ual performance is available at those higher frequencies. 9.2.6.2 Radio-Frequency Interference (RFI). There are three facets to RFI in this context: (1) own microwave can interfere with other LOS microwave and satellite com- munication earth stations nearby, (2) nearby LOS microwave and satellite communication facilities can interfere with own microwave, and (3) own microwave can interfere with itself. To avoid self-interference (3), it is advisable to use frequency plans of CCIR (ITU- R organization) as set forth in the RF Series (Fixed Service). Advantage is taken of proper frequency separation, transmit and receive, and polarization isolation. CCIR also provides methods for interference analysis (coordination contour), also in the RF series. Another alternative is specialist companies, which provide a service of electromagnetic compatibility analysis. Table 9.3 LOS Microwave Frequency Bands 2110-2130 MHz 18,920-19,160 MHz 3700-4200 MHz 19,260-19,700 MHz 5925-6425 MHz 21,200-23,600 MHz 6525-6875 MHz 27,500-29,500 10,700-11,700 MHz 31,000-31,300 MHz 17,700-18,820 MHz 38,600-40,000 MHz 9.3 SATELLITE COMMUNICATIONS The IEEE defines electromagnetic compatibility (EMC) as "The requirements for electromagnetic emission and susceptibility dictated by the physical environment and regulatory governing bodies in whose jurisdiction a piece of equipment is operated." We'll call electromagnetic emission (EMI) RFI. It just means the level of RF interfer- ence caused by a certain piece of equipment such as a microwave terminal. Susceptibility deals with how well a piece of equipment can operate in an RFI environment. EMC can be a real headache for a microwave engineer. 9.3 SATELLITE COMMUNICATIONS 9.3.1 Introduction Satellite communications is an extension of LOS microwave technology covered in Section 9.2. The satellite must be within line-of-sight of each participating earth ter- minal. We are more concerned about noise in satellite communication links than we were with LOS microwave. In most cases, received signals will be