Alina-Cristina Bunea

A tunable microwave slot antenna based on graphene

The paper presents the experimental and modeling results of a microwave slot antenna in a coplanar configuration based on graphene. The antennas are fabricated on a 4 in. high-resistivity Si wafer, with a ∼300 nm SiO2 layer grown through thermal oxidation. A CVD grown graphene layer is transferred on the SiO2. The paper shows that the reflection parameter of the antenna can be tuned by a DC voltage. 2D radiation patterns at various frequencies in the X band (8–12 GHz) are then presented using as antenna backside a microwave absorbent and a metalized surface. Although the radiation efficiency is lower than a metallic antenna, the graphene antenna is a wideband antenna while the metal antennas with the same geometry and working at the same frequencies are narrowband.

Diode modeling for milimeter wave applications based on co-simulation technique

This paper addresses the modeling and the co-simulation technique of millimeter wave Schottky diode for millimeter wave applications such as rectennas and detectors. In order to provide accurate simulation models a co-simulation technique based on the combination of full-wave electromagnetic simulations and non-linear circuit modeling is proposed. The obtained results demonstrates a good correlation between simulation and measurement and the proposed methodology can be used for designing high-performing circuits without expensive and time consuming prototyping.

Magnetic scanning of the radiation characteristic of a CRLH CPW antenna

The paper presents the results concerning the radiation characteristic scanning of a ferrite supported resonating CPW antenna based on CRLH (Composite Right / Left-Handed) transmission lines. The scanning effect is obtained by magnetically polarizing the ferrite substrate. Data obtained by simulation with a suitable microwave software indicate an azimuthal characteristic deviation of ± 9.780 at a working frequency f = 13 GHz for a variable magnetic biasing field between 0 T and 0.16 T. This result is in very good agreement with the experimental data showing a characteristic displacement of +120 … −100.

Scanning radiation characteristic of a CRLH CPW ferrite supported antenna

The paper deals with the radiation characteristic scanning of a ferrite supported resonating CPW antenna based on CRLH (Composite Right/Left-Handed) transmission lines. The scanning effect is obtained by magnetically polarizing the ferrite substrate with a magnetic biasing field which varies between 0 T and 0.16 T. Data obtained by simulation with a suitable microwave software indicate an azimuthally characteristic deviation of ± 9.87° at a working frequency of 13 GHz, in very good agreement with the experimental results showing an azimuthally characteristic deviation of 10°.

LTCC Microstrip Parasitic Patch Antenna for 77 GHz Automotive Applications

A microstrip parasitic patch antenna consisting of four parasitic patches, fed by one active patch, with a stripline input, is presented in this paper. The antenna was designed for the Low Temperature Co-fired Ceramics (LTCC) technology and shows very good matching and radiation behavior in the 77 GHz band, with measured reflection losses lower than - 10 dB between 75.175-80.6 GHz and below - 40 dB at 77 GHz. Simulation results show a gain higher than 8 dBi in the 76-81 GHz frequency range, with a radiation efficiency higher than 80%. A separate structure, based on direct conversion (video) receiver was designed and fabricated for radiation pattern measurements. The E and H planes at 77 GHz were measured and show good agreement with simulation results, with a computed gain of 8.2 dBi for the direction normal to the patches.

160 GHz silicon micromachined folded slot antenna array

This paper describes the design, electromagnetic (EM) modeling and experimental results obtained for a 160 GHz double folded slot antenna array processed through silicon micromachining. Initial simulations showed reflection losses (RL) of -17 dB at 160 GHz and a fractional bandwidth of ~18.7% (with RL<;-10dB between 148.65 GHz and 178.59 GHz). The simulated directivity was larger than 4 dBi in the working frequency band and ~6.8 dBi at 160 GHz. The structure was processed through deep reactive ion etching (DRIE), and resulted in a thinner substrate than designed. The experimental results for this thinner substrate of about 140 μm showed a ultra wideband behavior, with measured RL<;-10dB for almost the whole 140-210 GHz band and -17 dB at 160 GHz. The free space transmission parameter was measured and the results were compared with the simulated directivity showing a frequency shift of the curve, but otherwise a very good agreement in the trend of the two curves.

Ground speed Doppler sensor with a micromachined double folded slot antenna

This paper presents a new concept for the Doppler sensor for true ground speed measurement. The basic principle is based on a membrane supported double folded slot antenna operating at 77 GHz with a bidirectional radiation characteristic and a Schottky diode for signal mixing and Doppler frequency shift extraction. The sensor was fabricated using silicon micromachining. A dedicated setup was used for the proof of concept and the Doppler spectrum was recorded for different moving surface speeds. The measurement error is less than 2 % for speeds between 1 and 3 m/s.

220 GHz membrane supported folded slot antenna array

This paper presents the design, electromagnetic modeling, fabrication and characterization of a Folded Slot Antenna Array (FSAA) working at 220 GHz. The structure was processed on a 2.1 μm thick SiO2/Si3N4 dielectric membrane released through deep reactive ion etching (DRIE) of low-resistivity (p = 10 Ω ·cm) silicon. The antenna was characterized on wafer, showing good agreement with simulated results. The measured calibrated gain is 5.5 dB at 220 GHz, and is greater than 0 dB between 200-250 GHz.

Micromachined front-end for 60 GHz applications

In this paper we present the electromagnetic modeling, fabrication and experimental results of a on-chip 2×1 folded slot dipole antenna array manufactured through silicon micromachining, working in the 60 GHz band. The measurements are in very good agreement with the simulations and demonstrate a large working band of ~20% (54-65 GHz) for a return loss better than 10 dB.

94 GHz substrate integrated waveguide fed antenna in LTCC technology

This paper presents a novel 94 GHz parasitic antenna array with a substrate integrated waveguide feed. The antenna array was designed for a six tape low-temperature co-fired ceramic process, offering the opportunity of easy integration with other passive and active components. Simulations have shown a high directivity of 8.2 dBi at the central operating frequency of 94 GHz, with reflection losses lower than -10 dB for a 4.75 GHz bandwidth.