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An Ultra Broad bandDemodulator for Microwave
FM Receiver
Presented By:Sruthi.M.A
M1 MTV
5/1/2012
Guided By :Dr.Santhosh Kumar S
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Overview
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Introduction
Existing System
New FM Demodulator
Simulation
Experimental Verification
Conclusion
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Introduction
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Microwave Communication
Frequency Modulation
Why Frequency Modulation ?
FM Demodulators
Direct Demodulators
With Limiter & FM-AM conversionQuadrature Detector
Foster-Seeley Discriminator
Using Delay Line
Indirect Demodulator
PLL
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Existing System
Fig.1.Frequency Detector with limiter and FM-AM conversion
Fig.2.Phase Discriminator or quadrature detector
Fig.3.Detector type frequency discriminator
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Continued..
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Fig .4. Simplified block diagram of a mixer type
frequency discriminator
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Novel Frequency Demodulator
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Components
Power Splitter
Delay Line
90 Hybrid
Phase Detector
Low Pass Filter
Amplifier
Analog Multiplier
Operational Amplifier
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Demodulator Analysis
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Contd..
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Contd..
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Simulation
Fig .6. Input bit stream of a GSM signal and
demodulator output.
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Fig. 7. Photograph of the constructed setup for
evaluating the proposed demodulator
Experimental Verification
Power Splitters
42100 (Anaren)90 Hybrid
Amplitude imbalance
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Fig. 8. Evaluating setup for the proposed
demodulator
Experimental setup
Signal Generator
Frequency Modulation
capability
14- bit ADC & FIFO
Evaluation Boardsampling and recording
data
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Results
1 MHz sinusoid as modulatingsignal
Square waveform as modulatingsignal
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Fig.9. Modulating signal & DemodulatorOutput
Fig.10. Modulating signal &Demodulator Output
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Total Harmonic Distortion
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Demodulator Bandwidth
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Depends on frequency
response of baseband
stages
11.8MHz
Independent of carrier
frequencies, delay
quantities,FM
deviations
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Demodulator amplitude Response
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BER Measurement
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Network analyzerANT 20 SE
Variable gain
amplifier with
manual tuining
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Bit Error Rate
Fig. 16. BER versus input signalpower at 3 GHz
Fig.17. BER versus input signalpower at 17 GHz
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Conclusion
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New scheme for direct frequency demodulator introduced
Broadband frequency range showed no dependency on carrier frequency
No need of tuning elements
Can be implemented in IC technology with an external delay line
BER, Amplitude Response, Total Harmonic Distortion etc showed good
correspondence
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References
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1. S.R.Kurtz,Mixers as phase detectors, Watkins-JohnosonCompany, Palo Alto,CA,Tech. Note, vol. 5, no. 1,1978
2. H.Gheidi and A.Banai, Phase-noise measurement of microwave
oscillators using phase-shifterless delay-line discriminator, IEEE
Trans Microw. Theory Tech, vol. 58, no.2,pp.468-477,Feb.2010
3.
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Thank you
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