Proportional frequency discriminator circuit

Commonly used phase frequency discriminators can be divided into mutual inductance coupling frequency discriminators and capacitive coupling frequency discriminators according to their coupling methods. Its improved mutual inductance coupling ratio
frequency discriminator circuit is shown in the figure. In the figure, the diode is 2AP9×2.
    The z-phase frequency discriminator is the same in the frequency modulation to amplitude modulation frequency modulation wave conversion part, but there are major changes in the detector part. The main differences are: 1) Separate the connection point O of the two detection capacitors C3 and C4 from the connection point D of the two resistors, and take
    the output voltage ‰ of the frequency discriminator from the two points D and E.     2) Connect a large capacitance G in parallel to the output terminals A and B. Its capacitance is about 10yF. Since the time constant the (R.+R2)C circuit is very large, it is about (o.1~o .2)s, so that during the detection process, for amplitude modulation changes above 15Hz, Udc on the capacitor G remains basically unchanged.     3) Among the two diodes, one diode is connected in the opposite direction to the phase frequency discriminator. In addition to ensuring the DC path of the two diodes , this also makes the output voltage polarity of the two detectors the same. Therefore, both ends of a are the sum of the output voltages of the two detectors.