Radar spurious emission: measurement and impact on radio communication system performance

Abstract

In this thesis is presented a useful and economic measuring principle with which radar spurious emissions can be investigated under field conditions without disturbing the function of the radar in any way. The method presented here consists of two parts: In the time-domain parameter study is presented, how the radar antenna rotation produces radar pulses to the measuring receiver. Also is presented, how receiver parameters are defined by availability and use of radar pulses in the measurement. In the frequency spectrum measurement part a new sweep measurement system is presented. In this measurement the YIG filter presented by ITU [1] is replaced by a similar multistage tunable band-stop filter, which meets similar filtering characteristics, this is more easy to use and a less expensive filter. It is explained how the needed measurement dynamics are achieved and how the measurement time is determined and optimized in different situations. A two part measuring approach like this has not been reported before. ITU recommendations for attenuation of radar spurious emissions are updated to 100 dB below the radar nominal frequency (NF) signal level. The fulfillment of these spurious level requirements sets a hard challenge for measuring dynamics: dynamics must be more than 110 dB. The author provides in this work a solution to this requirement. This measuring method produces results, with which one can conclude the relative power level of radar spurious emissions and its effect on other radio services. In this work the spectrum produced by a 5 GHz weather radar has been studied and the results have been applied to study radar impact to terrestrial digital radio relay systems (TDRRS). The achieved result is both very important and current, and it can be utilized in the planning of new radar systems as also in the planning of new radio networks operating in the frequency ranges adjacent to radar frequencies. Possible radio networks in addition to TDRRSs that can be interfered from radar spurious emissions are Wireless Local Area Networks (WLAN), Worldwide Interoperability for Microwave Area (WiMAX) and Ultra Wide Band (UWB) systems. These systems also can interfere with radar frequencies.