LTspice does not have a generator for amplitude modulation so here's a way to do that.
Below is a simulation of using a sine function to vary a resistance with time, along with an AC current-source, to generate an AM signal and a DSB suppressed-carrier modulated signal.
The function works to generate a simulated negative resistance for the DSB generation. This provides a carrier phase reversal for alternate half-cycles of the modulation signal, which is characteristic of a DSB modulated signal.
The modulation frequency is (2pi*time*X), where time is the simulation time and X is an arbitrary constant. Thus sin(2pi*time*1k) gives a sine modulation frequency of one cycle per ms or 1kHz.
The peak output voltage is equal to I1/1000, thus giving a peak value of 1V for the shown value of 1000A.
Note that the output impedance of the circuit varies with time (from 0 to 1mΩ in this example) but that should not cause a significant error in most circuits. If necessary, a high impedance buffer circuit can be added.
To generate just one function, eliminate the resistor for the other function and ground the current source.
Of course other arbitrary time functions can be used to generate outputs besides sine modulation or a sine carrier.
Below is a simulation of using a sine function to vary a resistance with time, along with an AC current-source, to generate an AM signal and a DSB suppressed-carrier modulated signal.
The function works to generate a simulated negative resistance for the DSB generation. This provides a carrier phase reversal for alternate half-cycles of the modulation signal, which is characteristic of a DSB modulated signal.
The modulation frequency is (2pi*time*X), where time is the simulation time and X is an arbitrary constant. Thus sin(2pi*time*1k) gives a sine modulation frequency of one cycle per ms or 1kHz.
The peak output voltage is equal to I1/1000, thus giving a peak value of 1V for the shown value of 1000A.
Note that the output impedance of the circuit varies with time (from 0 to 1mΩ in this example) but that should not cause a significant error in most circuits. If necessary, a high impedance buffer circuit can be added.
To generate just one function, eliminate the resistor for the other function and ground the current source.
Of course other arbitrary time functions can be used to generate outputs besides sine modulation or a sine carrier.