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 by Bree Engineering
The following article is a brief introduction to and explanation of the theory and
application of the named frequency selective devices. A Bias-T is frequency dependent
just as much so as a band splitter or diplexer; it differentiates between DC (0 Hz)
and the RF frequency. Bree Engineering Corporation was founded in 1999 and is a manufacturer
of custom electronic filters, multiplexers, filter banks and other related types of components
in the frequency range of 0.1 MHz to 40 GHz. Designs include Chebychev, Bessel,
Butterworth, Gaussian, transitional, elliptic-function and pseudo-elliptic-function filters
in lumped element, cavity, combline, interdigital ...
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.
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.
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.
Short write-up on benefits of LED lighting.
by Kirt Blattenberger, RF Cafe
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 ;-)
by 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.
by Darioush Agahi and 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.
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.
Since 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?
by Jason Millard and Darioush Agahi
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 Ray Gutierrez, Micronda LLC
 A 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.
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.
Block diagrams, schematics, data are included.
See follow-on work: Reflect Forward Linearizer for Combined Amplifiers
by
Greg Adams, with the permission of Lockheed Martin Company, NE&SS
SS Math & Physics Seminar
 Synchronous
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 noise floor.
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
by S.Y. Skandari, Ch. Ghobadi, J. Nourinia, Urmia Univ., Urmia, Iran
Algorithms
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 Dr. Nasreddine Benahmed, University of Tlemcen, Algeria
A set of accurate closed-forms formulas for the effective dielectric constants of
the shielded symmetrical bandline.
by Dr. Nasreddine Benahmed, University of Tlemcen, Algeria
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 Shekar Kulashekaran, shekar.pk@gmail.com
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.
by Mrunal A. K. & Makarand Shirasgaonkar - MTech Students, Dr. R. M. Patrikar,
Professor, Visvesvaraya National Institute of Technology, Nagpur INDIA.
The 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.
 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
Lecture 2: Impedance Matching
Lecture 3: PA Design Fundamentals
Lecture 4: High Efficiency Power Amplifier Design
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.
by Dr. Dan Dobkin veDr. Dan Dobkin version 1.0,
enigmatics@batnet.com
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.
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
▪ Polarization
▪ Antennas
▪ Link Budget
▪ Interference
▪ Channel Characteristics
by Christopher K. Horne
In 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
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by Ed Troy, Aerospace Consulting, LLC
Almost everyone uses simulation tools for designing RF, microwave, and high speed
digital circuits today. It is essential. But, very few engineers use those same tools
for troubleshooting of circuits that are not working correctly. It amazes me that many
engineers and technicians still spend days tuning, tweaking, and adjusting RF circuits
that do not work properly on the bench. They could probably find, and fix, the problems
in much less time by firing up their simulation software. It is much faster to change
values, both known and speculated, in a simulation engine than it is to make the same
changes on the test bench.
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.
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.
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.
by John Lai, Oscilent Corporation
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.
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.
A brief overview of the 4G system still in its planning and implementation (and definition)
phase, provided by the folks at Broadband Expert.
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.
by Michael Hopkins, CurrentRF
A 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.
by William Domino, Nooshin Vakilian, and Darioush Agahi
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.
The staff at IMS ExpertServices™
has prepared a few articles on the subject of expert witnesses.
by Darioush Agahi, Sykworks
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
Kamaljeet Singh and K Nagachenchaiah Semiconductor Laboratory (SCL),
SAS Nagar, Near Chandigarh, India
Abstract:
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.
by
Kamaljeet Singh, R. Ramasubramanian, S. Pal Communication Systems Group,
ISRO Satellite Center, Bangalore, India
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.
by 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 and the
reactance?
Why does the reactance vanish at an
appropriate
length or frequency?
Part II: Detailed Estimates of Scattered Voltage
and Current
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
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.
CHALLENGE
"I will offer a $5 Starbucks gift certificate for each algebraic goof reported and
corrected."
dan@enigmatic-consulting.com
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.
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.
by Ivan Boshnakov (ivanb@aerial.co.uk), 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.
by Glen Dash
This tutorial series is graciously provided by Dr. Dash: Part
1: An
Introduction
Part
2: Why
Things Radiate
Part
3: The Difference a Del Makes
Part
4: Equations
Even a Computer Can Love
Part
5: Radiation
From a Small Wire Element
Part
6: The
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
Dr. Dash for making these immensely popular articles available.
by Manu V Thayyil and Prince V Thachil, Model Engineering College, Thrikkakra, Kochi,
India
This 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 -
manuthayyil@yahoo.co.in
by Carl Lodstrom
Tricks of the trade for successful use of capacitors for decoupling.
This 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.
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Now 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.
