Constant envelope continuous phase frequency shift key modulation apparatus and method at radio frequencies
US5812604A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 16, 1996 |
| Grant date | Sep 22, 1998 |
| Priority date | — |
| Expiry date | Jul 16, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/2014
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
Constant envelope angle modulation apparatus comprises a frequency synthesizer for outputting a stepped output waveform having a selectable precise output frequency. The output of the synthesizer provides an input to a mixer for O-QPSK modulating a received information signal. The O-QPSK modulated signal is then hard-limited, for example, via a series of hard limiting amplifier and filter circuits and a divider circuit. Preferably, a data stream for modulation may be filtered via a filter having an approximately 70-100% roll-off characteristic, such as a root raised cosine filter. A hard-limited, constant envelope angle modulated signal results that is easily frequency converted to, for example, microwave frequencies for landline or satellite applications via a simple multiplier circuit. The multiplier circuit preferably comprises a series of stage-filtered multipliers and band pass filters to achieve the desired output microwave frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.