The applications of superconductors in cellular network base stations

Du Toit, Riaan (2008-03)

Thesis (MScIng)--University of Stellenbosch, 2008.

Thesis

ENGLISH ABSTRACT: The Applications of Superconductors in Cellular Network Base Stations R. Du Toit Department of Electronic Engineering University of Stellenbosch Private Bag X1, 7602 Matieland, South Africa Thesis: MScEng (E&E) March 2008 Wireless communications have increasingly become part of our world. The growth of radio frequency (RF) wireless communications has led to an increasing demand for frequency spectrum licenses, increased system capacity and larger user bandwidths. These demands lead to frequent improvements on the physical and higher layers of wireless communication protocols. Changes in the physical layer are frequently followed by the need for replacement of dedicated hardware components. The need therefore exists for a more general and programmable physical layer. A more general and programmable radio architecture implies increased radio front-end performance without losing programmability. The contribution of this thesis is the analysis of how superconductor electronics (SCE) using Rapid Single Flux Quantum (RSFQ) logic may advance wireless radio front-ends by providing a general-purpose programmable radio architecture. Superconductor analogue to digital converters (ADCs) are employed as high performance, programmable digitization structures. Once a received signal is digitized, SCE can be used to rapidly do recursive operations such as synchronization and multi-path delay estimation. These operations are based on correlation, and for evaluation of such operations with SCE the popular CDMA multiplexing method is studied along with the WCDMA protocol used in the 3G UMTS standard. Two delta-type oversampling superconductor ADC modulator designs are presented and evaluated along with a hybrid decimation filter design, using both the benefits of SCE and room temperature electronics. A fast RSFQ correlator design is also presented and evaluated for use in a multi-path estimation structure. A rapid multi-path delay estimation architecture based on fast RSFQ circular data buffers and correlators is presented. The architecture uses the fast speeds of RSFQ logic to obtain accurate path delay estimates in a rapidly changing wireless environment. It is concluded that RSFQ-based wireless receiver components offer promising new options for data conversion, correlation and multi-path delay estimation implementations.

AFRIKAANSE OPSOMMING: The Applications of Superconductors in Cellular Network Base Stations R. Du Toit Department of Electronic Engineering University of Stellenbosch Private Bag X1, 7602 Matieland, South Africa Thesis: MScEng (E&E) March 2008 Draadlose kommunikasie word al hoe meer deel van ons wêreld. Groei in radiofrekwensietipe kommunikasie het gelei tot ’n toenemende aanvraag na frekwensiespektrum lisensies, vergrote stelselkapasiteit en groter gebruikerbandwydtes. Hierdie aanvrae lei tot gereelde en spoedige verbeteringe op die fisiese en hoër lae van huidige draadlose kommunikasieprotokol. Veranderinge in die fisiese laag vereis gewoonlik dat toegewyde hardewarde komponente vervang word. Die behoefte bestaan dus vir ’n meer algemene, programmeerbare fisiese laag. Dit vereis dus ’n verbetering in die radio-ontvanger se komponente naaste aan die antenna sonder om programmeerbaarheid te verloor. Die bydrae van hierdie tesis is hoofsaaklik die analise van hoe supergeleierelektronika wat van Rapid Single Flux Quantum (RSFQ) logika gebruik maak, huidige draadlose sellulêre basisstasies se fisiese laag kan verbeter deur ’n meer algemene en programmeerbare radio-argitektuur op te lewer. Supergeleier analoog-na-syfer omsetters (ADCs) word bestudeer as moontlike programmeerbare versyferingstrukture wat steeds hoë werkverrigting lewer. Wanneer ’n ontvangde sein in digitale vorm omgesit is, kan supergeleierelektronika gebruik word om vinnig rekursiewe operasies uit te voer. Voorbeelde van sulke operasies is sinkronisasie en die waardebepaling van die vertraging van verskillende paaie wat ’n sein volg na die ontvanger. Hierdie spesifieke operasies se werking is gebaseer op korrelasie, en vir die evaluasie van sulke operasies met supergeleierelektronika is die gewilde wyeband-CDMA (WCDMA) protokol wat gebruik word in die 3G UMTS-standaard. Twee supergeleier-delta-tipe oorversyferings-ADC-moduleerderontwerpe word voorgelê en evaluasie word daarop gedoen saam met ’n hibriede desimasiefilterontwerp wat gebruik maak van beide die voordele van supergeleierelektronika en kamertemperatuurelektronika. ’n Vinnige RSFQ-korreleerder word ook voorgelê en evaluasie word daarop gedoen vir gebruik binne ’n multi-padvertraging-waardebepalerstruktuur. Hierdie struktuur wat gebaseer is op RSFQ sirkulêre buffers en korreleerders, word voorgelê. Die waardebepaler maak gebruik van die spoed van RSFQ-logika om akkurate multi-padvertragingswaardes te bepaal in ’n vinnig veranderende draadlose omgewing. Die gevolgtrekking word gemaak dat RSFQ-gebaseerde draadlose ontvangerkomponente groot voordele in versyfering-, korreleerder- en multi-padvertragingsbepaler-toepassings bied.

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