# Application Gallery

The Application Gallery features COMSOL Multiphysics® tutorial and demo app files pertinent to the electrical, structural, acoustics, fluid, heat, and chemical disciplines. You can use these examples as a starting point for your own simulation work by downloading the tutorial model or demo app file and its accompanying instructions.

Search for tutorials and apps relevant to your area of expertise via the Quick Search feature. To download the MPH-files, log in or create a COMSOL Access account that is associated with a valid COMSOL license. Note that many of the examples featured here can also be accessed via the Application Libraries that are built into the COMSOL Multiphysics® software and available from the File menu.

### Dipole Antenna with a Quarter-Wave Coaxial Balun

An antenna balun blocks undesirable currents on the outside of a cable. A quarter-wave coaxial balun (1:1) is one of the easiest designs: it works as a transformer and makes the input impedance from the inner conductor to the outer conductor infinite. This model simulates an antenna prototype including a SMA Receptacle, an ABS enclosure and a quarter-wave coaxial balun. The frequency is tuned to ...

### Defining a Mapped Dielectric Distribution of a Material (RF)

This example demonstrates how to set up a spatially varying dielectric distribution. Here, a convex lens shape is defined via a known deformation of a rectangular domain. The dielectric distribution is defined on the undeformed, original rectangular domain and is mapped onto the deformed shape of the lens. Although the lens shape defined here is convex, the dielectric distribution causes the ...

### Sierpinski Fractal Monopole Antenna

A fractal is a mathematical form showing self-repeating patterns. By virtue of its geometrical properties, a fractal structure can generate multiple resonances in RF applications. This antenna model uses a 3rd order Sierpinski triangle and the calculated S-parameters shows good input matching at the higher order resonances.

### Parabolic Reflector Antenna

A large reflector can be modeled easily with the 2D axisymmetric formulation. In this model, the radius of the reflector is greater than 20 wavelengths and the reflector is illuminated by an axial feed circular horn antenna. The simulated far-field shows a high-gain sharp beam pattern

### Branch-Line Coupler

A Branch Line Coupler (Quadrature 90° Hybrid) is a four-port network device with a 90° phase difference between two coupled ports. The device can be used for a single antenna Transmitter/Receiver system or an I/Q signal splitter/combiner. The objective of this model is to compute the S-parameters and to observe the matching, isolation, and coupling around the operating frequency.

### Log-Periodic Antenna

The shape of a log-periodic antenna resembles that of a Yagi-Uda antenna, but is composed of a coplanar array to achieve a wider bandwidth. It is also known as a wideband or frequency-independent antenna. All metallic parts are modeled using the perfect electric conductor (PEC) boundary conditions. The antenna is excited by a lumped port while a lumped element with a resistor is used to ...

### Time-Domain Modeling of Dispersive Drude-Lorentz Media (RF)

This tutorial shows how to solve the full time-dependent wave equation in dispersive media such as plasmas and semiconductors. The 2D TM in-plane wave model solves for the vector potential from the wave equation and for an auxiliary electric polarization density from an ordinary differential equation. The geometry consists of a single dispersive slab with a sub-wavelength slit in it. Periodic ...

### Dielectric Resonator Antenna

A dielectric resonator placed near a radiating element can be used to increase directivity and gain. Here, a block of quartz dielectric, with additional passive metallic antenna elements, is placed above a slot antenna. The fields in and around the antenna are solved for. The far field pattern and impedance is computed and improved performance is seen.

### Designing a Waveguide Diplexer for the 5G Mobile Network

A diplexer is a device that combines or splits signals into two different frequency bands, widely used in mobile communication systems. This model simulates splitting properties using a simplified 2D geometry. The computed S-parameters and electric fields at the lower and upper bands will show the diplexer characteristics in the Ka-band.

### Time-to-Frequency Fast Fourier Transform of a Coaxial Low-Pass Filter

A very wide band coaxial low-pass filter is designed using a 2D axisymmetric model. To address the wide band frequency response with a fine frequency resolution, the model is built with a transient physics interface first. Then, S-parameters are calculated using a time-to-frequency Fourier transform. To achieve a low-pass frequency response, an air-filled coaxial cable is tuned with five ...

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