Question

Band filter frontend Filter LNA NEOL QB 88-108MHZ -108MHO LNA 1db=Mf зав Les AH 6- A 16 dB which configuration is better fer frontend if there is high interferance I (a) is better discus ? b) (b) is better to preduce the best Performance discus Scanned with CamScanner

Answer 1

The term ‘frontend’ is basically used in the radio receiver circuit. It starts from the receiver antenna and ends on the mixer with a local oscillator stage. As such kind of circuit is mostly used in the receiver stage; hence, it is always desirable to down-convert the signal before employing the filtering stage. Therefore, a better configuration is the option (b) for the frontend.

a)   The radio-frequency interference is mainly occurred due to the disturbance produced by an external source that affects the electrical conductivity. As a result of this, the performance of the circuit is degraded.
In configuration a), Band-pass filter (BPF) is applied before the low-noise amplifier (LNA) stage; hence, the received signal is filtered first, then the noise inside the filtered signal is removed by LNA. Therefore, in the filtered signal, the noise signal may also present which mainly generates high interference.

b)   On configuration b), LNA is applied before the BPF. Therefore, the noise in the received signal is first removed then it is filtered. Hence, the chance of noise source in the filtered signal is very low. Thus it produces the best performance.