RF Circuit / Microwave Circuit
Wireless Communications / Analog Engineer
Last updated: 20130517
For a more concise MS Word version look here (updated 20130517).
Expertise in RF/Microwave/wireless communications circuits and systems.
I'm a highly motivated individual with a broad skill set. My preference is to be working on RF and microwave communications systems as both a system designer and a detailed circuit designer. I consider myself qualified as an RF system designer as it applies to a radio product as well as a detail-oriented Microwave/RF circuit designer.
I enjoy working the tradeoffs in hardware design using a deep understanding of the systems and pure physical layer details (modem, RF impairments). When possible I enjoy understanding the customer's perspective on products to make sure that the solutions are appropriate for their needs. Sometimes a little time spent understanding the needs can save a lot of time/complexity/money.
In past jobs and in "hobby-space" I've done a fair amount of work with small to medium microcontroller and DSP Projects. I've also done some other bits and pieces of programming, some of which can be found on my tools page.
I am willing to work very hard to gain the confidence and respect of my employer and colleagues and I expect the same in return.
At this point in my career I prefer to remain a technical contributor leading/mentoring small technical teams as appropriate rather than taking the path of management. I have no interest in being isolated however I don't mind working as a sole contributor.
Consultant, RFdude.com LLC
1997-present (full time from June 2008-present)
Consulting and personal Projects:
- Transceiver system and where appropriate, circuit designs for 200, 700, 900 MHz, 2.8, 3.5, 4.6, 6.4, 10, 24 GHz. Most bold items made it to production though some failed to get traction.
- Frequency equalized switch board design for cabled broadband ( my contribution was the equalization).
- Design of high performance front ends for improving the selectivity of commodity radio chipsets.
- Brief study of a synchronizer (PLL-based) concept for a high speed optical communications system.
- Design of a VHF VCO for an amateur radio kit/product supplier
- 10 GHz Low noise amplifier, mixer, filter designs
- windows 2000 microchip PIC (tm) In Circuit Serial Programmer (as of early winter 2003 30-40 different flash PIC chips can be programmed (12F, 16F, 18F families). Project shelved (worked quite well, but a full time job keeping up with all the new PICs coming out!).
- Windows 2000 / GPIB projects (see the tools page)
- Completely stand-alone synthesized 1-2 GHz source employing a <$1 8-pin microprocessor (serial interface, EEPROM storage of frequency settings).
- Stand alone data acquisition/controller, "smart EEPROM" using a $1.00 8-pin microprocessor, single wire asynch. serial interface.
- Various microcontroller hardware/interfacing design projects
- general purpose interface board design using a synchronous serial bus with LCD keypad, rotary encoder inputs.
- High speed USB data acquisition system (for Phase noise measurement system)
- General purpose controller firmware with a decent command line parser.
- variable speed motor control & rotary position indicator (closed loop control when I get back to it...)
- <1.1dB NF, high dynamic range LNA for 144-1296 MHz (was typically <1.0dB from 144-903 MHz). OIP3 ~ +32 dBm, gain ~ 21 dB (~ 18 dB at 1296 MHz).
- <0.7dB NF, 903-1296 MHz LNA, similar to above, OIP3 > +27 dBm.
- prototype 12 to 28VDC converter, 15 amp output at 28v. 100 kHz push-pull design.
- Participated as an external reviewer for a deep-space receiver (Uplink) design being done at JHUAPL for the New Horizons program. Was invited back to participate in the Transmitter (Downlink) portion of the project as well.
- Several other proprietary projects not listed (commercial, defense, broadband).
- Many low cost frequency converters for clients (including simple mixer and synthesizer designs)
- Electronically tunable filters
Professional Roles and projects
RF/uWave Engineering Group Manager & Principal Microwave Engineer
Bosch Security Systems (Intrusion systems business unit)
Principal Microwave Engineer
- Involved primarily in the design of X-band Doppler motion sensors and short range wireless communications devices.
- I headed a very small team focused on RF and microwave hardware aspects.
Principal Engineer, RF
CEWD East Division of Titan (now part of L3-Linkabit division)
2/2004 - 2/2005
- Worked primarily on module level design for man-portable VHF tactical communications equipment.
Principal Engineer, RF design
Senior Development Engineer
6/1995 - 10/1998
- Involved in the development of narrowband through wideband point-point and point-multipoint systems between 200 MHz and 6 GHz.
I have worked on the RF system/circuit end of both point-point QAM radios as well as point-multipoint FSK based data radios. I have also spent a fair amount of time working with technologies geared towards broadband wireless internet access in the lower microwave bands. Troubleshooting/mentoring/supporting other projects also tends to take up a fair amount of my time over the course of any given year.
Specific design responsibilities & projects have included the following:
Miscellany December 2001-present
- Worked on a team as the technical lead to design a second generation
prototype linear broadband transceiver in the low microwave frequency range
- This also involved a brief period studying propagation models, using prediction software, and the team actually did some field path data collection.
- Designed a series of VCOs from 400 MHz to 1.8 GHz applied to this project
- Designed a very low noise 4.3 GHz synthesizer.
- Two projects that involved me as the primary contributor to move an existing microwave radio product to a new frequency band for demonstration purposes, provided prototype/demo hardware.
- Involved in many efforts to troubleshoot problems with various product families both in development and with shipping product.
- Provided system architecture proposals for a family of radios (two different products in a family) that were ultimately shelved but that offered some significant benefits over existing solutions at the company (mainly in manufacturability and reducing the number of variants in the product).
- Provided RF system design and planning for a 5.8 GHz QAM point-point radio development already under way, along with a couple of circuits.
UHF/SHF "R&D" July 2000 - December 2001
- studied, designed, evaluated the following discrete/ microstrip circuits in the 2-11 GHz frequency range
- LNA's, buffers
- Bandpass filters
- Based on success with the aforementioned circuits, I've proposed radio architectures based on them.
- Designed inexpensive($2-$4 or so in small quantities) medium/high performance VCO's in the 700-5000 MHz range. These designs seem comparable to commercially available ones that cost $4 to $12. Example, 700-900 MHz designs that tune about 100 MHz and achieve -100 to -108 dBc/Hz at 10 kHz offset, over a 3-4 volt range (20-40 MHz/volt). These are not the best, but certainly adequate for many things, and the performance improves with narrower (frequency) tuning ranges.
- Developed a 5 GHz DRO.
- Extensive analysis of phase noise and nonlinear distortion in QAM systems (analysis techniques developed on personal time, then applied to MDS projects).
- Full "complex baseband" analysis platform developed in MathCad for analyzing
- BER vs. Eb/No
- phase noise
- AM-AM/ AM-PM (from measured PA data)
- Effects of all of the above before and after block coding (got help on this!)
- Effects of group delay due to RF bandpass filters (eventually I plan on implementing an equalizer to better analyze the noise enhancement problems and slight degradations due to the filter rolloff).
- Spent a fair amount of my time, during certain periods, supporting other designs, previous products, etc.
FSK transceiver design project part time February 1999 through July 2000
- Worked with a team of engineers to come up with tradeoffs for making a new product with the goal of a more cost effective and flexible design. These technologies could be applied to a variety of our current and new products.
- Specific responsibilities for the initial designs
- Helping to work on RX system specifications
- Phase noise (analyzing/specifying)
- Selectivity (analyzing/specifying)
- Dynamic range (analyzing/specifying)
- RF VCO/synthesizer design
- Narrow-band high performance VCO design
- Wide-band, "adequate" performance design.
- Band-switched no-tweak design.
- Some work with the design/analysis of the synthesizer, trading off switching time and noise performance.
- Some work with the receiver chain
- Initial simple LNA design / evaluation
- Active mixer/IF filter design and evaluation at the prototype level.
- Some work on the Transmitter design
- Initial paper/simulated design of the discrete PA output stage for one band of interest
Newpoint-point radio project (LEDR II) (LEDR 900, LEDR 400, LEDR 1400) Summer 1998 through April 2000
- I served as the lead RF engineer/ RF architect on a family of digital point-point radios. The radios use QPSK, 16 QAM, and 32 QAM modulations to achieve high spectral efficiency and operate at data rates between 64 kbits/sec to 8192 kbits/sec on the 400, 900, and 1400 MHz bands. The complete transceiver has 1 Watt of output power and is on a single multi-layered circuit board. Spectral efficiencies in some channel bandwidths exceed 4 bits/second/Hz. In the spring of 2001, Microwave Data Systems received an order for greater than 15 Million dollars worth of these radios.
- Specific responsibilities
- All of the RF system level design for all three bands (some based on a previous product, much was new).
- RF system specifications for things such as synthesizer phase noise and PA linearity.
- Analysis, testing, and simulation of the transmitted spectrum for the purposes of ensuring FCC/ETSI mask compliance.
- Performed Electromagnetic simulation, analysis, and problem solving. This was required to work around some problems encountered with the size-constrained RF section.
- RF design/evaluation of
- Much of the low-level TX & RX circuitry: amplifiers, filters, diplexers, etc.
- Two out of the three LNA's.
- One UHF VCO
- All synthesizers
- Various low level circuits (TX/RX attenuators, active mixer interface circuits, power supply circuitry, PA bias circuit design)
- IF/AGC circuits (mostly reused from previous designs)
- Worked with two to four other engineers to spread out the work and get the job done efficiently while bringing several people up to speed on the required technology.
- Worked with others to prepare for ETS 300-630 certification of the 1400 MHz product, then personally accompanied the testing. The Radio type approval was granted.
- Helped with manufacturing support on the product line.
MDS400 Project ("LEDR I") (32 QAM / QPSK 2.048 Mb/sec digital point-point radio), spring-summer 1998
- I was responsible for the RF design of this radio, as such I maximized
reuse of circuitry from the MDS1400
- System design of the RX and TX
- Circuit design of most of the RX and TX
- Very quick turn-around -- this was a very short design cycle yet the first prototypes worked as expected... there were minimal design changes throughout the development.
MDS1400 Project ("LEDR I") (32 QAM / QPSK 2.048 Mb/sec digital point-point radio), 3/1996 - 12/1997
- Much of the system level planning, design, and evaluation
- RX design (my boss at the time designed most of the IF section)
- Selected most of the components
- Designed the LNA, diplexer, and selected MMIC amplifiers for many of the other necessary gain blocks
- TX design
- Designed the entire chain
- Designed a VCO used in one of the two stages of upconversion
- Designed upconverters based on active (IC) mixers.
- Designed the 100 mW/1W highly-linear PA, prototyped 1W/10W high-linearity power amplifiers.
- Designed stripline lowpass, directional coupler circuits
- Designed simple, effective PIN attenuator and GaAs FET bias circuits.
- Helped with the synthesizer design and performed most of the evaluation
- Wrote firmware that carried us for a few weeks when we were codeless with the initial prototypes in-hand.
- Wrote some software to quickly load the firmware into the radios (about 15 seconds tops) . This involved a PC application and an embedded application... the embedded application is used in the factory on a number of our products at this point in time.
- Wrote a Perl script to convert network analyzer data files (see Projects) into ".s2p" data files to help characterize and model active and passive microwave circuits and components.
- Worked with Test Engineering to come up with the best way to test the product.
- Wrote a "theory of operation" document to help others to understand the radio for future design and troubleshooting purposes.
SSE1/T1 project ( 1.544/2.048 Mb/sec DSSS point-point radio), 6/1995 - 3/1996
- 2.4 GHz, 1W upconverter module (1W GaAs FET PA, bias circuit, driver stages, mixer and filter lineup)
- 150 MHz (IF) transmit modulator assembly (I/Q modulator, PIN attenuator, IF level detector, doubler circuit)
- 2.4 GHz TX forward/reverse power detector module and lowpass filter.
- Low frequency VCO design for a "chipset synchronization" PLL.
- Doubler circuit used in the RX IF and TX IF sections.
- External charge pump designs for two PLL's in the system
- Some synthesizer design and evaluation (because I was interested, my boss at the time designed the synthesizer)
I like designing almost anything, but I find oscillators (VCO's mainly) most interesting and challenging. I am also fairly interested in other nonlinear microwave circuits such as multipliers, mixers, and higher-power amplifiers. I particularly like working with CAD/CAE tools on these so-called "tricky" circuits as it saves a ton of time at the bench. One can rarely provide a production ready design with only simulation, but the insight gained is extremely valuable. With the right tools and a little discipline, RF design can be an application of science rather than something that's "made to work" as many practitioners choose to treat it. I am far from perfect but I like to use some simple processes that easily catch many simple mistakes (who likes to make the same mistakes over and over again?).
- Technical leadership and adaptability
- Microwave/RF/Analog circuit & system design (with particular emphasis on signal sources, i.e. VCOs and synthesizers)
- Comfortable with standard DSP design including multi-rate filtering, DDS/NCO signal sources, and implementing digital equivalents of some simple standard analog filters (for instance I implemented digital de-emphasis/pre-emphasis on an FM voice radio system using the equivalent R-C filter models for a ham-radio project. This project also used polyphase filters (8x) for audio input and output to ease the processing burden for audio and keep the analog AAF simple. The digital squelch was operated at the higher rate.)
- RF communications system design, primary experiences with QAM, QPSK and Direct Sequence Spread Spectrum Systems, some experience with FM/FSK. Studied OFDM impairments, all on paper.
- Basic digital design (microcontroller/DSP bus interfacing, basic logic design)
- Proficient with Eagleware Genesys (linear, harmonic balance, electromagnetic, spectral-system), Sonnet, PSPICE, SysCalc, and MathCad, and Excel. Previous experience with HP/EESOF series IV, and some with ADS. Recent experience learning Octave (Matlab like). Competent with Ansoft HFSS, Ansoft Designer.
- Comfortable with a wide range of test equipment including spectrum analyzers, network analyzers, and vector signal analyzers. See the lab page to view the test equipment I actually own.
- Software skills (microcontrollers (HC11, HC705, 8051, Microchip PIC), DSPs (TMS320C2x, MC563xx), Perl, C, some C++, Visual C++ (including GPIB and other hardware interfacing mostly))
- Graduated with a BS/EE from Rensselaer Polytechnic Institute, Troy, NY in 1995.
- Short courses in the following areas during professional career:
- RF power amplifier design
- Oscillator design
- Digital Communications
- High efficiency Power amplifier design
- Design for manufacturing
- Triquint Foundry training (RFIC) (I'm not an RFIC designer, yet, I have just attended training to understand the basics of what it's all about).
- Two days of Ansoft HFSS training.
- Antenna design and analysis
- Design for Six Sigma techniques
- Graduate student at the Dick Frey Radio University (this is a joke, Dick is a good friend, ham buddy and "RF mentor" to me and many other radio nuts).
"Accurate Phase Noise Prediction in PLL synthesizers"
Part I, April 2000 and Part II, May 2000 in Applied Microwave & Wireless
This is a two-part article reviewing standard phase noise sources/analysis and bringing a strong emphasis to the contribution of resistors and op-amps to synthesizer phase noise. The second part of the article shows the comparison between predicted and measured phase noise for two different loop filters in a synthesized PLL source, showing the difference in performance that can happen with minor parameter changes. The techniques presented in the article are geared towards the very common "charge pump" phase detector based synthesizers, but the techniques could be adapted to a variety of different PLL architectures. The complete PLL analysis worksheets I've made available are here in MathCAD and PDF formats. There are many sources of PLL analysis literature available, however at the time this was published there didn't seem to be anything readily available for free that was this complete.
- RFdude.com Smith chart program a totally free RF Smith (TM) Chart utility for windows that can be found at Tools (along with some other widgets)
- "Simulating a discrete GaAs FET power amplifier" January/February 2003 Microwave Engineering Europe. Pardon the error in the schematic for the gate bias choke; the electrical model is correct but somehow the symbol was mistakenly set by me to look like a capacitor (years later nobody else seems to have noticed that, at least they didn't mention it to me!)
- Agilent webcast 1/2008: http://www.techonline.com/learning/webinar/204203418 Here I prepared a brief presentation that discussed practical RF design problems in a few areas. I provided several examples that I built and measured at RFdude.com LLC. It was a lot of material at a fairly high level in a short presentation -- but the slides can be downloaded from the archived version on the web.
- Agilent webcast 12/2013 on Planar microwave circuit tolerance analysis
- Some GPIB utilities for windows (click here to see more)
- Trace capture (for HP856x series spectrum analyzers)
- Signal generator sweeper (for a few generator types)
- "linearity tester", i.e. IP3 sweeper
- s-parameter extractor for HP8753 series network analyzers
- IEEE member (AP-S , CES, UFFC & MTT societies)
- Extra Class Amateur Radio License (WS2B) , ARRL member
- Former trustee Microwave Data Systems Amateur Radio Club (K2MDS)
- Historical roles/accomplishments: