Space-Qualified EMI Filters from Crane Meeting MIL-STD-461 with Passive Design
Electromagnetic interference (EMI) management in space power systems represents one of the most critical challenges in spacecraft design. The unique operating environment of space, combined with stringent reliability requirements and the impossibility of field repairs, demands EMI filtering solutions that deliver exceptional performance while maintaining absolute reliability. Crane Aerospace & Electronics has developed a comprehensive portfolio of space-qualified EMI filters specifically engineered to meet MIL-STD-461 requirements through innovative passive component design.
The Space EMI Challenge
Space-based power systems operate in an environment where electromagnetic compatibility (EMC) is paramount. Unlike terrestrial applications, space systems cannot tolerate EMI-induced failures, as they directly impact mission success and, in many cases, represent irreplaceable assets. The conducted emissions requirements of MIL-STD-461C CE-03 establish the baseline for acceptable EMI levels, but space applications often demand performance well beyond these minimum standards.
A logarithmic frequency response chart displaying attenuation performance (dB) versus frequency (Hz) for SFME28-461, SFMC28-461, and STF28-461 filters. The chart illustrates the minimum attenuation specifications: SFME28-461 achieving 60 dB at 500 kHz and 1 MHz, SFMC28-461 providing 55 dB at 500 kHz and 60 dB at 1 and 5 MHz, and STF28-461 delivering 50 dB at 500 kHz and 1 MHz.
Crane's Passive Component Philosophy
Crane Aerospace & Electronics' approach to space EMI filtering is founded on an exclusive use of passive components, a design philosophy that provides maximum tolerance for space environment requirements. This approach contrasts with active filtering solutions that rely on semiconductor components vulnerable to radiation effects and thermal cycling.
The passive component design strategy offers several critical advantages:
Radiation Tolerance: All Crane EMI filters achieve RHA level H qualification, guaranteeing 1000 krad(Si) total ionizing dose tolerance as specified in the company's quality assurance documentation.
Thermal Stability: Operating temperature range of -55°C to +125°C ensures consistent performance across the extreme thermal cycling encountered in space missions.
Long-term Reliability: Passive components exhibit superior aging characteristics compared to active elements, critical for missions spanning decades.
Technical Specifications and Performance Analysis
SFME28-461 Series: High-Current EMI Filtering
The SFME28-461 represents Crane's flagship EMI filter, designed for high-power space applications requiring up to 10 amperes of throughput current. Operating across the full 0–50-volt range with minimum attenuation of 60 dB at both 500 kHz and 1 MHz, this filter provides exceptional EMI suppression for demanding space power systems.
The SFMC28-461 targets mid-power applications with up to 2.7 amperes throughput current capability. This filter provides 55 dB minimum attenuation at 500 kHz and enhanced performance of 60 dB at 1 and 5 MHz, making it particularly effective for applications with higher frequency EMI concerns.
Technical specifications:
Input voltage range: 0-50V
Maximum current: 2.7A
Minimum attenuation: 55 dB @ 500 kHz, 60 dB @ 1 and 5 MHz
EMI Filter and DC-DC Converter Compatibility Matrix
EMI Filter and DC-DC Converter Compatibility Matrix
Crane Aerospace & Electronics Space Power Solutions
SFME28-461 (10A)
SFMC28-461 (2.7A)
STF28-461 (0.8A)
Not Compatible
DC-DC Converter Series
Power Output
SFME28-461 (10A, 60dB)
SFMC28-461 (2.7A, 55dB)
STF28-461 (0.8A, 50dB)
SMFLHP
53-100W
✓
—
—
SMFL
40-60W
✓
—
—
SMP120
40-49W
—
—
—
SMRT
23-35W
—
—
—
SMTR
18-30W
✓
✓
—
SMHF42
8-15W
—
—
—
SMHF
8-15W
✓
✓
—
SMSA
5W
✓
✓
✓
SLH
1.5W
✓
✓
✓
SFME28-461 Specifications
Current Rating:10.0A
Voltage Range:0-50V
Attenuation:60 dB @ 500kHz & 1MHz
Dimensions:3.005" × 1.505" × 0.400"
Case Options:U (standard), V
SFMC28-461 Specifications
Current Rating:2.7A
Voltage Range:0-50V
Attenuation:55 dB @ 500kHz, 60 dB @ 1MHz & 5MHz
Dimensions:2.910" × 2.10" × 0.400"
Case Options:H, K
STF28-461 Specifications
Current Rating:0.8A
Voltage Range:0-50V
Attenuation:50 dB @ 500kHz & 1MHz
Dimensions:0.980" × 0.805" × 0.270"
Case Options:A1
Important Notes:
• All filters may be used with multiple converters up to the rated current of the filter
• All filters comply with MIL-STD-461C CE-03 conducted emissions requirements
• Compatible with MIL-STD-704 A-E 28 volt power bus systems
• Operating temperature range: -55°C to +125°C for all models
• RHA Level H (1000 krad(Si)) radiation tolerance for all EMI filters
Figure 2: Power/Current Compatibility Matrix, showing which converters work with suitable filters.
A comprehensive matrix chart displaying the compatibility between Crane's DC-DC converter series and EMI filter models. The matrix displays power ranges (0-120W) on the horizontal axis and list all converter models (SMFLHP, SMFL, SMTR, SMHF, SMSA, SLH, SMHF42) on the vertical axis. The colored cells indicate which EMI filters (SFME28-461, SFMC28-461, STF28-461) are compatible with each converter, with current ratings marked.
STF28-461 Series: Compact Low-Power Filtering
Designed specifically for low-power applications, the STF28-461 offers 50 dB minimum attenuation at 500 kHz and 1 MHz while maintaining an exceptionally compact footprint of just 0.79 square inches (5.1 cm²). This filter demonstrates Crane's ability to deliver effective EMI suppression in space-constrained applications.
Crane Aerospace & Electronics Space Power Architecture
28V Power Bus (MIL-STD-704)
EMI Filter
DC-DC Converter
Load
28V Power Bus
MIL-STD-704
EMI Filter
SFME28-461
DC-DC Converter
SMFLHP
Load
Payload
EMI Filter
SFMC28-461
DC-DC Converter
SMTR
Load
Subsystem
Filtered 28V
Regulated Output
Filtered 28V
Regulated Output
⚡
EMI Reduced
⚡
EMI Reduced
Signal Flow and EMI Suppression Process
1. Power Bus: 28V space power bus provides primary power according to MIL-STD-704 A-E specifications 2. EMI Filtering: Crane EMI filters reduce conducted emissions to MIL-STD-461C CE-03 levels 3. Power Conversion: DC-DC converters provide regulated outputs with excellent transient response 4. Load Supply: Clean, regulated power delivered to space payloads and subsystems 5. EMI Compliance: System-level EMI performance meets space mission requirements
Figure 3: EMI Filter Integration Diagram, illustrating typical space power system with EMI filters.
A detailed system block diagram illustrating EMI filter integration in a typical space power system. The diagram illustrates the 28V power bus, EMI filter placement, DC-DC converter, and load connections. The graph demonstrates how Crane's EMI filters integrate with the MIL-STD-704 A-E 28V power bus and their positioning relative to DC-DC converters and loads.
Crane's EMI filters are designed for seamless integration with 28-volt space power systems, ensuring compatibility with MIL-STD-704 A-E power bus requirements. The filters' ability to operate across the full 0–50-volt range provides margin for bus voltage variations while maintaining consistent EMI suppression performance.
Multiple converter configurations are supported, with each filter capable of supporting multiple converters up to its rated throughput current. This flexibility allows system designers to optimize both EMI performance and power system architecture.
Radiation Hardness and Environmental Qualification
Space EMI filters must withstand the harsh radiation environment encountered in various orbital and interplanetary missions. Crane's EMI filters achieve RHA level H qualification, representing 1000 krad(Si) total ionizing dose tolerance, significantly exceeding the requirements for most space missions.
Crane Aerospace & Electronics Space Power Products
RHA O (No RHA)
RHA P (30 krad)
RHA L (50 krad)
RHA R (100 krad)
RHA H (1000 krad)
EMI Filter Radiation Advantage
Crane's EMI filters achieve the highest RHA level H (1000 krad(Si)), providing 10x greater radiation tolerance than the highest DC-DC converter RHA level R (100 krad(Si)). This superior radiation hardness is achieved through exclusive use of passive components, making EMI filters ideal for the most demanding space radiation environments.
The chart shows the comparison of radiation hardness assurance (RHA) levels across Crane's product portfolio. It displays RHA levels O (no RHA), P (30 krad(Si)), L (50 krad(Si)), R (100 krad(Si)), and H (1000 krad(Si)) with corresponding total ionizing dose values. EMI filters achieving RHA level H, with comparison to DC-DC converter RHA levels.
The environmental screening process for EMI filters follows rigorous protocols outlined in MIL-STD-883, including:
Temperature cycling: 10 cycles, -65°C to +150°C ambient
Constant acceleration: 3000g
Burn-in testing: 96-160 hours at +125°C case temperature
Hermeticity testing: Gross and fine leak detection
Final electrical testing across full temperature range
Quality Assurance and Screening
Crane's EMI filters undergo comprehensive quality assurance screening available in three levels:
Prototype (non-QML): Basic environmental screening suitable for early mission phases
Class H-QML: Full qualification per MIL-PRF-38534 Class H requirements
Class K-QML: Highest qualification level with enhanced screening and documentation
Flanged Cases: All EMI filters feature flanged, side-leaded packages for secure mounting
PIN Terminal Adaptors: Available to convert side-leaded to up-leaded or down-leaded configurations
Thermal Considerations: Metal cases provide excellent thermal conductivity for heat dissipation
Hermetic Sealing: All cases are hermetically sealed for space environment protection
Vibration Resistance: Designed to withstand launch and space environment vibrations
Design Notes:
• All dimensions are maximum values for design reference
• Pin configurations and terminal arrangements may vary by case type
• Consult individual datasheets for specific pin assignments and electrical connections
• All EMI filters operate from -55°C to +125°C and achieve RHA level H (1000 krad(Si))
• Filters are qualified to MIL-PRF-38534 Class H and K requirements
Figure 5: EMI Filter Case Configurations and Dimensions, displaying all three models described with precise dimensions.
The chart is displaying the three EMI filter models (SFME28-461, SFMC28-461, STF28-461) with precise dimensional specifications. This includes top and side views with detailed measurements in both inches and millimeters. It also illustrates the pin configurations, mounting options, and case styles (U, V, H, K, A1).
Real-World Applications and Mission Heritage
Crane's EMI filters have demonstrated their effectiveness in numerous space missions, including applications in Mars Rovers, Mars Science Laboratory, Phoenix Lander, Hubble Space Telescope, and Cassini-Huygens missions. This extensive mission heritage validates the design approach and provides confidence for future space applications.
The filters' compatibility with Crane's extensive DC-DC converter portfolio enables comprehensive power system solutions, from 1.5-watt low-power applications using SLH converters with STF28-461 filters to 100-watt high-power systems employing SMFLHP converters with SFME28-461 filters.
Conclusion
Crane Aerospace & Electronics' space-qualified EMI filters represent a sophisticated solution to the challenging requirements of space power system EMI management. Through exclusive use of passive components, rigorous environmental qualification, and comprehensive compatibility with 28-volt power systems, these filters enable space system designers to achieve MIL-STD-461 compliance while maintaining the reliability essential for mission success.
The three-tier product portfolio—SFME28-461, SFMC28-461, and STF28-461—provides scalable solutions from compact low-power applications to high-current space systems, all backed by extensive mission heritage and rigorous quality assurance processes. As space missions become increasingly complex and demanding, Crane's EMI filters continue to provide the electromagnetic compatibility solutions essential for space exploration and commercial space applications.
Leveraging SAGA Components and Crane Aerospace & Electronics
Navigating the complexities of space-qualified EMI filtering, radiation hardness requirements, and power system integration demands specialized expertise. At SAGA Components, our team of application engineers, backed by strong relationships with partners like Crane Aerospace & Electronics, provides crucial support for space and defense applications. We help you:
Translate mission requirements into optimal EMI filter specifications and RHA levels.
Compare Crane's space-qualified solutions against alternatives, highlighting performance and reliability benefits.
Access detailed technical documentation and qualification data for space mission planning.
Provide samples for prototyping and validation in demanding environments.
Offer insights into layout best practices for EMI performance and thermal management.
Navigate MIL-STD-461 compliance requirements and space qualification processes.
Manage logistics and supply chain requirements for mission-critical applications.
Our deep technical expertise in space power systems, electromagnetic compatibility, and space qualification requirements enables us to assist at every stage of your design process—from initial concept through mission deployment. By partnering with SAGA Components and leveraging Crane's comprehensive space-qualified EMI filter portfolio, you can develop robust, reliable, and mission-proven solutions for even the most demanding space and defense applications.
