Hamid Moghadas

A Dual-Band High-Gain Resonant Cavity Antenna With Orthogonal Polarizations

In this letter, a new study on the theory and the design of a dual-band dual-polarized high-gain resonant cavity antenna (RCA) is presented. The RCA includes two layers of orthogonal dipole arrays each located at a designated height above the ground plane of a microstrip patch antenna. A prototype is fabricated, and the measured results confirm the theory. The measured prototype has a lower-band gain of 19.6 dBi with the vertical polarization (V-pol) at 10 GHz and the upper band gain of 18 dBi with horizontal polarization (H-pol) at 11.6 GHz. The cross polarization (Xpol) is better than -27 dB at each band. It is demonstrated that the separation between the two bands is controlled arbitrarily.

MEMS-Tunable Half Phase Gradient Partially Reflective Surface for Beam-Shaping

A MEMS-tunable beam-shaping half phase-gradient (HPG) resonant cavity antenna (RCA) is presented. Traditionally, the full phase-gradient (FPG) partially reflective surface (PRS) is used in center-fed RCA for generating asymmetric off-broadside beams. Here, the novel configuration of HPG-PRS is offered with the advantages of faster real-time tracking and an improved scan profile compared to the FPG-PRS. A HPG-PRS is designed to scan 12 - 50° off broadside with frequency and also steer its beam for 69° at fixed frequency. Finally, the tunable PRS unit cell required for beam-steering in an RCA is realized using hybrid-integrated in-house developed RF-MEMS switches. These switches can be used to control the beam shape among: broadside, symmetric conical, and also an asymmetric single beam which is either frequency-scanned or steered at fixed frequency.

Bonding PMMA microfluidics using commercial microwave ovens

In this paper, a novel low-cost, rapid substrate-bonding technique is successfully applied to polymethyl methacrylate (PMMA) microfluidics bonding for the first time. This technique uses a thin intermediate metallic microwave susceptor layer at the interface of the bonding site (microchannels) which produces localized heating required for bonding during microwave irradiation. The metallic susceptor pattern is designed using a multiphysics simulation model developed in ANSYS Multiphysics software (high-frequency structural simulation (HFSS) coupled with ANSYS-Thermal). In our experiments, the required microwave energy for bonding is delivered using a relatively inexpensive, widely accessible commercial microwave oven. Using this technique, simple PMMA microfluidics prototypes are successfully bonded and sealed in less than 35 seconds with a minimum measured bond strength of 1.375 MPa.

Circularly Polarized Monopole L-Shaped Slot Antenna With Enhanced Axial-Ratio Bandwidth

A wideband circularly polarized antenna with L-shaped monopole slots and rotated parasitic patches has been proposed. The measured results show that the antenna has VSWR (<; 2) and axial-ratio (AR <; 3 dB) bandwidth of 64%. A novel wideband feeding structure has been used to excite the L-shaped slot and match the structure to 50-Ω impedance. The rotated parasitic patches are devised in the close proximity of slot to further enhance the circular polarization purity. Moreover, a Bazooka (sleeve) balun is used to eliminate the currents on the shield of coaxial feeding line and degrade AR. The antenna is relatively low-profile, low-cost, and easy to fabricate.

Half-phase-gradient Partially Reflective Surface for a reconfigurable dual-beam scanning cavity antenna

This paper presents a study on a novel reconfigurable orthogonally-polarized dual band high-gain Resonant Cavity Antenna (RCA). The RCA includes a Partially Reflective Surface (PRS) of printed slotted-patches with switch array across the slot which is designed based on the novel concept of half-phase-gradient PRS. The upper band has a broadside beam with V-polarization. The lower band is able to scan broadside and also 10-32° off broadside, depending on frequency and switch configuration with H-polarization.

Orthogonally-polarized dual-band MEMS-tunable double-slotted unit cell for reflectarray applications

This paper presents a single-layer MEMS-reconfigurable reflective unit cell that supports two bands (12 and 14 GHz) at two orthogonal polarizations. A pair of MEMS varactors is used for continuous and independent tuning of each band. The dynamic phase range of 310 degree is obtained with a maximum loss of 0.23 dB. The resultant reflectarray can have a separate scanned beam of given polarization at each of its two operating frequency bands. This unit cell has the requirements of Cognitive Radio and Satellite two-way communication.

Dual-band MEMS-tunable slotted-cross reflective unit cell with orthogonal polarization

This paper presents a single-layer single-sided dual-band MEMS reconfigurable reflectarray unit cell operating at 12 and 14 GHz. Each operating bands can continuously and independently be tuned using a pair of MEMS varactors at vertical and horizontal polarizations. A capacitance ratio of 2 provides more than 310 degree dynamic phase range with a very low loss. Therefore, the resulting reflectarray composed of this unit cell will have two beams that can independently be scanned at different operating frequencies and polarizations.

Dual-band dual-polarized high-gain Resonant Cavity Antenna

In this paper, a novel method is presented for designing a dual-band dual-polarized high-gain Resonant Cavity Antennas (RCA). The design procedure is also explained. The RCA includes two layers of dipole arrays each situated at a designed height above the ground plane of a microstrip patch antenna. The lower band has a gain of 22.1 dB with the vertical polarization (pol V) at 10.1 GHz and the upper band has a gain of 16 dB with horizontal polarization (pol H) at 11.9 GHz. The cross polarization is below 37 dB at each band.

Beam Reconfigurable Aperture Antenna by Stretching or Reshaping of a Flexible Surface

This letter presents a beam-reconfigurable superstrate antenna with a periodic flexible surface composed of an array of liquid-metal-filled microchannels inside a polymer. Two beam-reconfiguration techniques are used here: 1) stretching the surface along one axis where the radiation pattern depends on the elongation percentage; and 2) reshaping the surface to concave/convex where the pattern depends on surface state. Elongation and reshaping can split the broadside beam to two beams up to ±55° and ±58° off-broadside, respectively. This technique can be used as a simple low-cost alternative to electronic tuning that requires integration of an array of switches/varactors into the surface and hinder the fabrication of large-scale tunable surfaces and aperture antennas.

Integrated Magnetic Nanoinductors

This paper demonstrates the feasibility of the realization of on-chip inductors for use in microwave and millimeter-wave devices using ultraminiaturized on-chip vertical nanohelices. The inductors are constructed by depositing a thin film of closely packed, vertically aligned Nickel nanohelices. The film is fabricated using a CMOS-compatible glancing angle physical vapor deposition method. The resulting nanostructured inductors are characterized from 10 to 70 GHz and are found to have inductances of 6 pH/μm2, 60 times larger than conventional on-chip planar spiral inductors. A quality factor of three is measured and the results indicate that it continues to improve above 70 GHz, while inductance values remain relatively constant. The proposed nanostructured inductors can significantly reduce the chip area, and consequently the cost, of radio frequency and millimeter-wave integrated circuits. In addition, the nanostructured inductors offer significantly larger operation bandwidth than on-chip planar structures operating at frequencies above 100 GHz.