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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 paper, an optoelectronic sampler and an autocorrelator are described. The devices are made with microstrip propagation lines, and ultra-rapid photoconductive switches are integrated in the same substrate. These devices are studied along two interacting directions: sampler description and operation, and electromagnetic study. In particular, the electromagnetic study is discussed here. The purpose of the first is to understand the electromagnetic behavior of the optoelectronic sampler. The second study enables us to simulate the autocorrelator operation in order to characterize the ultra rapid photoconductive switch.

In this paper, a static electromagnetic study of planar structures is effected. The determination of electric and magnetic field distributions is used to deduce the characteristic impedance of these structures. The second application concerns the simulation of the line feed when a transient analysis using the Finite Difference Time Domain Method is used to analyse the line behaviour. In the case of a microstrip line, this new excitation method is compared to two excitations which are generally used.

The modeling of a 90 degree bend in a microstrip, carried out via a time frequency approach based on the Finite Difference Time Domain technique, is presented. Inthe study, the scattering parameters and radiated energy are derived from the Fourier transformed currents of the microstrip. A discussion of the stratified medium concept which was used to compute the radiation and surface wave losses is also included.