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 beam tube for frequency standard which employs either counter propagating optical beams or counter propagating atomic beams and Coherent Population Trapping (CPT) is disclosed. Atoms selected from the group consisting of the alkali metal family (Cesium, Rubidium, Potassium, Sodium and Lithium) are emitted from one or two sources to form a single or double atomic beams. The atoms interact with the optical beams at two crossing points. The optical beams are generated by a laser and are modulated at half the hyperfine frequency. The optical beam is splitted into two counter propagating beams in round paths which interact with the atomic beam at two interaction regions. The interaction with the light causes the atoms to enter a CPT state. A dark line in the fluorescence at the second crossing is used to lock an RF oscillator to the atomic hyperfine transition.

Abstract: This invention concerns the realization of a Coherent-Population-Trapping (CPT) atomic frequency standard by utilization of both the phase delay and the absorption of the light transmitted through an atomic vapor. The invented method enables the use of high modulation frequency and a fast lock of a low quality oscillator to the atomic hyperfine transition.

Abstract: This invention concerns the realization of a Coherent-Population-Trapping (CPT) atomic frequency standard using a laser which has feedback from an external cavity. The mode spacing of the external cavity is adjusted to equal the hyperfine transition frequency of the atomic vapor or a sub-harmonic of it. The external cavity enhances the modulation response at the required atomic transition and improves the stability of the frequency standard.

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.

Abstract: Improved atomic clocks and frequency standards of the type where the frequency of an oscillator is stabilized by locking via a phase lock loop to an atomic resonator and where the output of the clock is taken from this oscillator. Protective means are provided to maintain a high accuracy when such clock is exposed to a strong magnetic field. The stabilization is based on two magnetic "C"-fields which are controlled and adjusted to maintain the accuracy of the clock.