Question

Problem As a communications system engineer, you are asked to setup a communication system to serve a distance of 100m using an access point transmitting signals with power 20dBm at the frequency 2.4GHz. The antennas used at the transmitter and receiver side have the gains shown in the picture below. The coaxial cables used to interface the systems to the antennas have losses shown in the picture below. What is the received signal power in dBm at the input of the Rx radio receiver (point A)? What is the Rx radio sensitivity needed to have a margin of 10dB at the input of the Rx radio receiver (point A)? Assuming a • Rx radio receiver with noise figure 6dB and bandwidth 5MHz • Receiveing antenna operating at 290 K find the signal to noise ratio at the receiving antenna terminals (point B). antenna +10 dBi antenna +14 dBi point A +20 dBm YA Тх cable -2 dB radio Rx radio cable -2 dB point B

Answer 1

pooblem- is dBi She dollowing concept is very important before slow to solve this dB with respeel to id bopič Anlenng, so S. dBi is a nolehion which can be used as dB. 2 dBm dBm + dB Whenerd you in one another, where dB add unils OB and dBm need not to convert just Waile the restent as dBm. 10 log lower) dBm = 10 log l Power 10-3 Transmitter Anlenna Receiver Anlenna +14dBi = Gr 2 Gita +10dBi 23 +20dBm Por PH A d- Cable Tx Radio Rx Radio Cable B -2dB 22dB Le = 2 dB PTX Radio Griven Cable Losses Distance blw Two onlennas de doom 20dBm Power Ab Tx Radio Frequency } = 2.4 GH2 = 2.2.4x10? Hz Chain of Te Anlenna =GE = 10 dBi Grain of Rr Antenna = Go = 14 dBi Power at the Trammiltu Anlenna , Let that point Power cel the Tx Anlenna = Preradio - Le сы Pt = 18dBm Slebt! Delumine 200BM-2dB Ganned with CamScanner

slandard According Jay 1 8x108 22 = speed of light in Air Sleb2 Delamine Power of Receines Anlemne with Ho use of FRIIS Equation. to FRITS Equahon, Power Received Po es giren Ph = Pc Gt Gr la ind) ² = Pt Gear Lis PorldB) = PaldB) + 6+ (dB) + GoldB) 4s (dB) When LA : Free space Path loss (4ady? ANNO when 2 : Wavelength of the operating wave. 2.4x109 Frequency 2= 1/3 m Pueving value of a to calculate 44 43 = (4 x 100 x 8) 80 dB 43(dB) = 10 dog (4) Now we have : PrldB): 18 dBm G4 (dB) = 10 dBi i Guldb): 14dBi ; Pulling all these parumlu in eah ①, we get PoldB) = PoldB) = -38 dBm Received Power By Antenna cslepa in Dele, mine power al desired point A. 1.01 X109 - 1 460) () = 80 dB - 18+ 10+ 14 80 CamScanner

Power at Point A PA = Pouce Receumet Log Anlenne Cable Loss PA = Pr Pr - Pale : - 38 - 2 6 Received Power in dem - 40 dBm at the ilp of Rx Radio Receiver Am Part. B Radio Recure Sensity (Sv) es given given by the following for malo Sr (dB) = N(dB) + F(dB) + (SNR loin when NH : Thermal Noise f: Moise Jigure of Rx = 608 (SNRmin: Mumm Sanal to noise Reho Required the Receiru also known as the margin of the receive 16 dB 2 leg So (SNR)min = Now Thamel Aloise Nz=KTB Wher k= Bollgren Complant = 1.38X10-28 Ilk. T: Temperature of the Re = 290k 8: Receiver Band width 5X106 Hz. 2 So ME 1.38 x1023x230 x 5 X106 H2 — Watt - 2 x 10-14 10 log Ne NildB) CamScan MdB) Scanned with CS - 137 dB

Pulling all the baromelino in voquchon SoldB) -137 dB + 6 dB +10 dB SoldB) -1210dB So Rx radio Sensitivity Sy hequired to have a mapin of 10 dB is Sr - 121 dB Are