GB2353673A

GB2353673A - Diversity control apparatus

Info

Publication number: GB2353673A
Application number: GB0014835A
Authority: GB
Inventors: Katsuya Nagashima
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 1999-06-16
Filing date: 2000-06-16
Publication date: 2001-02-28
Anticipated expiration: 2020-06-16
Also published as: GB0014835D0; GB2353673B; JP3389153B2; AU4089000A; AU761935B2; JP2000357983A

Abstract

A diversity control technique for use in a diversity receiver having an antenna selection diversity mode and a diversity combining mode is disclosed. A signal strength detector detects a received signal strength from a received signal. A fading pitch detector detects a fading pitch from the received signal strength. A quality detector detects a received signal quality based on the received signal. One of the antenna selection diversity mode and the diversity combining mode is selected depending on whether at least one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated. In the case of the antenna selection diversity mode, a radio receiving system other than a normally used radio receiving system is powered off.

Description

2353673 DIVERSITY CONTROL APPARATUS AND METHOD The present invention

relates to diversity techniques and, more specifically, to a diversity control technique for use in a mobile communication device such as a cellular telephone.

There have been proposed several diversity techniques in order to achieve high-quality signal transmission even in radio communications on fading channels.

In Japanese Patent Application Unexamined Publication No. 7-15380, a diversity circuit allowing stable receiving characteristics and reduced power consumption is disclosed. This conventional diversity circuit is provided with an antenna selector, two receiving detection circuits, a fading-pitch detector, and a diversity-combining controller. In the case of a large fading pitch, two antennas are concurrently connected to the receiving detection circuits, respectively. Two received signals are detected by the receiving detection circuits and the detected signals are combined by the dive rsity-combi ni ng controller. Contrarily, in the case of a small fading pitch, one of the two receiving detection circuits are set to a power-saving mode and the other receiving detection circuit is used to detect a received signal by a selected one of the antennas.

In Japanese Patent Application Unexamined Publication No. 60- 2 100840, a diversity receiver allowing improved quality of communication and power consumption is disclosed. More specifically, this diversity receiver is provided with a fading-oc.Currence frequency detector. When a detected fading occurrence frequency is greater than a predetermined value, an antenna diversity system is used. When a detected fading occurrence frequency is smaller than the predetermined value, an after-detection diversity selection or combining system is used.

An object of the present invention is to provide a diversity control apparatus and method allowing stable receiving characteristics and easy reconnection of a previous channel.

Another object of the present invention is to provide a diversity control apparatus and method allowing reduced power consumption.

According to the present invention, a diversity control apparatus for use in a radio communication device having an antenna selection diversity mode and a diversity combining mode, includes a signal strength detector for detecting a received signal strength from a received signal, a fading pitch detector for detecting a fading pitch from the received signal strength, a quality detector for detecting a received signal quality based on the received signal, and a diversity mode selector for selecting one of the antenna selection diversity mode and the diversity combining mode depending on whether at least one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated.

According to another aspect of the present invention, a diversity receiver includes a plurality of antennas, a first radio receiving system for 3 receiving a radio-frequency signal to produce first received data, at least one second radio receiving system connected to a corresponding antenna of the plurality of antennas to produce second received data, a first switch for selecting one of radio-frequency signals which are each received at the plurality of antennas and outputting a selected radio-frequency signal to the first radio receiving system, a combiner for combining the first received data and the second received data to produce combined received data, a second switch for selecting one of the first received data and the combined received data, a demodulator for demodulating a selected received data input from the second switch to produce received data and quality data of the selected received data, a signal strength detector for detecting a received signal strength based on radio-frequency signals received at the plurality of antennas, a fading pitch detector for detecting a fading pitch from the received signal strength, a memory for storing threshold values each corresponding to the received signal strength, the fading pitch, and the received signal quality, a power-supply controller for powering off the at least one second radio receiving system and the combiner when the diversity receiver is in a power-on state, and a diversity controller for controlling the first and second switches and the power-supply controller such that one of an antenna selection diversity mode and a diversity combining mode is selected depending on whether at least one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated.

When the antenna selection diversity mode is selected, a combination of the at least one second radio receiver system and the combiner is 4 preferably powered off and the second switch selects the first received data.

When the diversity combining mode is selected, preferably, the combination of the at least one second radio receiving system and the combiner is powered on, the first switch selects a radio-frequency signal received at a predetermined antenna, and the second switch selects the combined received data.

The signal strength detector may detect a maximum signal strength from signal strengths of the radio-frequency signals received at the plurality of antennas to produce the maximum signal strength as the received signal strength.

The signal strength detector may detect an averaged signal strength of signal strengths of the radio-frequency signals received at the plurality of antennas to produce the averaged signal strength as the received signal strength.

The first switch may be incorporated in the first radio receiving system.

The diversity controller may compare each of the received signal strength, the fading pitch, and the received signal quality with a corresponding threshold value stored in the memory to determine whether at least one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated. Further, the diversity controller may update the threshold values based on determination results which were performed by the diversity controller.

According to the present invention, a diversity control method for a radio communication device having an antenna selection diversity mode and a diversity combining mode, includes the steps of detecting a received signal strength from a received signal, detecting a fading pitch from the received signal strength, detecting a received signal quality based on the received signal, and selecting one of the antenna selection diversity mode and the diversity combining mode depending on whether at least one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated.

According to the present invention, a diversity control method for use in a diversity receiver including a plurality of antennas, a first radio receiving system for receiving a radio-frequency signal to produce first received data, and at least one second radio receiving system connected to a corresponding antenna of the plurality of antennas to produce second received data, includes the steps of:

a) selecting one of the radio-frequency signals which are each received at the plurality of antennas and outputting a selected radio-frequency signal to the first radio receiving system, b) combining the first received data and the second received data to produce combined received data, C) selecting one of the first received data and the combined received data, d) demodulating a selected received data input from the second switch to produce received data and quality data of the selected received data, 6 e) detecting a received signal strength based on radio-frequency signals received at the plurality of antennas, f) detecting a fading pitch from the received signal strength, g) storing threshold values each corresponding to the received signal strength, the fading pitch, and the received signal quality, h) powering off the at least one second radio receiving system and the combiner when the diversity receiver is in a power-on state; and i) controlling the first and second switches and the power-supply controller such that one of an antenna selection diversity mode and a diversity combining mode is selected depending on whether atleast one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated.

As described above, the received signal quality, the received electricfield level, and the fading pitch are used to determine which one of the antenna selection diversity and the diversity combining should be selected. Therefore, radio conditions can be monitored from three viewpoints (received signal quality, signal strength, and fading pitch), resulting in precise diversity switching decisions.

Further, since the deterioration of radio conditions can be detected early, the receiving characteristics can be made stable and the channel disconnection can be prevented. Therefore, when a hand-over operation fails to be made, the previous channel can be easily obtained again.

7 Further, the hand-over operation can be started early and completed smoothly.

Furthermore, since the at least one second radio receiving system is powered off during the antenna selection diversity, the power consumption is dramatically reduced.

Arrangements illustrative of the invention will now be described, by way of example, with reference to Figs. 1 to 3 of the accompanying drawings.

In the drawings:

Fig. 1 is a block diagram showing a diversity control apparatus of a mobile telephone according to an embodiment of the present invention, Fig. 2 is a block diagram showing a diversity control apparatus according to another embodiment of the present invention, and Fig. 3 is a block diagram showing an example of a radio receiving system for use in the embodiments.

Referring to Fig. 1, a mobile telephone is provided with two antennas 101 and 102, which are connected to a radio-frequency (RF) switch 103.

The RF switch 103 selects one of the antennas 101 and 102 depending on a diversity control signal SID and outputs a radio signal received at a selected antenna to a radio receiving circuit 104. The antenna 102 is also connected to a radio receiving circuit 105. Each of the radio receiving circuits 104 and is provided with a frequency converter and other necessary circuit components.

The respective outputs of the radio receiving circuits 104 and 105 are 8 connected to the inputs of phase detectors 106 and 107. The output of the phase detector 106 is connected to one input of a combiner 108 and one input of a logic switch 109. The output of the phase detector 107 is connected to the other input of the combiner 108.

The combiner 108 combines the outputs of the phase detectors 106 and 107 to output a combined phase signal to the logic switch when the diversity combining is selected. The logic switch 109 selects one of the outputs of the phase detector 106 and the combiner 108 depending on the diversity control signal SID. A selected one is output to a demodulator 110.

The demodulator 110 demodulates; received data from a detected phase value that is received from a selected one of the phase detector 106 and the combiner 108 through the logic switch 109. The demodulator 110 further detects a received signal quality Q by monitoring the degree of a phase deviation from an ideal phase or a transmitted phase.

The outputs of the radio receiving circuits 104 and 105 are connected to the inputs of a received signal strength processor 111. The received signal strength processor 111 detects an electric-field intensity of each of the respective output signals of the radio receiving circuits 104 and 105 and performs processing thereof determined depending on the diversity control signal SID, which will be described later. The received signal strength processor 111 outputs a received electric-field level RSS to a fading pitch detector 112 and a diversity controller 114.

The fadi ng pitch detector 112 detects a fadi ng pitch FP f ro rn the received electric-field level RSS. A fading pitch FP can be obtained from a

9 change in the received electric-field level RSS in time slots assigned to the mobile telephone.

A memory 113 stores threshold values, which are used to determine whether deterioration of radio conditions occurs, which will be described later. Preferably, the diversity controller 114 may update these threshold values based on accumulated diversity decision results.

The diversity controller 114 inputs the received signal quality Q from the demodulator 110, the received electric-field level RSS from the received signal strength processor 111, and the fading pitch 112 from the fading pitch detector 112. The diversity controller 114 uses the threshold values stored in the memory 113 to determine whether deterioration of radio conditions occurs. When it is determined that the radio condition has been deteriorated, the diversity controller 114 sets the diversity control signal SID at a diversity combining state. This causes the receiving mode of the mobile telephone to be changed into diversity combining. When it is determined that the radio condition has been restored, the diversity controller 114 sets the diversity control signal SID at an antenna selection diversity state. This causes the receiving mode of the mobile telephone to be changed into antenna selection diversity.

The diversity control signal SID is output to the logic switch 109, the received signal strength processor 111, the RF switch 103, and a power supply controller 115. The power-supply controller 115 supplies power to all the circuit components of the mobile telephone. Further, the power-supply controller 115 controls the power-on/off of the radio receiving circuit 105, the phase detector 107, and the combiner 108. As described later, in the case of the diversity combining, the power-supply controller 115 powers on the radio receiving circuit 105, the phase detector 107, and the combiner 108.

In the case of the antenna selection diversity, the power-supply controller 115 powers off the radio receiving circuit 105, the phase detector 107, and the combiner 108.

An operation of the diversity control apparatus as shown in Fig. 1 will be described hereafter.

The received signal strength processor 111 inputs the respective received signals from the radio receiving circuits 104 and 105 and detects the respective electric-field strengths thereof.

In the case of the antenna selection diversity, as described before, the radio receiving circuit 105 is powered off. Therefore, the received signal strength processor 111 outputs the electric-field strength of a signal input from the radio receiving circuit 104.

In the case of the diversity combining, the received signal strength processor 111 performs appropriate processing determined depending on the specification of the combiner 108. For example, the received signal strength processor 111 detects a maximum one from the electric-field strengths of the received signals input from the radio receiving circuits 104 and 105 and outputs it as a received electric-field level RSS to the fading pitch detector 112 and the diversity controller 114. As another example, the received signal strength processor 111 detects an average of the electric field strengths of the received signals input from the radio receiving circuits

11 104 and 105 and outputs it as a received electric-field level RSS to the fading pitch detector 112 and the diversity controller 114.

The fading pitch detector 112 detects a fading pitch FP from the received electric-field level RSS and outputs it to the diversity controller 114.

The diversity controller 114 compares the received signal quality 0, the received electric-field level RSS, and the fading pitch FP to a quality threshold, an electric-field level threshold, and a fading pitch threshold respectively. These threshold values are stored in the memory 113.

The diversity controller 114 is preferably implemented with software running on a program-controlled processor. The software processing allows the degree of freedom in diversity decision to be increased. For example, a time-average value, a count-average value, and an instantaneous value can be easily obtained from each of the received signal quality 0, the received electric-field level RSS, and the fading pitch FP.

When the received signal quality 0 is lower than the quality threshold, when the received electric-field level RSS is lower than the electricfield level threshold, or when the fading pitch FP is greater than the fading pitch threshold, the diversity controller 114 determines that deterioration of radio conditions occurs.

In other words, when at least one of the received signal quality Q, the received electric-field level RSS, and the fading pitch FP has been deteriorated, the diversity controller 114 controls the diversity control signal SD so as to set the RF switch 103, the power-supply controller 115, and the logic switch 109 to the diversity combining. More specifically, the RF switch 12 103 is switched so as to connect the antenna 101 to the radio receiving circuit 104. The power-supply controller 115 powers all the circuit components on. The logic switch 109 is switched so as to connect the output of the combiner 108 to the demodulator 110.

Thereafter, when all of the received signal quality 0, the received electric-field level RSS, and the fading pitch FP have satisfied the thresholds, respectively, in other words, when the radio condition has been restored, the diversity controller 114 controls the diversity control signal SID so as to set the RF switch 103, the power-supply controller 115, and the logic switch 109 to the antenna selection diversity. More specifically, the RF switch 103 is switched into an antenna selection mode in which a better one of the antennas 101 and 102 is connected to the radio receiving circuit 104.

The power-supply controller 115 powers off the radio receiving circuit 105, the phase detector 107, and the combiner 108. The logic switch 109 is switched so as to connect the output of the phase detector 106 to the demodulator 110.

According to the embodiment, the received signal quality 0, the received electric-field level RSS, and the fading pitch Fl? are used to determine which one of the antenna selection diversity and the diversity combining should be selected. Therefore, radio conditions can be monitored from a plurality of viewpoints (here, three viewpoints), resulting in precise diversity switching decision. Further, since the deterioration of radio conditions can be detected early, if hand-over operation failed to be made, then the previous channel can be easily obtained again. Further, since the 13 channel disconnection to a base station is prevented, the hand-over operation can be started early and completed smoothly.

Further, only one RF switch 103 is needed and is connected to a normally used receiving system composed of the radio receiving circuit 104 and the phase detector 106. The other receiving system composed of the RF switch 105, the phase detector 107, and the combiner 108 is powered off during the antenna selection diversity. Therefore, in the case of the antenna selection diversity, the power consumption is dramatically reduced and only the normally used receiving system outputs a received phase value to the demodulator 110 through the logic switch 109 selecting the phase detector 106.

Referring to Fig. 2, a diversity control apparatus according to another embodiment of the present invention has three receiving branches which is formed by adding one or more branches composed of an antenna 201, a radio receiving circuit 202, and a phase detector 203 to the two-branch circuit configuration of Fig. 1. In this case, a received signal strength processor 204 detects an electdc-field intensity of each of the respective output signals of the radio receiving circuits 104, 105, and 202. Since the basic operation of the received signal strength processor 204 is the same as the received signal strength processor 111, the details thereof are omitted. Similarly, a combiner 205 combines the outputs of the phase detectors 106, 107, and 203 to output a combined phase signal to the logic switch when the diversity combining is selected. Since the basic operation of the combiner 205 is the same as the combiner 108, the details thereof are 14 omitted. In the similar manner, four or more receiving branches may be employed.

Alternatively, a plurality of antennas and a single receiving system may be provided. In this case, radio-frequency signals received at the antennas are analog-combined and the combined signal can be used to produce a signal quality 0, a received electric-field level RSS, and a fading pitch FP.

Referring to Fig. 3, a RF switch for antenna selection diversity may be provided within a radio receiving system. More specifically, the radio receiving system is composed of a (normally used) radio receiving circuit 301 and a radio receiving circuit 302. The radio receiving circuit 301 is composed of a bandpass filter 11, a RF amplifier 12, a RF switch 13, a mixer 14, and a bandpass filter 15. The radio receiving circuit 302 is composed of a bandpass filter 21, a RF amplifier 22, a mixer 234, and a bandpass filter 24.

A radio signal received at the antenna 101 passes through the bandpass fitter 11 before being amplified by the RF amplifier 12. A radio signal received at the antenna 102 passes through the bandpass filter 21 before being amplified by the RF amplifier 22. The respective radio- frequency (RF) signals amplified by the RF amplifiers 12 and 22 are input to two input terminals of the RF switch 13. The RF sWitch 13 is controlled by the diversity control signal SD received from the diversity controller 114 as in the case of the RF switch 103. As described before, the radio receiving circuit 302 is powered off during the antenna selection diversity.

A selected RIF signal by the RIF switch 12 is converted to an intermediate-frequency (IF) signal by the mixer 14 mixing it with a local oscillation signal LO. Similarly, the RF signal amplified by the RF amplifier 22 is converted into an intermediate frequency signal by the mixer 23 mixing it with the local oscillation signal LO. The respective IF signals re output to the phase detectors 106 and 107 through the bandpass filters 15 and 24.

Since the RIF switch 13 is provided in the normally used radio receiving circuit 301, the antenna selection diversity can be performed while powering off the radio receiving circuit 302. Further, since the RF switch 13 is provided downstream from the RIF amplifiers 12 and 22, noise immunity can be improved.

For a diversity decision method, several variations can be considered.

As an example, the detected values, that is, received signal quality 0, received electric-field level RSS, and fading pitch FP, are averaged in a time slot or in steps of a predetermined count before being compared with the respective threshold values. Every time the averaging calculation has been completed for each time slot or count step, arithmetic registers used for averaging calculation are reset. As another example, the arithmetic registers may be reset every time the diversity decision result is changed.

In order to burden the processor with less calculation task, it is preferable that the averaging calculation is started only when any of the detected values has been deteriorated. It is also possible to switch from the antenna selection diversity to the diversity combining immediately after any of the detected values has been deteriorated.

16 Preferably, the threshold values stored in the memory 113 may be updated based on accumulated diversity decision results. In other words, a threshold updating program runs on the diversity controller 14 to update the threshold values so as to meet a change of radio condition, resulting in stable receiving characteristics.

As described above, the received signal quality Q, the received electric-field level RSS, and the fading pitch FP are used to determine which one of the antenna selection diversity and the diversity combining should be selected. Therefore, radio conditions can be monitored from three viewpoints (received signal quality, signal strength, and fading pitch), resulting in precise diversity switching decision. Further, since the deterioration of radio conditions can be detected early, the receiving characteristics can be made stable and the channel disconnection can be prevented. Therefore, when hand-over operation fails to be made, the previous channel can be easily be obtained again. Further, the hand-over operation can be started early and completed smoothly.

Further, one of the radio receiving systems is powered off during the antenna selection diversity. Therefore, in the case of the antenna selection diversity, the power consumption is dramatically reduced.

It will be understood that, although the invention has been illustrated, by way of example, with reference to particular arrangements, variations and modifications thereof, as well as other arrangements may be made within the scope of the protection sought by the appended claims.

Claims

17 CLAIMS

1 A diversity control apparatus for use in a radio communication device having an antenna selection diversity mode and a diversity combining mode, including a signal strength detector for detecting a received signal strength from a received signal, a fading pitch detector for detecting a fading pitch from the received signal strength, a quality detector for detecting a received signal quality based on the received signal, and a diversity mode selector for selecting one of the antenna selection diversity mode and the diversity combining mode depending on whether at least one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated.

2. A diversity receiver including a plurality of antennas, a first radio receiving system for receiving a radio-frequency signal to produce first received data, at least one second radio receiving system connected to a corresponding antenna of the plurality of antennas to produce second received data, a first switch for selecting one of radio-frequency signals which are each received at the plurality of antennas and outputting a selected radio frequency signal to the first radio receiving systems, a combiner for combining the first received data and the second received data to produce combined received data, a second switch for selecting one of the first received data and the combined received data, a demodulator for demodulating a selected received data inputted from the second switch to produce received data and quality data of the selected received data, a signal 18 strength detector for detecting a received signal strength based on radiofrequency signals received at the plurality of antennas, a fading pitch detector for detecting a fading pitch from the received signal strength, a memory for storing threshold values each corresponding to the received signal strength, the fading pitch, and the received signal quality, a power-supply controller for powering off the at least one second radio receiving system and the combiner when the diversity receiver is in a power-on state, and a diversity controller for controlling the first and second switches and the power-supply controller such that one of an antenna selection diversity mode and a diversity combining mode is selected depending on whether at least one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated.

3. A diversity receiver as claimed in claim 2, wherein, when the antenna selection diversity mode is selected, a combination of the at least one second radio receiving system and the combiner is powered off and the second switch selects the first received data.

4. A diversity receiver as claimed in claim 3, wherein, when the diversity combining mode is selected, the combination of the at least one second radio receiving system and the combiner is powered on, the first switch selects a radio-frequency signal received at a predetermined antenna, and the second switch selects the combined received data.

19 5. A diversity receiver as claimed in claim 2, wherein the signal strength detector detects a maximum signal strength from signal strengths of the radio-frequency signals received at the plurality of antennas to produce the maximum signal strength as the received signal strength. 5 6. A diversity receiver as claimed in claim 2, wherein the signal strength detector detects an averaged signal strength of signal strengths of the radiofrequency signals received at the plurality of antennas to produce the averaged signal strength as the received signal strength.

7. A diversity receiver as claimed in claim 2, wherein the first switch is incorporated in the first radio receiving system.

8. A diversity receiver as claimed in claim 7, wherein the first radio receiving system includes a first bandpass filter connected to a predetermined antenna, a first radio-frequency amplifier for amplifying an output of the first bandpass filter, the first switch having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal is connected to the radio frequency amplifier, a first frequency converter for converting a radio-frequency signal output from the output terminal of the first switch into a first lower-frequency signal, and a first phase detector for detecting a phase signal from the first lower- frequency signal to produce the first received data, and the at least one second radio receiving system including a second bandpass fitter connected to a corresponding antenna, a second radio-frequency amplifier for amplifying an output of the second bandpass filter to output an amplified radio-frequency signal to the second input terminal of the first switch, and a second frequency converter for converting the amplified radio-frequency signal into a second lower- frequency signal, and a second phase detector for detecting a phase signal from the second lower-frequency signal to produce the second received data.

9. A diversity receiver as claimed in claim 2, wherein the diversity controller compares each of the received signal strength, the fading pitch, and the received signal quality with a corresponding threshold value stored in the memory to determine whether at least one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated.

10. A diversity receiver as claimed in claim 9, wherein the diversity controller updates the threshold values based on determination results which were performed by the diversity controller.

11. A diversity control method for a radio communication device having an antenna selection diversity mode and a diversity combining mode, including the steps of detecting a received signal strength from a received signal, detecting a fading pitch from the received signal strength, detecting a received signal quality based on the received signal, and selecting one of the antenna selection diversity mode and the diversity combining mode depending on whether at least one of the received signal strength, the fading 21 pitch, and the received signal quality has been deteriorated.

12. A diversity control method for use in a diversity receiver including a plurality of antennas, a first radio receiving system for receiving a radio frequency signal to produce first received data, and at least one second radio receiving system connected to a corresponding antenna of the plurality of antennas to produce second received data, the method including the steps of:

a) selecting one of the radio-frequency signals which are each received at the plurality of antennas and outputting a selected radio frequency signal to the first radio receiving system, b) combining the first received data and the second received data to produce combined received data, C) selecting one of the first received data and the combined received data, d) demodulating a selected received data inputted from the second switch to produce received data and quality data of the selected received data, e) detecting a received signal strength based on radio-frequency signals received at the plurality of antennas, f) detecting a fading pitch from the received signal strength, g) storing threshold values each corresponding to the received signal strength, the fading pitch, and the received signal quality, h) powering off the at least one second radio receiving system and the combiner when the diversity receiver is in a power-on state, and 22 i) controlling the first and second switches and the power-supply controller such that one of an antenna selection diversity mode and a diversity combining mode is selected depending on whether at least one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated.

13. A diversity control method as claimed in claim 12, wherein in the step (i), when the antenna selection diversity mode is selected, a combination of the at least one second radio receiving system and the combiner is powered off, and in the step (c) the first received data is selected.

14. A diversity control method as claimed in claim 13, wherein in the step (i), when the diversity combining mode is selected, the combination of the at least one second radio receiving system and the combiner is powered on, in the step (a), a radio-frequency signal received at a predetermined antenna is selected, and in the step (c), the combined received data is selected.

15. A diversity control method as claimed in claim 12, wherein the step (i) includes the step of comparing each of the received signal strength, the fading pitch, and the received signal quality with a corresponding threshold value stored to determine whether at least one of the received signal strength, the fading pitch, and the received signal quality has been deteriorated.

23 16. A diversity control method as claimed in claim 15, wherein the step (i) further includes the step of updating the threshold values based on past accumulated determination results obtained by the step (i).

17. A diversity control apparatus as claimed in claim 1 including an arrangement substantially as described herein with reference to any one of the accompanying drawings. 18. A diversity receiver as claimed in claim 2 including an arrangement 10 substantially as described herein with reference to any one of the accompanying drawings. 19. A diversity control method as claimed in claim 11 substantially as described herein with reference to the accompanying drawings. 15 20. A diversity control method as claimed in claim 12 substantially as described herein with reference to the accompanying drawings. 20