Question on quarter wave circuit?

In summary: The current in a resonant circuit is limited by the Q of the circuit, which is the ratio of the reactance to the resistance. In a series resonant circuit, the voltage and current at the source will be in phase.
  • #1
BHY-BK
18
1
Hi all, first post here.

I am studying 1/4 wave circuits and I've been wondering.

Can you have a LC circuit in which the reactances of the L and C produce resonance, while at the same time having the circuit be a 1/4 wavelength?

If so what would this circuits characteristics be?
 
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  • #2
BHY-BK said:
Hi all, first post here.

I am studying 1/4 wave circuits and I've been wondering.

Can you have a LC circuit in which the reactances of the L and C produce resonance, while at the same time having the circuit be a 1/4 wavelength?

If so what would this circuits characteristics be?
Welcome to the PF.

Can you post the Relevant Equations? Please show what you have been studying, and show the part that you are wondering about... :smile:
 
  • #3
OK,

You have a series LC circuit. The L value is 500uH while the C value is 10pF. So the resonant frequency is 2.25MHz. Now, let's say the electrical length of the inductor is exactly 1/4 wavelength at 2.25MHz. How would this circuit behave when driven at it's resonant frequency (2.25MHz) by an AC source?
 
  • #4
BHY-BK said:
OK,
I presume that the inductor is actually a piece of shorted transmission line having a length of 1/4 wavelength at 2.25 MHz. In such case it will behave as an open circuit and cannot look like 500uH.
If, however, the length of wire in the inductor is about 1/4 wavelength and the inductor looks like a shorted line 1/8 wavelength long, then it will have an inductive reactance numerically equal to its characteristic impedance. In this case the circuit appears the same as the LC series series circuit over a fairly wide range of frequencies centred on the resonant frequency.
500uH has a reactance of 707 ohms at 2.25 MHz, so the line would require a Z0 of 707 ohms.
If the circuit is driven by a low resistance generator in series with it, high voltages will appear across L and C.
 
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  • #5
Tech99

Thanks for the explanation, It is appreciated.

What about the current? How would you determine current flow in this circuit?
 
  • #6
What about the current? How would you determine current flow in this circuit?
A series resonant circuit has a resistance near zero, so the current will be mainly decided by the generator.
 
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FAQ: Question on quarter wave circuit?

What is a quarter wave circuit?

A quarter wave circuit is a type of electronic circuit that uses a quarter wavelength of a signal to achieve a desired effect, such as impedance matching or signal filtering. It is commonly used in radio frequency and microwave applications.

How does a quarter wave circuit work?

A quarter wave circuit works by utilizing the properties of a quarter wavelength, which is equal to one-fourth of the wavelength of a signal. This allows for constructive or destructive interference of the signal, which can be used to manipulate the signal in various ways.

What are the advantages of using a quarter wave circuit?

One advantage of using a quarter wave circuit is that it allows for precise tuning of signals, as the length of the circuit can be adjusted to match the desired wavelength. It is also a simple and inexpensive circuit to design and implement.

What are some common applications of quarter wave circuits?

Quarter wave circuits are commonly used in radio frequency and microwave applications, such as antennas, filters, and impedance matching networks. They can also be used in other electronic devices, such as televisions and cell phones.

Are there any limitations or drawbacks to using quarter wave circuits?

One limitation of quarter wave circuits is that they are only effective for a narrow range of frequencies. They also require precise calculations and measurements to achieve the desired results. Additionally, they may be affected by environmental factors, such as temperature and humidity, which can alter the wavelength of the signal.

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