Application Note AN008: RF Receiver Sensitivity
Contents
1. APPLICATION NOTE 008 Green Smart Wireless enocean 1 Introduction Radio frequency RF test equipment is often prohibitively expensive and test engineers may not have RF expertise available to them This leads to a lack of verification of the RF performance in a device As a result devices end up exhibiting poor range characteristics that are not circumvent able as the issue lies in the underlying design EnOcean has devel oped software tools that will allow you to validate the receiver performance with limited RF engineering support while utilizing on hand hardware 1 1 Table of contents L INNOCUO serae a E a a e E A E a 1 LL IIS OL CON ON aesa E mas ogeususecseaceuees 1 1 2 ROIOrONCOG 32a acenctenaacccd a aten aa a a aaa aaa a a aa anai 2 1 3 PUDO SO EEEE EO EE EEE E E EEEE EEEE 2 LI TENNO a T A E E 2 1 5 TOCO arrenar na a E A A A E T EEA 3 2 POS eUD a a r E E 4 2 1 Required materials sssssusssnnssnsnsnnsnrnnsnsnnenrnnennnnesnnnennsnennsnrnnenrnnenrnnennrnennnnenn 5 2 2 Hardware SCEUD reriririresinisironirinininini rinni ra nininini An DARDA TAE AOA AEA 5 2 2 1 RF iSolated Gale Way js auirciradasecatadntpeitaamorsacnegesabmaadaimpesreoatecmaaneniiabmtaces 5 2 22 Etema an ENN a ke ee ee ee ee ee nee ee ee ee ee ee ee 6 2 2 3 DEVICE Under to treaa A a a E R E A 6 2 2 4 ENOC O nNENAY ee E E A EE 7 2 3 Pini Wale SelUD cue tenccanee cranes teen acan cc cu acan aa a a a E a a a a Oa 7 2 3 1 RF Shielded Gatewa c2. RX Sensitivity dBm 98 96 98 Table 2 EnOcean modules RX sensitivities In order to include all noise sources at the receiver within the filtered bandwidth we meas ure the noise floor at the receiver This output is available as the long term signal strength indicator and should be similar to the values in Table 2 in an isolated RF environment 2 Test Setup The test setup consists of three EnOcean modules the DUT which measures receive power from the TX gateway and transmits this information back to the rx gateway device The RF shielded gateway device sends radio telegrams in conjunction with Dolphin View Advanced operating on a connected computer A second EnOcean gateway will be used to receive telegrams from the DUT also with Dolphin View This can be any EnOcean device that can utilize the onboard serial port All devices require the correct firmware to be programmed on them Initially the DUT will respond to all EnOcean telegrams with signal strength information To filter out devices besides the TX gateway device the remote management action command must be sent to the DUT from the TX gateway The DUT will then respond by transmitting the RSSI information of the TX gateway when it receives a trigger telegram Shielded TX Gateway ips l Trigger Telegram i I nnnnnnnnnnnnnnnnnnnnnnnnnnnnn l ESP3 i Serial Link E ares sicibig Saw ewe ses Kew eemeneew VLD Debug Telegram B Figure 1 Simplified
3. be removed Please see section 4 3 2 of the TCM 320 user manual Mounting 502 antennas for more details on this step as it varies with frequency APPLICATION NOTE 008 Green Smart Wireless ocean RF RECEVER SENSITIVITY PREFORMING VALIDATION 00000000 geceocoess Tt t 4 54 000000000000 Figure 2 Example Gateway device in RF shielded enclosure with external antenna connector 2 2 2 External antenna The RF isolated gateway should not be located near the DUT to reduce any emissions that escape the RF isolation box All RF connectors need to be securely connected placing the antenna approximately 100cm from the DUT As always spacing guidelines between any antenna and metal planes should be observed The antenna should be easy to disconnect in order to adjust the attenuation on the output signal Figure 3 External Antenna and DUT 2 2 3 Device under test The DUT should be orientated as it would be once installed It should be operating from the on board power supply and any other peripheral hardware if possible Placement should be at least 1m from potential external sources of interference including power supplies for oth EnOcean www enocean com Subject to modifications Bryan Edelman January 2013 Page 6 14 APPLICATION NOTE 008 Green Smart Wireless enocean er devices lighting drivers electromechanical devices and lighting fixtures unless this is the operating environment of t
4. connect button after the Dolphin Snif fer firmware has been programmed into the TX gateway The same applies for the RX gateway APPLICATION NOTE 008 Green Smart Wireless enocean 2 5 Test procedure 2 5 1 RX_Sensitivity_Test overview The RX_Sensitivity_Test firmware was developed by EnOcean to enable the receive power of radio telegrams to be measured without using RF tools During start up the DUT running the RX_Sensitivity_Test firmware will transmit a single SYS radio packet RORG equal to OxA4 with the four data bytes being 0x00 This allows you to determine the ID of the DUT and filter out other EnOcean devices in Dolphin View Advanced Once running for every radio telegram that is received the DUT will respond with a VLD debug telegram that contains the sender ID status RSSI long term RSSI level one re peated RSSI and level two repeated RSSI of the previously received telegram This data can be visualized using the EEP D2 3F DE from the debug xml profile file in the Dolphin View Advanced EEP tab Description Size Bytes Offset Bytes RX Telegram RORG 1 RX Telegram Sender ID RX Telegram Status RX Telegram RSSI RX Telegram Sub Telegrams Received DUT Long Term RSSI to Figure 4 VLD Debug Telegram Format To focus the RSSI debug telegrams trigger only on our RF isolated gateway messages a filter can be established via the remote management action command 2 Whenever the DUT receives
5. 85 telegram Send Radio RORG 1BS Data BE ijala wo Status OF DestinationlD FFFFFFFF Securitylevel 0 Set ID Jump to label Repeat Figure 10 Transmitting 1BS Trigger Telegrams 6 Start sending trigger telegrams by clicking the Execute All button Move to the EEP view of the receiving gateway Now you should see steady signal strength a con stant telegram count of 3 and the long term RSSI value APPLICATION NOTE 008 Green Smart Wireless enoceal Data Telegram Interpretation 127 5 200 30 20 15 50 30 13 50 40 15 50 30 15 51 00 13 51 10 a Subtelegram Count 3 00 9 4 5 0 70 20 15 50 30 13 30 40 15 50 50 15 51 00 13 51 10 4 Long term RSSI 89 00 dBm g 127 3 2292 50 20 15 50 30 15 50 40 15 50 50 15 51 00 15 51 10 Figure 11 Operation with no attenuation all sub telegrams received 7 In order to discover the lowest RX power that the DUT can properly decode we will lower the power the DUT receives with the use of attenuators until sub telegrams are lost occasionally In this case we would expect to be able to add in 43dB of at tenuation Continue to adjust the RX signal strength via attenuators until you begin to lose sub telegrams This can be considered the RX sensitivity level of the DUT This should be equal to or better than the LTRSSI value APPLICATION NOTE 008 Green Smart Wireless enocean Data Telegram Interpretation allSignal
6. RECEVER SENSITIVITY PREFORMING VALIDATION LTRSSI Long term RSSI a measurement to determine the ambient power levels of the frequency used in the DUT Trigger Telegrams 1BS telegrams with OxBE as the data byte These trigger the DUT to transmit RSSI VLD debug telegrams Transmit Gateway RF isolated gateway that will be sending trigger telegrams to the DUT via Dolphin View Advanced Receive Gateway Gateway that will be receiving VLD debug telegrams from the DUT via Dolphin View Advanced 1 5 Theory In order for an RF signal to be received it needs to be detected and then decoded By measuring ambient wireless power levels the receiver can detect the beginning of transmis sion when the input power level increases across a threshold During times when no transmissions are occurring this power level is known as the noise floor or long term re ceive signal strength value It represents the power received from emitters other than the intended transmitter If the power at the receiver has a sudden increase for a sustained time the receiver can attempt to decode this as a valid signal The successful decoding of a radio telegram de pends on the ratio of the power of the signal to the power of the noise SNR at the receiv er during reception If the SNR is large the noise will have little influence on the probability of correct bit detection If there is a significant noise level relative to the signal and thus a small SNR the prob
7. Test Setup Operating Mode For 0 1 telegram loss with three transmitted sub telegrams APPLICATION NOTE 008 Green Smart Wireless enocean 2 1 Required materials 1 2 3 4 5 6 7 8 9 The device under test A TCM320 with external SMA antenna connector shielded gateway A TCM3xx with Serial output or USB300 gateway An external antenna Dolphin View Advanced RF isolation box or Faraday cage EVA300 development board or similar hardware EOPX programmer board including cables Dolphin Sniffer Firmware Via Dolphin View Advanced 10 RX_Sensitivity_Test Firmware hex and _cfg hex 11 RF attenuators designed for the test frequency 2 2 Hardware setup 2 2 1 RF isolated gateway The TCM320 gateway and supporting hardware should be placed in an RF isolation box un grounded floating metal box or faraday cage to reduce RF leakage from PCB traces and RF connectors Otherwise spurious RF signals can leak out and change the power levels the receiver measures With the transmitter in RF isolation all the receive power is transmitted from the external antenna where the power output will be controlled The transmitter also needs to be connected to a PC to interact with Dolphin View Advanced This can be accom plished with the EnOcean programming board EOPX or a custom solution To enable the external antenna on the TCM320 its circuitry may need to be adjusted and the existing antenna needs to
8. ability of decoding bits correctly decreases To maximize the power re ceived good RF layout and antenna design practices should be followed Limiting the noise is more complicated Without noise a receiver could correctly decode a signal that arrives at the tiniest power level and wireless signals could be received at very long distances Many noise sources ex ist at the lowest level of physics and cannot be mitigated The most significant noise source is thermal noise because it is constant over time and exists at every frequency This noise s power level is a function of the devices temperature and the bandwidth of the receivers input The equation for noise power generated from thermal noise is below P kgTB kg 1 3807 107 T 298 15 K 25 C B 300kHz EnOcean Dolphin ASIC Freq 315MHz 868MHz 902MHz P dBm 119 1 119 1 119 1 Table 1 Noise Floors An EnOcean receiver with no other noise sources can receive radio telegrams that have power above the values in Table 1 However other significant signal quality reducers do exist amplifiers and filters introduce noise and attenuation while decoders require a mini mum power above the noise floor This allows us to arrive at the operating noise floor of EnOcean receivers EnOcean www enocean com Subject to modifications Bryan Edelman January 2013 Page 3 14 APPLICATION NOTE 008 Green Smart Wireless enocean Freq 315MHz 868MHz 902MHz
9. cccccccccccccecccccccccceccceseeeeeeeeaeeeeeeeeeeeeeeeaeauaaeaanaanaaags 7 2 332 D vice under toS eee ene nee E ere ere ere 7 2 3 3 BNOCEAN Gateway arcceaciatisentacsaceracatscsedinsecenceadigensentatwiesesaeenseatacansiadenensene 7 2 4 SOP ae SetU acumen ecco ewiewentu een a a a aa a a a a a a 7 2 5 Test procedure jcnsacatinceacnnnencasadiadeadenavordaatiadeaeaiaserdaatandeiaanaveeiaatiadeiaaiaseriaatiaant 8 2 5 1 RX_Sensitivity_Test overvieW s sssesessssssssssrrrrsnsnrnrnenensrnrnrnrnrnrnrnrnrrererune 8 2 5 2 PROCCQUI stance ccteccncecececsccotencnseceencsaestoncsieceeecscestencsiecececnsesteccsieceeecsiestencs 9 2 5 3 Alternative Procedure ccccccccccee eee enn nee e ee eeeee seen eee e nana nee saaeeeeeeeeneettnngs 13 2 5 4 COMCIUSIOINS ea dacs taeda sentaen tees tnettaeatacn teen taettaeatacniocntas 13 APPLICATION NOTE 008 Green Smart Wireless enocean 1 2 References Familiarity with the following will be useful for this test procedure 1 EnOcean Equipment Profiles EEP v2 5 2 Remote Management Specification v1 7 3 EnOcean Radio Protocol v1 0 4 TCM 3xx User Manual 5 Dolphin Studio Help Guide 6 Dolphin View Advanced Help Guide 7 AN602 USB Based EnOcean Transceiver Easy Realization of an EnOcean PC Gateway PDF 12 2010 Useful web sites 8 EnOcean website http www enocean com 9 EnOcean Alliance website http www enocean alliance org 10 MiniCircuits website h
10. ess enocean Two possible reasons that the measured RX sensitivity will not match the specification are that other devices are transmitting at the test frequency and the DUT is emitting uninten tional noise at the test frequency via onboard devices such as switching power supplies PWM drivers or other periodic signals Both of these are capable of corrupting RF telegrams as they are received at the antenna of a device The external RF environment can be qualified without additional RF test tools by using a known reference This can be accomplished by loading the RX_Sensitivity_Test firmware onto a TCM3xx module in combination with an EnOcean development board such as the EDK 300 and using this as a reference level If the measured RX sensitivity is not equal to or less than the LTRSSI value then the environment is not acceptable for testing Move the test setup to a different physical location where devices transmitting at the test frequency will have less impact on the DUT If in a low external noise environment the RX sensitivity fails to reach the LTRSSI then the device itself is generating interference and should be evaluated for unwanted emissions from internal components and the RF design should be validated This may require the use of a spectrum analyzer Please contact EnOcean for additional assistance if required The operating range of any wireless devices depends on the link budget It is important to remember that this is
11. he DUT 2 2 4 EnOcean gateway This device should be placed within RF range of the DUT Access to the serial lines are re quired in order to communicate with Dolphin View Advanced across ESP3 It is recom mended to use a TCM3xx and the EDK development board Alternatively please see AN602 USB Based EnOcean Transceiver Easy Realization of an EnOcean PC Gateway PDF 12 2010 2 3 Firmware setup 2 3 1 RF shielded gateway The gateway needs to be running the Dolphin Sniffer firmware This can be programmed into the TCM320 via the Dolphin View Advanced Firmware Download button once the cor rect COM port is selected in the dropdown menu Disconnect F6 enocean sis Telegram Analyzer 7 Remote Management Node Statistics 1 l L 2 3 2 Device under test The DUT needs to be running the RX_Sensitivity_Test firmware that is provided by EnO cean This can be programmed onto the TCM3xx using Dolphin Studio and your program ming hardware interface 2 3 3 EnOcean Gateway This TCM3xx needs to be running the Dolphin Sniffer Firmware Alternatively this can be a USB300 This needs to be connected to a separate instance of Dolphin View Advanced but can be running on the same computer as the RF isolated gateways instance of Dolphin View Advanced 2 4 Software setup Dolphin View Advanced will be used to send and receive radio telegrams from the gateway device Select the appropriate com port and click the
12. influenced by both the ability to receive low level signals as dis cussed in this application note and the ability to transmit efficiently Please see AN102 Antenna Basics Basic Antenna Design Considerations for EnOcean based Products and AN105 315 MHz internal antenna design Considerations for EnOcean based Products PDF 12 2011
13. om me pom an ae cm nn to me tm mets pam mene om mies nn ee pan cen pn meno etme pam weg pan pag an en rn cen pn men po gm pam pom an gon an m e a nen mp pee tm pags pom een on men pn men pon en pon enon toa 1 Device Power on roo yom x TX SY8 0 0 0 0 j Dolphi oa pur to ma Any lhe eee C EnOcean y 9 View 4 TX ReMan Action l Device 5 TX SYS Filter ID QW 6 TX 1BS 0xBE oo l E 401X VLD Debug 7 RX_Sensitivity_ Debug Repeat Operation Figure 5 Example Operation of RX_Sensitivity_Debug Firmware 2 5 2 Procedure 1 Follow the steps outlined in section 2 Test Setup 2 Locate your DUT in the Dolphin View workspace and apply the RX Debug EEP located in the debug xml profile file on the instance connected to the EnOcean gateway E Export Profs ETT a EnOcean Equipment Profile RORG oxD2 VLD Telegram a af The FFASSIRC Figure 6 Add the Debug EEP Profile APPLICATION NOTE 008 Green Smart Wireless enocean Data Telegram Interpretation Signal strength 81 00 dBm 11 06 00 11 06 10 11 06 20 11 06 30 11 06 40 a Subtelegram Count 6 00 9 4 5 g 11 06 00 11 06 10 11 06 20 11 06 30 11 06 40 C Long term RSSI 89 00 dBm a Figure 7 EEP Debug Profile 3 To eliminate the VLD debug telegrams coming from other sources we need the DUT to filter on the RF isolated gateway In the remote management wind
14. ow of the Dol phin View connected to the TX gateway click the action button CW 3 Jae Ul EEP View Taearam Aazer Remote Management Device security cate ta we mre Target G All devices CID 0100D2D6 b Je Figure 8 ReMan Action Command To confirm receiving this action telegram the DUT will reply with a SYS telegram containing the ID of the device it is now filtering on Confirm it is the TX gateways ID You will also no longer be receiving VLD debug telegrams from other EnOcean devices that are transmitting within range upon a successful filter is added in the DUT APPLICATION NOTE 008 Green Smart Wireless enocean 14 48 52 122 0100D2D6 5 00 00 00 00 14 48 54 745 0100D2D6 t 00 84 26 FB Figure 9 Start up and successful filter telegram from a DUT 4 To trigger the VLD RSSI telegrams we need to send 1BS telegrams with OxBE as the data We can utilize Dolphin View s Telegram Transmit to do this On the Telegram Transmit tab on the Dolphin View associated with the RF isolated gateway go to file then load Select RX_Sensitivity_Trigger do This file contains a loop that will auto matically send a trigger telegram once per second Please note that the least signifi cant nibble of the status byte must be OxF to indicate that the telegram should not be repeated by any repeaters 5 nna o a p J SS SS ee Label Repeat Delay 1000 millisecond Comment Send 1
15. strength 91 00 dBm 127 2 239 j 16 17 50 16 18 00 16 18 10 16 18 20 16 18 30 1 a Subtelegram Count 1 00 9 a EE EE x j 16 17 30 16 18 00 16 18 10 16 18 20 16 18 30 1 a Long term RSS 89 00 dBm j 16 17 50 16 18 00 16 18 10 16 18 20 16 18 30 1 Figure 12 Operation at RX Sensitivity level 2 5 3 Alternative Procedure The above procedure can be conducted with a USB gateway running the Dolphin Sniffer Software in place of a TCM320 external antenna and RF attenuators RF power levels re ceived at the DUT can be adjusted by physically moving the USB gateway and increasing distance between the devices instead of using RF attenuators Trial and error will be re quired to find an optimal position that sets the DUT RX power near the RX sensitivity level Please note that this does not qualify the maximum range and only the RX sensitivity level In order to analyze the VLD debug telegrams the receiving gateway should be running ona stationary computer within RF range of the DUT which may require a second person to aid in the completion of this application note 2 5 4 Conclusions Each Dolphin Module has its RX sensitivity specified in Table 2 EnOcean modules RX sen sitivities Ideally telegrams should properly be received down to this power level If the DUT s RX sensitivity is equal or less than the LTRSSI value the DUT RF receiver portion can be considered successful APPLICATION NOTE 008 Green Smart Wirel
16. this action command the DUT will respond with RSSI debug telegrams only if a telegram comes from this sender ID To confirm a successful filter addition the DUT will transmit a SYS telegram with the now filtered ID as the four data bytes Note that the de vice will only accept the action command for 30 minutes After this time the device will ig nore all remote management commands as defined in the remote management standard Power cycling the device will restart this 30 minute timer APPLICATION NOTE 008 Green Smart Wireless enocean Once filtering is established in order to trigger a RSSI debug telegram the DUT must re ceive a 1BS telegram from the filtered sender ID with its data byte equal to OxBE Once the device is reset or powered off the filter is removed Any time the remote management action command is received the DUT will start to filter on the most recent sender s ID In your test environment please ensure these remote management action commands are not being sent during testing In order to remove repeaters from the test environment which will affect RSSI values all transmitted telegrams will have the least significant nibble set to OxF This indicates that the telegram shall not be repeated Please see 4 2 3 of the EnOcean Radio Protocol for more information on repeaters gerem eem ee mee mee m e mea rem en om mea pn cen nome pa mpm eam mines pom es ae me pen ce nee nem ne pam mean ee man en en men pep na m
17. ttp www minicircuits com 1 3 Purpose The test procedure in this application note can be used to verify the sensitivity of an EnOcean wireless receiver that is designed into a finished good The receive sensitivity RX sensitivity is an important radio parameter as it establishes the minimum power that re ceived signals can be decoded correctly The RX sensitivity is affected by a number of things including consistency of the power supply effectiveness of RF filters and the amount of self generated in band EMF emissions Qualifying the RX sensitivity is useful for determining the ability of the DUT to receive wireless signals ultimately becoming a pa rameter in the link budget and determining the maximum operating distance between two devices This level can also be compared to the RX sensitivities of the individual EnOcean modules to evaluate how successful the end design is 1 4 Terminology DUT Device under test a finished EnOcean based product that will be tested for its re ceive sensitivity 1BS One byte sensor an EnOcean telegram type VLD Variable length data an EnOcean telegram type Gateway EnOcean based hardware that translates EnOcean telegrams to ESP3 ESP3 EnOcean Serial Protocol 3 the latest version of EnOcean s serial protocol RSSI Receive signal strength indicator a measurement to determine the power of a re ceived signal APPLICATION NOTE 008 Green Smart Wireless enocean RF
Download Pdf Manuals
Related Search