Electrically Variable Inductor

In summary: No, I'm not suggesting that. I'm suggesting that a varactor could be added in parallel with the radiator in order to vary the inductance.
  • #1
dnyberg2
125
2
I have an inductor in a design that is one half of an air coupled RF transformer. The operating frequency is 50 MHz. The purpose is to provide power to the load side. It is for all intents and purposes an RF to DC power supply design over some gap. The primary is the fed radiator inductor, a planar spiral PCB coil near 300nH. The secondary is the pickup and has a similar construction. The thing is, I need to be able to vary the inductance of the radiator inductor a little, plus and minus of the ~300nH in order to peak the match of the system. This post has a connection to my last post about detecting mismatch and changing the value of a varicap. Now I think I might need to vary the radiating inductor a bit but can't fathom a method to do so electrically. One theory is to insert ferrite core inductor in series with the radiating inductor and put a second winding on the tuning inductor and vary the u of that inductor by varying DC applied to the control winding like saturable reactor, thus varying the inductance of the tuning inductor that is in series with the radiator. Ideas?? Thanks!
 
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  • #2
At first glance without crunching the numbers my recommendation would be to incorporate a varactor. A circuit can still be inductive even though it has capacitance.
 
  • #3
dnyberg2 said:
I have an inductor in a design that is one half of an air coupled RF transformer. The operating frequency is 50 MHz. The purpose is to provide power to the load side. It is for all intents and purposes an RF to DC power supply design over some gap. The primary is the fed radiator inductor, a planar spiral PCB coil near 300nH. The secondary is the pickup and has a similar construction. The thing is, I need to be able to vary the inductance of the radiator inductor a little, plus and minus of the ~300nH in order to peak the match of the system. This post has a connection to my last post about detecting mismatch and changing the value of a varicap. Now I think I might need to vary the radiating inductor a bit but can't fathom a method to do so electrically. One theory is to insert ferrite core inductor in series with the radiating inductor and put a second winding on the tuning inductor and vary the u of that inductor by varying DC applied to the control winding like saturable reactor, thus varying the inductance of the tuning inductor that is in series with the radiator. Ideas?? Thanks!

I haven't read your other posts yet, so you may have addressed this already... How are you shielding this 50MHz power radiating apparatus to be sure not to cause interference with other RF devices?
 
  • #4
Right, the K or coupling coefficient between the radiator and the pick up is very close, in other words, the emissions is very low and there is a license in effect for the system.
 
  • #5
Averagesupernova said:
At first glance without crunching the numbers my recommendation would be to incorporate a varactor. A circuit can still be inductive even though it has capacitance.
In other words, you're suggesting to just shift the C around and that might be enough??
 

1. What is an electrically variable inductor?

An electrically variable inductor is a type of inductor that allows for the adjustment of its inductance value through an electrical signal. This is achieved through the use of a variable core material or a variable number of turns in the inductor's coil.

2. What are the applications of electrically variable inductors?

Electrically variable inductors are commonly used in electronic circuits for frequency tuning, filtering, and impedance matching. They are also used in variable inductance sensors and in power supplies for controlling the output voltage.

3. How does an electrically variable inductor work?

An electrically variable inductor works by changing the amount of magnetic flux passing through the inductor's core. This can be achieved through the use of a variable core material, such as a ferromagnetic material with adjustable permeability, or by varying the number of turns in the inductor's coil using a variable tap.

4. What are the advantages of using electrically variable inductors?

One of the main advantages of electrically variable inductors is their ability to be easily adjusted to a specific inductance value, making them more versatile than fixed inductors. They also have a smaller size and weight compared to other types of variable inductors, making them suitable for use in compact electronic devices.

5. Are there any limitations to using electrically variable inductors?

One limitation of electrically variable inductors is their lower quality factor (Q-factor) compared to fixed inductors, which can result in higher power losses. They also have a limited range of inductance values that can be achieved, making them less suitable for applications that require a wide range of inductances.

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