er Core network T/E copper fiber cable Figure 1.43 Illustration of an example satellite backhaul [79]. on orthogonal antenna polarizations (vertical and horizontal) and cross-polarization interfer- ence is canceled using digital signal processing. Spatial multiplexing significantly improves spectral efficiency and uses multi-antenna techniques to send multiple data streams over the same RF channel. A 2 X 2 MIMO link can ideally double the capacity. Spatial multiplexing has been used in many wireless access technologies including LTE/NR and IEEE 802.11n/ ac/ax, which relies on multipath interference and exploits spatial propagation paths caused by reflections. However, an LoS microwave link does not exhibit multipath phenomenon, thus a multipath condition is simulated by deliberate separation of the antennas, thereby cre- ating a pseudo multipath condition. While it is evident that high-density RF analog integra- tion is important to reduce the size and lower the component count, there are still many radio functions that rely on [discrete] RF building blocks. The IF circuitry and frequency up/down conversion require several key analog functions including phase-locked loop (PLL)5 frequency synthesizer, and the variable gain amplifier (VGA). Commercial satellite systems use very small aperture terminals (VSAT) for cost- effective delivery of telephony, broadband access, and video content. VSAT systems are deployed in enterprise-grade private networks, consumer broadband services, and cellular base station backhaul. In cellular base station backhaul applications, VSAT sys- tems are ideal for remotely located small-cell sites. Fig. 1.43 shows a typical VSAT system used in a base station backhaul application. Router and gateway VSAT A phase-locked loop is a control system that generates an output signal whose phase is related to the phase of an input reference signal. There are several different phase-locked loop types, but the simplest form is an electronic circuit consisting of a variable frequency oscillator and a p