A method, apparatus and digital exciter for compensating distributed parameters of vacuum tubes.

Abstract

This application discloses a method, apparatus, and digital exciter for compensating distributed parameters of a vacuum tube, relating to the field of shortwave communication technology. The method includes establishing a mathematical model of the radio frequency input of the plate-to-gate feedback effect of a high-end vacuum tube; obtaining a complex expression describing the total plate input signal based on the distributed parameters of the inter-electrode capacitance of the vacuum tube and the characteristics of the excitation signal; calculating and generating a compensation reference signal that is in real-time phase synchronized with the radio frequency input signal; decomposing the compensation reference signal into in-phase and quadrature components and inputting them into the digital exciter to determine the additional phase modulation angle and additional amplitude generated by the vacuum tube feedback; adjusting the phase and amplitude of the DRM excitation signal in reverse according to the additional phase modulation angle and additional amplitude, and combining it with a direct digital frequency synthesizer to output a pre-compensated phase deviation phase-modulated carrier to achieve vacuum tube distributed parameter compensation; this application can improve the efficiency and stability of vacuum tube distributed parameter compensation.

Description

Technical Field

[0001] This application relates to the field of shortwave communication technology, and in particular to a method, apparatus and digital exciter for compensating distributed parameters of vacuum tubes. Background Technology

[0002] Currently, the RF amplifier stage of the DF100A 100kW shortwave transmitter uses a single high-power metal-ceramic quaternion, which has high gain and relatively high input impedance. Although the inter-electrode (cross-circuit) capacitor Cag1 is small, it is still prone to oscillation. If the neutralization is not good, parasitic oscillations or noise may occur in the high-frequency or low-frequency bands, causing the transmitter to malfunction. In addition, since the transmitter operates in the shortwave band, lead inductance and distributed capacitance become coupling elements between the input and output capacitances. Therefore, effective compensation of the distributed parameters of the vacuum tube is a necessary technical measure to ensure the normal operation of the transmitter's RF system.

[0003] For tetrodes, the RF-grounded screen grid typically acts as a shield between the plate and the gate, reducing the inter-electrode capacitance and contributing positively to mitigating the plate's reaction force on the gate. However, at very high frequencies, the screen grid lead inductance becomes a coupling element between the input and output circuits, negating the screen grid's shielding effect; its adverse effect cannot be ignored. Furthermore, although the tetrode's Cag1 is very small (1.5–10 pF), the RF final stage typically uses a cathode circuit with high input impedance and high-gain amplification, making even small feedbacks prone to oscillation. Therefore, neutralization is necessary to ensure transmitter stability.

[0004] The existing DF100A shortwave transmitter uses a wideband II neutralization bridge circuit to eliminate the adverse effects of the inter-electrode (cross-circuit) capacitance Cag1 (such as shoot-through effect and feedback loop effect). The working principle is to generate a neutralization voltage equal in magnitude but opposite in direction to the excitation voltage through the neutralization capacitor, and to generate a neutralization current opposite in direction to the shoot-through current in the plate circuit through mechanical adjustment of the neutralization capacitor, thus eliminating the shoot-through effect. The neutralization bridge also addresses the adverse effects of feedback. However, it has the following drawbacks:

[0005] Insufficient adjustment precision: Relying on manual observation of the oscilloscope to judge parasitic oscillations, the optimal neutral point cannot be located due to scale errors;

[0006] Poor frequency band adaptability: It cannot balance high and low frequency bands, and the high frequency band is prone to over-neutralization, while the low frequency band is prone to under-neutralization;

[0007] Therefore, the system suffers from poor stability and inadequate compensation accuracy. Therefore, it is of practical research significance and value to provide a distributed compensation technique that can improve the accuracy and stability of electron tube distributed parameter compensation. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this application provides a distributed compensation technology that can improve the efficiency and stability of electron tube distributed parameter compensation. It offers an electron tube distributed parameter compensation method, apparatus, and digital exciter.

[0009] Firstly, the objective of this invention is achieved through the following technical solution:

[0010] A method for compensating distributed parameters of a vacuum tube, applied to a digital exciter for a shortwave emitter, includes:

[0011] A mathematical model of the radio frequency input of the plate-to-gate feedback effect of the high-end vacuum tube is established. Based on the distribution parameters of the interelectrode capacitance of the vacuum tube and the characteristics of the excitation signal, a complex expression describing the total input signal of the plate is obtained.

[0012] The radio frequency input mathematical model is subjected to equivalent substitution processing to calculate and generate a compensation reference signal that is synchronized with the real-time phase of the radio frequency input signal;

[0013] The compensation reference signal is decomposed into in-phase and quadrature components and input into a digital exciter to determine the additional phase modulation angle and additional amplitude generated by the vacuum tube feedback.

[0014] Based on the additional phase modulation angle and additional amplitude, the phase and amplitude of the DRM excitation signal are adjusted in reverse, and combined with the output of the phase-modulated carrier of the direct digital frequency synthesizer to pre-compensate the phase deviation, so as to realize the compensation of the distributed parameters of the vacuum tube.

[0015] By adopting the above technical solution, this application proposes a digital compensation algorithm. By establishing a mathematical model of the electron tube's distributed parameters to replace the physical capacitor, the bottleneck of mechanical adjustment is fundamentally avoided, and full-band adaptive compensation is achieved. The RF input mathematical model is used to characterize the shoot-through effect and feedback loop influence caused by the inter-electrode capacitance. This application establishes an RF input mathematical model of the feedback effect of the plate to the gate of the high-power shortwave transmitter's electron tube, derives the parameter values ​​that satisfy the electron tube's distributed parameter compensation, applies these parameter values ​​to the digital exciter, and then uses the phase-modulated carrier of the digital exciter's output pre-compensation excitation function to achieve electron tube distributed parameter compensation. This solves the problems of difficulty in fine adjustment, inability to balance high and low frequencies, and insufficient hardware reliability caused by the use of neutralizing capacitors in domestic models, and overcomes the many drawbacks of imported models that rely on tuning mechanical structures and vacuum adjustable capacitors. Using the vacuum tube distributed parameter compensation method of this application, the purpose of vacuum tube distributed parameter compensation can be achieved. The optimal MRE index is obtained through experimental observation, thus achieving optimal vacuum tube distributed parameter compensation. In actual experiments, it was found that the band ratio of the high-end vacuum tube in the RF amplifier of the DF100A 100kW shortwave transmitter was -27.36dB before compensation and -39.81dB after compensation. Thus, this application greatly improves the accuracy and stability of vacuum tube distributed parameter compensation through an economical and safe vacuum tube parameter compensation technique. Through full-band adaptive dynamic parameter adjustment, wideband fine compensation can also be achieved.

[0016] In a preferred embodiment of this application, the expression for the radio frequency input mathematical model is:

[0017] Where, parameter K= , Let ω be the angular frequency of the excitation signal, C be the equivalent cross-circuit capacitance, R be the plate load impedance, and A(t) be the audio signal. This is an excitation signal.

[0018] By adopting the above technical solution, the K value integrates the inherent parameters of the vacuum tube (C, R) with the operating condition variables ( This transforms physical disturbances into computable quantities. Among these, angular frequency... Reflecting the characteristics of the operating frequency band; the equivalent cross-circuit capacitance C, i.e., the parasitic capacitance between the plate and the gate, is the root cause of the shoot-through effect. The plate load impedance R determines the strength of the shoot-through effect; the larger the plate load impedance R, the stronger the shoot-through effect. The value of K quantifies the coupling strength of the distributed parameters to the signal; the larger K is, the more significant the high-frequency interference. The RF input mathematical model can quantify the distributed parameter interference to replace the hardware dependence of the traditional neutralizing capacitor, and the equivalent substitution processing achieves real-time phase synchronization, solving the frequency band discreteness problem. This application provides a precise quantitative description of the total input signal of the plate through the RF input mathematical model. The introduction of this expression makes the influence of the distributed parameters no longer an object of empirical or qualitative judgment, but an adjustable variable that can be directly obtained through calculation. In particular, the introduction of parameter K, as the core bridge connecting the physical structure and digital compensation, reflects the combined effect of the internal feedback strength of the vacuum tube and the external circuit parameters.

[0019] In a preferred embodiment of this application, the equivalent substitution specifically includes:

[0020] Let the equivalent in-phase components ,

[0021] Equivalent orthogonal components ,

[0022] Generate phase synchronization signal It can be equivalently replaced by

[0023] .

[0024] By adopting the above technical solution, the equivalent in-phase component Eliminating amplitude attenuation due to the straight-through effect The quadrature feedback component addresses the gate detuning problem. The core of the equivalent processing lies in transforming the originally difficult-to-handle nonlinear feedback process into an I / Q signal form that can be efficiently computed in the digital domain, greatly reducing the computational complexity of real-time compensation. The generated phase synchronization signal maintains real-time phase consistency with the original RF input signal, ensuring the time synchronization and phase continuity of the compensation process and avoiding transient distortion caused by delays or phase jumps.

[0025] In a preferred embodiment of this application: the additional phase modulation angle and additional amplitude Calculated using the following formula:

[0026] .

[0027] By adopting the above technical solution Precisely quantify phase shift. By capturing amplitude distortion and resolving amplitude modulation distortion, this application can obtain the degree of modulation interference of distributed parameters on DRM signals in real time, providing data support for subsequent precise reverse compensation.

[0028] In a preferred embodiment of this application, the generation of the pre-compensated phase-biased phase-modulated carrier satisfies:

[0029] in, and These represent the phase and amplitude of the DRM excitation signal, respectively.

[0030] By adopting the above technical solution, the generation of the phase-modulated carrier for pre-compensation of phase deviation is further limited to meet specific conditions. That is, the compensation process needs to be coordinated with the original phase and amplitude information of the DRM excitation signal. On the one hand, the compensation effect occurs at the source of signal generation, avoiding the cumulative distortion of the subsequent amplification stage. On the other hand, since the compensation is based on the modulation characteristics of the DRM signal itself, it will not destroy the integrity of the original modulation format and ensure the demodulation performance of the digital broadcast signal.

[0031] In a preferred embodiment of this application, the parameter K is determined by dynamically optimizing the modulation error rate, including:

[0032] Scan different K values ​​within the transmitter's operating frequency band;

[0033] Select the K value that optimizes the MER index and write it into the digital exciter parameter configuration table;

[0034] When the electron tube is a metal-ceramic tetrode, the value of K is in the range of 0.1≤K≤5.0.

[0035] By adopting the above technical solution, the frequency band scanning covers the entire shortwave band (3-30MHz) to solve the frequency band dispersion problem. By using the range constraint 0.1≤K≤5.0 to adapt to the characteristics of metal ceramic tubes, over / under neutralization is avoided, and the adaptive compensation efficiency can be improved.

[0036] In a preferred embodiment of this application: the electron tube distributed parameter compensation method achieves full-band adaptive compensation through parameter K, specifically including:

[0037] Establish a mapping relationship between frequency f and parameter K within the transmitter's operating frequency band:

[0038] in b and c are the fitting coefficients related to the electron tube model;

[0039] When the transmitter switches its operating frequency, the corresponding K(f) value is loaded into the digital exciter.

[0040] Real-time pre-compensation is performed on the DRM excitation signal to keep the shoulder ratio index within the preset index range.

[0041] By adopting the above technical solution, the optimal K value at different frequencies is pre-calibrated, and a quadratic function fitting model is constructed. This allows the transmitter to call the corresponding K(f) value and load it into the digital exciter when switching operating frequencies, thereby realizing real-time updates of compensation parameters and achieving full-band adaptive compensation.

[0042] In a preferred embodiment, this application also includes:

[0043] When tube aging or inter-electrode capacitance drift is detected, the following safety compensation is performed:

[0044] Real-time monitoring of plate current harmonic distortion rate ;

[0045] like If the value is greater than 5%, then the gradient optimization algorithm for parameter K is initiated.

[0046] in, The convergence factor;

[0047] When the MER metric stabilizes above the preset stability threshold, the lock is established. It also generates a health report for the electron tube.

[0048] By adopting the above technical solution, a safety compensation mechanism for electron tube aging or inter-electrode capacitance drift is added. By real-time monitoring of the plate current harmonic distortion rate δ, when it exceeds a 5% threshold, a gradient optimization algorithm for parameter K is activated, achieving online diagnosis and adaptive repair of the system's health status. During long-term operation, electron tubes may experience changes in inter-electrode capacitance due to cathode decay, electrode deformation, etc., thereby disrupting the original neutralization state. This invention, by setting up a distortion rate monitoring link, can promptly detect device performance degradation and trigger a dynamic optimization process for parameter K. When the MER index recovers to above a preset stable threshold, a new parameter is locked and a health report is generated.

[0049] Secondly, the objective of this invention is achieved through the following technical solution:

[0050] A shortwave transmission system, comprising:

[0051] The high-power vacuum tube amplifier circuit uses a high-power metal-ceramic tetrode as the final stage power amplification device.

[0052] A digital exciter is used to provide a radio frequency excitation signal to the high-power vacuum tube;

[0053] The processor of the digital exciter executes the steps of the electron tube distributed parameter compensation method described above, which is used to complete the pre-compensation processing of the electron tube distributed parameters before the excitation signal is output, generate a phase-modulated carrier with compensation characteristics and input it to the gate of the high-end electron tube.

[0054] Thirdly, the objective of this invention is achieved through the following technical solution:

[0055] A digital exciter for a shortwave transmitter, the digital exciter embedding a compensation logic unit that performs a vacuum tube distributed parameter compensation method as described above, the digital exciter being configured to:

[0056] Receives audio signals and DRM modulation instructions;

[0057] The vacuum tube distributed parameter compensation algorithm is run, and by establishing a mathematical model of the RF input of the plate-to-gate feedback, the additional phase modulation angle and additional amplitude corresponding to the feedback effect are generated.

[0058] During the generation of the DRM excitation signal, the additional phase modulation angle is calculated using a CORDIC calculator, and a phase-modulated carrier with pre-compensated phase deviation is output through a direct digital frequency synthesizer (DDS) combined with a frequency word (FTW).

[0059] The phase-modulated carrier wave is output as an excitation signal to the input terminal of the high-power vacuum tube to eliminate the shoot-through effect and feedback oscillation caused by the inter-electrode capacitance.

[0060] In summary, this application includes at least one of the following beneficial technical effects:

[0061] 1. By quantitatively modeling the distributed parameters of the inter-electrode capacitance inside the vacuum tube and the characteristics of the excitation signal, a complex expression describing the total input signal of the plate is obtained, thus achieving accurate characterization of the shoot-through effect and the influence of the feedback loop. Based on this, an equivalent substitution process is applied to this mathematical model to generate a compensation reference signal that is synchronized with the real-time phase of the RF input signal. This ensures strict phase consistency between the compensation signal and the original excitation, avoiding the undercompensation or overcompensation problems caused by phase mismatch in traditional neutralization circuits. Furthermore, the compensation reference signal is decomposed into in-phase and quadrature components and input into a digital exciter to determine the additional phase modulation angle and amplitude generated by the vacuum tube feedback, enabling the system to accurately identify the nonlinear distortion components caused by the distributed parameters. Finally, the DRM excitation signal is adjusted in reverse based on this additional phase and amplitude, and combined with the phase-modulated carrier output by the DDS to pre-compensate the phase deviation, active pre-distortion compensation at the signal generation source is achieved.

[0062] 2. This application provides a precise quantitative description of the total input signal of the plate through a mathematical model of the radio frequency input. The introduction of this expression makes the influence of distributed parameters no longer an object of empirical or qualitative judgment, but rather an adjustable variable that can be directly obtained through calculation. In particular, the introduction of parameter K, as the core bridge connecting the physical structure and digital compensation, reflects the combined effect of the internal feedback strength of the vacuum tube and the external circuit parameters. Attached Figure Description

[0063] Figure 1 This is a diagram illustrating the direct-through effect of inter-electrode capacitance;

[0064] Figure 2 This is a schematic diagram of the bridge-type neutralization principle in existing technology;

[0065] Figure 3 This is a schematic diagram illustrating the application of the neutralizing capacitor in the existing DF100A transmitter.

[0066] Figure 4 This is a schematic diagram of the mathematical model of the electron tube neutralizing capacitance in an embodiment of the electron tube distributed parameter compensation method of this application;

[0067] Figure 5 This is a flowchart of a method for compensating distributed parameters of a vacuum tube according to an embodiment of this application;

[0068] Figure 6 This is a diagram illustrating the generation process of the phase-modulated carrier wave for pre-compensating the distributed parameters of a vacuum tube in an embodiment of this application.

[0069] Figure 7 This is a measurement diagram of the shoulder ratio without compensation using the electron tube distributed parameter compensation method of this embodiment;

[0070] Figure 8 This is a measurement diagram of the shoulder ratio after compensation using a vacuum tube distributed parameter compensation method according to this embodiment. Detailed Implementation

[0071] The following is in conjunction with the appendix Figures 1 to 8 This application will be described in further detail.

[0072] To facilitate understanding or improvement of the technical solution of this application, the mainstream tetrode neutralization oscillation method in the prior art will be explained here first:

[0073] The adverse effects of the inter-electrode capacitance Cag1 are mainly reflected in the following two aspects:

[0074] 1. The impact of the straight-through effect

[0075] Figure 1This circuit represents a common cathode transistor circuit. Ug is the excitation voltage, La is the plate resonant circuit, and the inter-electrode capacitances Cag, Cak, and Cgk are inter-electrode parasitic parameters. Capacitors Cak and Cgk are combined into the input and output circuits, while Cag is connected across the input and output capacitors. A portion of the high-frequency current generated by the excitation voltage Ug bypasses the tube and is directly delivered to the plate circuit via the inter-electrode (cross-circuit) capacitance Cag, generating a voltage drop across the load in the plate circuit. This phenomenon is called the shoot-through effect.

[0076] The larger the inter-electrode (cross-circuit) capacitance, the higher the frequency, and the larger the plate load, the greater the shoot-through effect and the more severe the impact. The input and output of a common-cathode circuit are out of phase. A portion of the excitation voltage Ug bypasses the vacuum tube and is directly sent to the plate circuit through the inter-electrode capacitor. The harm it causes is that when the vacuum tube plate current is cut off, due to the shoot-through effect, a portion of Ug is directly sent to the plate circuit through the inter-electrode capacitor, preventing the plate circuit current from being completely cut off. When amplitude modulation is applied, 100% amplitude modulation cannot be achieved, resulting in amplitude modulation signal distortion, circuit instability, and increased excitation power consumption, leading to insufficient excitation.

[0077] 2. Impact of feedback loop

[0078] A feedback loop refers to a portion of the plate current being fed back to the gate circuit through the inter-electrode (cross-circuit) capacitor Cag; it is also commonly referred to as reverse action. Its harmful effect is that it causes a change in the gate input impedance of this stage. When this impedance is reflected in the preceding stage, it causes detuning in the preceding stage's circuit, resulting in instability in the preceding stage's operation. For the plate current Iao of this stage, due to gate detuning, the minimum value of Iao at resonance is different from that of Ig. 20 The fact that the maximum values ​​do not appear at the same time indicates that neutralization is needed (for the gate circuit of this stage, once it is positive feedback, it is easy to generate self-excited oscillation).

[0079] The following methods are typically used to eliminate tetrode neutralization oscillations:

[0080] 1. Reduce the screen grid lead inductance Lg2. For example... Figure 2 As shown, on the one hand, a small LG2 vacuum tube is selected; on the other hand, a screen grid capacitor with high process technology and low lead inductance is used. In the DF100A shortwave transmitter, a screen grid film capacitor with polyimide as the dielectric is used. The screen grid film capacitor is connected to the filament bypass capacitor (such as...) Figure 2 C29 and C30 (with polyimide dielectric) are uniformly mounted on the screen grid disk to reduce the influence of lead inductance. This is a major improvement of tetrodes compared to triodes. The screen grid film capacitor technology greatly improves the stability of the transmitter.

[0081] 2. Select an appropriate screen grid bypass capacitance, i.e., properly handle the relationship between Cag1 and Cg2. As Cg2 increases, the equivalent cross-circuit capacitance... (Equivalent cross-circuit capacitance) Inter-electrode capacitor Cag1 and second-path feedback capacitor The sum of these factors should be reduced, and Cg2 should be appropriately selected without affecting the operating bandwidth. In the DF100A shortwave transmitter, Cg2 is 20000pF. Figure 2 C31 in the middle.

[0082] 3. Select an appropriate neutralization circuit. The DF100A shortwave transmitter uses a wideband II neutralization bridge circuit.

[0083] To address the issues of insufficient neutralization in the low-frequency band and over-neutralization in the high-frequency band of the high-power metal-ceramic tetrode (4CV100000C), the final stage RF power amplifier of the DF100A high-power shortwave transmitter employs a wideband II neutralization bridge circuit, such as... Figure 2 As shown in the image. Neutralization capacitance photograph. Figure 3 As shown.

[0084] When the gate of the high-voltage transistor (4CV100000C) is subjected to an excitation voltage Ug, the equivalent cross-circuit capacitance is utilized. The current Ug acts on the plate circuit, generating a shoot-through current Iag1. Simultaneously, Ug is applied to capacitor C33, producing a neutralizing voltage Un across C33 that is equal in magnitude but opposite in direction to the excitation voltage. This Un acts on the plate circuit through C34, generating a neutralizing current I. Its direction is opposite to Iag1, so the shoot-through effect can be eliminated by adjusting C34 so that I = Iag1.

[0085] From Cag2 via Cg2 ( Figure 2 The feedback formed by Cgk (C31) can be achieved by neutralizing capacitor C34, bypass capacitor C33, and equivalent cross-circuit capacitor C34. The neutralization bridge formed by the vacuum tube input capacitor Cin solves this problem well. When the balance condition of the bridge is met, the voltage acting on points g and b will not generate current in the slot circuit between a and k, that is, the neutralization is good, eliminating the adverse effects of shoot-through and reverse action.

[0086] In one embodiment, such as Figure 4 The diagram shown illustrates the principle of establishing the RF input mathematical model for the plate-to-gate feedback effect in a high-performance vacuum tube. Figure 5 As shown, this application discloses a method for compensating distributed parameters of a vacuum tube, which specifically includes the following steps:

[0087] S1: Establish a mathematical model of the radio frequency input of the plate feedback effect on the gate of the high-end vacuum tube. Based on the distribution parameters of the interelectrode capacitance of the vacuum tube and the characteristics of the excitation signal, obtain a complex expression describing the total input signal of the plate.

[0088] In this embodiment, the radio frequency modulation signal : Where A(t) is the audio signal, This is an excitation signal.

[0089] Transfer function : ;

[0090] Total RF input due to plate-to-gate feedback : ;

[0091] Expanding and combining the above three formulas, we obtain the expression for the plate-to-gate feedback effect, which in turn gives the expression for the RF input mathematical model:

[0092] in, K= , Let ω be the angular frequency of the excitation signal, C be the equivalent cross-circuit capacitance, R be the plate load impedance, and A(t) be the audio signal. As an excitation signal, This represents the phase offset.

[0093] Furthermore, the mathematical model of the radio frequency input is analyzed and studied, and the parameters are set... K= This yields the following expression: The in-phase component I signal of the total input signal is: The quadrature component Q signal of the total input signal is: Using the IQ signal, the amplitude and phase of the total input signal at any given time can be calculated, where the amplitude is: ,

[0094] The phase is: .

[0095] S2: Perform equivalent substitution processing on the mathematical model of the radio frequency input to calculate and generate a compensation reference signal that is in real-time phase synchronization with the radio frequency input signal.

[0096] In this embodiment, the equivalent substitution specifically includes:

[0097] Let the equivalent in-phase components Equivalent orthogonal components It is possible to obtain the same as... Real-time phase remains consistent The expression is used to generate a phase synchronization signal. It can be equivalently replaced by .

[0098] In one embodiment, the parameter K is determined by dynamically optimizing the modulation error rate, including:

[0099] Scan different K values ​​within the transmitter's operating frequency band;

[0100] Select the K value that optimizes the MER index and write it into the digital exciter parameter configuration table;

[0101] When the vacuum tube is a metal-ceramic tetrode, the value of K is in the range of 0.1≤K≤5.0.

[0102] S3: Decompose the compensation reference signal into in-phase and quadrature components and input them into the digital exciter to determine the additional phase modulation angle and additional amplitude generated by the vacuum tube feedback.

[0103] In this embodiment, Two components and The input is fed into the CORDIC calculator in the digital exciter, which calculates the actual additional phase modulation angle produced by the vacuum tube due to feedback. and additional amplitude Among them, the additional phase modulation angle and additional amplitude Calculated using the following formula:

[0104] .

[0105] Specifically, digital actuators work by... and Input the data into the CORDIC calculator to calculate the phase angle of the DRM excitation. and the amplitude of the DRM excitation signal .

[0106] S4: Based on the additional phase modulation angle and additional amplitude, the phase and amplitude of the DRM excitation signal are adjusted in reverse, and combined with the output of the direct digital frequency synthesizer to pre-compensate the phase deviation phase carrier, so as to realize the compensation of the distributed parameters of the vacuum tube.

[0107] In this embodiment, the direct digital frequency synthesizer is a DDS; such as Figure 6 As shown, in order to obtain the phase-modulated carrier with pre-compensated electron tube distributed parameters, the pre-compensated phase angle of the required phase-modulated carrier is obtained by subtracting the additional phase modulation angle from the DRM excitation angle. The frequency word (FTW) and two key parameters are input into the DDS system (direct digital frequency synthesizer (DDS)) to generate the phase-modulated carrier with pre-compensated phase deviation, thereby realizing the compensation of electron tube distributed parameters.

[0108] In summary, a suitable parameter K value can achieve the purpose of compensating for the distributed parameters of the vacuum tube. By applying this vacuum tube distributed parameter compensation parameter to the digital exciter and adjusting parameter K, the optimal MER index (MRE is the modulation error rate) can be observed, which is the optimal vacuum tube distributed parameter compensation.

[0109] like Figure 7 and Figure 8 The figure shown is a comparison of the effects of the electron tube distributed parameter compensation method of this application in the DF100A shortwave transmitter. Figure 7 The original shoulder ratio compensation value was -27.36dB, while Figure 8 The compensated shoulder ratio is -39.81 dB. This application establishes a targeted mathematical model for the neutralizing capacitor of the vacuum tube (such as...). Figure 4 As shown in the figure, digital circuit processing is used to achieve tube parameter compensation. The objective can be achieved using a single universal parameter K, resulting in high engineering applicability and frequency adaptability. This application replaces the traditional mechanical capacitor structure with an algorithm, without affecting the RF structure and stability of the high-power transmitter. It not only achieves excellent compensation results but also avoids adding extra mechanical components or circuit elements, significantly reducing maintenance, overcoming component lifespan limitations, and ensuring high stability and broadcast safety.

[0110] In one embodiment, a method for compensating distributed parameters of a vacuum tube further includes achieving full-band adaptive compensation through parameter K, specifically including:

[0111] S10: Establish the mapping relationship between frequency f and parameter K within the transmitter's operating frequency band:

[0112] in b and c are the fitting coefficients related to the vacuum tube model; when the transmitter switches the operating frequency, the corresponding K(f) value is loaded into the digital exciter; the DRM excitation signal is pre-compensated in real time to keep the shoulder ratio index within the preset index range.

[0113] In this embodiment, the preset index range, such as the shoulder ratio index, is maintained above -39.81 dB.

[0114] In one embodiment, a method for compensating distributed parameters of a vacuum tube further includes:

[0115] S100: When tube aging or inter-electrode capacitance drift is detected, the following safety compensation is performed:

[0116] S1001: Real-time monitoring of plate current harmonic distortion rate ;like If the value is greater than 5%, then the gradient optimization algorithm for parameter K is initiated.

[0117] in, is the convergence factor.

[0118] S1002: When the MER indicator stabilizes above the preset stability threshold, lock the position. It also generates a health report for the electron tube.

[0119] For example, a preset stabilization threshold of 25-30 dB is used. In practical shortwave transmission systems, this preset stabilization threshold can be set experimentally or by following industry specifications. For instance, in DRM excitation systems, the preset stabilization threshold is typically set above 28 dB to ensure broadcast quality.

[0120] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0121] In one embodiment, a shortwave transmission system is provided, which is applied to a vacuum tube distributed parameter compensation method described in the above embodiment.

[0122] A shortwave transmission system includes a high-power vacuum tube amplifier circuit and a digital exciter. A detailed description of the shortwave transmission system is as follows:

[0123] The high-power vacuum tube amplifier circuit uses a high-power metal-ceramic tetrode as the final stage power amplification device.

[0124] A digital exciter is used to provide radio frequency excitation signals to high-performance vacuum tubes;

[0125] The processor of the digital exciter executes a step such as a vacuum tube distributed parameter compensation method, which is used to complete the pre-compensation processing of the vacuum tube distributed parameters before the excitation signal is output, generate a phase-modulated carrier with compensation characteristics and input it to the gate of the high-end vacuum tube.

[0126] For specific limitations regarding a shortwave transmission system, please refer to the limitations of a vacuum tube distributed parameter compensation method described above, which will not be repeated here. The processor of the digital exciter provides computational and control capabilities. Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a processor or a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0127] In one embodiment, a digital exciter for a shortwave transmitter is provided. The digital exciter embeds a compensation logic unit that performs a method such as a vacuum tube distributed parameter compensation method. The digital exciter is configured to:

[0128] Receives audio signals and DRM modulation instructions;

[0129] The vacuum tube distributed parameter compensation algorithm is run, and by establishing a mathematical model of the RF input of the plate-to-gate feedback, the additional phase modulation angle and additional amplitude corresponding to the feedback effect are generated.

[0130] During the generation of the DRM excitation signal, the additional phase modulation angle is calculated using a CORDIC calculator, and a phase-modulated carrier with pre-compensated phase deviation is output through a direct digital frequency synthesizer (DDS) combined with a frequency word (FTW).

[0131] The phase-modulated carrier wave is output as the excitation signal to the input terminal of the high-power vacuum tube to eliminate the shoot-through effect and feedback oscillation caused by the inter-electrode capacitance.

[0132] Specifically, the compensation logic unit adopts a multi-stage pipelined processing architecture, including a signal receiving module, a mathematical modeling module, an equivalent substitution module, a CORDIC processing module, and a pre-compensation synthesis module. Detailed descriptions of each functional module are as follows:

[0133] The signal receiving module is used to receive audio signal A(t) and DRM modulation instructions, which include carrier frequency f and modulation method;

[0134] The mathematical modeling module is used to establish a mathematical model of the radio frequency input (RF input) for the plate-to-gate feedback effect in high-performance vacuum tubes. The complex expression of the RF input mathematical model is as follows: ;

[0135] The equivalent substitution module performs equivalent substitution processing on the RF input mathematical model and calculates and generates a compensation reference signal that is synchronized with the RF input signal in real time. ;

[0136] The CORDIC processing module decomposes the compensation reference signal into in-phase and quadrature components, and inputs them into the digital exciter to determine the additional phase modulation angle and additional amplitude generated by the vacuum tube feedback.

[0137] The pre-compensation synthesis module reverses the phase and amplitude of the DRM excitation signal based on the additional phase modulation angle and additional amplitude, and outputs a phase-modulated carrier with pre-compensated phase deviation in conjunction with the direct digital frequency synthesizer.

[0138] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0139] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method of distributed parameter compensation for a tube, characterized by, The application relates to a digital exciter applied to a short-wave transmitting electrode, and a method. An RF input mathematical model of a high-end tube screen-to-grid feedback is established, and a complex expression describing the total input signal of the screen is obtained based on the distribution parameters of the tube inter-electrode capacitance and the characteristics of the excitation signal; The RF input mathematical model is subjected to equivalent replacement processing, and a compensation reference signal which is in real-time phase synchronization with the RF input signal is calculated and generated; The compensation reference signal is decomposed into in-phase and quadrature components and input into the digital exciter, so as to determine the additional phase modulation angle and the additional amplitude generated by the tube feedback; According to the additional phase modulation angle and the additional amplitude, the phase and amplitude of the DRM excitation signal are reversely adjusted, and a phase-modulated carrier with a pre-compensation phase deviation is output by a direct digital frequency synthesizer, so that the tube distribution parameter compensation is realized.

2. The method of claim 1, wherein The expression of the RF input mathematical model is as follows: wherein, is the total input signal to the plate, and K is a parameter , is the angular frequency of the excitation signal, C is the equivalent shunt capacitance, R is the plate load impedance, A(t) is the audio signal, is the excitation signal, j is the imaginary unit, t is the time variable, and e is the natural constant.

3. The method of claim 2, wherein The equivalent replacement specifically includes: Let the equivalent in-phase component , Equivalent orthogonal components where Q is the orthogonal component; Generating a phase-synchronous signal may be equivalently replaced by 。 4. The method of claim 2, wherein The additional phase modulation angle and additional amplitude By the following formula: 。 5. The method of claim 1, wherein The generation of the phase-modulated carrier with the pre-compensation phase deviation satisfies: wherein, and are the phase and amplitude, respectively, of the DRM excitation signal.

6. The method of claim 2, wherein The parameter K is determined by dynamically optimizing the modulation error rate, and includes: Different K values are scanned in the working frequency band of the transmitter; The K value which makes the MER index optimal is selected and written into a parameter configuration table of the digital exciter; When the tube is a metal ceramic tetrode, the value range of K is 0.1<=K<=5.

0.

7. The method of claim 2, wherein The tube distribution parameter compensation method realizes full-band adaptive compensation through the parameter K, and specifically includes: A mapping relationship between the frequency f and the parameter K is established in the working frequency band of the transmitter: wherein b, c are tube model dependent fitting coefficients; When the working frequency of the transmitter is switched, the corresponding K(f) value is called and loaded into the digital exciter; The DRM excitation signal is real-time pre-compensated, so that the shoulder ratio index is maintained in a preset index interval.

8. The method of claim 2, wherein, Further includes: When the tube aging or the inter-electrode capacitance drift is detected, the following safety compensation is performed: Real-time monitoring of screen current harmonic distortion ratio ; If >5%, then start the gradient optimization algorithm for the parameter K: wherein, is a convergence factor; When the MER index is stable above the preset stable threshold, locking and generating a tube health report.

9. A short wave transmitting system, characterized by Includes: A high-end tube amplification circuit adopts a high-power metal ceramic tetrode as a final-stage power amplifier device; A digital exciter is used for providing an RF excitation signal to the high-end tube; The processor of the digital exciter executes the steps of the tube distribution parameter compensation method according to any one of claims 1 to 8, so as to complete the pre-compensation processing of the tube distribution parameters before the excitation signal is output, generate a phase-modulated carrier with compensation characteristics, and input the phase-modulated carrier into the grid of the high-end tube.

10. A digital exciter for a short wave transmitter, characterized by The digital exciter is embedded with a compensation logic unit which executes the tube distribution parameter compensation method according to any one of claims 1 to 8, and the digital exciter is configured to: Receive an audio signal and a DRM modulation instruction; Run the tube distribution parameter compensation algorithm, generate an additional phase modulation angle and an additional amplitude corresponding to the feedback effect by establishing the RF input mathematical model of the screen-to-grid feedback; In the process of generating the DRM excitation signal, the additional phase modulation angle is calculated and processed by using a CORDIC calculator, and a phase-modulated carrier with a pre-compensation phase deviation is output by a direct digital frequency synthesizer DDS combined with a frequency word FTW; The phase-modulated carrier is output as the excitation signal to the input end of the high-end tube, so as to eliminate the straight-through effect and feedback oscillation caused by the inter-electrode capacitance.

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