MetraTec Echo-5P Leitfaden

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
General Information / Security Advice.................................................................................3
1 Notes on the use of this documentation........................................................................3
2 Further Documentation.................................................................................................3
Product Description.............................................................................................................4
1 Intended Use.................................................................................................................4
2 Technical Specification..................................................................................................4
3 Product Drawing............................................................................................................5
4 Accessories....................................................................................................................5
Installation / Integration.......................................................................................................7
1 Distance to Metal..........................................................................................................7
2 Distance to Non-Metallic Materials................................................................................7
3 Note on Cable Routing..................................................................................................7
Maximum Input Power and Antenna Gain...........................................................................9
1 Introduction to formulas and units.................................................................................9
2 Calculations for Echo-5P................................................................................................9
3 Calculations for Echo-8P..............................................................................................10
Further RF Characteristics..................................................................................................11
1 Directional Characteristics...........................................................................................11
2 Antenna Bandwidth.....................................................................................................12
3 Axial Ratio....................................................................................................................12
Version Control..................................................................................................................13
Technical Documentation metraTec Echo-5P/Echo-8P                                       Page 2 of 14

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).

Technical Documentation metraTec Echo-5P/Echo-8P Page 3 of 14

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

Technical Documentation metraTec Echo-5P/Echo-8P Page 4 of 14

2.3 Product Drawing

Technical Documentation metraTec Echo-5P/Echo-8P Page 5 of 14

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.

Technical Documentation metraTec Echo-5P/Echo-8P Page 6 of 14

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.

Technical Documentation metraTec Echo-5P/Echo-8P Page 7 of 14

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.

Technical Documentation metraTec Echo-5P/Echo-8P Page 8 of 14

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

= Maximum output power allowed at the UHF reader in dBm

GI = The antenna gain of a circular antenna in dBic

= 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.

Technical Documentation metraTec Echo-5P/Echo-8P Page 9 of 14

The maximum reader output power

will be calculated for the following example

Maximum ERP

Perp

=27 dBm (since the angular width is > 70°)

Cable loss

=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

for the following example

Maximum ERP

Perp

=33 dBm (since the angular width is < 70°)

Cable loss

=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.

Technical Documentation metraTec Echo-5P/Echo-8P Page 10 of 14

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