application note telink antenna design guidewiki.telink-semi.cn/doc/an/an_16080500-e_telink antenna...

Application Note：

Telink Antenna Design Guide

AN-16080500-E2

Ver 2.0.0

2018/12/17 TE

LIN

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ICO

ND

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Brief：

This document is the design guide for Telink common

antennas.


AN-16080500-E2 1 Ver 2.0.0

Published by Telink Semiconductor

Bldg 3, 1500 Zuchongzhi Rd,

Zhangjiang Hi-Tech Park, Shanghai, China © Telink Semiconductor

All Right Reserved

Legal Disclaimer

Telink Semiconductor reserves the right to make changes without further notice to

any products herein to improve reliability, function or design. Telink Semiconductor

disclaims any and all liability for any errors, inaccuracies or incompleteness contained

herein or in any other disclosure relating to any product.

Telink Semiconductor does not assume any liability arising out of the application or

use of any product or circuit described herein; neither does it convey any license

under its patent rights, nor the rights of others

The products shown herein are not designed for use in medical, life-saving, or

life-sustaining applications. Customers using or selling Telink Semiconductor products

not expressly indicated for use in such applications do so entirely at their own risk

and agree to fully indemnify Telink Semiconductor for any damages arising or

resulting from such use or sale.

Information:

For further information on the technology, product and business term, please

contact Telink Semiconductor Company (www.telink-semi.com).

For sales or technical support, please send email to the address of:

[email protected]

[email protected]

http://www.telink-semi.com/

mailto:[email protected]

mailto:[email protected]


AN-16080500-E2 2 Ver 2.0.0

Revision History

Version Major Changes Date Author

1.0.0 Initial release 2016/8 H.Z.F., L.X., Cynthia

2.0.0

Updated based on

“AN_16080500-E1_Telink Antenna Design

Guide” and “AN_A-PCB-E3_Common

Antennas”.

Added section 1 Overview,

2 Brief Introduction about Antenna,

3 Antenna Type,

4 Matching Bandwidth, RL with a Network

Analyzer.

2018/12 L.X., Cynthia


AN-16080500-E2 3 Ver 2.0.0

Table of contents

1 Overview ................................................................................................................. 5

2 Brief Introduction about Antenna .......................................................................... 5

3 Antenna Type .......................................................................................................... 8

4 Matching Bandwidth, RL with a Network Analyzer ................................................ 9

5 Antenna Simulation Sample 1 .............................................................................. 11

5.1 Module figure ................................................................................................ 11

5.2 S11 figure ....................................................................................................... 11

5.3 Radiation figure .............................................................................................. 12

5.4 Antenna description log ................................................................................. 13


6.1 Module figure ................................................................................................ 14

6.2 S11 figure ....................................................................................................... 14




7.1 Module figure ................................................................................................ 17

7.2 S11 figure ....................................................................................................... 17



8 Small-Dimension Antennas .................................................................................. 20

8.1 Sample 1 ......................................................................................................... 20

8.2 Sample 2 ......................................................................................................... 21


AN-16080500-E2 4 Ver 2.0.0

Table of figures

Figure 1 Typical emission pattern forλ/2 dipole antenna ................................... 5

Figure 2 Mounting cable ...................................................................................... 9

Figure 3 Calibrate vector network analyzer....................................................... 10

Figure 4 Module figure 1 ................................................................................... 11

Figure 5 S11 figure 1 .......................................................................................... 11

Figure 6 Radiation figure 1 ................................................................................ 12

Figure 7 Module figure 2 ................................................................................... 14

Figure 8 S11 figure 2 .......................................................................................... 14

Figure 9 Radiation figure 2 ................................................................................ 15

Figure 10 Module figure 3 ................................................................................ 17

Figure 11 S11 figure 3 ...................................................................................... 17

Figure 12 Radiation figure 3 ............................................................................. 18

Figure 13 Sample 1 ........................................................................................... 20

Figure 14 Sample 2 ........................................................................................... 21


AN-16080500-E2 5 Ver 2.0.0

1 Overview

Antenna is the most important component used in short-range device

applications.

In this document, many important parameters, e.g. bandwidth, gain, impedance

matching parameters, will be introduced.

It is very important to use a correct antenna pattern. In free space, wavelength

(λ) is about 12cm~12.5cm.

2 Brief Introduction about Antenna

Antenna is an important component to transmit higher power and receive a

weak signal.

A typical antenna used in consumer electronics is 1/4 wavelength antenna. And

1/2 wavelength dipole is usually used during initial design.

a) λ/2 dipole antenna

A dipole antenna is often designed asλ/2 wavelength. The Figure 1 shows the

typical emission pattern.

Figure 1 Typical emission pattern forλ/2 dipole antenna

The antenna is located in the Z plane. The most powerful energy is radiated out

in the XY plane. The weakest points are on the Z plane.


AN-16080500-E2 6 Ver 2.0.0

b) Monopole (λ/4) antenna

A monopole antenna is often designed asλ/4 wavelength, and it’s often used in

applications including consumer electronics and IOT.

Since one antenna element isλ/4 wavelength and the GND plane acts as the

otherλ/4 wavelength, theλ/4 wavelength monopole antenna is equal to aλ/2

wavelength dipole antenna in fact.

Usually, a big solid ground is necessary for good antenna performance.

c) Voltage Standing Wave Ratio (VSWR)

In theory, when the source resistance is equal to the load resistance, the load

will get the maximum power from the source.

Z0 = Zl

The complex reflection coefficient(Γ) is defined as below.

Γ = (Zl-Z0)/(Zl+Z0)

If Zl=Z0,Γ=0, then the load gets the maximum energy.

In antenna applications, VSWR and Return Loss (RL) are usually used.

VSWR=(1+|Γ|)/(1-|Γ|)

S11(db)=20log((VSWR-1)/(VSWR+1))

VSWR and RL are used to check how well the antenna works. Usually, VSWR 0f

2.0(RL=9.5dB) is usually used as the limitation to define antenna’s bandwidth. In

real application design, it’s recommended to adopt a pi-matching network.

Table 1 VSWR, RL and Γ

VSWR Return Loss (dB) Reflection Coefficient

1 ∞ 0

1.5 14 0.2

2 9.5 0.333


AN-16080500-E2 7 Ver 2.0.0

d) Antenna parameters

When choosing a correct antenna pattern, it’s needed to consider many

parameters, including:

i. Antenna location: Do not place antenna close to metal components, motor,

battery and so on. Please place antenna face to free space.

ii. Ground plane: A big and solid ground is a fundamental design point to

ensure good antenna performance.

iii. Matching network: A pi-matching network is optional in the design.

iv. Antenna gain: In consumer applications, omnidirectional antenna is a good

choice.

v. Antenna bandwidth: The parameter is defined using Return Loss.

e) Friis transmission equation

Friis transmission equation is a primary formula to estimate power and distance.

When the transmitted power increases by delta (unit: dBm), the communication

distance will be the X multiple.

For example, when increasing power by 6dBm, the communication distance will

double.

△(dBm) X (Multiple)

3 1.4

6 2


AN-16080500-E2 8 Ver 2.0.0

3 Antenna Type

Size and cost are parameters that should be considered together when choosing

antenna.

Table 2 Advantage and disadvantage for different antenna types

Antenna Type Advantage Disadvantage

PCB antenna

low cost;

small size at high frequencies;

wide bandwidth available when

designed well

large size at low frequencies

Chip antenna small size high cost;

narrow bandwidth

Whip antenna high performance high cost;

large volume


AN-16080500-E2 9 Ver 2.0.0

4 Matching Bandwidth, RL with a Network Analyzer

a) Mounting cable for S11 measurement

It is very important to use semi-rigid cables when doing RF measurement.

Solder the outer of the cable to ground plane, and solder the inner of the cable

to the feed point.

Figure 2 Mounting cable

b) Calibration

It is important to calibrate the network analyzer before doing RF measurement.

We usually do it like this.

i. Choose a suitable calibration kit.

ii. Set the correct frequency range.

iii. Set several markers.

iv. Connect three known terminations, 50 ohm load, short and open, to the

connector.

v. Move the calibration plane to the feed point by using calibration

extension function.


AN-16080500-E2 10 Ver 2.0.0

And ferrites MUST be used to reduce the influence from current running at the

outer of the cable. This point is very important, and it’s highly recommended to

follow it.

Figure 3 Calibrate vector network analyzer

c) Antenna under test

The antenna should be placed in the real case when measuring return loss.

For example, if the device is a remote controller, you should measure return loss

with the actual usage case. Since remote controller is handhold, it’s

recommended to take it by your hand when measuring.

d) Impedance matching

Usually Vector network analyzer (VNA) is used to tune an antenna.

Antenna type, ground size, and distance from antenna to ground are the

parameters that can affect the impedance. By changing them, it is possible to

improve the impedance.

Discreet components can also be used to tune antenna by smith chart on VNA.


AN-16080500-E2 11 Ver 2.0.0

5 Antenna Simulation Sample 1

5.1 Module figure

Figure 4 shows dimensions of a module board (Dual-layer FR4, board thickness

is 1mm) and combined antenna.

The maximum gain for this antenna is 3dBi or so.

Figure 4 Module figure 1

5.2 S11 figure

Figure 5 shows S11 figure.

Figure 5 S11 figure 1

2.20 2.30 2.40 2.50 2.60 2.70Freq [GHz]

-27.50

-25.00

-22.50

-20.00

-17.50

-15.00

-12.50

-10.00

-7.50

dB

(St(

An

ten

nn

a_

T1

,An

ten

nn

a_

T1

))

HFSSDesign1XY Plot 1 ANSOFT

m1

m2

m3

Curve Info

dB(St(Antennna_T1,Antennna_T1))Setup1 : Sw eep

Name X Y

m1 2.4000 -22.9083

m2 2.4500 -26.3755

m3 2.5000 -21.2613


AN-16080500-E2 12 Ver 2.0.0

5.3 Radiation figure

Figure 6 shows radiation figure.

Figure 6 Radiation figure 1


AN-16080500-E2 13 Ver 2.0.0

5.4 Antenna description log

1. External view drawing

Picture of antenna

2. Antenna Radiation Pattern

ZX plane ZY plane XY plane

Frequency Max Value Average Max Value Average Max Value Average

[MHz] [dBi] [dBi] [dBi] [dBi] [dBi] [dBi]

2400 3.09 1.77 2.84 -2.5 3.12 -3.71

2450 2.95 1.82 2.92 -2.59 3.06 -3.75

2500 3.18 1.71 2.83 -2.42 3.28 -3.55

Radiation Pattern XOZ Radiation Pattern YOZ Radiation Pattern XOY


AN-16080500-E2 14 Ver 2.0.0


6.1 Module figure





6.2 S11 figure



2.20 2.30 2.40 2.50 2.60 2.70Freq [GHz]

-22.50

-20.00

-17.50

-15.00

-12.50

-10.00

-7.50

-5.00

-2.50

0.00

dB

(St(

An

ten

nn

a_

T1

,An

ten

nn

a_

T1

))


m1

m2

m3

Curve Info


Name X Y

m1 2.4000 -10.9265

m2 2.4500 -21.3129

m3 2.5000 -12.4859


AN-16080500-E2 15 Ver 2.0.0





AN-16080500-E2 16 Ver 2.0.0


1. External view drawing:

Picture of antenna

3. Antenna Radiation Pattern




2400 2.18 1.68 2.18 -3.17 1.78 -3.43

2450 2.23 1.77 2.21 -3.18 1.78 -3.46

2500 2.13 1.70 2.13 -3.27 1.58 -3.52



AN-16080500-E2 17 Ver 2.0.0


7.1 Module figure





7.2 S11 figure



2.20 2.30 2.40 2.50 2.60 2.70Freq [GHz]

-22.00

-20.00

-18.00

-16.00

-14.00

-12.00

-10.00

dB

(St(

An

ten

nn

a_

T1

,An

ten

nn

a_

T1

))


m4

m5

m6

Curve Info


Name X Y

m4 2.4000 -18.6059

m5 2.4400 -19.9247

m6 2.5000 -21.0839


AN-16080500-E2 18 Ver 2.0.0





AN-16080500-E2 19 Ver 2.0.0


1.External view drawing:

Picture of antenna

2.Antenna Radiation Pattern




2400 2.91 2.09 2.93 -3.00 2.67 -4.14

2450 2.83 2.13 2.78 -3.12 2.81 -4.13

2500 2.95 2.07 2.87 -3.00 2.89 -4.05


0.60

1.20

1.80

2.40

90

60

30

0

-30

-60

-90

-120

-150

-180

150

120

HFSSDesign1XOZ ANSOFT

Curve Info max avg

Freq='2.45GHz' Phi='0deg' 2.9088 2.0909

Freq='2.4GHz' Phi='0deg' 2.8336 2.1312

Freq='2.5GHz' Phi='0deg' 2.9462 2.0705

-11.00

-7.00

-3.00

1.00

90

60

30

0

-30

-60

-90

-120

-150

-180

150

120

HFSSDesign1YOZ ANSOFT

Curve Info max avg

Freq='2.45GHz' Phi='90deg' 2.9354 -3.0085

Freq='2.4GHz' Phi='90deg' 2.7809 -3.1230

Freq='2.5GHz' Phi='90deg' 2.8668 -2.9999

-19.00

-13.00

-7.00

-1.00

90

60

30

0

-30

-60

-90

-120

-150

-180

150

120

HFSSDesign1XOY ANSOFT

Curve Info max avg

Freq='2.45GHz' Theta='90deg' 2.6711 -4.1401




AN-16080500-E2 20 Ver 2.0.0

8 Small-Dimension Antennas

The two types of antennas shown in this section apply to applications with

requirement for highly limited board size (e.g. dongle and module). In actual

applications, as long as board size allows, it’s recommended to adopt antenna with

larger area for better performance.

8.1 Sample 1

Figure 13 Sample 1


AN-16080500-E2 21 Ver 2.0.0

8.2 Sample 2

Figure 14 Sample 2

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