Question

3. The quality of a received signal is often characterized by the signal-to-noise-ratio (SNR), which is defined as SNR 10 log As you might expect from this Signal power in watts KTB definition, the unit of SNR is decibels (dB). The term in the denominator is the noise power, and it is generally specified as an effective noise temperature T multiplied by the product of Boltzmann's constant (K) and the bandwidth (B) of the signal in Hz. Generally we like to have the SNR greater than 10 dB for good quality communications. Use this information along with what you know about how radiated power diminishes over distance to answer the questions below for the following real application. DirecTV transmits signals to Earth from a geosynchronous satellite orbiting about 36,000 km above the Earth's surface. Each HD channel has a bandwidth of 20 MHz. Show that the quantity in brackets in the SNR equation is dimensionally correct. If the signal power transmitted by the DirecTV satellite is measured to be 1.2 W at a distance 1 km from the satellite, and the subscriber's antenna and receiver systems have an effective noise temperature of 125 Kelvin, what is the SNR of the subscriber's signal? a. b.

Answer 1

ven Stqnal pouer n walts kTB Here, Ha denominator has to be, wats because to be diwenstonally Coect uensiona ou b iven abla Hleve, kblan Constant Jouler evin TTeuperature u kelún O W lo Joules Sec coatts s diwen Chonally Correcł