On the other hand, in order to improve the linearity of Doherty power amplifier, one of the possible and simplified techniques is Composite Right/Left-Handed Transmission Lines (CRLH-TL) for its character of suppressing the second harmonic of the carrier amplifier of the Doherty power amplifier.
These two DPAs are all consisted of two identical GaN HEMT as carrier amplifier and peaking amplifier, the power ratio of the power divider is 2 : 1 in order to improve efficiency in a wide dynamic range of back-off power region.
where, [beta] is the saturated power ratio of the peak amplifier to carrier amplifier.
Hence, the saturated power ratio factor of the peak amplifier to carrier amplifier [beta] is equal to 18 approximately and the optimal OPBO point with peak efficiency in theory is 8.9 dB accordingly.
The advantage is that the carrier amplifier
amplifies only the average signal.
A conventional Doherty amplifier is composed of a carrier amplifier and a peak amplifier.
The Doherty amplifier consists of a carrier amplifier and a peak amplifier.
A Doherty amplifier consists of a carrier amplifier, a peak amplifier and a power combining network.
(2) The output of the carrier amplifier after passing through an inverter is combined with the output of the peak amplifier, as shown in Figure 1.
The RF performances of the Doherty amplifier-I (a combination of a class B carrier amplifier
and a bias-tuned class C peaking amplifier) have been compared with those of a class B amplifier alone.
The displayed amplifier shown is an 80 W IS-136 compliant PCS single carrier amplifier
operating from a wide range 20 to 30 V DC supply.
Consider this comparison for the 50 W single carrier amplifier
, [P.sub.out] = 50 W at the carrier frequency.