1.0 V RF and 1.8 V RF rails have very tight ripple specifications as ripple noise on these two rails affect the RF performance. Ripple on 3.3 V and 1.2 V rails do not directly affect the RF performance, but system level noise coupling could affect the RF performance; hence, it is necessary to minimize the ripple on these rails as well. Switching regulators have a fundamental ripple noise at switching frequency and this needs to be reduced. Table 2-4 provides the AWR device ripple noise specification. This ripple specification assumes a -105 dBc target spur level. If a higher spur can be tolerated based on the system requirements, then the ripple specifications can be relaxed. There is a dB-to-dB correlation between supply ripple and spur level. For example, a 1 dB increase in supply ripple will result in 1 dB increase in spur level.