Curve Fitting Circuit, Analog Predistorter, and Radio Frequency Signal Transmitter

• US 20170302233A1
• Filed: 04/28/2017
• Published: 10/19/2017
• Est. Priority Date: 10/31/2014
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Huang, Wei
• Granted Patent: US 10,141,896 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 17/10 Complex mathematical operations function generation by table look-up G06F1/03; evaluation of elementary functions by calculation G06F7/544
• CPC Class Codes: G06F 17/17 Function evaluation by approximation methods, e.g. inter- or extrapolation, smoothing, least mean square method G06F17/18 takes precedence ; interpolation for numerical control G05B19/18
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 1/3258 based on polynomial terms
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/20 Power amplifiers, e.g. Class B amplifiers, Class C amplifiers H03F3/26 - H03F3/30 take precedence
• CPC Class Codes: H03F 3/245 with semiconductor devices only

Abstract

A curve fitting circuit, an analog predistorter, and a radio frequency signal transmitter are disclosed. Each segmentation processing circuit in the curve fitting circuit generates a to-be-processed signal according to a intercepted part of a received signal, and generates q output signals according to the to-be-processed signal. Parts intercepted by different segmentation processing circuits are not exactly the same. Each first adder circuit in the curve fitting circuit receives one signal in the q output signals of each segmentation processing circuit, and obtains one output signal of the curve fitting circuit according to a sum of received n signals.

Claims

1. A curve fitting circuit, comprising:

n segmentation processing circuits, wherein n is greater than or equal to 2; and

q first adder circuits, wherein q is a natural number;

wherein each segmentation processing circuit of the n segmentation processing circuits is configured to;

receive an input signal;

intercept a part of the input signal according to a preset rule;

generate a to-be-processed signal according to the intercepted part; and

generate q output signals according to the to-be-processed signal using a polynomial fitting method, wherein parts of the input signal intercepted by different segmentation processing circuits are not exactly the same; and

wherein each first adder circuit is configured to;

receive one signal in the q output signals of each segmentation processing circuit; and

obtain one output signal of the curve fitting circuit according to a sum of received n signals, wherein different first adder circuits receive different output signals in q output signals of a same segmentation processing circuit.

2. The curve fitting circuit according to claim 1, wherein obtaining the one output signal of the curve fitting circuit according to the sum of received n signals comprises:

when none of the received q output signals of each segmentation processing circuit comprise a constant term, use a signal, obtained by adding the sum of the received n signals to a constant term, as the one output signal of the curve fitting circuit;

or

when q output signals of at least one segmentation processing circuit comprise a constant term, use the sum of the received n signals as the one output signal of the curve fitting circuit.

3. The curve fitting circuit according to claim 1, wherein intercepting a part of the input signal according to a preset rule comprises:

determining the intercepted part according to an amplitude of the input signal and a preset amplitude range of the segmentation processing circuit.

4. The curve fitting circuit according to claim 1, wherein intercepting a part of the input signal according to a preset rule comprises:

intercepting a part between two points of the input signal.

5. The curve fitting circuit according to claim 4, wherein each segmentation processing circuit comprises an amplitude limiting circuit, a polynomial operation circuit, and a weighting circuit;

wherein the amplitude limiting circuit is configured to;

receive an input signal; and

generates and output, when an amplitude of the input signal is within a preset amplitude range of the segmentation processing circuit at which the amplitude limiting circuit is located, a to-be-processed signal whose amplitude monotonically varies according to the amplitude of the input signal, or outputs a first preset value when the amplitude of the input signal is less than a minimum value of the preset amplitude range, or outputs a second preset value when the amplitude of the input signal is greater than a maximum value of the preset amplitude range, wherein the first preset value is equal to an amplitude of a to-be-processed signal that is generated when the amplitude of the input signal is the minimum value of the preset amplitude range, and the second preset value is equal to an amplitude of a to-be-processed signal that is generated when the amplitude of the input signal is the maximum value of the preset amplitude range;

wherein the polynomial operation circuit is configured to generate, according to the amplitude of the to-be-processed signal output by the amplitude limiting circuit, a value of each order of computation term whose order is not higher than a preset order; and

wherein the weighting circuit is configured to receive the value of each order of computation term and generate an output signal of the segmentation processing circuit according to a coefficient that is of each order of computation term and that is in weighting coefficients and according to the value of each order of computation term.

6. The curve fitting circuit according to claim 5, wherein the amplitude limiting circuit comprises a pre-adjustment circuit and an amplitude limiting amplifier circuit;

wherein the pre-adjustment circuit is configured to receive an input signal and output a signal obtained by amplifying the input signal and/or performing offset adjustment on the input signal; and

wherein the amplitude limiting amplifier circuit is configured to;

receive the signal output by the pre-adjustment circuit; and

generate and output, when an amplitude of the signal output by the pre-adjustment circuit is within an amplitude limiting range of the amplitude limiting amplifier circuit, a to-be-processed signal whose amplitude monotonically varies according to the amplitude of the signal output by the pre-adjustment circuit, or output the first preset value when the amplitude of the signal output by the pre-adjustment circuit is less than a minimum value of the amplitude limiting range of the amplitude limiting amplifier circuit, or output the second preset value when the amplitude of the signal output by the pre-adjustment circuit is greater than a maximum value of the amplitude limiting range of the amplitude limiting amplifier circuit;

wherein a mapping relationship between the amplitude limiting range of the amplitude limiting amplifier circuit and the preset amplitude range of the segmentation processing circuit at which the amplitude limiting amplifier circuit is located is the same as a mapping relationship between the input signal received by the pre-adjustment circuit and the signal output by the pre-adjustment circuit.

7. The curve fitting circuit according to claim 6, wherein the amplitude limiting amplifier circuit comprises a first triode, a second triode, a third triode, a fourth triode, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor;

wherein one end of the first resistor is configured to receive an amplitude-limited signal, the other end of the first resistor is separately connected to a collector of the first triode, a base of the first triode, and a base of the second triode, wherein an emitter of the first triode is configured to be grounded by using the second resistor, an emitter of the second triode is configured to be grounded by using the third resistor, and a collector of the second triode is configured to output a signal related to an amplitude of the amplitude-limited signal;

wherein a base of the third triode is configured to receive a first input signal, a base of the fourth triode is configured to receive a second input signal, a collector of the third triode is connected to a collector of the fourth triode by sequentially using the fourth resistor and the fifth resistor, an emitter of the third triode is connected to an emitter of the fourth triode by sequentially using the sixth resistor and the seventh resistor, an end on which the sixth resistor is connected to the seventh resistor is configured to receive the signal related to the amplitude of the amplitude-limited signal, a signal on an end on which the fourth resistor is connected to the collector of the third triode is one channel of signal in two channels of signals configured to be output by the amplitude limiting amplifier circuit, and a signal on an end on which the fifth resistor is connected to the collector of the fourth triode is the other channel of signal in the two channels of signals output by the amplitude limiting amplifier circuit;

wherein a difference between the first input signal and the second input signal is equal to the signal output by the pre-adjustment circuit, and a difference between the two channels of signals output by the amplitude limiting amplifier circuit is the to-be-processed signal output by the amplitude limiting circuit at which the amplitude limiting amplifier circuit is located.

8. The curve fitting circuit according to claim 5, wherein the preset order is m, the polynomial operation circuit comprises m−

1 multipliers, and one input end of each multiplier receives a signal output by the amplitude limiting circuit in the segmentation processing circuit at which the polynomial operation circuit is located; and

wherein the other input end of a first multiplier receives the signal output by the amplitude limiting circuit in the segmentation processing circuit at which the polynomial operation circuit is located, and the other input end of an l^th multiplier receives a signal output by an (l−

1)^th multiplier, wherein l=2, . . . , m; and

a signal output by a p^th multiplier is the (p+1)^th power of the signal output by the amplitude limiting circuit in the segmentation processing circuit at which the polynomial operation circuit is located, wherein p=1, . . . , m−

1.

9. The curve fitting circuit according to claim 5, wherein the preset order is m, and the weighting circuit comprises n*m multipliers and n second adder circuits, wherein the n*m multipliers are divided into n groups, each group has m multipliers, and n is a natural number;

wherein one input end of each multiplier in a k^th group receives one of values that are of orders of computation terms and that are output by the polynomial operation circuit;

wherein when one input end of a multiplier in the k^th group receives a value that is of an l^th order of computation term and that is output by the polynomial operation circuit, and the other input end of the multiplier receives a coefficient that is of the l^th order of computation term and that is in a k^th group of coefficients in the weighting coefficients, wherein k=1, n, and l is a natural number not greater than m; and

wherein each second adder circuit outputs a signal obtained by adding signals output by multipliers in a group, and uses the signal as one output signal of the segmentation processing circuit at which the weighting circuit is located.

10. An analog predistorter, comprising a curve fitting circuit, the curve fitting circuit comprising:

n segmentation processing circuits, wherein n is greater than or equal to 2; and

q first adder circuits, wherein q is a natural number;

wherein each segmentation processing circuit of the n segmentation processing circuits is configured to;

receive an input signal;

intercept a part of the input signal according to a preset rule;

generate a to-be-processed signal according to the intercepted part; and

generate q output signals according to the to-be-processed signal using a polynomial fitting method, wherein parts of the input signal intercepted by different segmentation processing circuits are not exactly the same; and

wherein each first adder circuit is configured to;

receive one signal in the q output signals of each segmentation processing circuit; and

obtain one output signal of the curve fitting circuit according to a sum of received n signals, wherein different first adder circuits receive different output signals in q output signals of a same segmentation processing circuit.

11. The analog predistorter according to claim 10, wherein obtaining the one output signal of the curve fitting circuit according to the sum of received n signals comprises:

when none of the received q output signals of each segmentation processing circuit comprise a constant term, use a signal, obtained by adding the sum of the received n signals to a constant term, as the one output signal of the curve fitting circuit;

or

when q output signals of at least one segmentation processing circuit comprise a constant term, use the sum of the received n signals as the one output signal of the curve fitting circuit.

12. The analog predistorter according to claim 11, wherein intercepting a part of the input signal according to a preset rule comprises:

determining the intercepted part according to an amplitude of the input signal and a preset amplitude range of the segmentation processing circuit.

13. The analog predistorter according to claim 11, wherein intercepting a part of the input signal according to a preset rule comprises:

intercepting a part between two points of the input signal.

14. A radio frequency signal transmitter, comprising a curve fitting circuit, the curve fitting circuit comprising:

n segmentation processing circuits, wherein n is greater than or equal to 2; and

q first adder circuits, wherein q is a natural number;

wherein each segmentation processing circuit of the n segmentation processing circuits is configured to;

receive an input signal;

intercept a part of the input signal according to a preset rule;

generate a to-be-processed signal according to the intercepted part; and

generate q output signals according to the to-be-processed signal using a polynomial fitting method, wherein parts of the input signal intercepted by different segmentation processing circuits are not exactly the same; and

wherein each first adder circuit is configured to;

receive one signal in the q output signals of each segmentation processing circuit; and

obtain one output signal of the curve fitting circuit according to a sum of received n signals, wherein different first adder circuits receive different output signals in q output signals of a same segmentation processing circuit.

15. The radio frequency signal transmitter according to claim 14, wherein obtaining the one output signal of the curve fitting circuit according to the sum of received n signals comprises:

when none of the received q output signals of each segmentation processing circuit comprise a constant term, use a signal, obtained by adding the sum of the received n signals to a constant term, as the one output signal of the curve fitting circuit;

or

when q output signals of at least one segmentation processing circuit comprise a constant term, use the sum of the received n signals as the one output signal of the curve fitting circuit.

16. The radio frequency signal transmitter according to claim 14, wherein intercepting a part of the input signal according to a preset rule comprises:

determining the intercepted part according to an amplitude of the input signal and a preset amplitude range of the segmentation processing circuit.

17. The radio frequency signal transmitter according to claim 14, wherein intercepting a part of the input signal according to a preset rule comprises:

intercepting a part between two points of the input signal.