How do I select decoupling capacitors for a high speed digital IC to minimize EMI to nearby RF stages?

How do I select decoupling capacitors for a high-speed digital IC to minimize EMI to nearby RF stages? The decoupling strategy must target the specific frequency range where digital noise couples into the RF circuits: (1) Frequency targets: below 10 MHz: handled by bulk capacitors (10-100 μF electrolytic or tantalum) and the LDO regulator. 10 MHz-1 GHz: the critical range for RF interference. Handled by MLCC decoupling capacitors (100 nF, 10 nF, 1 nF). Above 1 GHz: handled by power/ground plane capacitance and on-die capacitance. (2) Capacitor selection: the self-resonant frequency (SRF) determines the effective range of each capacitor value. At resonance: the capacitor impedance is at its minimum (limited by ESR). Below resonance: the capacitor acts as a capacitor. Above resonance: the capacitor acts as an inductor (provides no filtering). Common values and their SRFs (0402 package): 100 nF: SRF ≈ 30-80 MHz. Effective: 10-100 MHz. 10 nF: SRF ≈ 100-300 MHz. Effective: 30-500 MHz. 1 nF: SRF ≈ 300 MHz-1 GHz. Effective: 100 MHz-2 GHz. 100 pF: SRF ≈ 1-3 GHz. Effective: 500 MHz-5 GHz. Use multiple values: a combination of 100 nF + 10 nF + 1 nF covers the entire 10 MHz-2 GHz range. This is the "decade bypass" strategy. (3) Placement: place the smallest capacitor closest to the IC power pin (shortest loop inductance). Place bulk capacitors near the power entry point. The loop area (from cap to pin to ground via and back) determines the parasitic inductance. Loop inductance: L_loop ≈ 0.5 nH for a well-placed 0402 cap within 1 mm of the pin. L_loop ≈ 2-5 nH for a cap placed 5-10 mm away. The loop inductance limits the high-frequency effectiveness of the capacitor. (4) Dielectric material: X5R/X7R: standard for digital decoupling. Low cost, high capacitance density. However: X5R/X7R ceramics exhibit piezoelectric noise (voltage-dependent acoustic emission that creates supply noise at 1-100 kHz). This noise can affect RF circuits (particularly ADCs and VCOs). NP0/C0G: no piezoelectric noise, very stable. Use for RF circuit decoupling and any capacitor near sensitive analog/RF stages. Lower capacitance density (maximum approximately 10 nF in 0402).