The present invention relates to radio communications. More particularly, it relates to antennas in portable radio communication units that use spatial diversity reception to receive communication signals.

Portable and mobile radio communications create special problems which are not generally experienced in stationary communication systems. These problems are sometimes addressed by the use of spatial diversity reception techniques. This technique requires the use of two antennas which are preferably spatially separated by an electrically significant distance. Portable radio terminals, being designed to minimize their size, face an inherent difficulty in achieving the preferred spatial separation.

To overcome these and other limitations associated with existing portable radio units, new and improved antenna and processing means are needed.

The present invention provides improved reception of radio communication signals by portable radio terminals. In accordance with the present invention, a portable radio unit is provided that includes a housing that has a main section and a flip down housing section. The flip down housing section is rotatably mounted to the main section. A first antenna is connected to the main section and a second antenna is housed in the flip down housing section. In a preferred embodiment the second antenna has a first section extending along a first axis in the plane of the flip down housing section and a second section extending along a second axis in the plane of the flip down housing section. In a further preferred embodiment, the first axis and the second axis are orientated at an angle to each other, for example, at a 90° angle.

The portable radio unit also preferably includes processing circuitry, including first RF processing means, second RF processing means and signal analyzer means. The first RF processing means is connected to the first antenna for converting received communication signals to a first digital signal. The second RF processing means is connected to the second antenna for converting received communication signals to a second digital signal. The signal analyzer selects one ofthe two signals for further processing.

The invention will now be further described in connection with certain illustrated embodiments; however, it should be clear to those skilled in the art that various modifications, additions and subtractions can be made without departing from the spirit and scope of the

claims.

FIGS. 1 and 2 illustrate front and side views, respectively, of a portable radio terminal in accordance with a preferred embodiment ofthe present invention;

FIG. 3 illustrates a first antenna mounted in a first section of the housing of the portable radio terminal;

FIG. 4 illustrates a second antenna mounted in a flip down section of the housing of the portable radio terminal; and

FIG. 5 illustrates the processing circuitry of the portable radio terminal used to select one ofthe two signals received on the two antennas.

Referring to FIGS. 1 and 2, a portable radio terminal 10 is shown in accordance with a preferred embodiment of the present invention. The radio terminal 10 includes a housing 12. The housing 12 includes a main section 14 and a flip down housing section 16, which is shown in its open position. The flip down housing section 16 is preferably rotatably connected to the main section 14 via a hinge connector 18. The main section 14 of the housing 12 includes a keypad 20 and a display 22. When the radio terminal 10 is not in use, the flip down housing section 16 can be closed so as to cover the keypad 20.

The radio terminal 10 also includes a first antenna 24 and a second antenna 26. The first antenna 24 is preferably connected to the top ofthe main section 14 ofthe housing 12 in a conventional manner. The second antenna 26 is preferably housed in the flip down housing section 16. The second antenna 26 is preferably rubberized and is preferably molded directly into the flip down housing section 16 during construction.

The second antenna 26 can be shaped in any desired shape, the only constraint being the size of the flip down housing section 16 It is, however, preferred that a first section 28 of the second antenna 26 extend downward along a first axis in the plane ofthe flip down housing section 16 and that a second section 30 ofthe second antenna 26 extend along a second axis in the plane ofthe flip down housing section 16, such that the first axis 28 and the second axis 30 of the second antenna 26 are oriented at an angle to one another. In a preferred embodiment, the angle between the first axis 28 and the second axis 30 is 90°, so that the second antenna 26 is L-shaped.

FIG. 3 illustrates the mounting of the first antenna 24 in the main section 14 of the housing 16 of the radio terminal 10. As previously mentioned, the mounting is preferably accomplished in a conventional manner. The first antenna 24 is preferably constructed of

rubber and retractably mounted to an extension mount 32 The extension mount 32 has a channel 34 which allows the retraction of the first antenna 24 The first antenna 24 is preferably utilized to transmit and to receive signals The signals to and from the first antenna 24 are supplied from and to processing hardware via a coaxial cable 36

FIG 4 illustrates the mounting ofthe second antenna 26 in the flip down section 16 ofthe housing 12 The second antenna is preferably constructed from rubber and, as mentioned previously, is embedded in the flip down housing section 16 during the molded construction of the section 16 As stated previously, the second antenna 26 can be oriented in any desired fashion in the section 16, subject to the physical characteristics of the section 16, however, the preferred L-shaped orientation is illustrated in FIG 4 The second antenna 26 is preferably utilized to receive the same signals as the first antenna 24, i e. the antennas 24 and 26 are adapted to receive signals from the same frequency range It should be noted that the second antenna 26 could also be used to transmit communication signals, however, this is not the preferred arrangement As stated before, the preferred embodiment is to use the second antenna 26 as a spatially diverse receive antenna The signals from the second antenna 26 are supplied to processing circuitry via a coaxial cable 38

FIG 5 illustrates the processing circuitry 40 of the radio terminal 10 which is preferably located in the main section 14 of the radio terminal housing 12 The processing circuitry 40 includes a first RF front end 42, a second RF front end 44, a signal quality analyzer 46, a baseband signal processor 48 and a central controller 50

The signals received by the first antenna 24 are supplied, via the coaxial cable 36, to the first RF front end 42 The signals received by the second antenna 26 are supplied, via the coaxial cable 38, to the second RF front end 44 The radio signals received by the antennas 24 and 26 are processed by the RF front end circuitry 42 and 44, respectively, and digital signals representative of the received RF signals are provided to a signal quality analyzer 46 The analyzer 46 utilizes known techniques for measuring signal quality and/or strength or for estimating the quality of the communication channel over which the signals have been transmitted Based on the analysis, the best signal — either the signal from the first antenna 24 or the signal from the second antenna 26 — is selected for further processing The selected signal is supplied to the baseband processor 48 for the appropriate baseband processing The central controller 50 controls the operation ofthe analyzer 46 and the baseband processor 48 It is understood that changes may be made in the above description without departing

from the scope of the invention It is accordingly intended that all matter contained in the above description and in the drawings be interpreted as illustrative rather than limiting