The formulas derived by Stette [1] permit the calculation of TWT output carrier power and intermod power when the input to the TWT consists of an infinite number of infinitesimal carriers. The formulas for these quantities involve an integration of the TWT singlecarrier characteristic over a semi-infinite range, and for most of the TWT's one considers, a simple approximation of the integration by a summation gives satisfactory answers. However, when one considers special TWT's, e.g., linearized TWT's or the piecewise linear limiter [2], simple approximations are often not good enough. To get accurate results, a multipoint Gaussian quadrature must be used.

When more than one FM carrier is put through a TWT (or SSPA), the output consists of the original carriers plus intermod lines. The procedure for calculating these lines has been studied by several authors in recent years because of the rapid growth of satellite communications in which TWT's (and SSPA's) play a major role. Basically, these intermod calculations are used to design multiple carrier arrangements in a single satellite transponder so that the transponder can be filled to its capacity. Since this optimum point is usually achieved when the carriers are unequal in power, the methods derived so far have focused on this case. However, if an equal carrier case must be evaluated just once, and the number of carriers is moderately high and the intermod order is high (greater than third order), the present known methods are unsuitable. This report will present a method for solving this special case.