# US 11,444,589 B2 · Bias circuit for a Doherty amplifier, and a wireless communication system

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- Number: US 11,444,589 B2
- Document ID: US11444589B2
- Status: Granted
- Kind: B2
- Application number: 17/316,926
- Filed: 2021-05-11
- Published: 2021-11-18
- Granted: 2022-09-13
- Earliest claimed: 2020-05-13
- Assignees: Syntronic AB
- Applicants: Syntronic AB
- Inventors: Zhancang Wang
- Web page: https://patentgrep.com/patent/US11444589B2

## CPC

- H03F 3/211: {using a combination of several amplifiers (H03F3/60 takes precedence)}
- H01P 5/16: Conjugate devices, i.e. devices having at least one port decoupled from one other port
- H03F 1/0261: {with control of the polarisation voltage or current, e.g. gliding Class A}
- H03F 1/0283: {Reducing the number of DC-current paths}
- H03F 1/0288: {using a main and one or several auxiliary peaking amplifiers whereby the load is connected to the main amplifier using an impedance inverter, e.g. Doherty amplifiers}
- H03F 1/30: Modifications of amplifiers to reduce influence of variations of temperature or supply voltage {or other physical parameters (in differential amplifiers H03F3/45479)}
- H03F 1/56: Modifications of input or output impedances, not otherwise provided for
- H03F 3/245: {with semiconductor devices only}
- H03F 3/68: Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics {(power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602)}
- H04B 1/38: Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B 7/0413: MIMO systems
- H03F 2200/12: A bias circuit for some stages being shown using transmission lines
- H03F 2200/451: the amplifier being a radio frequency amplifier
- H03F 2200/555: A voltage generating circuit being realised for biasing different circuit elements
- H03F: AMPLIFIERS
- H01P: WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE (operating at optical frequencies G02B)
- H04B: TRANSMISSION

## Abstract

A bias circuit for a Doherty amplifier, characterized by comprising: an input port with an input impedance, wherein the input port is configured to receive a bias signal from a power supply; a first output port configured to provide a bias signal to an amplifier; a second output port configured to provide a bias signal to an amplifier; a two port impedance transformer with an input connected to the first input port, and an output of the two port impedance transformer having an intermediate impedance; an in-phase N-port dividing impedance transformer with an input connected to the output of the two port impedance transformer, wherein the in-phase N-port dividing impedance transformer comprises: a first output connected to the first output port having a first output impedance; and a second output connected to the second output port having a second output impedance.

## Claims

### Claim 1

A bias circuit for a Doherty amplifier, comprising:
an input port with an input impedance, wherein the input port is configured to receive a bias signal from a DC power supply;
a first output port configured to provide a bias signal to an amplifier;
a second output port configured to provide a bias signal to an amplifier;
a two port impedance transformer with an input connected to the input port, and an output of the two port impedance transformer having an intermediate impedance;
an in-phase N-port dividing impedance transformer with an input connected to the output of the two port impedance transformer, wherein the in-phase N-port dividing impedance transformer comprises:
a first output connected to the first output port having a first output impedance; and
a second output connected to the second output port having a second output impedance.

### Claim 2 (depends on 1)

The bias circuit according to claim 1, wherein:
the second output impedance is equal to the first output impedance;
the input impedance is greater than the intermediate impedance; and
the first output impedance and the second output impedance are greater than the intermediate impedance.

### Claim 3 (depends on 1)

The bias circuit according to claim 1, wherein the in-phase N-port dividing impedance transformer comprises physical loads connected to wave-guides thereof.

### Claim 4 (depends on 3)

The bias circuit according to claim 3, wherein the physical loads are selected from lumped elements, transmission line stubs, or hybrid devices.

### Claim 5 (depends on 1)

The bias circuit according to claim 1, wherein the in-phase N-port dividing impedance transformer is a Wilkinson impedance transformer, or a Gysel impedance transformer.

### Claim 6 (depends on 1)

The bias circuit according to claim 1, wherein the bias circuit is provided on a printed circuit board with micro strip waveguides, which forms the two-port impedance transformer and the in-phase N-port dividing transformer.

### Claim 7 (depends on 1)

The bias circuit according to claim 1, wherein the in-phase N-port dividing impedance transformer further comprises:
N−2 outputs, wherein each one of the N−2 outputs is connected to a corresponding output port of the bias circuit, and wherein each of the corresponding output ports has an impedance equal to the first and the second output impedance.

### Claim 8 (depends on 1)

A wireless communication system, comprising:
a baseband processor;
a power supply connected to the baseband processor;
a power amplifier with multiple amplifying circuits, wherein the power amplifier comprises an input connected to the baseband processor;
the bias circuit according to claim 1, wherein the input port of the bias circuit is connected to the DC power supply, and the first output port, and the second output port of the bias circuit are connected to respective multiple amplifying circuits of the power amplifier; and
a plurality of antennas are connected to outputs of the power amplifier.