What is the effect of simultaneous switching noise on the performance of an adjacent RF circuit?

What is the effect of simultaneous switching noise (SSN) on the performance of an adjacent RF circuit? SSN creates broadband voltage ripple on the power and ground planes that can couple into RF circuits, degrading receiver sensitivity, PA linearity, and LO phase noise: (1) SSN mechanism: when multiple digital outputs switch simultaneously, they draw large transient currents (ΔI). The voltage drop across the parasitic inductance of the PDN: ΔV = L_PDN × dI/dt. For 64 outputs switching 50 mA each with 100 ps rise time: dI/dt = 64 × 0.050 / 0.0001 = 32 kA/s. With L_PDN = 100 pH: ΔV = 100e-12 × 32e6 = 3.2 mV. With L_PDN = 1 nH (poor PDN): ΔV = 32 mV. This ΔV appears on the ground plane and propagates as a wave toward the RF circuits. (2) Impact on RF circuits: LO phase noise: the VCO supply or tuning voltage noise modulates the oscillator frequency. A 1 mV noise at 10 MHz offset on a 2.4 GHz VCO: can degrade phase noise by 5-10 dB. Receiver sensitivity: SSN on the LNA supply modulates the LNA gain, creating intermodulation products. SSN on the mixer supply creates spurious mixing products. PA linearity: SSN on the PA supply modulates the PA bias point, creating: AM/PM conversion (phase noise in the output spectrum), and spectral regrowth (increased ACLR). ADC performance: SSN on the ADC reference or supply degrades the ENOB (effective number of bits). 1 mV of SSN noise reduces a 12-bit ADC to approximately 11-bit performance. (3) Coupling paths: conducted (through PDN): the primary path for SSN to reach RF circuits. Mitigated by: ferrite bead isolation, separate LDOs, and extensive decoupling. Radiated (near-field coupling): SSN creates magnetic and electric near-field emissions from the digital IC and its traces. These fields couple to nearby RF traces and components. Mitigated by: physical separation, shielding, and ground stitching. Ground plane coupling: high-frequency SSN currents flow in the ground plane and can generate a ground voltage difference between the digital and RF sections. Mitigated by: low-impedance ground (thick copper, many vias), and avoiding ground plane slots.