Direct QAM modulator
US5852389A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 17, 1997 |
| Grant date | Dec 22, 1998 |
| Priority date | — |
| Expiry date | Apr 17, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03C3/22
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A direct QAM modulator for generating a high power QAM modulated signal at microwave frequencies comprises a hybrid to create the required RF signals for I and Q paths. In each path, a rat-race coupler is used to get the in phase and out of phase RF signal. The subsequent circuit blocks in each path consist of a single pole double throw switch (SPDT) switched by the polarity of the incoming data, a reflection attenuator, implemented by using forward biased pin diode terminations and controlled by the absolute values of the baseband pulse amplitude modulation (PAM) signal, and a variable reflection phase shifter to adjust for the phase error. To realize modulated signal filtering and to compensate for the nonlinearities, a combined prefiltering and predistortion block is used to shape the baseband PAM signal in each path. Finally, a power combiner is used to combine signals from the two paths into one high power QAM modulated and filtered output signal at microwave frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.