US 12,328,100 B2
Doherty amplifier and communication device
Shuichi Sakata, Tokyo (JP); Yuji Komatsuzaki, Tokyo (JP); and Shintaro Shinjo, Tokyo (JP)
Assigned to MITSUBISHI ELECTRIC CORPORATION, Tokyo (JP)
Filed by Mitsubishi Electric Corporation, Tokyo (JP)
Filed on Apr. 18, 2022, as Appl. No. 17/722,839.
Application 17/722,839 is a continuation of application No. PCT/JP2019/048944, filed on Dec. 13, 2019.
Prior Publication US 2022/0239259 A1, Jul. 28, 2022
Int. Cl. H03F 3/21 (2006.01); H03F 1/02 (2006.01); H03F 1/56 (2006.01)
CPC H03F 1/0288 (2013.01) [H03F 1/56 (2013.01); H03F 3/211 (2013.01); H03F 2200/451 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A Doherty amplifier comprising:
a first transmission line having a first end connected to an input terminal to which a signal to be amplified is input;
a second transmission line having a first end connected to the input terminal;
a resistor connected between a second end of the first transmission line and a second end of the second transmission line;
a carrier amplifier to amplify a signal output from the second end of the first transmission line and output the amplified signal to an output combining point; and
a peak amplifier to amplify a signal output from the second end of the second transmission line and output the amplified signal to the output combining point,
wherein the Doherty amplifier is configured such that:
a ratio of a characteristic impedance of the second transmission line to a characteristic impedance of the first transmission line is a power division ratio of the signal to be amplified between the carrier amplifier and the peak amplifier when both of the carrier amplifier and the peak amplifier are saturated, and
a resistance value of the resistor is a value obtained by multiplying, by a proportionality coefficient that is equal to or greater than 0 but less than 1, a sum of an input impedance of the carrier amplifier when the carrier amplifier reaches saturation and an input impedance of the peak amplifier when the peak amplifier reaches saturation,
wherein the Doherty amplifier further comprises:
a coefficient adjustment line that is connected between the second end of the second transmission line and the peak amplifier and adjusts a reflection coefficient of a signal at the peak amplifier, which is obtained when the peak amplifier is viewed from the second end of the second transmission line; and
a phase adjustment line that is connected between the second end of the first transmission line and the carrier amplifier and has an electrical length same as an electrical length of the coefficient adjustment line.