CN109085544B - Circuit for improving stability of transmitting signal - Google Patents
Circuit for improving stability of transmitting signal Download PDFInfo
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- CN109085544B CN109085544B CN201811268226.4A CN201811268226A CN109085544B CN 109085544 B CN109085544 B CN 109085544B CN 201811268226 A CN201811268226 A CN 201811268226A CN 109085544 B CN109085544 B CN 109085544B
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- 239000003990 capacitor Substances 0.000 claims abstract description 85
- 238000004146 energy storage Methods 0.000 claims abstract description 49
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- 229910044991 metal oxide Inorganic materials 0.000 claims description 3
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- 239000004065 semiconductor Substances 0.000 claims description 3
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- 238000010586 diagram Methods 0.000 description 7
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- 238000010894 electron beam technology Methods 0.000 description 5
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
- G01S7/282—Transmitters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The invention discloses a circuit for improving the stability of a transmitted signal, wherein a high-voltage power supply is connected with an energy storage capacitor, the energy storage capacitor is connected with a modulator, and the modulator is connected with the cathode of a microwave tube; the tube body of the microwave tube is connected with a tube body current adjusting circuit, and the tube body current adjusting circuit is connected with a tube body current branch; the collector of the microwave tube is connected with the collector current branch; the tube body current branch and the collector current branch are respectively connected with the energy storage capacitor; the high-voltage power supply charges the energy storage capacitor and provides constant direct-current high voltage; the energy storage capacitor stores high-voltage direct-current energy; when the modulator is closed, the energy storage capacitor can discharge the microwave tube through the modulator; the tube current branch, the collector current branch and the tube current adjusting circuit provide a current loop for modulator discharge.
Description
Technical Field
The invention relates to a circuit for improving the stability of a transmitting signal, and belongs to the technical field of microwave amplifiers.
Background
The stability of the transmitted signal refers to the stability of the amplitude, phase, pulse repetition frequency and pulse width of the radio frequency signal. Modern radars widely employ pulse compression, moving object display and pulse doppler techniques, all of which require good stability of the transmitted signal. For example, in moving target display (MTI) radar, the phase distortion of the transmitted signal will result in a decrease in the improvement factor; in Pulse Doppler (PD) radar, noise generated by a microwave amplifier will lead to broadening of the spectral line and an increase in the sideband noise level in the detection zone, affecting the visibility of the radar in the clutter background, or causing false target echoes to appear.
Factors that affect the stability of the transmitted signal can be categorized into a certain amount of instability and a random amount of instability. The amount of instability determined is a periodic function of time from factors such as ripple of the transmitter power supply, top fluctuations of the pulse modulation waveform, and regular mechanical vibrations of the surrounding environment. Random instabilities are arbitrary, such as noise in the transmitting tube, random variations in the amplitude of the modulated pulses, etc., may be one of the reasons. In general, the effect of noise modulation inside the rf amplifier is much smaller than that of regular parasitic modulation such as by supply ripple. Furthermore, in radar applications, the short-term stability of the transmitted signal is of major concern, i.e. the intra-and inter-pulse variations of these instabilities are considered.
The stability of the transmitted signal is measured in the frequency domain using the phase noise of the signal, which represents spurious outputs of the transmitted signal in the frequency domain in the signal spectrum. For example, in PD radar systems, PD weather radars typically require better than-85 dBc for signal phase noise for ideal clutter suppression and target detection, while military on-board fire pulse Doppler radars require more stringent transmit signal phase noise. To meet the signal spectrum purity requirements, the transmitter must be carefully designed with a targeted design. For example, in an airborne PD radar, a high-voltage power supply of a transmitter needs to be a stabilized voltage power supply, ripple waves and stability of the transmitter are better than 10 < -4 > -10 < -5 >, the top fluctuation of a pulse modulator is required to be not more than 2% -3%, and the top drop is not more than 5%.
In high power klystron transmitters, klystron electron beam voltages are typically tens of kilovolts to hundreds of kilovolts, electron beam currents are tens of amperes, and such high power high voltage power supplies are almost completed by high frequency switching power supplies. According to the signal stability requirement of a transmitter, the stability of a high-voltage power supply is required to be 10 < -4 > -10 < -5 >, and the stability of a high-voltage switching power supply with the power level of tens of kilowatts or even hundreds of kilowatts is very difficult to reach 10 < -4 > -10 < -5 >; in addition, during the pulse period, the energy of the high-voltage power supply is far smaller than the energy discharged by the energy storage capacitor, along with the continuous reduction of the pulse energy, the charge on the energy storage capacitor is reduced, the voltage is reduced, so that the trailing edge amplitude of the output modulation pulse is lower than that of the leading edge, namely, the pulse top drop is generated, the transmitter outputs a radio frequency signal to generate amplitude distortion and phase distortion, the distance resolution of the radar is reduced by the amplitude distortion, and the frequency offset is generated by the phase distortion. Increasing the capacity of the energy storage capacitor can reduce the pulse top drop, but in order to prevent the microwave tube from being damaged when the microwave tube is ignited, the fluctuation of the pulse top is reduced and the capacity of the transmitter is limited, and when the capacity of the energy storage capacitor is selected, the allowance cannot be left too large; in addition, there is a phase delay between the transmitter rf input signal and the output signal, which is determined primarily by the electron transit time in the microwave tube. The change of the amplitude of the modulation pulse causes the change of the electron velocity, and thus the electron transit time also changes, so that the phase of the radio frequency output signal is unstable. Thus, to meet the stability requirements of the transmitted signal, the stability of the amplitude of the modulated pulses and the top fluctuation of the modulated pulses should be controlled at a high level.
Document 1: nie Keqin stability of klystron transmitters in moving target display radars, modern radars, 1992, 14 (2): 61-66; document 2: fan Qing, analysis of the performance of "de-Q" circuits and parallel adjustment circuits, modern electronics, 1994, 48 (3): 48-51. Document 1 and document 2 describe that in order to reduce the amplitude instability between adjacent modulation pulses of the klystron cathode, a de-Q circuit and a bleeder circuit may be employed. The de-Q circuit adopts a method of suddenly reducing the Q value of the quality factor of the charging loop, so that the artificial line stops charging to keep the voltage unchanged. When the Pulse Repetition Frequency (PRF) of the radar changes, the voltage leakage is different for the de-Q circuit due to different waiting time after the manual line is fully charged, and the PRF changes to cause larger fluctuation of a power supply, so that the circuit cannot adapt to the situation of the change of the pulse repetition frequency, and the adjustment precision is low. The bleeder circuit is used for consuming redundant energy on the artificial line before the arrival of the discharge pulse after the artificial line voltage is slightly higher than the required level, so that the artificial line voltage is maintained at a stable level before the discharge. Since the operating time of such a circuit is after the manual line is fully charged, it is also called a post-charge regulator. The bleeder circuit works under high voltage, and the component withstand voltage requirement is higher, selects the use difficulty, and efficiency is lower. Furthermore, the documents 1 and 2 can only solve the problem that the stability of the transmitter radio frequency signal caused by the power supply ripple is deteriorated because the inter-pulse stability of the modulation pulse amplitude is not improved
Document 3: wei Zhi, influence of pulse modulated waveform distortion and mains ripple on radar transmitter quality, modern radars, 1992, 14 (3): 81-91; document 4: wang Peijin influence of supply ripple on the performance of PD radar, modern radar, 1997 (4). Documents 3 and 4 disclose that in order to reduce the influence of the ripple of the power supply on the radar transmission signal, the switching frequency of the switching power supply can be controlled and strictly synchronized with the pulse repetition frequency of the radar system. The difficulty and complexity of the method for adopting the filament power supply and other small-power switching power supplies are low, but when the radar PRF continuously changes, the method is adopted for adopting high-voltage power supplies of tens of kilowatts and even hundreds of kilowatts, so that a transmitter system is complex, and the cost is high. Furthermore, documents 3 and 4 can only solve the deterioration of the stability of the transmitter radio frequency signal due to the power supply ripple, and cannot improve the inter-pulse instability of the modulation pulse amplitude and the deterioration of the stability of the transmission signal due to the intra-pulse top fluctuation and the pulse top drop.
Document 5: zhang Xianghui, research on phase noise characteristics of high-power klystron transmitters, modern radars, 2012, 34 (3): 65-69. Document 5 describes a method of controlling the electron beam voltage and the collector voltage stability of a klystron, which separates a tube body from a collector, a high-power high-voltage power supply supplies a voltage between a klystron cathode and a klystron collector, and a low-voltage low-power supply is attached between the collector and the tube body for compensating for instability of the tube body voltage. The low-power low-voltage power supply can easily achieve higher stability, thereby improving the phase noise of the transmitter. However, the additional power supply introduces new power supply ripple and noise, and the reliability and anti-interference capability of the additional power supply must be specially designed to take into account the microwave tube ignition condition, which increases the complexity of the system.
Document 6: jae setup Lee, p.ully, radar's TWT phase noise reduction, radar Conference,2005IEEE International,2005:43-48; document 7: he Pengjun, zhang Guanjie, , analysis of travelling wave tube amplifier phase noise and suppression thereof, fire control radar technology, 2006, 35 (1): 26-29; document 8: liu Jie, he Pengjun, analysis of the influence of phase noise of travelling wave tube transmitters on radar range, fire-controlled radar technology, 2012, 41 (4): 72-75. The document 6, the document 7 and the document 8 all propose schemes for reducing the phase noise of the travelling wave tube amplifier by adopting a phase-locked loop technology; document 7 and document 8 also describe that in order to suppress the phase noise of the traveling wave tube amplifier, a power supply ripple recognition technique may be also employed. The phase-locked loop technology utilizes a phase detector to respectively detect the phase information of the input radio frequency signal and the output radio frequency signal of the transmitter, and sends the difference value of the input radio frequency signal and the output radio frequency signal to the phase shifter for phase compensation. The power supply ripple recognition technology samples the power supply voltage with ripples through a voltage divider, outputs two paths through a bottom limiter, averages one path through a top limiter and an integrator, compares the two paths of signals with the other path of signals in a comparator, and adjusts the control voltage of the phase shifter according to the compared difference value so as to achieve the purpose of phase compensation. The phase-locked loop technology directly plays a role in the radio frequency signal, has high requirements on devices, is relatively complex in technology and has high cost; the power supply ripple recognition technology can only solve the problem of transmitter radio frequency signal stability deterioration caused by power supply ripple, and cannot improve the inter-pulse instability of the modulation pulse amplitude and the transmission signal stability deterioration caused by intra-pulse top fluctuation and pulse top drop.
Disclosure of Invention
In view of the above, the present invention provides a circuit for improving the stability of a transmission signal.
In order to solve the problems, the invention adopts the following technical scheme: the circuit for improving the stability of the transmitted signal is characterized by comprising a high-voltage power supply, an energy storage capacitor, a modulator, a microwave tube, a tube body current branch, a collector current branch and a tube body current adjusting circuit. The high-voltage power supply is connected with the energy storage capacitor, the energy storage capacitor is connected with the modulator, and the modulator is connected with the cathode of the microwave tube; the tube body of the microwave tube is connected with a tube body current adjusting circuit, and the tube body current adjusting circuit is connected with a tube body current branch; the collector of the microwave tube is connected with the collector current branch; the tube body current branch and the collector current branch are respectively connected with the energy storage capacitor;
the high-voltage power supply charges the energy storage capacitor and provides constant direct-current high voltage; the energy storage capacitor stores high-voltage direct-current energy; when the modulator is closed, the energy storage capacitor can discharge the microwave tube through the modulator; the tube current branch, the collector current branch and the tube current adjusting circuit provide a current loop for modulator discharge.
The negative end of the high-voltage power supply E1 is respectively connected with one end of the energy storage capacitor C1 and one end of the modulator Q1; the other end of the modulator Q1 is connected with the cathode of the microwave tube; the tube body of the microwave tube is connected with one end of the tube body current adjusting circuit S3 and is connected with the ground; the other end of the tube body current adjusting circuit S3 is connected with one end of a tube body current branch S1; the collector of the microwave tube is connected with one end of a collector current branch S2; the other end of the tube current branch S1 and the other end of the collector current branch S2 are connected to the other end of the energy storage capacitor C1 together and then connected with the positive end of the high-voltage power supply E1.
The tube body current adjusting circuit S3 is a closed loop system and comprises a voltage dividing network S31, an error amplifier and compensation network S32, a power amplifying circuit S33 and an adjusting switch S34; the voltage dividing network S31 is a resistor and capacitor voltage dividing circuit, one end of the voltage dividing network S is connected with the negative end of the C1 or the cathode of the microwave tube, and the other end of the voltage dividing network S is connected with the ground; s31, sampling the voltage of C1 relative to the ground, and sending the sampled voltage with proper magnitude to an error amplifier and compensation network S32; the error amplifier and compensation network S32 compares the sampling voltage sent by the S31 with a reference voltage Vref and outputs an error amplified signal; the power amplification circuit S33 amplifies the power of the error amplification signal sent from the compensation network S32, and sends the power amplified signal to the adjustment switch S34 as a driving signal of the adjustment switch; the adjusting switch S34 adopts an insulated gate bipolar transistor IGBT or a metal oxide semiconductor field effect transistor MOSFET as an adjusting switch tube, one end of the adjusting switch tube is connected with a tube body current branch, and the other end of the adjusting switch tube is connected with a tube body of a microwave tube and works in a linear state, and the adjusting switch tube is similar to a real-time variable resistor.
The voltage division network S31 comprises voltage division resistors R1-Rn and voltage division capacitors C1-Cn; the resistor R1 and the capacitor C1 are connected in parallel, the resistor R2 and the capacitor C2 are connected in parallel, similarly, until the resistor Rn and the capacitor Cn are connected in parallel, and then all the resistors and the capacitors which are connected in parallel are connected in series in sequence; the unconnected end of the resistor R1 is a connection point P11, the common connection point of the resistor Rn-1 and the resistor Rn is P12, and the unconnected end of the resistor Rn is a connection point P13; the connection point P11 is connected with the negative end of the energy storage capacitor C1 or the cathode of the microwave tube, and the connection point P13 is connected with the ground; the sampling voltage of the connection point P12 changes in real time according to the voltages at two ends of the energy storage capacitor C1.
The error amplifier and compensation network S32 comprises resistors R21, R22 and R23, capacitors C21, C22 and C23, an operational amplifier N21 and a reference voltage Vref; after the resistor R21 and the capacitor C21 are connected in series, the resistor R22 is connected in parallel, one end of the parallel circuit is a connection point P21, and the other end of the parallel circuit is connected with the inverting input end of the operational amplifier N21; after the resistor R23 and the capacitor C23 are connected in series, the resistor R23 and the capacitor C22 are connected in parallel, one end of the parallel circuit is connected with the inverting input end of the operational amplifier N21, and the other end of the parallel circuit is connected with the output end of the operational amplifier N21; the reference voltage Vref is connected with the non-inverting input end of the operational amplifier N21, and the output end of the operational amplifier N21 is a connection point P22; the connection point P21 is connected to the connection point P12 in the circuit of the voltage dividing network S31.
The power amplifying circuit S33 comprises an NPN triode V31, a PNP triode V32, auxiliary voltages +15V and-15V; the base electrode of the triode V31 is connected with the base electrode of the triode V32, and the connection point is P31; the collector of the triode V31 is connected with auxiliary voltage +15V, and the collector of the triode V32 is connected with auxiliary voltage-15V; the emitter of the triode V31 is connected with the emitter of the triode V32, and the connection point is P32; the connection point P31 is connected with a connection point P22 in the error amplifier and compensation network S32, and the connection point P32 is connected with the gate electrode of an adjusting switch tube in the adjusting switch S34; the power amplifying circuit S33 amplifies the small signal sent by the error amplifier and compensation network S32 to a power signal for driving the adjusting switch tube, and the linear power amplifier can also be used for achieving the purpose.
The regulating switch S34 includes a switch component K41, a capacitor component C41, a resistor component R41, and a transient suppression diode (TVS) component V41; the switch component K41 is formed by connecting a single high-power switch or a plurality of low-power switches in parallel; the transient suppression diode component V41 is formed by connecting a single high-voltage high-current TVS or a plurality of TVSs in series-parallel connection; after the switch component K41, the capacitor component C41, the resistor component R41 and the transient suppression diode component V41 are connected in parallel, one end is used as a connecting point P41, and the other end is used as a connecting point P42; the connection point P41 is connected with the other end of the energy storage capacitor, and the connection point P42 is connected with the microwave tube body.
Compared with the prior art, the invention has the following beneficial effects: the invention obviously reduces the requirements on a high-voltage power supply and a modulator, solves the problems of unstable pulse amplitude modulation, and deterioration of the stability of a transmitting signal caused by top fluctuation and pulse top drop in the pulse, and improves the stability of a radio-frequency signal of the transmitter caused by power supply ripple. The system has simple circuit, low voltage and power requirements on components, low cost, easy realization and small efficiency loss, and is suitable for various occasions.
Drawings
Fig. 1 is a block diagram of the components of the present invention.
Fig. 2 is a block diagram of a conventional radar transmitter assembly.
Fig. 3 is a schematic circuit diagram of the present invention.
Fig. 4 is a schematic circuit diagram of the present invention.
Fig. 5 is a typical circuit of the voltage divider network of the present invention.
Fig. 6 is a typical circuit of an error amplifier and compensation network in the present invention.
Fig. 7 is a typical circuit of the power amplifying circuit in the present invention.
Fig. 8 is a typical circuit of the regulating switch in the present invention.
Fig. 9 is a schematic circuit diagram of another implementation of the present invention.
FIG. 10 is a schematic waveform diagram of a sampling voltage in a voltage divider network and a reference voltage in an error amplifier and compensation network using the circuit of FIG. 4.
FIG. 11 is a schematic waveform diagram of a sample voltage in a voltage divider network and a reference voltage in an error amplifier and compensation network using the circuit of FIG. 9.
Detailed Description
The invention is further described in conjunction with the following.
As shown in fig. 1, the present invention provides a circuit for improving stability of a transmitted signal, which includes a high voltage power supply, an energy storage capacitor, a modulator, a microwave tube, a tube current branch, a collector current branch, and a tube current adjusting circuit. The high-voltage power supply is connected with the energy storage capacitor; the energy storage capacitor is connected with the modulator; the modulator is connected with the cathode of the microwave tube; the tube body of the microwave tube is connected with the tube body current adjusting circuit; the tube body current adjusting circuit is connected with the tube body current branch circuit; the collector of the microwave tube is connected with the collector current branch; the tube body current branch and the collector current branch are respectively connected with the energy storage capacitor.
The high-voltage power supply charges the energy storage capacitor and provides constant direct-current high voltage; the energy storage capacitor stores high-voltage direct-current energy; the modulator is similar to a switch, and when the modulator is closed, the energy storage capacitor can discharge the microwave tube through the modulator; the tube current branch, the collector current branch and the tube current adjusting circuit provide a current loop for modulator discharge.
As shown in fig. 2, the present invention adds a tube current adjusting circuit to the conventional radar transmitter, and the tube current adjusting circuit can be regarded as a variable resistor.
As shown in fig. 3, the negative terminal of the high-voltage power supply E1 is connected to one end of the energy storage capacitor C1 and one end of the modulator Q1 respectively; the other end of the modulator Q1 is connected with the cathode of the microwave tube; the tube body of the microwave tube is connected with one end of the tube body current adjusting circuit S3 and is connected with the ground; the other end of the tube body current adjusting circuit S3 is connected with one end of the tube body current branch S1; the collector of the microwave tube is connected with one end of a collector current branch S2; the other end of the tube current branch S1 and the other end of the collector current branch S2 are connected to the other end of the energy storage capacitor C1 together and then connected with the positive end of the high-voltage power supply E1.
The tube body current branch S1 generally comprises a capacitor, a resistor, an overcurrent relay and an ammeter; the collector current branch S2 generally includes a capacitor, a resistor, an overcurrent relay, and an ammeter.
As shown in fig. 4, the tube current adjusting circuit S3 is a closed loop system, and includes a voltage dividing network S31, an error amplifier and compensation network S32, a power amplifying circuit S33, and an adjusting switch S34. The voltage dividing network S31 is a resistor and capacitor voltage dividing circuit, one end of the voltage dividing network S is connected with the negative end of the C1, and the other end of the voltage dividing network S is connected with the ground. S31, sampling the voltage of C1 relative to the ground, and sending the sampled voltage with proper magnitude to the error amplifier and compensation network S32; the error amplifier and compensation network S32 compares the sampling voltage sent by the S31 with a reference voltage Vref and outputs an error amplification signal; the power amplifying circuit S33 amplifies the power of the error amplifying signal sent from S32, and sends the amplified signal to the adjusting switch S34 as a driving signal of the adjusting switch; the adjusting switch S34 adopts an insulated gate bipolar transistor IGBT or a metal oxide semiconductor field effect transistor MOSFET as an adjusting switch tube, one end of the adjusting switch tube is connected with the tube current branch, and the other end of the adjusting switch tube is connected with the tube of the microwave tube and works in a linear state, and the adjusting switch tube is similar to a real-time variable resistor.
As shown in fig. 5, the voltage dividing network S31 typically includes voltage dividing resistors R1 to Rn and voltage dividing capacitors C1 to Cn. In a typical circuit of the voltage dividing network S31, the resistor R1 and the capacitor C1 are connected in parallel, the resistor R2 and the capacitor C2 are connected in parallel, similarly, until the resistor Rn and the capacitor Cn are connected in parallel, and then all the parallel resistors and capacitors are connected in series. The unconnected end of the resistor R1 is a connection point P11, the common connection point of the resistor Rn-1 and the resistor Rn is P12, and the unconnected end of the resistor Rn is a connection point P13. The connection point P11 is connected to one end of the energy storage capacitor C1, and the connection point P13 is connected to the ground. The sampling voltage of the connection point P12 changes in real time according to the voltages at two ends of the energy storage capacitor C1.
As shown in fig. 6, the error amplifier and compensation network S32 typically includes resistors R21, R22, R23, capacitors C21, C22, C23, an operational amplifier N21, and a reference voltage Vref. After the resistor R21 and the capacitor C21 are connected in series, the resistor R22 is connected in parallel, one end of the parallel circuit is a connection point P21, and the other end of the parallel circuit is connected with the inverting input end of the operational amplifier N21. After the resistor R23 and the capacitor C23 are connected in series, the resistor R23 and the capacitor C22 are connected in parallel, one end of the parallel circuit is connected with the inverting input end of the operational amplifier N21, and the other end of the parallel circuit is connected with the output end of the operational amplifier N21. The reference voltage Vref is connected to the non-inverting input terminal of the operational amplifier N21, and the output terminal of the operational amplifier N21 is the connection point P22. The connection point P21 is connected to the connection point P12 in a typical circuit of the voltage dividing network S31.
As shown in fig. 7, the power amplifying circuit S33 typically includes an NPN transistor V31, a PNP transistor V32, an auxiliary voltage +15v, and-15V. The base of the triode V31 is connected with the base of the triode V32, and the connection point is P31. The collector of the triode V31 is connected with the auxiliary voltage +15V, and the collector of the triode V32 is connected with the auxiliary voltage-15V. The emitter of the triode V31 is connected with the emitter of the triode V32, and the connection point is P32. The connection point P31 is connected to the connection point P22 in the typical circuit of the error amplifier and compensation network S32, and the connection point P32 is connected to the gate of the adjusting switch tube in the adjusting switch S34. S33 amplifies the small signal sent by S32 to a power signal for driving the adjusting switch tube, and the purpose can be achieved by adopting a linear power amplifier.
As shown in fig. 8, the exemplary circuit of the regulating switch S34 includes a switch component K41, a capacitor component C41, a resistor component R41, and a transient suppression diode (TVS) component V41. The switch component K41 can adopt a single high-power switch or can adopt a plurality of low-power switches to be connected in parallel; the transient suppression diode component V41 can adopt a single high-voltage high-current TVS or can adopt a plurality of TVSs to be connected in series and parallel. After K41, C41, R41 and V41 are connected in parallel, one end serves as a connection point P41, and the other end serves as a connection point P42. The connection point P41 is connected with the other end of the energy storage capacitor, and the connection point P42 is connected with the microwave tube body.
As shown in fig. 9, the only difference from fig. 4 is that one end of the voltage dividing network S31 is connected to the cathode of the microwave tube, and the other end is connected to the ground. S31 samples the voltage at the output of the modulator Q1 relative to ground and supplies a sampled voltage of suitable magnitude to the error amplifier and compensation network S32. By adopting the circuit of fig. 4, the problem of deterioration of the stability of the transmitter radio frequency signal caused by power supply ripple and modulation pulse peak drop can be only improved; by adopting the circuit of fig. 9, the problem of deterioration of the stability of the transmitter radio frequency signal caused by power supply ripple and modulation pulse peak drop can be improved, and the problem of deterioration of the stability of the transmitting signal caused by inter-pulse instability of modulation pulse amplitude and intra-pulse peak fluctuation can be solved.
As shown in fig. 10, if the circuit of fig. 4 is used, the left graph is a schematic waveform of the sampled voltage in the voltage divider network, and the right graph is a schematic waveform of the reference voltage in the error amplifier and compensation network.
As shown in fig. 11, if the circuit of fig. 9 is used, the left graph is a schematic waveform of the sampled voltage in the voltage divider network, and the right graph is a schematic waveform of the reference voltage in the error amplifier and compensation network.
The working principle of the invention is as follows: the high-voltage power supply in the transmitter provides direct-current energy for the energy storage capacitor, the energy storage capacitor discharges the microwave tube through the modulator, and the microwave tube amplifies the radio-frequency signal. The low-frequency ripple wave, the high-frequency ripple wave, the noise generated by a switching device and the like caused by a high-voltage power supply and the top fluctuation and the top drop of a discharge pulse generated by a loop distribution parameter can generate amplitude modulation on the electron beam voltage of the microwave tube, so that the phase noise of the radio frequency signal output by the microwave tube is deteriorated.
The most significant factor affecting phase noise is the electric field that provides the initial velocity to the microwave beam, which is created by the voltage between the cathode and the tube. And the electron beam passing rate of the microwave tube is generally more than 80%, and the tube body current only accounts for 10% -20% of the total current of the discharge pulse.
According to the voltage amplitude change of the energy storage capacitor or the modulation pulse, the voltage drop of a tube body current adjusting circuit connected in series in the loop is adjusted in real time, so that the voltage between the cathode of the microwave tube and the tube body is kept constant, and the phase noise of the microwave tube can be effectively reduced under the condition of small efficiency loss of the transmitter.
Based on the invention, the transmitter remarkably reduces the requirements on a high-voltage power supply and a modulator, solves the problem of unstable pulse amplitude modulation, and the problem of deterioration of the stability of a transmitting signal caused by fluctuation of the top of the pulse and the pulse top drop, and can also improve the problem of deterioration of the stability of a radio-frequency signal of the transmitter caused by power supply ripple. The system has simple circuit, low voltage and power requirements on components, low cost, easy realization and small efficiency loss, and is suitable for various occasions.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and variations could be made by those skilled in the art without departing from the technical principles of the present invention, and such modifications and variations should also be regarded as being within the scope of the invention.
Claims (6)
1. The circuit for improving the stability of the emission signal is characterized by comprising a high-voltage power supply, an energy storage capacitor, a modulator, a microwave tube, a tube body current branch, a collector current branch and a tube body current adjusting circuit;
the high-voltage power supply is connected with the energy storage capacitor, the energy storage capacitor is connected with the modulator, and the modulator is connected with the cathode of the microwave tube; the tube body of the microwave tube is connected with a tube body current adjusting circuit, and the tube body current adjusting circuit is connected with a tube body current branch; the collector of the microwave tube is connected with the collector current branch; the tube body current branch and the collector current branch are respectively connected with the energy storage capacitor;
the high-voltage power supply charges the energy storage capacitor and provides constant direct-current high voltage; the energy storage capacitor stores high-voltage direct-current energy; when the modulator is closed, the energy storage capacitor can discharge the microwave tube through the modulator; the tube body current branch circuit, the collector current branch circuit and the tube body current adjusting circuit provide a current loop for modulator discharge;
the negative end of the high-voltage power supply E1 is respectively connected with one end of the energy storage capacitor C1 and one end of the modulator Q1; the other end of the modulator Q1 is connected with the cathode of the microwave tube; the tube body of the microwave tube is connected with one end of the tube body current adjusting circuit S3 and is connected with the ground; the other end of the tube body current adjusting circuit S3 is connected with one end of a tube body current branch S1; the collector of the microwave tube is connected with one end of a collector current branch S2; the other end of the tube body current branch S1 and the other end of the collector current branch S2 are commonly connected to the other end of the energy storage capacitor C1 and then connected with the positive end of the high-voltage power supply E1;
the tube body current adjusting circuit S3 is a closed loop system and comprises a voltage dividing network S31, an error amplifier and compensation network S32, a power amplifying circuit S33 and an adjusting switch S34; the voltage dividing network S31 is a voltage dividing circuit, one end of the voltage dividing circuit is connected with the negative end of the C1 or the cathode of the microwave tube, and the other end of the voltage dividing circuit is connected with the ground; s31, sampling the voltage of C1 relative to the ground, and sending the sampled voltage with proper magnitude to an error amplifier and compensation network S32; the error amplifier and compensation network S32 compares the sampling voltage sent by the S31 with a reference voltage Vref and outputs an error amplified signal; the power amplification circuit S33 amplifies the power of the error amplification signal sent from the compensation network S32, and sends the power amplified signal to the adjustment switch S34 as a driving signal of the adjustment switch; the adjusting switch S34 adopts an insulated gate bipolar transistor IGBT or a metal oxide semiconductor field effect transistor MOSFET as an adjusting switch tube, one end of the adjusting switch tube is connected with a tube body current branch, and the other end of the adjusting switch tube is connected with a tube body of the microwave tube.
2. A circuit for improving the stability of a transmitted signal according to claim 1, wherein the voltage dividing network S31 comprises voltage dividing resistors R1 to Rn and voltage dividing capacitors C1 to Cn; the resistor R1 and the capacitor C1 are connected in parallel, the resistor R2 and the capacitor C2 are connected in parallel, similarly, until the resistor Rn and the capacitor Cn are connected in parallel, and then all the resistors and the capacitors which are connected in parallel are connected in series in sequence; the unconnected end of the resistor R1 is a connection point P11, the common connection point of the resistor Rn-1 and the resistor Rn is P12, and the unconnected end of the resistor Rn is a connection point P13; the connection point P11 is connected with the negative end of the energy storage capacitor C1 or the cathode of the microwave tube, and the connection point P13 is connected with the ground; the sampling voltage of the connection point P12 changes in real time according to the voltages at two ends of the energy storage capacitor C1.
3. A circuit for improving the stability of a transmitted signal according to claim 1, characterized in that the error amplifier and compensation network S32 comprises resistors R21, R22, R23, capacitors C21, C22, C23, an operational amplifier N21 and a reference voltage Vref; after the resistor R21 and the capacitor C21 are connected in series, the resistor R22 is connected in parallel, one end of the parallel circuit is a connection point P21, and the other end of the parallel circuit is connected with the inverting input end of the operational amplifier N21; after the resistor R23 and the capacitor C23 are connected in series, the resistor R23 and the capacitor C22 are connected in parallel, one end of the parallel circuit is connected with the inverting input end of the operational amplifier N21, and the other end of the parallel circuit is connected with the output end of the operational amplifier N21; the reference voltage Vref is connected with the non-inverting input end of the operational amplifier N21, and the output end of the operational amplifier N21 is a connection point P22; the connection point P21 is connected to the connection point P12 in the circuit of the voltage dividing network S31.
4. The circuit for improving stability of a transmission signal according to claim 1, wherein the power amplifying circuit S33 comprises an NPN transistor V31, a PNP transistor V32, an auxiliary voltage +15v and-15V; the base electrode of the triode V31 is connected with the base electrode of the triode V32, and the connection point is P31; the collector of the triode V31 is connected with auxiliary voltage +15V, and the collector of the triode V32 is connected with auxiliary voltage-15V; the emitter of the triode V31 is connected with the emitter of the triode V32, and the connection point is P32; the connection point P31 is connected to the connection point P22 in the error amplifier and compensation network S32, and the connection point P32 is connected to the gate of the adjustment switch tube in the adjustment switch S34.
5. The circuit for improving the stability of a transmitted signal according to claim 1, wherein the adjusting switch S34 comprises a switch component K41, a capacitor component C41, a resistor component R41 and a transient suppression diode component V41; after the switch component K41, the capacitor component C41, the resistor component R41 and the transient suppression diode component V41 are connected in parallel, one end is used as a connection point P41, and the other end is used as a connection point P42; the connection point P41 is connected with the other end of the energy storage capacitor, and the connection point P42 is connected with the microwave tube body.
6. The circuit for improving the stability of a transmitted signal according to claim 5, wherein the switch assembly K41 is a single high-power switch or a plurality of low-power switches connected in parallel; the transient suppression diode assembly V41 is formed by connecting a single high-voltage high-current TVS or a plurality of TVSs in series-parallel connection.
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