This master’s thesis describes RF power amplifier design. The designed amplifier has been built. The first three chapters outline basics about radio frequency amplifiers. The basic theory needed for amplifier implementation is also described there. In the fourth chapter the power amplifier is designed. The design is based on the theoretical knowledge. Complete amplifier contains RF preamplifier, power amplifier and filters. The OrCAD PSpice, Ansoft Designer SV and EAGLE programs have been used for the design and verification of some sections of circuits. Measurement results of the built amplifier are in the fifth chapter. This thesis contains also the draft for laboratory exercise.

Hearing loss of various types is increasingly plaguing our modern world (Geneva: World Health Organization 2018). As the life expectancy increased in the industrialized world, age-related hearing loss (ARHL) has become more prevalent. The wars and terrorism of the modern world also created a significant body of blast-induced hearing loss (BIHL) patients. Both types of hearing loss present significant challenges for listeners even at suprathreshold sound levels. However, increasing bodies of clinical and laboratory evidence have suggested that the difficulties in the processing of time-varying auditory features in speech and other natural sounds may not be sufficiently diagnosed by threshold changes and simple auditory electrophysiological measures (Snell and Frisina 2000; Saunders et al. 2015; Bressler et al. 2017; Guest et al. 2018).<br>Studies have emphasized that excitatory/inhibitory neurotransmission imbalance plays important roles in ARHL (Caspary et al. 2008) and may also be key in BIHL, as hinted by the strong presence of GABA regulation in non-blast TBI (O’Dell et al. 2000; Cantu et al. 2015; Guerriero et al. 2015). The current studies focus on age-related and blast-induced hearing deficits by examining changes in the processing of simple, brief stimuli and complex, sustained, temporally modulated sounds.<br>Through post hoc circular analysis of single-unit, in vivo recording of young and aged inferior colliculus (IC) neurons responding to amplitude modulation (AM) stimuli and modulation depth changes, we observed evidence of central compensation in the IC manifesting as increased sensitivity to presynaptic input, which was measured via local field potentials (LFPs). We also found decreased sensitivity to decreasing modulation depth. Age-related central gain in the IC single units, while preserving and even overcompensating for temporal phase coding in the form of vector strength, was unable to make up for the loss of envelope shape coding.<br>Through careful, longitudinal measurements of auditory evoked potential (AEP) responses towards simple sounds, AM and speech-like iterated rippled noise (IRN), we documented the development and recovery of BIHL induced by a single mild blast in a previously established (Song et al. 2015; Walls et al. 2016; Race et al. 2017) rat blast model over the course of two months. We identified crucial acute (day 1-4 post-exposure) and early recovery (day 7-14) time windows in which drastic changes in electrophysiology take place. Challenging conditions and broadband, speech-like stimuli can better elucidate mild bTBI-induced auditory deficits during the sub-acute period. The anatomical significance of the aforementioned time windows was demonstrated with immunohistochemistry methods, showing two distinct waves of GABA inhibitory transmission changes taking place in the auditory brainstem, the IC, and the auditory thalamus. These changes were in addition to axonal and oxidative damage evident in the acute phase. We examined the roles and patterns of excitatory/inhibitory imbalance in BIHL, its distinction compared to that of ARHL, and demonstrated the complexity of its electrophysiological consequences. Blast traumatizes the peripheral auditory system and auditory brainstem, evident through membrane damage and acrolein-mediated oxidative stress. These initial traumas kickstart a unique, interlocking cascade of excitatory/inhibitory imbalances along the auditory neuraxis that is more complex and individually varied than the gradual, non-traumatic degradations in ARHL. Systemic treatment with the FDA-approved acrolein scavenger Hydralazine (HZ) was attempted with limited effects.<br>Taken together, the current study provided insights into the similarities and distinctions between the mechanisms of ARHL and BIHL and called for innovative and individual diagnostic and therapeutic measures.<br>

Research in vocal vibrato has established that vocal tract filtering is primarily responsible for the amplitude modulation (AM) present in Western classical vibrato. Using electroglottography (EGG) and the EGG speed quotient, which is sensitive to fluctuations in the amplitude of vocal fold vibration, AM was detected at the laryngeal (source) level, in addition to the subsequent AM which results from vocal tract filtering. Seventeen classically-trained opera singers sang vowels in three pitch and loudness conditions. EGG and microphone measurements of FM and AM and their rates, extents, and periodicity were made. Airflow was also measured, and the samples were rated by voice professors for vibrato consistency, speed, and width. Physiologic and acoustic data revealed that AM from vocal tract filtering, or the resonance-harmonics interaction (RHI) described by Horii and associates, was present throughout the vibrato samples. Laryngeal-level AM was also present throughout, with soft conditions having the highest mean extents. Singers with lower degrees of laryngeal-level AM were also those rated highest for vibrato consistency. Vibrato rate increased as pitch increased, and, to a lesser extent, as intensity increased. These findings document, in addition to the AM resulting from the RHI, the concurrent presence of laryngeal-level AM in a group of singers representing a range of training and experience.

Amplitude and phase modulated optical OFDM (Orthogonal Frequency Division Multiplexing) are analyzed in a 50GBit/s single channel and 40GBit/s 5 channel 512 subcarrier non-ideal dispersion-compensated fiber optic communication systems. PM-OFDM is investigated as an alternative to AM-OFDM to alleviate the problem associated with amplitude-modulated signals in a nonlinear medium. The inherent dispersion compensation capability in OFDM (using a cyclic prefix) allows transmission over a link whose dispersion map is not exactly known. OFDM also mitigates the effects of dispersion slope in wavelength-division multiplexed (WDM) systems. Moreover, the overall dispersion throughout the transmission link may vary due to environmental effects and aging. OFDM is inherently tolerant to over- or under-compensation and dispersion slope mismatch. OFDM transmission over dispersive, non-dispersion managed fiber links using OFDM requires an overhead in excess of the maximum accumulated dispersion. Existing WDM systems usually employ periodic dispersion management. OFDM in these systems requires a smaller overhead. It is, however, more susceptible to nonlinearity due to the coherent beating of subcarriers after each dispersion-compensated span. The large variation in intensity associated with amplitude-modulated OFDM makes this modulation format more susceptible to nonlinear effects in fiber compared to phase-modulated signals. This holds true unless dispersion and EDFA noise lead to amplitude variations strong enough for PM-OFDM to be degraded by nonlinear effects as well. In conclusion OFDM is beneficial for non-ideal dispersion managed systems. PM-OFDM can further improve the performance.

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Várias técnicas de cifragem óptica de imagens surgem a todo o momento devido à necessidade que se tem de transmitir informações de uma maneira segura e confiável. Nessas técnicas a informação é criptografada de tal modo que para conseguir recuperar a informação criptografada é necessário ter um conhecimento prévio da mesma chave que a criptografou, sendo esta chave única. Isto faz com que as técnicas sejam robustas. Estes processos de cifragem de imagem trabalham com a distribuição de fase obtida diretamente da imagem que se deseja criptografar e conseqüentemente a imagem decodificada também está em modulação de fase. Porém imagens em distribuição de fase não são visíveis ao olho humano. Para transformá-Ias em modulação de amplitude, a qual é visível ao olho humano, é utilizado o método de contraste de fase de Zernike. Propôs-se então um método para cifrar imagem binária apenas em modulação de amplitude. Após o processo de decodificação, a imagem obtida é reconhecida graças à capacidade do olho humano em discernir regiões contínuas de regiões aleatórias. Este método é de fácil implementação, podendo ser obtido utilizando apenas materiais de baixo custo como papéis, filmes plásticos, etc. Vários ataques foram realizados contra o processo de cifragem óptica de imagens utilizando máscara binária aleatória para analisar a robustez de tal processo. Este processo de cifragem não é robusto ao ataque do texto conhecido e ao ataque das cifras conhecidas. / Several optical encryption techniques have been developed due to the need to transmit information in a secure and reliable way. In these techniques the information is encrypted in a way that to recover the encrypted information is necessary to have a previous knowledge of the same mask that encrypted it, being this mask unique. Because of this, the techniques are robust. These image encryption methods work with the phase distribution obtained directly from the image that is intended to encrypt and consequently the decrypted image will also be in the phase modulation. But, images in a phase distribution are not visible for the human eyes. To transform them in an amplitude modulation, that is visible for the human eyes, it is used the Zernike phase contrast method. Then, it is proposed a method for encryption and decryption of information processed in a binary form in an amplitude modulation. After the decryption process, the image obtained is recognized because the human eyes are able to differentiate continuous, periodical regions to random pattern. This method has an easy implementation and it can be obtained using regular and inexpensive materials, like paper, plastic films, etc. Many attacks were realized against the proposed method to analyse if this method is robust. This method can not resist the known-plaintext attack and the known-ciphertext attack.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Neste trabalho, apresentamos uma anÃlise numÃrica para a obtenÃÃo de portas lÃgicas totalmente Ãptica baseada em um acoplador direcional nÃo-linear simÃtrico (NLDC) em fibras de cristal fotÃnico (PCF). O projeto mais comumente usado para o NLDC-PCF à uma fibra holey, utilizada neste trabalho, em que a seÃÃo transversal à uma matriz periÃdica de buracos de ar que se prolonga por todo o comprimento da fibra, operando com dois pulsos de luz ultracurtos na forma de sÃlitons, de duraÃÃo mÃnima de 100fs (femtosegundos). Investigamos dois formatos de modulaÃÃo por pulsos, a modulaÃÃo por amplitude de pulso (PAM) na modalidade de chaveamento de mudanÃa de amplitude (ASK) e a modulaÃÃo por largura de pulso (PWM) para obter portas lÃgicas no NLDC-PCF duplo simÃtrico. Avaliamos o efeito resultante de um incremento no parÃmetro codificaÃÃo PAM (&#949;) e PWM (w), considerando a dispersÃo de segunda ordem (&#946;2), a dispersÃo de terceira ordem (&#946;3) e efeitos nÃo-lineares, tais como: SPM (Self Phase Modulation), SS (Self-Steepening) e IRS (lntrapulse Raman Scattering) em uma configuraÃÃo sem perdas. Os nossos resultados indicam que à possÃvel obter operaÃÃes lÃgicas utilizando um controle de fase entre os pulsos de entrada. / We present a numerical analysis for obtaining all-optical logic gates based on a nonlinear directional coupler symmetric (NLDC) based on photonic crystal fibers (PCF). The most commonly used to project the NLDC-PCF is a holey fiber, used here in cross section which is a periodic array of air holes extending through the length of the fiber, using two ultrashort light pulses in form of solitons, the minimum duration of 100fs (femtoseconds). We investigated two forms of modulation pulse, pulse amplitude modulation (PAM) in the form of amplitude shift keying (ASK) modulation and pulse width modulation (PWM) for logic gate NLDC-PCF symmetrical double. We evaluated the effect resulting from an increase in the offset parameter encoding PAM (&#949;) and PWM (w), considering the second order dispersion (&#946;2), the third order dispersion (&#946;3) and non-linear modulation effects SPM (Self Phase Modulation), SS (Self-Steepening) and IRS (lntrapulse Raman Scattering) in a configuration without loss. Our results indicate that logical operations can be obtained using a phase control between the input pulses.