Radio Frequency Transistors: Principles And Pra...
B EE 554 Planar RF and Microwave Engineering I: Passive Circuits and Networks (5)Provides a project-based radio frequency (RF) and microwave engineering approach that allows students to design, build, and test various passive RF and microwave circuits on planar printed circuit boards (PCB's) and ceramic substrates. Transmission line theory and Smith charts are used along with network analysis techniques for designing planar passive RF and microwave circuits. Student designs will be tested on a vector network analyzer.View course details in MyPlan: B EE 554
Radio Frequency Transistors: Principles and Pra...
Transistors are also used for low-frequency, high-power applications, such as power-supply inverters that convert alternating current into direct current. Additionally, transistors are used in high-frequency applications, such as the oscillator circuits used to generate radio signals.
Alternating current is so named because its direction (polarity) changes (alternates). This type of current is similar to that which comes from electrical wall outlets. The rapidity with which the direction of current flow changes per unit of time is referred to as frequency, and is measured in Hertz (Hz). One complete cycle per second is one Hz. If a current alters polarity one million times per second, it is a one megahertz (MHz) current. Electrosurgical generators typically operate at frequencies between 400,000 Hz and 2.5 MHz, although some generators produce currents with frequencies as high as 3.5 MHz. Because these frequencies fall in the range of radio waves, electrosurgical generators are sometimes called radio frequency generators, and do, in fact, produce radio waves as a byproduct. Either excessively high or low frequencies can cause undesirable effects. Depolarization of susceptible tissues ceases at frequencies above 10,000 Hz. Excessively high frequencies tend to encourage current leakage.
To understand electrosurgery, it must be clear that the effects obtained are the result of heat. This heat may be derived from an external source and transmitted to tissue by conductance (cautery), or, as in the case of both laser and electrosurgery, be produced within the tissue by an external source of energy. Due to the rapid changes in the direction (polarity) of current flow with the use of high frequency alternating current, there is no net transfer of electrons, and likewise, no movement of ions across cell membranes (depolarization). Part of the heat generated is from the tissue's impedance (resistance to current flow), but the majority of heat stems from the rapid vibration of molecules within the tissue under the effect of the changing electromagnetic field. That there is no essential difference in the effect of heat produced by any method was demonstrated by Lounsberry and associates,1 who were unable to detect any difference in tissue effect between cutting and coagulating currents of the same amperage, applied over the same area and for the same duration. Indeed, lesions produced by a soldering iron (cautery) were similar to electrical lesions. These findings were confirmed by Zervas and Kuwayama2 who found that lesions produced in rat brain and liver by induction heating, radio frequency electrocoagulation, and direct application of heat were similar for similar degrees of temperature elevation. The only application in which there may be a difference in both mechanism and effect is cutting with electrical current.
Even though the reason for the use of radiofrequency current (as opposed to low frequency current) is to avoid stimulation of excitable tissues, particularly nervous tissue and muscle, we have all noted localized contractions when attempting to cut muscle or to coagulate bleeding points on it. This paradox is explained by the observation that, as the duration of the stimulus is decreased (i.e., increasing the frequency of the current), stimulation can still be obtained by increasing the strength (current density) of the stimulus. Thus, high frequency current will cause localized muscle contraction where the current density is high, but generalized muscle contraction will be avoided as the current disperses away from the treatment electrode and the current density drops.
Although most modern cardiac pacemakers are resistant to interference by extraneous electromagnetic signals, several incidences of asystole and cardiac arrest have been reported when electrosurgery is used in patients with pacemakers.31 These problems occur predominantly in patients with older demand pacers. In these units, the electrosurgical signal may block the pacer's inhibition amplifier allowing an R-on-T phenomenon to occur, leading to ventricular fibrillation. Aside from the special case of the cardiac pacemaker patient, with the use of radio frequency currents, cardiac arrhythmia due to discharge from an ESU should be an almost nonexistent event.
Brief review of the semiconductor devices principles, including two terminal and three terminal devices: PN diodes, Tunneling Diodes, MOSFETs, Tunneling Diodes, Bipolar Junction Transistors, high frequency electronics like S parameters will be introduced. High frequency electronic devices principles will be discussed. Material transfer process, Lithography, metal deposition, atomic layer deposition, will be demonstrated. The full fabrication process of making MOSFET using III-V materials on insulator will be instructed and conducted. Students gets hands-on experience on advanced device design and fabrication technology.
Modern telecommunications and datacom systems operate at frequencies in the radio frequency (RF) and microwave range. The basic concepts and technologies required to design RF and microwave devices and circuits are explained. Examples of applications to wireless and lightwave systems are discussed.
This certificate provides training for design, installation, and maintenance of any type of wired or wireless communication system such as remote monitoring, radio frequency (RF) control, radio and television transmitters, public safety and government communication equipment, and fiber optic systems.
This course covers advanced analog and digital electronic communications including digital two-way radio, cellular, microwave, satellite, and broadcast communications. Topics include digital radio frequency theory, digital transmitters and receivers, P25 digital radio, antennas, software-defined radios, and related industry test equipment. Field trips may be required.
Advanced topics in design of analog and communications integrated circuits. Topics include: implementation of passive components in integrated circuits; overview of frequency response of amplifiers, bandwidth estimation techniques, high-frequency amplifier design; design of radio-frequency oscillators.
Abstract:Radio Frequency Identification (RFID) sensors, integrating the features of Wireless Information and Power Transfer (WIPT), object identification and energy efficient sensing capabilities, have been considered a new paradigm of sensing and communication for the futuristic information systems. RFID sensor tags featuring contactless sensing, wireless information transfer, wireless powered, light weight, non-line-of-sight transmission, flexible and pasteable are a critical enabling technology for future Internet-of-Things (IoT) applications, such as manufacturing, logistics, healthcare, agriculture and food. They have attracted numerous research efforts due to their innovative potential in the various application fields. However, there has been a gap between the in-lab investigations and the practical IoT application scenarios, which has motivated this survey of this research to identify the promising enabling techniques and the underlying challenges. This study aims to provide an exhaustive review on the state-of-art RFID sensor technologies from the system implementation perspective by focusing on the fundamental RF energy harvesting theories, the recent technical progresses and commercial solutions, innovative applications and some RFID sensor based IoT solutions, identify the underlying technological challenges at the time being, and give the future research trends and promising application fields in the rich sensing applications of the forthcoming IoT era.Keywords: radio frequency energy harvesting; radio frequency identification (RFID); RFID sensor; inductive coupling; backscattering
Often, radios can be fixed simply by looking for the sort of problems common to all electronic gadgets, with very little idea of how they actually work. But when that approach fails, it's necessary to have a basic grounding in the theory of operation in order to go deeper. This page aims to provide that grounding, describing the several types and their principles of operation.
A crystal set is the simplest practical type of radio, and demonstrates some of the basic principles, except that it provides no amplification, relying entirely on the energy delivered by the aerial. The diagram shows a very simple crystal set.
In fact, if you mix two frequencies f1 and f2, you get not only f1 - f2 but also f1 + f2. This means that there would be a second frequency that would be converted to the same IF frequency and possibly cause interference. To avoid this there is normally a single tuned circuit and stage of amplification to filter out any such "ghost" stations before the mixer. This tuned circuit has to track the local oscillator frequency, but that's still easier than tracking several more tuned circuits as a TRF radio would have to.
In a reasonably modern receiver with push-button tuning (such as a car radio), a digital circuit replaces the local oscillator. This generates a precise frequency derived digitally from an accurate quartz crystal oscillator.
Radio waves (and light) travel at 300 million metres per second. So if you were to count 300 million radio waves passing you per second (i.e. they have a frequency of 300MHz) then each peak must be racing past you just a metre behind the previous one. This is the wavelength - the distance between successive peaks (or troughs). 041b061a72