Transmitter phase and amplitude correction for linear FM systems
US4968968A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 9, 1989 |
| Grant date | Nov 6, 1990 |
| Priority date | — |
| Expiry date | Nov 9, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B1/123
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A system is disclosed for measuring and correcting for waveform modulation errors in a radar system employing FM signals and a digitally controlled waveform generator. The system relies on the assumption that the transmitter and other waveform phase and amplitude error contributions are slowly varying with respect to the radar mode data collection time and that instantaneous pulse-by-pulse correction is not necessary. During a calibration mode, a small portion of the transmitter output is input into the receiver and mixed with the waveform generator signal, with the waveform modulation being removed from the mixer signal, such that the mixer signal is at a constant IF but with phase and amplitude variations that result from the distortions. The radar digital processor measures these distortions, and during normal radar operation predistorts the waveform generator signal with phase distortions in antiphase with the measured distortions to compensate for the measured distortions. Amplitude distortions are compensated by control of a variable attenuator device. As a result, the system compensates for the exciter and transmitter distortions as well as distortions introduced by the rece…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.