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5G NR Primer for Amplifier and Filter Design

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Product Flow for 5G/LTE Envelope Tracking PAs Next-generation communication systems, made possible through innovative high-frequency electronics, will be responsible for a rich ecosystem of future wireless connectivity. The technologies being introduced to achieve anywhere, anytime instan- taneous data will rely on complex system architectures that will lead to design challenges at the component level. AWR Design Environment software is continually advancing to help RF/microwave engineers meet these challenges with system/ circuit/electromagnetic co-simulation and a streamlined path to test and measurement (T&M) equipment for design verifi- cation. This chapter examines the use of envelope tracking, digital pre-distortion, and impedance matching via load pull to improve the efficiency and linearity performance of RF power amplifiers targeting 4G and 5G applications. Carrier Aggregation With carrier aggregation (CA), operators can make better use of available fragmented spectrum allocations by combining component carriers (CCs) from a single intra-band CA or multiple intra-band CAs, allowing the combination of up to five separate carriers to enable bandwidths up to 100MHz, although current long-term evolution A (LTE-A) implementations target an aggregate bandwidth of 40MHz (two carriers with 20MHz bandwidth each) for the uplink and four CAs (80MHz) on the downlink. The earliest and most straightforward CA implementations, as defined by release 11 of the 3GPP LTE-A standard, call for aggre- gated contiguous CCs within the same frequency band (intra-band) for TD-LTE in the uplink. Inter-band CA configurations refer to the aggregation of component carriers in different operating bands, where the carriers aggregated in each band can be contiguous or non-contiguous, as shown in Figure 1. This can lead to CA combinations that cover a broad spectrum and is clearly a more challenging PA design problem. Figure 1: Contiguous and Non-Contiguous carrier bands Operation across two or more bands has historically required separate amplifiers and an assembly of low-pass filters (LPFs) and a multiplexer, as shown in Figure 2 (left). A single wideband amplifier and a low-loss switch could replace multiple ampli- fiers, offering a lower cost solution than multiple band-specific amplifiers and consuming less circuit board area as shown in Figure 2 (right). However, the configuration based on a wideband PA must offer higher power and efficiency to offset increased insertion loss of the switch. CA also requires higher power output to enable simultaneous transmission on multiple component carriers. In addition to high power and wideband requirements, PAs must offer sufficient linearity and power efficiency to reduce operating costs for the base station and extend operating time/reduce battery size and weight for the mobile device. Figure 2: Multi-band front-end configurations based on narrowband PA/filter chains (left) and wideband PA/switch filter bank (right) 5G NR Primer for Amplifier and Filter Design 2

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