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13 | integrated into an RF signal chain help RF designers design around the given inputs and ensure they meet the output requirements. In some cases, this could be as easy as finding the right commercial-off- the-shelf component or as laborious as designing and manufacturing a device from the ground up. Key RF Building Blocks There are many different types of RF components and devices, and even more extensive variations of each type. These components are typically grouped into broad categories based on their primary function in the RF signal chain, including the following: • Frequency translation • Frequency and phase adjustments • Amplitude adjustments • Frequency selection • Switching • Signal directivity isolation • Multiplexing (time, frequency, phase, directivity) • Signal splitting/combining • Generation and synthesis • Signal detection, demodulation, or conversion to baseband (analog or digital) Some RF components and devices may serve multiple functions, especially if the components are integrated into a module and the RF signal chain is at a high level of abstraction. In some cases, the RF signal chain building blocks correspond to RF circuit elements, but they may also be more complex circuits that include several RF circuits. For instance, an RF filter could be as simple as a 2D structure on a planar circuit board or a multi-element circuit with several active components as a dedicated filter module. Figure 2 depicts a generic, hybrid digital/ analog phased array transceiver circuit, like a hybrid analog/digital radar circuit. It presents a middle level of abstraction, displaying the key RF building blocks without showing significant details, ancillary components, or interconnects. The diagram also shows two frequency- translation stages, including two intermediate frequency (IF) stages. This is generally done when the distance between the baseband frequency and radio frequency is great enough that a single frequency translation stage would result in unacceptable signal quality at the output, such as from spurious content or harmonics. Filters RF filters are essentially frequency- selective attenuators. The frequency content of signals that pass through RF filters experiences minimal attenuation in the passbands (i.e., insertion loss) and significant attenuation in the stop bands. The design and complexity of an RF filter can result in multiple passbands and several stop bands. Depending on the application, these complex filters are often realized as filter banks and may also be used as diplexers or multiplexers. Figure 2: A generic, hybrid digital/analog phased array transceiver signal chain. (Source: Mouser Electronics/Author)

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