5G NR OTA (Over The Air) Testing Introduction · 2019-10-18 · White box testing - device is a...

5G NR – OTA (Over The Air) Testing Introduction

Günter Pfeifer

Market Segment Manager – Wireless Communication

5G New Radio Seminar Americas, May 2019

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Testing OTA? – Easy, just cut the cord…

May 2019 5G NR – OTA Overview 2

and replace it with an

antenna…

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OTA measurements

in far field**Note: Alternative near field methods are not precluded

Conducted testing

Re-use LTE UE

testing methodology

Why OTA testing?

3GPP TR 38.803 NR RF testability

6 GHz 24 GHz

Source: 3GPP TR 38.803 V2.0.0

Only antenna performance

tested requires

over the air (OTA)

[TRP, TIS, …]

Everything to be tested

over the air (OTA)

5G NR – OTA Overview 3May 2019

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ı 5G NR addresses – besides others – eMBB (enhanced mobile broadband)

ı eMBB means data rates of 20Gbps

ı Needs wide bandwidth (Shannon‘s law)

ı Contiguous wide bandwidth available at high frequencies (mmW bands)

ı High frequencies – high path loss

ı Counter measure – beamforming techniques

ı Beamforming needs active antenna arrays with multiple phase steered

antennas

ı Phased arrays do not allow cable connections

ı Testing can only be done wirelessly – over the air - OTA

Why is OTA such an important topic for 5G NR?

5G NR – OTA Overview 4

eMBB

BW

mmW

pathloss

beamforming

AAS

OTA

May 2019

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It’s all about no cables….in 5G mmWave systems

ı Phased arrays do not allow

connection through cables

Many antennas –

many connectors

Cable influences

antenna characteristics

Antenna becomes system

relevant functionality with

beamforming etc.

3D gain patterns of mmWave UE antenna

No measurement cable With measurement cable

Antenna couples to all surrounding objects

Conductive measurements introduce large error


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New challenges coming up with OTA testing

ı Testing in OTA is not new

ı So far below 6GHz antenna performance tests only

ı Now EVERYTHING has to be tested OTA

ı Frequencies in mmWave

ı Lots of new things to consider

Radiation pattern of the antenna

Field properties of the radiation

Near field vs. far field conditions

Quiet zone sizes

Chamber sizes

Positioners

…


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Radiation properties

ı Each antenna or antenna element emits a multitude of spherical waves

ı As the waves are travelling away from the antenna their energy locally decreases with the distance

from the antenna as it distributes over an increasing sphere

ı At a given point far enough away from the antenna the emitted wave looks plane within certain limits

- this region is called the “quiet zone”

Compare with throwing a stone into water

ı To increase the size of the quiet zone there are several options

Move further away from the antenna

Manipulate the field distribution

Use overlapping fields from multiple antennas

…

75G NR – OTA OverviewMay 2019

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Fundamental properties: electromagnetic fields

0.1 m apperture size at 28 GHz

Radiated near field region

Phase & magnitude

Far field

MagnitudeReactive near

field region

2𝐷2

𝜆= 1.87 𝑚

5G NR – OTA Overview

0.62𝐷3

𝜆= 19 𝑐𝑚*

* = formula commonly taken for radiators with D>𝜆

2May 2019

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What is the quiet zone?


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How good is the quiet zone?


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Reactive near field – radiated near field – far field

ı Reactive near field close to the antenna

Every object couples with the antenna - influences the antenna pattern and performance

ı Far field (beyond )

Field is considered as locally planar

RF measurements are easy - only magnitude measurements

ı Between these two point radiated near field

Waves are not plane - measurements in magnitude and phase

Entire sphere has to be measured to understand field distribution

For transformation to far field

Typically use of a positioner

Measurement more complex and time consuming, setup more expensive

11

D = size of radiating aperture

λ = wavelength

2𝐷2

𝜆


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Measurements that can be performed in the reactive near field

ı No RF parametric measurements like EVM, ACLR etc.

ı Stay away from the reactive near field

ı Measurements would influence the result since antenna pattern is influenced

ı Things like SAR measurements are performed here


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Measurements that can be performed in the radiated near field

ı Spherical scan of the entire field in magnitude and phase

All field parameters are known

Can then be mathematically transformed into the far field by using certain algorithms

All Tx measurements

Effort much higher than in far field

Space requirements are lower

ı Directly in radiated near field (without far field transformation)

Only some certain parameters can be measured

TRP (Total Radiated Power)

Peak EIRP (Equivalent Isotropic Radiated Power)

ACLR

Measurement uncertainties higher than in far field


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Solution transforming NF to FF by Software algorithm

14

Complex near-field

SW algorithm

Amplitude Phase

Plane wave far-

field received

𝑓𝑥,𝑦 = 𝐴ඵ𝐸𝑥,𝑦𝑒+𝑗𝐤∙𝐫 𝑑𝑥𝑑𝑦



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Near-field to Far-field Transformation – FIAFTA

Performance ComparisonFeatures Transformation

High precision positioner

vs.

220 minutes6 minutes

Fast Spiral Scan

angular resolution 0.1°

NF-FF transformation


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Measurements that can be performed in the far field

ı Measurements in the far field

Comparably easy

Every RF measurement can be performed

EiRP/EiS (Effective isotropic Radiated Power/Sensitivity)

In beam measurements for R&D and Production

EVM, ACLR, SEM, OBW, BLER etc.

Far away from antenna

Additional challenge - path loss typically high for direct far field


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Direct FF measurement Systems

Device

Under

Test

3D Rotation of DUT

DUT-MEAS Antenna Separation: R > 2D2/λ

Dual-Polarized High-Gain

Antenna

Far Field

Magnitude

Single Measurement point


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CTIA CompliantPre-Compliant

WPTC-XS WPTC-S WPTC-M WPTC-L WPTC-XL

Wireless Performance Test Chamber (WPTC) Overview

Wireless Performance Anechoic Test Chambers for mmWave

2,4x2,4x2,43,5x3x3m

4,6x3,7x3,5m

5,2x4,2x4m

5,8x5,2x5,1m

Far-field: 5G UE/CPE Test Far-field: 5G Basestation Test


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Quiet Zone Size

ı How big of a quiet zone is required in far field?

ı Depends on frequency and size of radiating aperture

Fraunhofer distance

19


λ = wavelength

2𝐷2

𝜆


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What size of a quiet zone (QZ) is needed?

ı Size and position of the antenna known

This size can be taken as D

White box testing - device is a “white box” for the user

since position of the antenna is known

e.g. QZ size 3 cm; 30 GHz λ = 1cm ; far field distance 18 cm

ı Size and/or position of the antenna is unknown

Entire DUT maximum distance to be considered as D

Black box testing - device is a “black box” for the user

e.g. QZ size 12 cm; 30 GHz λ = 1 cm; far field distance 2.9 m


λ = wavelength

2𝐷2

𝜆

D=

12 cm

D= 3 cm

2𝐷2

𝜆


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How big of a chamber is required for direct far field?ı Quiet zone size (black box)

ı Chamber size 3 m…5 m

ı Quiet zone size (white box)

ı Chamber size 0.5 m

12 cm


D= 3 cm

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How to reduce the far field distance?

ı Indirect far field methods

To overcome challenge of high path loss in far field

ı CATR (compact antenna test range)

Perform transformation of field to far field conditions using hardware

Leads to far field conditions in smaller chamber size

Typically bigger quiet zone

ı Same measurements as in far field


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Far-field to near-field systems: hardware Fourier transforms

Complex near-field

wave generated

Fresnel Lens (Fourier Optics) Reflector: Compact Antenna Test Range Array: Plane Wave Convertor

Amplitude PhasePlane wave far-

field received



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Possibilities to shrink the chamber size –

indirect far field

Feed

Reflector

DUT


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CATR – Compact Antenna Test Range

Feed horn

Spherical wave

~ ½ N cm quiet zone

Plane waves


N cm CATR

reflector

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CATR is a Bi-directional Device

26

From: Reflector Focal Point (Feed)

To: Reflector and DUT Quiet Zone

From: DUT Quiet Zone

To: Reflector Focal Point (Feed)

Reflector transforms spherical field

from focal point (feed antenna) into a

planar wave in front of reflector to

quiet zone

Reflector is a spatial filter that extracts

the planar components of the spherical

wave from DUT and focuses them at

the focal point (feed antenna)

Quiet Zone

Quiet Zone

Device

Under

Test

Forward: DUT Receives

Reverse: DUT Transmits

May 2019 5G NR – OTA Overview

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Top View

Path Loss in CATR Systems

27

Free Space Path Loss:

from Feed to Reflector

FSPL: Different FF paths

to upper and lower

portions of reflector

Amplitude Taper of Feed

Antenna (HPBW)

Vertical QZ Taper

Horizontal QZ Taper

Side View

d1

d2

d0

d1 < d0 < d2

(d)

frequency

d1 > d0 < d2


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Path Loss in CATR Systems

28

Quiet Zone

Reflector Near Field

P. Walt “The power density in the

radiating near field region of directive

antennas”, 2012

Power Density is constant up to: 0.25D2/l

800B/R (D = 20cm): 1 meter @30GHz

1800C (D = 30cm): 2.25 meters @30GHz

Feed Antenna (low-gain) Far Field: FSPL

Reflector Far Field

800B/R: 8 meters

1800C: 18 meters

No Path Loss from Reflector to DUT

Parabolic Reflector Power Density

ITU-R BS.1968 (2005)


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CATR Reflector Error: Edge Treatment (Low Frequency & QZ)

W. Burnside “Curved Edge Modification of Compact Range Reflector”, IEEE 1987

Wave ‘bends’

around corner

No scattering of energy

back into quiet zone

Quiet Zone

Amplitude Ripple

Rolled Edges

Low Scattering

Knife Edge

High Scattering

High

scattering of

energy into

quiet zone

Ei: Initial EM field (from feed horn)

Ei

Ei

Corner forms

a point source

Es

Es: Scattered EM field (from edges)

Es

5G NR – OTA OverviewMay 2019 29

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CATR Reflector Errors: Surface Roughness (High Frequency)

Ideal Actual

ρmax

5G NR – OTA OverviewMay 2019 30

Maximum FrequencySurface Roughness

(microns)

28 GHz 75

43 GHz (in band) 49

87 GHz (spurious emissions) 24

220 GHz (FCC 5th Harmonic) < 1

Surface roughness

Measurement:

• Rqmax < 1 micron

(RMS)

• Ra < 1.6 microns

(arithmetic average)

• Rzmax < 45 microns

(peak2peak)

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ATS800B – CATR Benchtop test setup

WPTC


Comparable QZ size in DFF

8m @ 30 GHz

May 2019

ı Application: basic antenna R&D, education

ı Frequency range: 20-50 GHz

ı Quiet zone: D 20 cm

ı Dimensions: 120x60x80cm

ı Maximum DUT size: 40x40 cm (laptop)

ı Reflector <1um surface roughness

ı Optional 2D positioner

ı Wide band feed antennaNo shielding

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ATS800R – CATR Rack-Mounted Test Chamberı Application: chipset and mobile phone R&D

ı Frequency range: 20-50 GHz


ı Dimensions: 80x100x210 cm (rack)



ı Optional 3D positioner

ı Wide band feed antenna

32

Height =

2.1m (6ft 10”)

Depth =

1m (3ft 3”)

Width =

0.8m (2ft 7”)

Reflector Rack Mounting

Adjustable Tilts in 2 planes


Shielding efficiency

~ 50..60dB

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ATS1800C - full conformance / compliance testing solutionı Application: 3GPP conformance

ı Frequency range: 18-87GHz


ı Dimensions: 90x150x210 cm



ı 3D great circle cut positioner

ı Wide band feed antenna

Comparable QZ size

in DFF

18 m @ 30 GHz


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ATS1000 – fast and compact mmW OTA solution

ATS1000

ı Compact conical cut concept dedicated to mmW DFF

and NFFF

ı <0.1° positioner accuracy and laser alignment ensure

high radiation pattern measurement accuracy

ı DUT: devices up to 14’’ and 20 kg

ı Current frequency coverage: 18 GHz to 50 GHz

ı Cable management through rotary joint and energy

chain

ı TRP test at 28 GHz with 4 degree angular step takes

about 7 min1.53 m

5ft0,85 m

2ft 9“

1.99 m

6ft 6“


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OTA test in extreme temperature conditions

ı Active antenna arrays

Amplifiers and phase shifters for beam forming and beam steering

Temperature sensitive

Accuracy in forming beams influenced by operation temperature

OTA tests in different temperature conditions

ı Temperature tests in OTA chamber is difficult

Volume of air to be heated or cooled is big - takes a long time to reach stable temperature

Absorbers and positioning motors do not like very high or very low temperatures

ı Thermal solution avoiding these problems

Climate bubble installed inside OTA chamber ATS1000

Climate controlled by an external thermal stream


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ATS1000 full 3-D OTA solution for extreme conditions

ı Full spherical measurement under

controlled temperature condition

from -40°C to +85°C

ı 100°K temp change within approx.

10 minutes (-40…+60 / +85…-15)


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ATSx series overviewATS800B ATS800R ATS1000 ATS1800C

Application Benchtop R&D R&D R&D +preconformance Conformance

Main frequency range 20-50 GHz 20-50GHz 18-87 GHz 18-87 GHz

Quiet zone (@1 dB

amplitude taper)

D 20 cm D 20 cm D 7 cm D 30 cm

Automation/Positioner 2D positioner 3D positioner 3D conical cut 3D great circle cut

37May 2019 5G NR – OTA Overview

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R&S CMQ200 shielding cube key facts

Ready for 5G and extra technologies -> absorber range 20 to 75 GHz

Prepared for automated handling -> drawer concept with automatic opening

Robust for million cycles -> solid, well known design

Reduced floor space -> fits into 19” racks

Scalable for most DUT’s -> smart devices , CPEs, RFICs, prototypes

Efficient for big lot sizes -> layouts with simplified geometry

Flexible for small lot sizes -> layout with floor positioner

Integrated OTA solution with CMP200/RRH -> reliability + efficiency


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R&S 5G NR OTA Solutions

Antenna Design• Highest Bandwidth

• Flexible system

Early Stage R&D • High Test Speed

• Climatic Testing

R&D / Regression• Cost efficient

• Space for instruments

RF Conformance• large QZ

• IB/OOB up to 90GHz

mmW Production• One stop shop solution

• High automation

WPTC ATS1000 ATS800 ATS1800C CMP200

CMQ200


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OTA testing fundamentals poster


Download at

www.rohde-schwarz.com/OTA-poster

www.mobilewirelesstesting.com

May 2019

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http://www.rohde-schwarz.com/OTA-poster

http://www.mobilewirelesstesting.com/


“If you want to go fast, go alone. If you want to go far, go together!”

African proverb

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5G NR OTA (Over The Air) Testing Introduction · 2019-10-18 · White box testing - device is a...

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