Design of the Dynamic Supply CMOS RF Power Amplifie - Linear CMOS RF Power Amplifiers for Wireless Applications - page 35

Fig. 3.20 Simulated LC filter transfer function

Table 3.2 Simulated LC
filter characteristics

10 6

LC filter at ω n = 2 π × 1 . 62 × rad/s at f s = 33 MHz

Attenuation 3 . 02 dB 43 . 7dB

| φ LC | 89.9° 123.7°

φ td 2.75° 56°

| φ total | 92.7° 179.7°

R p 108 24 . 5

C p 560 pF 51 pF

to decrease simulation time, the high-efficiency modulator circuit was replaced by a
buffer with 80% efficiency. The simulation results for IMD3 and PAE are shown in
Figs. 3.21 and 3.22 . These figures also show the simulation results for the RF power
amplifier operating with a constant VDD of 2.5 V.
Figures 3.21 and 3.22 indicate that if we adopt a maximum IMD3 level of

− 35 dBc as a limit, with the dynamic supply the PA reaches a higher linear output

power and presents a higher efficiency than with a constant supply. More comments
on these graphs are given in Sect. 4.5 on p. 50, where similar results are obtained in
the experimental characterization. The simulation results at maximum linear output
power are summarized in Table 3.3 .