X-band high-speed QPSK modulator suitable for spaceborne

Abstract

The invention discloses a satellite-borne X-band high-speed QPSK modulator, and the modulator comprises a power module which is used for providing + 5V, + 3V, + 12V and-5V input voltages, carrying out the filtering of the input voltages, and guaranteeing that a power supply provided for a subsequent circuit is clean and stable; the high-stability crystal oscillator module is used for providing a 40M clock with high reliability and stability for the 180-time phase-locked frequency doubling module; the 180-time phase-locked frequency doubling module outputs the frequency of the input signal in a frequency doubling manner to obtain higher frequency output; the first power amplification module is used for carrying out primary signal amplification on the signal subjected to 180-time phase-locking frequency multiplication; the interface and the driver receive external high-speed data, realize level conversion of high-speed data signals and then output the high-speed data signals to the X-band modulator; the X frequency band modulator is used for converting the digital signal into an analog signal; the second power amplification module is used for performing power amplification on the signal passing through the 180-time phase-locked frequency multiplication and the signal passing through the X-band modulator; and the isolator realizes signal isolation and converts and outputs the signal at the same time.

Description

Technical Field

[0001] The invention relates to the field of satellite communications, and in particular to an X-band high-speed QPSK modulator. Background Art

[0002] With the increase in the types of satellite payloads and the continuous improvement of resolution, the amount of information that needs to be transmitted is increasing. In order to transmit this information to the ground in real time, the requirements for the transmission capacity of the onboard data transmission system are getting higher and higher. The main ways to improve the transmission rate of the data transmission system on the existing basis are: 1. Change the modulation implementation form, that is, from the commonly used digital modulation to the form of direct RF modulation; 2. Change the modulation method, that is, from the commonly used QPSK modulation to a higher order modulation method to improve the utilization of the frequency band.

[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 shortcomings that are difficult to overcome. First, this method limits the maximum transmission rate of digital baseband signals. Secondly, the modulated signal will inevitably produce nonlinear distortion in the frequency conversion process. The third-order intermodulation distortion will cause spectrum diffusion and affect adjacent channels. The group delay characteristics and amplitude-frequency characteristics of the filter will also cause signal distortion. The use of direct microwave modulation and demodulation technology can meet the requirements of broadband channel transmission and reduce the impact of local carriers on the channel.

[0004] Patent search formula (QPSK+modulation) found 2 patent contents after searching, and two patents related to the present invention were retrieved, including:

[0005] 1) Patent No. CN 114978833 B, a QPSK modulation signal offset compensation method based on a combined modulation waveform, which mainly transfers the frequency offset and phase offset estimation of a simple QPSK modulation to the frequency offset estimation of MSK and the phase offset estimation of BPSK by generating a combined modulation waveform, which can effectively reduce the hardware resources consumed in realizing the frequency offset and phase offset estimation, and can calculate more accurate frequency offset and phase offset estimation values. The difference from the present invention is that the X-band modulator of the present invention is realized on the basis of an IQ double-balanced mixer, the device has improved accessibility, and the interface adopts a differential circuit form, which is convenient for module universalization and convenient for realizing higher-speed signal transmission. The universal 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, the microwave QPSK modulation circuit includes a carrier power division module, a first modulation module, a second modulation module and a modulation power division module. The difference from 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 frequency multiplier, an I / Q modulator, a signal level conversion and a power supply module. Summary of the invention

[0007] The object of the present invention is to provide an X-band high-speed QPSK modulator suitable for satellite-borne use. The X-band modulator of the present invention is implemented on the basis of an IQ double-balanced mixer, and the device has improved accessibility. At the same time, the interface adopts a differential circuit form, which is convenient for module universalization and for realizing higher-speed signal transmission. The universal circuit design can realize high-speed data modulation in various modulation modes.

[0008] The present invention provides a satellite-borne X-band high-speed QPSK modulator, comprising a power supply module, a high-stability crystal oscillator module, a 180-fold phase-locked frequency multiplication module, a first power amplifier module, an interface and a 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 filter the input voltages to ensure that the power provided to the subsequent circuits is clean and stable;

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

[0011] The 180-fold phase-locked frequency multiplication module obtains a higher frequency output by multiplying the frequency of the input signal;

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

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

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

[0015] The second power amplifier module is used to power amplify the signal that has passed through the 180-fold phase-locked frequency multiplication and the signal that has passed through the X-band modulator;

[0016] The isolator realizes signal isolation and converts the signal for output at the same time.

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

[0019] According to one embodiment of the present invention, the input port cascaded microwave amplifier is used to increase the power of the LO input port to 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; BPSK uses a passive double-balanced mixer as a phase modulation device, and uses the conduction and cutoff of the diode to make the transmission path of the microwave signal differ by λ / 2, thereby achieving a phase shift of 180°.

[0021] According to an embodiment of the present invention, after the local oscillator input signal is power-split, one path is subjected to 90° phase shift and then BPSK modulation, and the other path is directly subjected to BPSK modulation, and then the two modulated signals are synthesized with equal phases.

[0022] According to an embodiment of the present invention, the passive double-balanced mixer is used as a switch, and two intermediate frequency signals are used as switch control signals to control the on and off 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 the 0 and 1 states, the phase of the carrier is correspondingly flipped, and the implementation method is to convert the baseband signal into a bipolar signal and then implement it through a multiplier; the principle is as follows:

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

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

[0026] The beneficial effects of the present invention include: the X-band modulator of the present invention is realized on the basis of an IQ double-balanced mixer, the device has improved availability, and the interface adopts a differential circuit form, which is convenient for module universalization and convenient for realizing higher-speed signal transmission. The universal circuit design can realize high-speed data modulation of various modulation modes. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2 This is a schematic diagram of the X-band modulator circuit. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Figure 1 This is a diagram of the high-speed modulator, including power module, high-stability crystal oscillator, 180 times phase-locked frequency multiplication, interface and driver, X-band modulator, power amplifier and isolator. Its main function is to achieve the modulation rate of X-band high-speed modulator in 10Mbps-800Mbps. Within the full rate range, the amplitude imbalance is ≤1dB and the phase imbalance is ≤6°.

[0031] The function of the power module is to provide +5V, +3V, +12V and -5V input voltages, and filter the input voltage to ensure that the power provided to subsequent related circuits is clean and stable.

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

[0033] The function of 180 times phase-locked frequency multiplication is to obtain a higher frequency output by multiplying the frequency of the input signal.

[0034] The function of the interface and driver is to realize the level conversion of high-frequency data signals.

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

[0036] The function of the isolator is to achieve signal isolation and convert the signal for output.

[0037] The function of the X-band modulator is to convert digital signals into analog signals. 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 the microwave amplifier and used as the modulator local oscillator input 2. The differential signal input 1 is amplified by the low-pass filter 4 (DC-630MHz) and the differential amplifier 5 and sent to the intermediate frequency interface of the I / Q mixer 6 to realize QPSK modulation with the modulator local oscillator input 2. The modulated signal output 3 is output through the RF port.

[0039] 2. The cascaded microwave amplifier at the input port is used to increase the power of the LO input port to achieve the optimal local oscillator power input range of the I / Q mixer (≥+10dBm). The modulation method of each channel of the I / Q mixer 6 is BPSK, and the modulation signal is two channels. BPSK uses a passive double-balanced mixer 7 as a phase modulation device, and uses the conduction and cutoff of the diode to make the transmission path of the microwave signal differ by λ / 2, thereby achieving a 180° phase shift.

[0040] 3. After the local oscillator input signal is split, one path is phase-shifted by 90° and then BPSK modulated, and the other path is directly BPSK modulated, and then the two modulated signals are synthesized in equal phase. The passive double-balanced mixer 7 is used as a switch here, and the two intermediate frequency signals (high-speed code signals) are used as switch control signals to control the on and off of the RF signal. The implementation principle of single-branch BPSK modulation is that when the baseband signal changes between the 0 and 1 states, the phase of the carrier is flipped accordingly. The implementation method is to convert the baseband signal into a bipolar signal and then implement it through a multiplier. The principle is as follows:

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

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

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

Claims

1. An X-band high-speed QPSK modulator suitable for satellite-borne use, characterized in that: It includes a power supply module, a high-stability crystal oscillator module, a 180-fold phase-locked frequency multiplication module, a first power amplifier module, an interface and a driver, an X-band modulator, a second power amplifier module, and an isolator; wherein, The power module is used to provide +5V, +3V, +12V and -5V input voltages, and filter the input voltages to ensure that the power provided to the subsequent circuits is clean and stable; The high-stability crystal oscillator module is used to provide a highly reliable and stable 40M clock for the 180 times phase-locked frequency multiplication module; The 180-fold phase-locked frequency multiplication module obtains a higher frequency output by multiplying the frequency of the input signal; The first power amplifier module is used to amplify the signal that has been phase-locked and frequency-multiplied by 180 times; The interface and driver receive external high-speed data, and implement level conversion of the high-number data signal and then output it to the X-band modulator; The X-band modulator is used to convert the digital signal into an analog signal; The second power amplifier module is used to power amplify the signal that has passed through the 180-fold phase-locked frequency multiplication and the signal that has passed through the X-band modulator; The isolator realizes signal isolation and converts the signal for output at the same time.

2. The X-band high-speed QPSK modulator suitable for satellite use according to claim 1, characterized in that: 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, The local oscillator signal input is amplified by the cascaded microwave amplifier at the input port and used as the modulator local oscillator input; the differential signal input is amplified by the differential amplifier after passing through the low-pass filter and sent to the I / Q mixer intermediate frequency port to realize QPSK modulation with the modulator local oscillator input, and the modulated signal is output through the RF port.

3. The X-band high-speed QPSK modulator suitable for satellite use according to claim 2, characterized in that: The purpose of the input port cascade microwave amplifier is to increase the power of the LO input port and achieve the optimal local oscillator power input range of the I / Q mixer.

4. The X-band high-speed QPSK modulator suitable for satellite use according to claim 3, characterized in that: The modulation method of each channel of the I / Q mixer is BPSK, and there are two modulation signals; BPSK uses a passive double-balanced mixer as a phase modulation device, and uses the conduction and cutoff of the diode to make the transmission path of the microwave signal differ by λ / 2, thereby achieving a 180° phase shift.

5. The X-band high-speed QPSK modulator suitable for satellite use according to claim 4, characterized in that: After the local oscillator input signal is power-split, one path is phase-shifted by 90° and then BPSK modulated, and the other path is directly BPSK modulated. The two modulated signals are then synthesized with equal phases.

6. The X-band high-speed QPSK modulator suitable for satellite use according to claim 5, characterized in that: The passive double-balanced mixer is used as a switch here, and the two intermediate frequency signals are used as switch control signals to control the on and off of the RF signal.

7. The X-band high-speed QPSK modulator suitable for satellite use according to claim 6, characterized in that: The implementation principle of single-branch BPSK modulation is that when the baseband signal changes between 0 and 1, the phase of the carrier is flipped accordingly. The implementation method is to convert the baseband signal into a bipolar signal and then implement it through a multiplier; the principle is as follows: 1 state: cos(wt)1*cos(wt) 0 state: cos(wt+)-1*cos(wt).

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