Description of the parameters of the Geffen Af mat
2023-05-17
The large number of GEFFEN Geffen matrix models makes it difficult for customers to choose, and there is a lack of understanding of their parameters. Now, taking the AV matrix as an example, some professional parameters of the audio and video matrix are elaborated, such as gain, bandwidth, return loss, frequency response, etc.
gain
i.e. Gain. This is usually the ratio of a system's signal output to signal input.
Return loss
Also known as reflection loss. It is the reflection caused by the impedance mismatch of the cable link, and it is the reflection of the pair of wires themselves. Mismatches occur mainly where connectors occur, but they can also occur where the characteristic impedance changes in the cable, so the quality of construction is the key to improving return loss.
bandwidth
Bandwidth, also known as bandwidth, refers to the amount of data that can be transmitted at a fixed time, that is, the ability to transmit data in the transmission pipeline. There is a [-3dB] reference point for the transmission or processing of a video signal, which refers to the transmission bandwidth range or transmission distance of the video signal within the ideal effect, also known as the 1/2 power attenuation point.
Frequency response
It refers to the phenomenon that when an audio signal output with a constant voltage is connected to the system, the sound pressure generated by the speaker increases or decreases with the change of frequency, and the phase changes with the frequency. It also refers to the frequency range that the sound system can reproduce within the range of amplitude, and the amount of change in the signal within this range is called frequency response, also known as frequency characteristics.
Channel Crosstalk
Channel crosstalk is caused by the mutual interference between two or more signals, usually from one adjacent channel to add additional signals to the effective signal, will cause the image to appear [ghosting phenomenon]. Electromagnetic radiation, capacitive induction, and poor shielding are the main causes of channel crosstalk. Channel crosstalk is commonly expressed in dB, and it is absolutely negative, the smaller the value, the better the channel isolation, and the smaller the effect of signal crosstalk. The channel crosstalk data of any video matrix at different frequencies will be different, generally the higher the frequency, the larger the value: for example, the channel crosstalk of a matrix is -55dB at 10MHz, -45dB at 30MHz, and -37dB at 100MHz, which shows that the channel crosstalk of this matrix is slightly higher than that of 10MHz when transmitting 10MHz signals.
Differential Gain Error
The distortion of the amplitude of the chromaticity signal caused by the change of the amplitude of the image brightness signal is called differential gain distortion, and the color saturation distortion under different brightness backgrounds affects the color effect (such as wearing bright red clothes from dark to bright places, and bright red clothes becoming thicker or lighter). GY/T107-92 (Video Operation Index of TV Broadcast Control System) Class A standard stipulates that the differential gain distortion ± 0.2%
Differential Phase Error
The distortion of the chromaticity signal phase caused by the amplitude change of the image brightness signal is called differential phase distortion, and the hue is distorted under different brightness backgrounds, which will cause one color to change to other colors (for example, wearing bright red clothes from dark places to bright places, bright red clothes will be yellowish or purple). GY/T107-92 (Video Operation Index of TV Broadcast Control System) Class A standard stipulates that differential phase distortion ± 0.2°.
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