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This paper proposes a 2D notch generator algorithm based on frequency-invariant (FI)-shaped beampattern synthesis for the Global Navigation Satellite System (GNSS) space–time anti-jamming blind null-steering mode. Unlike conventional blind null-steering anti-jamming algorithms based on the power inversion (PI) algorithm, the developed method treats the blind null-steering spatial filter as a 2D spatial notch filter. The beampattern synthesis method is used to solve the value of the space–time filter. With the jamming direction as prior information, constraints are applied to the flat-top (FT) and nulling (NL) regions, and FI-shaped constraints are added to the FT region to establish the objective function. NL and FI enhancement coefficients are introduced to ensure the convergence speed of the objective function and the depth of nulling. The optimization method based on the alternating direction multiplier method is employed to solve the objective function. This synthesis method is applicable to arbitrary antenna arrays. The simulation shows that compared with the PI-based algorithms, the proposed algorithm ensures undistorted reception of GNSS signals, considerably improves the receiver's signal-to-jamming-noise ratio in different jamming scenes, enhances anti-jamming ability, and achieves an improvement of better than 20 dB in multiple three-jamming scenes. [ABSTRACT FROM AUTHOR]

Pulsar J0810+37 with a period of 1.2483 s is detected at a frequency of 111 MHz during the pulsar search at the Big Scanning Antenna (BSA) radio telescope of the Lebedev Physical Institute [1]. In this paper, we present the results of the detailed study of radio emission from J0810+37 which exhibits a rare nulling effect of different durations in a very wide time interval with an average nulling fraction in "switch-on" days 〈NF〉 = 38%; considering "switch-off" days, 〈NF〉 = 74%, since radio emission from this source is interrupted on average by 2–3 days, and then it again revives on average for 1–2 days. The "switch-off" periods reach 7 days. [ABSTRACT FROM AUTHOR]

In high-contrast imaging optical systems for direct observation of planets outside our solar system, adaptive optics with an accuracy of λ/10,000 root mean square is required to reduce the speckle noise down to 1 × 10 level in addition to the nulling coronagraph which eliminate the diffracted light. We developed the speckle area nulling (SAN) method as a new dark-hole control algorithm which is capable of controlling speckle electric field in a wide area quickly, despite an extension of speckle nulling, and is robust not relying upon an optical model. We conducted a validation experiment for the SAN method with a monochromatic light and succeeded in reducing the intensity of areal speckles by 4.4 × 10. [ABSTRACT FROM AUTHOR]

A nulling interferometer was proposed to achieve direct detection of extra-solar planets (exoplanets) by suppressing light from the central star using a pair of telescopes. Recently, the stellar coronagraph method has shown rapid progress, which uses an extended concept of the nulling interferometer within single telescope optics. A dynamic range larger than 1 × 10 9 for the detection of Earth-like exoplanets can be attained by reducing diffraction patterns using the nulling coronagraph, and by suppressing speckle noise using an adaptive optics with an accuracy of λ/10000 rms. An unbalanced nulling interferometer (UNI), which is used as fore-optics, improves the wavefront sensing sensitivity and compensation level of the adaptive optics by a factor of 10. Consequently, the dynamic range of the coronagraph can also be improved by two orders of magnitude. The UNI is composed of a modified coronagraph or a traditional interferometer and magnifies the aberrations of incoming wavefronts. [ABSTRACT FROM AUTHOR]

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About ∼ 200 radio pulsars have been observed to exhibit nulling episodes – short and long. We find that the nulling fraction of a pulsar does not have any obvious correlation with any of the intrinsic pulsar parameters. It also appears that the phenomenon of nulling may be preferentially experienced by pulsars with emission coming predominantly from the polar cap region, and also having extremely curved magnetic fields. [ABSTRACT FROM AUTHOR]