2020年3月13日星期五

Effect of operating frequency on system power, penetration ability, equipment volume, and system performance

Note:
This article considers empirical situations and may not apply to all situations.

1. Effect of frequency on power

Generally speaking, the higher the frequency, the smaller the power.
The power affects the working distance. Therefore, the system with a higher frequency often has a smaller working distance. The phenomenon that millimeter waves are commonly used in vehicles, 5G small cells, etc. can be explained with this.


2. Frequency vs. Penetration Capability

Generally, the lower the frequency, the stronger the penetration. (The penetrating ability here refers to the penetrating ability of the detection, that is, the diffractive ability. It does not refer to the energy penetration of gamma rays, lasers, etc.)

3. Relationship between frequency and device volume

Generally, when the other conditions are the same, the larger the operating frequency, the smaller the equipment size. This can be understood from the perspective of receiving and transmitting antennas. For example, millimeter waves can be chip-sized.

4. Relationship between frequency and system performance

When selecting a frequency, the cost is usually known, and the available frequency is determined based on the nature of the budget and frequency. For example, when the budget cost is low, a more mature frequency band should be selected.

Image aliasing (Moire pattern)

Image sampling and quantization are necessary steps in digital image acquisition and storage.

According to Nyquist's sampling law:

An analog signal can be perfectly reconstructed form its samples as long as the sampling frequency is at least twice the amount of the maximum frequency component present in the analog signal.

That is, the sampling frequency is at least twice the highest frequency in the analog signal. Otherwise, aliasing will occur.


Python regular expressions match specific input and output images

The saved results of an image generation experiment are the following pictures. Now I want to calculate the SSIM and PSNR between * _real_image * and * _synthesized * in the same iterations.


Calculate picture SSIM and PSNR using Python

This article mainly shows the calculation of two pictures psnr and ssim using Python.


Some reasons for error "Segmentation fault (core dumped)"

Sometimes we encounter "Segmentation fault (core dumped)", meaning that memory is used incorrectly, which may be caused by the following reasons.

1. Caused by breakpoints in the program

It may be caused by breakpoints in the program for debugging, such as pdb.set_trace (), etc.

In most cases, the pdb debugging tool that comes with Python will not cause problems, but individual cases do occur. The specific reason is not clear, but you can just remove pdb.set_trace () to solve it.

2. Mismatch between number of objects and number of categories

This is easy to appear in the debugging process of specific segmentation detection tasks such as yolo. You can change the number of filter files, or the number of categories to solve. The specific solution should be determined according to the specific situation.