11.2: RF System as a Cascade of Modules

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Most RF and microwave engineers work at the circuit board level and begin system design using modules. Some companies develop some of their own proprietary modules, thus providing a competitive advantage, but still use many modules developed by others. Examples of commercially available modules are shown in Figure 11.3.1. Modules can range in complexity from the simple surface mount resistor of Figure 11.3.1(a) and the transformer of Figure 11.3.1(d), up to the mixer and synthesizer modules shown in Figure 11.3.1(b and c). Modules can have very good performance as it is cost effective to put considerable design effort into a module that can be used in many applications and thus design costs shared.

Modules comprising a receiver are shown in Figure 11.3.2. Beginning with the bandpass filter after the antenna, each module contributes noise and nonlinear distortion. The system design objectives are generally to maximize dynamic range, the region between the signal being sufficiently above the noise level to be detected but before nonlinear distortion introduces spurious signals that limit the detectability of signals. At the same time power consumption and time to market must be minimized.

11.2.1 A \(15\text{ GHz}\) Receiver Subsystem

An example of a microwave subsystem is the \(15\text{ GHz}\) receiver shown in Figure 11.3.3 with details of the frequency conversion section shown in Figure 11.3.4. This subsystem is itself a module used in a point-to-point microwave link. The amplifier, frequency multiplier, mixer, circulator, and waveguide adaptor modules are available as off-the-shelf components from companies that specialize in particular types of modules.