What is a passive horn antenna and how does it work for EMC testing?

A passive horn antenna is a flared waveguide aperture antenna that transitions electromagnetic energy between a guided transmission line (coaxial cable or waveguide) and free space. The flared horn geometry provides a directional radiation pattern, moderate-to-high gain, low VSWR, and broad bandwidth without any active components or tuning. In EMC testing, horn antennas serve a dual role: for radiated emissions, they receive electromagnetic energy from the Equipment Under Test (EUT) and deliver it to the EMI receiver for measurement; for radiated immunity, they transmit amplified RF power toward the EUT to generate the required test field strength. This dual emissions/immunity capability makes passive horns the most versatile antennas in a microwave EMC laboratory. Because they contain no active electronics, they can safely handle the high RF power levels required for immunity testing — up to 800W CW depending on the model.

What frequency range do Com-Power passive horn antennas cover?

Com-Power offers passive horn antennas covering 200 MHz to 40 GHz across six models. The AH-220 covers 200 MHz–2 GHz (MIL-STD-461 RE102 optimized). The AH-118 covers 1–18 GHz (usable from 700 MHz), the most versatile general-purpose horn. The AH-8055 covers 800 MHz–5 GHz for high-gain cellular/WiFi/5G immunity. For millimeter-wave testing, the AH-826 covers 18–26.5 GHz, the AH-640 covers 26.5–40 GHz, and the AH-840 covers 18–40 GHz in a single wideband antenna. Together, the AH-220 + AH-118 + AH-840 can cover 200 MHz to 40 GHz with just three antennas, providing complete EMC test coverage from UHF through Ka-band.

Which EMC standards require passive horn antennas?

Passive horn antennas are specified or referenced across a wide range of EMC standards. MIL-STD-461 RE102 (200 MHz–18 GHz segment) specifies horn antennas with exact aperture dimensions — the AH-220 meets the 69 × 94.5 cm requirement for the 200 MHz–2 GHz band. MIL-STD-461 RS103 (radiated susceptibility) requires high-power horn antennas for field generation. RTCA DO-160 Sections 20/21 (avionics radiated emissions and immunity) reference MIL-STD-461 procedures. CISPR 16-1-4 specifies horn antennas for 1–18 GHz emissions. IEC 61000-4-3 (radiated immunity 80 MHz–6 GHz) requires horn antennas for field generation. ISO 11452-2 (automotive immunity) specifies horn antennas for 200 MHz–18 GHz testing and requires field strengths up to 200 V/m. ANSI C63.4 references horn antennas for microwave emissions above 1 GHz.

What power levels can passive horn antennas handle?

Com-Power passive horn antennas are rated for continuous wave (CW) power levels ranging from 10W to 800W depending on the connection method and model. The AH-220 handles 800W CW via its N-type coaxial connector — the highest coaxial-fed rating in the lineup. The AH-8055 handles 450W CW. The AH-118 handles 300W CW. The mmWave horns (AH-826, AH-640, AH-840) handle 200W via direct waveguide connection, or 10W with the removable coaxial adapter. For high-power immunity testing requiring more than 10W at mmWave frequencies, the waveguide flange must be used directly by removing the coaxial adapter. The coaxial 10W limit at mmWave applies specifically to the 2.92mm (K-connector) adapter, not the antenna structure itself.

What is the difference between passive and active horn antennas?

Passive horn antennas contain no active electronics — they are purely mechanical/RF structures. Their key advantages are: high power handling (up to 800W) for immunity testing, no battery or power supply required, wide dynamic range, and rugged construction. The trade-off is that they provide no signal amplification, so emissions measurements require an external preamplifier for best sensitivity. Active horn antennas (such as the Com-Power AHA-118 and AHA-840) incorporate a built-in low-noise preamplifier powered by an external supply. This significantly improves receive sensitivity for emissions measurements, but limits their input power to a few milliwatts — making them unsuitable for immunity testing. For a complete EMC lab, passive horns are typically chosen for immunity testing (and emissions when sensitivity requirements are met), while active horns are chosen when maximum emissions sensitivity is the priority.

How do I connect a horn antenna for coaxial vs waveguide applications?

The connection method depends on the power level and frequency. For coaxial connection (all AH-118, AH-220, AH-8055 models, and mmWave models at low power): use a standard Type-N cable for models below 18 GHz, or a 2.92mm (K-type) cable for mmWave models. Coaxial connections are simpler and use standard test equipment cables. For waveguide connection (AH-826, AH-640, AH-840 at high power): remove the removable coaxial adapter to expose the WR-42 or WR-28 waveguide flange, then connect directly to a waveguide-output amplifier or waveguide transition. Waveguide connection enables 200W power handling and reduces cable loss at mmWave frequencies. For any high-power immunity application, always verify that all connectors and cables are rated for the intended power level before energizing the system.

Which horn antenna should I choose for 5G testing?

5G EMC testing spans two distinct frequency ranges: FR1 (sub-6 GHz) and FR2 (mmWave, 24–40 GHz). For FR1 emissions and immunity, the AH-118 (1–18 GHz) covers all FR1 bands from n1 through n79. For high-power FR1 immunity (5G base station testing, automotive 5G OTA), the AH-8055 (800 MHz–5 GHz) provides the highest gain and field strength in the cellular/WiFi range. For FR2 mmWave testing, the AH-840 (18–40 GHz) is the recommended single-antenna solution, covering n257 (28 GHz), n258 (26 GHz), n260 (39 GHz), and n261 (28 GHz) without antenna changes. If budget is a constraint and only specific mmWave bands are needed, the AH-826 (18–26.5 GHz) or AH-640 (26.5–40 GHz) can be purchased individually.

Are Com-Power horn antennas individually calibrated?

Yes. All Com-Power passive horn antennas are individually calibrated per ANSI C63.5 or SAE ARP-958 with NIST traceability, and a calibration certificate with antenna factor and gain data is supplied with each antenna. ISO 17025 accredited calibration is available upon request for customers whose quality systems require it. Each antenna includes calibration data specific to that unit — not generic model data — which is loaded into the EMI receiver so it can automatically apply the correct antenna factor corrections during measurements. All models carry a three-year standard warranty. Annual recalibration is recommended to maintain measurement traceability, particularly for accredited test laboratories.

📢 AH-118: 1–18 GHz Broadband Horn (300W)

Applications: General-purpose 1–18 GHz emissions and immunity testing, WiFi 2.4/5/6 GHz, 5G FR1 (n1–n79), ISM bands, satellite C/X/Ku-band emissions, radar, MIL-STD-461 RE102 (above 200 MHz), FCC Part 15/18, CISPR 22/32, ANSI C63.4, DO-160 radiated emissions.

📢 AH-220: 200 MHz–2 GHz MIL-STD-461 Horn (800W)

Applications: MIL-STD-461 RE102 radiated emissions (200 MHz–2 GHz), RS103 radiated susceptibility, military and aerospace equipment testing, high-power immunity exceeding 200 V/m, RTCA DO-160 avionics, defense contractor compliance testing.

📢 AH-8055: 800 MHz–5 GHz High-Gain Horn (450W)

Applications: Automotive immunity ISO 11452-2 (200 V/m requirement), DO-160 Category Z extreme HIRF, safety-critical system testing, RS103 high-field military, cellular and WiFi high-power immunity.

📢 AH-826: 18–26.5 GHz mmWave Horn (200W waveguide / 10W coax)

Applications: 5G FR2 mmWave testing (24–26.5 GHz), automotive 24 GHz short-range radar emissions, satellite Ka-band, mmWave immunity, 5G base station and UE emissions.

📢 AH-640: 26.5–40 GHz Extended mmWave Horn (200W waveguide / 10W coax)

Applications: 5G mmWave 28/39 GHz testing, satellite Ka-band (26.5–40 GHz), automotive 77 GHz radar harmonic emissions, E-band microwave links, mmWave research and pre-compliance screening.

📢 AH-840: 18–40 GHz Wideband mmWave Horn (200W waveguide / 10W coax)

Applications: Complete 5G FR2 testing across all bands (n257/258/260/261), automotive radar 24 GHz and 77 GHz harmonics with a single antenna, satellite Ku/Ka-band, broadband mmWave emissions and immunity, lab equipment consolidation.