In general telecommunications, modulation is a process of conveying message signal, for example, a digital bit stream or an analog audio signal, inside another signal that can be physically transmitted.
A modulator is a device that performs modulation. A demodulator (sometimes detector or demod ) is a device that performs demodulation, the inverse of modulation. A modem (from modulator–demodulator) can perform both operations.
QAM conveys data by changing some aspect of a carrier signal, or the carrier wave, (usually a sinusoid) in response to a data signal. In the case of QAM, the amplitude of two waves of the same frequency, 90° out-of-phase with each other (in quadrature) are changed (modulated or keyed) to represent the data signal. Amplitude modulating two carriers in quadrature can be equivalently viewed as both amplitude modulating and phase modulating a single carrier.
In the digital television program broadcast process, QAM modulator need to complete QAM modulation and upconversion processing of stream. For the multi-level transmission and broadcasting digital TV service, in order to correctly operate the EPG, the QAM modulator needs to change the partial SI and PSI for the information of the transmitted stream in the function, which making the broadcast service in line with the description of TS stream.
QAM modulator is mainly used in digital headend television broadcasting, which is composed of the QAM modulator and digital upconversion，modulated input serial or parallel stream by the QAM module, modulated to the IF frequency, and then through the upconversion module change frequency conversion, to meet the requirements of the standard channel or supplementary channel, and then mixed into the CATV network, the terminal received by the STB.
1.DVB / MPEG-2 stream become standard channel or additional channels to meet requirements after QAM modulation and up-conversion processing,
2. Provide a complete digital TV transmission system used in conjunction with my company's digital TV system products
3.QAM modulator input stream includes formats of ASI input, DS3 (optional) input
4. the output frequency range is: 47MHz~900MHz
5. Web browser management for local and remote management, monitoring and control
1.Digital headend system base on IP network, HFC network edge
2.Broadcast Application built-in multiplexing and scrambling function
3.MPEG-TS transmission over local IP network
4.VOD Edge QAM modulator
IPQ6250 Plus (http://www.dibvision.com/broadcast-ip-to-qam-modulator-ipq6250-plus)a professional broadcast grade device dedicated to three-network convergence platform in the high speed IP-based head-end series, which is a new generation of modular & high density Edge QAM modulator combining multiple Gigabit Ethernet input, transport stream re-multiplexing, scrambling, maximum 144 channel QAM modulation in a 1U rackmount unit.
It supports 24/48/72 QAM channels by using three external pluggable 24 QAM modules, each of QAM modules supporting up to two Gigabit copper interfaces. Moreover, the IPQ6250 Plus supports 1+1 redundant & hot-swappable power supplies for high reliability and stability of system. Its pay-as-you-grow modular design, flexible configurations and licensing mechanism are making the IPQ6250 Plus unparalleled scalability, reliability and system performance to cable operators.