Passive intermodulation tester characteristics

Abstract. Passive intermodulation (PIM) is a severe issue for base transceiver stations. It can cause issues to the receiver of the device or to nearby devices if power levels are high enough. In the past, there have been many studies on the PIM, mostly concerning on modelling and mitigation of PIM. In this thesis, 3rd and 5th order forward PIM levels are measured and analysed from base station filters to determine if they are good enough for receiving of low-level signals. Also, used PIM test setup is simulated with modified component parameters for finding output third order intercept point (OIP3) threshold values of each component for which the setup still provides accurate enough results. Also, noise level calculations and cost estimation of typical PIM test setup is presented. PIM products were measured with accurate test setups that had residual PIM levels clearly below measured levels. As PIM performance often varies with time all measurements were repeated several times. The best unit out of all 10 measured devices under test (DUTs) had 100 % pass rate and less than 2.5 dB standard deviation. Results were also more than 8.5 dB over the limit in average. All the results were calculated from all measurement samples of DUTs. There were 4–16 of measurements per DUT. The worst unit had 25% pass rate and PIM results that were below limit in average. PIM results suggest that high standard deviation is linked to failed results, usually. Two additional DUTs was tested for finding if the source was electro-thermal nonlinearity. The results suggest that it might have been the source, but due to low quantity of measurements, waterproof conclusion can’t be made. There are many limiting factors in testing of PIM. First of all, the test results must be clearly above noise floor in order to see the real PIM products. Also, the test setup must have its residual intermodulation at least 10 dB below the measured PIM of DUT. Then, the measured results are considered to be accurate enough. That’s why the components of the setup have to be low-PIM. For these reasons, test setup simulations were done with AWR simulation tool in order to find the threshold values on which the setup still provides reliable test results for each test setup components. It was found out that the combiner should have the highest OIP3 value, of at least 61.3 dBm when ≈ 40 dB notch filter was used before DUT at the measured 3rd order PIM frequency. Without notch, OIP3 should be at least 73.7 dBm. Therefore, notch filter lowered the need of OIP3 by 12.4 dB. Signal generators, power amplifiers and circulators of the setup were limited by their 1 dB compression point. As a conclusion, this thesis work was successful since the limitations of the setup were found by simulations and calculations. Also, testing and analyzing of PIM products was performed successfully with low residual levels. The theory, calculations and simulations presented in this thesis can be used in acquisition of PIM test setup components. Also, the simulation model can be modified for simulating the PIM impact of any components in the test setup.Passiivisen keskinäismodulaatiotesterin piirteet. Tiivistelmä. Passiivinen keskinäismodulaatio (PIM) on vakava häiriö tukiasemille. Kun signaalien teho on tarpeeksi suuri, voi PIM aiheuttaa suuria ongelmia laitteen vastaanottamiskykyyn tai muihin lähellä oleviin laitteisiin. PIM:n mallinnusta ja heikennystä on tutkittu paljon menneisyydessä. Tässä diplomityössä 3:n ja 5:n asteen suoraan etenevän (eng. forward) PIM:n tasoja mitataan ja analysoidaan tukiasemien suodattimista, jotta voidaan päättää onko ne hyviä pienitehoisten signaalien vastaanottamiseen. Lisäksi käytettyä PIM-testijärjestelmää simuloidaan muuntamalla testijärjestelmän komponenttien parametrejä siten, että löydettäisiin jokaisen komponentin kolmannen asteen leikkauspisteen (OIP3) raja-arvot, jolla testijärjestelmä toimii taaten tarpeeksi tarkkoja tuloksia. Tavanomaisen PIM-testijärjeslmän kohinatason laskuja ja kustannusarvio on myös esitetty. PIM-tuotokset mitattiin tarkoilla testijärjestelmillä, joiden residuaaliset PIM-tasot olivat selvästi alle tutkittavasta laitteesta (DUT) mitattavia tasoja. Parhaalla yksiköllä 10:stä mitatusta oli 100 %:n läpäisytaso sekä alle 2,5 dB:n keskihajonta. Lisäksi, tulokset olivat keskimäärin 8,5 dB parempia kuin läpäisyraja. Kaikki tulokset on laskettu DUT:en kaikista mittausnäytteestä, joita oli 4–16 per DUT. Huonoimalla yksikkö oli 25 %:n läpäisytaso ja sen tulokset olivat keskimäärin alle läpäisyrajan. PIM-tulokset viittaavat siihen, että suuri keskihajonta on yleensä yhteydessä huonoihin tuloksiin. Kaksi ylimääräistä yksikköä testattiin, jotta tiedettäisiin olisiko PIM:n lähteenä sähkö-terminen epälineaarisuus. Tulokset viittaavat, että se voisi olla PIM:n lähde, mutta pienestä testimäärästä johtuen vedenpitävää johtopäätöstä ei voida tehdä. PIM:n testauksessa on monia rajoittavia tekijöitä. Ensinnäkin, testitulosten pitää olla selvästi yli kohinatason, jotta ne erottuvat nähtäviksi. Myös testijärjestelmän residuaalisen keskinäismodulaatio pitää olla vähintään 10 dB:ä matalemmalla tasolla kuin testattavan yksikön PIM. Siten mitatut tulokset mielletään tarpeeksi tarkoiksi. Sen takia testijärjestelmän osien pitää olla pienitasoisia PIM-teholtaan. Näiden syiden takia, testijärjestelmän simulointeja tehtiin AWR-simulointityökalun avulla, jotta löydettäisiin raja-arvot mittajärjestelmän eri osille, millä mittajärjestelmä tuottaa luotettavia tuloksia. Selvitettiin, että kaikista osista yhdyssuodattimella (eng. combiner) pitäisi olla suurin kolmannen asteen leikkauspiste (OIP3), vähintään 61.3 dB noin 40 dB:n kaistanestosuodattimen, joka tulee ennen DUT:a mitattavalle PIM-taajuudelle, kanssa ja vähintään 73.7 dB ilman kaistanestosuodatinta. Täten suodatin laski OIP3:n tarvetta 12.4 dB. 1 dB kompressiopisteet rajoittivat OIP3-raja-arvoja signaaligeneraattoreilla, tehovahvistimilla ja sirkulaattoreilla. Kaikkiaan työ oli onnistunut, sillä testijärjestelmän rajoitukset löydettiin simulointien ja laskutoimitusten avulla. Lisäksi mittaukset ja PIM-tulosten analysointi tehtiin onnistuneesti pienillä residuaalisilla tasoilla. Tämän diplomityön teoriaa, laskutoimituksia ja simulaatioita voidaan käyttää PIM-testijärjestelmän komponenttien hankintaan. Lisäksi, simulaatiomallia voidaan muokata siten, että minkä tahansa komponentin vaikutusta PIM-häiriöihin voidaan simuloida sen avulla

Passiivinen intermodulaatio suuritehoisissa radiolähetin-vastaanottimissa

Passive intermodulation (PIM) is a phenomenon which occurs when at least two signals are fed into a nonlinear passive device or circuit. Sources for PIM can be divided into two groups, nonlinearities in metal junctions and nonlinear materials. The most common source for PIM is a loose or a bad metal connection. The problem is more in a base station side because PIM requires high powers and a base station can have high trans-mission (TX) power and receive (RX) power may be low. In addition, there are con-nectors in use at base stations and antennas with metallic junctions. Furthermore, a base station duplexer may have a high isolation between TX and RX port leading to a situa-tion where intermodulation (IM) products due to TX power amplifier are attenuated well and PIM which is generated after the TX band-pass filter becomes significant. PIM is significant in the carrier aggregation technology, which uses more than one component carrier. In carrier aggregation, component carriers can be allocated non-contiguously on one or more frequency bands. If the duplex spacing is narrow, high-power 3rd order PIM products may fall on RX frequency band and desensitize the transceiver’s own receiver. Digital IM cancellation is based on estimating how TX signals are modified at the path to the receiver by taking and processing samples of the received signal. Then the main idea is to regenerate replicas of IM products and subtract them from the received signal. The aim in this thesis is to demonstrate that PIM products, which are generated after the TX band-pass filter, can be reduced with digital cancellation. The duplexer that is used in measurements is a frequency band 1 base station duplexer which has 190 MHz duplex spacing. Because of that, lower than 7th order IM products are not in the RX frequency band. For a reproducible test setup, a nonlinear connection at the antenna port of the duplexer is emulated with a diode. The diode circuit generated high-power IM products already with +20 dBm TX power at the antenna port and with this power the TX filter completely attenuated the IM products due to the power amplifier. With the digital cancellation, the 7th order IM product was successfully attenuated by 6 dB to 14 dB depending on the TX power. These measurement results demonstrate that it is possible to reduce PIM interference with digital cancellation. However, in this thesis the duplex spacing was considerably wide and therefore the most high-power 3rd order IM products could not be measured. For future research it would be important to measure how digital cancellation works when the duplex spacing is narrow and PIM product power is higher but the order is lower

Air-Induced Passive Intermodulation in FDD MIMO Systems : Algorithms and Measurements

In this article, we model and develop effective cancellation schemes for passive intermodulation (PIM) distortion induced by external objects in the vicinity of the transmitter—referred to as air-induced PIM—in frequency-division duplex (FDD) multiple-input–multiple-output (MIMO) systems. PIM is interference generated from the transmitted signals undergoing nonlinear transformation, which, in FDD systems, may cause desensitization of the receiver chain. First, we present a general model of the received air-induced PIM signal, with an arbitrary number of dual-carrier TX chains active and an arbitrary number of PIM sources causing interference, on all the intermodulation frequencies. Then, the derived model is used to develop a cancellation scheme based on a complete set of basis functions (BFs) in a rank-2 dual-carrier MIMO system with four active carriers. To alleviate the high complexity of the aforementioned scheme, we then propose a novel alternative cancellation scheme with much reduced complexity, leveraging on the physical modeling of the system, which is capable of handling any number of PIM sources in the system. RF measurement-based experimentations carried out with real-life equipment evidence excellent cancellation capabilities of the complete BF model, which can be retained with much reduced complexity with the proposed alternative technique.publishedVersionPeer reviewe

Advanced Techniques for the Characterization and Experimental Validation of Passive Inter-Modulation Effect (PIM) in Space Communications Systems

[ES] Los satélites de telecomunicación operan en entornos multiportadora, bajo una demanda continua de mayores capacidades de transmisión. Esto ha originado un aumento en los niveles de potencia de RF, frecuencias de trabajo, y número de canales transmitidos, estimulando la aparición de efectos no lineales de alta potencia, como Multipactor, Corona, y la Intermodulación Pasiva (PIM). Entre los efectos anteriores, el PIM es el menos comprendido, debido a su carácter no lineal y su estrecha relación con la fabricación, lo que dificulta el desarrollo de modelos fiables. Los términos de PIM generados en el enlace descendente pueden interferir a la débil señal en el canal de recepción, amenazando la capacidad de recepción del enlace ascendente. Los modelos tradicionales de PIM suelen basarse en una excitación formada por dos portadoras. Aunque se trata de un caso simple y bastante representativo, presenta diferencias importantes con el escenario real multiportadora. El trabajo de este Ph.D. intenta reducir estas diferencias. Para lograrlo, se realizan dos nuevas contribuciones de relevancia para las condiciones reales de operación de los satélites. En concreto, se ha investigado de forma teórica el rol de las fases de las portadoras en el PIM, y se ha propuesto un nuevo modelo que tiene en cuenta el efecto de las portadoras no contribuyentes en un cierto término de PIM, aplicando un nuevo principio de conservación de energía. Los resultados obtenidos con ambos modelos teóricos se ajustan a los datos experimentales. Debido a la compleja naturaleza del PIM, la validación de los componentes de RF de satélites se realiza mediante tests. Por lo tanto, la disponibilidad de bancos de medida de PIM es un tema de interés para la industria espacial. Sin embargo, el diseño de bancos de altas prestaciones es un desafío, ya que su nivel de PIM debe ser inferior al requerido para validar los dispositivos. Para hardware de satélites, la diferencia entre el nivel de las portadoras a transmitir y la señal de RF a detectar es como 185 dBc. En este Ph.D. se proponen unas nuevas arquitecturas integradas de bancos de PIM en guía de ondas, que cubren tanto el PIM conducido como el radiado. Dichas arquitecturas permiten una reducción importante del nivel de PIM residual del sistema de medida, siendo flexibles, capaces de manejar elevados niveles de potencia, y libres de resonancias e interacciones indeseadas. Los elementos claves de estos bancos son unos multiplexores de bajo PIM, que pueden incorporar dos familias de filtros que admiten un elevado número de ceros de transmisión, y por tanto, son capaces de proporcionar un elevado rechazo en la banda de recepción del PIM. Los bancos de medida de PIM conducido por onda reflejada, sin embargo, están expuestos al PIM generado por la carga empleada para absorber las portadoras de alta potencia. Para resolver esta situación, se han propuesto unas nuevas cargas de bajo PIM, que reducen el PIM residual de estos sistemas de medida. Así mismo, se ha elaborado un nuevo tipo de transición para mitigar el PIM respecto a flanges estándar. Para escenarios radiados se ha desarrollado una formulación capaz de relacionar densidades de potencia en el dispositivo bajo test con los niveles detectados en el banco de medida, y que por tanto permiten trasladar especificaciones de PIM del satélite al sistema de medida. Por último, se han mostrado varias campañas de medida de PIM realizadas con bancos implementados acorde a las nuevas arquitecturas propuestas. Las medidas cubren varias bandas de frecuencia y diferentes escenarios (tanto PIM conducido como radiado). Se ha determinado el excepcional nivel de fondo de ruido de PIM logrado en cada banco. Además, se han mostrado resultados obtenidos para medidas de PIM radiado en capas aislantes multicapa y mallas reflectoras, obteniendo interesantes conclusiones en cuanto a geometrías y impacto que tienen en el PIM elementos como los bordes serrados y los remaches.[CA] Els satèl·lits de telecomunicació operen en entorns multiportadora, sota una demanda contínua de majors capacitats de transmissió. Això ha originat un augment en els nivells de potència de *RF, freqüències de treball, i nombre de canals transmesos, estimulant l'aparició d'efectes no lineals d'alta potència, com *Multipactor, Corona, i la Intermodulació Passiva (*PIM). Entre els efectes anteriors, el *PIM és el menys comprés, a causa del seu caràcter no lineal i la seua estreta relació amb la fabricació, la qual cosa dificulta el desenvolupament de models fiables. Els termes de *PIM generats en l'enllaç descendent poden interferir al feble senyal en el canal de recepció, amenaçant la capacitat de recepció de l'enllaç ascendent. Els models tradicionals de *PIM solen basar-se en una excitació formada per dues portadores. Encara que es tracta d'un cas simple i bastant representatiu, presenta diferències importants amb l'escenari real multiportadora. El treball d'aquest *Ph.D. intenta reduir aquestes diferències. Per a aconseguir-ho, es realitzen dues noves contribucions de rellevància per a les condicions reals d'operació dels satèl·lits . En concret, s'ha investigat de manera teòrica el rol de les fases de les portadores en el *PIM, i s'ha proposat un nou model que té en compte l'efecte de les portadores no contribuents en un cert terme de *PIM, aplicant un nou principi de conservació d'energia. Els resultats obtinguts amb tots dos models teòrics s'ajusten a les dades experimentals. A causa de la complexa naturalesa del *PIM, la validació dels components de *RF de satèl·lits es realitza mitjançant tests. Per tant, la disponibilitat de bancs de mesura de *PIM és un tema d'interés per a la indústria espacial. No obstant això, el disseny de bancs d'altes prestacions és un desafiament, ja que el seu nivell de *PIM ha de ser inferior al requerit per a validar els dispositius. Per a maquinari de satèl·lits , la diferència entre el nivell de les portadores a transmetre i el senyal de *RF a detectar és com 185 *dBc. En aquest *Ph.D. es proposen unes noves arquitectures integrades de bancs de *PIM en guia d'ones, que cobreixen tant el *PIM conduït com el radiat. Aquestes arquitectures permeten una reducció important del nivell de *PIM residual del sistema de mesura, sent flexibles, capaces de manejar elevats nivells de potència, i lliures de ressonàncies i interaccions indesitjades. Els elements claus d'aquests bancs són uns multiplexors de baix *PIM, que poden incorporar dues famílies de filtres que admeten un elevat nombre de zeros de transmissió, i per tant, són capaces de proporcionar un elevat rebuig en la banda de recepció del *PIM. Els bancs de mesura de *PIM conduït per ona reflectida, no obstant això, estan exposats al *PIM generat per la càrrega emprada per a absorbir les portadores d'alta potència. Per a resoldre aquesta situació, s'han proposat unes noves càrregues de baix *PIM, que redueixen el *PIM residual d'aquests sistemes de mesura. Així mateix, s'ha elaborat un nou tipus de transició per a mitigar el *PIM respecte a *flanges estàndard. Per a escenaris radiats s'ha desenvolupat una formulació capaç de relacionar densitats de potència en el dispositiu sota test amb els nivells detectats en el banc de mesura, i que per tant permeten traslladar especificacions de *PIM del satèl·lit al sistema de mesura. Finalment, s'han mostrat diverses campanyes de mesura de *PIM realitzades amb bancs implementats concorde a les noves arquitectures proposades. Les mesures cobreixen diverses bandes de freqüència i diferents escenaris (tant *PIM conduït com radiat). S'ha determinat l'excepcional nivell de fons de soroll de *PIM reeixit en cada banc. A més, s'han mostrat resultats obtinguts per a mesures de *PIM radiat en capes aïllants multicapa i malles reflectores, obtenint interessants conclusions quant a geometries i impacte que tenen en el *PIM elements com les vores serrades i els reblons.[EN] Modern satellite payloads operate in multicarrier scenarios, under a continuous demand for higher capacity links. This leads to an increase in the RF power levels, frequency of operation, and the number of transmitted channels, thus stimulating non-linear high-power effects, such as Multipactor, Corona, thermal issues and Passive Inter-Modulation (PIM). Among the above-mentioned phenomena, PIM is the less studied, or, at least, understood. This is due to its extreme non-linear nature and its close relation to workmanship, which make very difficult the development of models able to faithfully predict and explain PIM degradation. PIM terms, once ignited in the downlink, may interfere the weak signal to be detected in the uplink channel, thus threatening the payload throughput. Traditional PIM models are based on a two-carriers excitation. This is a simple and quite representative case, but has significant differences with the real multi- carrier scenario. This Ph.D. thesis work tries to diminish this gap by two novel contributions of relevance for real operation conditions. Firstly, the role of the carrier phases (neglected for two-carriers excitation) has been theoretically investigated. Secondly, a new model to account for the effect of non-contributing carriers for a given PIM term has been developed, which is based on a novel energy conservation assumption. The resulting models fit to experimental data. Due to the complexity of PIM modeling, PIM validation of RF components is conducted only by testing. The availability of low PIM test set-ups is therefore of great interest for the space industry. However, the design of low PIM test benches is challenging, as their intrinsic residual PIM has to be below the one requested to validate the test devices. For satellite hardware, the dynamic range between the RF power levels of the transmission carriers and the signal to be detected may be 185 dBc. During this Ph.D. thesis work, novel integrated test bed architectures in waveguide technology, both for conducted and radiated PIM scenarios, have been developed. These architectures consent a mitigation of the residual PIM of the test facility, being at the same time flexible, free from unwanted interactions and spurious resonances, and able to withstand considerable RF power levels for the transmission carriers. The key elements of these set-ups are the low PIM multiplexers, which may integrate two new families of waveguide filters able to provide a high number of transmission zeros, and therefore a high rejection, in the PIM reception channel. The test benches conceived for measuring conducted backward PIM, however, are normally unprotected from the PIM generated by the termination absorbing the high-power transmission carriers. To alleviate this situation, a new type of low PIM terminations in waveguide technology has been proposed and verified with PIM tests, showing a clear benefit in mitigating the residual PIM of the test facilities. Moreover, novel transitions able to improve the PIM performance of standard flanges have also been conceived. Finally, and with regard to radiated scenarios, a novel formulation able to convert payload PIM specifications to a practical PIM test is proposed. This formulation consents to link the power flux densities at the device under test (DUT) with the RF power levels measured by the test bench. Last, a large class of PIM measurements carried out with the novel test bed architectures have been reported. These measurements cover several frequency bands (C-, Ku-, K- and Ka) and different PIM scenarios, both conducted and radiated. The exceptional residual PIM noise floor of each test bed will be pointed out. In addition, PIM tests on an anechoic chamber facility, multi-layer insulation blankets (MLIs) and reflector mesh samples are presented, with interesting considerations about the geometry of the structure and the impact on the PIM performance of typical elements as sawing areas and rivets.Smacchia, D. (2022). Advanced Techniques for the Characterization and Experimental Validation of Passive Inter-Modulation Effect (PIM) in Space Communications Systems [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/182402TESI

Radio over fiber broadband access networks architectures based on wavelength division multiplexing techniques

The recent remarkable growth in bandwidth of both wired optical and wireless access networks supports a burst of new high bandwidth Internet applications such as: peer-topeer file sharing, cloud storage, on-line gaming, video streaming, etc. Within this scenario, the convergence of fixed and wireless access networks offers significant opportunities for network operators to satisfy user demands, and simultaneously reduce the cost of implementing and running separated wireless and wired networks. The integration of wired and wireless network can be accomplished within several scenarios and at several levels. In this thesis we will focus on converged radio over fiber architectures, particularly on two application scenarios: converged optical 60 GHz wireless networks and wireless overlay backhauling over bidirectional colorless wavelength division multiplexing passive optical networks (WDM-PONs). In the first application scenario, optical 60 GHz signal generation using external modulation of an optical carrier by means of lithium niobate (LiNbO3) Mach- Zehnder modulators (MZM) is considered. The performance of different optical modulation techniques, robust against fiber dispersion is assessed and dispersion mitigation strategies are identified. The study is extended to 60 GHz carriers digitally modulated with data and to systems employing subcarrier multiplexed (SCM) mm-wave channels. In the second application scenario, the performance of WDM-PONs employing reflective semiconductor optical amplifiers (RSOAs), transmitting an overlay orthogonal frequency-division multiplexing (OFDM) wireless signal is assessed analytically and experimentally, with the relevant system impairments being identified. It is demonstrated that the intermodulation due to the beating of the baseband signal and wireless signal at the receiver can seriously impair the wireless channel. Performance degradation of the wireless channel caused by the RSOA gain modulation owing to the downstream baseband data is also assessed, and system design guidelines are provided.Universidade do Algarve, Faculdade de Ciências e Tecnologi

Radio over fiber broadband access networks architectures based on wavelength division multiplexing techniques

The recent remarkable growth in bandwidth of both wired optical and wireless access networks supports a burst of new high bandwidth Internet applications such as: peer-topeer file sharing, cloud storage, on-line gaming, video streaming, etc. Within this scenario, the convergence of fixed and wireless access networks offers significant opportunities for network operators to satisfy user demands, and simultaneously reduce the cost of implementing and running separated wireless and wired networks. The integration of wired and wireless network can be accomplished within several scenarios and at several levels. In this thesis we will focus on converged radio over fiber architectures, particularly on two application scenarios: converged optical 60 GHz wireless networks and wireless overlay backhauling over bidirectional colorless wavelength division multiplexing passive optical networks (WDM-PONs). In the first application scenario, optical 60 GHz signal generation using external modulation of an optical carrier by means of lithium niobate (LiNbO3) Mach- Zehnder modulators (MZM) is considered. The performance of different optical modulation techniques, robust against fiber dispersion is assessed and dispersion mitigation strategies are identified. The study is extended to 60 GHz carriers digitally modulated with data and to systems employing subcarrier multiplexed (SCM) mm-wave channels. In the second application scenario, the performance of WDM-PONs employing reflective semiconductor optical amplifiers (RSOAs), transmitting an overlay orthogonal frequency-division multiplexing (OFDM) wireless signal is assessed analytically and experimentally, with the relevant system impairments being identified. It is demonstrated that the intermodulation due to the beating of the baseband signal and wireless signal at the receiver can seriously impair the wireless channel. Performance degradation of the wireless channel caused by the RSOA gain modulation owing to the downstream baseband data is also assessed, and system design guidelines are provided.Universidade do Algarve, Faculdade de Ciências e Tecnologi

Integrated Filters and Couplers for Next Generation Wireless Tranceivers

The main focus of this thesis is to investigate the critical nonlinear distortion issues affecting RF/Microwave components such as power amplifiers (PA) and develop new and improved solutions that will improve efficiency and linearity of next generation RF/Microwave mobile wireless communication systems. This research involves evaluating the nonlinear distortions in PA for different analog and digital signals which have been a major concern. The second harmonic injection technique is explored and used to effectively suppress nonlinear distortions. This method consists of simultaneously feeding back the second harmonics at the output of the power amplifier (PA) into the input of the PA. Simulated and measured results show improved linearity results. However, for increasing frequency bandwidth, the suppression abilities reduced which is a limitation for 4G LTE and 5G networks that require larger bandwidth (above 5 MHz). This thesis explores creative ways to deal with this major drawback. The injection technique was modified with the aid of a well-designed band-stop filter. The compact narrowband notch filter designed was able to suppress nonlinear distortions very effectively when used before the PA. The notch filter is also integrated in the injection technique for LTE carrier aggregation (CA) with multiple carriers and significant improvement in nonlinear distortion performance was observed. This thesis also considers maximizing efficiency alongside with improved linearity performance. To improve on the efficiency performance of the PA, the balanced PA configuration was investigated. However, another major challenge was that the couplers used in this configuration are very large in size at the desired operating frequency. In this thesis, this problem was solved by designing a compact branch line coupler. The novel coupler was simulated, fabricated and measured with performance comparable to its conventional equivalent and the coupler achieved substantial size reduction over others. The coupler is implemented in the balanced PA configuration giving improved input and output matching abilities. The proposed balanced PA is also implemented in 4G LTE and 5G wireless transmitters. This thesis provides simulation and measured results for all balanced PA cases with substantial efficiency and linearity improvements observed even for higher bandwidths (above 5 MHz). Additionally, the coupler is successfully integrated with rectifiers for improved energy harvesting performance and gave improved RF-dc conversion efficienc

Radio Frequency Interference Impact Assessment on Global Navigation Satellite Systems

The Institute for the Protection and Security of the Citizen of the EC Joint Research Centre (IPSC-JRC) has been mandated to perform a study on the Radio Frequency (RF) threat against telecommunications and ICT control systems. This study is divided into two parts. The rst part concerns the assessment of high energy radio frequency (HERF) threats, where the focus is on the generation of electromagnetic pulses (EMP), the development of corresponding devices and the possible impact on ICT and power distribution systems. The second part of the study concerns radio frequency interference (RFI) with regard to global navigation satellite systems (GNSS). This document contributes to the second part and contains a detailed literature study disclosing the weaknesses of GNSS systems. Whereas the HERF analysis only concerns intentional interference issues, this study on GNSS also takes into account unintentional interference, enlarging the spectrum of plausible interference scenarios.JRC.DG.G.6-Security technology assessmen

Adaptive optical feedforward linearization of optical transceiver for radio over fiber communication link

With the tremendous growth in numbers of mobile data subscribers and explosive demand for mobile data, the current wireless access network need to be augmented in order to keep up with the data speed promised by the future generation mobile network standards. Radio over fiber technology (RoF) is a cost effective solution because of its ability to support numerous numbers of simple structured base stations by consolidating the signal processing functions at the central station. RoF systems are analog systems where noise figure and spurious free dynamic range (SFDR) are important parameters in an RoF link. The nonlinearity of a laser transmitter is a major limiting factor to the performance of an RoF link, as it generates spurious spectral components, leading to intermodulation distortions (IMD), which limit the achievable SFDR of the analog RF wave transmissions. The device nonlinearity can be mitigated through various linearization schemes. The feedforward linearization technique offers a number of advantages compared to other techniques, as it offers good suppression of distortion products over a large bandwidth and supports high operating frequencies. On the other hand, feedforward linearization is a relatively sensitive scheme, where its performance is highly influenced by changing operating conditions such as laser aging, temperature effect, and input signal variations. Therefore, for practical implementations the feedforward system has to be real-time adaptive. This thesis aims to develop an adaptive optical feedforward linearization system for radio over fiber links. Mathematical analyses and computer simulations are performed to determine the most efficient algorithm for the adaptive controller for laser transmitter feedforward linearization system. Experimental setup and practical measurement are performed for an adaptive feedforward linearized laser transmitter and its performance is optimized. The adaptive optical feedforward linearization system has been modeled and simulated in MATLAB Simulink. The performances of two adaptive algorithms, which are related to the gradient signal method, such as least mean square (LMS) and recursive least square (RLS) have been compared. The LMS algorithm has been selected because of its robustness and simplicity. Finally, the adaptive optical feedforward linearization system has been set up with digital signal processor (DSP) as the control device, and practical measurement has been performed. The system has achieved a suppression of 14 dB in the third order IMD products over a bandwidth of 30 MHz, in a two-tone measurement at 1.7 GHz