A novel multiplexing data transmission architecture: multiplexing modulator (MM) for twin remote sensing satellites

This paper proposes a novel standalone engineering model for space data transmission - the Multiplexing Modulator (MM). In previous space missions, multiplexers and modulators operated as separate standalone units: multiplexers aggregated multiple low-rate signals into single high-rate streams to enhance channel efficiency, while modulators converted baseband signals into high-frequency carrier waves suitable for channel transmission. This paper integrates both functionalities into a unified Multiplexing Modulator (MM), achieving substantial spacecraft electronics consolidation. The integration reduces weight by over 40%, decreases volume by 35% compared to discrete units, and power consumption by over 25%. All while maintaining space-grade reliability. The newly designed MM performs integrated processing of payload and telemetry data through multiplexing, storage, encryption, and X-band modulation before transmitting processed signals to ground stations via phased array antenna. Key innovations include 12Tbit massive storage capacity, multi-mode downlink capabilities, exceptional stability, high radiation tolerance, and ultra-low power consumption.

1 Introduction

This paper proposes a novel standalone engineering model for space data transmission - the Multiplexing Modulator (MM). In previous space missions, multiplexers and modulators operated as separate standalone units: multiplexers (Kuno et al., 2022; Marom et al., 2022; Munakata et al., 2022) aggregated multiple low-rate signals into single high-rate streams to enhance channel efficiency, while modulators (Baghdasaryan, 2023; Jacob and Baiju, 2015) converted baseband signals into high-frequency carrier waves suitable for channel transmission (Kuno et al., 2022; Marom et al., 2022; Munakata et al., 2022). This paper integrates both functionalities into a unified Multiplexing Modulator (MM), achieving substantial spacecraft electronics consolidation. The Multiplexing Modular (MM) design is a spatial data transmission device based on frequency division multiplexing, with a data transmission rate of 900 Mbps and 400 Mbps switchable. The multiplexing modulator for these satellites primarily functions to:

1. Receive payload and telemetry data;

2. Perform data multiplexing, storage and encryption;

3. Modulate processed data into X-band signals;

4. Transmit signals to ground stations via phased array antenna.

The multiplexer modulator used in the aerospace field is a key component for achieving efficient data transmission. The European Space Agency (ESA), the National Aeronautics and Space Administration (NASA) of the United States, and other countries have conducted in-depth research and product development in this field (Dai et al., 2024; Singh and Ahrens, 2023).

The core function of a multiplexing modulator is to combine multiple data streams into a single signal for transmission, and demultiplexing it at the receiving end, thereby effectively utilizing communication bandwidth, reducing system complexity and power consumption. In aerospace applications, this equipment must meet strict requirements such as high reliability, low power consumption, radiation resistance, and extreme temperature resistance (Daras et al., 2023; Edwards et al., 2010).

ESA and NASA have long been major driving forces in aerospace technology, including communication systems and multiplexing modulators. The two institutions have collaborated on many space missions, such as the Laser Interferometer Space Antenna (LISA) mission (Daras et al., 2023) and the Mass Variation and Earth Science International Constellation (MAGIC) mission, aimed at extending the time series of gravity fields and improving accuracy and spatiotemporal resolution (Edwards et al., 2010).

Although the specific performance parameters of the multiplexing modulator product are not directly detailed in the provided literature, its requirements and technical characteristics in the aerospace field can be analyzed from the following aspects (Ruan et al., 2022):

Communication protocols and data transmission: Aerospace vehicles typically require the transmission of large amounts of telemetry data, scientific payload data, and command data. Multiplexing modulators play a crucial role in these systems, ensuring that data is transmitted with high efficiency and reliability. For example, the Deep Space Network is an important application of NASA in this area.

Radiation resistance: High energy particle radiation in the space environment can cause damage to electronic components. Therefore, aerospace grade multiplex modulators must adopt radiation resistant design and materials to ensure long-term reliable operation. ESA and NASA have conducted extensive research in material flight experiments to understand the synergistic effects of high-energy radiation particles, atomic oxygen, micrometeoroids, orbital debris, and ultraviolet radiation on materials.

Power consumption and weight: In space missions, the power consumption and weight of spacecraft are strictly limited. The multiplexing modulator needs to adopt a low-power design and be as small and lightweight as possible to minimize the impact on the overall design of the spacecraft.

The product performance of aerospace multiplex modulators is mainly reflected in high reliability, low power consumption, radiation resistance, and support for new high-speed and high-capacity communication technologies. ESA and NASA have made significant progress in these areas through internal research and international cooperation. Although the provided information does not directly list detailed product models and specific performance indicators, through analysis of the technical requirements in the aerospace field, it can be inferred that its multiplexing modulator technology will inevitably develop towards extreme environments, high integration, and high data throughput (Daras et al., 2023; Kubanek et al., 2021).

Figure 1 illustrates a traditional space data transmission architecture. In this configuration, payload-derived low-rate data streams are aggregated by a multiplexer into a consolidated high-rate signal, which is subsequently converted to an intermediate frequency (IF) signal via a high-speed Digital-to-Analog Converter (DAC).

Figure 1

Figure 1. Traditional space data transmission architecture.

This IF signal traverses RF cabling to reach the modulator, where it is upconverted to application-specific RF carriers. Based on distinct power requirements, the modulated signals are routed to corresponding phased array antennas for downlink transmission to ground stations. Critically, both the multiplexer and modulator require dedicated Power Conditioning Units (PCUs) and High-Reliability Computing modules (HRCs). The PCUs convert primary power bus voltages (e.g., 28 V/100 V) into secondary digital and analog regulated buses (±5 V, ±15 V), while the HRCs interface with the satellite data platform via CAN bus to execute command forwarding and perform autonomous health monitoring. (Matsumura et al., 2016; Xu et al., 2018; Liu et al., 2019).

The space data transmission architecture of the novel Multiplexing Modulator (MM) is illustrated in Figure 2. By integrating multiplexers and modulators into a single standalone unit, this design significantly reduces equipment weight by 40%, volume by 35%, and power consumption by over 25%. The comparison of weight, volume, and power consumption between MM and the multiplexer and modulator previously designed by our team is shown in Table 1. The proposed MM comprises six core modules: Power Conditioning Unit (PCU), High-Reliability Computing Unit (HRCU), Data Processing Unit (DPU), Encoding and Modulation Unit (EMU), Radio Frequency Unit (RFU), Multiplexed Combiner/Power Distribution Unit (MCPDU).

Figure 2

Figure 2. Multiplexing modulator (MM) data transmission architecture.

Table 1

Table 1. The comparison of weight, volume, and power consumption between MM and the multiplexer and modulator previously designed.

In this system, a De-multiplier (DEMUX) is a digital circuit device whose core working principle is to allocate a single input signal to one of multiple output channels based on the instructions of the selection signal. Simply put, it performs the inverse operation of a multiplexer (MUX). The multiplexer combines independent signals from multiple sources into a single transmission channel, while the demultiplexer separates this combined signal back into the original independent signal.

The basic structure and working principle of a demultiplexer can be summarized as follows:

The demultiplexer only has one data input line, carrying the signals that need to be allocated. This signal can be a combined signal output from a multiplexer, or any data stream that needs to be routed to a specific output.

The demultiplexer has a set of selected input lines, whose binary values determine which output channel the input signal will be routed to. For example, a 1–4 demultiplexer (1 × 4 DEMUX) typically has 2 selection input lines (S0 and S1) because 2 binary bits can generate 4 different combinations (00, 01, 10, 11), each corresponding to a specific output channel.

The demultiplexer has multiple output channels, and the input signal will ultimately be directed to one of them. At a given point in time, only one output channel is active, carrying the input signal, while the other output channels are in an inactive state.

The internal logic circuit of the demultiplexer controls the connection of input signals to specific output channels based on the state of the selected input line. This is usually achieved through the combination of logic gates such as AND gates and NOT gates.

2 System design of MM

2.1 Overall hardware design

As explicitly stated in Chapter 1, the proposed MM comprises six core modules: Power Conditioning Unit (PCU), High-Reliability Computing Unit (HRCU), Data Processing Unit (DPU), Encoding and Modulation Unit (EMU), Radio Frequency Unit (RFU), Multiplexed Combiner/Power Distribution Unit (MCPDU).

The satellite platform’s primary power bus (28 V/100 V nominal) interfaces with the Multiplexing Modulator’s Power Conditioning Unit (PCU). Within the PCU, DC/DC converters transform this primary input into regulated secondary power rails, distributing +5VDC to all internal circuit boards. Electromechanical relays—actuated by telecommand (TC) signals—enable switching between primary and redundant power chains, as well as full system de-energization. Crucially, both primary and backup power circuits are co-located on a single multilayer PCB. The secondary power system implements dual-redundant cold backup architecture, where failover switching to the standby power chain is executed via TC commands upon detection of critical faults (e.g., overcurrent >150% or undervoltage <18 V).

The HRCU primarily provides the multiplexing modulator with dual-redundant CAN bus interfaces for communication with the satellite management system, supplies internal communication interfaces for other functional units within the multiplexing modulator and controls their operation, offers interfaces for program loading/refresh control, and provides hardware for the operating system and application software. The high-reliability computing unit mainly consists of a CPU, SDRAM, NOR FLASH, crystal oscillator, watchdog timer, CAN controller, and transceiver. To prevent program runaway caused by single-event upsets, the CPU performs ECC error correction coding on SDRAM; for both power-on reset and watchdog-triggered reset scenarios, the CPU can boot from different program storage areas, thereby avoiding system startup failure due to anomalies in a single program zone and enhancing system reliability.

The DPU primarily performs functions including payload data reception, processing, storage, and multiplexed playback, while incorporating a 12Tbit high-capacity storage system. The unit employs board-level backup design where two independent modules operate in parallel. Each module mainly consists of an FPGA, DDR2 SDRAM, NAND FLASH storage arrays, high-speed serial transceivers, RS422 receiver ICs, point-of-load (POL) converters, crystal oscillators, and related components.

The EMU primarily consists of an encoding/modulation FPGA, high-speed DAC, high-speed serial bus interface, and power modules. Its core functionalities include:

1. Receiving X-band transmission data from the data processing unit via TLK2711 interfaces (Zhao, 2022);

2. Encrypting incoming data in the FPGA, applying LDPC encoding, performing 8PSK constellation mapping and pulse shaping, then outputting processed signals to the RF unit through external SMA connectors for quadrature modulation;

3. Accepting power-on configuration and firmware refresh commands for the FPGA from the CPU;

4. Implementing data transmission joint modulation functionality using cryptographic keys distributed by the CPU;

5. Automatically powering on during orbital passes over ground stations and powering down when exiting coverage areas.

The RFU primarily consists of circuits such as an X-band modulator, carrier frequency source, and amplifiers.

The MCPDU establishes the RF channel between the RF unit and the phased array antenna; as a passive RF component, it offers high reliability.

2.2 CAN bus design

The MM employs a configurable bus architecture integrating CAN bus standards as its critical communication backbone (Figure 3), with meticulous design considerations paramount due to their fundamental role in mediating payload status monitoring and spacecraft command execution; specifically, this architecture implements cold redundancy with duplicated A/B channels for both bus types, significantly enhancing system fault tolerance through hardware-based redundancy while strictly adhering to spacecraft bus design specifications, thereby ensuring robust signal integrity through controlled impedance routing, electromagnetic interference (EMI) shielding, and validated signal termination protocols across all mission operating conditions.

Figure 3

Figure 3. The complex CAN Bus construction standards.

As to CAN bus as an example, the explicit level requirement is (Equation 1):

$V_{diff\_dom}=V_{CAN\_H}-V_{CA{N}_L}\ge 1.5V(1)$

Implicit level requirement (Equation 2):

$V_{diff\_dom}=V_{CAN\_H}-V_{CA{N}_L}\ge 0.5V(2)$

Common mode voltage tolerance (Equation 3):

$-2V\le V_{CM}\le 7V(3)$

Terminal resistors need to be deployed at both ends of the bus to suppress signal reflection (Equation 4):

$R_{term}=\frac{Z_0}{2}=120\mathrm{\Omega }\pm 5\%(4)$

The formula for signal quality assessment is (Equation 5):

$S_{total}=\frac{W_{edge}\times S_{edge}+W_{amp}\times S_{amp}+W_{ref}\times S_{ref}}{W_{total}}(5)$

Typical settings (W_edge, W_amp, W_ref) =(50%, 25%, 25%)

S_edge scores the edge rate (0%∼100%), and scores 100% when the edge time t_edge is less than 10% and the bit time is less than 10%

S_amp is a stable amplitude rating.

S_amp = 100%. When U_distortion = V_{diff_dom} ≥ 2.2 V, U_disturb is the minimum difference between explicit/implicit levels.

S_ref: Reflection Distortion Score. S_ref = 100% when U_pp = U_disturb (no overshoot/undershoot).

The transmission speed of CAN bus is relatively high, so twisted pair cables are used in PCB design, with a line length matching error of ≤ 5mil to avoid branching (stub length<3 cm).

2.3 DPU hardware design

The DPU primarily performs functions including payload data reception, processing, storage, and multiplexed playback, while incorporating a 12Tbit high-capacity storage system. The unit employs board-level backup design where two independent modules operate in parallel. Each module mainly consists of an FPGA, DDR2 SDRAM, NAND FLASH storage arrays, high-speed serial transceivers, RS422 receiver ICs, point-of-load (POL) converters, crystal oscillators, and related components.

The DPU not only implements fundamental interface data transmission functions such as TLK2711 high-speed signal communication with payloads and RS422 communication, but also incorporates a 12Tbit high-capacity storage system for retaining valid scientific payload data. To achieve this storage capacity, we selected 512 Gbit NAND FLASH memory chips. By connecting 24 chips in parallel, this design constructs a storage array with 128-bit data width and total capacity of 12Tbit.

2.4 EMU hardware design

The EMU primarily consists of an encoding/modulation FPGA, high-speed DAC, high-speed serial bus interface, and power modules. Its core functionalities include:

1. Receiving X-band transmission data from the data processing unit via TLK2711 interfaces;

2. Encrypting incoming data in the FPGA, applying LDPC encoding, performing 8PSK constellation mapping and pulse shaping, then outputting processed signals to the RF unit through external SMA connectors for quadrature modulation;

3. Accepting power-on configuration and firmware refresh commands for the FPGA from the CPU;

4. Implementing data transmission joint modulation functionality using cryptographic keys distributed by the CPU;

5. Automatically powering on during orbital passes over ground stations and powering down when exiting coverage areas.

The EMU supports the SRRC-8PSK modulation scheme, which is configured as follows: channel count: 1; channel coding: LDPC; modulation format: 8PSK; single-channel symbol rate: 900 Mbps; baseband shaping: root-raised-cosine (RRC) shaping filter with roll-off factor 0.15. The constellation diagram is illustrated in Figure 4. Through our optimization, this modulation scheme achieves an Error Vector Magnitude (EVM) of less than 8%.

Figure 4

Figure 4. The constellation diagram of EMU.

2.5 Functional description of MM

The MM actually possesses the following functions:

1. Data transmission AOS frames must conform to CCSDS formats, while modulation and channel coding comply with ECSS-E-50-01C standards;

2. Data exchange with the satellite management computer via CAN bus: transmitting telemetry data reflecting the operational status of the data transmission subsystem, receiving control commands, system time information, etc., and executing subsystem operational mode switching;

3. Receiving raw data output from payloads; receiving platform engineering parameter data from the satellite management computer; performing storage management for the above multi-channel data;

4. Providing solid-state mass storage: all partitions support autonomous erasure and command-based erasure (individual/full partitions); featuring bad block management and error correction capabilities; enabling partition size adjustment;

5. Completing multiplexing of payload data and platform data;

6. Supporting data protection functions;

7. Supporting real-time transmission mode for platform data.

3 Software design of MM

In the previous section, We have proposed a detailed system design for the MM. The multiplexing modulator management software comprises four functional modules: CAN bus communication management, mass storage management, engineering telemetry management, and health management and operational maintenance.

3.1 CAN bus communication management design

The multiplexing modulator exchanges data with the satellite management computer via CAN bus, receiving spacecraft time broadcast data, telemetry request commands, indirect commands, and data injection packets from the satellite management computer, while transmitting engineering telemetry parameters of the multiplexing modulator to the satellite management computer.

During system power-on or reset, the CAN bus is initialized by configuring the CAN bus interface chip SJA1000 according to the communication protocol to enter normal operational mode. The software receives indirect commands from the satellite management computer, parses the received indirect commands, discards erroneous or invalid indirect commands, and executes valid indirect commands correctly.

The software responds to telemetry request commands sent by the satellite management computer by transmitting engineering telemetry parameters of the integrated satellite-ground communicator to the satellite management computer.

3.2 Mass storage management software design

The software implements mass storage management functions including storage initialization, data storage, data playback, and data erase control.

Data storage employs a fixed-partition cyclic storage method: four storage partitions are established, each operating independent cyclic data storage. When any partition becomes full, the oldest data is automatically erased and overwritten with new data.

During software initialization, the FLASH BAT table information is read from the storage control FPGA. Based on this BAT table, storage status details for each partition are acquired to establish foundational storage management.

During data storage, the software locates available storage space and sends storage addresses for each partition to the storage control FPGA.

Data playback supports adjusting playback pointers by address or time within each partition to achieve on-demand playback.

3.3 Health management and operation maintenance software design

The software should possess certain system maintenance and safeguard functions, mainly including: system initialization, time management, EDAC error correction processing, FPGA loading and refresh control, CAN bus communication monitoring, and on-orbit updates.

The management software’s external interfaces primarily include interfaces with the CAN bus, storage control FPGA, encoding and modulation FPGA, refresh chip, and GPIO.

4 Reliability and safety design of MM

4.1 Redundancy design

To meet the system’s high reliability requirements, the multiplexing modulator employs multiple redundancy design methodologies:

4.1.1 Hardware redundancy

Units such as the power unit, computing unit, data storage unit, and encoding/modulation unit adopt redundant structures. When local failures occur, backup units can be activated to ensure normal system operation; all redundancies implement cold backup design.

The CAN bus utilizes an A/B bus design with dual interface chipsets, enabling switchover to the standby bus upon failure of any primary bus.

4.1.2 Software redundancy

The CPU applies ECC error correction to program-storing FLASH and runtime SDRAM, preventing program execution errors caused by single-event upsets (SEUs). For both power-on reset and watchdog-triggered reset scenarios, the CPU boots from distinct addresses, avoiding system failures due to corruption in a single program zone. Software protection techniques minimize software faults.

4.1.3 Information redundancy

CAN bus communications incorporate accumulated checksums beyond valid data in engineering parameters and injected data formats to detect transmission/storage errors. Data stored in NAND FLASH utilizes RS encoding against SEUs.

4.1.4 Static redundancy

FPGA designs implement triple modular redundancy (TMR), isolating/correcting fault effects before they reach module outputs. Critical parameters are triplicated in NOR FLASH; read operations employ two-out-of-three voting to ensure correct operation during failures, enhancing system reliability.

4.2 Electromagnetic compatibility analysis and design

The purpose of electromagnetic compatibility (EMC) design is to ensure normal operation in the intended system electromagnetic environment without performance degradation or malfunction, while simultaneously preventing interference with other instruments. It aims to reduce conducted and radiated interference from equipment on power lines, improve the conducted and radiated susceptibility of all devices, and enhance anti-interference capabilities.

The electromagnetic radiation protection and electromagnetic leakage prevention measures adopted by the multiplexing modulator include:

4.2.1 Shielding design

Power and clock cables undergo shielded twisted-pair treatment to prevent antenna effects from currents.

4.2.2 Grounding design

Primary and secondary grounds are isolated; primary power return lines are isolated from the chassis; primary power buses are isolated from secondary power buses and signal lines. Secondary power ground and signal ground share a single connection point; secondary ground connects to chassis ground.

4.2.3 Filtering design

Power interfaces incorporate RC filter circuits to prevent external electromagnetic pulse interference with the equipment. Filter circuits exist at the entrance of each printed circuit board and unit circuit. DC/DC module power supplies emphasize enhanced input/output filtering by using specialized filter modules to reduce electromagnetic interference effects and external radiation. RF output ports utilize bandpass filters for out-of-band suppression.

4.2.4 Structural design

Equipment chassis is sealed to shield against electromagnetic radiation from the device and external interference. Correct selection of active/passive components, appropriate circuit design, and layered PCB layout techniques are implemented.

4.2.5 Interface design

Power interfaces of the multiplexing modulator configure EMI filters matching the modules at the input end. For open-collector signal interfaces, appropriate input impedance is selected to improve anti-interference capability; digital signal interfaces use input circuits with hysteresis characteristics to reduce glitch sensitivity; analog signal interfaces ensure impedance matching and implement proper grounding.

4.3 Heat design

The multiplexing modulator operates within a temperature range of −10 °C to +45 °C. Components with thermal dissipation exceeding 0.3 W require heat dissipation treatment. The modulator’s chassis undergoes black anodized surface treatment, with heat conduction at mounting interfaces. Radiative heat dissipation capability is ensured by the performance specifications of the black anodized coating on the chassis surface.

Thermal design measures include:

1. For high-power components: DC/DC modules in the power unit (primary heat sources) utilize 2 mm-thick aluminum thermal pads integrally machined with the plate frame, ensuring direct contact between component undersurfaces and pads;

2. For medium-power components (>0.3 W thermal dissipation) such as CPUs, FPGAs, SDRAM, POL converters, and DACs: thermal pads transfer heat to the plate frame, which then radiates heat toward the platform cabin walls. After precise thermal design, the overall temperature simulation of the MM is shown in Figure 5.

Figure 5

Figure 5. The temperature simulation of the MM.

4.4 System integration reliability design

Firstly, due to the system integration of repeaters and modulators in the equipment, there are certain risks in the spatial environment. Due to sufficient electronic reliability verification and standalone system integration function verification on the ground, including various environmental simulation tests, the risks mainly focus on space environment adaptability. Our team conducted Failure Mode Effect Analysis (FMEA) on MM based on the above analysis and implemented corresponding protective measures against space radiation effects.

Failure Mode Effect Analysis (FMEA) is a design analysis method used in the system or equipment design process to analyze various potential failure modes of each component unit of a product and their impact on product functionality. Each potential failure mode is classified according to its severity, and preventive and improvement measures are proposed to improve the reliability of the system or equipment. FMEA is a qualitative reliability analysis method. The FMEA analysis results and fault handling measures are shown in Table 2.

Table 2

Table 2. The FMEA analysis results.

The reliability of the spliced modulator is expected to complete a 5-year assessment life in low orbit, with a reliability of better than 0.985 at the end of the life.

5 Experiment of MM

The multiplexing modulator for the remote sensing twin-satellite system is scheduled for launch later this year. As of the drafting date, the multiplexing modulator has completed all acceptance-level environmental tests and pre-launch system integration tests, including ESS mechanical testing, ESS thermal cycling, EMC testing, mechanical tests (random vibration and sinusoidal vibration), thermal cycling, burn-in testing, thermal vacuum testing, etc. The thermal cycling test standards are shown in Table 3. The multiplexed modulator is shown in Figures 6–8 for the ESS thermal cycle test, thermal cycle test, and EMC test, respectively.

Table 3

Table 3. Conditions of thermal cycling test.

Figure 6

Figure 6. MM in ESS thermal cycling.

Figure 7

Figure 7. MM in thermal cycling test.

Figure 8

Figure 8. MM in EMC test.

The multiplexing modulator demonstrated stable performance throughout the aforementioned tests. Under extreme testing conditions, its RF transmission functions remained fully operational, while Error Vector Magnitude (EVM) and power levels during environmental tests maintained consistent stability, as illustrated in Figure 9.

Figure 9

Figure 9. MM RF performance in environmental Mode test.

The main evaluation indicators for the Multiplexing Modular (MM) are shown in Table 4. During ground testing, our team conducted various experiments carefully to ensure the parameters in Table 4. Therefore, we strongly believe that the Multiplexing Modular (MM) will perform well in space missions.

Table 4

Table 4. Multiplexing modular (MM) main evaluation parameters.

6 Future work and outlook

Micro-Electro-Mechanical Systems (MEMS) technology plays a significant role in improving the radio frequency (RF) performance of multiplexers and moders, providing key hardware optimization solutions for modern RF communication systems through its miniaturization, high accuracy, and low power consumption. These improvements are not only reflected in performance parameters, but also present new possibilities for the overall integration and adaptability of the equipment.

Multiplexers are used in RF communications to transmit multiple frequencies simultaneously, requiring high selectivity, low insertion loss, and good signal isolation. Conventional multiplexer designs often face the problems of large size and high overhead, while the introduction of MEMS technology addresses low insertion loss and high isolation performance. The high isolation and low loss characteristics of MEMS switches are important for RF multiplexers. Research has shown that higher isolation and power consumption as low as microwatt levels can be achieved by optimizing metal film materials and dielectric structures in MEMS multiplexers, resulting in significantly improved transmission efficiency and band selectivity of the multiplexers (Percy et al., 2025; Velagaleti and Nalluri, 2024).

MEMS multiplexers enable dynamic regulation of multi band signals. For example, some studies have proposed that a multiplexer based on a MEMS switch configuration could adjust the impedance network by electrical actuation, thereby dynamically adapting to different operating frequencies and signal characteristics in actual operation (Lanter and Sutinjo, 2025; Lanter and Sutinjo, 2025).

MEMS technology enables the volume of the multiplexer to be significantly reduced. For example, in small multi frequency antenna multiplexer applications, efficient signal processing and multiplexing can be achieved in a very small chip area by optimizing the geometric and electromagnetic properties of the micromachined elements (Velagaleti and Nalluri, 2024; Miao et al., 2025).

MEMS multiplexers are highly adaptable to environmental changes such as fluctuations in temperature or vibration due to their high mechanical stability. Some designs even employ built-in thermoelectric cooling modules to further reduce the effect of operating conditions on signal performance (Zhang and Liang, 2025; Behera, 2024).

The Multiplexing Modulator (MM) presented in this work has already demonstrated substantial advantages in system integration, power efficiency, storage capacity, and transmission reliability. The successful completion of environmental testing and upcoming on-orbit validation further confirms its engineering maturity for future remote sensing satellite missions. Nevertheless, from the perspective of long-term scalability and deep-system evolution, several transformative opportunities remain open for exploration. In particular, the integration of Micro-Electro-Mechanical Systems (MEMS) (Niu and Feng, 2024; He et al., 2025) technology is expected to become a key enabler for the next-generation of MM, aligning with the ultimate goals of higher integration, lower power consumption, enhanced reliability, and intelligent self-maintenance (Chen et al., 2022).

6.1 RF front-end miniaturization through MEMS switching and resonant devices

Future iterations of MM can replace traditional solid-state RF switching and routing components with MEMS RF switches, phase shifters, and high-Q resonators, which offer lower insertion loss, lower actuation power, and significantly reduced size. By embedding MEMS-based reconfigurable RF paths inside the RFU and MCPDU, the MM could realize:

• Reduction in RF switching power consumption

• Lower group delay variation and improved carrier phase stability

• Multi-band reconfigurable transmission with adaptive RF routing

Such upgrades would directly benefit high-rate X-band transmission, reduce thermal stress, and enable scalable constellations with more satellites per bandwidth segment.

6.2 MEMS-enhanced reliability and autonomous health monitoring

With increased mission lifetimes and denser constellations, the MM must evolve toward self-diagnosing and self-recovering computing architecture. MEMS temperature, radiation, and vibration microsensors offer an ultra-low-power method for autonomous health perception across modules. A distributed sensor grid integrated into the PCU, HRCU, and storage arrays could enable:

• Real-time thermal gradient mapping and aging trend prediction

• Vibration-shock detection during launch and long-term fatigue monitoring

• Radiation-dose accumulation tracking for life-cycle prediction

Coupled with the existing redundancy framework, the MM could transition from fault-tolerant to fault-predictive, enabling pre-emptive switching and adaptive power modulation.

6.3 Pull-in-free MEMS actuators for redundancy switching and thermal regulation

MEMS-based micro-relays and thermal actuators can provide faster, lighter, and more efficient mechanism-level redundancy and thermal control compared to electromechanical relays. Beyond raw integration benefits, MEMS also introduce new dynamic tunability. With reference to recent progress in modified Babylonian-iteration MEMS dynamics modeling, pull-in phenomena—one of the primary lifetime constraints in electrostatic MEMS—may be mitigated or actively controlled. This opens the possibility of:

• Rapid failover switching in <100 μs

• Closed-loop thermal load balancing under varying downlink duty cycles

• Distributed heat-valving for peak-power operational phases

This capability will be critical as future payloads trend toward higher duty cycles, AI edge-processing, and 10+ year operational windows.

6.4 Toward an MEMS-driven intelligent MM architecture

Looking beyond component substitution, full convergence of RF MEMS + storage + modulation + health management could reshape the MM into a new platform class (Table 5):

Table 5

Table 5. Performance comparison after adding MEMS systems.

Ultimately, the MM may evolve into a self-optimizing communication core, capable of re-tuning its RF chain, rewiring redundancy autonomously, and extending operational lifespan without human intervention.

7 Conclusion of outlook

The current engineering implementation of the Multiplexing Modulator marks a decisive step toward spacecraft data-handling convergence. Looking forward, MEMS-level integration provides a clear and promising pathway for continued evolution—from structural miniaturization to reliability intelligence, from RF configurability to autonomous lifespan extension. With future work centered around MEMS-enhanced modulation, switching, sensing, and thermal control, the MM has the potential to become a new general-purpose transmission infrastructure for next-generation satellite clusters, supporting higher data densities, longer service windows, and more resilient mission architectures.

8 Conclusion

This paper proposes a novel standalone engineering model for space data transmission - the Multiplexing Modulator (MM). In previous space missions, multiplexers and modulators operated as separate standalone units: multiplexers aggregated multiple low-rate signals into single high-rate streams to enhance channel efficiency, while modulators converted baseband signals into high-frequency carrier waves suitable for channel transmission. This paper integrates both functionalities into a unified Multiplexing Modulator (MM), achieving substantial spacecraft electronics consolidation. The integration reduces weight by over 40%, decreases volume by 35% compared to discrete units, and power consumption by over 25%. All while maintaining space-grade reliability. The newly designed MM performs integrated processing of payload and telemetry data through multiplexing, storage, encryption, and X-band modulation before transmitting processed signals to ground stations via phased array antenna.

The novel multiplexing modulator proposed in this paper demonstrates the following innovations: high-level integration of multiplexing and modulation functionalities significantly reduces volume, weight, and power consumption in space applications, thereby freeing up more space for other spacecraft equipment; optimized hardware/software design ensures reliable operation under extreme space environments; comprehensive reliability design incorporating redundancy, thermal management, and EMC countermeasures guarantees space environmental compatibility; extensive space environment simulation testing validates equipment dependability.

Multiplexing Modulator (MM) was successfully launched in early August this year and has been on orbit for nearly 2 months now. During this period, the data transmission task remained normal without any failures or errors.

The Multiplexing Modulator (MM) presented in this work has already demonstrated substantial advantages in system integration, power efficiency, storage capacity, and transmission reliability. The successful completion of environmental testing and upcoming on-orbit validation further confirms its engineering maturity for future remote sensing satellite missions. Nevertheless, from the perspective of long-term scalability and deep-system evolution, several transformative opportunities remain open for exploration. In particular, the integration of Micro-Electro-Mechanical Systems (MEMS) technology is expected to become a key enabler for the next-generation of MM, aligning with the ultimate goals of higher integration, lower power consumption, enhanced reliability, and intelligent self-maintenance.

Data availability statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding authors.

Author contributions

WZ: Writing – original draft, Conceptualization, Writing – review and editing, Investigation. JR: Supervision, Writing – review and editing, Writing – original draft. SH: Conceptualization, Methodology, Writing – original draft. WJ: Writing – original draft, Validation, Formal Analysis. JS: Resources, Project administration, Validation, Writing – review and editing. WD: Methodology, Writing – original draft. ZD: Writing – original draft, Validation, Supervision. XM: Project administration, Conceptualization, Writing – original draft. JW: Writing – original draft, Formal Analysis, Validation. MX: Software, Writing – original draft. YZ: Writing – original draft, Investigation, Writing – review and editing. JA: Software, Writing – original draft, Conceptualization, Investigation, Writing – review and editing.

Funding

The author(s) declared that financial support was received for this work and/or its publication. This paper was supported by National Key Research and Development Program of China (Project No. 2022YFF0503903).

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

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