JP2008193384A - Receiver - Google Patents

Abstract

An object of the present invention is to provide a receiving device capable of efficiently receiving radio waves by switching a plurality of antennas provided in the receiving device according to the radio wave reception state.
A switching unit selects one antenna from an antenna element unit or an antenna element unit. Then, based on the state of the received radio wave extracted by the OFDM demodulator 8, the switching unit 6 switches and selects the antenna element unit 2 or the antenna element unit 3. In addition, the control unit 9 controls the timing for switching the antenna according to the reception state.
[Selection] Figure 1

Description

  The present invention relates to a receiving apparatus.

  In a mobile communication system represented by a mobile phone or the like, a plurality of transmission paths (multipath) having different path lengths between a base station and a mobile communication terminal in an urban area where there are many obstacles to radio waves such as buildings. It is often a multipath environment that causes Under such a multipath environment, the received power level of the mobile communication terminal varies with movement due to multipath fading. Then, depending on the location, there arises a problem that the received power level is lower than the required power level (the lowest level at which communication is possible).

  Note that multipath fading is a signal phase difference caused by a difference in the path length of a signal path when signals that have passed through a plurality of transmission paths (paths) having different path lengths from a transmission source are received together. This is a phenomenon in which the reception level varies depending on the reception location as a result of the received signals canceling each other or being superimposed. In particular, when the signals cancel each other, it is a problem in the mobile communication terminal that the reception power level is reduced and falls below the reception limit of the receiver.

  The portable and mobile digital terrestrial television broadcast receivers also have a problem that the reception status is deteriorated due to the influence of multipath fading as in the mobile communication system.

  In order to solve the above problem, a diversity reception method in which a plurality of antennas are installed in a mobile terminal has been proposed.

  FIG. 10 is a configuration diagram of a conventional diversity receiver. Based on the processing data from the OFDM decoder 106 or the MPEG decoder 107, the bit error rate (BER) of the received signal of each antenna is detected, and the antenna switching unit 102 is controlled by the control signal from the control unit 109. A diversity receiving apparatus that controls and selects an antenna 101 with a low bit error rate has been proposed (see, for example, Patent Document 1).

  In addition, a diversity receiver has been proposed that improves the reception rate by switching to an antenna having a high received signal strength. Usually, it is difficult to follow high-speed fluctuations, so the threshold value is taken by averaging the signal strength over time, and a low-pass filter is used to cope with fluctuations due to low-speed fading. (For example, refer to Patent Document 2).

Also, a diversity receiver is proposed in which a determination is made after a certain time has passed after the antenna switching, and when the received signal strength is lower than before the switching, the switching is performed again to enter the Stay state (see, for example, Patent Document 3). .
Japanese Patent Laid-Open No. 2002-33688 JP 2000-295150 A JP 2000-295151 A

  In the receiving apparatus described in the above background art, the bit error rate (BER) of the signal received by each antenna is measured and control is performed to switch to an antenna having a low bit error rate (BER). However, there has been a problem that the bit error rate (BER) fluctuates drastically and the antenna is frequently switched, and the reception performance deteriorates conversely. In addition, since the bit error rate (BER) of signals received by each antenna cannot be measured and compared at the same time, there is a problem that accurate antenna switching control cannot be performed when the error rate (BER) fluctuates severely. It was.

  In view of the above-described problems, an object of the present invention is to provide a receiving device that can efficiently receive radio waves by switching a plurality of antennas provided in the receiving device according to the radio wave reception state. To do.

  In order to solve the above-described problems, a receiving device to which the present invention is applied includes a plurality of antennas that receive radio waves, a switching unit that selects and switches one antenna from the plurality of antennas, and the switching unit. And a control unit that controls the timing of switching the antenna selected by the switching unit in accordance with the received radio wave condition.

  In the receiving apparatus to which the present invention is applied, the antenna switching timing is fixed according to the timing at which the antenna selected by the switching unit is fixed and switched after a lapse of a predetermined time, and the received radio wave condition by the switching unit. And the timing of switching the antenna.

  In the receiving apparatus to which the present invention is applied, the control unit controls timing for switching the antenna selected by the switching unit based on a bit error rate in the received radio wave.

  Further, in the receiving apparatus to which the present invention is applied, the control unit performs control to fix the antenna without switching for a predetermined time when the number of times the antenna is switched by the switching unit becomes a predetermined number or more. And

  As described above, the receiving device according to the present invention includes a plurality of antennas that receive radio waves, a switching unit that selects and switches one antenna from the plurality of antennas, and a control that controls the switching unit. The control unit controls the timing for switching the antenna selected by the switching unit according to the received radio wave condition. Therefore, by switching the antenna according to the received radio wave condition, it is possible to receive the radio wave using a more appropriate antenna.

  In the receiving apparatus according to the present invention, the antenna switching timing is fixed according to the timing at which the antenna selected by the switching unit is fixed and switched after a predetermined time elapses, and the received radio wave condition by the switching unit. The antenna switching timing is used according to the radio wave condition. Therefore, when the antenna is switched, it is possible to prevent frequent switching of the antenna by using the switching timing after a predetermined time has elapsed.

  In the receiving apparatus to which the present invention is applied, the control unit controls the timing for switching the antenna selected by the switching unit based on the bit error rate in the received radio wave.

  In the receiving apparatus to which the present invention is applied, the control unit performs control to fix the antenna without switching for a predetermined time when the number of times of switching the antenna by the switching unit exceeds a predetermined number. Therefore, it is possible to prevent the antenna from changing frequently.

  Hereinafter, an antenna switching diversity receiver and a reception control method according to an embodiment of the present invention will be described with reference to the drawings. The antenna switching diversity receiver according to the present embodiment relates to a portable terminal type digital broadcast receiver capable of receiving terrestrial digital broadcast. FIG. 1 is a functional block diagram showing an overall configuration of a portable terminal type digital broadcast receiving apparatus 1 capable of receiving terrestrial digital broadcast according to the present embodiment.

  As shown in FIG. 1, the digital broadcast receiving apparatus 1 is configured by being divided into blocks of a front end unit 10 and a back end unit 15. The antenna element unit 2 and the antenna element unit 3 are connected to the front end unit 10. In addition, a video display unit 16 and an audio output unit 17 are connected to the back end unit 15.

  Here, the front end unit 10 includes an antenna matching unit 4 connected to the antenna element unit 2, an antenna matching unit 5 connected to the antenna element unit 3, a switching unit 6, a tuner unit 7, and an OFDM demodulation unit. 8 and a control unit 9. Further, the back end unit 15 includes a TS-DEMUX unit 11, a video signal processing unit 12, a data signal processing unit 13, and an audio signal processing unit 14.

  Subsequently, the operation of the digital broadcast receiving apparatus 1 will be described with reference to FIG. First, in the digital broadcast receiving apparatus 1, a signal from a broadcast radio wave received by the antenna element unit 2 is selected as a desired channel by the tuner unit 7 through the antenna matching unit 4 and the switching unit 6, and is transmitted to the OFDM demodulation unit 8. Output as a signal. The IF signal thus selected and output is converted into a digital signal by the analog / digital conversion function in the OFDM demodulator 8. The IF signal converted into the digital signal is demodulated and decoded by the OFDM demodulator 8 and output as a TS signal. Further, the OFDM demodulator 8 outputs information based on the demodulated signal to the controller 9.

  The control unit 9 generates a control signal based on the received signal information and controls the switching unit 6. When it is determined that the reception status at the antenna element unit 2 is poor, the switching unit 6 switches from the antenna element unit 2 to the antenna element unit 3 to receive broadcast radio waves. Similarly to the above, the signal from the broadcast wave received by the antenna element unit 3 is selected as a desired channel by the tuner unit 7 through the antenna matching unit 5 and the switching unit 6, and is output to the OFDM demodulation unit 8 as an IF signal. The The IF signal thus selected and output is converted into a digital signal by the analog / digital conversion function in the OFDM demodulator 8. The IF signal converted into the digital signal is demodulated and decoded by the OFDM demodulator 8 and output as a TS signal. Further, the tuner unit 7 is controlled by a control signal (not shown) from the OFDM demodulating unit 8.

  The TS signal output from the OFDM demodulator 8 is demultiplexed by the TS-DEMUX unit 11 and outputs a video / audio / data broadcast stream. The stream signals separated from the signals are output to the video signal processing unit 12, the audio signal processing unit 14, and the data signal processing unit 13, respectively, and decoding processing of each stream signal is performed.

  The video stream is subjected to decoding processing such as MPEG-2 or MPEG-4 AVC, and the audio stream is mainly subjected to AAC decoding processing. Data broadcasting performs carousel processing, also processes information embedded with video signals and the like, and outputs them as still images or simple moving images.

  The decoded stream signal is output as viewable information from the video display unit 16 and the audio output unit 17. When a video signal or an audio signal is included in the data signal, signal processing is performed in the video signal processing unit 12 and the audio signal processing unit 14, and information that can be viewed by the video display unit 16 and the audio output unit 17. Is output as In the case of text data or the like, information is processed by a browser or application that operates on a CPU, RAM, or the like (not shown), and is similarly output from the video display unit 16 or the audio output unit 17 as viewable information. The operation status of the front end unit 10 and the back end unit 15 is controlled by a CPU or the like (not shown).

  Next, detailed configurations of the antenna element unit 2 and the switching unit 6 will be described with reference to FIG. FIG. 2 is a diagram showing a detailed configuration of the antenna element unit 2, the antenna element unit 3, the antenna matching unit 4, the antenna matching unit 5, and the switching unit 6.

  The antenna element unit 2 is connected to the tuner unit 7 via the antenna matching unit 4 and the switching unit 6. The antenna matching unit 4 includes a first coil element 401 and a second coil element 402. By providing the first coil element 401 between the node between the antenna element section 2 and the second coil element 402 and the ground, impedance matching to the tuner section 7 is performed, and the received signal is not lost in the tuner section. 7 can be input.

  Similarly, the antenna element unit 3 is connected to the tuner unit 7 via the antenna matching unit 5 and the switching unit 6. The antenna matching unit 5 includes a first coil element 501 and a second coil element 502. By providing the first coil element 501 between the node between the antenna element section 3 and the second coil element 502 and the ground, impedance matching to the tuner section 7 is performed, and the received signal is not lost in the tuner section. 7 can be input.

  The antenna matching unit 4 and the antenna matching unit 5 are connected to the switching unit 6, respectively. The switching unit 6 selects a signal output from one of the antenna matching units based on the control signal input from the control unit 9 and outputs the selected signal to the tuner unit 7.

  FIG. 3 is a diagram illustrating a configuration example of the tuner unit 7 of the digital broadcast receiving apparatus 1. As shown in FIG. 3, the tuner unit 7 includes an RF amplifier unit 71, a mixer unit 72, an IF filter unit 73, an IF amplifier unit 74, and a PLL unit 75.

  The RF signal input to the tuner unit 7 is amplified by the RF amplifier unit 71 and converted to an IF signal corresponding to the frequency set by the PLL unit 75 in the mixer unit 72. The IF signal is removed from the IF signal by the IF filter unit 73, amplified by the IF amplifier 74, and output from the tuner unit 7. Further, the amplification factors in the RF amplifier unit 71 and the IF amplifier unit 74 are AGC (automatic gain control) controlled from the OFDM demodulator unit 8 so that the output from the IF amplifier unit 74 becomes a constant level.

  Next, the control parameter (OFDM) will be described. FIG. 4 is a functional block diagram showing a configuration example of the demodulator 8 in the front end unit 10 of the digital broadcast receiver 1 according to the present embodiment. Information used for controlling the switching unit 6 can be obtained from the demodulating unit 8.

  The received radio wave converted to the IF signal in the tuner unit 7 is digitized and input to the orthogonal demodulation unit 81. The quadrature demodulation unit 81 and the next phase correction unit 82 perform signal processing on the received signal in the time domain. That is, correction processing such as filter processing and carrier clock is performed on the time axis data, a capture start point of the FFT unit 83 to be described later is determined, and reception signal data is output to the FFT unit 83. Information about the FFT obtained by the phase correction unit 82 is output to the FFT information output unit 93. The signal input to the FFT unit 83 is input to the detection unit 85 via the frame synchronization unit 84. The detection unit 85 detects TMCC (Transmission and Multiplexing Configuration Control) information, is passed to the TMCC information output unit 94, and is output therefrom.

  Similarly, the detection unit 85 detects parameters related to reception power and C / N, and outputs them to the reception power output unit 95 and the C / N output unit 96. A signal related to TS (Transport Stream) output from the detector 85 is then transmitted to a frequency / time deinterleaver 86, a bit deinterleaver 87, a Viterbi decoder 88, a byte deinterleaver 89, an energy spreader 90, and TS reproduction. Through the unit 91 and the RS (Reed-Solomon) decoding unit 92, the parameter relating to the bit error rate (BER) and the TS are output to the BER output unit 97 and the TS output unit 98.

  Note that the BER can be set to output a value when the RS is turned OFF, and when the reference value is satisfied, the RS is turned ON and the TS is output. Further, when the received video and the reception sensitivity are displayed at the same time, it is possible to detect the BER after the RS and always send the TS to the decoder unit.

  The FFT information output unit 93, the TMCC information output unit 94, the reception power output unit 95, the C / N output unit 96, the BER output unit 97, and the TS output unit 98 described above are information that generates a control signal to be sent to the control unit 9. Can be used as

  5 to 8 are flowcharts showing an example of the operation of the control unit 9. Here, an example is shown in which the bit error rate (BER) and C / N information of the received signal is used for control. In this embodiment, the bit error rate (BER) is used, but a packet error rate (PER) may be used instead of the bit error rate (BER).

  In FIG. 5, when processing is started (STRAT), first, initial values of various parameters necessary for control are set in step S51. Specifically, the period average C / N (1) of the antenna element unit 2 is set to “0”, and the period average C / N (2) of the antenna element unit 3 is set to “3”. Further, the antenna switching determination flag (AF) is set to “True”, the bit error continuous number (BN) is set to “0”, and the antenna switching continuous number (N) is set to “0”. In addition, the receiving antenna is set as a default antenna (for example, the antenna element unit 2). Here, the number of consecutive bit errors (BN) refers to the number of times that the measured bit error rate (BER) has continuously exceeded the threshold value S. For example, when the BER exceeds the threshold value S five times in succession, BN becomes “5”.

  Subsequently, in step S52, it is determined whether or not to execute the antenna switching control. If not (step S52; N), the control is terminated and the normal reception control state is restored. When the antenna switching control is executed (step S52; Y), the antenna switching control is started.

  If the determination flag (AF) is not “True” in step S53 (step S53; N), the process proceeds to the flowchart (B) of the long-term monitor mode. When the determination flag (AF) is “True” (step S53; Y), the process proceeds to step S54.

  In step S54, it is determined whether or not the number of bit errors BN exceeds “5”. When BN is “5” or less (step S54; N), the process proceeds to the flowchart (B) in the long-term monitor mode. When BN is larger than “5” times (step S54; Y), the process proceeds to the flowchart (A) of the short-term switching mode.

  Next, a flowchart (A) in the short-term switching mode will be described with reference to FIG. In the flowchart (A) of the short-term switching mode, first, in step S61, the antenna is switched. When BN is “5” in step S54 of FIG. 5, that is, when the antenna element unit 2 is the antenna in which the state in which the BER is greater than the threshold value S is continuously continued “5” times, the antenna element unit Switch to 3. On the contrary, if the antenna in which the BER is greater than the threshold value S in step S54 in FIG.

  After switching the antenna, in step S62, the reception state with the switched antenna is maintained for a certain time (for example, 1000 milliseconds). Next, in step S63, based on the BER measured again, it is determined whether the BER is equal to or less than a threshold value. If the BER is less than or equal to the threshold value S (step S63; Y), the process proceeds to step S64 to determine which antenna is used for reception.

  In step S64, when receiving by the antenna element unit 2 (step S64; Y), or receiving by the antenna element unit 3, and the period average C / N (1) of the antenna element unit 2 is the antenna element unit. If the period average C / N (2) is smaller than 3 (step S64; Y), the process proceeds to step S65. The bit error continuous number (BN) is set to “0”, the antenna switching continuous number (N) is set to “0” (step S65), and the antenna switching determination flag (AF) is set to “False” (step S66). ), Returning to C in the flowchart of FIG.

  In the case of N in step S63 and step S64, the process proceeds to step S67. In step S67, it is determined whether or not the number N of antenna switching exceeds a predetermined number (for example, “30” times), and if it exceeds the predetermined number (step S67; Y), the process proceeds to step S65. If the number of antenna switching does not exceed the predetermined number (step S67; N), the number of antenna switching N is incremented in step S68, and antenna switching is performed again (step S61).

  Next, the flowchart (B) in the long-term monitor mode will be described with reference to FIG. In the long-term monitor mode, the current receiving antenna is fixed for a certain period. First, an antenna fixed time is set (step S71). For example, “60” seconds are set here. If the antenna fixing time has elapsed (step S72; Y), the antenna switching determination flag (AF) is set to “True” (step S73), and the process returns to the flowchart of C in FIG.

  Next, referring to FIG. 8, a flowchart for obtaining the average period C / N (1) of the antenna element unit 2 and the average period C / N (2) of the antenna element unit 3 used in step S64 of FIG. explain. The flowchart of FIG. 8 operates in parallel with the flowcharts described in FIGS.

  In FIG. 8, first, in step S81, C / N is acquired at intervals of “500 milliseconds”. Next, in step S82, it is determined which antenna is receiving, and if the antenna element unit 2 is receiving (step S82; Y), in step S83, for example, an average C / N for 10 seconds is calculated. Calculate and update the value recorded in the period average C / N (1) of the antenna element section 2. On the other hand, when it is received by the antenna element unit 3 (step S82; N), the average C / N for 10 seconds is calculated in step S84 and recorded in the period average C / N (2) of the antenna element unit 3. Update the value.

  Then, in step S85, it is determined whether or not to end the C / N measurement flowchart. If not (step S85; N), the process returns to step S81. If it is ended (step S85; Y), the C / N measurement is ended. To do.

  In the above control method, information on the number of consecutive bit errors (BN) and C / N is used as a control parameter. Similarly, various parameters shown in FIG. 4, that is, received power, FFT information, TMCC information, TS, etc. Is naturally applicable as a control parameter. Of course, the determination may be made using the bit error rate (BER) of the received data instead of the number of consecutive bit errors (BN).

  The parameters including the number of consecutive bit errors (BN) and C / N are obtained at a later stage in the processing in the demodulator 8 in the front end unit 10 of the digital broadcast receiver 1 in FIG. By controlling with these parameters, more accurate control is possible. That is, C / N can be considered as received power (C: carrier signal) in consideration of the noise level. Therefore, it is possible to perform more accurate control than when the control is performed only with the received power.

  In addition, when the bit error rate (BER) is used, more accurate control is possible than using only the received power, by using BER as a control parameter, as in C / N.

  Also, TS information is video and audio signal information itself, and by setting whether or not this TS information can be obtained as a threshold value, control similar to the above can be performed.

  On the other hand, the information obtained in the earlier stage can shorten the processing time until the information is obtained, so that higher speed control is possible. Specifically, each parameter has the following characteristics.

  The synchronization state in OFDM demodulation can be detected from the FFT information. By setting whether or not the synchronization is lost as a threshold value, the same control as described above can be performed.

  The TMCC information is information related to the demodulation operation of the receiver, such as a hierarchical configuration and transmission parameters of each OFDM segment. By setting whether or not TMCC information has been acquired as a threshold value, control similar to the above can be performed. The TMCC carrier is modulated by the DBQPSK modulation method, and the TMCC information is easier to receive than the information of video and audio signals, and is suitable for control in a harsh reception environment.

  Although these pieces of information may be used and controlled individually, a plurality of pieces of information may be used in combination.

  FIG. 9 is a schematic diagram illustrating a configuration example of the antenna element unit 2 and the antenna element unit 3 of the receiving device 1. 1 is a diagram showing a one-seg TV-compatible mobile phone as an example of a receiving device 1, using a TV receiving whip antenna as the antenna element unit 2, and using an earphone antenna built in the earphone unit 92 as the antenna element unit 3. ing. Instead of the earphone antenna, the mobile phone casing itself can have an antenna function and can be used as the antenna element portion 3.

  As described above, the antenna switching diversity receiver according to the present embodiment includes a housing, a plurality of antennas provided in the housing and receiving radio waves, a switching unit connected to the antenna, A control unit that controls the switching unit based on a signal received by an antenna, and the control unit is controlled by mode switching and antenna switching according to a situation of a signal received through the antenna. By doing so, it is possible to realize an antenna switching diversity receiver capable of reducing unnecessary antenna switching operations.

  Further, according to the antenna switching diversity reception control method of the present invention, the mode switching is composed of the short-term switching mode and the long-term monitoring mode, so that unnecessary antenna switching operation is reduced and the reception status is further improved. There is an advantage that reflected antenna switching diversity reception control becomes possible.

  Further, according to the antenna switching diversity reception control method of the present invention, the antenna switching diversity that more reflects the reception state by making the antenna switching a continuous number of times when the error rate exceeds the threshold in the determination of the antenna switching. There is an advantage that reception control becomes possible.

It is a block diagram which shows the structural example of the receiver by embodiment of this invention. It is a figure which shows the structural example of the antenna element part by the embodiment of this invention, and a switching part. It is a block diagram which shows the detailed structural example of the tuner part by embodiment of this invention. It is a block diagram which shows the detailed structural example of the OFDM demodulation part by embodiment of this invention. It is a flowchart figure explaining an example of operation in a control part by an embodiment of the present invention. It is a flowchart figure explaining an example of operation in a control part by an embodiment of the present invention. It is a flowchart figure explaining an example of operation in a control part by an embodiment of the present invention. It is a flowchart figure explaining an example of operation in a control part by an embodiment of the present invention. It is a figure which shows the example of an external appearance structure by embodiment of this invention. It is a block diagram which shows the structural example of the conventional receiver.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital broadcast receiver 2, 3 Antenna element part 4, 5 Antenna matching part 6 Switching part 7 Tuner part 8 OFDM demodulation part 9 Control part 10 Front end part 11 TS-DEMUX part 12 Video signal processing part 13 Data signal processing part 14 Audio signal processing unit 15 Back end unit 16 Video display unit 17 Audio output unit 71 RF amplifier unit 72 Mixer unit 73 IF filter unit 74 IF amplifier unit 75 PLL unit

Claims (4)

Multiple antennas to receive radio waves,
A switching unit for selecting and switching one antenna from the plurality of antennas;
A control unit for controlling the switching unit,
The control unit controls a timing for switching an antenna selected by the switching unit in accordance with the received radio wave condition.   The timing for switching the antenna is a timing for fixing the antenna selected by the switching unit and switching after a predetermined time, and a timing for switching the antenna by the switching unit according to the received radio wave condition. The receiving device according to claim 1.   The receiving apparatus according to claim 1, wherein the control unit controls timing for switching the antenna selected by the switching unit based on a bit error rate in the received radio wave.   4. The control unit according to claim 1, wherein the control unit performs control to fix the antenna without switching for a predetermined time when the number of times the switching unit is switched by the switching unit becomes a predetermined number or more. The receiving device according to item.

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