Embedded Meets RF Evan Lojewski. RF Primer Terminology / Intro RF Options Certification.
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Transcript of Embedded Meets RF Evan Lojewski. RF Primer Terminology / Intro RF Options Certification.
![Page 1: Embedded Meets RF Evan Lojewski. RF Primer Terminology / Intro RF Options Certification.](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649d1a5503460f949ef367/html5/thumbnails/1.jpg)
Embedded Meets RF
Evan Lojewski
![Page 2: Embedded Meets RF Evan Lojewski. RF Primer Terminology / Intro RF Options Certification.](https://reader035.fdocuments.in/reader035/viewer/2022062300/56649d1a5503460f949ef367/html5/thumbnails/2.jpg)
RF Primer
•Terminology / Intro
•RF Options
•Certification
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Terminology
•Decibel - logarithmic scale
•Channel - subdivided portion of spectrum
•Carrier - center frequency of channel / transmission
•DNR - dynamic range
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Decibel
•dB is unit-less, denotes logarithmic
•value dB = 10log10(value)
•value = 10^(value dB / 10)
•Standard exponential rules apply
•Cannot multiply value together
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db Suffixes
•dBW: Watts
•dBm: miliWatts
•dBi: forward gain of antenna
•dBc: relative to carrier
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Gain / Loss•Gain is the Amplification of signal
(unitless). 3db gain is an amplification of 2x.
•Linear: Power * gain(amp) = final power
•dB: Power + gain(amp) = final power
•Linear: Gain = 1/Loss
•dB: Gain = - Loss
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Sample Calculations
•5dB + 10dBw = 15dBw
•-3dBw = 27dBm
•-3dBm + 3dBm = ????
•10dBm = 10 mW = 0.01 W
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More Examples
•3dB ~= 2
•6dBm ~= 4 mW
•13dB ~= 20
•20dB = 100
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Test Equipment
•Spectrum Analyzer
•Verify emissions
•demodulate packet
•Network Analyzer
•Impedance Matching
•Power Meter
•Anechoic Chamber
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RF Options
•Don’t do it -> go wired (really)
•Modules
•PDB Design
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Wires: The easy option
•Batteries are annoying
•Reliability
•Throughput
•Don’t have to mess with the FCC... much
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RF Frequencies: ISM
•2.45GHz: Wifi, Bluetooth, 802.15.4, Cordless Phones
•1W peak power
•915 MHz: UHF RFID, Cell Phones
•1W peak power
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Classic Bluetooth
•Interoperability
•Android
•Power hungry
•3mA connected
•30mA connecting
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Classic Bluetooth
•AT Command Set
•Control
•UART passthrough (SPP)
•Transparent to software
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Bluetooth Smart•Interoperability
•iOS
•Window 8
•Low Power
•~40uA - 150uA connected
•18mA transmitting (max ~300us burst)
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XBee
•Serial passthrough
•Pair two devices
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Wifi
•Interoperability
•Anything with network access
•web pages
•telnet
•Complex - TCP/IP
•High Power
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Proprietary
•Non-Interoperability
•Vendor lock in
•Minimal overhead
•Depending on implementation, can be very low power.
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RF Modules: 2.4Ghz
Module StandardsPower RX
(idle)Throughput
XBee 802.15.4 40 mA 250KbpsGS1011
MIP802.11b
150mA (150uA)
11Mbps
RN-171 802.11b/g120mA (15mA)
54Mbps
nRF24L01+
Proprietary
11.3mA (22uA)
2Mbps
RN-42 Bluetooth 30mA (26uA) 240Kbps
BR-LE4.0BluetoothL
E27mA (0.9uA) 1Mbps
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RF Modules: 2.4Ghz
Module Interface API DNR $
XBee UARTPassthroug
h99dB 23
GS1011MIP
UART / SPI Custom 90dB 28
RN-171 UART / SPI Custom 93dB 30nRF24L0
1+SPI Packet 82dB 20
RN-42 UART / SPIPassthroug
h84dB 16
BR-LE4.0 UART / SPIAT
Commands96dB 119
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Custom PCB vs Module
•Lower Cost than modules in volume
•Full control over design
•Smaller size
•Must go through complete certification process
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PCB Considerations
•εr: Affects thickness of PCB
•Ground Plane
•Controlled Impedance
•Manufacturer Recommendations
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FCC Regulations
•Covers Unintentional Radiator
•And Intentional radiators
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Unintentional Radiators
•Digital Device operating at 9kHz+
•Must be Verified.
•Manufacture makes measurements.
•Submittal of measurements / sample unit only required if FCC asks.
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Intentional Radiators
•Digital Device operating at 9kHz+
•Must have a Declaration of Conformity
•You declare part complies with FCC regulations.
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FCC Certification
•Form 731
•$1265.00 Fee
•Measurement Results / Report
•System Block Diagram
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FCC Exceptions:Subassemblies
•Subassemblies
•Do not need to be certified / verified
•End user will need to FCC certify
•Home-built devices
•Up to 5 of any non-marketed, non-kit
•Personal use only.
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FCC Requirements: 15.247 (2.4GHz)
•1W peak Power
•spurious emissions: 20dB below carrier
•And many more...
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FCC Requirements:
47 CFR 2•Must retain description of faciility
•List of equipment used
•Must retain original drawings, records of procedures and measurements made.
•Retain all data required to show conformity.
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PCB Considerations
•Software?
•Module vendors usually give you their stack and examples
•Chip vendors don’t support small companies often.
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PCB Considerations
•Antenna
•Chip Antenna? (expensive)
•Trace Antenna? (cheap)
•RF Connector? (expensive)
•Impedance Matching
•balun?
•Tuning components
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References•FCC 47 CFR 15: Radio Devices
•FCC 47 CFR 2 Subpart J: Equipment Auth
•http://www.sparkfun.com/tutorials/398
•Example FCC report: http://faenl.msi.com/ftp/CE%20Documents/68xx/BTHub/41104402-RP1%20Part%2015.247.pdf