Chapter 7

Payload's Communications Parameters

7.1 Introduction

This chapter presents the communications parameters found in the top-level payload requirements document with the intent to fully explain the following for each:

  • What the parameter is
  • How the parameter's application at unit level relates to its application at payload level
  • How the parameter is verified.

What these parameters mean to the signal quality is discussed in Chapter 10, after the basics of communications theory are presented there.

Figure 7.1 gives the simplified transponder diagram used in the sections below, for marking the payload elements that contribute to a parameter value, when there is more than one such element. (“Element” means either a unit or an element used to integrate the payload, such as a piece of waveguide.) The high-power amplifier (HPA) subsystem is identified in the figure because reference is made to it in a couple of places.

Figure 7.1 Simplified transponder diagram for showing main contributors to each communications parameter.

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Each payload element enhances the reception and retransmission of the signal in some way but also inevitably distorts the signal in some minor way. The elements can be divided into two classes: those that cause basically linear distortion and those that cause nonlinear distortion. The effect of linear distortion on communications is easier to analyze. The elements ...

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