The role of the intermediate frequency transformer mainly includes frequency selection and coupling.
Frequency selection: The intermediate frequency transformer has a fixed resonant circuit in the superheterodyne receiver. This resonant circuit can be fine-tuned within a certain range to ensure that the accurate resonant frequency can be achieved after the circuit is connected. The intermediate frequency transformer can achieve this function by changing the relative position of the fine-tuning capacitor or the magnetic core. In specific applications, such as the intermediate frequency amplifier circuit of the superheterodyne radio, the primary coil of the intermediate frequency transformer and the capacitors C1 and C2 form a 465kHz resonant circuit as the load of the transistors VT1 and VT2, so that only the 465kHz intermediate frequency signal is amplified, which plays a role in frequency selection.
Coupling: The intermediate frequency transformer not only has the function of frequency selection, but also plays the role of signal coupling. In the intermediate frequency amplifier circuit of the superheterodyne radio, the output signal of the first intermediate frequency amplifier is coupled to the second intermediate frequency amplifier through the intermediate frequency transformer, and the output signal of the second intermediate frequency amplifier is coupled to the detection stage through another intermediate frequency transformer, realizing the transmission and amplification of the signal.
In addition, the intermediate frequency transformer is also used in semiconductor radios as the main frequency selection component. By adjusting its magnetic core to change the inductance of the coil, the sensitivity, selectivity and passband of the intermediate frequency signal can be changed. This adjustment mechanism makes the intermediate frequency transformer play a key role in electronic equipment such as radios, optimizing the performance of the equipment.