Stefan Simion

MEMS optimization using genetic algorithms

Using genetic algorithms, an original method for MEMS optimization is proposed in This work. The optimized MEMS device should provide both minimum switching time and minimum equivalent capacitance, so the highest operating frequency is obtained. By analyzing the results obtained on the switching time for different operating voltage and geometrical configurations, it is important to mention that by using GA, the MEMS behavior is in good agreement with the expected results obtained by classical means.

Silicon Supported Microwave Zeroth-order Resonance Antenna on Metamaterial Approach

This paper presents the results in modeling, technological realization and measurements of a zeroth- order resonating antenna based on CRLH (composite right/left-handed) transmission lines. The CRLH consists of series connected CPW interdigital capacitors and parallel connected CPW transmission lines. The studied devices were fabricated on silicon substrate for a subsequent integration in a more complex circuit. A very good agreement between the simulation data and the experimental results has been found out in the 10 - 14 GHz frequency domain.

Coplanar waveguide stub/filters on thin membranes and standard substrates

Several coplanar waveguide series stubs and filter structures based on such stubs were designed and manufactured on standard semiinsulating GaAs substrates and thin GaAs membranes as well as on silicon based thin dielectric membranes. Coplanar waveguide circuits realized on thin membranes offer significant advantages over conventional coplanar or microstrip lines for monolithic or hybrid MIC applications.

Broadband and small-size 3-DB ring coupler

A topology for a 3-dB broadband and small-size ring coupler is proposed. It consists of fully-distributed Composite Right-/Left-Handed phase shifters and a Lange coupler. For the fabricated coupler, the frequency bandwidth is one octave, centered on 1.5GHz, while the footprint area is reduced to 25%, compared to the conventional ring coupler topology. The experimental results are in good agreement with the expected ones, obtained by electromagnetic simulation.

Silicon resonating antenna based on CPW composite right/left-handed transmission line

The aim of this paper is to present results obtained in modeling, technological realization and measurements for a CPW (CoPlanar Waveguide) zeroth-order resonating antenna, based on CRLH (composite right/left-handed) transmission line. The CRLH consists of series connected CPW interdigital capacitors and two parallel connected CPW transmission lines. The antenna was fabricated on silicon substrate for a subsequent integration in a more complex circuit. A very good agreement between the experimental and simulation results has been observed for return-loss as well as for the radiation pattern.

Design and Fabrication of MMIC Coupled Lines Coupler Consisting of Composite Right/Left-Handed Transmission Lines

Coupled-line directional coupler based on CRLH (Composite Right/Left-Handed) cascaded structures is designed, analyzed and then fabricated. The technological realization of the coupler involves one mask process on silicon substrate, using CPWs (CoPlanar Waveguides). The preliminary measurements were also performed, showing that the experimental results fit well the simulation results.

Tuning ferrite supported antenna with CRLH cells

This paper presents the results in frequncy tuning of a ferrite supported resonating CPW antenna based on CRLH (Composite Right/Left-Handed) transmission lines. The tuning is obtained by magnetically polarizing the ferrite substrate with a magnetic biasing field variable between 0 T and 0.26 T. Data obtained by simulation with a suitable microwave software indicate a frequency shift of 530 MHz at a working frequency 12.88 GHz, in very good agreement with the experimental results showing a frequency shift of 450 MHz

Design considerations and experimental results on composite right-/left-handed based distributed oscillator

An oscillator based on distributed amplifier realized by using CRLH (Composite Right-/Left-Handed) unit cells is designed and experimentally validated. The positive feedback consists of a transmission line which connects the input port and drain idle port of the amplifier. The remaining two ports of the distributed amplifier are the oscillator output ports. For this oscillator topology, the transistors give the same contribution to the output power. The measured powers at the two output ports are equal to 12.6 dBm and 10.4 dBm. The experimental frequency of oscillation is 2.77 GHz, the difference compared to the simulated value being less than 1%.

High power efficiency distributed oscillator based on composite-right-/left-handed unit cells

A circuit topology for a fixed frequency oscillator based on Composite-/Right-/Left-Handed distributed amplifier is proposed. For this topology, it is demonstrated that each transistor contributes equally to the output power. The oscillation condition is introduced, too. The oscillator has been designed and fabricated for a frequency of oscillation equal to 2.8GHz. The experimental and simulated results are in good agreement.

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.