Emanuele Cardillo

A study on dynamic threshold for the crosstalk reduction in frequency-modulated radars

This paper presents the preliminary results of a new study aimed at minimizing the crosstalk effect in the receiver of a frequency-modulated radar. The main idea consists of performing a calibration of the system in absence of targets by analyzing the intermediate-frequency signal at the output of the radar receiver to compute a variable threshold according to the crosstalk amplitude. An electromagnetic analysis of the antenna matching networks has been performed since the system operates in a wider frequency range than the network performance specifications. Experimental results are presented to confirm the feasibility of the proposed approach due to the good agreement with the expected behavior.

A feasibility study of a compact radar system for autonomous walking of blind people

In this contribution, recent developments in the design and development of a novel compact smart radar for visually impaired and blind users are described. Starting from previous studies and according to the specific user requirements, a new antenna (dimensions: 54mm × 8.4mm × 1.44mm) and an integrated Tx/Rx circuit board, working in the 24-26 GHz frequency band, have been designed; the aim of these improvements is twofold: the miniaturization of the whole system allowing its integration onto a traditional white cane and a drastic reduction of the dimensions, weight and final costs of the system by using existing and available technologies.

Optical control of gain amplifiers at microwave frequencies

In the present work, the effects of 650 nm light exposure on the electromagnetic (EM) design of two gain hybrid amplifiers has been investigated. Both amplifiers have been optimized to operate in the 7.5–8.5 GHz frequency band according to the dark parameters of two pseudomorphic high electron mobility transistors having scaled gate widths. In addition, the EM analysis of the effects of the coaxial-to-microstrip connectors, has been addressed for a better evaluation of their impact on the electrical behavior of the amplifiers. Therefore, the comparison among the performance variations due to device illumination has been performed thus showing that the circuit behavior can be adjusted by using an optical signal.

Flexible CAD methodology for UWB filter with a tailored notch

In this paper, an original and flexible CAD methodology for different substrates, is presented for the design of an UWB filter equipped, if needed, with a notch at a desired frequency. The structure is designed in planar microstrip technology and it is capable of covering up to 120% of fractional bandwidth. This design methodology shows good performance with different materials either conventional or unconventional, as high-temperature superconductors for reducing losses at a minimum level. Furthermore the component has been designed with the aim of easily tailoring the notch frequency as a function of a single geometrical parameter. The procedures steps and relevant design results are shown together with the preliminary experimental characterization of a structure realized with a Rogers TMM10i substrate.

A Low-Cost Smart Microwave Radar for Short Range Measurements

In this paper, the design and development of a smart microwave radar is described. The system has been designed with the aim of realizing a cost-effective flexible radar, capable of detecting short-range targets (within 5 m) and suitable for the integration in different scenarios. The miniaturization of the radar has been possible by working within the available ISM band extending from 24 to 25 GHz. A pulsed chirp has been used to achieve a high resolution (up to 15 cm with a 1 GHz chirp bandwidth). In addition, the transmitted signal has been pulsed thus achieving a lower power consumption. A system prototype has been realized and several tests have been carried out for confirming the expected performance.

Light activation of noise at microwave frequencies: a study on scaled gallium arsenide HEMT's

This study is focused on the experimental investigation of noise at microwave frequencies for scaled gallium arsenide high-electron-mobility transistors (HEMTs). The light activation of noise has been achieved by laser exposure in the visible range. The devices have 0.25 μm gate length and 100–200–300 μm gate widths. Their DC characteristics, linear scattering and noise parameters were measured both in dark condition and under continuous wave light exposure in the 2–18 GHz frequency range. Previous results had shown a remarkable influence on all the above-measured parameters under illumination, with a special concern for the noise performance. Therefore, the authors investigated the origin of this light-activated noise in terms of the intrinsic noise sources, by extracting a noise temperature circuit model for each HEMT.In addition, the noise model formulation based on the P, R and C as well as the K g, K r and K c coefficients is used to enlighten the key aspects of the optically activated noise on the device performance. It is observed that the degradation of the minimum noise figure can be attributed to the noise coefficient R, related to the gate noise source that is strongly affected by the charge generation related to light exposure.

A straight-line equation for the notch tailoring of a microwave extra wideband filter

Abstract This paper deals with a flexible CAD methodology for the design of a microwave extra wideband filter introducing a notch at a desired frequency. The structure, designed in a cost-effective planar microstrip technology to operate in the 5–20 GHz frequency band, is capable of covering up to 120% of fractional bandwidth. It shows good performance in terms of in-band and out-of-band insertion loss and group delay. Furthermore, a simple relationship between the notch frequency and a single geometrical parameter of the structure has been extracted, thus making the component highly flexible to design. The procedure steps and the relevant design results are reported, including the electromagnetic analysis of the port connectors. Finally, different samples of the filter have been realized and measured to test the procedure. The experimental results have shown a good agreement with the expected performance thus confirming the effectiveness of the proposed methodology.

Inverse modeling of an AlGaAs/GaAs HEMT from DC and microwave measurements

This paper deals with the inverse modeling of an on wafer AlGaAs/GaAs HEMT based on DC and microwave measurements. The device employed was first characterized in DC conditions, then the scattering parameters from 0.5 to 50 GHz were measured at maximum transconductance performance. The device was also accurately modeled by means of a linear circuit model. Since no detailed information on the structure was available, we decided to undertake a physical analysis of a test structure performed by the SILVACO Atlas™ software to engage an inverse modeling study. By employing the above listed measurements data and the related circuit model, together with some general process information, we could gain a precious insight on the main features of the device structure as demonstrated by the simulation results.

Performance analysis of a microwave low-noise amplifier under laser illumination

This paper analyzes in detail the performance changes of a GaAs HEMT-based low-noise amplifier under visible (650 nm) laser exposure. The device employed was first characterized in dark and illuminated conditions over the 2-18 GHz frequency range in terms of DC, scattering and noise parameters. Subsequently, it was modeled by means of a linear circuit model with associated noise sources in both conditions. By employing the experimental results, a low noise amplifier has then been designed and optimized for dark mode operation in the 7.5-8.5 GHz frequency range. Finally, the performance of the LNA under light exposure has been evaluated. On the basis of the device performance variations under VIS light exposure, we expected either a severe degradation of the noise figure, a slight increase of the amplifier gain and a moderate variation of the input/output matching. Instead, the obtained results exhibited a moderate degradation of the overall LNA performance due to device illumination, except for the input matching level which showed to be improved. We then analyzed the correlation between the device model variations and the amplifier behavior to get a deeper insight into the observed trends.

A new methodology to estimate E-band pHemt linearity optimum load from low microwave frequency load pull measurements

A procedure to estimate the optimum linearity load for a pHemt device working in E-band based on low microwave frequency load-pull measurements is proposed. This methodology has been used to extrapolate the optimum load for two tones linearity performances (OIP3) in 70/80GHz bands of a 4×50um pHemt device using the measured optimum load at 20, 26, 37 and 40GHz. The same procedure has been successfully validated extrapolating the optimum load for P1dB at 90GHz and comparing it with that estimated using the non linear model provided by the foundry. This has proven to well predict the P1dB at E-band in previous designs. Then, the technique has been used to extract the OIP3 optimum load over entire E-band and used for a Power Amplifier (PA) design.