Linearized offset QPSK modulation utilizing a sigma-delta based frequency modulator
US6975687B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 18, 2001 |
| Grant date | Dec 13, 2005 |
| Priority date | — |
| Expiry date | Dec 20, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03F2200/331
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A vector modulator including an offset QPSK modulator operative for receiving input data and generating a first output signal representing the modulation to be imposed on a carrier signal to effect offset QPSK modulation of the input signal and a second output signal representing an amplitude of the input data; and a frequency modulator including a sigma-delta modulator, operative for receiving the first output signal generated by the offset QPSK modulator, and generating a control signal representing the desired frequency of the carrier signal such that the carrier signal represents the input signal offset QPSK modulated. The vector modulator also includes a phase-lock loop circuit having a voltage controlled oscillator for generating the carrier signal and a programmable frequency divider for receiving the control signal as an input signal and for changing the frequency of the carrier signal in accordance with the control signal, and an amplifier having a variable gain which is operative for receiving and amplifying the carrier signal output by the phase-lock loop circuit in accordance with the amplitude of the second output signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.