Subsystems and Systems

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Radar has been used for observation of weather since the 1940s. 1 Advances in weather radar include the incorporation of Doppler capability, which allows measurement of wind velocity, and the use of multiple polarizations, which enhance rainfall estimation and provide the ability to discriminate between types of hydrometeors, such...

The number of mobile users is predicted to reach 1.7 billion by the year 2010. More than 45 percent of them will use high data speed services. W-CDMA, proposed by IMT2000, has become the most practical and important system for the development of new wireless communications. Nevertheless, second generation...

Atmospheric propagation attenuation is known to be higher in the 2.1 GHz band than in the cellular band. Thus, to overcome this performance disadvantage and to maximize cell coverage and capacity, Unity Wireless System's first feedforward multi-carrier linear power amplifier (MCLPA) product has been designed with a high 60...

There are many ways of characterizing W-CDMA transmitter performance. However, the Third Generation Partnership Project (3GPP) specifications require two measurements to verify the in-channel modulation quality of W-CDMA transmitters - error vector magnitude (EVM) and peak code domain power (peak CDE). This article explores the purpose behind these key...

The prime requirements of a handheld spectrum analyzer are for it to be lightweight, compact, but with as large a display as possible, and exhibit low power consumption - all within a sturdy housing. These criteria are not easy to fulfill in themselves, so it is an even greater...

With the continually increasing complexity of digital modulation techniques employed in wireless and satellite communications systems, instruments that accurately generate and maintain a set level of bit energy-to-noise density ratio (E b /N o ) have become valued tools in optimizing bit-error rate (BER) performance. These instruments have been...

The transmitter unit, contained in base stations for third generation cellular systems, requires a linear power amplifier to preserve signal integrity when amplifying composite signals associated with multiple channels. While the power amplifier must meet a number of requirements to be system level compliant, the design process generally emphasizes...

Test applications that require microwave power from 1 to 18 GHz are usually addressed by two amplifiers, a solid-state unit to cover the low frequency range and a traveling-wave tube amplifier (TWTA) for the higher range. The input signal must be switched between the two amplifiers and, if there...

Noise is a limiting factor for sensitive reception. In recent communication receivers, noise, along with many external factors, including intermodulation, reciprocal mixing and spurious response, may disturb the sensitive reception of the desired signal. Thus, much consideration for the noise and other factors that disturb the signal reception and...

Electromechanical distribution systems (switch matrices) are used in both commercial applications and military systems. Computer control of these switch matrices facilitates their use in automated testing and in those systems requiring remote control of switching functions. The newest product in Dow-Key's line of electromechanical switches is a single-pole 12-throw...