RF/Antenna/Communication Systems, by Bradden (Brad) K. Cowan

I have more than 20 years of design, analysis, and modeling experience with RF, antenna, communications, and EW/SIGINT systems to apply to your project.
Bradden (Brad) K. Cowan | 43 McQuade Brook Rd, Bedford, NH  03110
home: (603) 488-5781 ; cell: (510) 326-6314
E-mail: brad.cowan@bkcconsulting.net

Objective: Principal RF Systems Engineer/Consultant

  • BSEE + graduate course work in antenna and RF systems (net-centric electronic warfare, antennas & propagation, radiowave propagation, microwave circuits, Fourier analysis)
  • 20+ years engineering experience in satellite communications systems & RF payload design, airborne surveillance and direction finding, free-space optical communications, radar warning receiver systems
  • Familiarity with design and implementation of microwave chips, circuits, components and systems
  • Experienced with link analysis and link margin in the presence of signal processing impairments
  • Working knowledge of modulation waveforms and digital signal processing (DSP) techniques
  • Experienced in conceptualization of technical approaches, generation of plans to implement the concepts, and directing the technical team to attain the goals
  • Strong working knowledge of RF, antenna and communications systems and component design
  • Proficient at performing RF cascade analysis and analyzing dynamic range, intercept point, sensitivity, noise figure, spurious analysis
  • Working knowledge of RF propagation and antenna/EM theory and design
  • Strong analysis/simulation background using Matlab/Simulink, ADS, HFSS, CST MWS, SPW
  • Familiarity with correlation interferometer based direction finding and geolocation techniques
  • Excellent verbal/written communication skills for making verbal presentations and preparing proposals
  • Active DoD Secret clearance, Top Secret inactive < one year, current SSBI, TS/SCI w/poly inactive 4 years.
Professional Experience: |
July 2009 to February 2010
Sr. Principal RF/DSP Systems Engineer
BAE Systems E&IS, Hudson, NH
  • Lead RF systems engineer for proposal to upgrade low band (VHF/UHF) airborne acquisition and early warning electronic support measures radar warning system. Performed RF propagation analysis for emitters, analyzed sensitivity and dynamic range performance, assessed direction finding (DF) and geolocation system performance while determining optimum antenna locations to meet DF/geo requirements.
  • Lead systems engineer for field demonstration of a vehicle mounted RF active/passive system for detection, direction finding and geolocation of IED trigger devices using correlation interferometer techniques.
January 2006 to May 2009
Sr. Lead System Engineer
General Dynamics Advanced Information Systems, Santa Clara, CA
  • Modeled and analyzed Radar Warning Receiver Switched Filter Bank design using ADS, translated layout to Mentor Graphics DxDesigner/Expedition, analyzed and verified RF/EM performance using Momentum.
  • Lead systems engineer for high performance antenna and front-end RF concept design for handheld UHF mobile satellite terminal. Performed electrically small broadband antenna configuration trade study and comparative analysis for gain, radiation pattern, & field distribution for folded patch, sleeve dipole, monopole, and quadrifilar helix using CST MWS; developed and tested prototype antenna for verification. Analyzed overall communication system link performance as a function of data rate, duty cycle and environment (urban, rural, foliage). Generated concept design for high-efficiency RF power amplifier using Doherty configuration with envelope tracking.
  • Designed ground-based beamformer element separator triple conversion superhet receiver, including cascade modeling and analysis of linear distortion, dynamic range, gain, noise figure, spurious. Specified RF filters, mixers, amplifiers. Wrote test requirements and compliance matrix. Tested prototype in lab using spectrum analyzer, synthesizer, and vector network analyzer.
  • Modeled & analyzed 4-input, 6-output passive beamforming network using 90° & 180° hybrids feeding six-element antenna in a two-channel monopulse tracking system using ADS. Performed Monte Carlo analysis to determine phase and amplitude balance requirements. Test hybrids in lab for verification.
  • Proposed candidate architectures combining and extending elements of existing UAV payload offerings into an integrated Predator-class payload suitable for broadband detection and geolocation of signals and targets.
  • Analyzed and modeled V-band QPSK satellite crosslink for GPS III to assess BER with user specified transmit carrier phase noise profile and digital Costas PLL phase tracker implemented in receiver.
  • Wrote Matlab program to generate 30 MHz instantaneous bandwidth multi-carrier complex sampled spectrum with user-specified # of carriers, modulation (CW, MPSK, MQAM, MFSK, AM, FM), carrier frequency, data rate, SNR, and AOA for development of SIGINT/COMINT receiver DF algorithms.
  • Wrote Matlab program to compute link degradation vs. untracked phase noise vs. modulation type (BPSK, QPSK, 8PSK, MSK, GMSK, CPFSK) using closed-form equations .
December 2001 to December 2005
Sr. Staff Communication Systems Engineer
Lockheed Martin Integrated Systems & Solutions, San Jose, CA & Space Systems Company, Sunnyvale, CA
  • Principal Investigator for Free Space Optical Communications IRAD. Provided technical oversight of five engineers investigating distortion mitigation techniques (FEC coding, Reed Solomon, interleaving, site diversity) for free-space optical communication link design. Performed statistical analysis of measured received data to determine fading distribution and probability density function. Simulated BER performance w/FEC and interleaver using Matlab. Responsible for customer presentations, briefings, and documentation.
  • Principal Investigator for Communications-On-The-Move IRAD for Transformational Satellite (TSAT) communications system (Advanced EHF satellite serving as leveraged program). Analyzed satellite antenna pointing accuracy and receiver acquisition & tracking requirements to support frequency hopped communications at T1 data rates between geosynchronous onboard processed payload and land mobile terminals over various types of terrain and environments. Investigated EHF propagation channel modeling, Doppler correction, error correction coding, interleaving, link-layer ARQ (automatic repeat request).
  • Analyzed and generated requirements for Airborne Lasercom Terminal (ALT) Technical Reference Architecture (TRA) proposal supporting optical communications for ISR (Intelligence Surveillance & Reconnaissance) and command and control aircraft and transformational communications initiatives requiring laser transmission of sensor data at high data rates over TSAT. Features include integrated communication and networking capabilities, heterogeneous RF and optical links, SONET/SDH, onboard gateway & routing, network capacity brokering. Investigated integration of ALT communications capability into the FAB-T (Family of Advanced Beyond-Line-of-Sight terminal) architecture and interfaces.
  • Lead developer for Mobile User Objective System (MUOS) waveform channel simulator model using Matlab and ADS. Led team of five consultants to develop an end-to-end waveform channel simulation model for a mobile geosynchronous satellite communications system based on Wideband CDMA (3GPP) with cell tower extended to space segment (“cell tower in the sky”). Modeled WCDMA waveforms, multiport power amplifier (PA), modulation/demodulation and BER performance as a function of backoff from saturation, number of CDMA users per channel, and carrier spacing. Model used to derive system performance requirements and flow down to subsystem level.
  • Analyzed electromagnetic self-interference for multi-transponder scientific/sensor satellite payload to determine transmit/receive filter requirements.
October 2000 to October 2001
Hardware System Engineer for 60 GHz Gigabit Radio Project
Agilent Technologies, Wireless Semiconductor Division, Santa Clara, CA
  • Analyzed, modeled, and specified a 1.25 Gbps FSK radio using Agilent ADS to determine FM modulation index, filter requirements, and frequency discriminator to meet FCC out-of-band emission and timing jitter requirements. Allocated system requirements to RF components.
  • Designed millimeter wave 60 GHz coplanar waveguide antenna using Momentum and HFSS. Antenna design was a coplanar waveguide fed, /2 slot dipole, with hyper-elliptic ceramic lens and hemispherical antireflection shell. Analyzed input impedance, radiation pattern, sidelobes, gain and subharmonic rejection for parametric perturbations in lens geometry and single vs. dual slots. Generated far field 3D plots and 2D plots. Supervised testing of prototype and comparison with simulated data.
March 1997 to October 2000
Advanced Programs Analyst & Payload Engineer
Space Systems/Loral, Palo Alto, CA
  • Designed CD Radio/XM/Sirius S-band high-power transmit payload including
    • Monte Carlo analysis/simulation to assess phase matching requirements for multi-port antenna.
    • Allocation of phasing requirements to payload RF components
    • Layout of waveguide combining and redundancy ring to minimize phase dispersion
    • Analysis of harmonic filter rejection requirements for CDMA vs TDMA waveforms.
    • Developed budgets for phase, gain, noise figure, intermodulation distortion, AM/PM etc.
    • Developed test requirement documents
  • Analyzed spectral regrowth for CDMA traffic through linearized TWT.
  • Analyzed adjacent channel interference (ACI) for three QPSK carriers through non-linear transponder
  • Analyzed carrier-to-interference ratio (C/I) and NPR as a function of carrier position and number of carriers for multiple QPSK signals through satellite transponder.
  • Developed spectral plots and 99% BW estimates for analog FM/PM and digital M-PSK signals for meteorological and aeronautical payload.
  • Co-authored IRAD report, “Higher order modulation signals for satellite,” investigating QPSK, 8PSK, 16QAM, Trellis-coded 8-PSK, determination of optimum backoff for fixed BER
  • Performed analysis/simulation for Globalstar CDMA system with phased array S-band transmit antenna to determine compliance with ITU spectral mask* (*received Employee Recognition Award) .
Additional Engineering Experience
6/95-3/97 ArgoSystems, Test and Measurement Division, Sunnyvale, CA
  • Principal RF engineer for Global Broadcast System (GBS) airborne burst receiver development.
    • RF system analysis and specification of antenna, RF up/down converters.
    • Modification to COTS LNB to accept phase locked external reference.
    • Generation of QPSK IF test vectors with Gaussian or root raised cosine pulse shaping
  • Analyzed RF system and filter requirements for C band frequency modulated continuous wave (FMCW) aircraft radio altimeter system .
  • Developed Test Requirements Documents (TRDs) for frequency discriminator circuit card and LO frequency synthesizer assemblies used in airborne AWACS E-3 ESM System.
8/92-6/95 Stanford Linear Accelerator Center, Menlo Park, CA
  • Designed RF signal generation, detection, control, and interlock circuitry for test of UHF high power klystron amplifier using analog and digital circuitry.
2/89-8/92 Loral (now Lockheed) Western Development Labs, Wideband Receiver Design, Palo Alto, CA
  • Designed 3 GHz OQPSK multi-rate modulator
    • Performed RF system design/analysis and specified phase locked LO phase noise requirements.
    • Designed wideband amplifier/select module & analog/digital control & status card.
10/88-2/89 Litton Applied Technology Division, San Jose, CA
  • Analyzed antenna patterns.
  • RF front end noise figure/gain budget for EW RWR/antenna system proposal.
2/88-9/88 Microwave Modules & Devices (now Spectrian), Mountain View, CA
  • Designed and developed RF solid-state power amplifier modules.
  • Combined modules into 1 kW transmitter.
Education & Short Courses:
  • In progress – MSEE w/Sensor Systems Engineering option, Naval Postgraduate School, Monterey, CA. Course work includes Radiowave Propagation, Net-centric Electronic Warfare, Antennas and Propagation
  • 1989-90 Santa Clara U., Santa Clara, CA, graduate courses in Active Microwave Circuits & Fourier analysis
  • 1987 BSEE, San Jose State U., San Jose, CA (electromagnetics, field and waves, microwaves, fiber optics, communication theory, analog and digital electronics, semiconductor device physics, control systems)
  • Satellite Communications Payload Design and System Architecture, Short course, UCLA Extension
  • Simulation of Communication Systems using Agilent Advanced Design System, Short course, Agilent
  • Simulation of Communication Systems using Signal Processing Workstation, Short course, Cadence
Clearances: |
Active DoD Secret with current SSBI
Top Secret inactive since June 2009
TS/SCI w/poly inactive since December 2005
Modeling/Simulation Tools: |
Proficiency in each of the following
  • Matlab/Simulink
  • CST Microwave Studio, HFSS, Momentum, EMPro, EZNEC
  • Agilent Advanced Design System, Momentum, Genesis
  • AWR Microwave Office & Visual System Simulator
  • Signal Processing Workstation (SPW)
  • Mathcad
  • Satellite Tool Kit (STK)
Test Equipment & Hardware-In-The-Loop Simulation Experience: |
  • Downloaded complex I/Q samples generated in Matlab to Agilent E4438C for use in developing SIGINT detection algorithms.
  • Interfaced WCDMA waveforms to prototype SSPA using ESG signal generator and Vector Signal Analyzer using Agilent ADS and Matlab.
  • Experienced using the following instruments: Vector Signal Analyzer, Network Analyzer, Spectrum Analyzer, Phase Noise Test Set, Noise Figure Meter, Digital Oscilloscope
Awards & Achievements: |
  • STAR Employee Achievement Award, GDAIS, Phase Noise vs. Modulation Analysis
  • Employee Recognition Award, Space Systems/Loral, CDMA Spectral Emissions Mask analysis
References: |
Available Upon Request