ELEN422-RF Microwave Engineering

Running head: ELEN422 Elen422 Institutional Affiliations Name Date ELEN422 2 ELEN422 3 The above block diagram shows Armstrong's Super Heterodyne Receiver. As shown, The Antenna picks up the weak radio signal and feeds it to the RF Amplifier. The RF Amplifier provides some initial gain and selectivity. The output of the RF Amplifier is applied to the input of the mixer. The mixer also receives an i nput from the local oscillator. The output of mixer circuit is difference frequency (fRF – fLO ) commonly known as Intermediate frequency (IF). The signal at this intermediate frequency contains the same modulation as the original carrier. This signal is a mplified by one or more IF Amplifier stages and most of the receiver gain is obtained in these IF Stages. The highly amplified IF Signal is applied to detector circuits to recover the original modulating information. Finally, the output of detector circuit is fed into audio and power amplifier which provides a sufficient gain to operate a speaker. Other important circuits in the Super heterodyne receiver are AGC and AFC Circuit. AGC (Automatic Gain Controller) is used to maintain a constant output voltage l evel over a wide band range of RF input signal levels. AFC Circuit generates AFC Signals which is used to adjust and stabilize the frequency of the local oscillator. The performance of the Super Heterodyne Receiver can be measured in terms of Selectivity, Sensitivity, Fidelity, Image frequency and its Rejection and Double Spotting . ELEN422 4 REFERENCES Algarin, J. M., Ramaswamy, B., Weinberg, I. N., Chen, Y. J., Krivorotov, I. N., Katine, J. A., ... & Waks, E. (2019). Frequency conversion of microwave signal without direct bias current using nanoscale magnetic tunnel junctions. Scientific reports , 9(1), 1 -7.