A miniaturized integrated measurement, control and data transmission terminal

Abstract

This invention belongs to the field of aerospace telemetry, tracking, and command (TT&C) and communication technology, and particularly relates to a miniaturized integrated TT&C and data transmission terminal. The terminal includes a baseband processing unit, a single local oscillator (LOO) generation unit, a transmit link, and a receive link. The terminal does not include secondary or higher analog frequency conversion links. The frequency of the LOO signal satisfies a unified sampling constraint relationship with the frequency of the transmitted analog low-IF signal and the frequency of the received analog high-IF signal. The frequency of the transmitted analog low-IF signal is located within the first Nyquist sampling interval of the digital-to-analog converter (DAC). The frequency of the received analog high-IF signal is located within the second or third Nyquist sampling interval of the DAC, and after undersampling by the DAC, a received digital IF signal is formed. This invention, while ensuring high reliability of TT&C and high energy efficiency of data transmission, achieves a reduction in the size, weight, and power consumption of the spacecraft terminal, providing a lightweight communication solution for microsatellites and deep space probes.

Description

Technical Field

[0001] This invention belongs to the field of aerospace telemetry, measurement and control and communication technology, and in particular relates to a miniaturized telemetry, measurement and control data transmission integrated terminal. Background Technology

[0002] In modern space missions, to ensure comprehensive monitoring and high-speed data transmission during spacecraft operation in orbit, spacecraft typically need to have both telemetry and data transmission modes. The telemetry and data transmission mode mainly works with ground stations to perform functions such as remote control, telemetry, ranging, velocity measurement, and orbit determination, so as to keep track of the spacecraft's orbital parameters and operational status in real time. The data transmission mode is used to perform on-orbit reconfiguration and other information uploading, as well as high-speed backhaul of spacecraft status information and on-orbit sensing information.

[0003] However, in conventional system design, telemetry, tracking and data transmission functions are usually implemented by two separate sets of physical equipment. Each set of equipment requires independent configuration of radio frequency modules, signal processing modules and secondary power supplies, which increases the weight, size, power consumption and interface resource usage of spacecraft, making it difficult to meet the growing demand for miniaturization, lightweighting and low power consumption of modern spacecraft.

[0004] Furthermore, due to the difference in operating frequency bands between the telemetry and control mode and the data transmission mode, traditional solutions require the use of four or more frequency synthesizers to generate different local oscillator signals to meet the frequency conversion requirements of telemetry and control reception, telemetry and control transmission, data transmission reception, and data transmission transmission. This increases the complexity of the hardware circuitry and becomes a key obstacle restricting the miniaturization of the equipment. In addition, up to six transceiver antennas are usually required externally, which further increases the complexity and overall weight of the spacecraft system.

[0005] When attempting to reduce the number of local oscillators and share local oscillator resources, it is also necessary to address the image suppression problem. If a single local oscillator frequency is simply set near the center frequency of the telemetry and control transmitter and the data transmission transmitter, the low intermediate frequency of the telemetry and control transmitter and the low intermediate frequency of the data transmission may be symmetrically distributed relative to the local oscillator frequency, which in turn leads to a symmetrical distribution of their image components, increasing the difficulty of image suppression and spectrum isolation design.

[0006] Meanwhile, the performance requirements of power amplifiers differ between measurement and control signals and data transmission signals. Measurement and control signals require power amplifiers to operate in the high linear region to ensure signal quality, while data transmission signals require power amplifiers to operate in the high efficiency region to improve energy utilization. Traditional solutions usually require separate measurement and control power amplifiers and data transmission power amplifiers to meet these different requirements, which has become a bottleneck restricting further miniaturization of equipment.

[0007] Therefore, there is an urgent need for an integrated terminal that can take into account both telemetry and data transmission functions. Under the condition of predetermined telemetry and data transmission frequency points, by planning the single local oscillator frequency, processing the high-frequency and mid-frequency undersampling in the receiver, and designing a shared transmission link, the number of independent devices, frequency sources, frequency conversion links, power amplifiers and antenna interfaces can be reduced, thereby reducing the size, weight, power consumption and system complexity of the spacecraft terminal. Summary of the Invention

[0008] To address the technical challenges of traditional measurement, control, and data transmission systems in miniaturization design, such as high hardware resource consumption, numerous and complex frequency sources and analog frequency conversion links, and the difficulty in balancing multi-mode hardware multiplexing with signal quality and energy efficiency, this invention proposes a miniaturized integrated measurement, control, and data transmission terminal.

[0009] This invention is achieved through the following technical solution:

[0010] A miniaturized integrated measurement, control, and data transmission terminal includes:

[0011] The baseband processing unit is used to generate a transmit digital low-IF signal of the corresponding frequency according to the current operating mode, and to analyze the receive digital intermediate frequency signal.

[0012] A single local oscillator (LOO) generation unit, connected to the baseband processing unit, is used to provide a unique and constant frequency LOO signal; wherein the frequency of the LOO signal deviates from the preset center frequency positions of the measurement and control transmission radio frequency point and the data transmission radio frequency point.

[0013] The transmission link includes a digital-to-analog converter, a primary upconverter, and a shared broadband power amplifier cascaded together. The digital-to-analog converter converts the transmitted digital low-IF signal into a transmitted analog low-IF signal. The primary upconverter performs a primary upconversion between the transmitted analog low-IF signal and the single local oscillator signal. The shared broadband power amplifier has a working bandwidth covering the measurement and control transmission radio frequency point and the data transmission radio frequency point, and amplifies the signal after the primary upconversion to obtain the target radio frequency transmission signal.

[0014] The receiving link includes a receiving primary downconverter and an analog-to-digital converter cascaded in sequence; the receiving primary downconverter is used to perform a primary downconversion on the input radio frequency received signal and the same single local oscillator signal to obtain a received analog high-frequency signal;

[0015] The terminal does not contain secondary or higher analog frequency conversion links, and the frequency of the single local oscillator signal satisfies a unified sampling constraint relationship with the frequency of the transmitted analog low-IF signal and the frequency of the received analog high-IF signal.

[0016] The frequency of the transmitted analog low-IF signal is entirely within the first Nyquist sampling interval of the digital-to-analog converter;

[0017] The frequency of the received analog intermediate frequency signal is located within the second or third Nyquist sampling interval of the analog-to-digital converter. After being undersampled by the analog-to-digital converter, it is folded into the first Nyquist sampling interval without in-band aliasing, thus forming the received digital intermediate frequency signal.

[0018] Furthermore, the frequency of the single local oscillator signal The following asymmetric constraints must be satisfied:

[0019] ;

[0020] in, For measurement and control transmission radio frequency points, Number of transmission radio frequency points;

[0021] By making the frequency of the single local oscillator signal deviate from the center frequency position of the measurement and control radio frequency point and the data transmission radio frequency point, the image frequency corresponding to the measurement and control radio frequency transmission signal and the image frequency corresponding to the data transmission radio frequency transmission signal do not coincide symmetrically.

[0022] Furthermore, the baseband processing unit is internally configured with a digital predistortion module, which is used to perform predistortion processing on the transmitted digital low-IF signal input to the shared broadband power amplifier according to the current operating mode.

[0023] When the current working mode is the measurement and control transmission mode, the digital predistortion module calls the first predistortion coefficient to compensate for the amplitude and phase of the measurement and control radio frequency transmission signal, so that the measurement and control radio frequency transmission signal output by the shared broadband power amplifier meets the preset linearity requirements.

[0024] When the current working mode is data transmission mode, the digital predistortion module calls the second predistortion coefficient to compensate for the amplitude and phase of the data transmission radio frequency transmission signal, so that the data transmission radio frequency transmission signal output by the shared broadband power amplifier meets the preset efficiency and spectrum index requirements.

[0025] Furthermore, the radio frequency received signal includes a measurement and control radio frequency received signal and a data transmission radio frequency received signal;

[0026] The measurement and control radio frequency received signal is down-converted by the receiving downconverter to generate a measurement and control received analog high-frequency signal. The measurement and control received analog high-frequency signal is completely located within the third Nyquist sampling interval of the analog-to-digital converter.

[0027] The data transmission radio frequency received signal is down-converted by the receiving downconverter to generate a data transmission received analog high frequency signal. The data transmission received analog high frequency signal is completely located within the second Nyquist sampling interval of the analog-to-digital converter.

[0028] Furthermore, the digital intermediate frequency signal of the telemetry and control receiving analog high-frequency signal, which is folded after undersampling, and the digital intermediate frequency signal of the data transmission receiving analog high-frequency signal, which is folded after undersampling, both have frequency bands within the first Nyquist sampling interval and do not have any spectral overlap.

[0029] Furthermore, the baseband processing unit generates a transmit digital low-IF signal corresponding to the current operating mode in the digital domain, and under the condition that the frequency of the single local oscillator signal remains constant, realizes the switching between the measurement and control transmission radio frequency point and the data transmission radio frequency point at the radio frequency end.

[0030] Furthermore, the operating bandwidth of the shared broadband power amplifier simultaneously covers both the measurement and control radio frequency point and the data transmission radio frequency point, and the terminal's transmission link amplifies the power of the measurement and control radio frequency transmission signal and the data transmission radio frequency transmission signal in a time-division manner through the shared broadband power amplifier.

[0031] The beneficial effects of this invention are:

[0032] (1) The present invention can realize all functions of remote control, telemetry, distance measurement, speed measurement and data transmission with only one integrated measurement and control data transmission terminal, which greatly reduces the overall size and weight of the terminal and reduces power consumption. At the same time, it reduces the number of external supporting antennas from six to three, significantly improving the system hardware complexity and space resource utilization.

[0033] (2) Based on the typical radio frequency points of measurement and control and data transmission, the present invention makes reasonable planning so that the single local oscillator generation unit only needs to provide a single local oscillator signal with a constant frequency, which greatly reduces the number of frequency synthesizers used; by making the frequency of the single local oscillator signal deviate from the absolute center frequency position of the radio frequency point of measurement and control and data transmission, the influence of symmetrical image interference components on the target transmission radio frequency band is reduced from the source; at the same time, in conjunction with the baseband processing unit, a transmit digital low intermediate frequency signal with frequency jump is generated in the digital domain, and under the premise of constant single local oscillator frequency, flexible switching between different working frequencies of the radio frequency end is realized, so that the terminal does not contain secondary or higher analog frequency conversion links, simplifying the analog radio frequency circuit and eliminating the locking delay caused by frequency conversion;

[0034] (3) The present invention completely restricts the analog low-IF signal of the transmitting end to the first Nyquist sampling interval of the digital-to-analog converter to meet the output requirements; at the same time, the high-IF signal generated by the receiving end through one down-conversion is precisely planned in the second or third high-order Nyquist sampling interval of the analog-to-digital converter, so that the undersampling technology of the analog-to-digital converter can be used to completely fold it to the digital IF position in the first Nyquist sampling interval without in-band aliasing. Moreover, the frequency band of the digital IF signal received by the measurement and control and the frequency band of the digital IF signal received by the data transmission do not overlap in the first Nyquist sampling interval, which effectively reduces the design difficulty of the image rejection filter of the receiving circuit and overcomes the hardware bottleneck limitation of the high frequency band on the high sampling rate of the ADC / DAC under the single local oscillator architecture.

[0035] (4) The present invention is simplified in hardware to a single shared broadband power amplifier, and a differentiated digital predistortion strategy is configured in the front-end baseband processing unit for the measurement and control signal and the data transmission signal. When in the measurement and control transmission mode, the first predistortion coefficient is called to adjust the peak-to-average power ratio and amplitude distribution of the input signal so that the power amplifier works in the preset high linearity region. When in the data transmission transmission mode, the second predistortion coefficient is called to adjust the characteristics of the input signal so that the power amplifier works in the preset high efficiency region. Thus, under the condition of sharing a single power amplifier, the high quality transmission of the measurement and control signal and the high energy utilization of the data transmission signal are taken into account, and the system software-defined radio architecture integration is improved.

[0036] In summary, this invention features a single-system, single-local oscillator, single-power amplifier, and three-antenna architecture. It not only avoids the image crosstalk and high sampling rate bottlenecks that are prone to occur with single-local oscillators, but also achieves a significant reduction in the size, weight, and power consumption of spacecraft terminals while ensuring high reliability of telemetry and control and high energy efficiency of data transmission. This provides a lightweight communication solution for microsatellites and deep space probes. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the overall structure of a miniaturized integrated measurement, control, and data transmission terminal proposed in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the single local oscillator frequency synthesizer structure of a miniaturized measurement and control integrated data transmission terminal proposed in an embodiment of the present invention;

[0040] Figure 3This is a schematic diagram of the single local oscillator design frequency band planning for a miniaturized integrated measurement, control, and data transmission terminal proposed in an embodiment of the present invention;

[0041] Figure 4 This is a schematic diagram of the FPGA processing unit structure of a miniaturized measurement and control data transmission integrated terminal proposed in an embodiment of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0043] Example 1

[0044] refer to Figure 1 This embodiment provides a small integrated measurement and control data transmission terminal, which consists of three parts: a radio frequency (RF) module, a signal processing module, and a secondary power supply. The RF module includes a combiner, a filter, a low-noise amplifier, a power divider, a crystal oscillator, a receiving primary downconverter (e.g., a receiving intermediate frequency primary downconverter unit) forming part of the receiving link, a transmitting primary upconverter (e.g., a transmitting primary upconverter unit) forming part of the transmitting link, a single local oscillator frequency synthesizer (as a single local oscillator generation unit), and a power management unit, etc., used to perform functions such as combining, filtering, amplifying, and performing intermediate frequency primary downconversion of the RF received signal, upconversion and amplification of the transmitted signal, and generating the local oscillator signal.

[0045] The signal processing module consists of an undersampled analog-to-digital converter (ADC) as an analog-to-digital converter (ADC), a digital-to-analog converter (DAC) as a digital-to-analog converter (DAC), an FPGA processing unit as a baseband processing unit, an interface unit, a clock unit, and a power management unit. It is connected to the receiving high-frequency downconversion unit, the transmitting upconversion unit, and the crystal oscillator, respectively, to complete functions such as analog-to-digital / digital-to-analog conversion, baseband signal processing, differential control and pre-compensation of different modes of transmitted signals through an internal digital predistortion module, interaction with other modules, and mode control. The secondary power supply is connected to the RF module and the signal processing module respectively to provide a stable and reliable operating power for each functional unit.

[0046] In addition, to complete the reception and transmission of radio frequency signals, the terminal needs to be equipped with corresponding transceiver antennas, including one telemetry and control receiving antenna to the sky, one telemetry and control / data transmission receiving antenna to the ground, and one telemetry and control / data transmission transmitting antenna, for a total of three antennas. The transceiver antennas are interconnected with the radio frequency module interface to complete the input and output of radio frequency module signals.

[0047] In this embodiment, the miniaturized integrated measurement, control, and data transmission terminal operates as follows:

[0048] 1) Power-on initialization

[0049] After the terminal is powered on, the secondary power supply generates the operating power required by the radio frequency module and the signal processing module, and the device completes power-on and initialization.

[0050] 2) Clock and local oscillator signal generation

[0051] The crystal oscillator outputs a reference clock in the RF module, which is supplied to the clock unit of the signal processing module and the single-local oscillator frequency synthesizer of the RF module. The clock unit of the signal processing module generates the operating clocks required by the ADC, DAC, and FPGA processing units based on the reference clock. The single-local oscillator frequency synthesizes frequencies based on the reference clock to generate a single-local oscillator signal, the frequency of which is denoted as [missing information]. The single local oscillator signal is used simultaneously for receiving a down-conversion and transmitting a up-conversion signal in both measurement and control and data transmission modes. The structure of the single local oscillator frequency synthesizer is as follows: Figure 2 As shown, the single local oscillator frequency synthesizer includes a frequency and phase detector, a charge pump, a low-pass filter, a voltage-controlled oscillator (VCO), and a frequency divider. The reference clock is connected to the frequency and phase detector as an input signal. The output of the frequency and phase detector is connected to the input of the charge pump. The output of the charge pump is connected to the input of the low-pass filter. The output of the low-pass filter is connected to the input of the VCO, which outputs a single local oscillator signal. Simultaneously, the output of the VCO is also connected to the input of the frequency divider, and the output of the frequency divider is fed back to the frequency and phase detector.

[0052] The reference clock output from the crystal oscillator in the RF module not only provides the clock unit of the signal processing module with a working clock, but also serves as a reference signal input to the frequency and phase detector. This reference clock is phase-detected with the signal fed back by the frequency divider. The generated error signal is processed sequentially by the charge pump and the low-pass filter, and then controls the voltage-controlled oscillator to lock and output a single local oscillator signal. This single local oscillator signal is simultaneously provided to the system's transmit and receive channels, uniformly meeting the single-transmit frequency conversion requirements in the measurement and control and data transmission modes.

[0053] In this embodiment, the single local oscillator frequency It is necessary to uniformly plan based on the measurement and control transmission frequency, data transmission transmission frequency, measurement and control reception frequency, data transmission reception frequency, ADC undersampling constraints, and DAC sampling constraints, through... The reasonable selection of signals enables the same single local oscillator signal to simultaneously meet the primary frequency conversion requirements of four channels: telemetry and control transmission, data transmission, telemetry and control reception, and data reception. It also enables the receiving side to form a high-frequency signal suitable for undersampled ADC processing, and the transmitting side to form a low-frequency signal suitable for DAC output.

[0054] Specifically, such as Figure 3 As shown, the single local oscillator frequency Located at a preset frequency position between the measurement and control transmission radio frequency point and the data transmission radio frequency point, the The selection is not based on the strict center frequency of the two, but is determined by comprehensively considering the low intermediate frequency of telemetry and control transmission, the low intermediate frequency of data transmission, the high intermediate frequency of telemetry and control reception, the high intermediate frequency of data transmission reception, the DAC output bandwidth, the undersampling processing capability of the ADC, and the image rejection constraint.

[0055] like lie in and The center frequency position, then the telemetry and control transmission low intermediate frequency and the data transmission low intermediate frequency relative to the center frequency position, then the telemetry and control transmission low intermediate frequency relative to the center frequency position. The symmetrical distribution of these signals can easily lead to a symmetrical distribution of the image components of the telemetry and control RF transmission signals and the data transmission RF transmission signals, thus increasing the difficulty of image suppression and spectrum isolation design. Therefore, this embodiment will... The asymmetric preset frequency position between the two is set to reduce the influence of the symmetric mirror component on the target transmission frequency band.

[0056] Under the above overall frequency planning principles, the frequency planning for the four types of channels—telemetry and control transmission, data transmission, telemetry and control reception, and data reception—is as follows:

[0057] a) For the measurement and control radio frequency transmission signal, the FPGA processing unit generates the corresponding I / Q complex low-IF signal on the baseband side. The frequency of this complex low-IF signal is:

[0058]

[0059] The measurement and control transmission I / Q complex low-IF signal, after being output by the DAC, enters the transmission primary up-conversion unit and undergoes a primary up-conversion with the single local oscillator signal to obtain the measurement and control transmission radio frequency signal. The center frequency and signal bandwidth of the measurement and control transmission I / Q complex low-IF signal should be set within the first Nyquist sampling interval of the DAC.

[0060] b) For the data transmission RF signal, the FPGA processing unit generates the corresponding I / Q complex low-IF signal on the baseband side. (Note: The last part, "data transmission RF point," appears to be an unrelated fragment and is omitted from the translation.) With measurement and control transmission frequency point Located at the single local oscillator frequency The low-IF frequency corresponding to the data transmission on different sides can be expressed as:

[0061]

[0062] when At that time, the As a negative frequency component, the data transmission I / Q complex low intermediate frequency signal is output by the DAC and then enters the transmission upconversion unit, and is upconverted once with the single local oscillator signal to obtain the data transmission radio frequency signal. The center frequency and signal bandwidth of the data transmission I / Q complex low intermediate frequency signal should be set within the first Nyquist sampling interval of the DAC.

[0063] c) For telemetry and control (TT&C) received signals, since there is usually a certain frequency gap between the TT&C transceiver frequency bands to ensure transmission and reception isolation, the TT&C receiving link adopts a high-frequency, mid-frequency, single-down-conversion design. The TT&C received RF signal is then transmitted via a single local oscillator signal. After one down-conversion, an analog high-frequency signal is generated for the telemetry and control receiver, with a center frequency of:

[0064]

[0065] in, The radio frequency point for measurement and control reception; the center frequency of the analog high-frequency signal received by the measurement and control reception is used in the frequency design. It is preferably set within the second or third Nyquist sampling interval of the ADC so that it can be subsequently folded to a predetermined digital intermediate frequency position within the first Nyquist sampling interval by an undersampled ADC.

[0066] d) For the data transmission receiving signal, the same high-frequency down-conversion design is adopted, and the data transmission receiving RF signal is processed by a single local oscillator signal. After one down-conversion, an analog high-frequency signal is generated for data transmission reception, with a center frequency of:

[0067]

[0068] in, The data transmission receiving radio frequency point; during frequency design, the center frequency of the analog high-frequency signal for data transmission reception is used. It is preferably set within the second or third Nyquist sampling interval of the ADC so that it can be subsequently folded to a predetermined digital intermediate frequency position within the first Nyquist sampling interval by an undersampled ADC.

[0069] The single local oscillator frequency synthesizer outputs the single local oscillator signal to the receiving high-frequency down-conversion unit and the transmitting up-conversion unit respectively through the power divider, as the common local oscillator signal for receiving the first down-conversion and transmitting the first up-conversion.

[0070] Through the above design, the single local oscillator frequency synthesizer only needs to output one local oscillator signal to simultaneously meet the frequency conversion requirements of measurement and control reception, data transmission reception, measurement and control transmission, and data transmission. Compared with the traditional scheme of configuring multiple local oscillator sources and multi-level frequency conversion links, this embodiment, through the internal frequency landing point planning of a single local oscillator frequency, reduces the number of frequency sources, simplifies the RF link, and reduces the size and power consumption of the equipment. At the same time, it enables the measurement and control and data transmission reception signals to form high-frequency signals suitable for undersampling ADC processing, and enables the measurement and control and data transmission RF transmission signals to share the same transmission channel to complete RF output.

[0071] 3) Uplink signal reception and demodulation

[0072] After receiving the uplink signal from the external antennas pointing to the sky and to the ground, the radio frequency module performs combining, filtering, low-noise amplification, and high-frequency downconversion on the uplink signal. The downconverted high-frequency signal is then output to the signal processing module. The signal processing module performs undersampling ADC and baseband digital signal processing on the high-frequency signal. After processing, the uplink remote control data is extracted and output to other functional units of the spacecraft to execute relevant remote control commands or data transmission processing tasks.

[0073] a) To reduce the design difficulty of the image rejection filter in the receiving circuit and reduce the design complexity of the primary downconversion unit circuit of the receiving high-frequency circuit, the primary downconversion unit of the receiving high-frequency circuit uses a mixer to mix with the local oscillator signal output in 2) to complete the downconversion.

[0074] To balance single-LO frequency reuse and miniaturized receiver link design, the high-frequency down-conversion unit does not down-convert the received signal to zero or low IF, but instead down-converts it to a high-frequency narrowband signal. The center frequency of this high-frequency narrowband signal is located within the second or third Nyquist sampling interval of the ADC. After high-frequency bandpass filtering, gain adjustment, and ADC driving, the high-frequency narrowband signal is output to the ADC unit.

[0075] b) The ADC unit receives the high-frequency signal after one down-conversion and performs analog-to-digital conversion through an undersampled ADC. The undersampled ADC does not directly sample any high-frequency signal, but rather plans the folding frequency of the high-frequency signal after undersampling under the constraints of the center frequency of the received high-frequency signal, the ADC sampling rate, the bandwidth of the received signal, and the folding order.

[0076] Specifically, let the center frequency of the intermediate frequency signal after one down-conversion be... The received signal bandwidth is ADC sampling rate The frequency band of the high-frequency signal is then... The high-frequency signal is preferably located within the second or third Nyquist sampling interval of the ADC. After undersampling by the ADC, the high-frequency signal is folded to the digital intermediate frequency position within the first Nyquist sampling interval as follows:

[0077]

[0078] in, A positive integer, representing the higher-order Nyquist interval index, so that... The signal falls within the first Nyquist sampling interval of the analog-to-digital converter. To ensure that the signal spectrum does not experience in-band aliasing after undersampling, the position of the folded digital intermediate frequency satisfies:

[0079]

[0080]

[0081] Thus, the high-frequency narrowband signal of the measurement and control or data transmission after one down-conversion is completely folded to the predetermined digital intermediate frequency position within the first Nyquist sampling interval after undersampling by the ADC, without in-band aliasing.

[0082] The single local oscillator frequency synthesizer and the ADC sampling clock use the same reference clock source, which improves the stability between the local oscillator frequency and the sampling clock, reduces the frequency deviation and phase drift of the digital intermediate frequency signal after undersampling, and improves the accuracy and reliability of subsequent FPGA digital processing.

[0083] c) The FPGA processing unit performs digital baseband processing on the digital intermediate frequency signal output by the ADC, supporting the reception of data transmission signals at various data rates, including BPSK, direct sequence spread spectrum, and hybrid spread spectrum systems, as well as MPSK systems. Through integrated acquisition, tracking, demodulation, deframering, and decoding of measurement and control and data transmission signals, it obtains uplink measurement and control and data transmission information, such as... Figure 4 As shown.

[0084] 4) Downlink signal transmission

[0085] The radio frequency module adopts an integrated design. The measurement and control and data transmission modes share the same set of transmit primary upconversion unit, filter, power amplifier and isolator. The FPGA processing unit encodes and frames the downlink measurement and control and data transmission information according to the current working mode. Then, it performs pre-compensation and pre-processing on the differences in transmission frequency between different modes, spurious signals between measurement and control and data transmission frequency bands, and differences in power amplifier nonlinear distortion between different frequency ranges through modulation, variable digital filtering and differentiated digital predistortion.

[0086] a) The measurement and control (M&C) and data transmission signals use the same transmit-on-conversion unit and share a mixer for upconversion. However, the M&C and data transmission signals have different frequencies, and directly upconverting the zero-IF baseband signal cannot convert it to different specified frequencies in one step. Therefore, the FPGA processing unit performs digital frequency conversion in the baseband using I-Q quadrature modulation to generate the intermediate frequency signal specified in 2), pre-compensating for the difference between the M&C and data transmission frequencies. Specifically, the M&C signal generates a positive frequency intermediate frequency component through forward complex rotation, while the data transmission signal generates a negative frequency low-IF component through reverse complex rotation. The M&C and data transmission complex baseband signals after encoding, framing, modulation, and shaping filtering are respectively represented as:

[0087]

[0088]

[0089] in, and These are the in-phase components of the measurement and control signal and the data transmission signal, respectively. and These are the orthogonal components of the measurement and control signal and the data transmission signal, respectively. The imaginary unit; It is a discrete-time sample sequence.

[0090] When the terminal is operating in telemetry and control transmission mode, set At this point, the FPGA processing unit performs a positive complex rotation on the measurement and control complex baseband signal to generate a positive frequency intermediate frequency component:

[0091] ;

[0092] in This indicates the digital baseband signal for measurement and control. It represents the base of the natural logarithm, used to construct complex exponential functions; It is a digital constant; For measuring and controlling digital intermediate frequency; The output indicates that by multiplying the baseband signal by a positive rotation factor, the entire spectrum is shifted in the positive frequency direction in the digital domain. The distance.

[0093] When the terminal is operating in data transmission mode, set At this point, the FPGA processing unit performs a reverse complex rotation on the data transmission baseband signal to generate a negative frequency low-intermediate frequency component:

[0094] ;

[0095] in Indicates the digital baseband signal transmitted via data transmission; For digital intermediate frequency transmission; The output indicates that by multiplying the baseband signal by the inverse rotation factor, the entire spectrum is shifted in the negative frequency direction in the digital domain. The distance is used to pre-compensate for frequency differences in the baseband transmit hard link.

[0096] The generated low-frequency signal is mixed with the local oscillator signal output in 2) once to obtain the target radio frequency transmission signal, thus enabling the measurement and control and data transmission modes to be compatible in the same set of upconversion hardware, avoiding the use of multi-level independent upconversion links.

[0097] b) The RF transmission channel uses the same filter for both the measurement and control (TM) and data transmission signals. The passband of this filter covers the transmission frequency range of both the TM and data transmission signals. Because there is a frequency gap between the TM and data transmission signals, the shared RF filter cannot effectively suppress the unwanted spectral components located between the TM and data transmission frequency bands within their passbands. Therefore, the fine spectral shaping is moved forward to the baseband side.

[0098] Specifically, different filter coefficients are configured for the modulated measurement and control and data transmission signals in different modes to perform variable digital filtering, thereby achieving I / Q imbalance correction, image and spurious suppression, and removing unwanted spectral components between the frequencies of the data transmission and measurement and control signals. The filter coefficients for different operating modes are determined based on the modulation method, symbol rate, target occupied bandwidth, DAC sampling rate, transmit frequency, passband ripple, stopband attenuation, transition bandwidth, spectral template, and image suppression index of the corresponding signal.

[0099] The FPGA processing unit contains preset coefficient tables for finite impulse response filters for both measurement and control signals and data transmission signals. The filter coefficients corresponding to the various operating modes are expressed as follows: ,in, Indicates either the measurement and control mode or the data transmission mode. The filter order is indicated by the parameter. The filter coefficients can be designed offline using the window function method, equiripple method, or least squares method, and the image suppression, spurious suppression, and I / Q amplitude-phase imbalance correction effects are calibrated and corrected based on the overall system test results. Since the operating frequency, signal bandwidth, sampling rate, and spectral template differ for different spacecraft missions, the filter coefficients are not limited to fixed values, but are determined jointly by the above design constraints and calibration results.

[0100] Furthermore, by sharing the same filter in the RF transmission channel, spurious signals and leakage outside the frequency band of data transmission and measurement and control signals can be suppressed, avoiding the need to configure multiple independent RF filters, thereby reducing the hardware complexity of the transmission RF channel.

[0101] c) Measurement and control signals and data transmission signals have different requirements for power amplifiers, and they correspond to different transmission frequency points. When they share the same power amplifier, they need to be treated differently.

[0102] It should be clarified that this embodiment uses a shared broadband power amplifier with a working bandwidth covering both the measurement and control transmitter and the data transmission transmitter in actual working conditions, instead of configuring separate power amplifiers for measurement and control and data transmission. Since the measurement and control signals and data transmission signals have different requirements for the power amplifier's operating state, this embodiment uses a pre-distortion coefficient for differentiated configuration. In measurement and control mode, the power amplifier operates in a higher linearity region; in data transmission mode, the power amplifier operates in a higher efficiency region, thus balancing the quality of measurement and control signals and the energy utilization rate of data transmission under the condition of sharing a power amplifier.

[0103] Different transmission frequency points are generated by the front-end FPGA baseband digital frequency conversion and the primary up-conversion unit. The power amplifier itself does not generate frequency points, but only amplifies the signal that has been converted to the target radio frequency point.

[0104] The different operating frequencies are implemented by the FPGA processing unit generating the corresponding low-intermediate frequency signal according to the current operating mode. After being output by the DAC, the signal is mixed with the single local oscillator signal by the primary up-conversion unit to obtain the target radio frequency transmission signal for measurement and control or data transmission. Then, the target radio frequency signal enters the common power amplifier for amplification.

[0105] Measurement and control signals require the power amplifier to operate in the high linearity region to ensure signal quality; data transmission signals, on the other hand, require the power amplifier to operate in the high efficiency region to improve energy utilization. To address the different requirements of the same power amplifier for measurement and control signals and data transmission signals, as well as the varying nonlinear distortion across different frequency ranges, the FPGA processing unit configures differentiated digital predistortion strategies for both signals. For narrow-bandwidth measurement and control signals, a basis function combination adapted to their nonlinear characteristics and a digital predistortion model with low memory depth are used; for wider-bandwidth data transmission signals, a digital predistortion model with richer basis functions and higher memory depth is used to compensate for the differentiated nonlinear distortion of the power amplifier in different modes, ensuring the transmission quality of measurement and control signals and data transmission signals under shared power amplifier conditions. Specifically, the digital predistortion model adopts a memory polynomial model or a generalized memory polynomial model. For input complex baseband signals... Digital predistortion output Represented as:

[0106]

[0107] in, It is a nonlinear order. For memory depth indexing, For predistortion coefficients, This indicates that the input signal was delayed in the past. The signal value of each sample point. This is a higher-order power operation for the modulus.

[0108] The basis function combination includes linear basis functions, higher-order amplitude correlation basis functions, and memory basis functions. For measurement and control signals with narrow bandwidth, a lower-order digital predistortion model with a smaller memory depth is used, and its basis function combination includes... , , And a small number of delayed memory items .in, A smaller memory depth, such as 1 or 2, can be used to compensate for the static nonlinearity and weak memory effect of the measurement and control signal.

[0109] For data transmission signals with wide bandwidth and high data rates, a digital predistortion model with a higher nonlinear order and a larger memory depth is adopted. The memory depth corresponding to the data transmission signal can be 3 or 5, or other positive integers determined based on the bandwidth, sampling rate, and power amplifier memory effect test results of the data transmission signal, in order to compensate for the dynamic nonlinear distortion, frequency-related distortion, and out-of-band spectral regeneration caused by the data transmission signal under broadband transmission conditions.

[0110] The predistortion coefficients can be obtained through ground testing and calibration or on-orbit calibration. The complex baseband signal at the power amplifier input and the equivalent complex baseband signal at the output obtained via a feedback receiving link are collected, and time alignment, amplitude normalization, and phase correction are performed on both. Subsequently, the predistortion coefficients for different operating modes, different transmission frequency points, and different output power levels are obtained using the least squares method, indirect learning structure, or lookup table correction method, and these predistortion coefficients are written into the coefficient table of the FPGA. During actual operation, the terminal calls the corresponding digital predistortion model and coefficients according to the current measurement and control or data transmission mode, transmission frequency point, and power level.

[0111] Example 2

[0112] This embodiment proposes an exemplary implementation method based on Embodiment 1. To facilitate the explanation of the planning relationship between the single local oscillator frequency, the low intermediate frequency of transmission, the high intermediate frequency of reception, and the undersampling folding frequency in this invention, the following exemplary engineering frequency points are given.

[0113] It should be noted that the frequency points described below are only used to illustrate the frequency planning method of the present invention, and do not correspond to any specific satellite model, specific mission or actual on-orbit satellite-to-ground link frequency points, nor do they constitute a limitation on the scope of protection of the present invention.

[0114] Let the measurement and control transmission frequency, data transmission frequency, measurement and control reception frequency, and data transmission reception frequency be respectively: , , , Single local oscillator frequency = .

[0115] At this time, the single local oscillator frequency Located at the data transmission radio frequency point With measurement and control transmission frequency point The frequencies are between, but not at, the strict center frequency of, the control and measurement transmitter frequency and the data transmission transmitter frequency. Specifically, the center frequencies of the control and measurement transmitter frequency and the data transmission transmitter frequency are:

[0116]

[0117] The single local oscillator frequency is 2400MHz. Therefore, the single local oscillator frequency... Deviating from the strict center frequency position of the measurement and control radio frequency point and the data transmission radio frequency point can reduce the risk of the measurement and control radio frequency transmission signal and the data transmission radio frequency transmission signal forming symmetrical mirror components.

[0118] For the measurement and control radio frequency transmission signal, its low-intermediate frequency is:

[0119]

[0120] The telemetry and control system transmits a simulated low-intermediate frequency signal, which is then converted to a single local oscillator signal via a primary up-conversion unit. After one up-conversion, the measurement and control transmission radio frequency signal is obtained:

[0121]

[0122] For data transmission radio frequency transmission signals, the low-intermediate frequency is:

[0123]

[0124] The low-intermediate frequency component corresponding to the data transmission radio frequency signal is a negative frequency component, and its amplitude is:

[0125]

[0126] The data transmission transmits an analog low-intermediate frequency signal, which is then converted to a single local oscillator signal via a single up-conversion unit. After one up-conversion, the data transmission radio frequency signal is obtained:

[0127]

[0128] If the DAC sampling rate If set to 100MHz, the first Nyquist sampling range of the DAC is 0~50MHz.

[0129] The aforementioned 15MHz analog low-IF signal for telemetry and control transmission and 10MHz analog low-IF signal for data transmission are both located within the first Nyquist sampling interval of the DAC, which can meet the DAC output requirements.

[0130] For the measurement and control received signal, it is transmitted via a single local oscillator signal. The intermediate frequency center frequency after one down-conversion is:

[0131]

[0132] For data transmission received signals, it is transmitted via a single local oscillator signal. The intermediate frequency center frequency after one down-conversion is:

[0133]

[0134] If ADC sampling rate If set to 100MHz, the first Nyquist sampling range of the analog-to-digital converter is 0~50MHz, the second Nyquist sampling range of the ADC is 50~100MHz, and the third Nyquist sampling range of the ADC is 100~150MHz.

[0135] Therefore, the 70MHz high-frequency analog signal received by the data transmission is located in the second Nyquist sampling interval of the ADC, and the 112MHz high-frequency analog signal received by the telemetry and control is located in the third Nyquist sampling interval of the ADC.

[0136] The digital intermediate frequency (IF) position of the received analog high-frequency signal, after undersampling by the ADC and folded to the first Nyquist sampling interval, is:

[0137]

[0138] The digital intermediate frequency (IF) position of the analog high-frequency signal received by the telemetry and control system, after undersampling by the ADC and folded to the first Nyquist sampling interval, is as follows:

[0139]

[0140] in, This indicates the digital intermediate frequency (IF) of the received analog high-frequency signal after undersampling by the ADC and folded to the first Nyquist sampling interval. This indicates that the analog intermediate frequency signal received by the telemetry and control system is folded to the digital intermediate frequency within the first Nyquist sampling interval after undersampling by the ADC; thus, the analog intermediate frequency signal received by the data transmission system and the analog intermediate frequency signal received by the telemetry and control system are folded to 30MHz and 12MHz respectively after undersampling, both of which are located within the first Nyquist sampling interval of the analog-to-digital converter.

[0141] Furthermore, if the bandwidth of the measurement and control received signal... If the frequency is 2MHz, then the bandwidth of the measurement and control receiving signal after undersampling and folding is 12±1MHz, that is, 11~13MHz.

[0142] If the data transmission receiving signal bandwidth If the frequency is 20MHz, then the bandwidth of the undersampled and folded data transmission received signal is 30±10 MHz, that is, 20~40MHz.

[0143] The frequency bands of the above-mentioned measurement and control received signal after folding and the frequency bands of the data transmission received signal after folding are both completely located within the first Nyquist sampling range of the analog-to-digital converter (0~50MHz), and there is no intra-band overlap between the two. Therefore, intra-band aliasing after undersampling can be avoided.

[0144] As can be seen from the above example, by selecting the single local oscillator frequency and ADC sampling rate This allows the telemetry and control transmitting side and the data transmission transmitting side to generate low-IF signals of 15MHz and 10MHz respectively, meeting the output requirements within the first Nyquist sampling interval of the DAC; simultaneously, it allows the telemetry and control receiving side and the data transmission receiving side to generate high-IF signals of 112MHz and 70MHz respectively, falling into the third and second Nyquist sampling intervals of the ADC, and folding them to 12MHz and 30MHz digital intermediate frequency positions after undersampling. Thus, under single local oscillator conditions, both the low-IF transmission planning and the high-IF reception undersampling planning requirements are simultaneously met.

[0145] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A miniaturized integrated measurement, control, and data transmission terminal, characterized in that, include: The baseband processing unit is used to generate a transmit digital low-IF signal of the corresponding frequency according to the current operating mode, and to analyze the receive digital intermediate frequency signal. A single local oscillator (LOO) generation unit, connected to the baseband processing unit, is used to provide a unique and constant frequency LOO signal; wherein the frequency of the LOO signal deviates from the preset center frequency positions of the measurement and control transmission radio frequency point and the data transmission radio frequency point. The transmission link includes a digital-to-analog converter, a primary upconverter, and a shared broadband power amplifier cascaded together. The digital-to-analog converter converts the transmitted digital low-IF signal into a transmitted analog low-IF signal. The primary upconverter performs a primary upconversion between the transmitted analog low-IF signal and the single local oscillator signal. The shared broadband power amplifier has a working bandwidth covering the measurement and control transmission radio frequency point and the data transmission radio frequency point, and amplifies the signal after the primary upconversion to obtain the target radio frequency transmission signal. The receiving link includes a receiver downconverter and an analog-to-digital converter cascaded in sequence; The receiving downconverter is used to perform a downconversion on the input radio frequency received signal and the same single local oscillator signal to obtain a received analog high frequency signal. The terminal does not contain secondary or higher analog frequency conversion links, and the frequency of the single local oscillator signal satisfies a unified sampling constraint relationship with the frequency of the transmitted analog low-IF signal and the frequency of the received analog high-IF signal. The frequency of the transmitted analog low-IF signal is entirely within the first Nyquist sampling interval of the digital-to-analog converter; The frequency of the received analog intermediate frequency signal is located within the second or third Nyquist sampling interval of the analog-to-digital converter. After being undersampled by the analog-to-digital converter, it is folded into the first Nyquist sampling interval without in-band aliasing, thus forming the received digital intermediate frequency signal.

2. The miniaturized integrated measurement, control, and data transmission terminal according to claim 1, characterized in that, The frequency of the single local oscillator signal The following asymmetric constraints must be satisfied: ； in, For measurement and control transmission radio frequency points, Number of transmission radio frequency points; By making the frequency of the single local oscillator signal deviate from the center frequency position of the measurement and control radio frequency point and the data transmission radio frequency point, the image frequency corresponding to the measurement and control radio frequency transmission signal and the image frequency corresponding to the data transmission radio frequency transmission signal do not coincide symmetrically.

3. The miniaturized integrated measurement, control, and data transmission terminal according to claim 1, characterized in that, The baseband processing unit is equipped with a digital predistortion module, which is used to perform predistortion processing on the transmitted digital low-IF signal before it is input to the shared broadband power amplifier according to the current working mode. When the current working mode is the measurement and control transmission mode, the digital predistortion module calls the first predistortion coefficient to compensate for the amplitude and phase of the measurement and control radio frequency transmission signal, so that the measurement and control radio frequency transmission signal output by the shared broadband power amplifier meets the preset linearity requirements. When the current working mode is data transmission mode, the digital predistortion module calls the second predistortion coefficient to compensate for the amplitude and phase of the data transmission radio frequency transmission signal, so that the data transmission radio frequency transmission signal output by the shared broadband power amplifier meets the preset efficiency and spectrum index requirements.

4. The miniaturized integrated measurement, control, and data transmission terminal according to claim 1, characterized in that, The radio frequency received signal includes measurement and control radio frequency received signal and data transmission radio frequency received signal; The measurement and control radio frequency received signal is down-converted by the receiving downconverter to generate a measurement and control received analog high-frequency signal. The measurement and control received analog high-frequency signal is completely located within the third Nyquist sampling interval of the analog-to-digital converter. The data transmission radio frequency received signal is down-converted by the receiving downconverter to generate a data transmission received analog high frequency signal. The data transmission received analog high frequency signal is completely located within the second Nyquist sampling interval of the analog-to-digital converter.

5. A miniaturized integrated measurement, control, and data transmission terminal according to claim 4, characterized in that, The measurement and control receiving analog high-frequency signal, after being undersampled and folded to form the measurement and control receiving digital intermediate frequency signal, and the data transmission receiving analog high-frequency signal, after being undersampled and folded to form the data transmission receiving digital intermediate frequency signal, both have frequency bands within the first Nyquist sampling interval and do not have any spectral overlap.

6. A miniaturized integrated measurement, control, and data transmission terminal according to claim 1, characterized in that, The baseband processing unit generates a transmit digital low-IF signal corresponding to the current operating mode in the digital domain, and switches between the measurement and control transmission radio frequency point and the data transmission radio frequency point at the radio frequency terminal while keeping the frequency of the single local oscillator signal constant.

7. A miniaturized integrated measurement, control, and data transmission terminal according to claim 1, characterized in that, The operating bandwidth of the shared broadband power amplifier simultaneously covers both the measurement and control radio frequency point and the data transmission radio frequency point. The terminal's transmission link amplifies the power of the measurement and control radio frequency transmission signal and the data transmission radio frequency transmission signal in a time-division manner through the shared broadband power amplifier.

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