Your circuit is a bit incomplete in the sense that it only shows the inductor and capacitor in parallel. This circuit is often called an "LC tank" and it has an impedance that is frequency dependent.
There are two ways to determine an impedance:
- A: apply a voltage and measure the current
- B: apply a current and measure the voltage
simulate this circuit – Schematic created using CircuitLab
Now the "special" property of the LC circuit is that in some situation the energy travels back and forth between inductor and capacitor. That's called "resonance" and an important property of you want to use this as an antenna.
Can you spot the issue with circuit A? It is related to this resonance.
The issue is the following: suppose capacitor C1 has a certain charge (and therefore some energy) and since we want the circuit to resonate the energy has to go into the inductor. But can this happen? No it can't because the voltage source V1 dictates the voltage across C1 so even if C1 had a certain charge that would immediately be overruled by the voltage set by V1. So circuit A isn't useful.
Is circuit B better?
Yes it is, I2 is a current source so it will not enforce any voltage. But what about the current? Indeed I2 does force the current but that is the current through both L2 and C2. So C2 can still push out extra charge (current) into L2. This means the energy can be exchanged between L2 and C2 so we can have resonance.
So the input signal for your circuit is the current and the output signal will be the voltage that develops across the LC circuit as a result.
I'm not going into the analysis of that and it is not needed as it is all explained on the LC circuit article on Wikipedia
Also, if you want a voltage input but and current output that's also possible but then you have to use a series LC circuit.