 explain. The RSL is the level or power of the received signal in dBW or dBm as measured at the input of the receiver's mixer or, if the receiver has an LNA (low-noise amplifier), at its input. This is illustrated in the block diagram of a typical LOS microwave receiver shown in Figure 9.6. In Figure 9.6, the incoming signal from the antenna (RF) is amplified by the LNA and then fed to the downconverter, which translates the signal to the intermediate frequency (IF), often 70 MHz. The IF is amplified and then inputs the demodulator. The demodu- lator output is the serial bit stream, replicating the input serial bit stream at the far-end transmitter. The next step in the path analysis (link budget) is to calculate the free-space loss between the transmit antenna and the receive antenna. This is a function of distance and Table 9.2 Digital LOS Microwave Basic Equipment Parameters Parameter Normal Special Comments Transmitter power 500 mW common above 10 GHz Receiver noise figure 4-8 dB 1-2.5 dB Use of low-noise amplifier Antenna Parabolic, 2- to Antennas over 12 ft not 12-ft diameter recommended Modulation 64-256 QAM Up to 512 QAM, Based on bandwidth Note: Bit packing or QPR, or bit rate constraints, requirements QAM/trellis or bandwidth desired in case of SONET/SDH CONCEPTS IN TRANSMISSION TRANSPORT Down- Demodulated Demodulator Converter Amplifier Output (bits) A or B Local Point of RSL measurment Oscillator Figure 9.6 Simplified block diagram of an LOS microwave receiver. RF is radio frequency; IF is intermediate frequency; LNA is low-noise amplifier. Point A is used to measure RSL when and LNA is employed, which is optional. Otherwise, the measurement point is point B, at the input of the downconverter. frequency (i.e., the microwave transmitter operational frequency). We then calculate the EIRP (effective isotropically radiated power) at the transmit antenna. The EIRP (in dBm or dBW, Appendix C) is the sum of the transmitter power output, minus the transmission line losses plus the antenna gain, all in decibel