4.1 General Considerations Figure 4.2.Hypothetical filter to suppress an interferer. A 900-MHz GSM receiver with BPF 200-kHz channel spacing must Response tolerate an alternate adjacent 20 dB 35 dB channel blocker 20 dB higher than the desired signal. Calculate the Q of a second-order 900 900.4 f(MHz) LC filter required to suppress this interferer by 35 dB. Equation 4.2 Lo2 ZT(j@)2= (1-LCw2)2+L2w2/R2 For an attenuation of 35 dB(=56.2) Equation 4.3 at 900.4 MHz,this quantity must be Lo2 equal to R2/56.22 (why?).Solving for R2 =2.504×10-10 L202/R2,we obtain Recall from Chapter 2 that Q=R/(Lw)=63,200.4.1 General Considerations A 900-MHz GSM receiver with 200-kHz channel spacing must tolerate an alternate adjacent channel blocker 20 dB higher than the desired signal. Calculate the Q of a second-order LC filter required to suppress this interferer by 35 dB. For an attenuation of 35 dB ( = 56.2) at 900.4 MHz, this quantity must be equal to R2/56.22 (why?). Solving for L2ω2/R2, we obtain