ForewordRadiofrequency (RF) electronics is a special branch of electronics that deals with the study and design of devices and systems in which the physical effects of high frequency play an important role. RF has applications in vast areas of engineering and science including wireless telecommunications, radar, manufacturing, plasma heating, plasma processing of materials, radio astronomy, magnetic resonance imaging and many more. Radiofrequency signals are electromagnetic oscillations that cover a wide range of frequencies. The use of radiofrequency spectrum is similar from country to country however there are many local differences. To learn about details relevant to Australia go to the Australian Communications and Media Authority (ACMA) website. In the USA the Federal Communications Communication is the equivalent authority (FCC). On a worldwide basis radio communications is governed by the International Telecommuncations Union (ITU). The following table describes the RF spectrum, its nomenclature, frequency ranges and some applications. The table specifies electromagnetic waves according to both frequency (f) and wavelength (λ), where the two are related by fλ = c, where c is the speed of light = 299,793 km/s. Some of the applications suggested have occurred largely for historical reasons whilst others have a physical basis. Some examples: The FM radio band used to be down at 50 MHz but political effects in the USA around WWII led to it being transferred to the 100 Mhz band where it is today. Electromagnetic waves do not propagate inside conductors such as sea water. Hence radio communications with submarines is essentially impossble. The long wavelengths indicated in the table are necesssary to maximise the limited depths of penetration of RF in sea water. Radio Astronomy research can be carried out in any frequency range but the weakness of the signals detected means that it needs specially assigned allocations in order to avoid interference from man made RF devices. For example the MOST in Hoskingstown, Bungendore is a UHF radiotelescope array. It operates on 867 MHz: right in the middle of the mobile phone band. Another relevant phenonemon is the high data rates that we have grown accustomed to in wireless communications. Physical requirements limit operation of these to the UHF and microwave bands where enough spectrum has been allocated. The patchy and largely historical narrowband assignments of the HF and VHF bands make high speed wireless impossible. The range of allowed frequencies varies between countries. Radio frequency spectrum
Amateur radio frequenciesA very interesting set of special radiofrequency assignments are the amateur radio bands. These are shown in the following table. To a slight degree, even they differ from country to country. For example, technically in Australia, the 50 - 54 MHz is assigned to amateur radio and is partially "shared" with TV channel 0. Of course these services cannot operate in the same area at the same time! The HF band (1 - 30 MHz) is valid internationally due to the important physical effect of "skip" that makes it so popular. Skip results from the ionosphere which is a cloud of tenuous plasma (ionised gas) that envelopes the earth starting at an altitude of about 50 kms. Radiowaves below about 30 MHz are reflected back to earth from the ionosphere. The most important effect that this has is to the practice of DX-ing, wherein amateurs the world over communicate by voice over Single Side Band (SSB). Obviously skip is a weather and time dependent effect and multiple reflections of a HF signal between the earth and the ionosphere may be necessary for successful communications over thousands of kms. A corollary of this is that the highly dispersive nature of the ionosphere makes the "skip channel" one of the wireless world's most challenging for data communications. Skip is not the only way that amateurs communicate over long distances. VHF and C band satellites such the "Amateur Oscar" operate on amateur bands. Satellites are major international undertakings as you may appreciate. However if you're really keen to do long range comms and satellite is too expensive or the ionosphere too inclement, then you could always try "moon bounce communications"!
Amateur radio is a hobby for the fun loving and technically minded and RF practice is one of their main skills: especially in Australia. The amateur radio bands are also used for reliable communications of data and voice in situations of national emergency. Amateurs even have their own wireless data communications standards: Packet Radio, which is a Wide Area Networking (WAN) technology that operates independently of other lines of national communications such as the telephone infrastructure. To become a "Ham" you need to sit for an exam and obtain a licence to operate. This is easier now that Morse Code has been abolished as a prerequisite. Citizen Band RadioFor voice communications using low power devices (5 Watts) it is not necessary to obtain a licence for operation. The (once popular) CB radios operating in the HF and UHF bands exist and are class licenced. The most disappointing thing about CB is that digital communications is strictly forbidden! This renders CB useless for any practical purpose in regional areas where most public communications digital services are substandard. 27 MHz CB radios operate on the following standard 40 channels:
UHF CB radios operate on the following standard 40 channels:
Microwave Frequency Designations
Properties of RadiofrequencyThe essential properties of radiofrequency that distinguish it are the following:
The Special Nature of Radiofrequency ElectronicsWhat makes radiofrequency electronics special is the way that it challenges conventional electronics circuit notions. Radiofrequency circuits differ from their low frequency counterparts in a number of ways:
The Radiofrequency CourseWe will be looking at radiofrequency design using a mixture of fundamental physics and practical design techniques. Essentially all of the relevant fundamental aspects of electromagnetism are introduced in the first four lectures. This fundamental material is then fleshed out and applications are introduced in this web material. The material will be put into practice in the context of a VHF and a UHF radiofrequency transceiver design project which will form the radiofrequency front end of an IQ transceiver. InstructionsThe course has at least 20 lectures in all. The web based material serves the purpose of a brick of background material including some assessible exercises that either entail computational or lab based exercises. These quizzes must be attempted. Students should pursue the web based material individually and ask questions in tutorials. The project can be performed from day one as new information comes to light. In the early stages, students can practice using the PCB CAD software. Parts will be made available for the construction project. For the time being, the project can take place in the Ian Ross seminar room 103 during office hours, however extra availability of this lab may be made later on. All radiofrequency diagnostic instrumentation should remain in this lab. AssessmentThe assessment for the course will be based on 40% final exam, 40% project and 20% Exercises. The final exam will be based predominantly on the theoretical lecture material although some questions on practical scenarios can be expected. For the project each student should obtain both a scrap book and a log book. In the scrap book students should keep note of the full day to day progress during the design of the wireless transceiver. Every idea and measurement goes in the scrap book. The scrap book should be complete, not too crowded (if possible) and dated but will probably be messy (though this is not my advice). Entries should be in pen. Liquid paper is forbidden. Errors should be at most traced so that correct but misjudged thoughts can be reconstituted. The scrap book is an aid to logical thinking and is a necessary aspect of good scientific practice. The log book on the hand should contain a complete description of circuit details, layouts, tests and measurements, summarising the scrap book and providing a sound basis for the final report (<30 pages). The log book is intended to cement the findings in a readable and not too verbose form (so you at least think twice about your reasoning on any given subject). I must be able to read and understand the log book clearly as a demonstration of your ability as an engineer to communicate and clearly express your findings. For assessment purposes I require both the final report and the log books/scrap books. A midterm progress report of two page length is due on April 23 (this is not assessable but just gives me an idea of your progress and understanding). The final project report is due on May 31. I may also randomly inspect and date the scrap books and log books to make sure that satisfactory work is being performed and that the log books track the scrap books. In addition, your understanding of the practical and theoretical material will be assessed by your reponses to the questions on the web. This work is to be performed in a separate lab book. These exercises will be done in the laboratory sessions and your spare time. Present the lab book to me at the end of term (circa May 31) for marking. I may also make random inspections of the lab book throughout the semester to make sure that you are keeping up. The lab material will probably be the subject of most of your questions and therefore learning. We can deal with this in tutes as well as any questions you may have about the lectures ENGN4545 Transceiver Project The following folder contains information about the project including support material. Files for download COURSE MATERIAL
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