IMS2011 in Baltimore: A Perfect Match
IMS2011
Wideband Direct Digital Radio Modeling and Verification
Rulon VanDyke1, David Leiss2
1 Agilent Technologies, Alpharetta, GA, USA2 Agilent Technologies, Manassas, VA, USA
IMS2011 in Baltimore: A Perfect Match
Typical Presentation Flow
• The “Ideal” Direct Conversion Receiver• A Basic Example of ADC Undersampling• ADC Undersampling Examples• Spectral Domain Analysis• Spectral Domain ADC Undersampling
Results• Cascaded Spectral Analysis• OFDM Direct Digital Radio
Slide 2
IMS2011 in Baltimore: A Perfect Match
Direct Conversion Receiver
Slide 3
AGC
Advantages:• A Minimum of Parts• Minimum of RF Parts• No Mixers• Filtering done in DSP• Wide Bandwidth • The Ultimate in Flexibility
Disadvantages:• DSP Processing Speed• Interference It’s a noisy a world out there! • ADC Dynamic Range• LNA Dynamic Range
IMS2011 in Baltimore: A Perfect Match
ADC Undersampling Example
Slide 4
IMS2011 in Baltimore: A Perfect Match
Spectral Domain Analysis
Slide 5
•Applied Waveforms:•GSM - 1934 MHz•GSM - 834.78 MHz
•WCDMA - 873 MHz •WCDMA – 2110 MHz
IMS2011 in Baltimore: A Perfect Match
ADC Undersampling Results
Slide 6
Input RF Spectral Domain
Waveforms
ADC Fs/2
(85 MHz)
ADC Output Aliased Spectral Domain
Waveforms
Signals at the ADC Input map into the first Nyquist Zone (DC – 85 MHz)
IMS2011 in Baltimore: A Perfect Match
Cascaded Spectral Analysis
Slide 7
ADC Limits Dynamic Range
IMS2011 in Baltimore: A Perfect Match
Modeling the Receiver
Slide 8
• All Microwave/RF receivers must function in high spectral density environments.• Most simulation models involve “ideal” signals with possibly AWGN.• In order to very that a radio design will work in the “real-world” we need to apply the same spectral content as will be expected.• How can this be done in a practical manner?• How does our reciever perform in this environment?
IMS2011 in Baltimore: A Perfect Match
Using Wideband Measured Data
Slide 9
Measured WidebandSpectra
•Measurement based .sdf file•Frequency Range: DC - 2.5 GHz •Sequence Length: ~ 1.342 mSec•~ 4.3 Million Samples IQ Samples•File Size: ~ 3.9 Gigabytes•Sample Rate: 3200 MHz•Time Step: 0.3125 nSec•Freq Resolution: ~745 Hz•Simulation Time: ~30 minutes
Binary File Downloader
•File Size: ~ 16.77 MB•Sim. Time: ~ 15 Sec.
Results:• A Practical Sim.• All Signals will be present at the receiver input, just like the real-world!
IMS2011 in Baltimore: A Perfect Match
Wideband Direct Digital Radio
Slide 10
Anti-Alias Filter
ADC Output Spectrum
DC 2850 MHz
Filtering & Down-sampling
IMS2011 in Baltimore: A Perfect Match
OFDM Direct Digital Radio
Slide 11
OFDM
Receiver
IMS2011 in Baltimore: A Perfect Match
OFDM Direct Digital Radio
Slide 12
Measurement at ADC input:
Measurement at Output:
IMS2011 in Baltimore: A Perfect Match
Summary
Slide 13
• Provided a basic review of a direct conversion ADC under-sampled receiver.
• Showed techniques for rapidly evaluating receiver performance in the spectral domain. Identified the limiting component in the receiver.
• Incorporated Measured data into SystemVue and converted it into a Binary format to save time and space.
• Evaluated a wideband direct conversion receiver. performance with applied measured signals covering DC to nearly 3 GHz.
• Preformed an OFDM Direct Digital Radio Simulation
IMS2011 in Baltimore: A Perfect Match
Slide 14
References & ResourcesProduct Web sites:
SystemVue http://www.agilent.com/find/systemvue
RF sensors http://www.agilent.com/find/rfsensor
Whitepapers and application notes:
Cognitive Radio Algorithm Development and Testing:http://www.agilent.com/find/eesof-cognitive-whitepaper
- Software Defined Radio Measurement Solutions:http://cp.literature.agilent.com/litweb/pdf/5990-4146EN.pdf
- Solutions for Addressing SDR Design and Measurement Challengeshttp://www.agilent.com/find/sdrhttp://www.agilent.com/find/powerofx
Videos:
Web video of CR Testbed discussed in this paper:http://www.agilent.com/find/eesof-cognitive-whitepaper
