Its function is to modulate the video signal (VIDEO) and audio signal (AUDIO) provided by the signal source (which can be AV signal sources such as digital TV set-top boxes, satellite digital TV receivers, DVD players, computers, cameras, TV demodulators, etc.) into stable high-frequency RF oscillation signals. Video is amplitude modulated and audio is frequency modulated.
According to the different color TV systems in the world, there are also three types of modulators: PAL, NTSC and SECAM. PAL-D is adopted in China.
1. The modulator adopts PAL-D standard adjacent frequency modulation mode for fixed channel output in the 48MHz - 750MHz frequency band.
2. In the circuit design, the image frequency and audio frequency CPU double phase locked loop (PLL) design idea is adopted.
3. Imported high-quality broadcast modulation chips (TOSHIBA, MOTOROAL, INTECH, TEXAS INSTRUMENTS, FAIRCHILD and other companies) are used in the device.
4. High performance surface acoustic wave (SAW) filtering is adopted, and the residual sideband suppression is greater than 65dB.
5、110 dBuv radio frequency Output, stable level amplitude, accurate frequency. 6. Unique wave filtering Mode, the out of band output suppression is greater than 65dB. 7. The image modulation, audio frequency offset, A/V ratio, and RF output electric average can be adjusted.
8. 19 inch standard case design, standardized installation.
Adjacent frequency modulator is used in various cable television systems, satellite television systems, residential closed-circuit television, monitoring systems, hotel and hotel digital set-top box transformation systems, as well as military and school education audio-visual systems.
name | Television modulator | name | Television modulator |
Image carrier output level | ≥ 110dbuV-20db adjustable | frequency range | Any channel within 49-750MHz |
Frequency accuracy | ≤5KHz | Image sound power ratio | -18db fixed |
Emissivity output impedance | 75Ω | RF output reflection loss | ≥13db |
Out of band parasitic output suppression | ≥60db | Sideband suppression | ≥60db |
Video input | 0.7-1.4Vp-p, 75 Ω positive polarity | Regulation | 87.5% adjustable |
Differential gain DG | ≤3% | Differential phase DP | ≤ 3 degrees |
Signal-to-noise ratio | ≥60db | Color light delay difference | ≤45ns |
In band flatness | ±1.2db | Audio input | 0.775Vrms, 20 Ω unbalanced |
power supply | ～220V ± 10% 50HZ | Overall dimension | 483mm X 136mm X 45mm |
Modulators can be divided into digital modulators and analog modulators;
According to different classification standards, analog modulators can be divided into:
According to the frequency vestigial sideband and double sideband, it can be divided into adjacent frequency modulator and frequency isolation modulator;
According to the frequency processing mode, it can be divided into: intermediate frequency processing modulator, high-frequency processing modulator;
Adjustable according to frequency can be divided into: frequency agile modulator, fixed frequency modulator;
It can be divided into standard modulator, professional modulator and broadcast modulator by level
According to the number of integrated channels, it can be divided into: single channel adjacent frequency modulator, 4-channel modulator, 8-channel modulator, and 16 channel modulator.
