Alexander E. Martynyuk

Spiraphase-type reflectarrays based on loaded ring slot resonators

Reflective periodic arrays based on loaded ring slot resonators are analyzed. A full-wave mathematical model is developed and numerical results are presented. It is proven that the reflection angle for the normally incident circularly polarized wave can be effectively controlled by proper positioning of reactive loads in ring slot resonators. Analysis of the reflection characteristics of the Ka band one-layer reflectarray results in a conclusion that the incident wave can be effectively redirected in the directions determined by elevation angles as high as 65/spl deg/ with conversion coefficient better than -1.5 dB. It is also shown that the usage of the multilayer reflectarray leads to a considerable improvement in the reflection characteristics when it is compared with the one-layer reflectarray. The method of the waveguide simulator has been used to verify the developed mathematical model.

A Multilayer Circular Polarizer Based on Bisected Split-Ring Frequency Selective Surfaces

This letter presents a circular polarizer using a multilayer frequency selective surface based on split rings bisected by a metal strip. This geometry provides the advantages of both low cross-polarization level and low sensibility with respect to the incidence angle of the ring-based topology. To validate the proposed design, a four-layer prototype to operate in Ka-band has been designed, fabricated, and tested. Experimental results show that axial ratios lower than 3 dB are obtained for angles of incidence as high as 25 ° over the frequency range of 25.5-36.5 GHz.

Reflective antenna arrays based on shorted ring slots

Reflective arrays based on shorted ring slots are analyzed. It is proven that reflection angle for the normally incident circularly polarized wave can be effectively changed by proper situation of the conductive shorts. Thus, phased arrays with wide-angle scanning can be built using arrays of shorted ring slots.

Millimeter-wave amplitude-phase modulator

A millimeter-wave amplitude-phase modulator, using Foxs (polarization) principle of phase changing has been developed. Using this modulator, it is possible to perform the following types of phase modulation: binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), differential QPSK (DQPSK), /spl pi//4-DQPSK with peak phase error 5/spl deg/ (rms error: 2/spl deg/), and peak amplitude error 2% (rms error: 1%) in the frequency range of 36-37.5 GHz. The achievable switching time is less than 35 ns. A low level of insertion loss (1 dB) is achieved. The modulator is able to switch up to 25 dBm of RF power. This modulator can also be used for changing the amplitude of the output wave from 0 to -6 dB with an accompanying phase modulation less than 3/spl deg/. The modulator is suitable for use in high-speed millimeter-wave communication systems.

2-bit

The design and performance of a 2-bit p-i-n diode reflective X-band phase shifter are described. This phase shifter uses the spiraphase principle of phase changing. Benzocyclobutene-based bias circuits are used to decrease the insertion loss level and to reduce the fabrication costs. It has been proven that the phase shifter demonstrates insertion loss better than 0.5 dB in the frequency band from 9.75 to 11.5 GHz for all four phase states. The phase shifter is characterized by maximum phase errors of 11deg in the frequency band from 9.75 to 11.25 GHz. The measured switching time of the phase shifter is less than 150 ns

X

An active ring slot resonator loaded by switchable radial stubs is investigated. It is shown that this element can be used as the unit cell of a switchable reconflgurable frequency selective surface (RFSS). Equivalent circuit and full-wave mathematical models are obtained to evaluate the re∞ection characteristics of the RFSS based on this element. The possibility to obtain difierent resonant transmission frequencies is discussed. The mathematical model developed is used to design an X band RFSS capable of obtaining resonant frequencies at 9.65, 10.28, 10.83 and 12.05GHz. Commercially available RF MEMS switches are used to evaluate the efiect of the ofi-state capacitances over the response of the periodic structure. To validate the numerical simulation results, difierent active and passive diaphragms were designed, fabricated, and tested using the waveguide simulator. A good agreement between numerical and measured results was found.

-Band Reflective Waveguide Phase Shifter With BCB-Based Bias Circuits

Reconfigurable spiraphase-type reflectarrays based on ring slot resonators with switchable radial stubs are presented. The mathematical model of the infinite array was used to optimize the spiraphase-type element at 36.5 GHz. The optimization goals were to minimize the dissipative loss in the p-i-n diode switches and to reduce the cross-polarization radiation. The mathematical model of the finite array was then used to simulate the radiation characteristics of a reconfigurable reflectarray with 277 optimized elements for different scanning elevation angles θ_ο. The calculated aperture efficiencies were 0.42, 0.40, 0.36, 0.25, 0.16, and 0.12 for θ_ο equal to 0°, 20°, 30°, 40°, 45°, and 50°, respectively. For validation of the numerical simulations, three 277-element reflectarrays for fixed θ_ο of 0°, 20°, and 30° were designed. Metal strips and open circuits were used instead of the forward and reverse p-i-n diode states, respectively. These reflectarrays were then fabricated and tested, demonstrating aperture efficiencies equal to 0.41, 0.40, and 0.28 for θ_ο equal to 0°, 20°, and 30°, respectively. Measured characteristics agreed satisfactorily with theoretical predictions.

An Active Ring Slot with RF MEMS Switchable Radial Stubs for Reconfigurable Frequency Selective Surface Applications

This letter presents active dual-band frequency selective surfaces (AFSS) with close band spacing based on two switchable ring slots loaded by PIN diode switches. The close band response is achieved by splitting the outer ring slot, and then shifting upward its fundamental resonance beyond the resonance of the inner ring slot. The proposed AFSS can provide four states of operation including lower single-band, upper single-band, dual-band with close band spacing, and reflective mode. Experimental results based on the waveguide simulator show that a frequency ratio of 1.14, with insertion loss lower than 0.82 dB at resonant frequencies, is obtained in the X-band.

Reconfigurable Reflectarrays Based on Optimized Spiraphase-Type Elements

Wideband spiraphase-type reflective arrays based on loaded metal rings are analyzed. It is demonstrated that these arrays can redirect an incident circularly polarized wave in the directions determined by elevation angles up to 40/spl deg/ in a 2:1 frequency band with conversion loss less than 1 dB. A full-wave mathematical model has been developed to predict the characteristics of these arrays. This mathematical model was used for the synthesis of two arrays for X-Ku and K-Ka bands. Minimotor-driven elements have been designed and fabricated for the X-Ku band reflective array to test their switching velocity.

Active Dual-Band Frequency Selective Surfaces with Close Band Spacing Based on Switchable Ring Slots

A novel design of spiraphase-type reflective phased array is proposed. A full-wave mathematical model is developed to predict the scanning characteristics of this phased array. Numerical optimization of the geometry of the array element is performed. The scanning characteristics of the phased array with optimized elements are calculated. It is proven numerically that this passive array demonstrates a total loss better than -2 dB in the frequency band from 25 to 30.5 GHz within a scanning sector limited by elevation angles up to 28 degrees. The mathematical model developed has been experimentally verified with the help of the waveguide simulator.