Radiolocator Design: Power Measurement and Digital Data Path
In this chapter, we continue to follow the radiolocation signal through the data-collection stages: to power measurement and digitization of the power level, then onto gathering, formatting, and communication of radiolocation data to the supporting systems.
We are now at the stage where the signal has been downconverted to baseband frequency, and filtered to the desired radio channel. Provided that the received signal belongs to a valid wireless packet, a topic which we will take up in Chap. 6, we can be sure that we are detecting the transmission from one networking source, and one source only, and that radiolocation on the basis of this signal will give meaningful results.
Our power-measurement stage has, in its general design, a fairly typical real-time data-collection architecture: a sensor, in this case an integrated circuit measuring the average power of an AC signal, produces an analog reading of the sensory input after a fixed, known measurement time. The reading is digitized, also in real time, and raw data are grouped into meaningful units, in this case, readings of the same packet from all antennas, and sent off for higher-level processing. This higher-level step is the calculation of the packet’s direction of arrival (bearing); we discussed the algorithm in Chap. 2, and we will return to this algorithm’s timing aspects in Chap. 6.
KeywordsPower Measurement Automatic Gain Control Sampling Clock Crest Factor Sampling Capacitor
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