Papers by Henrique Miranda
The synthesis of two or more tones simultaneously has numerous applications, including waveform g... more The synthesis of two or more tones simultaneously has numerous applications, including waveform gen- eration, music synthesis and telephone signaling. This paper describes a simulation of a multitone gen- erator using direct digital synthesizer techniques, in a time-shared approach. Each tone frequency-amplitude pair can be independently specie d, as well as the syn- thesizer resolution parameters. Simulation results are also presented under various parameter settings.
IEEE Transactions on Biomedical Circuits and Systems, 2010
HermesD is a high-rate, low-power wireless transmission system to aid research in neural prosthet... more HermesD is a high-rate, low-power wireless transmission system to aid research in neural prosthetic systems for motor disabilities and basic motor neuroscience. It is the third generation of our "Hermes systems" aimed at recording and transmitting neural activity from brain-implanted electrode arrays. This system supports the simultaneous transmission of 32 channels of broadband data sampled at 30 ks/s, 12 b/sample, using frequency-shift keying modulation on a carrier frequency adjustable from 3.7 to 4.1 GHz, with a link range extending over 20 m. The channel rate is 24 Mb/s and the bit stream includes synchronization and error detection mechanisms. The power consumption, approximately 142 mW, is low enough to allow the system to operate continuously for 33 h, using two 3.6-V/1200-mAh Li-batteries. The transmitter was designed using off-the-shelf components and is assembled in a stack of three 28 mm 28-mm boards that fit in a 38 mm 38 mm 51-mm aluminum enclosure, a significant size reduction over the initial version of HermesD. A 7-dBi circularly polarized patch antenna is used as the transmitter antenna, while on the receiver side, a 13-dBi circular horn antenna is employed. The advantages of using circularly polarized waves are analyzed and confirmed by indoor measurements. The receiver is a stand-alone device composed of several submodules and is interfaced to a computer for data acquisition and processing. It is based on the superheterodyne architecture and includes automatic frequency control that keeps it optimally tuned to the transmitter frequency. The HermesD communications performance is shown through bit-error rate measurements and eye-diagram plots. The Manuscript
softFM: An all-Digital Stereo FM Transmitter with RDS based on Software Radio Architectures
… Conference, Figeira da …, 2001
Nowadays there is a great effort to replace all (or nearly all) the analog components of a commun... more Nowadays there is a great effort to replace all (or nearly all) the analog components of a communication system by architectures using digital hardware, whose functionality can be software configurable using FPGAs and/or DSPs. Radio communication systems based on these new archi- ...
fe.up.pt
This paper describes the realisation of a high-quality, fully digital, stereophonic frequency Mod... more This paper describes the realisation of a high-quality, fully digital, stereophonic frequency Modulation (FM) broadcast system based on Direct Digital Synthesiser (DDS) techniques. After an introduction to DDS technology, the advantages of numeric FM over traditional analogue modulation methods are emphasised. Next, the digital FM transmitter prototype is described. Its main parts include the synthesiser chip, the logic control section, the bandpass filter and the RF amplifier. Finally, some results are presented and possible applications for this system are foreseen.
This paper proposes an alternative architecture for the implementation of Software Defined Radio ... more This paper proposes an alternative architecture for the implementation of Software Defined Radio (SDR) systems, providing low-cost, high degree of flexibility and scalability. The architecture is based on a cluster of COTS (Commercial Off-The-Shelf) computers interconnected by standard network devices (LAN network interface cards and switches). This architecture is mainly intended for testing software radio algorithms in parallel/distributed computing environments capable of real-time processing.
Modulações Multiresolução e sua Aplicação na Difusão Terrestre de Televisão Digital
Resumo Este artigo aborda as modulações hierárquicas e a sua van-tajosa aplicação nos sistemas de... more Resumo Este artigo aborda as modulações hierárquicas e a sua van-tajosa aplicação nos sistemas de difusão digital em geral, e em particular na difusão terrestre de televisão digital [1] E efectuado o tratamento analítico deste tipo de modula cões (também designadas por modulações multiresolução ou fractais) em termos do seu desempenho face ao ruído. São descritos os modos de difusão hierárquico e não-hierárquico do sistema europeu de difusão terrestre de televisão digi-tal [2], cuja norma foi recentemente aprovada pelo ETSI (European Telecommunications Strandards Institute). Fi-nalmente, são apresentados resultados da simulação de um sistema de transmissão hierárquico em conformidade com a norma anterior.
Uploads
Papers by Henrique Miranda