X-band high-speed QPSK modulator suitable for satellite

Abstract

A kind of X frequency band high-speed QPSK modulator suitable for spaceborne, comprising: power module is used to provide +5V, +3V, +12V and-5V input voltage, while filtering input voltage, ensure that the power provided for subsequent circuit use is clean and stable;High-stability crystal oscillator module is used to provide high-reliability stable 40M clock for 180 times phase-locked frequency multiplication module;180 times phase-locked frequency multiplication module obtains higher frequency output by frequency multiplication to input signal frequency;First power amplifier module is used to amplify the signal through 180 times phase-locked frequency multiplication once;Interface and drive receive external high-speed data, and realize high number data signal level conversion and then output to X frequency band modulator;X frequency band modulator is used to convert digital signal into analog signal;Second power amplifier module is used to power amplify the signal through 180 times phase-locked frequency multiplication and the signal through X frequency band modulator;Isolator realizes signal isolation while converting and outputting signal.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of satellite communication, in particular to an X-band high-speed QPSK modulator. BACKGROUND

[0002] With the increase of the types of satellite payloads and the continuous improvement of the resolution, the amount of information to be transmitted is increasing. In order to transmit these information to the ground in real time, the transmission capacity of the on-board data transmission system is required to be higher and higher. The main ways to improve the transmission rate of the data transmission system on the basis of the existing ones are: 1. Changing the modulation implementation form, i.e. changing from the commonly used digital modulation to the form of direct radio frequency modulation; 2. Changing the modulation mode, i.e. changing from the commonly used QPSK modulation to a higher order modulation mode to improve the frequency band utilization.

[0003] Traditional microwave transceivers basically adopt the scheme of intermediate frequency modulation and then up-conversion to the microwave frequency band. The intermediate frequency modulator is easy to design and manufacture, and has high reliability. However, this scheme also has its insurmountable shortcomings. First of all, this method limits the highest transmission rate of the digital baseband signal. Secondly, the modulated signal inevitably produces nonlinear distortion in the frequency conversion process, and the third-order intermodulation distortion will lead to spectrum spreading, affecting the adjacent frequency channels. The group delay characteristic and amplitude-frequency characteristic of the filter will also cause signal distortion. Using direct microwave modulation and demodulation technology can meet the transmission requirements of wide frequency band channels and reduce the influence of the local carrier on the channel.

[0004] Patent search formula (QPSK+modulation) found 2 pieces of patent content, 2 pieces of patents related to the present application were searched, including:

[0005] 1) Patent No. CN 114978833 B, a QPSK modulation signal offset compensation method based on combined modulation waveform, which is mainly through the generation of combined modulation waveform, the frequency offset and phase offset estimation of pure QPSK modulation is transferred to the frequency offset estimation of MSK and the phase offset estimation of BPSK, which can effectively reduce the resources consumed by hardware in the implementation of frequency offset and phase offset estimation, and can calculate more accurate frequency offset and phase offset estimation value. The difference between the present application and the present application is that the X-band modulator of the present application is realized on the basis of the IQ double balanced mixer, the device has improved performance, and the interface adopts differential circuit form, which is convenient for module generalization and realization of higher speed signal transmission. The general circuit design can realize high-speed data modulation of various modulation modes.

[0006] 2) Patent No. CN 110035026 A, Microwave QPSK Modulation Circuit and Electronic Equipment, wherein the microwave QPSK modulation circuit includes a carrier power divider module, a first modulation module, a second modulation module, and a modulation power divider module. The difference between this invention and the present invention is that the X-band high-speed QPSK modulation circuit of the present invention includes a high-stability crystal oscillator, a phase-locked loop frequency multiplier, an I / Q modulator, a signal level converter, and a power supply module. Summary of the Invention

[0007] The purpose of this invention is to provide a high-speed QPSK modulator for the X-band suitable for spaceborne applications. This X-band modulator is implemented based on an IQ double-balanced mixer, improving device availability. Furthermore, the interface uses a differential circuit, facilitating module standardization and enabling higher-speed signal transmission. The standardized circuit design allows for high-speed data modulation using various modulation methods.

[0008] This invention provides a high-speed X-band QPSK modulator suitable for spaceborne applications, comprising a power supply module, a high-stability crystal oscillator module, a 180x phase-locked loop frequency multiplier module, a first power amplifier module, an interface and driver, an X-band modulator, a second power amplifier module, and an isolator; wherein,

[0009] The power module is used to provide +5V, +3V, +12V and -5V input voltages, and at the same time filters the input voltages to ensure that the power supplied to the subsequent circuits is clean and stable.

[0010] The high-stability crystal oscillator module is used to provide a highly reliable and stable 40MHz clock for the 180x phase-locked loop frequency multiplier module;

[0011] The 180x phase-locked frequency multiplier module multiplies the frequency of the input signal to obtain a higher frequency output.

[0012] The first power amplifier module is used to amplify the signal that has been multiplied by 180 times phase-locked loop frequency once;

[0013] The interface and driver receive external high-speed data and output it to the X-band modulator after high-speed data signal level conversion;

[0014] The X-band modulator is used to convert digital signals into analog signals;

[0015] The second power amplifier module is used to amplify the power of the signal that has been multiplied by 180 times phase-locked loop and the signal that has been multiplied by the X-band modulator;

[0016] The isolator achieves signal isolation while simultaneously converting and outputting the signal.

[0017] According to one embodiment of the present invention, the X-band modulator includes a local oscillator signal input, a differential signal input, a modulator local oscillator input, a modulated signal output, a low-pass filter, a differential amplifier, an I / Q mixer, and a passive double-balanced mixer; wherein,

[0018] The local oscillator signal input is amplified by a cascaded microwave amplifier at the input port and then used as the local oscillator input of the modulator. The differential signal input is amplified by a differential amplifier after passing through a low-pass filter and then sent to the intermediate frequency port of the I / Q mixer to achieve QPSK modulation with the local oscillator input of the modulator. The modulated signal is then output through the RF port.

[0019] According to one embodiment of the present invention, a cascaded microwave amplifier at the input port is used to increase the power of the LO input port and achieve the optimal local oscillator power input range of the I / Q mixer.

[0020] According to one embodiment of the present invention, the modulation method of each channel of the I / Q mixer is BPSK, and there are two modulation signals. The BPSK uses a passive double-balanced mixer as the phase modulation device. By using the conduction and cutoff of the diode, the transmission paths of the microwave signals are phased by λ / 2, thereby achieving a phase shift of 180°.

[0021] According to one embodiment of the present invention, after the local oscillator input signal is power divided, one path is phase-shifted by 90° and then BPSK modulated, while the other path is directly BPSK modulated. Then, the two modulated signals are synthesized in equal phase.

[0022] According to one embodiment of the present invention, the passive double-balanced mixer is used as a switch, and the two intermediate frequency signals are used as switch control signals to control the on / off state of the radio frequency signal.

[0023] According to one embodiment of the present invention, the implementation principle of single-branch BPSK modulation is that when the baseband signal changes between 0 and 1 states, the phase of the carrier wave flips accordingly. This is achieved by converting the baseband signal into a bipolar signal and then using a multiplier. The principle is as follows:

[0024] State 1: cos(wt)1*cos(wt)

[0025] State 0: cos(wt+)-1*cos(wt).

[0026] The beneficial effects of this invention include: the X-band modulator is implemented based on an IQ double-balanced mixer, improving device availability; and the interface uses a differential circuit, facilitating module standardization and enabling higher-speed signal transmission. The use of a universal circuit design allows for high-speed data modulation using various modulation methods. Attached Figure Description

[0027] Figure 1This is a diagram of a high-speed modulator.

[0028] Figure 2 This is a schematic diagram of an X-band modulator circuit. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Figure 1 This diagram shows the components of a high-speed modulator, including a power supply module, a high-stability crystal oscillator, a 180x phase-locked loop frequency multiplier, interfaces and drivers, an X-band modulator, a power amplifier, and an isolator. Its main function is to achieve a modulation rate of 10Mbps-800Mbps for the X-band high-speed modulator. Amplitude imbalance ≤1dB and phase imbalance ≤6° across the entire rate range.

[0031] The power module provides +5V, +3V, +12V and -5V input voltages, and filters the input voltages to ensure that the power supplied to subsequent circuits is clean and stable.

[0032] The purpose of the high-stability crystal oscillator is to provide a highly reliable and stable 40MHz clock for the 180x phase-locked loop frequency multiplication.

[0033] The purpose of a 180x phase-locked loop frequency multiplier is to obtain a higher frequency output by multiplying the frequency of the input signal.

[0034] The role of the interface and driver is to realize the conversion of high-order data signal levels.

[0035] The function of the power amplifier is to amplify the power of the signal that has passed through the 180-fold phase-locked loop frequency multiplier and the signal that has passed through the X-band modulator.

[0036] The function of an isolator is to isolate signals while converting and outputting them.

[0037] The function of an X-band modulator is to convert digital signals into analog signals. Its circuitry is as follows: Figure 2 As shown, it includes: local oscillator signal input 0, differential signal input 1, modulator local oscillator input 2, modulated signal output 3, low-pass filter 4, differential amplifier 5, I / Q mixer 6, and passive double-balanced mixer 7.

[0038] 1. The local oscillator signal input 0 is amplified by a microwave amplifier and used as the local oscillator input 2 of the modulator. The differential signal input 1 is amplified by a differential amplifier 5 after passing through a low-pass filter 4 (DC-630MHz) and then sent to the intermediate frequency port of the I / Q mixer 6 to achieve QPSK modulation with the local oscillator input 2 of the modulator. The modulated signal is output 3 via the RF port.

[0039] 2. The cascaded microwave amplifier at the input port is used to increase the power of the LO input port, achieving the optimal local oscillator power input range (≥ +10dBm) for the I / Q mixer. Each channel of the I / Q mixer 6 uses BPSK modulation, with two modulation signals. The BPSK uses a passive double-balanced mixer 7 as the phase-shifting device, utilizing the switching on and off of diodes to make the microwave signal transmission paths differ in phase by λ / 2, thus achieving a 180° phase shift.

[0040] 3. After the local oscillator input signal is power-divided, one path undergoes a 90° phase shift before BPSK modulation, while the other path is directly BPSK modulated. The two modulated signals are then combined in equal phase. The passive double-balanced mixer 7 is used as a switch here, with the two intermediate frequency signals (high-speed code signals) serving as switch control signals to control the on / off state of the radio frequency signal. The principle of single-branch BPSK modulation is that when the baseband signal changes between 0 and 1 states, the carrier phase flips accordingly. This is achieved by converting the baseband signal into a bipolar signal and then using a multiplier. The principle is as follows:

[0041] State 1: cos(wt)1*cos(wt)

[0042] State 0: cos(wt+)-1*cos(wt)

[0043] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A high-speed QPSK modulator for spaceborne X-band, characterized in that, It includes a power supply module, a high-stability crystal oscillator module, a 180x phase-locked loop frequency multiplier module, a first power amplifier module, interfaces and drivers, an X-band modulator, a second power amplifier module, and an isolator; among which, The power module is used to provide +5V, +3V, +12V and -5V input voltages, and at the same time filters the input voltages to ensure that the power supplied to the subsequent circuits is clean and stable. The high-stability crystal oscillator module is used to provide a highly reliable and stable 40MHz clock for the 180x phase-locked loop frequency multiplier module; The 180x phase-locked frequency multiplier module multiplies the frequency of the input signal to obtain a higher frequency output. The first power amplifier module is used to amplify the signal that has been multiplied by 180 times phase-locked loop frequency once; The interface and driver receive external high-speed data and output the high-speed data signal level to the X-band modulator after high-speed data signal level conversion. The X-band modulator is used to convert digital signals into analog signals; The second power amplifier module is used to amplify the power of the signal that has been multiplied by 180 times phase-locked loop and the signal that has been multiplied by the X-band modulator; The isolator achieves signal isolation while simultaneously converting and outputting the signal; The X-band modulator includes a local oscillator signal input, a differential signal input, a modulator local oscillator input, a modulated signal output, a low-pass filter, a differential amplifier, and an I / Q mixer, wherein the I / Q mixer includes a passive double-balanced mixer; wherein... The local oscillator signal input is amplified by a cascaded microwave amplifier at the LO input port and then used as the local oscillator input of the modulator. The differential signal input is amplified by a differential amplifier after passing through a low-pass filter and then sent to the intermediate frequency port of the I / Q mixer to achieve QPSK modulation with the local oscillator input of the modulator. The modulated signal is then output through the RF port.

2. The X-band high-speed QPSK modulator suitable for spaceborne applications according to claim 1, characterized in that, A cascaded microwave amplifier at the input port increases the power of the LO input port, achieving the optimal local oscillator power input range for the I / Q mixer.

3. The X-band high-speed QPSK modulator suitable for spaceborne applications according to claim 2, characterized in that, The I / Q mixer uses BPSK modulation for each channel, with two modulation signals. BPSK uses a passive double-balanced mixer as the phase modulation device, which uses the conduction and cutoff of diodes to make the transmission paths of microwave signals differ by λ / 2, thereby achieving a 180° phase shift.

4. The X-band high-speed QPSK modulator suitable for spaceborne applications according to claim 3, characterized in that, After the local oscillator input signal is power divided, one path is phase-shifted by 90° and then BPSK modulated, while the other path is directly BPSK modulated. The two modulated signals are then synthesized in equal phase.

5. The X-band high-speed QPSK modulator suitable for spaceborne applications according to claim 4, characterized in that, The passive double-balanced mixer is used as a switch here, with two intermediate frequency signals serving as switch control signals to control the on / off state of the radio frequency signal.

6. The X-band high-speed QPSK modulator suitable for spaceborne applications according to claim 5, characterized in that, The principle of single-branch BPSK modulation is that when the baseband signal changes between 0 and 1 states, the phase of the carrier wave flips accordingly. This is achieved by converting the baseband signal into a bipolar signal and then using a multiplier. The principle is as follows: State 1: 1*cos(wt) State 0: -1*cos(wt).

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