Constant Impedance Combining Filter
also called Bridge Diplexers

It is possible to connect several tranmitters to a single antenna. This system is convenient when the working frequencies of the transmitters have a minimum spacing < 1.4 MHz. With our modular configuration it is possible to have the band pass filters with three cavities so that we can connect transmitters with working frequencies with spacing up to 0.8 MHz. Constant impedance combining filters - see fig. 1 - permit an expansion of the transmitters system for future necessity. This equipment includes band/pass filters (double cavity or triple cavity) connected with 3 dB couplers (or hibrid coupler). The power of the TX1 enters into the first hybrid coupler (narrow-band input) and is divided in two halves while the filters are tuned on TX1 frequency. The TX1 power is recombined again in the second 3 dB coupler, and sent to antenna system. Hybrid coupler provides the isolation between TX1 and TX2. TX2 similarly, enters into the second hybrid coupler (broadband input), where is divided and flows toward band ass filters (both tuned on TX1 frequency) where is reflected. The signal goes to output where is connected the antenna and added to TX1 signal. The isolation between the TX1 and TX2 signals is obtained by using hibrid couplers and band pass filters. This system is more expensive than star type combining filter, but sometime, for techincal reasons, is more reliable