NRD guide pulse radar for level sensor applications at 60 GHz

Abstract

An NRD guide pulse radar front-end was fabricated for level sensor applications at 60 GHz. Main emphasis was placed on circuit configuration. Typically, an oscillation power is divided by a junction circuit and is introduced into two parts. One is for transmitting wave, and the other is for LO wave to perform hetero-dyne detection. The frequency of the former is up-converted so as to be different from the frequency of the LO wave, and thus, a power amplifier is installed in the transmitting side due to low output power of the up-converted millimeter-wave. In this paper, we proposed a new circuit configuration, which consists of a Gunn oscillator with two output ports to eliminate a junction circuit, a direct pulse-modulator to obtain a high level transmitting power without an expensive millimeter-wave power amplifier, and a filter-based down-converter with an up-converter as a local oscillator. Range finding was performed by using the NRD guide pulse radar, however multi-reflection occurred between a target and a planar antenna due to a pencil beam radiation of our developing planar antenna, so that precise distance estimation could not be performed for short range detection. With this in mind, an FPGA-based signal processor was developed in order to eliminate such multi-reflection. The sequential sampling method was employed to reduce experimental errors which were investigated in terms of difference of periods between a modulated pulse train and a sequential sampling clock. The error of range finding was successfully reduced to be less than 2 % for the distance range from 2 m to 10 m under multi-reflection environment. © 2008 The Institute of Electrical Engineers of Japan.