Need help regarding ADS; what is the input signal?

Hi All,

I am designing a 2 stage amplifier in ADS. I have used the term components at the input and output ports. DC supply of 6V is used with the RFC at the collector. Can somebody tell me as to what is input signal amplitude provided to the circuit so that I can provide the same input signal when i build the circuit.

How can we vary the amplitude of the input signal when performing the s parameter simulations?

During s-parameter simulations, the amplitude is not concerned by simulator engine because s-parameter simulations are done under small signal conditions.That's why, whatever you type in power or amplitude field in port component, ADS won't consider this information.

BigBoss is right. ADS isn't concerned with input power level for s-parameter simulation. When you actually build it and measure it tho, you need to apply an input power from the Network Analyzer that is low enough such that your amp is operating in the linear region, such that you measure the correct gain, without the amp being compressed. You can do this by seeing if S21 changes when you change the input power level. If it doesn't change when you go from say, -35 dBm to -40 dBm, then you're in the linear region with an input power of -35 dBm.

Thanks. I built the circuit and measured the gain at 0dB, but when I reduced the input signal -10, -15, -20dBm there was an increase in gain, Can you explain me why does it happen?

Because the circuit entry into saturation and gain drops down by higher input signals.S-parameter measurements should always be done under smal signal conditions so that circuit does not have exceeded linear output power ..
Simulation is another issue...

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