Question

Question #2: Consider the wireless local area network (WLAN) receiver front-end shown below, where the bandwidth of the bandpass filter is 100 MHz centered at 2.4 GHz. If the system is at room temperature, find the noise figure of the overall system. What is the resulting signal-to-noise ratio at the output if the input signal power level is-90 dBm? la TLalSdB G-= 20dB

Answer 1

Here no information about the input noise, therefore assume noise generated internally by each block and take this for the calculation of SNR at the output.

Step 1- calculate overall noise figure

Step 2- calculate equivalent noise power at the input

Step 3- SNR at the output.

The los o BPF is gtven as L I ds IL 1-41 Yoom The gain ot BPF, Second ampltun a 9: 20dB 100 The ovivall noise frqn 교 BPF 1, 411+1, 585-1 t. 585-1 t 0 108) x Clo 2-322 Fourvall 3.66 d6 393. 96 K

They the equivalent Aoise pour γ, at the input, /p k.To r all .(Band width = (I, 38x16 23寸1k) x (393.96 k) x (100 x106 Hz 5.44メ1010 mW 10109 (644x101 = Signal inpul level qriven [S/ヲ-120 dB 12o de), therefre, input SNR o dem12.o dB 122. 6 SdB = 02 , 65dB ir. Band width ot 1008Hz) Thevefor, outpat SNR is also wal to c2.65 dB