What Is Hpem Simulator?

An HPEM simulator is a test system that generates high-power electromagnetic fields or conducted transients in a controlled laboratory or field environment for the purpose of evaluating the susceptibility of electronic equipment, systems, and infrastructure to HPEM threats. Simulators are designed to reproduce the waveform characteristics of specific threat environments, including high-altitude electromagnetic pulse (HEMP), intentional electromagnetic interference (IEMI), and high-power microwave (HPM) sources, so that engineers can determine whether a given system will survive or continue to operate when subjected to those fields.

The development and classification of HPEM simulators is guided by IEC Technical Report IEC TR 61000-4-35, which provides a compendium of narrowband and wideband radiating and conducting test systems along with their key parameters. The field draws from high-voltage pulsed power engineering, antenna and aperture design, and electromagnetic compatibility measurement practice.

Narrowband Simulators

Narrowband HPEM simulators, also called High Power Microwave (HPM) simulators, generate fields concentrated near a single center frequency, typically transmitted in pulses on the order of microseconds. Magnetrons, traveling wave tubes, and virtual cathode oscillators (vircators) are common HPM source technologies capable of producing peak powers from tens of megawatts to gigawatt levels in the microwave frequency range. The resulting electric fields couple efficiently into apertures and cables tuned to the operating frequency.

Narrowband simulators are used to reproduce the threat from directed-energy HPM weapons and from illicitly built microwave sources that can be transported and aimed at specific targets. The HPEM threats to the smart grid article in Interference Technology notes that IEMI threats operating above 100 MHz share spectral characteristics with narrowband HPM, making narrowband simulators directly relevant for IEMI susceptibility testing of communications and control hardware.

Wideband and Ultra-Wideband Simulators

Wideband and ultra-wideband (UWB) HPEM simulators generate impulse-like fields that occupy a broad frequency range simultaneously. These systems reproduce the E1 component of HEMP and certain IEMI sources that use fast-rise-time pulses rather than microwave sinusoids. IEC TR 61000-4-35 classifies simulators by fractional bandwidth into mesoband, sub-hyperband, and hyperband categories; hyperband simulators have fractional bandwidths exceeding 163 percent and are effectively UWB impulse radiators.

UWB simulator architectures typically use Marx generators or solid-state pulsers to generate high-voltage pulses with sub-nanosecond rise times, feeding antenna structures such as half-impulse radiating antennas (half-IRAs) or transverse electromagnetic (TEM) horns. The resulting free-space pulses can reach tens of kilovolts per meter over the test volume, sufficient to replicate the worst-case E1 HEMP environment.

System-Level Testing Methodology

HPEM simulators are used in system-level testing, where the complete equipment assembly or subsystem under test is placed in the simulated field environment rather than subjecting only individual components. This approach captures coupling pathways through cables, connectors, and enclosure apertures that component-level testing misses. Test sequences follow IEC 61000-4-35 protocols specifying the field level, waveform parameters, exposure duration, and performance criteria.

Performance criteria for IEMI and HEMP susceptibility are typically graded: criterion A indicates no degradation during or after exposure; criterion B allows temporary performance reduction that recovers automatically; criterion C permits degradation that requires operator intervention to restore. Research published via IEEE on HPEM susceptibility of IT networks demonstrates how these criteria apply to network equipment tested with both narrowband and wideband simulator configurations.

Applications

HPEM simulators have applications in a range of fields, including:

• Electromagnetic hardness testing of military communications, command, and control equipment
• Critical infrastructure protection assessments for power grids and transportation control systems
• IEMI vulnerability studies for commercial buildings and public facilities
• Standards conformance testing for equipment intended for high-electromagnetic-risk environments
• Research into directed-energy effects and protective shielding effectiveness