Phase modulator in 41.650 MHz

The design of a phase modulator in 401.650 MHz, which was developed as an alternative for the transmitter modulator of a meteorological and hydrological data collection system by satellite is presented. This system collects and transmits environmental data to a reception center by data collection platforms, through a satellite. The modulated carrier has an angle deviation of +60 deg or -60 deg, corresponding to the digital data levels. The modulator consists basically of a phase locked loop (PLL) with a voltage controlled oscillator (VCO) in 401.650 MHz. The VCO frequency is divided by 64 and phase locked to a high stability reference. The modulation is made at 401.650 MHz with the modulation signal introduced after the phase comparator.