| 摘要 |
A microwave signal that varies linearly in frequency through a sweep period is radiated to and reflected back from a target body. In one mixer the directly generated signal is mixed with the reflected signal to produce a difference frequency corresponding to distance; another mixer mixes the directly generated signal with the same signal delayed for a constant time, to produce a reference difference frequency. Each difference frequency is digitized as a pulse train. The sweep period is divided into successive short time intervals, each of which can begin with a pulse of the lower frequency train and to each of which is assigned a numerical weighting factor, said factors for successive intervals differing stepwise in value. Pulses of each train occurring during each such interval are multiplied by the factor for the interval. All such multiplied pulses are counted through the sweep period to obtain a pair of pulse totals, and a quotient relationship between those totals gives an accurate measure of distance.
|
