UWB_Lecture03_v2 - Ultrawideband systems: Fundamentals and...

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1 1 Ultrawideband systems: Fundamentals and Standardization Lecture 3 Min-Kuan Chang National Chung Hsing University 教育部通訊教改計畫 教育部通訊教改計畫 2 Outline • Ultra wideband waveforms
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2 3 Ultra wideband waveforms • Pulse-based transmission was the first implemented by Hertz in 1893 – However, to let signals from different transmitters be received selectively, sinusoidal waves becomes dominant • FCC ruling for emissions in UWB – Intentional radiators that produce class B emissions are prohibited 4 Ultra wideband waveforms Class B Emission • According to FCC Part 15, Section 15.3 – A class B digital device is one that is “marketed for use in a residential environment notwithstanding use in commercial, business and industrial environments” • Examples of such devices include, but are not limited to, personal computers, calculators, and similar electronic devices that are marketed for use by the general public."
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3 5 Ultra wideband waveforms Class B Emission • A damped wave has the following form () ( ) t f Ae t p c t π λ 2 sin = An arbitrary amplitude The exponential decay coefficient () f j f f A f f P c c πλ 4 4 2 ) ( 2 2 2 + = Fourier Transform 6 Ultra wideband waveforms Class B Emission G f A c 5 . 1 and 2 . 1 , 1 . 1 = = =
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4 7 Ultra wideband waveforms Class B Emission • The spectrum of Class B waveform – contains sharp peak in the spectrum – causes sever interference with the existing services if used in UWB 8 Ultra wideband waveforms • Features of pulses used in UWB – Time duration is on the order of nanoseconds • Hard to interception • Results in ultra-wide spectrum – Zero DC if possible • Pulse radiate more effectively • The choice of pulses would have impact on – the design of filters – the receiver bandwidth – antenna design – BER performance – multipath performance
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5 9 Ultra wideband waveforms Gaussian waveform 10 Ultra wideband waveforms Gaussian waveform • Mathematically similar to the Gaussian function • The basis of Gaussian waveforms is a Gaussian pulse () 2 2 2 2 2 1 σ πσ x e x G = 2 1 1 g = τ t e K t p a constant a time-scaling factor ( ) 2 1 1 f g e K f P πτ π =
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6 11 Ultra wideband waveforms Gaussian waveform • Gaussian monocycles – The first derivative of a Gaussian pulse – One zero crossing – Fourier transform () 2 2 2 2 2 = τ t g e t K t p ( ) ( ) 2 2 2 2 f g e f j K f P πτ π = 12 Ultra wideband waveforms Gaussian waveform • Gaussian doublet – The second derivative of a Gaussian pulse – Double zero crossings – Fourier transform 2 3 2 2 3 3 2 1 2 = t g e t K t p ( ) 2 3 2 3 2 f g e f j K f P =
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7 13 Ultra wideband waveforms Gaussian waveform -3 -2 -1 0 1 2 3 x 10 -8 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 x 10 8 Gaussian Doublet t τ = 10 -9 τ = 3*10 -9 τ = 5*10 -9 τ = 7*10 -9 τ = 9*10 -9 14 Ultra wideband waveforms Gaussian waveform • Pulse shapes that are successively higher
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UWB_Lecture03_v2 - Ultrawideband systems: Fundamentals and...

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