Communications: radio wave antennas – Antennas – With radio cabinet
Patent
1996-04-25
1998-06-23
Le, Hoanganh T.
Communications: radio wave antennas
Antennas
With radio cabinet
343893, H01Q 124, H01Q 2106
Patent
active
057710228
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The invention comprises an antenna particularly for a hand held or portable communications terminal.
BACKGROUND
In mobile communications, the radio link is usually non-line-of-sight. The information-bearing radio waves travelling between the terminals undergo multiple path propagation. The result is short-term signal fading, caused by wave interference, combined with long-term fading caused by "shadowing" of the waves by objects of several-wavelength dimension, such as people, trees, buildings, and hills, etc. The short-term fading occurs on average every half-wavelength, which, for example, at the newly allocated personal mobile communications frequencies of 1.5 to 1.7 GHz, is about every 10 cm. The short-term fading of the signal envelope is approximately Rayleigh-distributed. The long-term fading occurs over several wavelengths and is approximately log-normal distributed. The fading impairs the capacity, or quality, of the communications channel.
A well known technique to mitigate the effects of fading is by using antenna diversity with a signal combiner.
A well known form of diversity antenna is space diversity, in which similar elements are spaced apart by a half-wavelength or more.
Further, for hand held terminals, up to two antenna elements can be configured using polarization diversity. The polarization diverse antenna requires a monopole antenna and a collocated loop antenna--i.e., the loop is located around the monopole.
The idea of diversity antennas is to receive "uncorrelated signals". For the Rayleigh distributed short term fading, this can be taken to mean that "the envelopes should have short-term cross correlation coefficients of less than 0.7".
SUMMARY OF INVENTION
The present invention provides an antenna particularly suitable for a hand held or portable communications terminal.
In broad terms the invention may be said to comprise a composite antenna comprising at least two individual antennas spaced from each other at less than 0.3 wavelengths relative to the frequency to be received, on a hand held or portable communications terminal.
Preferably a composite antenna of the invention comprises multiple antennas which are spaced as closely as 0.2 or 0.15 wavelengths from each other or even less than 0.1 wavelengths, in two or more separate arrays. The individual antennas may be spaced as closely as 0.06 wavelengths for a two element array and 0.07 wavelengths for a three or more element array, relative to the frequencies to be received. The individual antennas may be regularly or irregularly spaced from each other.
Most preferably a composite antenna of the invention consists of two or more arrays of individual closely spaced antennas, with each array comprising two, three, four, five or more individual antennas.
The frequencies to be received i.e, for which the composite antenna of the invention is designed, may be any portable communications frequencies such as cellular telephone communication frequency bands, frequency bands that may be utilized for communicating between computers on a wireless network or the like. Typically the composite antenna will be designed to comprise a number of individual antennas closely spaced for frequencies in the 800 MHz to 5 GHz range, and particularly the 1.5 to 1.7 GHz range and also at about 2.7 GHz, these being international frequencies for personal communications.
Preferably each of the individual antennas making up the composite antenna comprises a monopole, but it is also possible for each of the antennas to comprise a folded monopole, a slot or loop antenna element, a patch element, a printed element or any other type of antenna type.
Preferably each of the antennas is between 0.1 and 0.7 wavelengths long relative to the received frequencies, and most preferably about 1/4 wavelength long.
Preferably the individual antennas or at least some of the antennas are spaced from each other in the direction of orientation of the individual antennas to assist in each individual antenna receiving a signal as uncorrelated as possibl
REFERENCES:
patent: 4396920 (1983-08-01), Grimberg et al.
patent: 4494120 (1985-01-01), Garay
Scott Neil
Vaughan Rodney
Industrial Research Limited
Le Hoanganh T.
LandOfFree
Composite antenna for hand held or portable communications does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composite antenna for hand held or portable communications, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composite antenna for hand held or portable communications will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1397707