<title>Development, analysis and performance tests of a chirped laser radar with optoelectronic signal demodulation</title>

Abstract

Scanning objects in an extended scene or large architectural structures, such as buildings, is an essential task used in numerous applications. In this paper we present the concept of a chirped laser radar with a range of 100 m and a design resolution of 3(DOT)10<SUP>-5</SUP> that exhibits an optoelectronic signal processing. The scanning signal is a 1 microsecond(s) long chirped pulse with 100 MHz bandwidth and is centered at 300 MHz. This signal is generated by a voltage controlled oscillator (VCO) that is driven by a direct digital synthesizer (DDS). The requirements imposed on the quality of the chirped signal are very high. These include temperature stabilization of the VCO and a programmed correct of its non-linear frequency response. The DDS facilitates the generation of a clean signal of the desired quality. The return signal is analyzed via an optoelectronic signal processor that measures the time delay between the target signal and the reference signal. The optoelectronic signal processor consists of two Bragg-cells and has two different output channels. Both channels evaluate the time delay of the two signals from the compressed pulses. In this paper we present the evaluation of the first channel, that measures this delay as a function of time. First experimental results indicate that the signal analysis of this channel gives a resolution of 5(DOT)10<SUP>-4</SUP>. The evaluation of the second channel is not entirely completed yet. We present experimental results achieved with the radar using a single laser diode, which is intensity modulated by variation of the diode current, and scanning of co-operative targets.