Hello!
I'm relatively new to LTSpice, I have a project to simulate in LTSpice. I appreciate any help you guys can afford. the project is a distance measure using ultrasound transducers. I have a timing generator which generates a square wave to start TX to send an ultrasound signal and a sawtooth signal wich feeds Sample and Hold circuit. When RX recieves an echo signal, it sends it to an amplifier wich enables Hold state. The voltage that is held is sent to VCO (using 555 timer) wich generates a proper signal according to Hold voltage, see attached block diagram and LTSpice file.
My headache is the transmitter TX which it generates a 40 kHz signal when it simulated only with the timing generator but when it is simulated with the whole circuit, it generates a 20 kHz! And i don't have a clue of why!
thanks in advance!