Inverting a modulated signal (OOK).

[imrankhanPNU]

Hello,
I'm modulating the message signal with OOK (on-off keying) modulation. Multisim software is used to model the schematic [attached]. At the resistor R1, the modulated signal is obtained. I wanted to invert the modulated single, for that I used a simple NOT gate (U3), however at the NOT's gate output, I got the same signal as input means without inverting [attached]. So my question is, why isn't the NOT gate inverting? Am I doing something wrong?

As hit and trail, I added two more NOT gates (U4 and U5) but this time I got an inverted signal, although further improvement is needed to achieve a 180-degree phase shift. So my second question is: Why is it an inverter this time? and how to get exactly a 180-degree phase shift between two signals?

Thanks for your time.

 

[FvM]

Consider gate propagation delay.

Suggest to make a setup with a more reasonable operating frequency.

 

[imrankhanPNU]

Consider gate propagation delay.

Suggest to make a setup with a more reasonable operating frequencyFrom previous

Thanks, @FvM for your response. Due to the signal delay of the inverter, a shift is observed in the output signal, which is not applicable in my application.
Moreover, I am keen to achieve, an oscillating frequency of 100Mhz for a 1Mhz input signal. For that, i tried another schematic [attached]. however I could not get the desired result although everything seems correct to me, I do not know where I am making mistake? could you please review it? Thanks.

Fc=Oscillating freq, R=resistor, and C= capacitor
Fc=1/2.2RC

https://www.allaboutcircuits.com/technical-articles/how-to-design-schmitt-trigger-oscillators/

 

[betwixt]

The reactance of a 1nF capacitor at 100MHz is 1.592 Ohms and the series resistor is 4.55 Ohms so even if the 4093 could switch enough, you would be trying to draw I=V/R 5/6.146 = 814mA from its output. That is rather more than it is rated to deliver!

You need faster logic gates, a much smaller capacitor and higher feedback resistor value.

Brian.