Frequency counting modulator
Abstract
A frequency-counting modulator (FCM) to produce constant-envelope signals for nonlinear-channel satellite or mobile digital transmissions is presented and evaluated analytically. The FCM output-signal frequency is set by the division of an oscillator frequency by a programmable counter controlled by a preset-value generator using oscillator-derived timing and modulation data. Signals for MSK and modified versions of MSK and BPSK with three instantaneous frequencies can be generated. The MSK design formulas are derived, and the minimum signal distances, the effect of a Gaussian receiving filter, and power spectra are analyzed; graphs and drawings illustrate the results. It is pointed out that the purely digital design of the FCM should facilitate an LSI implementation.
- Publication:
-
IEEE Transactions on Communications
- Pub Date:
- December 1983
- Bibcode:
- 1983ITCom..31.1280N
- Keywords:
-
- Counting Circuits;
- Digital Systems;
- Frequency Modulation;
- Frequency Shift Keying;
- Large Scale Integration;
- Network Synthesis;
- Channel Capacity;
- Design Analysis;
- Frequency Dividers;
- Performance Prediction;
- Power Spectra;
- Satellite Transmission;
- Transmission Efficiency;
- Communications and Radar