Content area
Full Text
RF engineers are primarily concerned with real signal power when sizing components and implementing controls for optimization of signal fidelity and/or data integrity. In communication links, RF signal power is carefully managed to maintain high performance and reliable connections over some distance. Transmitters carefully monitor signal power to maintain high levels of efficiency, and conformity to spectral regulations. Receivers monitor signal power to maintain optimal sensitivity and selectivity.
Most every power detector available on the market has been designed for broadband communications systems. However, it is the manufacturers of test equipment, developers of military and space technology, and advanced physics labs that have challenged companies such as Hittite Microwave Corp. to develop power detector technology best suited for measurement performance in terms of input sensitivity, dynamic range, repeatability, speed and accuracy over temperature. The HMC614LP4E RMS Power Detector with iPAR is die latest outcome ofthat work.
In general, power detectors sense an RF signal and produce an output signal that corresponds to that level of signal energy. A subsequent processor takes that detector output and correlates it to real signal power. Log detectors and RMS detectors have largely replaced diode detectors for large dynamic range applications, but each type has characteristics diat lend themselves better to some applications dian others. Table 1 provides a comparison between power detector types (key advantages of each detector type are indicated in bold).
LOG DETECTORS
Log detectors work well for systems in which the RF signal is pulsed (such as TDMA systems) and/or when the signal's peak-to-average power ratio (PAR) remains relatively constant. The output of a log detector correlates well with real signal power; however, that correlation varies as waveshape and PAR vary. The latest generation of broadband communication systems employ complex modulation schemes and sophisticated...