Cellular communications systems continue to grow in popularity and have become an integral part of both personal and business communications. Cellular phones allow users to place and receive voice calls most anywhere they travel. Cellular phones and other handheld wireless communication devices typically include a radio, e.g. having a wireless transceiver and associated circuitry connected thereto, and an antenna connected to the radio.
Antenna noise temperature has been discussed in many books and papers, such as John D. Kraus and Ronald J. Marhefka, “Antennas: For all Applications”, McGraw Hill, 2002, ch. 12; Constantine A. Balanis, “Antenna Theory: Analysis and Design” John Wiley & Sons Inc. 1997, ch. 2; David M. Pozar, “Microwave Engineering”, Addison-Wesley Publishing Company, 1993, ch. 12; J. Dijk, MJeuken and E. J. Maanders, “Antenna noise temperature”, Proc. IEEE, Vol. 115, No. 10, October 1968, pp 1403-1409; and Warren L. Flock and Ernest K. Smith, “Natural Radio Noise—a Mini-Review”, IEEE Trans. on AP Vol. Ap-32, No. 7, July 1984 pp 762-767.
The definitions for antenna noise temperature are mainly given based on remote sensing and satellite receiving applications, where antennas are generally physically away or well shielded from radio receivers and high gain antennas are used to capture weak signals. In this case the total noise at the terminal of the receiver antenna is mainly contributed from thermal noise and background noise. In contrast, a wireless handheld antenna is physically very close to its receiver so that the printed circuit board and accessories operate as a part of the antenna. This makes the noise contributions to the handheld wireless device antenna different from the noise contributions to antennas for remote sensing and satellite receiving applications.
This difference makes the standard antenna temperature definition inadequate for explaining the receiver behavior of handheld wireless devices in a noisy environment. A wireless handheld device generally operates in an ever changing noise environment, and the handheld antenna radiation pattern is generally a broad beam antenna pattern. Furthermore, human physical interface and device usage scenarios change constantly in the practical application. For these reasons, antenna noise temperature is constantly changing in the practical sense.