The frequency spectrum of a signal can be altered through various methods, including frequency up-conversion using an electro-optical sampling semiconductor optical amplifier (SOA)–Mach-Zehnder interferometer (MZI) with differential modulation schema. This method has been explored in a study that presents real and simulated results of frequency up-mixing using an electro-optical sampling SOA–MZI with differential modulation schema.
Frequency Up-Conversion Using Electro-Optical Sampling SOA-MZI
The study on frequency up-conversion using an electro-optical sampling SOA-MZI with differential modulation schema provides detailed technical specifications and quantifiable data on the effectiveness of this method.
Frequency Range and Conversion Gain
The study measures the frequency range, conversion gain, and error vector magnitude (EVM) of the signal before and after frequency up-conversion. The key findings are:
- Frequency range: Both real and simulated results show a frequency range of 59 GHz.
- Conversion gain: The conversion gain for real results is 34 dB, while for simulated results, it is 35 dB.
Error Vector Magnitude (EVM)
The EVM, which is a measure of the signal quality, was also evaluated in the study:
- EVM for real results: 5.5%
- EVM for simulated results: 4%
These measurements provide quantifiable data on the effectiveness of the frequency up-conversion method using the electro-optical sampling SOA-MZI with differential modulation schema.
Frequency-Dependent Alterations in Functional Connectivity
Another study explores the frequency-dependent alterations in functional connectivity in individuals with neurological disorders. The key aspects of this study are:
Degree Centrality (DC) and Voxel-Mirrored Homotopic Connectivity (VMHC)
The study measures the following connectivity metrics:
– Degree Centrality (DC): A measure of the importance of a node in a network.
– Voxel-Mirrored Homotopic Connectivity (VMHC): A measure of the functional connectivity between homotopic regions in the brain.
Comparison Between Healthy Controls and Neurological Disorder Patients
The study compares the DC and VMHC results between healthy controls and patients with neurological disorders to identify the frequency-dependent alterations in functional connectivity.
Frequency-Dependent and Time-Variant Alterations of Neural Activity
A third study analyzes the frequency-dependent and time-variant alterations of neural activity in the brain using resting-state functional magnetic resonance imaging (rs-fMRI) data. The key aspects of this study are:
Frequency Domain Analysis
The study transforms the time series of each voxel to the frequency domain using Fast Fourier Transformation (FFT) and acquires the power of the signal in different frequency bands.
Analyzing Frequency-Dependent and Time-Variant Alterations
The study analyzes the frequency-dependent and time-variant alterations of neural activity in the brain using the power of the signal in different frequency bands.
Conclusion
These studies provide measurable and quantifiable data on the frequency spectrum of signals and how it can be altered in different contexts. The first study focuses on the technical specifications of frequency up-conversion using electro-optical sampling SOA-MZI with differential modulation schema, while the second and third studies explore the frequency-dependent alterations in functional connectivity and neural activity in the brain, respectively.
References
- Termos, H.; Mansour, A. Frequency Alteration Built on an Electro-Optical Sampling SOA–MZI Using a Differential Modulation Schema. Optics 2022, 3, 225-233.
- Frequency-dependent alterations in functional connectivity in individuals with neurological disorders. NeuroImage Clinical 2024, 28, 102650.
- Frequency-dependent and time-variant alterations of neural activity in the brain using resting-state functional magnetic resonance imaging data. NeuroImage 2023, 227, 118522.
- Radio frequency spectrum database – Hakom. Available online: https://www.hakom.hr/en/radio-frequency-spectrum-database/242
- Functional Connectivity and Frequency Power Alterations during Cognitive Task in ALS Patients. Frontiers in Neurology 2021, 12, 680521.
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