Diversity for mobile terminals

• US 6,049,705 A
• Filed: 02/03/1998
• Issued: 04/11/2000
• Est. Priority Date: 02/03/1998
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Xue, Hongxi
• Primary Examiner(s): Hunter, Daniel S.
• Assistant Examiner(s): WYCHE, MYRON
• Application Number:
  US09/017,882
• Time in Patent Office: 798 Days
• Field of Search: 455/562, 455/277.1, 455/277.2, 455/273, 455/278.1, 455/272
• US Class Current: 455/277.1
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity

Abstract

Polarization diversity is achieved in mobile terminals with three antennas. Each of the three antennas are orthogonal to one another. With three orthogonal antennas, the mobile terminal increases the likelihood that at least one antenna'"'"'s polarity will match that of the incoming signal'"'"'s wavefront, regardless of how the user orients the mobile terminal. Once a signal has been received by each of the three antennas, they can be selected or combined using a variety of techniques and/or algorithms. Among these techniques are selection diversity, switching selection diversity, fixed combining diversity, and adaptive combining diversity (e.g., maximal ratio combining and interference rejection combining).

Claims

1. A mobile terminal utilizing polarization diversity, said mobile terminal comprising:

a first group of antennas, said first group of antennas including at least a first, a second, and a third antenna operatively connected to a receiver; and

selecting circuitry for selecting between said first antenna, said second antenna and said third antenna to select an antenna that substantially matches a wave polarization of an incoming signal, said selecting circuitry selecting a default antenna among said first, second and third antenna, said selecting circuitry detecting when a received signal on said default antenna drops below a first predetermined threshold and switching to a secondary antenna when said received signal drops below said first predetermined threshold, said selecting circuitry switching from said secondary antenna to said default antenna when said signal level is above a second predetermined level.

2. The mobile terminal of claim 1, wherein:

said first, said second, and said third antennas are approximately orthogonal to one another.

3. A mobile terminal utilizing polarization diversity, said mobile terminal comprising:

a first group of antennas including a first and a second antenna operatively connected to a receiver circuitry;

a second group of antennas including a third and a fourth antenna operating connected to said receiver circuitry;

first combining circuitry for co-phasing and combining received signals from said first set of antennas to provide a first composite signal;

second combining circuitry for a co-phasing and combining received signals from said second set of antennas to provide a second composite signal; and

selecting circuitry for receiving said first composite signal and said second composite signal, said selecting circuitry selecting the stronger combined and co-phased signal and providing the selected composite signal to a receiver circuit.

4. The mobile terminal of claim 3, wherein:

said first and said second antennas are approximately orthogonal to one another.

5. The mobile terminal of claim 3 wherein said first combining circuitry co-phases signals from said first and second antenna at ninety degrees, said second combining circuitry co-phases signal from said third and fourth antenna at ninety degrees.

6. A method of receiving signals at a mobile terminal utilizing polarization diversity, said method comprising the steps of:

receiving an incoming signal at a first group of antennas which includes a first antenna, a second antenna and a third antenna, said first, second, and third antennas being substantially orthogonal to each other, said first group of antennas being adapted to be operatively connected to a receiver;

selecting a default antenna from among the first, second, and third antennas;

determining whether an incoming signal strength of said incoming signal is below a first predetermined level;

switching to a secondary antenna from among said first, second, and third antennas if said incoming signal strength is below said first predetermined level;

switching from said secondary antenna to said default antenna if said incoming signal strength rises above a second predetermined level; and

switching from said secondary antenna to a second secondary antenna if said incoming signal strength is below a third predetermined level.

7. The method of claim 6, wherein said step of selecting further comprises the steps of:

adjusting a gain for each of said first, second, and third antennas to equalize an average SNR for each of said first, second, and third antennas; and

selecting among said first, second, and third antennas an antenna with the highest average SNR.