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?