Pulse distortion correction method for multi-level phase-shifting full-digital transmitter

Abstract

The invention discloses a pulse distortion correction method for a multi-level phase-shifting all-digital transmitter, and relates to the field of all-digital transmitters, and the method comprises the steps: determining a relational expression between a total time delay error and a phase-shifting control word; determining an integral multiple error relationship between the total time delay error and the phase shift control word based on a relational expression between the total time delay error and the phase shift control word; calculating a preprocessed phase shift control word according to an integral multiple error relation between the total time delay error and the phase shift control word; calculating a compensation control word according to the total duty ratio change error and the preprocessed phase shift control word; controlling the delay amount of the carrier signal according to the compensation control word to obtain a carrier signal with a duty ratio change error; generating a corrected carrier signal based on the carrier signal with the duty cycle change error; and performing delay processing on the corrected carrier signal according to the pre-processing phase shift control word, and performing amplification synthesis on the output signal. According to the invention, adaptive correction processing of pulse waveform distortion can be realized, and the linear performance of ADTx is improved.

Description

Technical Field

[0001] The present application relates to the field of all-digital transmitters, and in particular to a method for correcting pulse distortion of a multi-level phase-shifted all-digital transmitter. Background Art

[0002] With the rapid growth of communication service demand, the widespread application of complex modulation methods, the continuous improvement of signal rate and bandwidth, the continuous improvement of multi-mode and multi-band requirements for hardware equipment, and the green communication concept represented by low power consumption have become the development trend and goal of wireless communication technology. For the transmitter, it is necessary to process signals with larger bandwidth and higher peak-to-average ratio, as well as requirements such as higher reconfigurability and compatibility, which puts tremendous pressure on the design and implementation of traditional transmitters. On the other hand, as a revolutionary technology, the All-Digital Transmitter (ADTx) is different from the traditional transmitter system in terms of system and mechanism. It has technical advantages such as high efficiency, high linearity, flexible reconfigurability and programmability, and is expected to play an important role in future wireless communication systems.

[0003] In recent years, ADTx technology has developed rapidly, and a variety of technical architectures have emerged, represented by orthogonal ADTx, polarization ADTx and outphasing ADTx. Among them, the phase-shifting architecture ADTx solution based on radio frequency pulse width modulation technology (RF-PWM) combined with digital delay lines (Digital Delay Lines, DDL) technology has significant advantages in terms of system complexity, time resolution and processing power consumption. However, the pulse signal will experience waveform distortion. The main reason is that due to the non-ideality of the device, the rise and fall time of the pulse signal will increase significantly after the pulse signal passes through the digital delay line circuit and the switching power amplifier circuit, resulting in a change in the duty cycle of the pulse waveform. At the same time, due to the differences in distortion between multiple pulse signals, the multiple signals will no longer be synchronized, introducing a delay mismatch error. Pulse waveform distortion affects ADTx performance in the following ways: Since the performance of the RF-PWM algorithm is directly related to the width and position of the pulse signal, duty cycle error will deteriorate harmonic performance, generate additional even harmonics, and increase filtering difficulty; while delay mismatch error will cause serious nonlinear distortion of in-band signals. However, traditional linearization methods such as digital pre-distortion are difficult to directly apply to correct the above distortion phenomena. Summary of the invention

[0004] The purpose of this application is to provide a method for correcting pulse distortion of a multi-level phase-shifted all-digital transmitter, which can realize adaptive correction processing of pulse waveform distortion and improve the linear performance of ADTx.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] The present application provides a multi-level phase-shifted all-digital transmitter pulse distortion correction method, the method is applied to a multi-level phase-shifted all-digital transmitter pulse distortion correction system, the multi-level phase-shifted all-digital transmitter pulse distortion correction system comprises: a digital signal processing unit, a delay preprocessing unit, a clock compensation unit, a phase modulation unit and a digital power amplifier; the method comprises:

[0007] Determine the relationship between the total delay error and the phase shift control word; the total delay error includes the delay error of the digital delay line circuit in the phase modulation unit and the delay error of the digital power amplifier; the phase shift control word is calculated by the digital signal processing unit based on the baseband signal using the RF-PWM algorithm;

[0008] Determine the integer multiple error relationship between the total delay error and the phase shift control word based on the relationship between the total delay error and the phase shift control word;

[0009] Calculate the preprocessing phase shift control word according to the integer multiple error relationship between the total delay error and the phase shift control word;

[0010] Calculating a compensation control word according to a total duty cycle variation error and a preprocessed phase shift control word; the total duty cycle variation error includes a duty cycle variation error of a digital delay line circuit in a phase modulation unit and a duty cycle variation error of a digital power amplifier;

[0011] Controlling the delay of the carrier signal according to the compensation control word to obtain a carrier signal with a duty cycle variation error;

[0012] generating a correction carrier signal based on the carrier signal with a duty cycle variation error;

[0013] The correction carrier signal is delayed according to the pre-processing phase-shift control word, and the output signal is amplified and synthesized.

[0014] According to the specific embodiments provided in this application, this application has the following technical effects:

[0015] The present application provides a method for correcting pulse distortion of a multi-level phase-shifted all-digital transmitter. The method calculates a pre-processed phase-shift control word based on the integer multiple error relationship between the total time delay error and the phase-shift control word, and can correct the time delay error caused by pulse waveform distortion; calculates a compensation control word based on the pre-processed phase-shift control word, and determines a correction carrier signal based on the compensation control word, and can compensate for the pulse waveform distortion error caused by the digital delay line circuit and the digital power amplifier in the phase modulation unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 The schematic diagram of the architecture of a five-level phase-shifted all-digital transmitter based on DDL;

[0018] Figure 2 A schematic diagram of the structure of a multi-level phase-shifted all-digital transmitter pulse distortion correction system provided in one embodiment of the present application;

[0019] Figure 3 It is a schematic diagram of the detailed functional modules of the clock compensation unit;

[0020] Figure 4 A flowchart of a pulse distortion correction method for a multi-level phase-shifted all-digital transmitter provided in an embodiment of the present application;

[0021] Figure 5 A schematic diagram of pulse waveforms at various stages in a clock compensation unit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0023] Figure 1 The figure is a schematic diagram of the architecture of a five-level phase-shifted all-digital transmitter based on DDL. It contains three functional units. First, the signal processing unit calculates four phase-shift control words based on the input baseband signal based on the RF-PWM algorithm and sends them to the phase modulation unit; the phase modulation unit is composed of four DDL circuits, which delay the input pulse signal according to the phase-shift control word, thereby realizing the modulation and up-conversion of the amplitude and phase information of the baseband signal; amplification and synthesis are achieved through the digital power amplifier (DPA), and a 5-level pulse modulation signal is output. However, in the actual circuit, the waveform distortion phenomenon will occur after the pulse signal passes through the above units.

[0024] The purpose of the present application is to provide a multi-level phase-shifted all-digital transmitter pulse distortion correction method with even-order harmonic elimination function, so as to realize adaptive correction processing function of pulse waveform distortion and improve the linear performance of output signal.

[0025] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0026] In an exemplary embodiment, a method for correcting pulse distortion of a multi-level phase-shifted all-digital transmitter is provided, wherein the method is applied to Figure 2 Pulse distortion correction system of multi-level phase-shifted all-digital transmitter in.

[0027] like Figure 2 As shown, the multi-level phase-shifted all-digital transmitter pulse distortion correction system includes: a digital signal processing unit, a delay preprocessing unit, a clock compensation unit, a phase modulation unit and a digital power amplifier. Figure 3 As shown, the clock compensation unit specifically includes a signal source, a digital delay line circuit and an inverter which are connected in sequence.

[0028] The carrier signal S with a 50% duty cycle is generated by the signal source sq (t), and input to the DDL circuit in the clock compensation unit to compensate the control word (W CON_i (t)) modulates the phase information to the clock signal to generate an output pulse signal S with duty cycle distortion error DCE (t), a pulse train S with a specific width and compensation characteristics is generated through an inverter CON (t) (i.e., corrected carrier signal).

[0029] The present application decomposes the pulse waveform distortion error of the all-digital transmitter into a delay error and a pulse width error. On the basis of the existing all-digital transmitter architecture, a delay preprocessing unit and a clock compensation unit are added to compensate for the delay error and the pulse width error respectively. First, the delay error caused by the pulse waveform distortion is corrected by the delay preprocessing unit, and the delay error can be offset by adding the corresponding delay error to the delay line control word data of each channel in the phase modulation unit. Then, the clock signal of the DDL circuit in the phase modulation unit is replaced with a specific width two-level signal (i.e., a correction carrier signal) output by the clock compensation unit. The correction carrier signal output by the clock compensation unit is used as the carrier signal of the DDL circuit in the phase modulation unit, which can compensate for the pulse waveform distortion error caused by the DDL circuit.

[0030] like Figure 4 As shown, the pulse distortion correction method of the multi-level phase-shifted all-digital transmitter includes the following steps:

[0031] S1: Determine the relationship between the total delay error and the phase shift control word; the total delay error includes the delay error of the digital delay line circuit in the phase modulation unit and the delay error of the digital power amplifier; the phase shift control word is calculated by the digital signal processing unit based on the baseband signal using the RF-PWM algorithm.

[0032] In a specific embodiment, step S1 specifically includes:

[0033] S11: Measure the influence of the digital delay line circuit in the phase modulation unit on the pulse waveform distortion, and determine the delay error of the digital delay line circuit in the phase modulation unit.

[0034] Measure the influence of components in the DDL circuit on the pulse waveform distortion when the pulse signal passes through the phase modulation unit. The delay error of DDL is Δδ. ddl (t). Δδ ddl (t) is linearly increasing with the phase shift control word W(t). When W(t) is the maximum, Δδ ddl (t) = δ, δ is the maximum delay error.

[0035] S12: Measure the impact of components in the digital power amplifier on pulse waveform distortion and determine the delay error of the digital power amplifier.

[0036] The actual measurement of the influence of components in DPA on pulse waveform distortion, the delay error of DPA is δ dpa , δ dpa is a constant, and the delay error in the DPA is converted into the corresponding phase shift control word value W dpa , the delay error δ of DPA dpa The relationship between the phase shift control word W(t) is: dpa =round((δ dpa / δ)W max (t)), W max (t) is the maximum phase shift control word.

[0037] S13: Determine a relationship between a total delay error and a phase shift control word based on a linear relationship between a delay error of a digital delay line circuit in a phase modulation unit and a phase shift control word and a relationship between a delay error of a digital power amplifier and a phase shift control word.

[0038] Establish the relationship between the total delay error Δδ(t) and the phase shift control word:

[0039] Δδ(t)=δ((W(t)+W dpa ) / W max (t)).

[0040] S2: Determine the integer multiple error relationship between the total time delay error and the phase shift control word based on the relationship formula between the total time delay error and the phase shift control word.

[0041] Calculate the integer multiple error (N) relationship between the total time delay error and the phase shift control word:

[0042] When 0 < Δδ(t) < 1, -W dpa <W(t) < W max (t) / δ - W dpa ;

[0043] When 1 < Δδ(t) < 2, W max (t) / δ - W dpa <W(t) < 2W max (t) / δ - W dpa ;

[0044] When 2 < Δδ(t) < 3, 2W max (t) / δ - W dpa <W(t) < 3W max (t) / δ - W dpa ;

[0045]

[0046] When N < Δδ(t) < N + 1, N·W max (t) / δ - W dpa <W(t) < (N + 1)·W max (t) / δ - W dpa .

[0047] S3: Calculate the preprocessed phase shift control word according to the integer multiple error relationship between the total time delay error and the phase shift control word.

[0048] The calculation formula for the preprocessed phase shift control word W i ′(t) is: W i ′(t) = W(t) + N, i ∈ [1, 4], where i is the number of channels of the digital delay line circuit.

[0049] The preprocessing of the phase shift control word can realize the correction processing of the time delay error caused by the pulse waveform distortion in the multi-level RF-PWM all-digital transmitter.

[0050] S4: Calculate the compensation control word according to the total duty cycle change error and the preprocessed phase shift control word; the total duty cycle change error includes the duty cycle change error of the digital delay line circuit in the phase modulation unit and the duty cycle change error of the digital power amplifier.

[0051] In a specific embodiment, the influence of components in the DPA on the pulse waveform distortion is actually measured, and the duty cycle variation error of the DPA is denoted as τ dpa , τ dpa Is a constant.

[0052] Measure the influence of components in the DDL circuit of the phase modulation unit on the pulse waveform distortion, and record the duty cycle variation error of DDL as Δτ ddl (t), Δτ ddl (t) is linearly increasing with the phase shift control word W(t). When W(t) is the largest, Δτ ddl (t) = τ, τ is the maximum duty cycle variation error.

[0053] Calculate the total duty cycle variation error Δτ(t) caused by the DDL circuit and DPA of the phase modulation unit: Δτ(t) = Δτ ddl (t)+τ dpa , Δτ(t) and the phase shift control word W(t) are linearly increasing.

[0054] Calculate the compensation control word W in the clock compensation unit CON_i (t):

[0055] W CON_i (t) = W i (t)+round((Δτ ddl (t)+τ dpa ) / τ)

[0056] The pulse waveform distortion Δτ caused by the DDL circuit in the phase modulation unit ddl (t) The above delay error is linearly increasing with the phase shift control word W(t), so W CON_i (t) = W i ′(t)+round(τ dpa / τ).

[0057] S5: Control the delay amount of the carrier signal according to the compensation control word to obtain a carrier signal with a duty cycle variation error.

[0058] W CON_i (t) Control the delay of the clock carrier signal in the clock compensation unit to obtain a carrier signal S with a duty cycle variation error DCE_i (t), such as Figure 5 As shown in (a) in .

[0059] S6: Generate a correction carrier signal based on the carrier signal with duty cycle variation error.

[0060] S DCE_i (t) is generated after passing through the inverter in the clock compensation unit and S DCE_i(t) Corrected carrier signal S with opposite distortion CON_i (t), such as Figure 5 As shown in (b) in .

[0061] S7: Delay processing is performed on the correction carrier signal according to the pre-processing phase shift control word, and the output signal is amplified and synthesized.

[0062] S CON_i (t) is used as the input carrier clock of the DDL circuit in the phase modulator. The two are cascaded to produce an ideal two-level signal S i (t), such as Figure 5 As shown in (c) in .

[0063] The clock compensation unit can be used to correct the duty cycle distortion error caused by pulse waveform distortion in a multi-level RF-PWM full digital transmitter.

[0064] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for correcting pulse distortion of a multi-level phase-shifted all-digital transmitter, characterized in that: The method is applied to a multi-level phase-shifted all-digital transmitter pulse distortion correction system, the multi-level phase-shifted all-digital transmitter pulse distortion correction system comprising: a digital signal processing unit, a delay preprocessing unit, a clock compensation unit, a phase modulation unit and a digital power amplifier; the method comprises: Determine the relationship between the total delay error and the phase shift control word; the total delay error includes the delay error of the digital delay line circuit in the phase modulation unit and the delay error of the digital power amplifier; the phase shift control word is calculated by the digital signal processing unit based on the baseband signal using the RF-PWM algorithm; Determine the integer multiple error relationship between the total delay error and the phase shift control word based on the relationship between the total delay error and the phase shift control word; Calculate the preprocessing phase shift control word according to the integer multiple error relationship between the total delay error and the phase shift control word; Calculating a compensation control word according to a total duty cycle variation error and a preprocessed phase shift control word; the total duty cycle variation error includes a duty cycle variation error of a digital delay line circuit in a phase modulation unit and a duty cycle variation error of a digital power amplifier; Controlling the delay of the carrier signal according to the compensation control word to obtain a carrier signal with a duty cycle variation error; generating a correction carrier signal based on the carrier signal with a duty cycle variation error; The correction carrier signal is delayed according to the pre-processing phase-shift control word, and the output signal is amplified and synthesized.

2. The pulse distortion correction method of a multi-level phase-shifted all-digital transmitter according to claim 1 is characterized in that: Determine the relationship between the total delay error and the phase shift control word, specifically including: Measuring the influence of the digital delay line circuit in the phase modulation unit on the pulse waveform distortion and determining the time delay error of the digital delay line circuit in the phase modulation unit; Measure the impact of components in digital power amplifiers on pulse waveform distortion and determine the delay error of digital power amplifiers; Based on the linear relationship between the delay error of the digital delay line circuit in the phase modulation unit and the phase shift control word and the relationship between the delay error of the digital power amplifier and the phase shift control word, the relationship between the total delay error and the phase shift control word is determined.

3. The pulse distortion correction method of a multi-level phase-shifted all-digital transmitter according to claim 2 is characterized in that: The relationship between the delay error of the digital power amplifier and the phase shift control word is: W dpa =round((δ dpa / δ)W max (t)) Among them, W dpa The phase shift control word value converted from the delay error of the digital power amplifier, δ dpa is the delay error of the digital power amplifier, δ is the maximum delay error, W max (t) is the maximum phase shift control word.

4. The multi-level phase-shifted all-digital transmitter pulse distortion correction system according to claim 3 is characterized in that: The relationship between the total delay error and the phase shift control word is: Δδ(t)=δ((W(t)+W dpa ) / W max (t)) Among them, Δδ(t) is the total delay error.

5. The pulse distortion correction method of a multi-level phase-shifted all-digital transmitter according to claim 4 is characterized in that: The integer multiple error relationship between the total delay error and the phase shift control word is as follows: When 0 < Δδ(t) < 1, -W dpa <W(t) < W max (t) / δ - W dpa When 1 < Δδ(t) < 2, W max (t) / δ - W dpa < W(t) < 2W max (t) / δ - W dpa When 2 < Δδ(t) < 3, 2W max (t) / δ - W dpa < W(t) < 3W max (t) / δ - W dpa When N < Δδ(t) < N + 1, N·W max (t) / δ - W dpa <W(t) < (N + 1)·W max (t) / δ - W dpa Wherein, W(t) is the phase shift control word, and N is the integer multiple error.

6. The pulse distortion correction method of a multi-level phase-shifted all-digital transmitter according to claim 5, characterized in that: The calculation formula of the preprocessing phase shift control word is: W i ′(t)=W(t)+N,i∈[1,4] Among them, W i ′(t) is the preprocessing phase shift control word, and i is the number of channels of the digital delay line circuit.

7. The pulse distortion correction method of a multi-level phase-shifted all-digital transmitter according to claim 1 is characterized in that: Before calculating the compensation control word according to the total duty cycle variation error and the preprocessed phase shift control word, it also includes: Measuring the influence of the digital delay line circuit in the phase modulation unit on the pulse waveform distortion and determining the duty cycle variation error of the digital delay line circuit in the phase modulation unit; Measure the impact of components in digital power amplifiers on pulse waveform distortion and determine the duty cycle variation error of digital power amplifiers; A total duty cycle variation error is calculated based on a duty cycle variation error of a digital delay line circuit in a phase modulation unit and a duty cycle variation error of a digital power amplifier.

8. The pulse distortion correction method for a multi-level phase-shifted all-digital transmitter according to claim 1 is characterized in that: The calculation formula of the compensation control word is: W CON_i (t)=W i ′(t)+round(τ dpa / t) Among them, W CON_i (t) is the compensation control word, W i ′(t) is the preprocessing phase shift control word, τ dpa is the duty cycle variation error of the digital delay line circuit in the phase modulation unit, and τ is the maximum duty cycle variation error.

Images