Engineering & Science Technical Articles
(submitted by RF Cafe visitors)
you don't have to wait for a magazine to publish your technical article. If you would like to have your article
posted here, please attach it to an
e-mail in MS Word
format (I will convert it to PDF) or PDF format, along with a brief description to use with the listing.
Suggested topics include radar, electronic warfare, commercial wireless, aerospace, semiconductors, system design,
oscillators, amplifiers, filters, project management, component specification, testing, homeland security, defense
technology and simulation.
Many thanks to all the contributors here for sharing your knowledge with our visitors.
Articles listed here have been submitted by the original authors. Please direct any questions or comments to the
Measuring Peak and
with USB Power Sensors
by Orwill Hawkins, LadyBug Technologies
As technology and measuring techniques advance, the time
eventually comes when continuing to use old methods not only doesn't make sense, but can actually harm your
reputation by providing data that cannot be duplicated by customers who long ago adopted the new ways. Orwill
Hawkins, of LadyBug Technologies, has written a white paper describing how to make accurate, repeatable
peak and pulse power measurements on waveforms using the precision of modern instruments that provide a
graphical view of the entity being investigated. USB power meters provide an inexpensive means of obtaining
high quality measurements and the benefits of a graphical display environment (on your computer) at a relatively
low cost. I particularly like the use of the word 'mesial' in describing the midpoint of a pulse's rising
and falling edges.
Aeromodeler Dave Wineland
the Nobel Prize in Physics
As you might know if you have been an RF Cafe visitor for a while, my life-long hobby has been model
aviation. Many notable people have similarly been aeromodelers from a young age, including aircraft designer
Burt Rutan, Space Shuttle astronaut Robert "Hoot" Gibson, radio personality Paul Harvey, actor and WWII
bomber pilot Jimmy Stewart, Olympiad Bruce Jenner, catamaran and surfboard designer Hobart "Hobie" Alter,
to name a few. Physicist Dr. David
(Dave) Wineland has just been added to the list since he won the Nobel Prize in Physics in December
2012 for his work on quantum computing. The Academy of Model Aeronautics' (AMA) monthly magazine Model
Aviation printed an interview with Dr. Wineland in the January 2013 edition, where he discusses his
history with model airplanes and his work at the National Institute of Standards and Technology (NIST) in
Boulder, Colorado. Model Model Aviation editor Jay Smith granted permission for me to reprint the
article here on RF Cafe since it will likely be of interest to engineers and scientists who visit the website.
Reflect Forward Linearizer for Combined Amplifiers
By Ray Gutierrez, Micronda LLC
This paper is a continuation work for the “New
High Efficiency Intermodulation Cancellation Technique for Single Stage Amplifiers.” Published in January
2008 on RF Café’s Paper section. The paper describes configurations for dual and multiple parallel amplifiers
and uses the basic Reflect Forward technique for intermodulation cancellation. Some new improvements were
made to the RFAL technique to improve the efficiency and operation.
LED Lighting vs. Incandescent Lights
for Commercial Buildings
Short write-up on benefits of LED lighting.
SPURS Software Article
RF Design Magazine Software Contest Winner November 1992
I just ran across this magazine and
decided to scan the article. It is a great tutorial on mixer spurious product calculation - if I do say
so myself ;-)
Author: Cornell Drentea
Here is a short treatise on the history of radar development, beginning
in 1793 with Italian scientist Lazarro Spallanzani's experimentation on a bat's use of ultrasound for navigation,
on up through modern systems.
Efficiency Measurements of Portable-Handset Antennas Using the Wheeler Cap
Authors: Darioush Agahi, William Domino
In the design of wireless portable devices, antenna
efficiency is a variable that can have a great effect on overall system performance, and yet may not always
receive the attention it deserves. As an example, RF engineers must frequently make critical tradeoffs in
receiver design in order to improve sensitivity by mere fractions of a dB, but a poor antenna efficiency
can easily cause a degradation of several dB. This pitfall can occur in systems such as GSM, where many
tests are performed using a cable connection to the antenna port; a handset may easily pass such tests,
only to be later hampered by its antenna in the field. This paper is targeted at the very important parameter
of antenna efficiency, and a measurement technique that can be used to quantify it.
Claims in Radio
by Robert Horvitz
Abstract: Presented at the 1st COMMUNIA Workshop on "Technology and the Public
Domain," NEXA Center for Internet and Society, Politecnico di Torino, Italy, 18 January 2008.
early in the 20th century, national governments have asserted sovereignty over the electromagnetic spectrum.
These assertions were initially embraced as a way to control the monopolistic ambitions and offensive business
practices of the Marconi Wireless Telegraph Company. They are still the basis of radio regulation. However,
as wireless communication moves to higher and higher frequencies - into the range of infrared (heat) and
free space optics (light) - it is becoming obvious that claiming sovereignty over radio frequencies makes
no more sense than claiming sovereignty over colors of the rainbow. Is radio legally different from light?
If not, might we someday need government permission to use certain colors of light for certain purposes,
as with the invisible colors of radio?
GSM Handset Power
Amplifier Control Loop
Design An Analog Approach
Power amplifier control (PAC) for a Global System for Mobile communications© (GSM©) compatible radio
is one of the more challenging aspects of the GSM-based system design. Not only must the radio meet all
output radio frequency (RF) spectrum specifications, but the Power Amplifier (PA) control loop must also
be stable under varying environmental conditions. This paper starts by looking at the basic control theory,
and discusses its advantages over simple open loop control. It then moves on to describe each block of the
loop in detail. Stability is also discussed, and then finally, the paper examines a case study radio.
by Jason Millard & Darioush Agahi
New High Efficiency Intermodulation
Cancellation Technique for
Single Stage Amplifiers
By Ray Gutierrez, Micronda LLC
new design configuration that uses the basic concept of the RFAL distortion cancellation technique. Previously
published configurations using the RFAL uses two main amplifiers, the new configuration requires only one
single main amplifier and low level MMIC amplifiers in the Intermodulation Cancellation Loop.
basic RFAL technique uses the behavior of a transistor when driven into its non-linear operating region.
At the high drive level the input reflects not only the fundamental components of the input signal but also
the non-linear distortion components appearing at the output of the transistor. The level of the distortion
products at the input is sufficiently proportional to the output such that it can be used and processed
as a correction or error signal to cancel the output distortion of the transistor amplifier.
diagrams, schematics, data are included.
See follow-on work:
Reflect Forward Linearizer for Combined Amplifiers
in the Discrete Fourier
sampling is typically used with a DFT when testing analog to digital converters in the laboratory. A pure
sine wave test signal is generated at such a frequency that the input signal goes through a whole number
of cycles during the sampling period.
If the test signal is slightly off frequency, i.e. the input signal
doesn’t complete a whole number of cycles within the DFT time window, a distortion called spectral leakage
occurs. A small frequency error has little effect on the main signal, but has a strong effect on the DFT
The relationship between frequency error, and the signal to noise ratio due to leakage
noise has been established. This relationship can be used to determine the frequency resolution which the
sine wave generator must have in order to generate a sine wave at a sufficiently accurate frequency. A simple
calculator program is provided to evaluate the equations.
ADC Toolkit: Used with presentation
Greg Adams, with the permission of Lockheed Martin Company, NE&SS SS Math & Physics Seminar
The Study of Fast Adaptive Algorithms
and Introducing New Methods
for Increasing the Rate of Convergence
and Its Use in Smart Antennas
are introduced for increasing the rate of convergence in adaptive algorithms and new methods for selection
of m step-size are given. Special functions are introduced for
the definition of m which overturn current limitations and increase
the rate of convergence and decrease noise.
By S.Y. Skandari, Ch. Ghobadi, J. Nourinia, Urmia Univ.,
Rigorous Analytical Expressions
for the Effective Dielectric Constants
the Shielded Symmetrical Bandline
A set of accurate closed-forms formulas for the effective dielectric constants of the shielded symmetrical
By Dr. Nasreddine Benahmed, University of Tlemcen, Algeria
Software for Design NMR Probes Using
the Shielded Split Ring and the
Symmetrical Band Resonators
Design NMR probes using closed-forms formulas of the primary and secondary parameters of the shielded
split ring and the shielded symmetrical band resonators . These formulas are based on rigorous analysis
by finite element method (FEM) , method of moment (MoM) and curves fitting techniques.
By Dr. Nasreddine
Benahmed, University of Tlemcen, Algeria
In-Building RF Coverage Solutions
by Shekar Kulashekaran, firstname.lastname@example.org
This presentation offers a methodical approach to planning and implementing in-building solutions
for GSM 900 & 1800 MHz, and CDMA phone systems that helps solve the problem of coverage in offices,
garages, shopping centers, etc. Shekar has 6 years of experience planning and installing these systems.
Power Amplifier Linearization
Using Diode On Voltage
by Mrunal A. K. & Makarand Shirasgaonkar - MTech Students
Dr. R. M. Patrikar, Professor,
Visvesvaraya National Institute of Technology, Nagpur INDIA.
emphasizes on higher data rates and spectral efficiency has driven the industry towards linear modulation
techniques such as QPSK, 64 QAM, or multicarrier configurations. The result is a signal with a fluctuating
envelope which generates intermodulation (IM) distortion from the power amplifiers. This paper describes
a new approach of using a Diode as a predistorter in view of minimizing non linear distortion introduced
by the high power amplifier in microwave radio links.
Power Amplifier Design
4-Part Lecture Presentation
(contains much material from book)
by Andrei Grebennikov, M/A-COM Eurotec
Note: If you get sign-in screens,
just close the window and the file will load.
Lecture 1: Nonlinear Active Device Modeling
2: Impedance Matching
Lecture 3: PA Design Fundamentals
Lecture 4: High Efficiency Power Amplifier Design
Design and Development of Low Noise Amplifier
Using 3-dB Quadrature Hybrids
by Vandana Kalibhat Ramchandra
This paper describes and discusses a procedure of how to design
RF/Microwave Low noise amplifier with minimum noise figure and low VSWR. The initial data available is S-parameters
of the device. This paper references the RF design tool called ADS by Agilent technology.
Short Wire Antennas: A Simplified Approach
Part I: Scaling Arguments
Dr. Dan Dobkin veDr. Dan Dobkin version 1.0,
In this article we shall try to illustrate a simpler and more direct way
of understanding how short wire antennas, and by extension other small antennas, interact with traveling
electromagnetic waves, in which we focus on the potentials that result directly from charges and currents.
Part II will follow if sufficient interest is shown in this first installment.
Tutorial of Satellite Communication
by Kamran Ahmed, Institute of Information Technology, University of Sindh, Pakistan
This is an
excellent series of lectures on the basics of satellite communications.
▪ Overview of Satellite Systems
▪ Orbital Mechanics
▪ Orbital Perturbations
▪ Radio Wave Propagation
▪ Link Budget
▪ Channel Characteristics
On the Physical Meaning of the Curl Operator
by Christopher K. Horne
solving electromagnetic problems where the curl operator is evoked to compute the electric or magnetic fields,
one often forgets the curl has a physical meaning. The purpose of this article is to support the mathematics
of the curl with the physical meaning of its operation.
- See also: "Pulsed
S-parameter Measurements for GSM Amplifiers", MP Digest, June 2004
The Design of
Ultra Narrow-band Amplifiers using Small Signal Varactor Up-converters for ESM, ECM, ECCM, and ELINT Applications
by Dr. Alfred I. Grayzel, Dr. Ashok (Ash) K. Gorwara, Paul Kuhn Planar Monolithics Industries, Inc.
A method is presented in this paper for realizing tunable amplifiers with bandwidths of less than 0.5%;
without the use of superconductors and cryogenic cooling. This method uses a small signal varactor up-converter
to achieve these ultra narrow bandwidths. The equivalent circuit for the up-converter is presented as well
as the circuit configuration of the narrow band negative resistance amplifier. The design and experimental
results are presented for a 0.5% bandwidth negative resistance amplifier at 800 MHz; using this unique
circuit design. These devices and circuits can be used for electronic warfare applications such as surveillance,
electronic reconnaissance, jamming and frequency hopping.
Reflection / Transmission Power Measurements
by LadyBug Technologies
Obtaining accurate, reliable, and useful measurements of RF power in
the forward (transmission) and reverse (reflection) directions requires careful selection of test devices
and detection equipment. LadyBug Technologies has produced a white paper describing a method for performing
reflection and transmission measurements using a power sensor and a directional coupler. It includes a discussion
on coupler directivity and impedance match as a factor in measurement accuracy.
Measuring Semiconductor Device Input
Parameters with Vector Analysis
by Joe Cahak, Sunshine Design Services
This article will cover a recent test experience that
utilized some thinking about the test fixture, the bias requirements and the device mounting and special
calibration offsets needed to de-embed the test fixture response from the device response within the test
fixture. The device also had to have bias on several ports simultaneously. We had to establish a "reference
plane" within the fixture, from which we can use the Vector Network Analyzer's Port Extension or Phase Offset
to dial out the distance from our 1 port calibration reference plane to the point of short reference within
the fixture. With this phase offset compensation we can then measure the device capacitance of the part
within the fixture and the line length of the test fixture mostly worked out by the port extension.
Filter and RF SAW Filter
The purpose of this article is to discuss the important design considerations and development limitations
of a Radio Frequency and Surface Acoustic Wave (SAW) Filter (Both IF Filter and RF Filter). Each of the
major Electrical Parameters are discussed from a development perspective as follows (reference Figure 1
for further definition): We will also be reviewing RF Filter electrical components.
by Brian B. Donalson
This is a technical paper written to support newly trained satellite operators.
It helps in understanding how signals are received from orbiting satellites. Not too technical but if you
are someone who wanted to learn a little about satellite communications, this is a good start.
Understanding Standard Off-Set vs. Inverted [Satellite] Dishes
by Brian B. Donalson
This is technical paper written to support newly trained Satellite Operators.
It is a paper that shows the difference between a standard off-set satellite dish and an inverted off-set
Satellite dish. Technical in nature, but easy to understand. Complete with illustrations to help you understand.
A good read even if you know nothing about satellite dishes.
4G Technology - An Overview
A brief overview of the 4G system still in its planning and implementation (and definition) phase, provided
by the folks at Broadband Expert.
A Graphical Approach to
Mixer Spurious Analysis
by Kirt Blattenberger, RF Cafe
The Spur Web chart rapidly identifies both inband and out-of-band
spurs, affording a pictorial view of where conversion system frequencies lie with respect to all spur products.
(RF Digital-to-Analog Converter)
by Michael Hopkins, CurrentRF
breakthrough in Digital to Analog Conversion and breaching the Nyquist barrier, any output frequency is
now possible from low frequency digital data with the RFDAC. Achieve optimal baseband DAC noise and AC performance,
clearing the way for true 12, 14, and 16 bit performance at any output frequency.
Polynomial Model of Blocker Effects on Small Signal Gain and Noise Figure for LNA/Mixer Devices
Used in Wireless Receivers
In designing today’s wireless handset receivers, it is important to maximize both receive sensitivity
and resistance to undesired signals, also called “interferers”, or “blockers”. The starting place for receiver
design is the calculation of budgets for noise figure and linearity, usually facilitated by a spreadsheet.
While it is straightforward to find the cascaded noise figure (NF) and 1dB compression point (P1dB) using
a spreadsheet calculation, it is often not clear how to use these to predict the actual performance of the
receiver in the presence of a large blocker. To obtain a reasonably accurate prediction may instead require
an inconvenient co-simulation of the system with circuit models embedded. However, a simpler approach is
possible, which is still performed at the level of cascade calculations rather than simulation.
William Domino, Nooshin Vakilian, & Darioush Agahi
The staff at IMS ExpertServices™
has prepared a few articles on the subject of expert witnesses.
Monolithic Ceramic Block
Combline Bandpass Filters
Small size and ruggedness are two important factors in the selection of bandpass filters for military
and OEM applications. Monolithic ceramic block combline bandpass filters not only offer a size advantage
in UHF through L-band frequencies; they also have other characteristics that make them extremely attractive
when compared to other technologies. The filters are characteristically lower in cost and have relatively
good insertion loss due to their high Q material (Q>10,000). This paper describes the design technique
used for ceramic bandpass filters.
By Darioush Agahi, Sykworks
CAD Oriented Study of Polyimide Interface
Layer on Silicon Substrate for RF Applications
Polyimide interface layer on standard silicon substrate extends the use of silicon for RF applications and
is also compatible with the present CMOS technology. This paper investigates the characteristics of the
microstrip lines patterned on polyimide interface layer up to 40 GHz. The limitation of lossy silicon substrate
can be overcome by this approach. The full wave analysis of the microstrip line has been carried out using
CAD tool. Also the non-ideal ground plane effects along with the concept of thicker bottom metallization
below polyimide have been demonstrated to have lower losses.
Kamaljeet Singh & K Nagachenchaiah Semiconductor Laboratory (SCL), SAS Nagar, Near Chandigarh, India-160071
Coupled Microstrip Filters:
for Improved Characteristics
This paper presents improved characteristics of the hairpin filter topology. Standard hairpin configuration
has the drawback of broader bandwidth, more insertion loss along with poor skirt rate. This paper demonstrates
the approach to overcome the limitation inherent in hairpin as well as suppression of the harmonic which
is prominent in the microstrip coupled filter topology.
Kamaljeet Singh, R. Ramasubramanian, S. Pal Communication Systems Group, ISRO Satellite Center, Bangalore,
Short Wire Antennas: A Simplified Approach
Dr. Dan Dobkin version 1.0
Note: If you get sign-in screens, just close
the window and the file will load.
Part I: Scaling Arguments
How does a wire dipole antenna work?
How do we find the resistance
the reactance vanish at an
appropriate length or frequency?
Part II: Detailed Estimates of Scattered Voltage
We will now fill in the details of the calculation
of scattered current and voltage for a short
length of wire with
an impinging potential
this article we shall try to illustrate a simpler and more direct way of understanding how short wire antennas,
and by extension other small antennas, interact with traveling electromagnetic waves, in which we focus
on the potentials that result directly from charges and currents.
"I will offer a $5 Starbucks gift certificate for each algebraic goof
reported and corrected."
Smith Chart™ for Excel™
by Kirt Blattenberger, RF Cafe
This Excel workbook demonstrates how easy it is to implement
a Smith Chart using only a standard x-y scatter chart and coordinate conversions.
Load Network Design Techniques for Class E
RF and Microwave Amplifier
by Andrei Grebennikov, M/A-COM Eurotec
The output network of a class E amplifier must provide impedance
matching at the fundamental frequency and adequate rejection of harmonic frequencies, while handling DC
power to the device.
First-Time-Right Design of RF/Microwave
Using Only S-Parameters
by Ivan Boshnakov (email@example.com), Senior Principal Engineer, Aerial Facilities Limited (www.aerialfacilities.com)
This article describes and discusses a procedure of how to design RF/Microwave Class A power amplifiers
in a very efficient and highly accurate manner when the only initial data available are the S-parameters
of the transistors. This paper references the "Tandem RF Software Programs Streamline the Design of
Power Amplifiers" item by Mr. Boshnakov toward the bottom of this page.
Maxwell's Primer (see
series of links below)
by Glen Dash
This tutorial series is graciously provided by Dr. Dash: Part
1: An Introduction
Difference a Del Makes
Even a Computer Can Love
From a Small Wire Element
Method of Moments
These articles provide a magnificently comprehendible presentation of Maxwell's
Equations. They originally appeared in Conformity magazine in 1999, and were pulled a couple years ago.
All six parts have been revised and condensed into a much small file size to facilitate
easier downloads (as of November 15, 2005). Glen Dash is the author of numerous papers on the laws
and standards applicable to electronic equipment. He is a graduate of MIT in Electrical Engineering and
holds a law degree from Harvard. Please send a note of thanks to
Dash for making these immensely popular articles available.
Automatic Telephone Call Indication Device
Using Power Line
by Manu V Thayyil and Prince V Thachil, Model Engineering College, Thrikkakra, Kochi, India
paper describes the design of an automatic telephone call indication device with power line as the channel
for communication via Amplitude Shift Keying. These guys are graduate students and welcome feedback -
Tandem RF Software Programs Streamline
the Design of Power Amplifiers
by Ivan Boshnakov and Jon Divall, Aerial Facilities Ltd., U.K.
This article describes a procedure
for the design and development of power amplifiers using harmonic-balanced software in tandem with impedance
matching network synthesis software. For this purpose a particular design problem will be discussed.
The Noble Art of De-Coupling
by Carl Lodstrom
Tricks of the trade for successful use of capacitors for decoupling.
Criss-Cross RFAL Cancels
the IMD Distortion in Amplifiers
article provides a new design configuration that uses the basic concept of the RFAL (Reflect Forward Adaptive
Linearizer) distortion cancellation technique.
The basic RFAL technique uses the behavior of a transistor
when driven into its non-linear operating region. At the high drive level the input reflects not only the
fundamental components of the input signal but also the non-linear distortion components appearing at the
output of the transistor. The level of the distortion products at the input is sufficiently proportional
to the output such that it can be used and processed as a correction or error signal to cancel the output
distortion of the transistor amplifier. Author: Ray Gutierrez, Micronda LLC.