MMDS Microwaves Multipoint Distribution
The MMDS Transmitter is a fully-solid-state device, forced air cooled, intended for use in the MMDS SHF BAND (2500 to 2700 MHz or 2300 to 2500 MHz - other bands available on request). The output is obtained by converting the entire UHF band with a LO at 1838MHz. In order to improve linearity, the device employs GaAsFET semiconductors working in class A. The audio/video amplification is combined and amplification is separated for each individual channel (4 channels in figure), available on request the multi-channel amplification version. It includes both the transmitter and the RF amplifier in a single unit. The RF amplifier directly powers a radiant antenna or a power combiner in case of multi-channel transmission.
The device has modular design to facilitate maintenance. Other features are available to provide automatic video gain control, sync pulse shape restoration with amplitude stabilisation, black-level clamping and peak-white limitation. IF SAW filters, specified according to the particular standard, are employed in the VSB modulator of the transmitter drive. Channel changing operations are simple and easy to perform.
The device has IF linearity pre-correction that, together with the high degree of linearity and the optimisation of the RF circuits, minimizes intermodulation thus permitting the use of adjacent channel systems. The user interface has been kept simple and intuitive with the use of an alphanumeric display and only two push-buttons to control output power, temperature, channel, audio and video inputs. All functions can be remoted by the RS232 rear panel connector.
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