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WHITE PAPER PREVIEW Design of a Complete RF Downconverter Module for Test Equipment RF/microwave modules such as the 3D layout of a finished downconverter circuit shown in Figure 1, often referred to as "hybrids," integrate functional blocks used to transmit and/or receive radio signals. These hybrid circuits combine different technologies, including monolithic microwave integrated circuits (MMICs)/RFICs, discrete field-effect transistors (FETs), and passive devices attached to substrates such as alumina or FR4, which contain circuit traces and distributed components, all within a single housing or enclosure. Figure 1: 3D layout of the finished downconverter circuit. By integrating diverse technologies, RF modules address the challenge of developing cost-effective radio circuitry for low- to medium-volume production, commonly used in test and measurement equipment and aerospace/defense applications. RF design is complicated by the sensitivity of radio circuits and the electrical behavior of components and layouts at higher frequencies. In addition to the electrical design, engineers must consider the manufacturing process to ensure that the RF performance is not adversely affected. Radio circuits are also subject to limits on radiated emissions, requiring conformance testing and certification by standardization organizations. For these reasons, a pre-made "drop-in" radio module that adheres to a specified footprint and input/output (I/O) connector config- uration helps save the system/subsystem designer devel- opment time and money. This white paper describes the design and simulation of a complete downconverter module for use in spectrum analyzer test equipment. The example module and its constituent parts were designed and simulated with AWR Design Environment software demonstrating a top-down/ bottom-up approach using circuit- and system-level analyses. The integration of the downconverter within a mechanical outline influences the layout of the individual radio blocks. Electromagnetic (EM) simulation of the module housing along with these blocks is necessary to produce a comprehensive analysis of the manufactured module. Module Specification A downconverter module consists of all the components in a receiver that process an incoming RF signal before conversion to a lower intermediate-frequency (IF) range for further processing. Performance parameters include input/ output frequency range, conversion gain, noise figure (NF), input/output power, return loss, spurious tones, power consumption, number of channels, and operating temperature. In addition to these electrical requirements, the spectrum analyzer test equipment application requires a specific mechanical footprint and I/O connector positioning. The following example illustrates the high-level design and system analysis of the downcon- verter module within a spectrum analyzer front-end. Part of the RF front-end of the receiver is shown in Figure 2, with the downconverter module circled in red. Figure 2: Spectrum analyzer front-end schematic showing downconverter receiver (in red circle). 11 www.cadence.com/go/awr