Simulation design test method for dynamic EVM (Error Vector Magnitude) of high-linearity PA

Abstract

The invention provides a high-linearity PA dynamic EVM simulation design test method. The method is characterized by comprising the following steps: step (1), establishing a time domain transient response simulation platform and obtaining consistency with a test result; and step (2), converting the power into a voltage amplitude, and then determining a DEVM (Digital Error Vector Magnitude) index. According to the method, expensive special test equipment (DEVM vector signal analyzer) is not used, and the dynamic EVM can be tested and evaluated by using an oscilloscope with certain precision; the problem that the DEVM is difficult to evaluate in the design simulation and test stages of the power amplifier is solved.

Description

Technical Field

[0001] The present invention relates to the field of circuit testing, and in particular to a simulation design testing method for high linear PA dynamic EVM. Background Art

[0002] DEVM is the dynamic vector magnitude error. The typical static EVM analysis platform architecture is as follows: Figure 1 As shown in the figure, the static EVM analysis of PA circuit is mainly carried out under the condition of frequency domain. The simulation analysis method of dynamic EVM index under frequency domain setting has not been reported yet. In addition, in the actual PA test, the dynamic EVM index test under frequency domain setting still needs to upgrade other software / hardware before the PA bias circuit can be quickly cycled (Duty Cycle ON-OFF) to determine the dynamic linearity of PA.

[0003] In static EVM simulation and testing, the PA is in a continuous working state (PA_EN Duty = 100%), and the simulated static EVM index and the actual measured index have good consistency (correlation). However, in the actual application of PA chips, in order to make more efficient use of electrical energy, the PA is only turned on when it is in the transmitting state and is turned off at other times (so that PA_EN Duty < 100%), and the switching process of transceiver is completed in a very short time, so it is required that the PA must ensure that the original EVM power remains unchanged when switching between fast on and off (i.e. dynamic EVM or DEVM). However, the PA design under the typical frequency domain setting does not have such evaluation conditions, resulting in most PA chips failing to pass the DEVM index in future tests. On the other hand, since the dynamic EVM test requires the synchronization of the receiving end and the pulse switching signal, the implementation of the test system is relatively difficult, so the dedicated DEVM test equipment is expensive. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a simulation design and testing method for high linear PA dynamic EVM to solve the problems raised in the above background technology.

[0005] The technical problem solved by the present invention is achieved by adopting the following technical solution: a simulation design and test method for high linear PA dynamic EVM, comprising the following steps:

[0006] Step (1). Establish a time domain transient response simulation platform and obtain consistency with the test results (correlation)

[0007] Step (2). Determine the DEVM index after converting the power into voltage amplitude;

[0008] The specific implementation of step (2) is mainly as follows:

[0009] When the PA Gain Imbalance is 0.3dB, the EVM is 1.8%, which requires that in the transient response, the difference between the power values ​​P1 (dBm) and P2 (dBm) at any two points is within 0.3dB;

[0010] The voltage values ​​of Vp1(V) and Vp2(V) at points P1 and P2 can be measured on an oscilloscope, so the power values ​​at points P1 and P2 can be calculated. Then, based on the basic formula of peak voltage and power, P1(W) and P2(W) can be derived:

[0011]

[0012] According to the conversion formula of P(dBm)=10log(P(W)), it can be calculated by the following formula:

[0013] ∵10log(P1)-10log(P2)≤0.3

[0014]

[0015] Therefore, the ratio of the voltage amplitude between any two points of the time domain transient response waveform output by the PA is:

[0016] When 0.966≤Vp1 / Vp2≤1.035, its EVM≤1.8%.

[0017] Compared with the prior art, the beneficial effects of the present invention are: the present invention eliminates the need for expensive dedicated test equipment (DEVM vector signal analyzer), and can test and evaluate dynamic EVM with an oscilloscope of a certain accuracy; it solves the problem of difficulty in evaluating DEVM in the design simulation and testing stages of power amplifiers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of a typical static EVM analysis platform architecture of the present invention.

[0019] Figure 2 It is a schematic diagram of the corresponding relationship between AM / AM, AM / PM and EVM of the present invention.

[0020] Figure 3 It is a schematic diagram of the time domain transient response simulation results of the present invention.

[0021] Figure 4 It is a schematic diagram of the time domain transient response simulation and test framework of the present invention.

[0022] Figure 5 It is a schematic diagram of gain compression and AM and AM / AM distortion caused by overexcitation of the present invention.

[0023] Figure 6 It is a schematic diagram for comparing the consistency between the time-domain transient response simulation and the actual test of the present invention.

[0024] Figure 7 It is a schematic diagram of the DEVM indicator in the stable state of the time domain waveform of the present invention.

[0025] Figure 8 It is a schematic diagram of AM / AM in a stable state of the time domain waveform of the present invention. DETAILED DESCRIPTION

[0026] In order to make the technical means for realizing the present invention, the creative features, the objectives and effects to be achieved easy to understand, the present invention is further explained below in conjunction with specific diagrams. In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection, or an integral connection can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be internal communication between two elements.

[0027] like Figures 1 to 8 As shown, a simulation design and test method for high linear PA dynamic EVM includes the following steps:

[0028] Step (1). Establish a time domain transient response simulation platform and obtain consistency with the test results (correlation)

[0029] Step (2). A method for determining the DEVM index after converting the power into a voltage amplitude.

[0030] The specific implementation of step (2) is as follows: the IEEE Standards Association formulates the conversion relationship between AM distortion and EVM as follows: Figure 3 As shown,

[0031] according to Figure 3 When the PA Gain Imbalance is 0.3dB, the EVM is 1.8%. This requires that in the transient response, the difference between the power values ​​P1 (dBm) and P2 (dBm) at any two points is within 0.3dB. The voltage values ​​of Vp1 (V) and Vp2 (V) at points P1 and P2 can be measured on the oscilloscope, so the power values ​​at points P1 and P2 can be calculated, and then P1 (W) and P2 (W) can be derived based on the basic formula of peak voltage and power:

[0032]

[0033] According to the conversion formula of P(dBm)=10log(P(W)), it can be calculated by the following formula:

[0034] ∵10log(P1)-10log(P2)≤0.3

[0035]

[0036] Therefore, the ratio of the voltage amplitude between any two points of the time domain transient response waveform output by the PA is:

[0037] When 0.966≤Vp1 / Vp2≤1.035, its EVM≤1.8%.

[0038] Based on this theoretical foundation, a time-domain transient simulation platform is established to analyze whether the DEVM meets the specifications. Figure 3 The output waveform of each stage of PA is simulated by using time domain transient response. It can be observed that the AM distortion generated by PA_EN switching in different cycles can be truly analyzed through the time domain transient response simulation platform, which leads to failure to pass the dynamic EVM test. Figure 3 From the first-stage transient simulation current waveform shown, it can be seen that the PA needs a slow period of time for the current to reach a stable state at the moment of turning on. Because there is a signal input at any time during the entire cycle, the gain slowly decreases as the current slowly rises. The gain changes while keeping the input power unchanged, resulting in AM distortion.

[0039] The new architecture of the time domain transient test platform is used to test the unqualified dynamic EVM. When the PA enable terminal is switched at a certain period, it can be found that its starting voltage has an overshoot phenomenon (Overshoot) in the initial rise time, which causes AM / AM distortion. Figure 5 As shown. We define a coefficient K that characterizes the degree of change of the time domain voltage waveform, namely the fluctuation coefficient. The fluctuation coefficient is the ratio of the voltage values ​​of any two points on the time domain waveform when the PA is turned on. m5=1.157v,m4=1.338v,K=m5 / m4=0.865, the fluctuation coefficient of 0.865 is not within the requirements mentioned above Within, that is, EVM>1.8%, so the DEVM indicator cannot be tested.

[0040] After the PA is optimized through debugging, the time domain waveform when switching on is smooth and fast rising and reaches a stable state. Figure 6 As shown in the figure, the waveform basically reaches a stable state 1us after the PA is turned on. At this time, the fluctuation coefficient K≈1. The DEVM index at this time is as follows: Figure 7 As shown in the figure, by debugging and optimizing the time domain transient response waveform becomes stable, and the DEVM power curve that cannot be measured is changed into a DEVM power curve that can be quantitatively analyzed. Figure 8It can also be seen from the AM / AM distortion curve of the PA that it has been improved and optimized.

[0041] like Figure 6 As shown in the time domain transient response test method, it can be observed that when the waveform amplitude changes less during a certain voltage rise stage, the AM distortion is also smaller. Figure 7 The converted DEVM power curve shown can meet the specification of DEVM<=1.8% under a certain output power. The present invention converts AM distortion into EVM index, and thus obtains the EVM index under time domain transient response, which is the final DEVM index.

[0042] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A simulation design and test method for high linear PA dynamic EVM, characterized by: The following steps are involved: Step (1). Establish a time domain transient response simulation platform and obtain consistency with the test results; Step (2): Determine the DEVM index after converting the power into voltage amplitude.

2. The simulation design and testing method of a high linear PA dynamic EVM according to claim 1, characterized in that: The specific implementation of step (2) is mainly as follows: When the PA Gain Imbalance is 0.3dB, the EVM is 1.8%, which requires that in the transient response, the difference between the power values ​​P1 (dBm) and P2 (dBm) at any two points is within 0.3dB; The voltage values ​​of Vp1(V) and Vp2(V) at points P1 and P2 can be measured on an oscilloscope, so the power values ​​at points P1 and P2 can be calculated. Then, based on the basic formula of peak voltage and power, P1(W) and P2(W) can be derived: According to the conversion formula of P(dBm)=10log(P(W)), it can be calculated by the following formula: ∵10log(P1)-10log(P2)≤0.3 ∴ ∴ Therefore, the ratio of the voltage amplitude between any two points of the time domain transient response waveform output by the PA is: When 0.966≤Vp1 / Vp2≤1.035, its EVM≤1.8%.

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