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Analysis and Design of an Rf Front End for a Radar Digital Receiver

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Analysis and Design of an Rf Front End for a Radar Digital Receiver ANALYSIS AND DESIGN OF AN RF FRONT END FOR A RADAR DIGITAL RECEIVER A Thesis Presented to the Faculty of California State Polytechnic University, Pomona In Partial Fulfillment Of the Requirements for the Degree Master of Science In Electrical Engineering By John O. Mortensen 2018 SIGNATURE PAGE THESIS: ANALYSIS AND DESIGN OF AN RF FRONT END FOR A RADAR DIGITAL RECEIVER AUTHOR: John O. Mortensen DATE SUBMITTED: Winter 2018 Electrical and Computer Engineering Department Dr. James Kang Thesis Committee Chair Electrical Engineering Dr. Thomas Ketseoglou Electrical Engineering Dr. Saloman Oldak Electrical Engineering ii ACKNOWLEDGEMENTS First, I’d like to thank my adviser Dr. James Kang for the patient help he has provided over the two years of my pursuit of my master’s degree. In addition I’d like to thank Dr. Ketseoglou and Dr. Oldak and the rest of the staff at Cal Poly for all of the great electronics courses I’ve taken both recently and back in the 1980s when I first received my BSEE. I’d should also thank MPT and its owner Dr. Rick Sturdivant for the help on this project and the funding available to complete this research and project. I’d also like to thank my wife Marie for putting up with me and the support she has given me over the years. iii ABSTRACT This paper focuses on the use of commercial off the shelf parts in the design of an X Band receiver used in radar. The need today for a low cost flexible approach is of the utmost importance due to the trend of having a transceiver module for each element of a phased array antenna. Therefore, smaller and cheaper units are being demanded. An analysis of the given specifications is first presented. A detailed specification is developed and then the analysis and design is covered for each of the main components in the analog section. Several of the components are measured individually and the resulting test data is reported. The individual component test data provides information required for modeling of the receiver and confirms performance. The digital portion of the receiver includes an analog to digital converter (ADC) evaluation board. Since the focus of this research is on a low cost, high performance analog front end the ADC was used for capturing the data. A detailed model is developed using an Excel spreadsheet. It calculates system level performance parameters such as gain, noise figure, third order intercept point, large signal maximum before damage and dynamic range. The spreadsheet can be used to optimize the design for desired results. A circuit board of the analog section was designed, assembled and measured. It was connected to the ADC evaluation board for measurements. The measured data confirms the predicted performance from the spreadsheet analysis. The research demonstrates that a cost effective and high performance digital receiver is achievable. iv TABLE OF CONTENTS SIGNATURE PAGE ......................................................................................................... ii ACKNOWLEDGEMENTS ............................................................................................... iii ABSTRACT ....................................................................................................................... iv LIST OF FIGURES .......................................................................................................... viii CHAPTER 1 ...................................................................................................................... 1 Introduction ......................................................................................................................... 1 CHAPTER 2 ...................................................................................................................... 3 Block Diagram and Specifications ...................................................................................... 3 Block Diagram ................................................................................................................ 3 Front End RF Section...................................................................................................... 4 1st IF Section ................................................................................................................... 4 2nd IF Section .................................................................................................................. 5 Separate ADC Digital Receiver Processor ..................................................................... 5 Specifications .................................................................................................................. 5 Frequency Input .............................................................................................................. 6 Power Input Max with No Damage ................................................................................ 7 RF Input Level ................................................................................................................ 7 LO Frequencies ............................................................................................................... 7 ADC Requirements ......................................................................................................... 7 Output Frequency............................................................................................................ 8 ADC Sampling Rate ....................................................................................................... 8 v ADC Bits ......................................................................................................................... 8 Dynamic Range Specifications ....................................................................................... 8 Noise Figure .................................................................................................................... 8 Linearity ........................................................................................................................ 11 Intermodulation Distortion............................................................................................ 12 3rd Order Intercept Point ............................................................................................... 14 Compression ................................................................................................................. 18 Mixer Products .............................................................................................................. 19 Spurious Free Dynamic Range ..................................................................................... 19 Image Rejection ............................................................................................................ 20 CHAPTER 3 .................................................................................................................... 23 Design ............................................................................................................................... 23 Approach ....................................................................................................................... 23 Description .................................................................................................................... 24 Design Simulation and Compliance.............................................................................. 25 CHAPTER 4 .................................................................................................................... 28 Components ...................................................................................................................... 28 Front End RF Section.................................................................................................... 29 Limiter........................................................................................................................... 29 First RF Preselect and Image Filter .............................................................................. 30 First Variable Attenuator .............................................................................................. 32 First Low Noise Amplifier (LNA) ................................................................................ 33 Second Variable Attenuator .......................................................................................... 34 Second LNA.................................................................................................................. 34 Second RF Preselect and Image Filter .......................................................................... 34 vi RF Mixer ....................................................................................................................... 35 Passive Attenuators ....................................................................................................... 35 1st IF Section ................................................................................................................. 36 IF Filter ......................................................................................................................... 36 IF Amplifier .................................................................................................................. 38 IF Mixer ........................................................................................................................ 39 2nd IF Section ...............................................................................................................
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