Transcript Slide 1
Mid-Semester Design Review
High Frequency Radio with BPSK Modulation
Goal Statement
Our project is to design and build a wireless 900 MHz transmitter and receiver for Simply Test, LLC. The transceiver is to conform as closely as possible to the IEEE 802.15.4a standards for Low Rate, Wireless Personal Area Networks (LR-WPAN) and utilize Binary Phase Shift Key (BPSK) modulation.
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Deliverables
Working transceiver prototype Sub-circuit designs for amplifiers and filter Simulations of sub-circuit designs in PSpice 3
Functional Requirements
Transmit and receive binary data High carrier frequency Low power signal transmission Efficient high frequency PCB layout Conforms to IEEE 802.15.4a standards for wireless LANs Transmission range for a conventional wireless network 4
Specifications
Transmission range of 20 – 30 meters Antenna and transmission power of 12 dBm 870-900 MHz carrier frequency Data throughput of 40kbps 5
System Block Diagram
Rx In Low Noise Amp Mixer Filter Synthesizer IF Amp Demodulator Data Out Tx Out Power Amp Mixer Synthesizer Modulator Data In 6
Analysis Breakdown
Transmitter Mixer/Modulation Power Amplifier Antennas Receiver LNA Filter IF Amplifier Demodulator 7
Mixer/Modulation
Translation between a high frequency (the RF) and Intermediate Frequency (IF) The signal is imposed onto a carrier signal so that transmission circuits can be realized on a practical scale The modulation scheme defines how the signal is imposed onto the carrier signal for transmission 8
BPSK Modulation
BPSK = Binary Phase Shift Key Binary 1 represented by 180 ° phase shift in carrier signal Binary 0 has no phase shift 9
Diode Mixers
Provide a simpler topology compared to transistor based mixers Have a lower noise figure compared to transistor based mixers Have a higher conversion loss than transistor based mixers
Mixer Single-Ended Balanced (90 °) Balanced (180 °) Double Balanced Image Reject Number of Diodes
1 2 2 4 2 or 4
RF Input Match
Poor Good Fair Poor Good
RF-LO Isolation
Fair Poor Excellent Excellent Good
Conversion Loss
Good
Third-Order Intercept
Fair Good Good Fair Fair Excellent Good Excellent Good 10
Diode Mixer
Double balanced BPSK Mixer/Modulator 11
Off-the-shelf Mixer
RF2638 Upconverter/BPSK modulator Specs:
IF to LO Isolation RF to LO Isolation Noise Figure IP3 Conversion Loss IF Input
30 dB 30 dB -
LO Input
30 dB -
Output
14 dB 13 dBm 0.5 dB 12
Important Specs
Third Order Intercept Point, 1 dB Compression Figures of merit that describe linearity of device High IP3 desirable Noise Figure Noise (in dB) added to amplified signal by amplifier circuitry Average 1.5 dB for LNA, 5 dB for PA Input and Output Impedances 13
Power Amplifier
Boosts the level of the modulated signal for broadcast by the antenna Operates at the carrier frequency Need a specific output power level to achieve the 12dBm transmission power specification 14
Power Amplifier
Linx Technologies BBA-519
Spec
Operating Frequencies Gain (1 GHz) Noise Figure Output IP3 VSWR (in, out) Max Output Power Operating Voltage (single supply) Operating Current
Value
10MHz – 4 GHz 17 dB 4.8 dB +33 dBm 2.1:1, 1.8:1 +17 dBm 4.8 – 5.2 V, 5.2 – 12 V w/ R 60 mA minicircuits.com amplifier selection guide 15
Antennas
Broadcasts/receives the carrier signal Considerations: type, size, connector type, and impedance (typically 50 Ohms) AN-900S RF Antenna from rf-links.com: 896-930 MHz, 3 in. tall, BNC connector, omni Omni-Directional Yagi (directional) Dipole 16
Low Noise Amplifier
First component of receiving unit Amplifies weak signal picked up from antenna while contributing minimal noise Resulting output is sent to mixer 17
Low Noise Amplifier
Choices from various manufacturers Input impedance will be properly matched with the antenna for an optimal SWR LNA Gain Noise Figure Current Draw Size
SA601
18 dB 1.6 dB 4.4 mA na
MSA0685
19 dB 3 dB na na
MAX2642
16.7 dB
MAX2640
15.1 dB 1.35 dB 5.3 mA 0.9 dB 3.5 mA 2.0x2.1 mm 2.7x2.9 mm 18
Filter
Bandpass filter used to reject unwanted frequency products and pass signals of the selected IF Important Specs cutoff frequency/center frequency passband and stopband insertion loss out of band attenuation VSWR 19
Filter
Two realization options: One bandpass filter or a low pass filter cascaded with a high pass to create a bandpass filter Filter selection will depend on selected IF Possible filter selections: Model # MC LCFN-80 MC SCLF-95 MC PHP-150 MC PHP-100 Filter type Low pass Low pass High pass High pass Center frequency 145 MHz 108 MHz 120 MHz 82 MHz VSWR Passband, Stopband 1.2:1, 20:1 1.7:1, 18:1 1.8:1, 17:1 1.5:1, 17:1 20
IF Amplifier
Boosts the level of the filtered IF signal so that it can be accurately demodulated More options for selection due to operation at the IF rather than the carrier frequency 21
IF Amplifier
Linx Technologies BBA-322 High gain version of BBA-519 minicircuits.com amplifier selection guide also has options
Spec
Operating Frequencies Gain (1 GHz) Noise Figure Output IP3 VSWR (in, out) Max Output Power Operating Voltage (single supply) Operating Current
Value
10 MHz – 3 GHz 20 dB 3.8 dB +22.5 dBm 2.3:1, 2.1:1 +10 dBm 4.8 – 5.2 V, 5.2 – 12 V w/ R 35 mA 22
Cost Breakdown
Modulator: $9 LNA: $4 Antenna: ?
Power Amp & IF Amp: $2 - $15 Filter: $2 - $15 Miscellaneous Components: ?
PCB Board and Manufacturing: ?
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Potential Problems
Antenna Selection Complex design Physical properties Impedance matching Range & frequency considerations Accounting for mismatches in available components Power supply requirements for each component 24
Next Steps
Finalize component selection Impedance matching Biasing considerations Signal level Order components Test equipment training Begin testing components 25
Schedule
Further component research – Dec. 3 rd Finalized preliminary design – Jan. 17 th Component list Cost analysis Finalized system diagram DFMEA/Design review issue resolution Place orders for parts – Jan. 21 st Begin PCB layout – Jan. 31 st 26