What Is a Wave Filter PCB?

Using the piezoelectric substrate’s acoustic resonance capabilities, these filters offer high selectivity. This allows undesirable frequencies that are near the intended signal’s frequency range to be attenuated while the desired signal is magnified.

Printed RF components all use wave propagation on transmission line sections to transmit or block signals within specified bandwidths. These devices make it easy to create filtering action for a signal chain when certain off-the-shelf modules are not available.

Acoustic Waves

Sound waves are vibrations that travel in a medium, such as air. They disturb the particles in the medium and cause them to move. This movement causes other particles in the Wave filter PCB medium to vibrate, and so on. This creates a wave pattern that can be seen, for example, the rolling peaks and valleys of a sine (aka sinusoid) wave. These waves carry energy and can travel very long distances, but they lose intensity as they move farther away from the source.

The amplitude of a wave tells how loud the sound is. It can be measured in decibels, with higher amplitudes producing louder sounds. The frequency of a wave tells how often the sound oscillates per second. It is usually expressed in Hertz (Hz), which is equal to one cycle per second.

Ladder bulk acoustic wave filters are characterized by an unbalanced operation mode, with very small size able to deliver high selectivity filtering responses. However, they typically present low rejection or isolation out of band. Lattice bulk acoustic wave filters are more balanced, with slower roll off coefficient and high rejection. They are not a good choice for blocking signals close to the passband but are more effective at rejecting undesired bands [4].

Transducers

Transducers are devices used to convert energy in various forms into electrical signals. They can change chemical, mechanical, light, thermal, acoustic, and electromagnetic energy into signals. This is why they are often used in electronics and electrical projects. They can also work in both directions, converting electrical signals into physical action and vice versa. For example, a microphone converts sound waves into electrical signals, while a radio receiver converts electromagnetic transmissions into electrical signals.

These devices are classified into three types based on their operation principle and end-use. The first classification is based on the physical quantity converted. The second classification is based on the source of energy that drives them. Finally, the third classification is based on their mechanical structure.

The dynamic characteristics of a transducer verify its performance and specify how efficiently it can recognize preferred input signals and refuse unwanted ones. These characteristics are reliant on the transducer’s parameters and the nature of the input signal.

The dynamic properties of a transducer include linearity, repeatability, and efficiency. Linearity is the property by which a proportional change in output can be observed with a variation in input signal applied to it. Repeatability is the ability of a transducer to produce the same output repeatedly under identical environmental conditions. Efficiency is the capacity of a transducer to transform energy into a desired form of output.

Frequency Response

The frequency response of a filter PCB is determined by the design and layout of its Wave Filter PCB Supplier components. Using a PCB with an incorrect layout can cause unwanted resonances or even distortion in the signal. A good PCB will have a low insertion loss and selectivity and will be able to transmit desired frequencies while attenuating undesired ones.

Lumped element filters can be built from components like resistors, inductors and capacitors, which all have different dynamics at different frequencies. Inductors increase in impedance at higher frequencies, while capacitors decrease in impedance at lower frequencies. The overall effect of these dynamic changes can affect the RF signal in a number of ways, and can be detrimental to the performance of the filter.

For example, a current metal-based dichroic filter has a relatively narrow bandwidth (20 GHz) due to the fabrication limit in minimizing the circular hole spacing with thick metal plates. However, by utilizing a commercial PCB fabrication process with flexible adjustment of the circular hole spacing, a much wider bandwidth can be achieved. Furthermore, the skirt property of the filter can also be improved by varying the thickness of the filter substrate.

This paper proposes a new high-performing PCB dichroic filter for the KSTAR electron cyclotron emission imaging system. The filter is designed and optimized with theoretical calculation, verified with EM simulation, and experimentally measured. The simulated and measured results demonstrate that the proposed PCB dichroic filter has significantly larger FBW and steeper skirt properties than its counterparts in microstrip or pure acoustic filters.

Selectivity

A wave filter PCB is a device that selects specific frequencies and rejects others. In low-frequency applications, capacitors and inductors are arranged in resonant circuits to achieve selectivity. At SHF, these discrete elements cannot be used effectively; instead, distributed components, such as wave guide and strip line structures, must be employed.

The KSTAR ECEI imaging system utilizes a high-performing W- and F-band dichroic filter that has been fabricated with a commercial PCB process. The dichroic filter is a six-mm thick metal plate with a triangular lattice array of circular holes. The circular hole spacing should be minimized to increase the operating bandwidth of the filter. However, this can be difficult because of the fabrication tolerance of PCB materials.

In analytical chemistry, selectivity is the ability of an analytical method to distinguish between one substance and another. It is also referred to as sensitivity, which refers to how low a concentration can be detected. It is important for QC laboratories to establish selectivity because it ensures that only the analyte is detected, and no cross-reactions with other substances are observed.

Selectivity can be determined by using the ratio of the rate constants for competing reactions, or by measuring the logarithms of these ratios. This parameter is usually calculated from multi-component adsorption equilibria, but it can also be determined from single-component adsorption equilibria. Other terms for selectivity include isoselectivity, partial rate factor, and regioselectivity.