Blogs de Ingeniería Electrónica y Telecomunicaciones
The Integrated Circuit
It seems that the integrated circuit was destined to be invented. Two separate inventors, unaware of each other's activities, invented almost identical integrated circuits or ICs at nearly the same time.
Why the Integrated Circuit Was Needed
In designing a complex electronic machine like a computer it was always necessary to increase the number of components involved in order to make technical advances. The monolithic (formed from a single crystal) integrated circuit placed the previously separated transistors, resistors, capacitors and all the connecting wiring onto a single crystal (or 'chip') made of semiconductor material.
The amplifying device (electron tube, transistor, magnetic amplifier, etc.) itself will have frequency limitations and respond in different ways as the frequency changes. Capacitors and inductors in the circuit will change their reactance as the frequency changes. Even the slight amounts of capacitance and inductance between the circuit wiring and other components (interelectrode capacitance and self-inductance) can become significant at high frequencies. Since the response of components varies with the frequency, the components of an amplifier are selected to amplify a certain range or band of frequencies
Airborne radars present unique design challenges, mainly in the severe nature of the ground echo received by the radar and in the installation constraints on the size of the radar. The peculiar clutter situation governs the nature of the signal processing, and the installation limitations influence the antenna design and the radio frequency to be used (the two being strongly related) as well as the packaging of the rest of the radar. Similar considerations influence the design of space-based radars as well.
A particularly valuable use of airborne radar is weather assessment. Radars generally operating in the C or X bands (around 6 GHz or around 10 GHz, respectively) permit both penetration of heavy precipitation, required for determining the extent of thunderstorms, and sufficient reflection from less intense precipitation. See also Meteorological radar; Radar meteorology.
Another basic and valuable airborne radar function is altimetry. The aircraft's altitude can be continuously measured, using (generally) C-band frequencies (around 6 GHz), low-power transmission, and a downward-oriented antenna beam. Sometimes, information from additional beams (looking somewhat forward, for example) is combined with measurements of the Doppler shift of the ground echo received to further aid in navigation. Another type of radar used in navigation is the radar beacon, in which a ground-based receiver detects an interrogation pulse from the aircraft and sends back a so-called reply on a different frequency, to which the receiver on the aircraft is tuned. See also Air-traffic control; Altimeter; Doppler effect; Surveillance radar.
Airborne radars are used effectively to provide high-resolution mapping of Earth's (or other planetary) surface, with a technique called synthetic aperture radar (SAR). The processing uses the fact that surface objects produce a Doppler shift (due to the aircraft's flight) unique to their position as the aircraft passes by; this Doppler history is indicative of the scatterer's lateral, or cross-range, position at the particular range determined by the usual echo timing. With very stable radars and well-measured flight characteristics (and other focusing methods), picture cells (pixels) of 1 ft × 1 ft (0.3 m × 0.3 m) can be formed in the processed images from radars tens or hundreds of miles away. The resolution is somewhat like that possible had the flight path itself been used as a huge antenna, the synthetic aperture.
It wasn't too long ago that wireless communication was only available using devices designed solely for that purpose; walkie-talkies and the like. But over the last few years, wireless communication has found its way into all manner of products. Today, providing the ability for a product to communicate via Wi-Fi, gsm or other rf technologies is almost expected. What might once have been pretty much a digital design is now more complex – and the tools needed to design and test these products have had to adapt to new demands.
1-10 of 52