Radio Frequency Integrated Circuit Design - Webs

378 Radio Frequency Integrated Circuit Design
Figure 10.29 Class F frequency components of waveforms.
8
9 Vcm = VCC ∴ Vcm = 9
8 VCC
As an aside, the Fourier series for the ideal square wave is
sin � + 1
3
(10.33)
1
sin 3� + sin 5� . . . (10.34)
5
However, choosing Vcm3 = 1/3Vom would produce a nonflat waveform,
as shown in Figure 10.30.
The efficiency can be calculated as Po /P dc. By taking a Fourier series of
the iC (� ) waveform with a peak value of i cm, it can be shown that the dc
value I dc is equal to i cm/� and the fundamental value of the output current
Io is equal to i cm/2. As well, V om is equal to V cm. Thus, efficiency can be
calculated as
1
Po 2
=
P dc (io
1
� Vom)
=
I dcVCC
2�i cm
2
� 9
8 VCC�
i cm
� � V CC
= 9
8
Figure 10.30 Fundamental and third harmonic to make square wave.
� �
4 ⇒ 88.4% (10.35)