STANDARD GAIN HORN ENGINEERING NOTE
STANDARD GAIN HORN
ANTENNA
SELECTION GUIDE
Select a standard gain horn by operating frequency first, then choose the waveguide band, nominal gain and beamwidth that fit the measurement geometry. Flange, polarization, mounting, test distance and the surrounding RF environment determine whether the horn will perform correctly in the actual setup.
SELECTION ORDER
START WITH
THE RF BAND.
A standard gain horn is tied to a rectangular waveguide band. Frequency therefore defines the first set of usable models. After the WR band is known, gain and beamwidth determine how concentrated the radiation pattern is and whether the horn fits the available test range.
WR650–WR159
1.12–7.05 GHz coverage for lower-frequency RF and microwave antenna measurement and test setups.
WR137–WR75
5.85–15.0 GHz coverage including common C-, X- and adjacent microwave test bands.
WR62–WR51
12.4–22.0 GHz coverage where alignment, cable/waveguide loss and chamber geometry become increasingly important.
WR42–WR28
18.0–40.0 GHz coverage with smaller waveguide apertures and tighter mechanical and alignment tolerances.
INTERACTIVE ENGINEERING TOOL
FIND THE
HORN FAMILY.
Enter an operating frequency and preferred nominal gain. The selector checks the current Impulse standard gain horn table and returns models whose published frequency range contains that point. Boundary frequencies can legitimately return more than one WR band.
The selector mirrors the current Impulse standard gain horn product table for model number, WR size, frequency, nominal gain and published 3 dB beamwidth. Use the controlled model datasheet and factory confirmation before final design release or procurement.
GAIN VS COVERAGE
GAIN CHANGES
THE BEAM.
Gain is not only a larger number on the datasheet. In a horn family, higher gain generally concentrates energy into a narrower angular region. The actual E-plane and H-plane 3 dB beamwidths are model-specific, so use the published values rather than assuming one universal angle for every horn.
Wider angular coverage
Useful where the setup benefits from a broader main beam or lower nominal gain. Actual beamwidth varies by WR band.
Middle ground
Balances gain and beam concentration for many measurement, calibration and antenna-test arrangements.
Tighter main beam
Higher nominal gain generally requires more careful pointing and alignment because angular coverage is narrower.
POLARIZATION & ORIENTATION
LINEAR POLARIZATION
HAS TO LINE UP.
Current Impulse standard gain horns are linearly polarized. Rotating the horn rotates its polarization axis. In a two-antenna test, polarization mismatch between transmitting and receiving antennas can reduce the measured signal even when frequency, gain and distance are otherwise correct.
Point the phase centers consistently.
Repeatable antenna measurements depend on controlling azimuth, elevation, height and the reference axis through the test setup.
Record antenna rotation.
If polarization orientation is not controlled, a change in measured level can be mistaken for a gain, cable or system problem.
Define where distance is measured.
Use a consistent mechanical or phase-center reference when establishing separation between antennas or between a horn and the DUT.
FAR-FIELD SCREENING TOOL
CHECK THE
TEST DISTANCE.
A common first-pass far-field screening estimate is the Fraunhofer distance, 2D²/λ, where D is the largest aperture dimension and λ is free-space wavelength. This is a geometry check, not a complete chamber or range qualification.
Use the actual horn aperture dimension from the controlled drawing for this calculation. Chamber reflections, quiet-zone quality, DUT size, antenna phase center, absorber performance and measurement uncertainty can require a longer or more controlled test range.
WORKED IMPULSE EXAMPLE
10 GHz.
WR90.
15 dB.
At 10 GHz, the current Impulse SGH90-15-ITI is one applicable catalog choice because its published range is 8.20–12.4 GHz. Impulse lists nominal gain of 15 dB, 29.3° E-plane 3 dB beamwidth, 29.0° H-plane 3 dB beamwidth and a Cover flange for this model.
VIEW SGH90-15-ITI→Frequency containment is only the first gate. Final selection must also account for test geometry, beamwidth, polarization, flange, mechanical envelope, mounting and the exact model specification.
MECHANICAL & TEST INTEGRATION
THE HORN HAS TO FIT
THE RANGE.
Standard gain horn selection is an RF and mechanical decision. Confirm the waveguide flange, antenna envelope, mounting arrangement, polarization orientation, surrounding clearances and test-range geometry before freezing the setup.
CPRF or Cover
Current Impulse standard horns use flat CPRF or Cover flanges depending on model. Other flange options are available by request.
VERIFY EXACT MODELChemfilm + red paint
Impulse lists clear Chemfilm and its distinctive red paint as the standard coating system for the current product line.
CORROSION-RESISTANT CONSTRUCTION1/4-20 tripod provision
The current Impulse product page states that all standard gain horn antennas include provisions for mounting to a tripod using a 1/4-20 screw.
CONTROL HEIGHT + ANGLEWG-to-coax attached
Impulse also offers horn configurations with a waveguide-to-coax adapter attached, with SMA-F, Type N-F and 2.92 mm-F options depending on configuration.
REQUEST CONFIGURATIONControl reflections
Walls, benches, fixtures, cables and nearby metal can perturb the free-space field and create measurement ripple or apparent gain error.
MANAGE MULTIPATHRepeatable boresight
Use controlled azimuth, elevation, antenna height and polarization so repeated measurements are comparable.
DOCUMENT THE SETUPCOMMON SELECTION ERRORS
WHAT GOES
WRONG.
Most selection errors are not caused by one impossible specification. They come from choosing a horn that technically covers the frequency while ignoring beamwidth, polarization, range distance, flange, alignment or the measurement environment.
Choosing by GHz and stopping there
Two horns in the same WR band can have substantially different gain and beamwidth.
Ignoring antenna rotation
Linear polarization mismatch can reduce the received level and distort comparison data.
Testing too close
Near-field behavior can invalidate assumptions made for a far-field gain or pattern measurement.
Allowing uncontrolled reflections
Nearby structures can create standing-wave ripple and apparent gain changes unrelated to the horn itself.
Wrong flange or mounting plan
The RF band can be correct while the physical interface or orientation is wrong for the fixture.
Changing the setup between measurements
Distance, height, boresight, cables and polarization must be controlled for meaningful repeatability.
RFQ / DESIGN RELEASE CHECKLIST
SPECIFY THE
HORN COMPLETELY.
A usable standard gain horn requirement should state the RF band and the test geometry, not only a nominal gain. These inputs let engineering and sales confirm the correct model and identify any required flange, adapter or radome option.
Include every required test frequency, not only the center frequency.
Confirm the horn feed matches existing waveguide hardware.
Choose the gain family that fits the test objective and geometry.
Check angular coverage and alignment tolerance using the model data.
State the required mounting or field orientation if the setup constrains rotation.
Match the installed waveguide interface and bolt pattern.
Verify the measurement geometry can support the horn and DUT aperture sizes.
Define height, support, boresight and any mechanical envelope limits.
Identify adapter, connector, protective cover or custom-interface requirements.
WR650 TO WR28.
1.12 TO 40 GHz.
10 / 15 / 20 dB.
ENGINEERING FAQ
STANDARD GAIN
HORN QUESTIONS.
These answers address the most common selection and test-integration questions for standard gain horn antennas.
How do I choose the correct standard gain horn frequency band?+
Start with the complete operating frequency range. Select a WR waveguide band whose published horn frequency range contains every required operating point, then verify gain, beamwidth, flange and mechanical requirements.
Should I choose a 10 dB, 15 dB or 20 dB gain horn?+
Choose based on the measurement objective and geometry. Higher gain generally produces a narrower main beam, while lower-gain models provide broader angular coverage. Use the model-specific E-plane and H-plane beamwidths rather than assuming one fixed angle.
What is the difference between E-plane and H-plane beamwidth?+
They are the 3 dB angular widths of the main radiation pattern in two orthogonal principal planes. Standard gain horns can have different beamwidths in the two planes, so both values matter for alignment and coverage.
Why does polarization orientation matter?+
Impulse standard gain horns are linearly polarized. If transmitting and receiving polarization axes are not aligned, the received level can drop even when frequency, distance and gain are otherwise correct.
How far apart should antennas be for a far-field measurement?+
A common first-pass screening estimate is 2D²/λ using the largest aperture dimension D and free-space wavelength λ. The final range must also account for chamber quality, reflections, phase-center behavior, DUT size and required measurement uncertainty.
What standard gain horn options does Impulse Technologies offer?+
The current Impulse product line covers WR650 through WR28 from 1.12 to 40 GHz with standard 10, 15 and 20 dB gain models. Current options also include alternate flanges, radomes and waveguide-to-coax adapter configurations by request.
