metraTec Echo-5P Guide

Technical Documentation and
Integrations-Guide
for metraTec Echo-5P and Echo-8P UHF Patch Antennas
Release July 2017
Version 1.4
Technical Documentation metraTec Echo-5P/Echo-8P Page 1 of 14

Table of Contents
1 General Information / Security Advice.................................................................................3
1.1 Notes on the use of this documentation........................................................................3
1.2 Further Documentation.................................................................................................3
2 Product Description.............................................................................................................4
2.1 Intended Use.................................................................................................................4
2.2 Technical Specification..................................................................................................4
2.3 Product Drawing............................................................................................................5
2.4 Accessories....................................................................................................................5
3 Installation / Integration.......................................................................................................7
3.1 Distance to Metal..........................................................................................................7
3.2 Distance to Non-Metallic Materials................................................................................7
3.3 Note on Cable Routing..................................................................................................7
4 Maximum Input Power and Antenna Gain...........................................................................9
4.1 Introduction to formulas and units.................................................................................9
4.2 Calculations for Echo-5P................................................................................................9
4.3 Calculations for Echo-8P..............................................................................................10
5 Further RF Characteristics..................................................................................................11
5.1 Directional Characteristics...........................................................................................11
5.2 Antenna Bandwidth.....................................................................................................12
5.3 Axial Ratio....................................................................................................................12
6 Version Control..................................................................................................................13
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1 General Information / Security Advice
1.1 Notes on the use of this documentation
This user manual and integration guide uses different symbols to point out potentially
dangerous situations. The following signs and symbols are used throughout the document.
ATTENTION
Declares a potentially hazardous situation. If this is not avoided, the product
or something in its surrounding could be damaged.
NOTE
Declares notes for the user as well as other useful information, where no
harmful or dangerous situations can be expected.
1.2 Further Documentation
This documentation refers at different points to the EN ETSI 302 208-1 where important
parameters and limits for the use of UHF RFID systems in the territory of the European
Union are defined. The system integrator (the person or company who combines this
product with other devices, e.g. UHF readers) is responsible for the compliance with these
limits. The document is available for free at the website of the ETSI (www.etsi.org).
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2 Product Description
The metraTec Echo-5P and Echo-8P are circularly polarized UHF RFID antennas for the
European UHF RFID frequency range around 868 MHz. The housing is made from POM
(polyoxymethylene) which has excellent mechanical properties and is resistant to many
chemicals. Common applications are for UHF RFID Gates (especially Echo-8P with narrow
angular width and a gain of 8 dBic), as well as in systems with limited available space, e.g.
forklifts underneath for scanning tags on the floor or inside the fork lift's mast.
2.1 Intended Use
The Echo-5P and Echo-8P are UHF patch antennas developed for the use in UHF RFID
systems using the European frequency range (around 868 MHz). All technical specifications
in this document are given with this intended use in mind. The performance of this product
for any other use cannot be guaranteed by metraTec.
2.2 Technical Specification
Operating Principle Circular polarized UHF patch antenna
Resonance Frequency 865 MHz (UHF RFID, ETSI)
Impedance Bandwidth (-10 dB) 858 – 877 MHz
Polarization RHCP ( right-handed circular polarized)
3dB Angular Width Echo-5P 100°
Echo-8P 62°
Antenna Gain Echo-5P 5 dBic
Echo-8P 8 dBic
Nominal Impedance 50 Ohm
Axial Ratio < 3 dB
Max. RF power permitted
(acc. to EN ETSI 302 208-1)
Echo-5P 500mW ERP (see Ch. 4)
Echo-8P 2W ERP (see Ch. 4)
Operating Temperature -40°C to +85°C
Dimensions Echo-5P 90 x 105 x 30 mm (without R-TNC connector)
Echo-8P 90 x 300 x 20 mm (without SMA connector)
Antenna Connector Echo-5P R-TNC, male
Echo-8P SMA, female, gold plated
Protection (IP-Code) IP 40
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2.3 Product Drawing
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Fig. 1: Drawing of Echo-5P (all dimensions in mm)
Fig. 2: Drawing of Echo-8P (all dimensions in mm)

2.4 Accessories
Besides the Echo-5P and Echo-8P antennas metraTec offers all the necessary accessories,
e.g. coaxial cables with R-TMC/SMA connector on the one side and (almost) any other
antenna connector on the other side. For this we can use standard coaxial cables or special
low loss coaxial cable with a loss of only 0,3 dB/meter (for applications with cable length up
to 15 m without problems). Depending on your requirements we can also build high
temperature cables, cables with protection against certain chemicals, etc.
Another accessory we offer is the wall mounting bracket for increased flexibility in adjusting
antenna alignment using a ball joint.
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3 Installation / Integration
3.1 Distance to Metal
To ensure the full performance of the antenna certain minimal distances between the
antenna and all metal parts should be observed. Our recommendations are
Keep bigger metal parts at least 6cm away from the sides of the antenna.
Don't place any metal parts in front or to the side of the patch antenna in the main
lobe (see radiation pattern, section 5.1).
Installing the antenna on a bigger metal plane should be avoided since all antenna
parameters can shift extremely in this case. It is no longer certain that all regulations
are fulfilled and a new measurement would be necessary in this case, requiring
special knowledge as well as appropriate equipment, i.e. at least a spectrum
analyzer. You can avoid this by using a mounting kit that ensures a minimum
distance of 6 cm between antenna and metal plane. We would like to recommend
the optional available wall mounting bracket for this purpose, as mentioned in
2.4(Accessories).
3.2 Distance to Non-Metallic Materials
Also non-metallic materials can influence the performance of the antenna in a negative way.
Especially mounting the antenna close to containers with fluids (even if they are made from
plastics) as well as near human bodies (e.g. if used for wearable computing applications) will
influence the circular polarization of the antenna (ref. to 5.3"Axial Ratio"). The read
performance for tags which lie in the affected polarization will decrease significantly. In
extreme cases the antenna can be de-tuned in such a way that it is no longer able to radiate
in the RFID frequency band (ref. to 5.2"Antenna Bandwidth").
3.3 Note on Cable Routing
Besides minimal distance to objects near the antenna, also the cable routing can have a big
influence on the performance. Following the next few tips will give you the best
performance
Lay the cable straight to the bottom of the patch or to the back (using a 90°
connector).
Do not lay the cable around the sides of the antenna.
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Do not lay the cable in front of the antenna, directly in the radiation field.
Keep cables as short as possible and use low loss cables for best performance. If
needed, these can be purchased from metraTec.
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4 Maximum Input Power and Antenna Gain
Antennas in connection with RFID systems for use in the European Union are covered by the
R&TTE Directive (Radio and Telecommunications Terminal Equipment Directive;
1999/05/EG). This means that numerous norms regarding maximum output power of such a
system have to be considered. For UHF RFID systems this is mainly the EN ETSI 302 208-1.
Depending on the type of antenna the following power limits are allowed
For systems with antennas with an angular width of more than 70° (e.g. the Echo-5P)
an effective radiated power (ERP) of 500mW (27 dBm) is allowed.
For systems with antennas with an angular width below 70° (e.g. the Echo-8P) an
effective radiated power (ERP) of 2W (33 dBm) is allowed.
The corresponding reader output power to the maximum values of 500mW resp. 2W ERP
depends on the losses of the cables as well as the antenna gain (being a measure for the
concentration of the energy). The next section shows an example for such a calculation.
4.1 Introduction to formulas and units
The antenna gain of a circular antenna is measured in dBic. This values describes the
capability of the antenna to concentrate the radiated power in the main coil compared to an
isotropic radiator. It combines the radiated power of both polarizations. The antenna gain of
a single polarization (given in dBi) is 3dB lower. Antenna gain of a single dipole (given in
dBd) is 2.15 dB lower.
The maximum power allowed for a UHF reader is calculated with the following formula
Pc=Perp−GIC+5.15+CL
Where the symbols mean
Pc
= Maximum output power allowed at the UHF reader in dBm
GI = The antenna gain of a circular antenna in dBic
CL
= Cable loss in dB
Perp
= max. allowed ERP according to the ETSI 302 208-1 in dBm, being 27 dBm
(500mW) for the Echo-5P and 33 dBm (2W) for the Echo-8P
4.2 Calculations for Echo-5P
The Echo-5P has an antenna gain of approx. 5dBic.
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The maximum reader output power
Pc
will be calculated for the following example
Maximum ERP
Perp
=27 dBm (since the angular width is > 70°)
Cable loss
CL
=0,3 dB (1m cable with low loss cable)
This leads to
Pc=27 dBm−5dBic +5.15+0.3=27.35 dBm=540 mW
Mobile UHF readers with a typical maximum output power of 500mW may be operated with
the Echo-5P. Fixed readers with typically more than 500mW have to be limited to 540 mW.
4.3 Calculations for Echo-8P
The Echo-8P has an antenna gain of approx. 8dBic.
We will calculate the maximum reader output power
Pc
for the following example
Maximum ERP
Perp
=33 dBm (since the angular width is < 70°)
Cable loss
CL
=1,5 dB (5m cable with low loss cable)
This leads to
Pc=33 dBm−8dBic+5.15+1.5=31.65 dBm=1460 mW
Thus, fixed UHF reader with a typical output power of 2W have to be limited already (this
holds for every UHF antenna with 8dBic or more!)
You can see that antenna with a very high gain (e.g. 10 dBic) do not have a real advantage
when used in the EU since the power of the reader has to be limited in every case so that
the maximum read distance stays the same. Only the beam becomes narrower which makes
it harder to “target” transponders.
The Echo-8P has an optimized radiation pattern for both polarizations (horizontally narrow,
vertically wide).
NOTE
The Echo-8P has to be installed horizontally when it is used with more than
540mW output power.
The Echo-5P can be mounted in any orientation or be used in a mobile
application, since the output power of the reader should always stay below
540 mW.
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5 Further RF Characteristics
5.1 Directional Characteristics
The radiation pattern/directional characteristics of the Echo-5P is identical for both
polarizations and is shown in Fig. 3. The radiation pattern also shows the radiation of the
Echo-8P in the vertical polarization. Fig. 4 shows the radiation of the Echo-8P in the
horizontal polarization.
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Fig. 3: Directional characteristics of the Echo-5P (both polarizations) and Echo-8P,
vertically
Fig. 4: Directional characteristics of the Echo-8P, horizontally

5.2 Antenna Bandwidth
Figure 5 shows the input impedance of the antenna at the operating frequency of 868 MHz
including antenna bandwidth at 10 dB. The minimum of the reflexion is at 865 MHz (-28 dB).
The 10dB-bandwidth is 12 MHz (858 MHz to 877 MHz).
5.3 Axial Ratio
The axial ratio is the ratio of the radiated power of the two polarization planes. A circular
antenna should distribute the power of the reader evenly between both planes to read RFID
transponders at any polarization.
The axial ratio of the Echo-5P and Echo-8P is typically 1-2 dB.
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Fig. 5: Input impedance of the antenna around 868 MHz

6 Version Control
Version hange edited by Date
1.0 created KD 10.09.09
1.1 minor edits CS 09.07.14
1.2 update antenna dimensions, minor
corrections, layout
CS 07.10.14
1.3 update address and image KS 07.12.16
1.4 update technical sketch Echo-5P,
update technical specifications Echo-5P
KS 06.07.17
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Contact
metraTec GmbH
Niels-Bohr-Str. 5
39106 Magdeburg, Germany
Tel. [phone]
Fax [phone]
Email [email protected]
Web http //www.metratec.com
Copyright
© 2017 metraTec GmbH
Reprint or reproduction of this documentation for other than internal purposes is only allowed with
written permission by metraTec GmbH.
All trademarks are the property of their respective owners.
All right reserved.
We are constantly improving our products. Changes in function, form, features can happen without
prior notice.
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