What is an L-network?

A network consisting of an inductor and a capacitor.

This network matches a big range of impedances present in RF circuits. To accomplish this, inductor-capacitor circuit is used.

Please see the All About Circuits site for the article Understanding Matching Networks, and the article called L-Match Impedance Matching Circuits

Also, please see the Electronic Design site for the article Back to Basics: Impedance Matching (Part 2)

And, see the Analog Intgckts site for the article L-Matching. This site has the L-Matching Calculator.

For more information, please see the RF Wireless World site for the article Difference between L network Pi network T network antenna tuner type

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What is a pi-network?

A network consisting of one inductor and two capacitors or two inductors and one capacitor.

A capacitor is connected between the input and ground, another capacitor is connected between the output and ground, and an inductor is connected between input and output

From ki6ujh:

Think of the symbol "Pi" (π). It's the same shape, with two lines down to the ground.

For a Low Pass function, the two capacitors will lead the higher frequencies to ground while opposing that path to lower frequencies. The inductor leads the lower frequencies to the output while opposing that path to higher frequencies. Capacitors block DC

See Wikipedia's article Antenna tuner

Hint:

Pi-L, L for inductance. So, its a Pi with an inductor.

Hint: It's the only answer that has "Pi" in it, which comes from the loose suggestion it looks like the Greek letter pi (π).

See Wikipedia's article Π pad

Also, please see the EEEEGuide site for the article Symmetrical pi Network in Network Analysis:

And, see the RF Wireless World site for the article on Difference between L network Pi network T network antenna tuner type

Please, see the Robkalmeijer NL site for the article Pi and Pi-L design curves

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What is the resonant frequency in an electrical circuit?

The frequency at which capacitive reactance equals inductive reactance.

Generally, the resonant frequency occurs when there is a maximum oscillation, or as in electrical circuits it is the maximum value of the transfer frequency. In other words, it is the maximum output for any level of input.

In a resonant circuit, the inductive and capacitive reactance are equal and opposite, thus cancelling each other. This leaves the fundamental resistance of the circuit as the only impedance.

If either the inductance or capacitance is greater than the other resulting in non-resonance, the remaining uncancelled impedance adds to the overall impedance of the circuit. The key words here are "at resonance".

From Wikipedia's article on Resonance

"In physics, resonance is the tendency of a system to oscillate with greater amplitude at some frequencies than at others. Frequencies at which the response amplitude is a relative maximum are known as the system's resonant frequencies, or resonance frequencies. At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy.

Resonance occurs when a system is able to store and easily transfer energy between two or more different storage modes (such as kinetic energy and potential energy in the case of a pendulum). However, there are some losses from cycle to cycle, called damping. When damping is small, the resonant frequency is approximately equal to the natural frequency of the system, which is a frequency of unforced vibrations. Some systems have multiple, distinct, resonant frequencies."

See Wikipedia's article on Electrical resonance

Also, please see the Resources PCB Cadence C site for the article on What is Resonant Frequency?

And, see the Electronics Tutorials site for the article Series Resonance Circuit

For more information, please see the EEEGuide site for the article Symmetrical pi Network in Network Analysis:

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Which three network types are commonly used to match an amplifying device to a transmission line?

L network, pi network and pi-L network.

Please see the RF Wireless World site for the article on Difference between L network Pi network T network antenna tuner type

See the All About Circuits site for the article on Understanding Matching Networks

See Wikipedia's article on Impedance matching

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What is a pi-L network?

A network consisting of two inductors and two capacitors.

From jriechel:

One of the most common issues with transmitting into a multi-band antenna system is the creation of harmonic distortion that can cause cross interference with the outgoing signal.

Using some sort of filter network just prior to the last stage of the amplification process can suppress harmonics within that particular frequency transmission.

Of these many different Filter Networks the Pi-L (π) network is one of the most effective methods to suppress the harmonics in the final stage.

See Wikipedia's article Antenna tuner and the article on Π pad

Also, please see the EEEEGuide site for the article Symmetrical pi Network in Network Analysis:

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Which network provides the greatest harmonic suppression?

Pi-L network.

From jriechel:

In a resonant circuit, the inductive and capacitive reactance are equal and opposite, thus cancelling each other. This leaves the fundamental resistance of the circuit as the only impedance.

If either the inductance or capacitance is greater than the other resulting in non-resonance, the remaining uncancelled impedance adds to the overall impedance of the circuit. The key words here are "at resonance".

See Wikipedia's article Antenna tuner, and the article Π pad

Also, please see the EEEEGuide site for the article Symmetrical pi Network in Network Analysis:

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