Issue link: https://resources.mouser.com/i/1541351
| 6 ambient or focused RF energy generated or reflected throughout an environment. These signals then stimulate transducers that are strategically located to capture the desired RF radiation. In some cases, arrays of transducers and signal- processing technology are used to create high-resolution images of incoming radiation or otherwise modify the transducer dynamics to enhance sensor directivity. Examples include radio telescopes that capture RF radiation from distant stars and celestial objects for astronomical observation and astrophysics research. Active RF sensing uses generated RF radiation with specific signatures that are directed using probes, antennas, waveguides, or other RF transducers toward target objects. The reflected or penetrating signals from the RF radiation circuitry are then captured by either the same transducers sending the generated signals or dedicated receiving transducers. These captured signals are then analyzed to determine the characteristics of the materials, medium, or interface through which the signals passed or were reflected. With appropriate circuit design targeting specific RF signal parameters, a variety of material and interface properties can be extracted from analysis of the signals. Examples of active RF sensing technologies include radar, weather radar, RF atmospheric measurements, non- invasive medical analysis, and grain silo food quality analysis. These also encompass material characterization techniques such as microwave free-space characterization and split-post dielectric resonator measurements. Radar is a very prevalent use of RF sensing techniques to determine the distance, velocity, shape, and structure of stationary and mobile objects, including environmental obstacles and terrain. With radar, a continuous, ramped, or pulsed RF signal is produced by the radar transmitter and directed to an RF transducer (antenna, aperture, or antenna array) that sends directed wavefronts (Figure 2). The resulting reflections from environmental features and targets are then captured and Figure 2: A legacy radar system with separate transmit and receive antennas. (Source: Koapan/stock.adobe.com)