Measurement Setups and Additional Screenshots - Linear CMOS RF Power Amplifiers for Wireless Applications - page 125

Chapter 9
Appendix A: Measurement Setups
and Additional Screenshots
Abstract This first of two appendices presents the setups used for the measure-
ments performed to characterize the RF power amplifiers treated in this topic. The
setups for S-parameter, 2-tone, and OFDM measurements are described. It also pro-
vides a few additional screenshots taken from the measurement instruments.
9.1 Setups Used for the S-Parameter Measurements
Figure 9.1 depicts one of the setups used for S-parameters measurement. This was
the setup used in Sect. 7.2 on p. 102 where no RF choke is employed. In this case,
the output bias tee plays the role of both the output DC blocking capacitor and the
RF choke inductor. At the input, a bias tee is also used for a similar purpose.
The signal from port 1 of the network analyzer arrives at the evaluation board
through an SMA cable (50 cm long and with tight tolerances) and the input bias tee.
The output signal arrives from the evaluation board to port 2 of the network analyzer
also through an SMA cable and a bias tee. The current flowing through the PA is
measured with a true-rms handheld digital multimeter. Three DC voltage sources are
used for gate bias, drain bias, and VDD (in fact the triple-well technology requires
that the deep n -well be always connected to the highest positive voltage present in
the circuit). Three bench-top digital multimeters are used to monitor these voltages.
Figure 9.2 depicts the second setup used for S-parameters measurement. This
setup was used in Sect. 4.4 on p. 45 where an RF choke is used for the RF PA drain
bias. The difference with respect to the previous setup is that one DC voltage source
is eliminated because the drain bias voltage comes also from VDD. The output bias
tee is used only for DC blocking with its DC input left unconnected. Table 9.1 lists
the instruments used in the S-parameter measurement setups.
9.2 Setup Used for the 2-Tone Measurements
The setup for the 2-tone measurements used to obtain the results for the dynamic
supply RF power amplifier presented in Sect. 4.5.1 on p. 50 is depicted in Fig. 9.3 .