Vimesa FM Multiplexers

VIMESA FM MULTIPLEXERS Multiplexer systems have the mission of directing several high-power signals through a common antenna, while keeping the transmitters electrically isolated. This equipment is made up of filters formed by resonant cavities. The decoupling between transmitters and the losses are a function of the selectivity of the filters. In addition to others, there are basically two types manufactured by Vimesa. VIMESA FM MULTIPLEXERS This is undoubtedly one of the most widely used multiplexers in FM, due to its good characteristics and moderate cost. It consists of 2 band filters organized as follows with outputs connected by a star (Star Point).

Isolation between the inputs is provided by the rejection presented by the filter at the opposite frequency, which also limits the minimum separation between the frequencies. For 2-cavity filters, this separation must be greater than 2.5 MHz. With 3-cavity filters, separations of up to 1.2 MHz are acceptable, all in band II. Good adaptation is achieved by making the lines connecting the filters to the star so long that, from the point of attachment, each filter carries the frequency of the other with a very high impedance, as close as possible to an open circuit Insertion losses can vary between 0.1 and 0.7 dB, achieving adaptations of better than 26 dB. This diplexer has an important advantage and is capable of adapting impedances. With this, we can make the transmitter see a good load at its output, even if the antenna adaptation is not very good. Obviously, the energy returned by the radiating system will dissipate from the cavities in the form of heat. Constant impedance multiplexer. These types of multiplexers are suitable for their characteristics when high performance technical requirements are needed. They are based on quadrature hybrid couplers. They are the Multiplexers with which the highest performance is achieved, some of their fundamental characteristics are: very close frequency diplexing, high isolation between inputs, high elimination of spurious intermodulations and, above all, the ability to expand with the sum “n” of frequencies. They are made up of 2 band-pass filters with 2, 3 or 4 resonant cavities, depending on the proximity of the frequencies to the multiplex, 2 -3Db couplers and a balancing load; they are interconnected by high-quality lines.