Comba Telecom White Paper - Quality Control Analysis of Base Station Antennas

1 © 2015 Comba Telecom. All Rights Reserved

QUALITY CONTROL ANALYSIS OF BASE

STATION ANTENNAS

July 2015

A Comba Telecom White Paper


TABLE OF CONTENTS ABSTRACT AND NOTES ..................................................................................................................... 3

INTRODUCTION ............................................................................................................................... 4

KEY FACTORS INFLUENCING ANTENNA QUALITY .................................................................................... 4

ANTENNA MANUFACTURING QUALITY CONTROL AND ASSURANCE ........................................................... 4

Software Criterions .................................................................................................................................. 5

Design Software ......................................................................................................................... 5

Management Tools .................................................................................................................... 5

Comprehensive Quality Control System for Product Life Cycle Management .......................... 6

Hardware Facilities ................................................................................................................................... 6

Margin and Tolerance Definition and Control ........................................................................... 7

Quality Materials—Advanced Material Testing Equipment and Scientific

Inspection Method ..................................................................................................................... 7

Strict Procedure Quality Control: Multiple Quality Supervision Aspects ................................... 8

Strict Quality Control Procedure: Component Manufacturing Equipment ................................ 8

ASSURANCE OF ANTENNA PERFORMANCE TESTING ................................................................................ 9

Radiation Parameter Testing Field and Requirements (Far-Field and Compact Range) ........................ 10

Radiation Parameter Testing Field and Equipment Requirement (128 Probes Spherical

Near-Field) ............................................................................................................................................ 11

Requirements of Electrical Test Environment and Equipment .............................................................. 11

SUMMARY ................................................................................................................................... 11

ABOUT COMBA TELECOM ............................................................................................................... 12


ABSTRACT AND NOTES

An unsung hero, the base station antenna is at the core of any wireless

network. Often the final link to end-user devices, the antenna performance

can make or break a network regardless of the robustness of the underlying

baseband technology. It is therefore imperative that mobile network

operators have an understanding of the key indicators of antenna quality and

the underlying processes behind ensuring such quality in order to assess their

antenna solution partners.

This article therefore discussed the factors that impact the antenna quality. It

looks into various aspects of antenna quality assurance including design,

production, testing equipment and facilities. It provides thoughtful ideas for

research and analysis of antenna quality control.

This paper was presented by Comba Telecom as “Quality Control Analysis of

Base Station Antenna” at the 7th

International Conference on

Communications and Networking in China 2012 (“Chinacom”).

Original author credits: Bu Binlong, Lin Xuejin, Carol Ye.


INTRODUCTION The base station antenna is one of the most important components in a

mobile communications system, and the antenna quality has direct impact

on the overall performance of the wireless network system. The network

quality cannot be assured unless antenna quality can be effectively

controlled. Therefore in order to implement effective quality control, there is

a need to analyze and discover relevant factors that determine BTS antenna

performance and quality, such as antenna structure, material, process and

assembling levels, etc. and find ways to ensure high quality antenna.

KEY FACTORS INFLUENCING ANTENNA QUALITY The antenna quality is mainly decided by the design and manufacturing

standards. Under the premise of good antenna design methodology, antenna

structure, material, process and assembling determine the stability, reliability

and durability of antenna performance.

In short, high quality antennas must possess the following three conditions:

1. Excellent design methodology and advanced manufacturing

technique.

2. Good consistency of material, assembly and welding.

3. Strict process control of production work flow and quality inspection.

ANTENNA MANUFACTURING QUALITY CONTROL

AND ASSURANCE In order to manufacture good quality antennas, software and hardware

facilities are necessary. The criteria for good quality antennas are measured

by -high production efficiency and one-time pass rate for electrical

parameters:

1. There must be basic infrastructure established for the software and

hardware including design, material inspection, manufacturing

process control, parameters testing, environmental and reliability

testing and verification, etc.

2. Manufacturing Key KPIs:

• One-time pass rate (Electrical parameters): refers to pass rate

without tuning after assembling. It is one of key KPIs that directly

reflects capabilities of design and manufacturing quality control.

• Number of antennas output and one-time pass rate per unit time:

these two parameters can directly reflects production efficiency

and design quality.


SOFTWARE CRITERIA

DESIGN SOFTWARE High-quality antenna design requires highly efficient electromagnetic and

mechanical simulation software supported by superfast and advanced

workstation to support. An accurate electromagnetic simulation software,

intelligent post-processing optimization software and mechanical simulation

software can achieve high efficiency and accurate results and provide

assurance for excellent electrical specs and reliable mechanical structure.

Due to the complexity of the antenna physical models, Maxwell Equations

and mechanical structures, in order to accomplish the calculation, multi-CPU

need to run in parallel and process data simultaneously. In this case, super

power workstations with massive capacity are required.

Figure 1: Design software simulation interface

MANAGEMENT TOOLS It is difficult to ensure quality products effectively just by human resources,

as quality control involves not only people, but also tools, standards, material

and process. Therefore, advanced management tools must be implemented

in order to achieve effective information transfer, problem tracking, and

document and data control and management. Please refer Figure 2 for

details:

Quality Control System Supporting

management tools

Main functions

Design process control

PDM

Management tools that control from product development project launch to release, ensure customer’s requirements can be met in the development stage.

Pilot and small batch production

Material control

SPC and MES

Incoming material inspection and automatic data collection and analysis for manufacturing process control, to find the root cause of quality issue and solutions

Production process control

Post-Sales Quality Tracking QDM

Quality data management platform for the sold products, to collect customers’ feedbacks and provide fast response to problems and issues.


Figure 2: Margin and Tolerance Definition and Control Flow

COMPREHENSIVE QUALITY CONTROL SYSTEM FOR PRODUCT LIFE CYCLE

MANAGEMENT A comprehensive life cycle management system can provide the assurance of

product quality cross over all the stages including design and development

process, pilot and small-batch production, supplier chain management and

incoming material control, production process control, etc. The procedure

and phases will be managed by program, standards, and documentation.

HARDWARE FACILITIES

Theoretical studies and simulation design need to be verified through testing,

the same for production and assembling to ensure the product consistency.

Therefore the precise mechanical and electrical test equipment and facilities,

such as far-field or near-field chamber, network analyzer, PIM tester and

environmental reliability testing facilities are required as shown in Figure 3.

Figure 3: Test Environment and Facilities

To ensure products quality during mass production, you need to pay high

attention to margin and tolerance for design and manufacturing procedures,


excellent material quality control mechanism and strict quality and process

control.

MARGIN AND TOLERANCE DEFINITION AND CONTROL The discretion of materials and production during the massive production is

unavoidable. In order to overcome the uncertainties and errors during the

process, antenna suppliers should give certain margin and tolerance for

production during the product design, to ensure the high one time pass rate

and prevent the quality drop due to tuning and maintenance.

Figure 4: Test Environment and Facilities

The antenna is highly integrated product comprising of electrical and

mechanical performance and manufacturing techniques. Besides drawings,

working instruction, etc., it also requires some technical documents to

provide the instruction and guidelines for suppliers, IQC, manufacturing and

materials inspection.

QUALITY MATERIALS—ADVANCED MATERIAL TESTING EQUIPMENT AND

SCIENTIFIC INSPECTION METHOD Incoming material inspection includes conventional and advanced

inspections. Conventional inspection normally uses conventional tools or

visual inspections. The conventional inspection has some limitation.

Sometimes the advanced testing equipment and facilities need to be used to

check the texture, thickness of the materials,

While for in depth inspection it can ensure products’ reliability and durability

with the use of professional testing equipment to inspect the texture,

process and thickness of the plating, etc. Some of the advanced testing

equipment are shown in Figure 5.

Plating Tester Edge Compression Tester Insertion Force Tester

Figure 5: Incoming Material Inspection Equipment


STRICT PROCEDURE QUALITY CONTROL: MULTIPLE QUALITY SUPERVISION

ASPECTS Manufacture process for antenna quality control should be monitored in

steps. Details are shown as below:

Figure 6: Antenna Quality Control Processes

STRICT QUALITY CONTROL PROCEDURE: COMPONENT MANUFACTURING

EQUIPMENT After tuning or repair, the stability of antenna electrical parameters,

especially 3rd order PIM will decrease a lot. From this aspect, antenna is not

repairable. Besides, it is unpractical to implement 100% inspection to all

components. Hence, excellent process and equipment are required to ensure

high quality and consistency of the key components during mass production.


ASSURANCE OF ANTENNA PERFORMANCE

TESTING Antenna performance is verified through relevant testing, which includes

electrical parameters, radiating parameters and reliability testing. Radiation

parameter testing has very high requirement for the testing facility and

needs to get special attention. . There are three ways to conduct radiation

parameter testing: far-field, compact range and near-field testing.

Theoretically, all three methods can perform correct and accurate testing. In

fact, due to hardware, testing system and budget constraint, each testing

method has the inhabitant errors, therefore limits the accuracy. Figure 7

shows the comparison among different testing system:

Figure 7: Comparison between Different Test Systems

Therefore, no matter which test system you use, it should have

corresponding technical requirements to ensure accuracy. Details are shown

as following.


RADIATION PARAMETER TESTING FIELD AND REQUIREMENTS

(FAR-FIELD AND COMPACT RANGE)

Ordinary Test field Precise Test Field

Technical

Requirements Parameters Parameters

Basic Requirements

Far-field test requirements

L > 2(D1^2 + D2^2)/λ

Remark：D1 stands for the dimension of source

antenna, D2 stands for the dimension of antenna

under test. Allows algorithm compensation for the vertical pattern if

the distance is not adequate.

L > 2(D1^2 + D2^2)/λ

Remark：D1 stands for the dimension of source antenna, D2 stands for

the dimension of antenna under test.

Net dimension of

Compact Range

>25m×12m×12m

Shielding requirements of indoor field

>-60dB >-60dB

Caliber field (quiet zone)

requirements

Dimension of quiet zone

Larger than the dimension of antenna under test.

>3m×3m×3m

Reflection level of the quiet zone

>-41dB >-45dB

Magnetic conicity

<0.5dB <0.3dB

Amplitude fluctuation

<±0.25dB <±0.15dB

Level difference between

horizontal and vertical

polarizations

<0.5dB <0.3dB

Radiating performance

testing requirements

Gain testing error range

<±0.5dB； <±0.3dB；

Test stability of gain

<±0.2dB； <±0.1dB；

Pattern testing error

range

-10dB level:<±0.3dB; -15dB level:<±0.7dB; -25dB level:<±2.0dB; -30dB level:<±2.7dB.

-10dB level:<±0.2dB; -15dB level:<±0.4dB; -25dB level:<±1.2dB; -30dB level:<±1.5dB.


RADIATION PARAMETER TESTING FIELD AND EQUIPMENT

REQUIREMENT (128 PROBES SPHERICAL NEAR-FIELD)

Basic requirements

Technical Requirements Parameters

Shielding requirements >-60dB

Dimension of quiet zone Larger than the dimension of antenna under test.

Reflection level of quiet zone >-40dB

Consistency requirements

of probe performance

Amplitude uniformity <±0.15dB

Phase uniformity <±0.2º

Cross polarization >-35dB

Radiation performance

testing requirements

Gain testing error range <±0.5dB；

Test stability of gain <±0.2dB；

Pattern testing error range

-10dB level: <±0.3dB; -15dB level: <±0.711dB; -25dB level: <±2.0dB; -25dB level: <±2.7dB.

REQUIREMENTS OF ELECTRICAL TEST ENVIRONMENT AND

EQUIPMENT

Items Requirements

Shielding requirements

>-60dB

Stability of field VSWR

Choose the antenna under test with VSWR<1.35, the difference of VSWR measured should be within ±0.05 when the antenna consecutively moves according to Tianzi way in a wavelength range around the antenna.

Stability of field PIM

Choose the antenna under test with PIM<-110dBm, do a test for 0.25 wavelength of each move in a wavelength range around the antenna, the difference of 3

rd PIMs should be within 5dB. The test system

connects with standard value of load and the test result complies with specifications.

SUMMARY To summarize, BTS antenna quality is determined by design methodology,

material selection and manufacture process control and so on. The quality of

the antenna has direct impacts on the overall network performance. In

general, in order to produce the high quality antenna, the product life cycle

management system has to be implemented to ensure the quality and

consistency. Also the corresponding software and hardware system and

various testing facilities need to be put into place.


ABOUT COMBA TELECOM Comba Telecom is a leading supplier of infrastructure and wireless

enhancement solutions to mobile operators and enterprises to enhance and

extend their wireless communications networks. With over 50,000 system

deployments around the world including turnkey in-building systems,

urban/rural wireless systems, and transport wireless networks, Comba

Telecom’s end-to-end network solutions include consultation, network

design, optimization and commissioning.

Comba Telecom’s product portfolio includes DAS, small cells, tower mounted

systems, antennas, subsystems, passive accessories, Wi-Fi systems and digital

microwave links.

Listed on the Hong Kong Stock Exchange, Comba Telecom is headquartered

in Hong Kong and has operations throughout the Americas, Europe, Middle

East, Africa and Asia Pacific. To learn more, visit www.comba-telecom.com

and follow Comba Telecom on LinkedIn for regular updates.

www.comba-telecom.com [email protected]

© 2015 Comba Telecom. All rights reserved. Comba Telecom reserves the right to change, modify, transfer, or otherwise revise this

publication and the product specifications without notice. While Comba Telecom uses commercially reasonable efforts to ensure the

accuracy of the specifications contained in this document, Comba Telecom and its affiliated companies will assume no responsibility for

any errors or omissions. Nothing in this publication forms any part of any contract.

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Comba Telecom White Paper - Quality Control Analysis of Base Station Antennas