I have a confusion about the impedance matching between the antenna and the RF-DC rectifier. The antenna(915MHz) was bought from the market and the datasheet says its impedance is 50ohm. However, I use a mini-Vector network analyzer to measure the impedance of the antenna, which is (42.4+22.5j)ohm. To reach maximum power transfer, the impedance of the source and the load should be the conjugate with each other (R+j=R-j).
My confusion is which impedance should I choose for matching (42.4+22.5j or 50ohm)?
Tuning the impedance matching is also difficult. First, I use ADS2017 to calculate the value of the L matching network. Then, I modify the capacitor and inductance around the calculated value. However, it hard to reach perfect matching. For example, the impedance of the antenna is 42.4+22.5j so I think the impedance of the rectifier should be tunned to 42.4-22.5j. If add a serial capacitor, the point should move counter-clockwise on the Z circular of the smith chart but in practice, the point just jumps to another position where it shouldn't be. Maybe it is because of the parasitic effect?
How do you usually matching the impedance according to the smith chart? Is there any mistake in my operation?
www.ebyte.com/en/pdf-down.aspx?id=362 antenna datasheet