Wideband Direct Digital Radio Modeling and Verification Rulon VanDyke 1, David Leiss 2

Transcription

1 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

2 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

3 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

4 ADC Undersampling Example Slide 4

5 Spectral Domain Analysis Applied Waveforms: GSM MHz GSM MHz WCDMA MHz WCDMA 2110 MHz Slide 5

6 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

7 Cascaded Spectral Analysis ADC Limits Dynamic Range Slide 7

8 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

9 Using Wideband Measured Data Measured Wideband Spectra Binary File Downloader File Size: ~ MB Sim. Time: ~ 15 Sec. Measurement based.sdf file Frequency Range: DC GHz Sequence Length: ~ msec ~ 4.3 Million Samples IQ Samples File Size: ~ 3.9 Gigabytes Sample Rate: 3200 MHz Time Step: 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

10 Wideband Direct Digital Radio ADC Output Spectrum DC 2850 MHz Filtering & Downsampling Anti-Alias Filter Slide 10

11 OFDM Direct Digital Radio Receiver OFDM Slide 11

12 OFDM Direct Digital Radio Measurement at Output: Measurement at ADC input: Slide 12

13 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

14 Product Web sites: IMS2011 in Baltimore: A Perfect Match References & Resources SystemVue RF sensors Whitepapers and application notes: Cognitive Radio Algorithm Development and Testing: - Software Defined Radio Measurement Solutions: - Solutions for Addressing SDR Design and Measurement Challenges Videos: Web video of CR Testbed discussed in this paper: Slide 14