Measurement Results for the Frequency-Tunable CMOS RF Power Amplifie - Linear CMOS RF Power Amplifiers for Wireless Applications - page 114

Fig. 7.20 Hybrid frequency-tunable RF power amplifier schematic

7.5.1 Measurement Results for the Hybrid PA

In order to evaluate the benefits of the tunable PA, the conventional power amplifier
was also measured. It uses the same PA with the control circuit disabled. The trans-
former is replaced by a chip inductor of the value required to attain R opt = 150

at 300 MHz. Figures 7.21 and 7.23 show the IMD3 results for the 2-tone measure-
ments with tones centered at 200 and 300 MHz, and 500 kHz tone spacing. The
corresponding PAE results are given in Figs. 7.22 and 7.24 .
At 300 MHz, although the conventional PA was expected to present a better
performance, the tunable PA generates less distortion with almost equal PAE (at
the same output power) for output power levels greater than 7 dBm (5 mW). At
200 MHz, the tunable PA shows much lower IMD3 than its conventional counterpart
for output power levels lower than 11.2 dBm (13.2 mW). These measurement results
are summarized in Table 7.6 .
At an IMD3 level of

30 dBc, the tunable PA attains 10.5 dBm (11.2 mW) out-
put power and 15% PAE at 200 MHz, whereas the conventional PA attains 5.9 dBm
(3.9 mW) and 4.9%. The ratio between the efficiencies of the tunable and conven-
tional PAs is also shown in Fig. 7.22 , revealing that at 200 MHz, a relative improve-
ment of a factor of 1.38 (PAE ratio

−

= 138%) in PAE is attained using the tunable PA.

30 dBc IMD3, the tunable PA presents an output power of
10.1 dBm (10.2 mW) and a PAE of 15% against 7.8 dBm (6 mW) and 8.5% of the
conventional PA. The ratio between the efficiencies of the tunable and conventional

At 300 MHz and −