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The design and development of a co-pulse IFM receiver

Myburgh, Kobus (2015-12)

Thesis (MEng)--Stellenbosch University, 2015.


ENGLISH ABSTRACT: The instantaneous frequency measurement (IFM) receiver is normally a subunit used in electronic warfare receivers. Its purpose is to measure the frequency of pulse and continuous wave signals over a very wide bandwidth and power dynamic range. It should be noted that the band of interest can range from 500 MHz to 40 GHz. This is an extremely wide bandwidth. These receivers have a very high resolution (typically 1 MHz) over this very wide bandwidth and the error of these receivers is typically a few megahertz. The IFM receiver should reveal the presence of signals. It is not generally known in advance whether signals are present, even if they are, nor their frequency and other characteristics. An inherent disadvantage of all traditional IFM receivers is that overlapping pulses within the same power range corrupt the discriminator outputs to the extent that frequency measurements appear random. This is particularly bothersome, as high duty cycle and continuous wave emitters reduce the frequency measurements to little value. This thesis entails the design and development of an IFM receiver (co-pulse IFM receiver) that can distinguish overlapping pulses within the same power range. Different acquisition receivers were researched to make sure that the IFM receiver is still the best option, taking bandwidth, frequency resolution/accuracy and throughput time (latency) into consideration. The traditional IFM receiver was researched and simulated in MATLAB. While researching the traditional IFM receiver, literature was discovered that identified Prony’s method as a solution to distinguish overlapping pulses (simultaneous signals). Literature proposing Prony’s method that had been submitted from as early as 1989 was found. However, no evidence of the use of the method in current commercial IFM receivers was found, indicating that the implementation of Prony’s method is the difficult part. Prony’s method was simulated in MATLAB, then implemented, simulated and tested in hardware. The results of the hardware implementation were documented and demonstrated a solution to distinguish overlapping pulses.

AFRIKAANSE OPSOMMING: Die oombliksfrekwensiemeting (OFM)-ontvanger is gewoonlik ᾽n sub-eenheid wat gebruik word in elektroniese oorlog-ontvangers. Die doel daarvan is om die frekwensie van gepulsde en kontinue seine te meet oor ᾽n baie wye bandwydte en wye drywing dinamiese bereik. Daar moet in ag geneem word dat die bandwydte van belang vanaf 500 MHz tot 40 GHz kan strek. Dit is ᾽n uiters wye bandwydte. Hierdie ontvangers het ᾽n baie hoë resolusie (tipies 1 MHz) oor die baie wye bandwydte en die meetfout van hierdie ontvangers is tipies ᾽n paar megahertz. Die OFM-ontvanger moet die teenwoordigheid van seine uitwys. Dit is gewoonlik nie eers seker of daar wel siene is nie, nog minder wat die moontlike frekwensie en ander eienskappe is. ᾽n Nadeel van alle tradisionele OFM-ontvangers is dat oorvleuelende pulse wat naby dieselfde drywings bereik is, die diskrimineerders se uitsette verkeerd beïnvloed, sodat die frekwensiemetings verkeerd is. Dit is ᾽n groot probleem want hoë diensiklus- en kontinue sein-uitsenders verlaag die frekwensiemeting se betroubaarheid. Die doel van hierdie tesis is om ᾽n OFM-ontvanger (tweepuls-OFM-ontvanger) te ontwikkel wat oorvleuelende pulse wat naby dieselfde drywingsbereik is, te kan onderskei. Verskillende sein-optelontvangers is nagevors om seker te maak dat die OFM-ontvanger nog steeds die beste opsie is as bandwydte, frekwensieresolusie, akkuraatheid en vertragingstyd (latensie) in ag geneem word. Die tradisionele OFM-ontvanger is nagevors en is in MATLAB gesimuleer. Terwyl die tradisionele OFM-ontvanger nagevors is, is literatuur gevind wat Prony se metode voorstel as oplossing vir die probleem van oorvleuelende pulse (gelyktydige seine). Literatuur wat so vroeg as 1989 gepubliseer is, is gevind wat Prony se metode voorstel. Bewys van die gebruik daarvan in huidige kommersiële OFM-ontvangers is egter nie gekry nie, wat aandui dat die implementering daarvan baie moeilik is. Prony se metode is gesimuleer in MATLAB. Daarna is dit geïmplementeer, gesimuleer en in hardeware getoets. Die resultate van die hardeware-implementering is gedokumenteer en dit demonstreer ᾽n oplossing om oorvleuelende pulse te onderskei.

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