C. Pérez-Vega

A Simple Approach to a Statistical Path Loss Model for Indoor Communications

Path-loss in indoor environments is investigated at 1.8 GHz, using a power-law model where the exponent of the distance is the descriptive random variable. The model is extremely simple and easily applicable in practice by working engieers who need only make a few measurements to get a knowledge of path loss sufficient for many applications. The model fits well experimental data in various environments under different propagation conditions, including cross polarization, and the observed behavior of the exponent suggests the possibility of using only one distribution function to statistically characterize path loss.

X-band Gunn diode oscillator for a multiple-frequency continuous-wave radar for educational purposes

A low-cost, high-performance X-band Gunn diode oscillator for educational and research purposes has been developed. The cavities have been manufactured on a standard WR90 rectangular waveguide with UBR100 flange in order to make it compatible with the waveguide circuitry usually available in a basic microwave laboratory. The capability of sweeping the whole X band at constant output power and low phase noise, as well as the low cost of its components, make this device suitable for users at any level. As an example of its many educational applications, a multiple frequency continuous-wave (MFCW) radar has been developed, and the results of the laboratory implementation are shown.

A simple and efficient model for indoor path-loss prediction

A power-law path-loss model for indoor communications at 1.8 GHz is examined. In it, the exponent of the distance is treated as a random variable and its behaviour studied through experiments conducted under various propagation conditions in different buildings. The effects of random human traffic in the propagation channel, as well as those of antenna polarization are also experimentally studied. The statistical behaviour of the exponent and its fitting to several distribution functions, in particular Weibull, Nakagami and gamma ones, are also reported. By using the proposed model, new, simple and efficient instruments can be developed as an aid for the estimation of the power budget of indoor wireless communication systems.

Optical ports: next generation of MMIC control devices?

The results of our research on the electro-optical control of MMICs are shown in this paper. Two different devices have been investigated: a GaAs chip monolithic amplifier at S band, and an AlGaAs chip MMIC voltage controlled oscillator at Ku. The possibilities of optical control of the amplifier are evidenced as follows: if the amplifier operates with the same biasing, the gain can be optically controlled from a condition of almost isolation,, up to an active condition, which gives a range of optical control of about 15 dB and provides an improvement of the input and output matching in a range of 12dB and 6dB, respectively. The possibilities of optical control of the VCO by illumination of the PHEMT transistor are demonstrated through measurements of the oscillation output power and frequency. An optical control range of 8dB of oscillation output power and up to 400MHz of oscillation frequency has been obtained. This optical control suggests an interesting control of gain and matching for other microwave FET based active devices.

Large-signal model for microwave FETs under CW laser stimulation: Research Articles

In this article, a linearity-improving technique for active antennas and arrays, based on spatial power combining, is presented. An auxiliary branch is employed to cancel the radiation pattern at the intermodulation distortion (IMD) components, either in the main-beam direction for a subarray or in all elevation angles for a single antenna element. The need for precise amplitude and phase control over the IMD currents in the array auxiliary elements is demonstrated, quantifying the possible degradation suffered in the carrier-to-intermodulation distortion (CIMD) ratio improvement obtained when this solution is applied. The potentialities of implementing the derivative-superposition technique in small- and large-signal regimes, both in an array and in an antenna element, are finally proposed.