Abstract: A securing interface apparatus to be inserted between a GNSS antenna and a first, unsecured, GNSS receiver fed by the antenna, for providing immunity against spoofing or jamming or interrupting of the timing provided by the first unsecured GNSS receiver.

Abstract: A securing interface apparatus to be inserted between a GNSS antenna and a first, unsecured, GNSS receiver fed by the antenna, for providing immunity against spoofing or jamming or interrupting of the timing provided by the first unsecured GNSS receiver.

Abstract: An atomic frequency standard system includes two atomic standard devices, a comparison circuit and a correction circuit. The first device operates continuously, while the second device is operated only periodically. As the second device is only periodically operated, it experiences little frequency drift due to aging effects. When operated, the second device is stabilized, and then frequency compared to the first device by means of the comparison circuit. The correction circuit is then used to recalibrate frequency of the first device with the stabilized frequency of the second device.

Abstract: A passive atomic frequency standard such as a Rubidium Frequency Standard or a Cesium Frequency Standard, using a microprocessor or equivalent circuit as part of its Frequency Locked Loop. The microprocessor phase modulates (pm) the RF signal which is introduced into the Atomic Resonator, and demodulates the output signal. The modulation and demodulation are performed by frequency hopping or spread spectrum techniques. Secondly, the microprocessor samples and integrates the error signal from the atomic resonator (Physics Package or Atomic Tube) with a sampled weighted- sum technique and thus better filters the noise, improves the Signal to Noise Ratio, rejects large noise like spikes, etc. Thirdly, the microprocessor saves the last control voltage of the Voltage Controlled Oscillator (VCO) to ease the start-up of the device as well as to keep the VCO at the last frequency in case the atomic resonator fails to function.