LFM/PRBC Modulation Signal Parameter Estimation

Since pseudo-code phase modulation and carrier frequency modulation composite reconnaissance signals have both the good anti-interference capability and the low probability of interception, they have been widely used in electronic reconnaissance systems. This paper proposes a multi-parameter estimation method for pseudo-random binary phase code (PRBC) and linear frequency modulation (LFM) composite modulation signal in a complex electromagnetic environment. Firstly, this paper uses the square operation to remove the code phase information; secondly, we use the delay correlation and two times frequency estimation to estimate the starting frequency and the frequency modulation rate; finally, the wavelet transform algorithm is utilized to estimate the code rate parameter. Through the simulation analysis and full comparison with other methods, we can prove the performance superiority of this method under low signal-to-noise ratios (SNRs).

Neuronal sequences during theta rely on behavior-dependent spatial maps

Navigation through space involves learning and representing relationships between past, current and future locations. In mammals, this might rely on the hippocampal theta phase code, where in each cycle of the theta oscillation, spatial representations provided by neuronal sequences start behind the animal's true location and then sweep forward. However, the exact relationship between theta phase, represented position and true location remains unclear and even paradoxical. Here, we formalize previous notions of 'spatial' or 'temporal' theta sweeps that have appeared in the literature. We analyze single-cell and population variables in unit recordings from rat CA1 place cells and compare them to model simulations based on each of these schemes. We show that neither spatial nor temporal sweeps quantitatively accounts for how all relevant variables change with running speed. To reconcile these schemes with our observations, we introduce 'behavior-dependent' sweeps, in which theta sweep length and place field properties, such as size and phase precession, vary across the environment depending on the running speed characteristic of each location. These behavior-dependent spatial maps provide a structured heterogeneity that is essential for understanding the hippocampal code.

Aversive memory formation in humans is determined by an amygdala-hippocampus phase code

Memory for aversive events is central to survival, but can also become maladaptive in psychiatric disorders. Emotional memory relies on the amygdala and hippocampus, but the neural dynamics of their communication during emotional memory encoding remain unknown. Using simultaneous intracranial recordings from both structures in human patients, we show that in response to emotionally aversive, but not neutral, visual stimuli, the amygdala transmits unidirectional influence on the hippocampus through theta oscillations. Critically, successful emotional memory encoding depends on the precise amygdala theta phase to which hippocampal gamma activity and neuronal firing couple. The phase difference between subsequently remembered vs. not-remembered emotional stimuli translates to ∼25-45 milliseconds, a time period that enables lagged coherence between amygdala and downstream hippocampal gamma activity. These results reveal a mechanism whereby amygdala theta phase coordinates transient coherence between amygdala and hippocampal gamma activity to facilitate the encoding of aversive memories in humans.

Phase-encoded RF signal generation based on an integrated 49GHz micro-comb soliton crystal optical source

We demonstrate photonic RF phase encoding based on an integrated micro-comb source. By assembling single-cycle Gaussian pulse replicas using a transversal filtering structure, phase encoded waveforms can be generated by programming the weights of the wavelength channels. This approach eliminates the need for RF signal generators for RF carrier generation or arbitrary waveform generators for phase encoded signal generation. A large number of wavelengths—up to 60—were provided by the microcomb source, yielding a high pulse compression ratio of 30. Reconfigurable phase encoding rates ranging from 2 to 6 Gb/s were achieved by adjusting the length of each phase code. This work demonstrates the significant potentials of this microcomb-based approach to achieve high-speed RF photonic phase encoding with low cost and footprint.

Behavior-dependent spatial maps enable efficient theta phase coding

Navigation through space involves learning and representing relationships between past, current and future locations. In mammals, this might rely on the hippocampal theta phase code, where in each cycle of the theta oscillation, spatial representations start behind the animal’s location and then sweep forward. However, the exact relationship between phase and represented and true positions remains unclear and even paradoxical. Here, we formalize previous notions as ‘spatial’ or ‘temporal’ sweeps, analyze single-cell and population variables in recordings from rat CA1 place cells, and compare them to model simulations. We show that neither sweep type quantitatively accounts for all relevant variables. Thus we introduce ‘behavior-dependent’ sweeps, which fit our key observation that sweep length, and hence place field properties, such as size and phase precession, vary across the environment depending on the running speed characteristic of each location. This structured heterogeneity is essential for understanding the hippocampal code.

Probing signals with ZACZ for GPRonboard of unmanned aerial vehicle

<p><span>Modern ground penetrating radars (</span><span>GPR</span><span>), designed to determine the thickness of ice or search for the occurrence of aquifers in arid regions of the Earth, are installed either on helicopters or on the earth's surface. The use of a helicopter is economically expensive, and the installation of GPRs on the earth's surface is of a local nature. Modern GPRs mainly use video pulse probing signals and probing signals with linear frequency modulation. These signals have correlation noise, which makes it difficult to obtain a high-quality radar image. In this work, we propose to use a signal with a zero autocorrelation zone (ZACZ) as a probing signal for GPR installed on an unmanned aerial vehicle. In work, a polyphase probing signal with a ZACZ is synthesized and a comparative analysis of the correlation characteristics of the synthesized signal with the optimal phase-code shift keyed signal is carried out. </span></p>