tailieunhanh - Ultra Wideband Part 6

Tham khảo tài liệu 'ultra wideband part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 144 Ultra Wideband performed in the case of linear modulations OOK BPSK PAM for which the transmit signal s t and its PSD Sss f are expressed as s t K-J qkg t - kTk 4 k 0 2 2 Sss f yL G f 2 T lG f 2 Wps f 5 1 s 1 s where qk is a random sequence with mean value ụq and variance ơq g t is the pulse waveform and G f its Fourier transform. This analysis especially gives the potential of OOK and BPSK modulations in terms of detection and data rate in order to see which types of applications they are compatible with. Lastly we assume here an ideal pulse with a spectrum defined by the FCC or ECC masks in order to evaluate the maximum theoretical amplitude value and the associated data rate value. . Mean PSD The mean PSD of a UWB signal is limited by the masks shown in Fig. 4 Fig. 4. FCC and ECC masks If we ignore the power in the unallocated bands the spectrum of the signal with the best spectral occupation is given by equation 3 . It is a square function with a width BWTOT defined by the allocated band and which is centred on the middle of this band fo . Its inverse Fourier transform gives the ideal base pulse equation 0 . G f G0 rn_ f - f0 II. f f0 0 Bw tot 0 BW TOT 0 g t .sinc GBG t .cos 2v f0t 6 7 Pulse generator design 145 with for the FCC standard BWtot GHz and f0 GHz and for the ECC standard BWtot GHz and f0 GHz. The peak amplitude of the ideal pulse is then given by go 2G0 BWtot 8 The ECC and FCC standards require the use of a spectrum analyser whose resolution filter bandwidth RBWav is set to 1 MHz. The measured PSD single-sided can then be expressed as follows from 0 DSPf - .-bW DsW 9 Zo For both standard the maximum value of the average PSD is set to dBm MHz and can be expressed as follows 2ơ2 . 2u2 i D RBwG -dSg0 Ị. 10-7 13 10 s av 0 S 0 Zo Zo I Using 0 and 0 it is then possible to establish a relationship between the maximum amplitude allowed by the standard and the symbol rate as follow g0max min 2 DRBWvrt 1 2