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Generation of unipolar and bipolar pulses by using high- and medium-voltage silicon rectifier diodes is achieved. These components are provided by the French Atomic Energy Commission (CEA). Furthermore, these devices work in the linear mode of photoconducting switches. Generation of electrical unipolar pulses with an amplitude of 10.7 kV and a full-width at half-maximum of 300 ps by using only 1.2 mJ of optical power is demonstrated. This energy value is 10-100 times less than usually published during the past decades. Furthermore, the linear mode running of these devices permits to synchronize several generators with a precision as low as 2 ps. This low timing jitter is useful for bipolar generators in order to control their spectrum with high precision, i.e., bipolar pulses of 3 kV peak-to-peak have been generated with a cycle duration of 400 ps and an optical energy of 1 mJ. Index Terms--Antenna array feeds, laser applications, microwave generation, photoconducting materials, synchronous generators synthetic aperture radar.

In this article, a damped sinusoids high-voltage source based on the optoelectronic waveform generators principle is presented to perform electromagnetic susceptibility testing. Photoconductive semiconductor switches (PCSS), operating in linear switching mode and triggered via a laser pulse, have been used. The developed conducted source generates damped sinusoids with a center frequency between 30 and 600 MHz, a maximum peak-to-peak amplitude of approximately 3 kV for a bias voltage of 4 kV, a Q factor between 8 and 11, and a transient shape closest to a reference damped sinusoid. The dimensions of the source go from 220 mm × 80 mm to 220 mm × 510 mm. A PCSS characterization has been set up to determine the necessary parameters for the establishment of a damped sinusoids optoelectronic generator model on Keysight Advanced Design System software. Experimental tests have been realized using a measurement bench to compare the obtained and simulated signals. [ABSTRACT FROM AUTHOR]

In this paper, a new design of an optoelectronic system for transient waveforms shaping, with a selection of rejected frequencies, is presented. The generation of short pulses is performed with several optoelectronic generators using photoconductive semiconductor switches (PCSS) operating in linear switching mode and triggered via a laser pulse. With the appropriate number of generators, the system generates a spectrum ranging from 300 MHz to 3 GHz, with rejected frequencies at 900 MHz and 1.8 GHz. A PCSS characterization has been set up to determine the necessary parameters for the establishment of an optoelectronic generator model on Keysight Advanced Design System software (ADS). Experimental tests have been realized using measurement benches to compare the simulated and measured signals. [ABSTRACT FROM AUTHOR]

This study presents a new design of a reduced volumetric ultra-wideband (UWB) antenna using innovative dielectric based on the use of geopolymer material which is safe and eco-friendly. The created antenna is intended to radiate in the air. The impedance mismatch due to interface dielectric/air at the aperture of the antenna imposes to choose dielectric material with an appropriate permittivity value. In this study, the authors focus on the experimental protocol that they use to elaborate a dielectric material with suitable dielectric properties over an UWB domain. An experimental phase of dielectric properties assessment is also described. The conceived antenna is inspired by K-antenna which constitutes the starting point of the proposed new antenna design, particularly because of their small dimensions. The antenna is intended to operate in a frequency band ranging from 300 MHz to 3 GHz. The authors demonstrate that the use of an appropriate innovative dielectric material like a geopolymer is an efficient way to reduce the antenna size. Furthermore, the behaviour of the antenna filled with geopolymer is validated using experimental results. [ABSTRACT FROM AUTHOR]

The development and construction of self-scanning capability short-range ultrawideband (UWB) radar is forthcoming for the French Military for Defense. This paper is devoted to the presentation of the self-scanning radar principle and of the development, construction, and tests of the different blocks needed to implement the elementary part of the forthcoming radar. The elementary radiation source is composed of a microstrip line with photoconductive switches, an optical system to trigger the switches, a pulsed modulator used as bias voltage to load the line, and a UWB antenna to radiate high electric fields in a broad frequency band. The main proposed innovations are devoted to the integration of the photoconductive switches within the antenna and to the use of the pulsed modulator as bias source instead of a dc voltage source. This modulator allows considering the increase in the yield of the whole source as well as the increase in the radiation bandwidth. Experimental results are presented in order to compare the switching efficiency with a dc bias source against this pulsed modulator bias source. Finally, photoswitches triggered by an 80-ps/20- \mu \textJ laser source are able to generate monopolar or bipolar pulses in the kilovolt range with subnanosecond duration and a 33-MHz pulse repetition frequency. First radiated electric field results of the whole device are also reported. [ABSTRACT FROM AUTHOR]

The ultrafast speed and the large spatial area scanning autonomy are the two main advantages of the new radar presented in this paper. Indeed, the autonomous beam scanning capability with high pulse repetition frequency (PRF) is obtained by coherent combining of electrical fields emitted from active antennas’ array integrating photoconductive switching devices. An original signal processing associated with this new radar system is presented. We show a hybrid version of a CLEAN algorithm able to overcome the depth limitation induced by high PRF with standard imaging signal processing. Simulations and measurements are performed to validate the proper operation of the algorithm. [ABSTRACT FROM PUBLISHER]

Describes an optoelectronic sampler and autocorrelator. Device operation; Electromagnetic components; Numerical method for electromagnetic analysis; Behavior of the propagation line; Time conductivity selected for the simulation of the autocorrelation function.