wireless transreceivers

with the wireless industry striving to offer customers better connectivity and functionality. Users are promised ubiquitous wireless access to digital voice, the Internet, and many other sources of information. In order to incorporate in a small form-factor the different modes of access required to achieve ubiquitous connections between users and service providers adopting different radio technologies, future PCS devices are expected to be highly integrated and multi-standard in nature [1]. In fact, according to the IMT-2000 specifications, the next generation “phones”, or information appliances, potentially need to be compatible with up to five disparate radio standards for high-speed data access. In addition, “accessory” radios such as GPS and Bluetooth may also be incorporated for location sensing and short-range cable replacement. One approach to providing multi-standard connectivity would be to simply incorporate independent transceivers for each standard targeted. However, traditional transceiver designs rely heavily on multiple semiconductor technologies and discrete components, and by incorporating multiple transceivers, this situation is compounded and becomes cumbersome with the multiplicity of components needed. It is clear that for multi-standard transceivers to be practical, higher levels of integration will be necessary.

Current transceiver solutions often use low cost CMOS for digital and baseband circuitry, while reserving silicon bipolar or GaAs for critical RF circuits. While this is good for optimizing the performance of individual subsystems, it is costly and makes full transceiver integration very difficult. Discrete passive components commonly used in today’s transceivers (e.g. SAW filters and high-Q resonators) enable excellent filtering and ease generation of spectral pure signals, but they are often bulky and expensive. In addition, while the fixed frequency characteristics of these components are ideal for single-standard transceivers, they are inflexible and generally not as well suited for systems requiring multi-standard adaptation.

1 Response

  1. Guru June 13, 2010 / 5:28 am

    Wireless Receiver A wireless system consists of two main components: a transmitter, and a receiver. The responsibility of the wireless receiver is to pick up the radio signal broadcast by the transmitter and change it back into an audio signal. Wireless receivers are available in two different configurations. Single antenna receivers utilize one receiving antenna and one tuner, similar to an FM radio. Diversity receivers, or dual antenna systems, often provide better wireless microphone performance. A diversity receiver utilizes two separate antennas spaced a short distance apart and (usually) two separate tuners. An “intelligent” circuit in the receiver automatically selects the better of the two signals, or in some cases a blend of both. Since one of the antennas will almost certainly be receiving a clean signal at any given moment, the chances of a dropout occurring are reduced. There are actually several distinctions among dual antenna systems (diversity, true diversity, etc.) that are variations on the same theme.

    Wireless Transmitter
    A wireless system consists of two main components: a transmitter, and a receiver. The transmitter handles the conversion of the audio signal into a radio signal and broadcasts it as a radio wave via an antenna. The antenna may stick out from the bottom of the transmitter or it may be concealed inside. The strength of the radio signal is limited by government regulations. The distance that the signal can effectively travel ranges from 100 feet to over 1,000 feet, depending on conditions and quality of signal. Transmitters are available in two basic types. One type, called a “body-pack” or “belt-pack” transmitter, is a small box about the same size as a pack of playing cards (or smaller in some cases). The transmitter clips to the user’s belt or may be worn on the body. For instrument applications, a body-pack transmitter is often clipped to a guitar strap or attached directly to an instrument such as a trumpet or saxophone. In the case of a handheld wireless microphone, the transmitter is built into the handle of the microphone, resulting in a wireless mic that is only slightly larger than a standard wired microphone. Usually, a variety of microphone elements or “heads” are available for handheld wireless microphones. All wireless transmitters require a battery (usually a 9-volt alkaline type) to operate.

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