Background:
The High Definition TV "experience" continues to offer the producers really drive digital devices. The days of analog video interfaces are limited. In previous articles we mentioned HDMI. It 'clear that HD sources such as DVD players, satellite set-top box decoder for HDMI, too. It 's inevitable that future HD sources such as HD-DVD players (HD or Blu Ray) and PS3 will use HDMI as an interfaceStandard. With all these new HDMI sources, such as the desired input to the HD monitor? HDMI Switch: In this article we will go into the details of those arrangements.
Hdmi
What is a HDMI switch:
An HDMI switch allows the end user to select multiple HDMI sources such as DVD players, set-top box, a monitor in HD. The basic models are available 2x1 HDMI switch, which simply means that there are 2 inputs and 1 output. The 2x1 HDMI switch allows the user to switch between 2 HDMI SwitchSources. There are also 4x1 HDMI switches available which allows the user to select up to 4 HDMI sources as possible. By the way, we encourage users to select high, 4-door model for future expansion.
Why do I need an HDMI switch: Who can an HD monitor with less than the desired number of HDMI inputs use external HDMI switch to expand the system.
What should I look for in an HDMI switch:
- Expandability: 4 ports devices are recommended for future expansion. If youUse a 2-door, then you have extensibility. E 'likely that future HD sources such as games stations, HD DVD player / recorders will use HDMI.
- Transparency HDCP: any change must pass HDCP data between source and display.
- Compatibility with DVI-D: a mixture of both HDMI and DVI-D in the field. People should have a HDMI switch rather than a DVI-D switch since HDMI compatible with DVI-D. With an HDMI switch. The user selects the onlycorrect cables needed, HDMI or HDMI / DVI-D to customize the system.
- Remote control: a remote control to select the desired channel is essential.
Design consideration of a HDMI switch:
HDMI is extremely high speed digital transmission standard, with a rate of total lettable area of ~ 4.95 Gbps of data. Jean Baptiste Fourier (1768-1830) showed that any waveform in a summation of sine wave harmonics content can be resolved. may be the amplitude of sine wavesdetermined by calculating the Fourier transform.
What is the word in some dead French mathematician have to do with the HDMI switch? Well, tell us that the waveform is a Fourier sum of sine wave harmonics content. Therefore, the higher data rates, a higher frequency of sine waves. Incidentally, the fundamental frequency of the sine wave is half the speed of data transmission. For example, the fundamental frequency of a 2 Gbit / s (50% duty cycle) square wave is 1GHz.
As data ratesincrease, every aspect of the switch design (every millimeter) is critical because the wavelengths of the signals on the size of the components on board approach. The 3 critical parameters to consider:
Impedance:
HDMI is based on a 100 ohm (differential) impedance-based. E 'imperative that the switch is optimized for the characteristic impedance can be adjusted. Any imperfections in the board layout because of the "reflections" that reduced signaling to the HD monitor. Think"reflection", as the signals that are lost between inputs to output. With careful RF and microwave layout techniques minimizes these reflections.
Minimum insertion loss:
loss of signal must be minimized to maximize the integrity of the output signal of the HDMI switch. Again, careful with RF and microwave layout techniques minimizes insertion loss.
Minimum Cross Talk:
With multiple inputs (up to 4), all potentially active at the same time,essential that the channel is not disturbed by any unwanted channels. Again attention to minimize RF microwave design techniques of crosstalk.
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