Attila Zólomy

Optical millimeter wave generation for cellular mobile systems

An optical millimeter wave generation approach is presented for cellular mobile systems. The well-known methods distribute the millimeter wave signal via fibers. They have drawbacks because they need very high speed photonic components which are expensive. That problem is overcome by the present approach utilizing an optically transmitted low-frequency reference signal to generate the millimeter wave carrier. This approach applies inexpensive photonic components and is less sensitive to the fiber dispersion.

Effect of parasitics in tunable X-band metamaterial isolators

In this paper the investigations of the parasitics in a fabricated X-band tuneable metamaterial isolator are presented. The isolator applies a microstrip left handed artificial transmission line (LHTL) with Butterworth phase response on an anisotropic ferrite substrate material. The structure is simplified and optimized to reduce the harmful right handed and coupled parasitic effects to achieve stable, spurious resonance free phase characteristic in the targeted 8-12 GHz frequency band. This is required to archive the tuneable 20 dB isolation by varying the applied magnetic field. Detailed analysis shows that both the capacitive and inductive coupling between the consecutive stage printed inductors have no significant effect in realistic structures. Also, the parallel shunt parasitic capacitance can be reduced enough with proper design to have very little effect. The main limiting factor is the series parasitic inductance of both the traces and the applied series capacitors.

Multi-band impulse filtered UWB signal transmission by wideband optical VCSEL transmitter

This paper introduces a novel approach for transmitting UWB signals over optical fibre with cost effective Vertical-cavity surface-emitting laser (VCSEL). The transmitted impulse compile with the strict European frequency plan (ECC). A prototype filter is presented with lumped elements which has a −40 dB/500 MHz cut off at the critical 3.1 GHz band. Also a novel impedance matching method is presented for matching low cost 850 nm multi-mode VCSEL in the lower UWB band. Time-domain transmission measurements are presented with the fabricated devices that show this approach is acceptable for low cost remote antenna connection for UWB applications.

Strongly nonlinear feedback technique for significant phase noise suppression at microwave harmonic oscillators

Calculations are presented to study the phase noise suppression effects of an additionally introduced highly nonlinear feedback loop in microwave harmonic oscillators. Calculations are done for determining the optimal structure and parameter set of nonlinearly feedbacked harmonic oscillators, with respect to the effects of the nonlinear properties on the behaviour of the phase noise characteristics. Using the calculated analytical form /spl sim/6 dB of phase noise suppression was achieved. Measurement and simulation results far confirming our theoretical principles are also reported.

Wideband impedance matching for VCSELs used in Free-Space quantum communication

The quantum based communication techniques are one of the leading research topics of optical communication. Quantum based Free-Space Optical (FSO) communication systems are potential alternatives to high speed microwave communication. The high speed operation requires wide operation bandwidth for the elements applied in the FSO link including the transmitter lasers, VCSELs in many cases. This paper discusses wideband impedance matching techniques for VCSELs, to have efficient and equalized electro-optical transfer characteristic in the whole operation band. In this paper a complete VCSEL (op. wavelength: 850 nm) matching process is presented, which results better than -10 dB simulated input reflection in 60% relative bandwidth around the 1.375 GHz center frequency.

Design of a distributed amplifierfor the first higher order passband operation

It is shown that distributed amplifiers using transmission lines between the active devices are able to operate at higher order passbands. This feature is similar to the operation of a distributed element microwave filters, where besides the fundamental, higher order passbands appear at the odd harmonics. This property allows higher frequency operation which cannot be achieved by conventional distributed amplifier design techniques. Analysis of operation and a novel design technique is presented in detail, which yields the optimum design parameters for higher order passband operation of distributed amplifiers. The method is demonstrated by the realization of a hybrid integrated three stage amplifier.

Application of high impedance antennas in low cost ISM wireless chips

In case of integrated digital radio chips devoted to low cost, licence free short range radio systems the necessary bill of material and the battery life are one of the most important issues. The targeted RF power level determines whether a low or a high Q output architecture (output driver stage+optional matching+antenna) gives better result. It is shown that in case of the most commonly used radiated power ranges (-20...+10 dBm) for this radios, the high impedance configuration is advantageous. The high Q configuration is applied in a general purpose 0.6 mum BiCMOS transmitter chip operating in the 315, 434, 868 and 915 MHz bands. Novell printed high Q antenna topologies ad matching network are presented as well.