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. 2 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 Low Noise Amp Mixer IF Amp Demodulator Filter Rx In Data Out Synthesizer Synthesizer Modulator Tx Out Power Amp Data In Mixer 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 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 10 Diode Mixer Double balanced BPSK Mixer/Modulator 11 Off-the-shelf Mixer 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 12 Important Specs Third Order Intercept Point, 1 dB Compression Noise Figure 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 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 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 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 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 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 # 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 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 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 22 Cost Breakdown Modulator: $9 LNA: $4 Antenna: ? Power Amp & IF Amp: $2 - $15 Filter: $2 - $15 Miscellaneous Components: ? PCB Board and Manufacturing: ? 23 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. 3rd Finalized preliminary design – Jan. 17th Component list Cost analysis Finalized system diagram DFMEA/Design review issue resolution Place orders for parts – Jan. 21st Begin PCB layout – Jan. 31st 26