Types of Wave Filter PCB Components
Printed RF filters operate based on wave propagation in transmission line sections. They are often employed in electronic devices and medical equipment to reduce jitter and ensure precise readings.
These filters utilize a piezoelectric substrate to eliminate particular frequencies from signals by producing surface acoustic waves. They are compact and offer high selectivity.
SAW Filter
The SAW filter is an electronic circuit board component that takes in radio waves and only lets them pass through when they match the desired frequency. It does this with an electrode that’s supported by a piezoelectric substrate. The piezoelectric layer vibrates when the signal arrives, converting it into surface acoustic waves that can move through the filter. This makes it possible for the filter to magnify certain frequencies and attenuate others. Because of this high selectivity, these filters can be very useful in a variety of applications, including mobile phones, Wi-Fi and radar systems.
The key difference between BAW and SAW filters is that the former directs energy through a bulk of Wave filter PCB the substrate, while the latter does so along the surface. This distinction also impacts the device’s frequency capabilities. BAW filters are typically more complex to design and fabricate, while SAW devices offer lower insertion loss and higher selectivity.
Another notable feature of SAW filters is their ability to withstand temperature variations. They are often designed with a frequency shift that’s proportional to temperature. This characteristic makes them more suited for battery-powered devices that don’t need a large power supply. However, the frequency shift can cause problems when the temperature changes significantly, so SAW filters are also available in temperature-compensated forms. These are typically more expensive, but they provide better performance than standard SAW filters.
Microstrip Filter
Microstrip filters are a type of planar transmission line technology that consist of a conducting strip separated from a ground plane by a dielectric substrate. They are commonly used in printed circuit boards to filter out unwanted signals from the desired signal. These filters can be designed using a number of different topologies, including stub loaded, stepped impedance, and interdigital. The design of these filters requires careful attention to the precise dimensions of the filter elements.
A new enhanced design procedure for microstrip band pass filters has been developed. The procedure uses a length correction factor for the filter resonator that significantly reduces the error in the center frequency of the filters. The result is a much more accurate microwave filter that requires no tuning.
The design method is based on a Minkowski fractal iteration algorithm for the geometry of the comb-line cavity filter. This method allows for the fabrication of high-order microstrip filter resonators with a narrow bandwidth and high stopband selectivity. The technique also simplifies the fabrication process.
The performance of the filter has been tested after coating it with CV-1152 resin. This material appears as a viscous liquid before it is applied to the device, and then dried for one week. The measured frequency shift between the S -parameters of the filter without and with the coating is 130 MHz.
SAW Line Filter
SAW line filters are semiconductor devices that filter RF (radio frequency) and IF (intermediate frequency) signals. They use piezoelectric effects to transform input energy into vibrations that are transferred across the chip as waves and turned back into a desired frequency range of signals at the output IDT. They offer high performance and stability in temperature ranges, low insertion loss, and excellent stop-band attenuation.
When a signal travels through a SAW filter, it loses some of its energy due to the mechanical vibrations caused by the piezoelectric material used in these filters. This is known as insertion loss and can Wave Filter PCB Supplier affect the quality of a signal. SAW filters are designed to minimize insertion loss, so they can transmit the most possible energy from one end of the circuit to the other without losing any of its quality.
Typical SAW filters are made of quartz, lithium tantalate (LiTaO3), or lithium niobate (LiNbO3). They operate by converting radio frequency energy into acoustic or mechanical energy by the application of pressure to the piezoelectric substrate. These acoustic or mechanical vibrations are then converted into electrical pulses at the output IDT.
SAW technology has gained significant traction in the mobile telephony market and offers technical advantages in terms of size, cost, and performance compared to competing technologies such as LC filters and quartz crystals (based on bulk waves). However, SAW filters begin to show less selectivity beyond 3 GHz and thus have a limited usage in mobile applications. For this reason, a complementary technology is needed for higher frequencies.
Microwave Filter
Microwave filters are used to filter signals in radio communication and radar applications. They are available in several types, including waveguide, stripline/microstrip, dielectric resonator and cavity/coaxial topologies. Microwave filters are designed to meet the specific requirements of a given application, and can be customized with a wide range of specifications. They can be found in a variety of products, from high-performance broadband filters to low-cost bandpass and high-pass filters.
RF/microwave PCB design engineers often use materials with high dielectric constant values to minimize the dimensions of their filter circuits. The dielectric constant of a particular material is determined by its permittivity e’, which translates the material’s capacity to store electrons in an electric field. It is important that this value remain within the tolerance range cited for the material by its manufacturer, as small errors in the dielectric-constant calculation can lead to unwanted changes in a filter’s dimensions and center frequency/wavelength.
Whether it’s a simple RF filter or a large microwave filter, accurate CAD design is vital for successful results. A unified PCB design tool that includes digital, analog and mixed-signal capabilities can help designers stay productive and deliver quality RF designs faster than ever before. Altium Designer on Altium 365 provides a suite of automation tools to help engineers create accurate and reliable RF and microwave PCB designs for manufacturing.