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I am attempting to simulate the following circuit. The MOSFET does not completely go off and the sin wave still leaks through the circuit even in the off state. Moreover, the output signal's amplitude is severely attenuated when the transistor is in the on state.

enter image description here

This phenomenon can be observed in the provided figure. I have attempted to use multiple MOSFETs however the results are similar. My input signal is 915MHz and is the net V(n011) in the figure. Please suggest a suitable MOSFET that would work for this particular frequency.

enter image description here

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My input signal is 915MHz

With a 915 MHz signal, the parasitic drain source capacitance of the MOSFET needs to be extremely small to achieve what you want. For instance 1 pF will present an impedance of 174 Ω even when the MOSFET is supposedly off.

The RK7002 is totally unsuitable as it has an output capacitance of typically 10 pF.

This is why we use 50 Ω as an impedance for transferring signals because otherwise, the parasitic capacitance problem would be beyond solvable.

Please suggest a suitable MOSFET that would work for this particular frequency.

Requests for products are off-topic on this site.

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  • \$\begingroup\$ So I should look for a capacitor that has a drain-source impedance of 50 Ohm at 915MHz? If I don't find the exact 50Ohm one, would there be a way to match the impedance some how? \$\endgroup\$ May 31, 2023 at 10:06
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    \$\begingroup\$ Not quite. There is an inherent problem in what you are trying to do using a MOSFET because they have (normally) such high drain source capacitance. It's normally solved at high frequencies using two switching devices; one replaces the resistor @PessentrauOptiarou <-- in fact you might need to use PIN diodes. \$\endgroup\$
    – Andy aka
    May 31, 2023 at 10:25

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