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Simulation AD630 -ASK modulation

Question asked by a.murray88 on Oct 23, 2013
Latest reply on Oct 23, 2013 by TimW

I am designing a basic ASK modulation system based on the AD630. The carrier signal is a sine wave of 1 MHz, and the modulating signal is a square waveform based on Manchester coding (it has some information I have encrypted). I am using the spice model provided for AD630 by Analog Devices, and LTspice.

I am trying to do the first trials with the spice model and using the circuit  suggested in the AD630's datasheet (Figure 9b, AD630 configured as a
gain-of-two-balanced modulator), but the simulator understands that pins 11,  21, 51 and 52 of the spice model, corresponding to pins 2, 18, 7, and 12 of the chip have floating nodes. The circuit suggested in the datasheet  has this floating nodes, and if I connect them to ground them, I practically ground the modulation input too . Am I missing something? How can I simulate this simple balanced modulator? Thanks,