Spreading function and scattering function, Advanced Statistics

1)  Consider an antenna with a pattern:

G(θ,φ) = sinn(θ/θ0) cos(θ/θ0)   where θ0 = Π/1.5

(a) What is the 3-dB bandwidth?

(b) What is the 10-dB beam width?

(c) What is the directivity?

2)  Let  the  transmit  antenna  be  a  vertical λ/2  dipole,  and  the  receive  antenna  a  vertical λ/20 dipole.

(a) What are the radiation resistances at TX and RX?

(b) Assuming ohmic losses due to Rohmic = 10 Ω, what is the radiation efficiency?

3)  Explain the  difference  between  spreading  function  and  scattering  function.  Give examples  of  situations  where  the  information  contained  in  the  time  frequency correlation function RH(Δt, Δf) can be useful.

4)  The coherence  time Tc gives measure of how  long a channel can be considered  to be constant,  and  can  be  approximated  as  the  inverse  of  the  Doppler  spread. Obtain  an estimate of coherence time in Figure 6.7 of Molisch text.

5)  In  a  CDMA  system,  the  signal  is  spread  over  a  large  bandwidth  by  multiplying  the transmitted  symbol  by  a  sequence  of  short  pulses,  also  called  chips.  The  system bandwidth  is thus determined by the duration of a chip.  If the chip duration  is 0.26 μs and  the maximum excess delay  is 1.3 μs,  into how many delay bins do  the multipath components  fall?  If  the  maximum  excess  delay  is  100  ns,  is  the  CDMA  systems wideband or narrowband?

6)  For the COST 207 channel models (created for GSM evaluations),

(a)  Find the rms delay spread of the COST 207 environments RA, TU.

(b) What is the coherence bandwidth of the RA and TU channels?

(c)  Could two different function PDPs have the same rms delay spread?

Posted Date: 2/27/2013 1:18:20 AM | Location : United States

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