13.1 Introduction

With many telecommunications services using radio transmissions, interference between services can arise in a number of ways. Figure 13.1 shows in a rather general way the possible interference paths between services. It will be seen in Fig. 13.1 that the terms earth station and terrestrial station are used, and the distinction must be carefully noted. Earth stations are specifically associated with satellite circuits, and terrestrial stations are specifically associated with ground-based microwave line-of-sight circuits. The possible modes of interference shown in Fig. 13.1 are classified by the International Telecommunications Union (ITU, 1985) as follows:

Figure 13.1: Possible interference modes between satellite circuits and a terrestrial station. ( Courtesy of CCIR Radio Regulations.)

A ₁: terrestrial station transmissions, possibly causing interference to reception by an earth station

A ₂: earth station transmissions, possibly causing interference to reception by a terrestrial station

B ₁: space station transmission of one space system, possibly causing interference to reception by an earth station of another space system

B ₂: earth station transmissions of one space system, possibly causing interference to reception by a space station of another space system

C ₁: space station transmission, possibly causing interference to reception by a terrestrial station

C ₂: terrestrial station transmission, possibly causing interference to reception by a space station

E: space station transmission of one space system, possibly causing interference to reception by a space station of another space system

F: earth...