A. M. Annenkov, V. N. Yudin

Modernization of Russian radio-channels and frame structures is required in order to meet the CCSDS and IRIG regulations. Bandwidth-efficient modulations give the solution for spectral compactness problem. Frequency shift keying (FSK) is the most popular method of signal transmission. Continuous phase frequency shift keying (CPFSK) is a variation of FSK. Continuous phase results in less spectral bandwidth occupancy. Minimum shift keying (MSK) was invented for binary data transition. Common MSK modulator scheme use voltage controlled oscillator (VCO) for binary data mapping and can be used for generating signals for coherent demodulation. Modulation index (m = 0,5 for MSK) of VCO-modulators is sensitive to time and temperature deviations. Digital modulation methods along with quadrature scheme provide more effective signal generation, i.e. high carrier frequency stability, deviation stability, noise stability, and functionality of universal digital radio transmitter. Spectrum of CPFSK meet the requirements of CCSDS (SFCG 21-2 from 413.0-B-1 recommendation) and IRIG 106-07 masks.