IMS2011 Wideband Direct Digital Radio Modeling and Verification Rulon VanDyke 1, David Leiss 2 1 Agilent Technologies, Alpharetta, GA, USA 2 Agilent Technologies, Manassas, VA, USA
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
Direct Conversion Receiver 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 Slide 3
ADC Undersampling Example Slide 4
Spectral Domain Analysis Applied Waveforms: GSM - 1934 MHz GSM - 834.78 MHz WCDMA - 873 MHz WCDMA 2110 MHz Slide 5
ADC Undersampling Results Signals at the ADC Input map into the first Nyquist Zone (DC 85 MHz) Input RF Spectral Domain Waveforms ADC Output Aliased Spectral Domain Waveforms ADC Fs/2 (85 MHz) Slide 6
Cascaded Spectral Analysis ADC Limits Dynamic Range Slide 7
Modeling the Receiver 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? Slide 8
Using Wideband Measured Data Measured Wideband Spectra Binary File Downloader File Size: ~ 16.77 MB Sim. Time: ~ 15 Sec. 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 Results: A Practical Sim. All Signals will be present at the receiver input, just like the real-world! Slide 9
Wideband Direct Digital Radio ADC Output Spectrum DC 2850 MHz Filtering & Downsampling Anti-Alias Filter Slide 10
OFDM Direct Digital Radio Receiver OFDM Slide 11
OFDM Direct Digital Radio Measurement at Output: Measurement at ADC input: Slide 12
Summary 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 Slide 13
Product Web sites: IMS2011 in Baltimore: A Perfect Match References & Resources 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 Challenges http://www.agilent.com/find/sdr http://www.agilent.com/find/powerofx Videos: Web video of CR Testbed discussed in this paper: http://www.agilent.com/find/eesof-cognitive-whitepaper Slide 14