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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
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Simulations of sub-circuit designs in PSpice
3
Functional Requirements
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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
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Specifications
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Transmission range of 20 – 30 meters
Antenna and transmission power of 12 dBm
870-900 MHz carrier frequency
Data throughput of 40kbps
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System Block Diagram
Low Noise
Amp
Mixer
IF Amp
Demodulator
Filter
Rx In
Data Out
Synthesizer
Synthesizer
Modulator
Tx Out
Power Amp
Data In
Mixer
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Analysis Breakdown
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Transmitter
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Mixer/Modulation
Power Amplifier
Antennas
Receiver
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LNA
Filter
IF Amplifier
Demodulator
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Mixer/Modulation
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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
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BPSK Modulation
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BPSK = Binary Phase Shift Key
Binary 1 represented by 180° phase shift in
carrier signal
Binary 0 has no phase shift
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Diode Mixers
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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
Number of
Diodes
RF Input
Match
RF-LO
Isolation
Conversion
Loss
Third-Order
Intercept
Single-Ended
1
Poor
Fair
Good
Fair
Balanced
(90°)
2
Good
Poor
Good
Fair
Balanced
(180°)
2
Fair
Excellent
Good
Fair
Double
Balanced
4
Poor
Excellent
Excellent
Excellent
Image Reject
2 or 4
Good
Good
Good
Good
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Diode Mixer
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Double balanced BPSK Mixer/Modulator
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Off-the-shelf Mixer
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RF2638 Upconverter/BPSK
modulator
Specs:
IF Input
LO Input
Output
IF to LO
Isolation
30 dB
-
-
RF to LO
Isolation
30 dB
30 dB
-
Noise Figure
-
-
14 dB
IP3
-
-
13 dBm
Conversion
Loss
-
-
0.5 dB
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Important Specs
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Third Order Intercept Point, 1 dB
Compression
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Noise Figure
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Figures of merit that describe linearity of device
High IP3 desirable
Noise (in dB) added to amplified signal by
amplifier circuitry
Average 1.5 dB for LNA, 5 dB for PA
Input and Output Impedances
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Power Amplifier
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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
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Power Amplifier
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Linx Technologies
BBA-519
Spec
Value
Operating
Frequencies
10MHz – 4 GHz
Gain (1 GHz)
17 dB
Noise Figure
4.8 dB
Output IP3
+33 dBm
VSWR (in, out)
2.1:1, 1.8:1
Max Output Power
+17 dBm
Operating Voltage
(single supply)
4.8 – 5.2 V,
5.2 – 12 V w/ R
Operating Current
60 mA
minicircuits.com amplifier selection guide
15
Antennas
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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
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Low Noise Amplifier
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First component of receiving unit
Amplifies weak signal picked up from
antenna while contributing minimal noise
Resulting output is sent to mixer
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Low Noise Amplifier
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Choices from various
manufacturers
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Input impedance will be
properly matched with the
antenna for an optimal SWR
LNA
SA601
MSA0685
MAX2642
MAX2640
Gain
18 dB
19 dB
16.7 dB
15.1 dB
Noise Figure
1.6 dB
3 dB
1.35 dB
0.9 dB
Current Draw
4.4 mA
na
5.3 mA
3.5 mA
na
na
Size
2.0x2.1 mm 2.7x2.9 mm
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Filter
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Bandpass filter used to reject unwanted
frequency products and pass signals of the
selected IF
Important Specs
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cutoff frequency/center frequency
passband and stopband
insertion loss
out of band attenuation
VSWR
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Filter
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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 #
Filter type
Center
frequency
VSWR
Passband, Stopband
MC LCFN-80
Low pass
145 MHz
1.2:1, 20:1
MC SCLF-95
Low pass
108 MHz
1.7:1, 18:1
MC PHP-150
High pass
120 MHz
1.8:1, 17:1
MC PHP-100
High pass
82 MHz
1.5:1, 17:1
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IF Amplifier
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Boosts the level of the filtered IF signal so
that it can be accurately demodulated
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More options for selection due to operation at
the IF rather than the carrier frequency
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IF Amplifier
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Linx Technologies
BBA-322
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High gain version of
BBA-519
minicircuits.com
amplifier selection
guide also has options
Spec
Value
Operating
Frequencies
10 MHz – 3 GHz
Gain (1 GHz)
20 dB
Noise Figure
3.8 dB
Output IP3
+22.5 dBm
VSWR (in, out)
2.3:1, 2.1:1
Max Output Power
+10 dBm
Operating Voltage
(single supply)
4.8 – 5.2 V,
5.2 – 12 V w/ R
Operating Current
35 mA
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Cost Breakdown
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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
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Antenna Selection
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Complex design
Physical properties
Impedance matching
Range & frequency considerations
Accounting for mismatches in available
components
Power supply requirements for each
component
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Next Steps
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Finalize component selection
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Impedance matching
Biasing considerations
Signal level
Order components
Test equipment training
Begin testing components
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Schedule
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Further component research – Dec. 3rd
Finalized preliminary design – Jan. 17th
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Component list
Cost analysis
Finalized system diagram
DFMEA/Design review issue resolution
Place orders for parts – Jan. 21st
Begin PCB layout – Jan. 31st
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