very satisfactory repeatability with better than 0.1-dB variation in insertion loss and less than 1-dB variation in return loss and isolation at 30-dB level up to 6000 times switching cycles. The switch has been also successfully tested for RF power handling capability up to 40 dBm. The proposed switch has very simple RF structure which makes it an ideal candidate to be integrated in the form of more complex circuitry. An application of the proposed switch for a band selection network which is used in multiband transceivers has been presented here.

Thermally Actuated Latching RF MEMS Switch and Its Characteristics

Microwave signal filtering is a fundamental and central functionality in radio-frequency (RF) systems. Underpinned by advanced integrated photonics technologies, emerging integrated microwave photonic (IMWP) filter platforms enable reconfigurable and widely tunable RF signal filtering functionalities that were unattainable using conventional electronics while also exhibiting superior features in terms of compactness, light weight, stability, low power consumption, and low latency. This paper presents a comprehensive review of the principles, architectures, and performance of IMWP filters. We highlight recent advances of IMWP filters enabled by on-chip nonlinear optics, RF-interference technology and emerging integration platforms, with an emphasis on the RF performance which is critical for their usability in real-world applications. We conclude with a perspective on future research challenges and new possibilities for IMWP filters.

Integrated microwave photonic filters

A vertically polarized substrate-integrated waveguide (SIW)-fed endfire metasurface antenna array is proposed for wideband operation. Each of the metasurfaces consists of $3\times 3$ rectangular patches and is printed on the two surfaces of a single-layered substrate with a thickness of $0.16\lambda _{0}$ (where $\lambda _{0}$ is the wavelength at 32.65 GHz in free space). The antenna is fed at one side of metasurface by an open-end SIW for wideband endfire radiation. The proximity-coupled interdigital strips are introduced between the SIW and metasurface for fault-tolerant coupling. The wideband operating mechanism is revealed by studying the propagation mode and multiple resonant modes of metasurface. To verify the proposed antenna, a $1\times 4$ array is presented with uniform excitation including two SIW Y junctions and an SIW T junction. Moreover, the connected SIW Y junction improved the impedance matching at the low frequencies based on the cavity mode analysis. The proposed design shows that the measured impedance bandwidth (10 dB return loss) is 26.6–38.7 GHz (37%) with the achieved gain of 9.1–13.8 dBi.

Wideband Substrate-Integrated Waveguide-Fed Endfire Metasurface Antenna Array

This paper proposes new solutions for implementing wideband large switch matrices. These solutions are based on crossbar and L-shaped topologies. This paper introduces a high-performance wideband switch cell to build up scalable NtimesN switch matrices and gives an account of the design, fabrication, and characteristics of the switch cell and a 3times3 crossbar switch matrix. The chosen design procedure is seen to be appropriate since it produces valid measured results. In addition, this paper presents an RF microelectromechanical systems L-shaped switch matrix, which indicates less variation of characteristics for certain types of connectivity. It also demonstrates that for a 4times4 switch matrix, there is a 50% improvement in insertion loss and phase-shift variation.

Scalable RF MEMS Switch Matrices: Methodology and Design

A cost-effective way of reducing sidelobe level and improving front-to-back ratio of the substrate integrated waveguide H-plane horn antennas is proposed in this letter. Metal rectangular patches and dielectric loading are integrated to the aperture of the horn antenna, resulting in an increased gain, narrow E-plane beamwidth, and reduced sidelobes and backward radiation. The overall dimensions of the fabricated antenna are 42 × 18.6 mm2 . The antenna works at 22.7 GHz with a measured gain of 10.1 dBi. A single substrate and a 3.5-mm connector with a transition pin are used to ensure the lowest cost for mass production.

Substrate Integrated Waveguide H-Plane Horn Antenna With Improved Front-to-Back Ratio and Reduced Sidelobe Level

By taking advantage of the MEMS contact type switches in tunable filters, a new method that allows both the adjustment of resonant frequency and the input/output and inter-resonator coupling is presented A three-pole filter capable to switch to three different states is designed using this method The measured center frequency for each state is 8, 9, and 10 GHz (25% tuning) with a constant bandwidth of around about 1 GHz The measured insertion loss of the filter is better than 35 dB for all three states

RF MEMS Switchable Interdigital Bandpass Filter

This paper presents a simple, low-cost, hours-long fabrication method for microwave waveguide components of high RF performance The technique combines 3-D-printed configurations with liquid metal waveguide structures As a demonstration, a fused deposition modeling multimaterial 3-D consumer-grade printer and liquid gallium were used A conductive polylactic acid (PLA) waveguide flange was 3-D printed along, in-one-go, with standard PLA for the rectangular waveguide liquid metal enclosures Microwave WR62 waveguides, resonators, and filters operating in Ku-band were designed, fabricated, and tested The RF performance of the fabricated waveguide devices is in agreement with the simulations demonstrating better than 129 dB/m attenuation in the waveguide and better than 1000 $Q$ -factor for the resonator and the filter at 13 GHz The fabricated devices demonstrate a new option of an economical fabrication technology for high RF performance microwave waveguide-based devices that can be delivered in hours-time, anywhere, anytime with minimal equipment deployment and investment

Low-Cost Ku-Band Waveguide Devices Using 3-D Printing and Liquid Metal Filling

This paper presents a novel approach to implement RF MEMS large size switch matrices. The concept is based on the implementation of a crossbar switch matrix and the introduction of unique switch cells that can be easily used to expand the matrix size. A six-mask fabrication process is adapted to fabricate the proposed four-port switch cell as well as the switch matrix samples. The switch cell has two operational states: thru and turn. This allows the cell to be easily integrated in the form of a crossbar switch matrix. Novel series contact cantilever beams have been used to implement the entire structure. The measured results for the entire switch cell show excellent insertion loss of 0.5dB, return loss of better than −20dB and isolation of −25dB for the thru path. The turn state of the switch shows a good performance of 0.4dB insertion loss, −18dB return loss and better than −25dB isolation for the frequency band of interest. A 3×3 switch matrix is implemented that shows 98% size reduction in comparison with the previously reported RF MEMS switch matrices.

King Yuk Chan

Papers

Scalable RF MEMS Switch Matrices: Methodology and Design

Substrate Integrated Waveguide H-Plane Horn Antenna With Improved Front-to-Back Ratio and Reduced Sidelobe Level

RF MEMS Switchable Interdigital Bandpass Filter

Low-Cost Ku-Band Waveguide Devices Using 3-D Printing and Liquid Metal Filling

Monolithic crossbar MEMS switch matrix