FM receivers using two-terminal negative admittance networks

A superheterodyne FM receiver comprising:

• first and second two-terminal negative admittance networks,
• a resonance structure in which a frequency modulated RF signal is induced, connected in series with the first negative admittance network,
• a first transistor connected to the point connecting the resonance structure and the first negative admittance network,
• a bypass capacitor connected to the output terminal of the first transistor for bypassing the RF signal,
• a second transistor connected to the first transistor in series therewith,
• a coil and the second negative admittance network connected in series with each other, the output of the second transistor being connected to the point connecting the coil and the second negative admittance network,
• a third transistor being connected to the said point connecting the coil and the second negative admittance network,
• the third transistor producing a frequency demodulated output signal at its output terminal, a resistor and capacitor connected in parallel with each other, one end of which is connected to the output terminal of the third transistor and the other to be connected to one of the polarities of a power supply, and
• a frequency feedback loop connecting the third transistor and the second transistor for feeding back the frequency demodulated output signal to the second transistor to control the frequency of the resonance structure.