Harmonic enhanced load traction system

Abstract

The invention provides a harmonic enhancement type load traction system. The harmonic enhancement type load traction system comprises a circulator, an impedance tuner, a high-pass filter, a radio frequency power amplifier and a non-reflection duplexer which are connected end to end to form a closed-loop structure, the input end of the circulator is connected with a bias structure of a to-be-tested device, and the non-reflection duplexer is connected with a fundamental wave signal to form an open-loop structure; the active closed-loop load traction structure is used at the harmonic wave position, the active open-loop load traction structure is used at the fundamental wave position, tuning of the fundamental wave and tuning of the second harmonic wave are effectively compatible, the integration level is high, and impedance tuning of the harmonic wave can be achieved under the condition that other equipment such as a signal source is not introduced.

Description

Technical Field

[0001] The present invention relates to the field of power amplifier design, and in particular to a harmonic enhanced load-pull system. Background Art

[0002] With the development of modern communication technology, power amplifiers, as core components in the field of RF communication, have put forward higher requirements on indicators such as efficiency and gain. Load pulling has been proven to be an effective way to improve these indicators, providing a means for the device under test (DUT) to present a non-50Ω environment and measure its performance. This provides designers with the information they need to design matching networks to obtain the best performance of the DUT, and has been successfully proven to reduce design risks and save time in the product design cycle.

[0003] Due to the low cost and good power handling capability brought by the relatively simple structure, passive load-pull technology is currently widely used in the market. It is a combination of a central conductor and a tuning probe. By changing the relative position between the central conductor and the ground wire, arbitrary impedance is generated to achieve load modulation. However, due to its own structural defects, passive load-pull cannot be applied to fields such as broadband impedance matching and harmonic matching. Therefore, active load-pull technology was proposed. Due to its larger tuning range than passive load-pull, it has been widely used in the characterization of microwave devices. According to different structures, it can be divided into two types: closed-loop active load-pull and open-loop active load-pull. Figure 1 shown.

[0004] Passive load traction is prone to wear and tear due to its mechanical structure, which causes system loss and greatly reduces the calibration accuracy of the system. At the same time, since no active components are used, it is impossible to synthesize a high reflection coefficient and cover the edge of the Smith chart, making it difficult to apply to harmonic load traction. Active load traction has an incomparable speed advantage over passive load traction. However, its two mainstream solutions, closed-loop and open-loop active load traction, both require high-gain and high-linearity amplifiers to ensure high accuracy and a wide tuning range of the system. This greatly increases the cost of the system. At the same time, the former has a higher test throughput, but there is a risk of self-excitation, which may burn out the device, while the latter has no risk of self-excitation but requires a complex iterative algorithm. At the same time, when the active load traction technology is implemented, a signal source needs to be provided for each frequency, which increases the cost of the system and makes the system setting more complicated, which provides obstacles for the large-scale application of active load traction technology in the industry. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a harmonic enhanced load traction system that is compatible with the tuning of the fundamental wave and the second harmonic, has a high degree of integration, and can achieve impedance tuning of the harmonics without introducing other devices such as a signal source.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a harmonic enhanced load-pull system, which includes: a circulator, an impedance tuner, a high-pass filter, a radio frequency power amplifier and a reflectionless duplexer connected end to end to form a closed-loop structure; the input end of the circulator is connected to the bias structure of the device to be tested, and the fundamental wave signal is connected to the reflectionless duplexer to form an open-loop structure.

[0007] Preferably, the circulator includes a first circulator and a second circulator connected in sequence, wherein a first end of the first circulator is connected to an output end of a bias structure of the device under test, and a second end is connected to an input end of the reflectionless duplexer; and one end of the second circulator is grounded.

[0008] Preferably, the reflectionless duplexer includes a first directional coupler, a low-pass filter and a second directional coupler connected in sequence; the isolation end of the first directional coupler is connected to the output end of the radio frequency power amplifier, the coupling end of the second directional coupler is grounded, and its through end is connected to the fundamental wave signal source.

[0009] Preferably, when a harmonic signal passes through the reflectionless duplexer, the harmonic signal is input from the isolation end of the first directional coupler and output from the input end to the output end of the bias structure of the device under test; when a fundamental wave signal passes through, the fundamental wave signal is input from the fundamental wave end of the second directional coupler and output from the input end of the first directional coupler.

[0010] Preferably, the impedance tuner comprises an adjustable attenuator and an adjustable phase shifter connected in sequence.

[0011] The benefits of the harmonic enhanced load traction system provided by the present invention are:

[0012] 1. The present invention uses an active closed-loop load-pull structure at the harmonic and an active open-loop load-pull structure at the fundamental, which effectively supports the tuning of the fundamental and second harmonics, has a high degree of integration, and can achieve impedance tuning of harmonics without introducing other equipment such as a signal source.

[0013] 2. The present invention realizes the synthesis of fundamental wave and second harmonic through a reflectionless duplexer instead of a broadband combiner, which reduces the loss in the load-pull structure, reduces the requirements for the signal source in the open-loop structure, and avoids the instability of the active load-pull structure due to signal reflection.

[0014] 3. The present invention broadens the frequency tuning range by setting an impedance tuner, which can easily achieve higher-order harmonic tuning and obtain better test results; at the same time, it avoids the need for complex iterative algorithms and high-power and high-gain amplifiers in traditional load-pull systems, saving time and instrument costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The prior art is: (a) an open-loop active load-pull system, (b) a closed-loop active load-pull system;

[0016] Figure 2 A structural diagram of the connection between the harmonic enhanced load pull system provided by the present invention and the bias structure of the power amplifier;

[0017] Figure 3 A structural diagram of a reflectionless duplexer in a harmonic enhanced load-pull system provided by the present invention;

[0018] Figure 4 A simulation schematic diagram of a harmonic enhanced load traction system provided by the present invention;

[0019] Figure 5 This is a simulation result diagram of the harmonic enhanced load traction system provided by the present invention based on ADS, wherein (a) is the tuning range of the fundamental load reflection coefficient, and (b) is the tuning range of the second harmonic load reflection coefficient. DETAILED DESCRIPTION

[0020] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0021] like Figure 2 As shown, the present invention provides a harmonic enhanced load traction system, which includes: a circulator, an impedance tuner, a high-pass filter, a radio frequency power amplifier and a reflectionless duplexer connected end to end to form a closed-loop structure; the input end of the circulator is connected to the bias structure of the device to be tested, and the reflectionless duplexer is connected to the fundamental wave signal to form an open-loop structure.

[0022] Specifically, the present invention uses a circulator, an impedance tuner, a high-pass filter, a radio frequency power amplifier and a reflectionless duplexer connected end to end to form a closed-loop structure, so that the input harmonic signal is returned to the harmonic input end again through feedback, which can avoid the re-injection of the echo to cause loop oscillation and burn the device, thereby improving the stability of the system. In addition, a fundamental signal source is also connected to the reflectionless duplexer to form an open-loop structure. The present invention combines the open-loop structure and the closed-loop structure, so that the system can be compatible with the tuning and matching of the fundamental signal and the harmonic signal at the same time without adding the harmonic signal source, thereby widening the tuning range, replacing the passive load-pulling mechanical structure that is easy to wear, improving the high precision, and ensuring the accuracy of the tuning, reducing the system cost, and simplifying the complexity of the system.

[0023] In this embodiment, the circulator includes a first circulator and a second circulator connected in series, a first end of the first circulator is connected to the output end of the bias structure of the device under test, and a second end is connected to the input end of the reflectionless duplexer; one end of the second circulator is grounded.

[0024] In this embodiment, the circulator is a unidirectional transmission device. In actual use, the first end of the first circulator receives the harmonic signal output by the bias structure of the device under test, and outputs it to the second circulator after transmission by the first circulator. The second circulator is used to suppress interference in the harmonic signal and reduce the loss of the system. It should be noted that the use of two circulators can achieve complete suppression of interference in harmonics. If the number of circulators is increased, the loss in the system loop structure will increase, and the accuracy and efficiency of tuning will be reduced; if the number of circulators is reduced, the interference generated in the harmonics cannot be suppressed. Similarly, the tuning accuracy of the harmonics will also be reduced. Therefore, the number of circulators cannot be increased or decreased at will. In another embodiment, the circulator can be any microwave device with a signal direction selection function, such as a four-port coupler.

[0025] In this embodiment, the impedance tuner includes an adjustable attenuator and an adjustable phase shifter connected in sequence, the adjustable attenuator is used to adjust the amplitude of the frequency, and the adjustable phase shifter is used to adjust the signal phase. The impedance tuner changes the gain of the harmonic signal by adjusting the frequency and phase, avoiding the need for complex iterative algorithms and high-power gain amplifiers, saving time and instrument costs.

[0026] In this embodiment, the system also includes a high-pass filter and a radio frequency power amplifier connected in series with the impedance tuner. The high-pass filter is used to remove low-frequency interference signals in the harmonics. The harmonic signal (second harmonic) is filtered, amplified by the radio frequency power amplifier, and then output to the load end of the device under test.

[0027] In this embodiment, the device under test is preferably a power amplifier, and its bias structure includes: a signal generator, a first power amplifier, a second coupler, a device under test, a second coupler, and a second power amplifier connected in sequence, the first power amplifier and the second power amplifier both include a capacitor and an inductor, one end of the inductor is connected to one end of the capacitor, and the other end is connected to a DC current source, and the other end of the capacitor is respectively connected to the first port of the first circulator and the signal generator. The first coupler and the second coupler are connected to a vector network analyzer.

[0028] like Figure 3 As shown, the reflectionless duplexer includes a first directional coupler, a low-pass filter and a second directional coupler connected in sequence; the isolation end of the first directional coupler is connected to the output end of the radio frequency power amplifier, the coupling end of the second directional coupler is grounded, and its through end is connected to the fundamental wave signal source.

[0029] Specifically, the gain values ​​of the first directional coupler and the second directional coupler are both 3 dB, and a low-pass filter is connected between the coupling end of the first directional coupler and the input end of the second directional coupler. Similarly, a low-pass filter is also connected between the through end of the first directional coupler and the isolation end of the second directional coupler. The low-pass filter is used to filter the fundamental wave signal of the reflectionless duplexer to improve the stability of the fundamental wave signal. In another embodiment, the reflectionless duplexer can be replaced by a reflectionless filter.

[0030] In the closed loop, when a harmonic signal passes through the reflectionless duplexer, the harmonic signal is input from the isolation end of the first directional coupler, and is output from the input end to the output end of the bias structure of the device under test; when a fundamental wave signal passes through, the fundamental wave signal is input from the fundamental wave end of the second directional coupler, and is output from the input end of the first directional coupler.

[0031] Specifically, when the harmonic signal enters the reflectionless duplexer through the loop, the harmonic signal enters from the isolation end of the first directional coupler. By utilizing the 90° phase shift characteristic of the through end of the directional coupler, the reflected signals at the coupling end and the through end of the first directional coupler differ in phase by 180°, and then cancel each other out, so that the reflected signal cannot return to the input end. The signal of the loop is directly output from the input end of the first directional coupler back to the load end (the output end of the bias structure of the device under test), avoiding the reflected signal (the harmonic signal enters the reflectionless duplexer and then reflects back to the input end) from being re-injected, which may easily cause loop oscillation and burn the device, thereby ensuring the stability of the entire system and the accuracy of load traction. Therefore, when the harmonic signal reaches the reflectionless duplexer, it passes through the door without entering, so as to improve the stability of the system.

[0032] When tuning the fundamental signal, the fundamental signal source provides the fundamental signal, which is input from the through end of the second directional coupler, filtered by the low-pass filter, and then merged into the output end (load end) of the bias structure of the device under test from the input end of the first directional coupler, thereby realizing the tuning of the fundamental signal and the harmonic signal. In this way, the isolation of the input end signal is realized, that is, the harmonic signal is input from the first port of the first circulator, and the fundamental signal is input from the reflectionless duplexer. In addition, in the traditional load-pull system, if it is desired to increase the control of the harmonic signal on the basis of controlling the fundamental signal, it is necessary to introduce an additional harmonic signal source, and the price of the introduced harmonic signal source will increase with the increase of frequency. Therefore, when tuning the high harmonic frequency, its price is relatively high. In this embodiment, the reflectionless duplexer enables the system to form a closed-loop structure at the harmonic frequency, thereby realizing the tuning of the harmonic. The present invention can tune and match the harmonics without introducing an additional signal source (i.e., the harmonic signal source), thereby reducing the system cost and simplifying the system complexity.

[0033] In another embodiment, the structure of the present invention can be used to perform open-loop load pulling on harmonics (high frequency) and closed-loop load pulling on fundamental waves. In other embodiments, the structure of the present invention is also used to achieve source pulling (tuning of the source end).

[0034] In this embodiment, the principle of the open-loop structure at the fundamental wave can be expressed as:

[0035]

[0036] Among them, Γ L，1 is the load impedance at the fundamental wave, a 2，1 is the fundamental wave signal of the second port of the incident wave, a g，1 is the voltage wave provided by the signal generator at the load end of the device under test, k1 is the loss coefficient on the path from the signal generator to the output end of the device under test, b 2，1 is the fundamental component of the output wave of the device under test and the input a g，1 The superposition of the reflected waves generated after the scattering can be calculated by the following formula:

[0037]

[0038] Wherein, S1 is the fundamental component of the voltage wave signal output from the device under test, and Γ is the reflection coefficient of the output impedance of the device under test relative to the load (usually 50Ω).

[0039] In the closed-loop structure, the load impedance Γ at the second harmonic can be obtained L，2 for:

[0040]

[0041] Where b 2，2 is the second harmonic component of the output wave of the device under test, a 2，2 is the second harmonic component of the input wave at the output of the device. In order to find the real-time adjustment value of the adjustable phase shifter and the injected signal, the signal flow graph Mason formula can be obtained:

[0042] b 3,2 =k2b 2，2 ,

[0043] b 4，2 =k3b 3，2 e jθ ,

[0044] a 2,2 =k4b 4，2 ,

[0045] Combining the above formulas, we have:

[0046] Γ L，2 =k2k3k4e jθ

[0047] Among them, k2, k3, k4 are the losses or gains on each path respectively, and e jθ is the phase changed by the adjustable phase shifter. b x，2 is the harmonic signal of the xth output port of the device under test, x=1~4.

[0048] like Figure 4 The simulation schematic diagram of the closed-loop structure and the open-loop structure of the present invention is shown. The test environment is Genesys Harbec (HB) harmonic balance simulation, which simulates the signal injection at the load end with an amplitude of 0dBm to 30dBm and a phase of 0° to 360°. Figure 5 This is a diagram showing the simulation results of the tuning range of the fundamental wave and second harmonic load reflection coefficients based on ADS of the present invention.

[0049] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Claims

1. Harmonic enhanced load traction system, characterized in that: include: A circulator, an impedance tuner, a high-pass filter, a radio frequency power amplifier and a non-reflection duplexer are connected end to end to form a closed-loop structure; the input end of the circulator is connected to the bias structure of the device under test, and the non-reflection duplexer is connected to the fundamental wave signal to form an open-loop structure.

2. The harmonic enhanced load traction system according to claim 1, characterized in that: The circulator comprises a first circulator and a second circulator connected in sequence, wherein a first end of the first circulator is connected to an output end of a bias structure of a device under test, and a second end is connected to an input end of a reflectionless duplexer; and one end of the second circulator is grounded.

3. The harmonic enhanced load traction system according to claim 1, characterized in that: The reflectionless duplexer comprises a first directional coupler, a low-pass filter and a second directional coupler which are connected in sequence; the isolation end of the first directional coupler is connected to the output end of the radio frequency power amplifier, the coupling end of the second directional coupler is grounded, and its through end is connected to a fundamental wave signal source.

4. The harmonic enhanced load traction system according to claim 3, characterized in that: When a harmonic signal passes through the reflectionless duplexer, the harmonic signal is input from the isolation end of the first directional coupler, and is output from the input end to the output end of the bias structure of the device under test; when a fundamental wave signal passes through, the fundamental wave signal is input from the fundamental wave end of the second directional coupler, and is output from the input end of the first directional coupler.

5. The harmonic enhanced load traction system according to claim 1, characterized in that: The impedance tuner includes an adjustable attenuator and an adjustable phase shifter which are connected in sequence.

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