Neometrix / Microwave Test Facilities / Spherical Antenna Test Facility / NMX-SAF-40

NMX-SAF-40 · ENGINEERED TO ORDER — SPHERICAL NEAR-FIELD · ANECHOIC CHAMBER · NF-FF TRANSFORMATION

Measure near. Know far.

Name: Spherical Antenna Test Facility
Brand: Neometrix

An antenna's true pattern only exists far away from it — and for a large antenna, far away means hundreds of metres. No hall is that long, and no outdoor site is that clean. The spherical near-field range solves it indoors.

A probe samples everything the antenna radiates — amplitude and phase together — over a complete sphere around it. Then mathematics does what distance would have done: the sampled field becomes the exact far-field pattern, every direction at once. Around that idea we build the whole facility: shielded anechoic chamber, positioners, probes, instrumentation and software.

Discuss a range Capability note (PDF)

Shielded anechoic chamber lined with blue pyramid absorber, a horn antenna mounted on a roll-over-azimuth positioner at centre facing a probe on a vertical arch

Fig · 01 — The quiet zone. Shielding keeps the world's signals out, absorber kills the reflections, and what remains is the antenna's own field — measurable, clean, repeatable.

The idea

measure near, know farsample the sphere, transform

The room

shielded + anechoica quiet zone, engineered

The data

amplitude + phaseprobe-corrected, complete

The family

spherical, planar, compactone discipline, three geometries

Status

engineered to ordersuccessive-quoted class

ISO 9001ISO 14001Clause-by-clause complianceValidation by reference antennasIn-house engineering

Overview

Why the far field will not fit in a building.

The problem is geometry, and it gets worse exactly when the antenna gets serious.

Multi-probe measurement arch inside an anechoic chamber, a ring of small probe antennas on a curved gantry around a positioner carrying a dish antenna

Fig · 02 — The multi-probe arch. Instead of moving one probe over the whole sphere, a ring of switched probes samples it electronically. Hours become minutes.

The far field is not a place you visit. It is a result you compute — from a sphere you can actually reach.

The distance problem

Close to an antenna, the field is a churn of near effects. Only far away does it settle into the clean pattern that matters in service. How far is far? It grows with the square of the antenna's size and shrinks with wavelength. For a small antenna, a room is enough. For a large dish or array at microwave bands, the honest distance is hundreds of metres.

Outdoors at that distance, everything fights you: weather, ground reflections, other transmitters, and no repeatability worth the name. So the discipline moved indoors — and changed the question.

Three ways to bring far away inside

Spherical near-field: sample amplitude and phase over a complete sphere around the antenna, then transform. Nothing about the pattern is missed, because the whole sphere is captured. This is the most complete method, and the right one for antennas that radiate broadly — which is most of them.

Planar near-field: scan a flat surface in front of the aperture. The natural choice for large, directional antennas whose energy goes mostly forward. The scanner hardware is its own discipline — our positioners-and-scanners page covers it.

Compact range: a precision reflector collimates the beam, creating true far-field conditions in a room. No transformation needed; the reflector's surface accuracy sets the highest band it can serve.

One facility, signed data

Whichever geometry, the output is the same: patterns, gain, polarisation and phase-centre data measured with laboratory accuracy, probe-corrected, validated against reference antennas — numbers an engineer can sign and a programme can build on.

Sampledamplitude + phase, full sphere

Transformednear field to exact far field

Shieldedthe world out, reflections dead

Validatedreference antennas, repeatability

The facility

Five parts, one measurement.

Chamber, positioning, probes, instrumentation, software. Each is buyable alone; the measurement only exists when they are engineered as one.

FIG · 03SPHERICAL NEAR-FIELD FACILITY · SHIELD + ABSORB / POSITION / PROBE + MEASURE / TRANSFORM / VALIDATE

The part outsiders underrate is the last box. A range is accepted by measurement: reference antennas with known answers, measured and matched, repeatably — before any programme trusts a number from it.

1 · Shield and absorb

A welded or panel RF shield keeps outside signals out and inside signals in. Pyramid absorber on every surface soaks up reflections. The result is the quiet zone: a volume where only the antenna's own field exists.

2 · Position

A roll-over-azimuth positioner turns the antenna through every angle of the sphere, precisely and repeatably. Position accuracy becomes pattern accuracy — this is the sibling page's hardware, engineered as one system with the range.

3 · Probe and measure

A calibrated probe samples the field; microwave instrumentation captures amplitude and phase. In the multi-probe form, an arch of switched probes samples a whole cut at once — minutes, not hours.

4 · Transform

The mathematics of spherical wave expansion turns the sampled sphere into the far-field pattern in every direction — exactly, with the probe's own behaviour corrected out of the data.

5 · Analyse and report

Pattern cuts, gain, polarisation, axial ratio, phase centre — computed, plotted and archived, with every measurement traceable to its setup and calibration.

6 · Validate

Reference antennas with known behaviour are measured and matched. Repeatability is proven, not assumed. The range earns its numbers before any programme relies on them.

Work content

What the facility contains, element by element.

Read it as a checklist: a range missing a row will buy that row later, at integration prices.

Close view of blue pyramid RF absorber covering a chamber wall and floor walkway, with a reference horn antenna on a tripod in the quiet zone

Fig · 03 — Absorber is not decoration. Its shape, depth and layout decide how dead the room is — and the quiet zone is only as honest as the deadest wall.

Element	What it does	What matters
RF shielded chamber	keeps the world's signals out	shielding integrity, door design
Pyramid absorber	kills reflections on every surface	layout and depth by band
Quiet zone	the clean volume the antenna sits in	engineered, then verified
Roll-over-azimuth positioner	turns the antenna through the sphere	position accuracy = pattern accuracy
Multi-probe arch	samples a full cut electronically	speed: hours become minutes
Calibrated probes	sample the field faithfully	probe correction in the transform
Microwave instrumentation	amplitude and phase, laboratory grade	stability across long scans
NF-FF software	turns the sphere into the far field	exact expansion, not approximation
Analysis and reporting	patterns, gain, polarisation, phase centre	traceable to setup and calibration
Reference antennas	known answers for validation	the range earns its numbers
Planar option	flat scan for large directional apertures	the sibling page's scanners
Compact-range option	a reflector folds far field into the room	surface accuracy sets the top band
Test fixtures	hold the antenna without changing it	structural design is a bid class of ours
Training and documentation	operators run it; records survive audits	handed over with the range

The row that separates facilities from collections of equipment is the transform software's probe correction. Without it, the probe's own personality is stamped on every measurement. With it, the data is the antenna's alone — which is the entire point of the room.

Full specification — expand

System	Spherical near-field antenna test facility: shielded anechoic chamber, precision positioning, calibrated probes, microwave instrumentation, near-field-to-far-field transformation and validation — engineered as one measurement
The One Idea	Measure near. Know far. The far field does not fit indoors, so the range samples amplitude and phase over a complete sphere and computes the exact far-field pattern — every direction at once
Why Indoors	The honest far-field distance grows with the square of antenna size over wavelength — hundreds of metres for serious apertures. Outdoors offers weather, reflections and interference; the chamber offers repeatability
The Chamber	RF shielding keeps outside signals out; pyramid absorber on every surface kills reflections; the quiet zone is the engineered volume where only the antenna’s own field exists — designed by band, then verified by measurement
Positioning	Roll-over-azimuth positioners carry the antenna through every angle of the sphere; position accuracy becomes pattern accuracy. The positioning-and-drive hardware is the positioners and scanners page’s subject, engineered as one system with the range
Multi-Probe Form	An arch of switched probes samples a complete cut electronically instead of moving one probe mechanically — a measurement that took hours takes minutes, and production-rate testing becomes practical
The Mathematics	Spherical wave expansion: the sampled near field is transformed into the far-field pattern exactly, with probe correction removing the probe’s own behaviour from the data
What Is Measured	Pattern cuts in any plane, gain by comparison and direct methods, polarisation and axial ratio, phase centre — plotted, archived, traceable to setup and calibration
The Siblings	Planar near-field: a scanner sweeps a flat surface in front of large directional apertures. Compact range: a precision reflector collimates the beam, folding true far-field conditions into a room, its surface accuracy setting the highest usable band. One discipline, three geometries — all three are bid classes of this firm
Validation	The range is accepted by measurement: reference antennas with known behaviour measured and matched, repeatability proven across days and operators, and documentation an auditor can follow
Applications	Satcom terminals and earth stations, spacecraft antennas, telecom base stations, aircraft and airborne antennas, research laboratories and academia
Sensitive Boundaries	No sensor types, no frequency figures, no quiet-zone dimensions or reflectivity numbers appear on this page — programme-specific parameters live in programme documents. Customers are described as classes, never named
Scope Boundary	Ours: chamber and shielding, absorber engineering, positioning integration, probe and instrumentation fit, transformation and analysis software, fixtures, validation, training and documentation. Bought in: microwave instruments and absorber from their makers. The customer’s: the antennas, the programmes and the acceptance decision
Status	Work of this class is engineered to order; Neometrix has quoted against successive spherical near-field antenna test range requirements and across planar near-field, compact-range and antenna test fixture programmes, and no delivered antenna test range is claimed.

Configurations

One discipline, three geometries.

The choice is set by what the antenna is — and all three are classes this firm has bid.

Spherical

The complete answer

Sample the whole sphere; miss nothing. The right geometry for antennas that radiate broadly — terminals, arrays, spacecraft antennas — and the page's headline act.

Planar

For the big and directional

A scanner sweeps a flat surface in front of the aperture. Natural for large dishes and arrays whose energy goes forward. The scanner is the sibling page's machine.

Compact range

Far field in a room

A precision reflector collimates the beam: true far-field conditions, no transformation. The reflector's surface accuracy sets the highest band it serves.

The honest advice at specification time: choose by the antennas you will actually test, not by the biggest name on the brochure. A facility sized for the real fleet of test articles outperforms a trophy.

Where it fits

Everything that talks through the air was measured in a room like this.

The demand base runs from space programmes to phone networks.

Satcom terminals

Earth-station and on-the-move terminals live or die by pattern and polarisation purity — both are exactly what the sphere measures.

Spacecraft antennas

An antenna that cannot be fixed after launch is measured exhaustively before it. Space programmes are the range's most demanding customers.

Telecom and base stations

Modern arrays steer beams electronically; proving them takes full-sphere data at production pace — the multi-probe arch's home ground.

Aircraft antennas

Antennas live on curved, conductive airframes; measurement with representative structure shows what the installation truly radiates.

Research establishments

The bid history behind this page comes from research-establishment programmes — ranges built as national capability, used across projects.

Academia

Universities tender compact chambers and measurement systems for teaching and research — the same engineering at laboratory scale.

Antenna range control room with microwave instrumentation racks and a workstation showing a plain three-dimensional radiation pattern plot

Fig · 04 — The control room, where the sphere becomes a pattern. The plot on the screen is the far field — computed from a room the size of a garage.

FAQ

Common questions.

Longer answers, for readers who want the reasoning.

Q · 01 Why can't you just measure the antenna from far away?

Because far away is farther than you think, and dirtier than you can afford. Close to an antenna, the radiated field has not yet sorted itself out: near effects dominate, and a measurement there looks nothing like the pattern the antenna will show in service. The distance where the pattern becomes honest grows with the square of the antenna's size and shrinks with the wavelength — which is a brutal combination, because it means the distance explodes exactly when antennas get large and bands get high. For a serious aperture at microwave bands, the honest distance is hundreds of metres. Build that outdoors and every measurement inherits the weather, the ground bounce, the neighbouring transmitters and the season; repeatability — the property a programme actually pays for — is the first casualty. The near-field insight turned the problem around: you do not need to stand in the far field to know it. Sample the field completely close in, amplitude and phase together, and the far pattern follows mathematically, exactly. The measurement moves indoors, into a shielded room the size of a workshop, and distance stops being the enemy. That single idea is why nearly every antenna you rely on — in orbit, on towers, on aircraft — was proven in a chamber, not a field.

Q · 02 How does measuring near actually give you the far field?

Through one of the quietly beautiful results of electromagnetics. Any field radiating outward from a bounded source can be written as a sum of elementary spherical waves — a complete alphabet of ways energy can leave a region. Measure the field on a closed sphere around the antenna, amplitude and phase at every sample point, and you have enough information to find how much of each elementary wave the antenna emits. Once you hold those coefficients, the field anywhere outside the sphere — including infinitely far away — is a computation, not an approximation. Three practical disciplines make the theory deliver. Sampling: the sphere must be sampled finely enough for the antenna's size and band, or the alphabet is under-read — the sampling rules come from the same theory. Phase: the instrumentation must hold amplitude and phase stable across a scan that may run for hours, which is an engineering feat of cabling, references and drift correction. And probe correction: the probe is itself an antenna with its own pattern, so its personality is measured once, then mathematically removed from every measurement — without this, every result wears the probe's fingerprint. Get all three right and the transform is exact. That is not marketing language; it is the mathematics.

Q · 03 Spherical, planar or compact range — how do you choose?

By what the antenna is, and by what question you are asking it. The spherical range captures everything — the complete ball of radiation — so nothing about the pattern is invisible to it: main beam, sidelobes, back radiation, polarisation everywhere. That completeness makes it the right choice for antennas that radiate broadly (terminals, small arrays, spacecraft antennas) and for any programme that needs the whole truth. The planar range scans a flat surface in front of the aperture; it sees the forward hemisphere well and the back poorly, which is a fair trade for large, highly directional antennas whose energy genuinely goes forward — big dishes, large arrays — and its scanner mechanics suit heavy articles that are easier to hold still than to rotate. The compact range takes a different road entirely: a precision reflector collimates the source's beam so the test zone genuinely contains far-field conditions — no transformation, real-time patterns, which production lines and rapid campaigns love; the price is a precisely machined reflector whose surface accuracy caps the highest band it can honestly serve. A facility can host more than one geometry in one chamber, sharing shielding, instrumentation and software — and the bid history behind this page spans all three, which is precisely why the honest advice at specification time is fleet-first, not brochure-first.

Q · 04 What do the shielding and absorber actually do?

They manufacture silence, in two different senses. The shield handles the outside world: a continuous metal skin — welded sheets or bolted panels with conductive gaskets, filtered power entries, honeycomb air vents, and doors engineered like pressure hatches — that keeps external transmissions out of the measurement and the measurement out of the airwaves. Its enemy is the small defect: one degraded door seal can undo tonnes of steel, which is why shielding effectiveness is verified by survey, not assumed from construction. The absorber handles the room itself: without it, a metal box is a hall of mirrors, and the probe would measure the antenna plus every echo. The familiar pyramids are impedance ramps — they ease the wave from air into lossy material so gradually that almost nothing reflects; their depth sets the lowest band they can absorb, their layout is engineered per surface, with the wall behind the antenna and the specular zones treated most carefully. Together, shield and absorber produce the quiet zone: the volume where the only field present is the one the antenna itself makes. Every claim the facility will ever produce rests on the honesty of that volume — so it is designed by band, then verified by measurement, and treated as infrastructure, not furniture.

Q · 05 What does the multi-probe arch change?

The clock, and with it the economics. In the classical single-probe range, the sphere is sampled by mechanics: the positioner steps the antenna, the probe measures, and the pair repeat until the sphere is covered — a precise but patient process that can run for hours per configuration. The multi-probe arch replaces one axis of that mechanics with electronics: a curved gantry carries a ring of probes, and switching between them samples an entire arc of the sphere in the time mechanics would have spent reaching one point. The antenna then only rotates in azimuth, and full-sphere coverage arrives in minutes. What that buys is not just comfort. Antennas are no longer measured once; modern arrays are measured per beam state, per band, per configuration, and development programmes iterate. When a measurement costs minutes, engineers measure often and learn fast; when it costs an afternoon, they measure rarely and guess more. The arch's engineering burden is calibration — every probe in the ring must be known individually and the switching path corrected, so the electronic sphere is as honest as the mechanical one. Done properly, the multi-probe facility is what turns antenna measurement from a laboratory event into a production step — which is where the telecom world already lives.

Q · 06 Has Neometrix delivered one of these facilities?

Work of this class is engineered to order; Neometrix has quoted against successive spherical near-field antenna test range requirements and across planar near-field, compact-range and antenna test fixture programmes, and no delivered antenna test range is claimed. We would rather say that plainly than dress it up. The record behind the sentence: two separate spherical near-field range establishments bid for research-establishment programmes, a planar near-field range, a compact antenna test range, and the structural design and realisation of antenna test fixtures — each answered clause by clause. Around those bids stands adjacent engineering this site shows in depth: the positioners-and-scanners line that is the motion half of every range, the EMI/EMC laboratory discipline of shielded rooms, absorber and quiet measurements, precision structural and drive engineering across dozens of delivered machines, and test-facility integration as the house trade. The honest shape of a first range contract is the one the buyers' own pattern defines: compliance stated line by line, the facility proven by reference-antenna validation and repeatability on site, operators trained, documentation complete. That is the basis we would bid on, and the page claims nothing more.

Q · 07 How does this page relate to the positioners-and-scanners page?

As facility to subsystem, and the split is deliberate. This page is the whole measurement: the shielded room, the absorber, the probes and instrumentation, the transformation software, the validation — the thing a programme buys when it says "establish a range". The positioners-and-scanners page is the precision motion inside it: roll-over-azimuth positioners, planar scanner mechanics, drives and controllers — machinery that is a discipline in its own right, with its own engineering standards, and that also sells separately, because ranges are upgraded piecemeal and positioners outlive electronics. The claims are split the same honest way: the range-establishment bid history lives on this page, because those tenders bought facilities; the sibling page carries the positioning-and-drive competence that sits inside them. One set of tenders, one home per claim — the same no-double-counting rule this whole catalogue follows. Practically, read them together in whichever order your problem arrives: buying or upgrading a complete range, start here and follow the link for the motion hardware's depth; upgrading only the mechanics under an existing range, start there and follow the link back when the campaign grows into shielding, probes or software.

Q · 08 What does it take to trust a range's numbers?

A validation habit, exercised before anyone needs the numbers. A range is a measuring instrument the size of a building, and like any instrument it must be proven against known answers. The tools are reference antennas — standard gain horns and well-characterised articles whose behaviour is established — measured in the new facility and compared against their known patterns and gain. Agreement earns trust; disagreement starts an investigation of the usual suspects: quiet-zone cleanliness, probe calibration, cable stability, positioner accuracy, sampling density. Beyond the first proof come the habits that keep trust alive. Repeatability studies: the same article, measured across days, operators and re-mounts, must return the same answers within stated bounds. Drift discipline: instrumentation references checked, cables exercised and re-verified, because phase stability decays quietly. Records: every measurement traceable to its setup, calibration state and software version, so a number can be defended years later. And periodic re-validation, because absorber ages, doors wear and instruments drift. This is the same calibration-culture that runs through our test-laboratory pages, applied at room scale — and it is why the acceptance of a range is itself a measurement campaign, not a handover ceremony.

The motion, the silence, and the vacuum.

Three neighbours in the measurement world.

↗ The motion

Antenna Positioners & Scanners

The precision mechanics inside every range — this facility's moving half, in its own depth.

↗ The silence

EMI / EMC Test Laboratory

Shielded rooms and absorber in their other life — proving electronics quiet and immune.

↗ The vacuum

Thermal Vacuum Chamber

The other room spacecraft hardware must survive before it flies.

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Get a quotation

Tell us the antennas, the bands,
and the pace you must measure at.

The projects desk replies within two working days with a clause-by-clause compliance matrix and a budgetary quotation. Write to [email protected] or use the form.

Enquire — antenna test facility Capability sheet (PDF) +91 7777 876 876

ISO 9001 / 14001 ENGINEERED TO ORDER — SPHERICAL ANTENNA TEST FACILITY SHIELD · POSITION · PROBE · TRANSFORM · VALIDATE · MEASURE NEAR, KNOW FAR ENGINEERED IN NOIDA · INDIA

Measure near. Know far.

Why the far field will not fit in a building.

The distance problem

Three ways to bring far away inside

One facility, signed data

Five parts, one measurement.

1 · Shield and absorb

2 · Position

3 · Probe and measure

4 · Transform

5 · Analyse and report

6 · Validate

What the facility contains, element by element.

One discipline, three geometries.

The complete answer

For the big and directional

Far field in a room

Everything that talks through the air was measured in a room like this.

Satcom terminals

Spacecraft antennas

Telecom and base stations

Aircraft antennas

Research establishments

Academia

Common questions.

The motion, the silence, and the vacuum.

Antenna Positioners & Scanners

EMI / EMC Test Laboratory

Thermal Vacuum Chamber

Tell us the antennas, the bands,
and the pace you must measure at.

Similar Products

Share This Page

Measure near. Know far.

Why the far field will not fit in a building.

The distance problem

Three ways to bring far away inside

One facility, signed data

Five parts, one measurement.

1 · Shield and absorb

2 · Position

3 · Probe and measure

4 · Transform

5 · Analyse and report

6 · Validate

What the facility contains, element by element.

One discipline, three geometries.

The complete answer

For the big and directional

Far field in a room

Everything that talks through the air was measured in a room like this.

Satcom terminals

Spacecraft antennas

Telecom and base stations

Aircraft antennas

Research establishments

Academia

Common questions.

The motion, the silence, and the vacuum.

Antenna Positioners & Scanners

EMI / EMC Test Laboratory

Thermal Vacuum Chamber

Tell us the antennas, the bands,and the pace you must measure at.

Similar Products

Share This Page

Tell us the antennas, the bands,
and the pace you must measure at.