WT4 Millimeter Waveguide System: Channelization

Channelization By E. T. HARKLESS, A. J. NARDI, and H. C. WANG (Manuscript received April 7, 1977) Waveguide networks operating in the millimeter wave region to separate the 62 transmitter and 62 receiver frequency spectra at each end of every waveguide transmission line are described. The overall loss of these networks for the various channels has been designed to complement the shape of the transmission medium loss in order to yield maximum repeater spacing. General descriptions of the design and performance of all filters used in the complete channelization array are given. I. NETWORK LAYOUT The main factors controlling the repeater spacing in the WT4 system are the available gain, the transmission medium loss, and the channelizing network loss. For each of the 124 channels, the available gain must exceed the sum of the transmission medium plus channelizing network losses. Both the transmission medium loss and the available gain are strong functions of frequency over the 40 to 110 GHz band. To obtain maximum repeater spacing and reduce systems costs, it is therefore necessary to plan the channelizing networks such that they will have minimum loss at the frequencies where the transmission medium loss is high and/or the available gain is low. Figure 1 plots the moderate terrain transmission medium loss and the projection of available gain for four-phase repeater development. (It is planned to set the repeater spacing such that four-phase repeaters can be introduced at some future date without change in repeater spacing or channelizing networks.) The plot clearly shows that the channelizing networks should be designed to minimize the loss at the edges of the band.