BAW filters direct the signal energy through the bulk of the substrate, while SAW filters direct the signal energy along the surface of the substrate. The two main types of AWFs-bulk acoustic wave (BAW) and surface acoustic wave (SAW) filters-convert electrical and acoustic signals using interdigital transducers. ![]() Practically, these factors result in acoustic filters that can be as much as an order of magnitude smaller than traditional electromagnetic filter types for similar performance. The advantage over other electromagnetic filter technologies is that acoustic wave phenomena are roughly five orders of magnitude smaller than electromagnetic filtering phenomena. In this way, AWFs allow for the conversion of high-frequency signals into acoustic wave signals that can then be conditioned by acoustic resonator and filtering technology before being converted back into high-frequency signals. ![]() In essence, AWFs are constructed of electroacoustic transducers on piezoelectric substrates that can convert electrical energy into acoustic/mechanical energy and vice versa. To meet this need, engineers often use acoustic wave filters (AWFs). In many cases, distinct RF filters are needed for every frequency band to minimize crosstalk and mitigate nonlinear products. Given the extremely compact nature of modern wireless communication systems, there is a need for highly compact filters that still exhibit a high Q factor and can readily be integrated into filter banks for multi-band filtering applications. Many modern electronics also use accessory services that require their own filtering, such as the global positioning system (GPS) and other geolocation technologies as well as near-field communication (NFC) technology. Federal Communications Commission (FCC) and the global Electronic Communications Committee (ECC), as well as wireless standards such as Wi-Fi, 4G/5G, Bluetooth ®, and Zigbee. These can be standards set by national and international regulatory agencies, such as the U.S. What Applications Require an RF Filter?Īs the compact design of most modern communication technologies limits physical isolation, engineers use RF filters to enhance that isolation and ensure that these products meet the necessary standards. This article explores the basics of RF filtering and compares the two main types of acoustic wave filters-surface acoustic wave and bulk acoustic wave-for modern wireless communication applications. In many cases with modern electronics such as smartphones, these devices are equipped with several wireless communication technologies that could interfere with each other if not properly isolated using RF filters-a design challenge known as coexistence ( Figure 1).įigure 1: An example 5G smartphone diagram featuring a variety of wireless communication hardware with callouts to the various filter types needed. RF filters are also used to reduce harmonics, spurious content, and out-of-band leakage from transmitter circuits. In wireless communication systems, various RF filters are used at the input of receivers to attenuate signals outside the band of interest. RF filters are crucial, as there are many instances where undesirable signals (known as interference) can result in degradation or even damage to system functionality. ![]() Given the physical limitations of technology, RF filters are not ideal and do not reject signal content in rejection bands, which results in losses in passband frequencies. The primary function of an RF filter is to attenuate signals in certain undesired frequency bands while only minimally impacting signals in desired frequency bands. ![]() Radio frequency (RF) filters are cornerstone components in all RF/microwave systems, especially wireless communication systems with many channels or bands. SAW RF Filters The Difference Between Bulk Acoustic Wave (BAW) & Surface Acoustic Wave (SAW) RF Filters
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