Here is the circuit
I am a beginner so I'm not sure what exactly could be done to improve the circuit but let me go through what i understand about the circuit.
The circuit is comprised of the following
A resistive mixing network to algebraically add the carrier signal and the modulating signal (I dont fully understand why the resistors are required, can't we just connect them same node directly ? Also i dont see any difference upon removing the resistor R4 despite the references iread saying its need and that the mix signal appears across it, which i mean sure but why would that have any effect on the mixing of the two signals ?)
A diode which causes halfwave rectification, this makes the current running through the diode a series of pulses proportional to the amplitude of the modulating signal (I dont understand why its only proportional to the amplitude of the modulating signal and not to the carrier signal aswell)
Finally the LC tank tuned to resonate at the same frequency as the carrier signal 1.85MhzThat creates a negative half cycle for ever positive half cycle of our modulated signal as the pulses of of current cause the charging during the positive half cycle and discharging during negative
If there is any issue with my understanding of the circuit please let me know
Here is the output of my circuit compared to Ideal AM modulation
The output is definitely modulated, however i fear that the quality simply isn't good enough
My personal suspicions as to why this is the case based on my understanding are the following
The resistive mixer part of the circuits values were chosen arbitrarily through trial and error as i have no idea what exactly they should be, tunning these could improve the output.
The diode i am using could simply not have the correct characteristics + my input signal may be too high of a voltage and i am aware that this would cause no-linear behavior in the diode.
I miss understand the concept of the D.C offset required to offset your input signal such that through out its cycle is it positive.
Thank you in advance for the help