Analysis of logarithmic amplifier-detector properties in its use in receiving paths of ADS-B system
Detectors having logarithmic transmission characteristic are rather widely used in the radio-transmitting devices of communication systems as a part of wave power control and regulation units and also in radio receiving equipment as radio signal envelope detectors. Logarithmic amplifier- detectors (LAD) have broad dynamic band (up to 80 dB) with bandpass range (unities and tens of GHz) of input radio signals and high conversion conductance. The article analyzes LAD properties characteristics in its application as a part of of receiving paths of Automatic Dependent Surveillance - Broadcast system (ADS-B) for signal envelope extraction of extended squitter. Analysis of the logarithmic detector’s operation is made, its mathematical model is developed, statistical characteristics of detector’s output signal are investigated. Analytic expressions for one-dimensional density of random probability of LUD output are obtained. Law revision of probability density affected by harmonic signal and Gaussian noise at detector’s input and with different signal-to-noise ratio is investigated. In order to evaluate performance of pulse detection system in which log detector is used the paper presents its detection performance calculation. This performance data enables to set necessary signal/noise power ratio at output of receiver’s high-frequency, to calculate its power parameters and to carry out the analysis of detection performance system.