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Show related SlideShares at end. WordPress Shortcode. Published in: Business , Technology. Full Name Comment goes here. Are you sure you want to Yes No. Preemal Dsouza , Student at st joseph engineering college vamanjoor mangalore at Assistant Professor. Mousa Mousa. Rahul Mathai , Student at Student. No Downloads. Views Total views. Actions Shares. Embeds 0 No embeds. No notes for slide. Satellite communications by dennis roddy 4th edition 1.

Example 9. Calculate the modulation index and the bandwidth. However, for the video signal, for which the deviation ratio is relatively low, the two estimates of bandwidth are In practice, the standard bandwidth of a satellite transponder required to handle this signal is 36 MHz.

The peak frequency deviation of an FM signal is proportional to the peak amplitude of the baseband signal. Increasing the peak amplitude results in increased signal power and hence a larger signal-to-noise ratio. At the same time, AF, and hence the FM signal bandwidth, will increase as shown previously. Although the noise power at the demodulator input is proportional to the IF filter bandwidth, the noise power output after the demodulator is determined by the bandwidth of the baseband filters, and therefore, an increase in IF filter bandwidth does not increase output noise.

Thus an improvement in signal-to-noise ratio 2. Analog Signals is possible but at the expense of an increase in the IF bandwidth. This is the large-amplitude signal improvement referred to in Sec. The noise is represented by the system noise temperature Ts, as will be described in Sec. At the input to the detector, the quantity of interest is the carrier-to-noise ratio. Since both the carrier and the noise are amplified equally by the receiver gain following the antenna input, this gain may be ignored in the carrier- to-noise ratio calculation, and the input to the detector represented by the voltage source shown in Fig.

The carrier root-mean-square rms voltage is shown as Ec. The LF bandwidth W fixes the equivalent postdetector noise bandwidth at 2W. Sf is an infinitesimally small noise bandwidth. It cannot directly frequency modulate the carrier, the frequency of which is determined at the transmitter, which is at a great distance from the receiver and may be crystal controlled.

Now as noted earlier, the available noise power at the input to the detector is kTsBN and the noise spectral density, which is the noise power per unit bandwidth just kTs. Thus the output spectral density as a function of frequency is 2wf 2 kTs. The variation of output spectral noise density as a function of frequency is sketched in Fig.

Since voltage is proportional to the square root of power, the noise voltage spectral density will be proportional to frequency as sketched in Fig. Figure 9. The available noise output power in a very small band df would be given by 2wf 2 kTshf.

The total average noise output power. You just clipped your first slide! Clipping is a handy way to collect important slides you want to go back to later. Now customize the name of a clipboard to store your clips. Visibility Others can see my Clipboard. Cancel Save.


Satellite Communications, Fourth Edition






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