MEASUREMENT OF LORAN-C ENVELOPE TO CYCLE DIFFERENCE IN THE FAR FIELD; TECHNICAL REPT. (FINAL)

With continent expansion and increased use of LORAN over extensive land paths by both aviation and terrestrial users, there has been renewed interest in the prediction and measurement of Envelope to Cycle Difference (ECD) in the far field. A number of relevant issues in measurement of ECD are discussed. These include modeling of the far field pulse, analysis and calibration of the receiver front end, the algorithm used for calculation of ECD and the statistics of the measurements as a function of the signal to noise ratio and the noise model. Via network analysis, the magnitude and phase of the frequency response of the receiver is measured and used to create a computer model of the front end. Calibration of the front end is accomplished by supplying an ideal LORAN pulse of varying ECD as the input to the model, measuring the output, and applying a conversion curve in the algorithm. Issues such as receiver bandwith, order, and the waveform samples used for ECD calculations are discussed. The statistics of the measurement process are examined in detail. Examples of bias due to cross rate interference and procedures for calculating the bias are presented.