JPWO1995009495A1 - Selection diversity system - Google Patents

Abstract

(57) [Abstract] A selection diversity device and its control method employ a pre-detection diversity system, and are capable of switching branches without signal errors, even when receiving a communication physical slot with a short preamble signal section. When receiving a control physical slot in which the preamble signal section included in the received burst is long enough for the time required for branch selection and switching, branch determination and switching are performed during the preamble signal section, and when receiving a communication physical slot in which the preamble signal section is not long enough, branch determination is performed during burst reception, and branch switching is performed during the guard time immediately before the burst one frame later.

Description

[Detailed Description of the Invention] Selective Diversity System Technical Field This invention relates to a selective diversity device and its control method for digital mobile communications using time-division multiplexed digital signals. In particular, it relates to a selective diversity device and its control method that prevents signal errors by varying the switching timing of receiving circuit branches according to the length of the signal section of a preamble signal included in the received digital signal.

Background Technology Conventional selective diversity methods for digital mobile communications include: 1) Post-detection diversity, which provides multiple receiver chains (receive circuit branches) and selects and switches between receiver circuit branches based on the reception quality of each demodulated signal. 2) Pre-detection diversity, which selects and switches between receiver circuit branches at the radio frequency (RF) or intermediate frequency (IF) signal stage before detection.

The former, post-detection diversity, provides good diversity effects but has the drawback of requiring multiple receive sequences before detection. The latter, pre-detection diversity, requires only a single receive sequence after switching, but has the drawback of signal errors occurring due to phase discontinuities in the radio frequency or intermediate frequency signal when branch switching occurs during signal reception.

For this reason, in the past, when adopting the latter pre-detection diversity method, it was necessary to switch the receiver branch during reception of the preamble signal, when signal errors would not be a problem.

However, in digital mobile communications, this preamble signal section is generally set sufficiently long in the control channel's control physical slot, but is set short in the communication channel's communication physical slot. Therefore, when branch selection and switching are attempted within the preamble signal section of this short communication physical slot, the branch switching may not be completed within the preamble signal section, resulting in signal errors and other problems due to the branch switching.

Additionally, if the received data is time-division multiplexed, it would be possible to receive the previous burst and select the branch with the best characteristics at that time. However, this configuration is not feasible because the previous burst may be used for communication with a completely different terminal.

Thus, conventional pre-detection diversity techniques have the advantage that only a single receive sequence is required after branch switching. However, when the preamble signal interval is short, such as when receiving a physical communication slot of a communication channel, the branch selection and switching process may not be completed in time within the preamble signal interval, resulting in signal errors due to branch switching.

Disclosure of the Invention The objective of this invention is to provide a selective diversity device and its control method that employs a pre-detection diversity method and enables branch switching without signal errors, even when receiving a communication physical slot on a communication channel with a short preamble signal duration.

To achieve the above object, the present invention comprises a plurality of antennas, a plurality of receiving circuit branches respectively corresponding to the plurality of antennas and inputting received signals from each antenna, a plurality of level detecting means for detecting the receiving levels of the receiving circuit branches, a determining means for determining the receiving circuit branch with the highest receiving level based on the detection outputs of the plurality of level detecting means, a selecting means for selecting one of the plurality of receiving circuit branches in response to the determination output of the determining means, and a determining/selecting control means for causing the determining means to make a determination at a first timing and causing the selecting means to make a selection at a second timing.

Here, the receiving circuit branch includes a radio frequency circuit that processes a signal received by the antenna, and a frequency conversion circuit that converts the radio frequency signal output from the radio frequency circuit into an intermediate frequency signal, and the level detection means detects the receiving level based on the output of the frequency conversion circuit.

The determining means also includes a comparison circuit that compares the reception levels of the reception branches, and determines the reception circuit branch with the highest reception level based on the output of the comparison circuit.

Furthermore, the received signal from the antenna is a burst-shaped signal having a frame structure including multiple slots, each of which includes a preamble signal, with a guard time between each slot. The judgment/selection control means sets the first timing within the period of the preamble signal and the second timing within the period of the guard time.

Furthermore, the received signal from the antenna is a burst-shaped signal having a frame structure including multiple slots, each of which includes a preamble signal. The burst-shaped signal includes control physical slots and communication physical slots with guard times between each slot. The duration of the preamble signal in the control physical slot is set longer than the duration of the preamble signal in the communication physical slot. The determination and selection control means, upon receiving the control physical slot, sets the first timing and the second timing within the duration of the preamble signal, and, upon receiving the communication physical slot, sets the first timing to the same timing as when receiving the control physical slot and sets the second timing within the duration of the guard time.

The present invention also provides a plurality of antennas for receiving burst-like signals, including control physical slots and communication physical slots, each containing a preamble signal and with a guard time set between each slot, the duration of the preamble signal in the control physical slot being set longer than the duration of the preamble signal in the communication physical slot; a plurality of receiving circuit branches provided corresponding to each of the plurality of antennas and receiving the received signals from each of the antennas; a plurality of level detection means for detecting the receiving levels of each of the receiving circuit branches; and a receiving circuit branch with the highest receiving level based on the detection outputs of the plurality of level detection means. The receiver circuit branch is provided with a determination means for determining a branch, a selection means for selecting one of the plurality of receiving circuit branches in response to a determination output of the determination means, and a determination/selection control means for, when receiving the control physical slot, making a determination by the determination means at a first timing within the period of the preamble signal of the control physical slot and making a selection by the selection means at a second timing within the period of the preamble signal of the control physical slot, and, when receiving the communication physical slot, making a determination by the determination means at the same timing as the first timing and making a selection by the selection means at a third timing within the period of the guard time.

Here, the burst-like signal received by the antenna is composed of a superframe signal, which is a multiframe of frames each including a control physical slot and a communication physical slot.

Furthermore, this invention relates to a system including a plurality of antennas for receiving burst-like signals, each of which includes a control physical slot and a communication physical slot, each of which includes a preamble signal and a guard time between the slots, the duration of the preamble signal in the control physical slot being longer than the duration of the preamble signal in the communication physical slot; a plurality of receiving circuit branches corresponding to the plurality of antennas, each of which receives a received signal from each antenna; a plurality of level detection means for detecting the receiving levels of the receiving circuit branches; and a determination means for determining the receiving circuit branch with the highest receiving level based on the detection outputs of the plurality of level detection means. A control method for a selective diversity device including a selection means for selecting one of the plurality of receiving circuit branches in response to a decision output from the decision means, the control method comprising: a first step of, when receiving the control physical slot, having the decision means make a decision at a first timing within a period of the preamble signal of the control physical slot and having the selection means make a selection at a second timing within the period of the preamble signal of the control physical slot; and a second step of, when receiving the communication physical slot, having the decision means make a decision at the same timing as the first timing and having the selection means make a selection at a third timing within the period of the guard time.

Here, the burst-like signal received by the antenna is composed of a superframe signal, which is a multiframe of frames each including a control physical slot and a communication physical slot.

In this invention, when a control physical slot having a sufficiently long preamble signal section is received, the determination means makes a determination and the selection means selects a receiving circuit branch, i.e., switches, during this preamble signal section. When a communication physical slot having a short preamble signal section is received, the determination means makes a determination at the same timing as when the control physical slot is received, and the selection means selects a receiving circuit branch, i.e., switches, during the next guard time.

This allows branch switching to be performed without signal errors even if there is a phase difference between multiple receiving circuit branches.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram showing one embodiment of a selective diversity device according to the present invention.

Figure 2 is a block diagram showing the detailed configuration of the circuitry that determines and selects branches in the selector shown in Figure 1.

Figure 3 shows the control physical slots received on the control channel and the branch selection and switching timing.

FIG. 4 shows the timing of determining and switching between communication physical slots and branches received on a communication channel in digital mobile communications.

Figure 5 shows the LCCH superframe structure used in digital mobile communications.

FIG. 6 is a block diagram showing another embodiment of a selective diversity device according to the present invention.

FIG. 7 is a block diagram showing the overall configuration of a base station for a digital mobile communication system incorporating the selective diversity system of the present invention.

8 is a circuit diagram showing an example of the configuration of the antenna switch shown in FIG. 7. FIG.

FIG. 9 is a block diagram showing the overall configuration of a mobile station of a digital mobile communication system to which the selective diversity device of the present invention is applied.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a selective diversity device and its control method according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a selective diversity apparatus according to the present invention.

The selective diversity device shown in Figure 1 is employed, for example, in the receiving system of the radio section of a base station of a digital mobile communication device. The selective diversity device shown in Figure 1 has a first receiving circuit branch consisting of an antenna 11, a radio circuit (RF circuit) 12, an intermediate frequency circuit (IF circuit) 13, and a quadrature detector 14, and a second receiving circuit branch consisting of an antenna 21, a radio circuit (RF circuit) 22, an intermediate frequency circuit (IF circuit) 23, and a quadrature detector 24.

The receiver also includes a level detector 15 that detects the reception level of an intermediate frequency circuit (IF circuit) 13, and a level detector 25 that detects the reception level of an intermediate frequency circuit (IF circuit) 23. A comparator 31 compares the detection level of the level detector 15 with the detection level of the level detector 25. A selector 32 selects and switches between the first and second reception circuit branches in accordance with the comparison result of the comparator 31.

That is, the comparator 31 compares the detection level of the level detector 15 with the detection level of the level detector 25, and the selector 32 selects the output of the first receiving circuit branch, i.e., the output of the quadrature detector 14, if the detection level of the level detector 15 is higher than the detection level of the detector 25, and selects the output of the first receiving circuit branch, i.e., the output of the quadrature detector 24, if the detection level of the level detector 25 is higher than the detection level of the level detector 15.

The output of the first receiving circuit branch or the second receiving circuit branch selected by the selector 32 is then applied to a demodulator 33 at the subsequent stage.

In the digital mobile radio device to which this embodiment is applied, a control physical slot and a communication physical slot are included, each slot includes a preamble signal, and a guard time is set between each slot. The duration of the preamble signal in the control physical slot is set longer than the duration of the preamble signal in the communication physical slot. Antennas 11 and 21 receive this burst-like signal.

In the selective diversity device of this embodiment, the selection timing, i.e., the switching timing, of the first and second receiving circuit branches in the selector 32 is configured to differ when receiving a control physical slot and when receiving a communication physical slot.

That is, the timing of the comparison between the detection level of level detector 15 and the detection level of level detector 25 in comparator 31, i.e., the timing of determining whether to use the first or second receiving circuit branch, is set to the same value, but the timing of the selection between the first and second receiving circuit branches in selector 32, i.e., the switching timing, differs between when a control physical slot is received and when a communication physical slot is received.

Figure 2 shows the detailed configuration of the control unit that selects, i.e., switches, the branches in the selection unit 32 shown in Figure 1. This circuit includes a latch circuit 321 that latches the comparison output of the comparison unit 31 shown in Figure 1, a decision timing generation circuit 323 that generates a decision timing signal that indicates the latch timing of the latch circuit 321, i.e., the branch selection decision timing, a switch timing generation circuit 327 that generates a switch timing signal that indicates the branch switch timing, a timing selection unit 326 that selects the switch timing signal generated by the switch timing generation circuit 327, a branch switch signal output circuit 322 that outputs a branch switch signal based on the signal latched in the latch circuit 321 using the switch timing signal selected by the timing selection unit 326 as a trigger, a central processing unit (CPU) 324, and a port 325 that receives the output of the CPU 324.

In FIG. 2, the comparator 31 compares the reception level A, which is the detection level of the level detector 15 of the first receiving circuit branch, with the reception level B, which is the detection level of the level detector 25 of the second receiving circuit branch, and latches the comparison result in the latch circuit 321 at the timing of the determination timing signal generated by the determination timing generator 323. Here, the determination timing generator 323 is configured to generate the determination timing signal within the period of the preamble signal of the control physical slot.

Furthermore, the central processing unit (CPU) 324 determines whether the received burst signal is a control physical slot or a communication physical slot based on the sequence, and outputs the determination result to the timing selection unit 326 via the port unit 325.

If the signal from the port unit 325 indicates that the receiving slot is a control physical slot, the timing selection unit 326 selects the switching timing signal generated by the switching timing generation circuit 327 within the period of the preamble signal of the control physical slot and outputs it to the branch switching signal output circuit 322. If the signal from the port unit 325 indicates that the receiving slot is a communication physical slot, the timing selection unit 326 selects the switching timing signal generated by the switching timing generation circuit 327 within the period of the guard time one frame after the communication physical slot and outputs it to the branch switching signal output circuit 322.

The branch switching signal output circuit 322 generates and outputs a branch switching signal based on the signal latched by the latch circuit 321, at the timing of the switching timing signal applied from the timing selector 326.

That is, according to the circuit shown in FIG. 2, the comparison result of the comparator circuit 31 is latched at the timing of the decision timing signal generated by the decision timing generator circuit 323, i.e., within the period of the preamble signal of the control physical slot, both when a control physical slot is received and when a communication physical slot is received. However, the branch switching signal output circuit 322 outputs a branch switching signal within the period of the preamble signal of the control physical slot when a control physical slot is received, and within the period of the guard time of the communication physical slot one frame later when a communication physical slot is received.

Figure 3 shows an example of a control physical slot used in a digital mobile communication device to which this embodiment is applied, Figure 4 shows an example of a communication physical slot, and Figure 5 shows an LCCH superframe structure used in a digital mobile communication device to which this embodiment is applied.

Next, the operation of the selection diversity apparatus shown in FIGS. 1 and 2 will be described in more detail with reference to FIGS. 3 through 5.

The control physical slot shown in FIG. 3 is composed of a 4-bit burst transient response time bit R, a 2-bit start symbol bit SS, a 62-bit preamble bit PR, a 32-bit synchronization word bit UW, a 108-bit control signal bit CAC, and a 16-bit check bit CRC, followed by a 16-bit guard time bit.

The communication physical slot shown in FIG. 4 is composed of a 4-bit burst transient response time bit R, a 2-bit start symbol bit SS, a 6-bit preamble bit PR, a 16-bit synchronization word bit UW, a 180-bit information signal bit I, and a 16-bit check bit CRC, followed by a 16-bit guard time bit.

The LCCH superframe structure used in the digital mobile communication device to which this embodiment is applied, shown in FIG. 5, is set to nSG = 2, nSUB = 4, nPCH = 3, and nGROUP = 2. One frame consists of eight slots, with each slot being 625 μs and each frame being 5 ms, resulting in a multiframe structure in which each slot appears every 150 ms. Overall, the LCCH superframe structure employs a repeating sequence of BC, S, S, P1, S, S, S, P2 every 1.2 s.

Here, BC indicates a system information broadcast message (BCCH), S indicates a link channel establishment request and link channel assignment (SCCH), and P1 and P2 indicate incoming calls (PCH).

Considering the slot and frame structures shown in Figures 3 through 5, the preamble bit PR of the control physical slot is sufficiently long at 62 bits, as shown in Figure 3, making it possible to select and switch branches within the period of this preamble bit PR. However, the preamble bit PR of the communication physical slot is short at 6 bits, as shown in Figure 4, making it impossible to select and switch branches within the period of this preamble bit PR.

Furthermore, when using the LCCH superframe structure shown in Figure 5, communication physical frames occur every 5 ms, but control physical slots occur intermittently every 1.2 s. Therefore, if they cannot be received accurately the first time, the time required to establish a connection between terminals will be extended.

Therefore, in this embodiment, the preamble bit PR is sufficiently long to allow branch selection and switching within the period of this preamble bit PR. However, if the preamble bit PR is not received correctly in one attempt, the time required to establish a connection between terminals will be extended. When receiving a control physical slot, branch selection and switching are performed within the period of the preamble bit PR. When receiving a communication physical slot, which has a short preamble bit PR and appears every 5 ms, branch determination is performed at the same timing as when the control physical slot is received, and branch switching is performed during the guard time one frame later.

That is, as shown in FIG. 3, when a control physical slot is received, branch determination and switching are performed within the 18th bit from the beginning of the burst transient response time bit R of the control physical slot, i.e., within the period of the preamble bit PR of the control physical slot.

Specifically, in the configuration shown in FIG. 2, a decision timing signal is generated from the decision timing generation circuit 323 at the timing of the 18th bit from the beginning of the burst transient response time bit R of the control physical slot, and the comparison result of the comparator 31 is latched in the latch circuit 321 in synchronization with this decision timing signal to determine the branch to be used. Furthermore, a switching timing signal generated by the switching timing generation circuit 327 is selected by the timing selection unit 326 within the period of the preamble bit PR of this control physical slot and applied to the branch switching signal output circuit 322, causing the branch switching signal output circuit 322 to generate a branch switching signal within the period of the preamble bit PR of this control physical slot, and this branch switching signal performs branch switching.

In contrast, as shown in Figure 4, when a communication physical slot is received, branch decisions are made at the same timing as when a control physical slot is received, and branch switching is performed within the guard time period one frame later.

Specifically, in the configuration shown in FIG. 2, the decision timing generation circuit 323 generates a decision timing signal at the timing of the 18th bit from the beginning of the burst transient response time bit R of the communication physical slot, i.e., within the period of the synchronization word bit UW of the communication physical slot, just as when a control physical slot is received. The comparison result of the comparator 31 is latched in the latch circuit 321 in synchronization with this decision timing signal, thereby determining the branch to be used. Furthermore, the timing selector 326 selects a switch timing signal generated by the switch timing generation circuit 327 within the guard time period one frame after this communication physical slot and applies this signal to the branch switch signal output circuit 322, thereby generating a branch switch signal from the branch switch signal output circuit 322 within the guard time period one frame after this communication physical slot, and this branch switch signal performs branch switching.

In this case, the branch switching period during communication channel reception is 5 ms, which is significantly shorter than the fading period of 0.1 s.

Thus, in this embodiment, when a control physical slot is received in which the preamble signal section included in the received burst is long enough relative to the time required for branch determination and switching, branch determination and switching are performed during the preamble signal section. When a communication physical slot is received in which the preamble signal section is not long enough, branch determination is performed during burst reception, and branch switching is performed during the guard time immediately preceding the burst one frame later. This allows branch switching without signal errors even if there is a phase difference between the multiple received signals. Moreover, the system can be reduced to a single system after the branch switching point, resulting in a selection diversity device that can achieve low cost, reduced power consumption, and compact size.

In the above embodiment, the first receiving circuit branch is composed of an antenna 11, a radio frequency circuit (RF circuit) 12, an intermediate frequency circuit (IF circuit) 13, and a quadrature detector 14, and the second receiving circuit branch is composed of an antenna 21, a radio frequency circuit (RF circuit) 22, an intermediate frequency circuit (IF circuit) 23, and a quadrature detector 24. However, as shown in FIG. 6, a quadrature detector 34 may be provided in place of the quadrature detectors 14 and 24, and a selector 32 may select either the output of the intermediate frequency circuit (IF circuit) 13 as the output of the first receiving circuit branch or the output of the intermediate frequency circuit (IF circuit) 23 as the output of the second receiving circuit branch, and then the output of the selector 32 may be applied to a demodulator 33 via the quadrature detector 34.

FIG. 7 shows the overall configuration of a base station for digital mobile communications systems incorporating the selective diversity system of the present invention, and FIG. 9 shows the overall configuration of a mobile station connected to this base station via a radio line.

Base station 100 for digital mobile communications devices shown in FIG. 7 transmits and receives signals in the 1.9 GHz band and is equipped with two antennas 101 and 102, two radio frequency receiving circuits 104 and 105, and one radio frequency transmitting circuit 106. The two radio frequency receiving circuits 104 and 105 and the one radio frequency transmitting circuit 106 are connected to the two antennas 101 and 102 via antenna switch 103.

The outputs of the two radio frequency receiving circuits 104 and 105 are connected to a channel codec 109 via a diversity switching circuit 108. The channel codec 109 is connected to an extension interface circuit 111 via an ADPCM codec 110. The extension interface circuit 111 is connected to an extension terminal of a private branch exchange (PBX) (not shown) via interface transformers 114 and 115. The output of the channel codec 109 is connected to a radio frequency transmitting circuit 106.

The output of a frequency synthesizer 107 is applied to two high-frequency receiving circuits 104 and 105 and one high-frequency transmitting circuit 106.

In addition, a control circuit 112 is connected to the antenna switch 103, diversity switching circuit 108, channel codec 109, ADPCM codec 110, extension interface circuit 111, and frequency synthesizer 107, and the operations of these circuits are controlled by this control circuit 112.

The control circuit 112 is also connected to an ID memory 113 that stores an ID code for identifying the base station 100.

Also connected to base station 100 is power supply unit 120, which includes AC/DC conversion circuit 121, which converts 100V AC to 12V DC. The output of AC/DC conversion circuit 121 is applied to power supply switching circuit 116 of base station 100. Power supply switching circuit 116 switches between the output of AC/DC conversion circuit 121 and the PBX power supply and supplies it to power supply circuit 117, which in turn supplies power to various components of base station 100.

In this configuration, the two systems of receiving high frequency circuits 104, 105 and diversity switching circuit 108 constitute the selective diversity device according to the present invention.

That is, the diversity switching circuit 108 of FIG. 7 is configured to determine and switch between the two receiving high-frequency circuits 104 and 105 in response to the reception levels of the two receiving high-frequency circuits 104 and 105. The determination of which of the two receiving high-frequency circuits 104 and 105 to use is made at a fixed timing of the burst signal received by the antennas 101 and 102. The switching is performed during the preamble signal period when a control physical slot is received in which the preamble signal period included in the received burst is sufficiently long compared to the time required for branch determination and switching. However, when a communication physical slot is received in which the preamble signal period is not long enough, the switching is performed during the guard time immediately preceding the burst one frame later. In the configuration of FIG. 7, this control is performed by the control circuit 112.

Fig. 8 shows a detailed configuration example of the antenna switch 103 shown in Fig. 7. The antenna switch 103 shown in Fig. 8 is composed of a strip line 130 branched into five terminals T1 to T5, and high frequency switches SW1 to SW5 provided corresponding to each of the terminals T1 to T5.

Here, a receiving radio frequency circuit 104 is connected to terminal T1 of the strip line 130, an antenna 101 is connected to terminal T2, a transmitting radio frequency circuit 106 is connected to terminal T3, an antenna 102 is connected to terminal T4, and a receiving radio frequency circuit 105 is connected to terminal T5.

Furthermore, the high-frequency switches SW1 to SW5 function as diode switches that connect the signals at the terminals T1 to T5 of the strip line 130 to ground (this state is referred to as the high-frequency switch being off) or disconnect the signals from ground (this state is referred to as the high-frequency switch being on) in a high-frequency manner.

Specifically, the high-frequency switch SW1 is composed of capacitors C1 and C2, resistors R1 and R2, and diode D1, and is turned on when −4 V is applied to terminal V1 and +4 V is applied to terminal V2. Conversely, it is turned off when +4 V is applied to terminal V1 and −4 V is applied to terminal V2.

The high frequency switch SW2 is composed of capacitors C3 and C4, resistors R3 and R4, and diode D2, and is turned on when −4 V is applied to terminal V3 and +4 V is applied to terminal V4, and conversely, is turned off when +4 V is applied to terminal V3 and −4 V is applied to terminal V4.

The high frequency switch SW3 is composed of capacitors C5 and C6, resistors R5 and R6, and diode D3, and is turned on when −4 V is applied to terminal V5 and +4 V is applied to terminal V6, and conversely, is turned off when +4 V is applied to terminal V5 and −4 V is applied to terminal V6.

The high frequency switch SW4 is composed of capacitors C7 and C8, resistors R7 and R8, and diode D4, and is turned on when −4 V is applied to terminal V7 and +4 V is applied to terminal V8, and conversely, is turned off when +4 V is applied to terminal V7 and −4 V is applied to terminal V8.

The high-frequency switch SW5 is composed of capacitors C9 and C10, resistors R9 and R10, and diode D5. It turns on when −4 V is applied to terminal V9 and +4 V is applied to terminal V10, and turns off when +4 V is applied to terminal V9 and −4 V is applied to terminal V10.

In this configuration, when base station 100 receives a signal, only high-frequency switch SW3 is turned on, and the other high-frequency switches SW1, SW2, SW4, and SW5 are turned off. In this state, the high-frequency signal received by antenna 101 is output to high-frequency receiving circuit 104, and the high-frequency signal received by antenna 102 is output to high-frequency receiving circuit 105. Furthermore, the high-frequency signal from high-frequency transmitting circuit 106 is grounded via high-frequency switch SW3, and is therefore not output from either antenna 101 or 102.

Furthermore, when base station 100 transmits, it uses the antenna with the better reception sensitivity between antennas 101 and 102. For example, if antenna 101 has better reception sensitivity than antenna 102, high-frequency switches SW1 and SW4 are turned off, and high-frequency switch SW3 is turned on. In this case, the high-frequency signal from transmitting high-frequency circuit 106 is output from antenna 101.

Conversely, if antenna 102 has better reception sensitivity than antenna 102, high-frequency switches SW2 and SW5 are turned off and high-frequency switch SW3 is turned on.

In this case, the high frequency signal from the transmitting high frequency circuit 106 is output from the antenna 102.

The mobile station 200 of the digital mobile communication device shown in FIG. 9 is equipped with one antenna 201, which is connected to a transmitting high-frequency circuit 203 and a receiving high-frequency circuit 204 via an antenna switch 202.

The transmitting high-frequency circuit 203 is connected to a microphone 210 and an audio input terminal of a headset terminal 216 via a channel codec 206 and an audio codec 207, while the receiving high-frequency circuit 204 is connected to a speaker 211 via the channel codec 206 and the audio codec 207, and is also connected to an audio output terminal of the headset terminal 216 via an amplifier 214 and a diode circuit 215.

The output of a frequency synthesizer 205 is also applied to the transmitting high frequency circuit 203 and the receiving high frequency circuit 204.

A control circuit 208 is connected to the frequency synthesizer 205, the channel codec 206, and the voice codec 207, and the operations of these circuits are controlled by this control circuit 208.

Also connected to the control circuit 208 is an ID memory 209 that stores an ID code for identifying the mobile station 200, and further connected to the control circuit 208 via an amplifier 212 is a sounder 213 for announcing an incoming call.

A battery pack 220 is connected to the mobile station 200, and the 4.8 V DC output from the battery pack 220 is supplied to a power supply circuit 217, which supplies power to each component of the mobile station 200.

In the above embodiment, the selective diversity device of the present invention is applied to a base station of a digital mobile communication device. However, the selective diversity device of the present invention can also be applied to a mobile station of a digital mobile communication device.

INDUSTRIAL APPLICABILITY As described above, this invention provides a selective diversity device and control method suitable for application to digital mobile communications devices, which eliminates signal errors during branch switching and achieves low cost, reduced power consumption, and compact size. When receiving a control physical slot with a sufficiently long preamble signal, the branch to be used (switched) is determined and the branch switching is performed during this preamble signal. When receiving a communication physical slot with a short preamble signal, the branch to be used (switched) is determined at the same timing as when the control physical slot is received, but the branch switching is performed during the next guard time.

───────────────────────────────────────────────────── (Note) This publication is based on the publication published internationally by the International Bureau of Patents (WIPO). The effect of the international publication of the Japanese patent application (Japanese utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act) and is unrelated to this publication.

Claims (10)

[Claims] (1) A selective diversity device comprising: a plurality of antennas; a plurality of receiving circuit branches corresponding to the plurality of antennas, each receiving a received signal from the corresponding antenna; a plurality of level detection means for detecting the receiving levels of the receiving circuit branches; a determination means for determining the receiving circuit branch with the highest receiving level based on the detection outputs of the plurality of level detection means; a selection means for selecting one of the plurality of receiving circuit branches in response to the determination output of the determination means; and a determination and selection control means for causing the determination means to make a determination at a first timing and the selection means to make a selection at a second timing. (2) The receiving circuit branch includes a radio frequency circuit that processes the received signal received by the antenna, and a frequency conversion circuit that converts the radio frequency signal output from the radio frequency circuit into an intermediate frequency signal, and the level detection means detects the receiving level based on the output of the frequency conversion circuit. (3) The determination means includes a comparison circuit that compares the reception levels of each reception branch, and the CLAIM1 selection diversity device determines the reception circuit branch with the highest reception level based on the output of the comparison circuit. (4) The signal received by the antenna is a burst-shaped signal having a frame structure, wherein each slot of the burst-shaped signal contains a preamble signal and a guard time is set between each slot, and the determination and selection control means sets the first timing within the period of the preamble signal and sets the second timing within the period of the guard time. A selective diversity device of CLAIM1. (5) The received signal from the antenna is a burst-shaped signal having a frame structure including multiple slots, the burst-shaped signal includes a control physical slot and a call physical slot, each of which includes a preamble signal and a guard time between the slots, the duration of the preamble signal in the control physical slot is set longer than the duration of the preamble signal in the call physical slot, the determination and selection control means, upon receiving the control physical slot, sets the first timing and the second timing within the duration of the preamble signal, and, upon receiving the call physical slot, sets the first timing to the same timing as when receiving the control physical slot and sets the second timing within the duration of the guard time. (6) A CLAIM1 selective diversity device in which the received signal from the antenna is a superframe signal, which is a multiframe consisting of a frame consisting of multiple slots. (7) A system including a plurality of antennas for receiving burst-like signals, each including a control physical slot and a call physical slot, each including a preamble signal and a guard time between the slots, wherein the duration of the preamble signal in the control physical slot is longer than the duration of the preamble signal in the call physical slot; a plurality of receiving circuit branches corresponding to the plurality of antennas, each receiving a signal from each antenna; a plurality of level detection means for detecting the reception levels of the receiving circuit branches; a determination means for determining the receiving circuit branch with the highest reception level based on the detection output of the plurality of level detection means; and a selection means for selecting one of the plurality of receiving circuit branches in response to the determination output of the determination means. a determination and selection control means for, when receiving the control physical slot, causing the determination means to make a determination at a first timing within the period of the preamble signal of the control physical slot and causing the selection means to make a selection at a second timing within the period of the preamble signal of the control physical slot, and, when receiving the call physical slot, causing the determination means to make a determination at the same timing as the first timing and causing the selection means to make a selection at a third timing within the period of the guard time. (8) A CLAIM7 selective diversity device in which the burst-shaped signal received by the antenna consists of a superframe signal, which is a multiframe of frames including control physical slots and call physical slots. (9) A control method for a selective diversity device comprising: a plurality of antennas for receiving burst-shaped signals, including control physical slots and call physical slots, each containing a preamble signal, with a guard time set between each slot, and the duration of the preamble signal in the control physical slot being longer than the duration of the preamble signal in the call physical slot; a plurality of receiving circuit branches corresponding to the plurality of antennas, each receiving a signal from each antenna; a plurality of level detection means for detecting the reception levels of the receiving circuit branches; a determination means for determining the receiving circuit branch with the highest reception level based on the detection outputs of the plurality of level detection means; and a selection means for selecting one of the plurality of receiving circuit branches in response to the determination output of the determination means, A control method for a selective diversity device comprising: a first step of, upon receiving the control physical slot, having the determination means make a determination at a first timing within the period of the preamble signal of the control physical slot and having the selection means make a selection at a second timing within the period of the preamble signal of the control physical slot; and a second step of, upon receiving the call physical slot, having the determination means make a determination at the same timing as the first timing and having the selection means make a selection at a third timing within the period of the guard time. (10) A method for controlling a CLAIM9 selective diversity device, wherein the burst-like signal received by the antenna is a signal having a superframe structure, which is a multiframe of frames including control physical slots and call physical slots.