5G RF filters need more innovation 

 Rf filters have always been an important part of mobile devices, and in the 5G era, they are the key to unlocking the high bandwidth that will drive many 5G use cases. Top 4G/LTE mobile devices contain 50 to 90 RF filters to support use in countries around the world. These filters allow the desired RF signal to pass through while blocking adjacent signals that might interfere with that signal. Each antenna and frequency band supported by the device requires a new filter. Therefore, increasing 5G frequencies and supporting antenna diversity will drive the increase of filters in the next generation of mobile devices, cars, and other wirelessly connected systems. 

 The 4G transition requires new RF filter resonator structures - thin film bulk acoustic resonators (FBAR) and bulk acoustic resonators (SMR-BAW) - because the original adaptation frequency needs to be at least about 2 GHz, and the bandwidth needs to be 70MHz, because these networks operate in higher frequency bands. A new underlying resonator structure is needed to drive the performance of the RF filter. 5G, too, will require significant performance improvements in terms of network capacity, mobile connectivity, latency, cost, data rate and coverage. 

 Acoustic filtration technique Acoustic filters have become the most popular filter technology in mobile devices because of their small size and high performance. They use the piezoelectric effect to convert RF signals into electricity. Fine-tune the substrate to produce specific and small fluctuations. These fluctuations determine the frequency that the filter will handle. The filter can select a specified signal from a specific frequency band, while blocking signals that will cause interference. Key acoustic wave filter technologies include surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters, whose sound energy propagates on or inside the piezoelectric body, respectively. The growth in the number of filters used in mobile devices and the increasing demands placed on filters by increasingly crowded airwaves make RF filtering a key pain point for RF front-end (RFFE). Although specific 5G requirements for filters are now being developed, a basic overview of these requirements is shown, and the differences from previous wireless offerings are already clear. Path loss minimization The filter in the RF signal chain is responsible for the loss, which has a critical impact on the total emission efficiency and current consumption of PA and battery life. Figure 2 shows where losses occur in the RFFE, a module that includes power amplifiers, RF filters, antenna switches, low noise amplifiers (Lnas), and other circuits. The Tx/Rx filter is the largest loss, affecting the power consumption and total noise figure in the TxRx path, which ultimately reflects the signal-to-noise ratio (SNR) and data rate. The 5G band has a much wider bandwidth (up to 400 MHz instead of 20 MHz) and operates at a much higher frequency than 4G's 3 GHz. Therefore, 5G devices need to use different acoustic filters to minimize losses across the bandwidth, especially at the edge of the band. Some other important features of 5G filters include: Power handling: 5G is optimized for high-speed data/HD video. Due to millimeter wave operation, 5G requires much higher power than 4G to maintain coverage. In fact, 3GPP has created a new class of High Power User Equipment (HPUE) that operates at a frequency of +26 dBm on a single antenna. Therefore, the power durability of the gradually decreasing filter becomes the main problem. Interference: In the early days of using 5G bands, traffic is small, so there are few potential interference issues. Therefore, the requirements for filters are relaxed. However, as more traffic flows to 5G networks, higher filters will have to be used to address the interference that causes the user experience to decline. In addition to loss, suppression, and power, the increasing complexity of RFFE, especially filtering requirements, is driving other constraints. Complex multiplexing: Carrier aggregation (CA) provides multiple individual bandwidths to the smartphone, which must be multiplexed together into one aggregated data feed to increase the total bandwidth. Each of these data streams requires a filter and a reuse capability. In 4G, there are about 50 possible combinations, and according to Qualcomm's analysis, those combinations are expected to soar to more than 1,000 for early 5G devices. This will greatly increase the specifications and complexity of 5G filters. Optimized amplifier interface: While all filters support the standard 50Ω interface, in some cases it is not optimized for the signal path of a power amplifier (PA) or low noise amplifier (LNA). This affects power consumption. Understanding interface challenges during the design process ensures that the filter is path-optimized, which improves performance and helps reduce power consumption. Another important consideration is the growing collection of RF filter chips, which must be small and inexpensive so that they can be housed in phones without compromising size. conclusion 5G RFFE for mobile broadband will be complex and highly integrated. Acoustic filters are critical to managing this complexity. The goal of filter design is to simplify the design: to use the most appropriate components for the application and to optimize the interfaces within the RFFE module. RF filter designs that minimize and reduce component complexity will be critical, and both the tools and IP to enable this innovation will be critical to simplifying the RFFE.