We occasionally publish Technical Articles that talk about techniques that are used in the products that we develop. These articles introduce the basic ideas behind these technologies without going into the mathematics behind them.
This paper is a review of some of the basics of Electrically Small Antennas. An electrically small antenna is generally defined by its largest dimension being less than one sixth to one tenth of a wavelength.
The critical design parameters are feedpoint impedance bandwidth, radiation efficiency and antenna “smallness”.
With the explosive growth of satellite-based services, the ability to receive or transmit a tight beam of circularly polarized radiation while minimizing unwanted radiation is imperative to maintaining good communication.
For such demanding applications, the axial-mode quadrifilar helical antenna provides a high performance and robust antenna platform both in space as well as on the ground. Furthermore, for portable and handheld radio systems, the quadrifilar helical antenna can be readily miniaturized, providing good quality circular polarization and near hemispherical coverage in the UHF and microwave bands. This article was published in the RF Globalnet Newsletter of March 17, 2015.
This article explores the basic concepts of patch antennas. We use a simple rectangular, half wave long, probe-fed patch operating in its fundamental mode as an example. Topics include principles of operation, impedance matching, radiation pattern, circular polarization, bandwidth, efficiency, alternative feed types, stacked patches and higher mode behavior.
This article was originally published in September 2005. After it was published, we received substantial feedback from those who read it. The article has been revised based upon the feedback we received and this updated version was published in the RF Globalnet Newsletter of September 2009.
This article, originally published in RF Globalnet’s 2008 Annual RF & Microwave Solutions Update, provides an overview of the general properties of GPS antennas and briefly compares three common types. It gives you a basic understanding of how GPS antennas work and what level of performance is required for specific applications. Another version of this article was published in the February 1, 2009 issue of GPS World.
In some instances, single-element antennas are unable to meet the gain or radiation pattern requirements of a particular application, such as satellite communications or point-to-point telecommunications. One possible solution to this problem is to combine several single antenna elements into an antenna array.
This article will introduce the basic concepts of antenna array theory, without delving into the mathematics behind it.
This article focuses on a qualitative review of the Class A, B, AB and C “limited conduction angle” amplifier modes as well as giving some explanation on where inefficiencies appear in each.
Some of the advantages and disadvantages of each topology will be presented and the trade-offs will be briefly elaborated in an intuitive manner, through the use of computer simulation.
This article was originally published as the featured article in the February 2011 issue of the RF Globalnet Newsletter.
The so-called “switching” amplifiers like Class-D, E, F and inverse F are briefly reviewed in this article.
These amplifiers are based on the notion of limiting the dissipation in the active device during its resistive “turn-on” and turn-off” times and in doing so, improving the efficiency over that of the classical “linear” amplifier classes. Again, computer simulation of the basic circuit topologies is used give the reader an intuitive feel for how these amplifiers work.
This article was originally published as the featured article in the June 2011 issue of the RF Globalnet Newsletter.
Here, we review the behavior of the Class-AB and Class-C amplifiers and then take a detailed look at how these two amplifier types can be combined to produce the Doherty amplifier, a system that preserves signal fidelity as well as boosts efficiency.
The fact that two inherently non-linear amplifiers can be combined to produce an amplifier with a linear response is an amazing result of Doherty’s 1936 invention. Despite its “antiquity”, the Doherty amplifier has become indispensable in today’s digital wireless revolution.
This article was originally published as the featured article in the August 2011 issue of the RF Globalnet Newsletter.
This paper is a review of some of the basics of phase locked oscillators and the mechanics of “Cycle Slipping” in low carrier-to-noise environments.
We explore the concept of Allan deviation as a measure of phase error in situations where phase locking is not always guaranteed.
We also propose an improved version of the heterodyne method for measuring the Allan deviation of a phase-locked oscillator for use in characterizing the performance of a deep-space coherent transponder prototype.