The present invention relates to a process for the autonomous reduction of acquisition and tracking thresholds of carriers received in orbit by a receiver accessing an orbital navigator inside or outside said receiver, the latter having at least one phase loop. The phase loop, which is responsible for the acquisition and/or tracking of the carrier, is "pushed" by the fine speed aid and takes up the error between the real speed and the calculated speed. The search for the Doppler frequency of the carrier received takes place around a frequency prediction maintained by the fine speed aid coming from the orbital navigator.

An antenna tracking device comprising an antenna which is so controlled in direction as to receive a plurality of beacon signals at different frequencies transmitted from a plurality of stationary satellites, respectively, which are spaced apart from each other by a relatively small distance, error detector connected to the feed of the antenna for detecting error signals each representing the difference between the incoming direction of each beacon signal and the axial direction of the main beam of the antenna, reference signal generator responsive to each beacon signal delivered to a receiver for generating a reference signal, and a tracking receiver which receives the reference signals and the error signals to generate the tracking error signals each consisting of mutually orthogonal components. The antenna tracking device of the type described above further includes synthesizer means for combining the components in the same directions of the tracking error signals from the tracking receiver, thereby generating the antenna driving signals. In response to these driving signals, the antenna is directed to the midpoint or center of a plurality of stationary satellites.

A low phase noise third order phase lock loop which can track and eliminate microphonic disturbances and phase hits. The PLL utilizes a third order loop filter which incorporates two integrators. These two integrators, when coupled with the integration which occurs at the voltage control input of the voltage controlled oscillator within the PLL yield an open loop transfer function with a --18 dB/octave rolloff over a band of frequencies which at least encompasses the spectral content of the microphonic or phase hit phase noise disturbance to be eliminated. The open loop gain of the phase lock loop must be set high enough such that the phase lock loop does not oscillate and such that the loop converges and locks. The integrators are implemented with operational amplifiers with RC feedback networks. The values of the components in the RC feedback networks set the frequencies of two zeroes in the transfer function. The frequencies of these zeroes are set by proper selection of the R and C values to cause a change in slope of the open loop gain frequency response curve at the frequency of the zeroes from the -18 dB/octave rollof to a -6 dB/octave rolloff at the frequency of the zeroes. This causes the phase angle of the open loop PLL transfer function to be more positive than -180 degrees at the frequency at which the open loop gain magnitude frequency response curve falls to unity gain thereby achieving conditional stability. The open loop gain of the PLL is set such that the -18 dB/octave rolloff of the frequency response does not result in a gain of unity until a frequency is reached which is above the highest expected frequency deviation of the carrier caused by microphonic disturbances or phase hits. In the preferred embodiment, the gain is set high enough that the -18 dB/octave rolloff of the open loop gain frequency response extends over at least two decades and extends up to 10 kHz which encompasses substantially all the spectral content of the microphonic disturbance caused by package resonance which sources the phase noise to be eliminated.