JP2008283304A - Broadcast wave reception device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a broadcast wave reception device that can effectively reduce capturing operation made redundant and therefore continue to stably receive the same broadcast content. <P>SOLUTION: The broadcast wave reception device 10 has a plurality of antennas 11 and 12, includes functions 17, 18, and 20 of changing directivities of the antennas by performing adaptive processing on reception signals SG1 and SG2 of a broadcast wave received through the antennas, and further includes means 25, 26, and 27 of detecting an electric field intensity before the adaptive processing and an electric field intensity after the adaptive processing respectively, and a control means 21. When the control means 21 decides that the difference between the detected electric field intensities before and after the adaptive processing is higher than a prescribed threshold for deciding a capturing state, it is decided that the adaptive processing is in error, and then control for initialization and restarting thereof is carried out. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a broadcast wave receiving apparatus, and more particularly to a broadcast wave receiving apparatus suitable for changing the directivity of an antenna by performing adaptive processing on each broadcast wave received signal received via a plurality of antennas.

  Conventionally, in a mobile communication receiving device equipped with an antenna such as an in-vehicle radio receiver, a plurality of broadcast waves of the same frequency may be simultaneously received via the antenna, particularly in an area where there are many plains. there were. FIG. 5 shows, as an example of receiving a plurality of broadcast waves having the same frequency, an RDS (Radio Data System) via an antenna (omnidirectional antenna) of a receiving device 2 mounted on the host vehicle 1. The case where a broadcast is received is shown. The RDS broadcast is a broadcast in which RDS data including an AF list (alternate frequency list), PI (Program Identity), and the like is multiplexed on an FM signal.

  As shown in FIG. 5, there are two broadcast stations ST1 and ST2 (hereinafter referred to as “first broadcast station ST1” and “second broadcast station ST2” for the sake of convenience) within the distance that can be detected by the receiving device 2 of the vehicle 1. Is present). The first broadcasting station ST1 is a desired station that the receiving device 2 of the own vehicle 1 is trying to receive a broadcast, and its broadcasting frequency is f [MHz] and PI is D301. On the other hand, the second broadcast station ST2 is an interfering station, and its broadcast frequency is the same f [MHz] as the first broadcast station ST1, and the PI is D302.

  Here, even when the first broadcast station ST1 is a nearby station and the second broadcast station ST2 is a distant station with respect to the own vehicle 1, the output of the second broadcast station ST2 is higher than the output of the first broadcast station ST1. If it is high, the reception level of both broadcast stations ST1 and ST2 in the receiving device 2 of the own vehicle 1 may be approximately the same in a region with good visibility such as a plain.

  Further, the output level of the first broadcast station ST1 and the output level of the second broadcast station ST2 are approximately the same, and the first broadcast station ST1 and the second broadcast station ST2 are moved along with the movement of the host vehicle 1. When there is an area having the same distance from the own vehicle 1, the reception levels of both broadcast stations ST <b> 1 and ST <b> 2 in the receiving device 2 of the own vehicle 1 may be almost the same in the area. .

  Further, as illustrated in FIG. 6, even when the first broadcast station ST1 is a nearby station and the second broadcast station ST2 is a distant station with respect to the own vehicle 1, the first broadcast station ST1 and the own vehicle 1 In the area where the shielding object OB exists between the two broadcasting stations ST1 and ST2 in the receiving device 2 of the own vehicle 1, as a result, the reception level of the first broadcasting station ST1 is relatively lowered by the shielding object OB. May have the same reception level.

  In this way, the broadcast wave of the desired station (first broadcast station ST1) and the broadcast wave of the interfering station (second broadcast station ST2) are received simultaneously, and the reception levels of both broadcast stations ST1 and ST2 are the same. It is known that a phenomenon unique to FM broadcasting called a so-called capture phenomenon (capture operation) occurs when there is an area having the same level. In other words, the broadcast wave of the first broadcast station ST1 and the broadcast wave of the second broadcast station ST2 having the same frequency are simultaneously received by the antenna (omnidirectional antenna) of the receiving device 2 of the own vehicle 1, and these two waves Are mixed and input to the FM detector, as shown in FIG. 7, the FM detector demodulates the signal of the broadcasting station having the stronger electric field strength of the two mixed waves (received signals). Resulting in. Such a capture operation causes a problem that it is impossible to continue listening to broadcasts having the same content, and therefore an effective solution has been demanded.

  Conventionally, in a receiving device for mobile communication, a signal superimposed and transmitted from a broadcasting station is reflected and diffracted due to obstacles such as a building or terrain, so that the receiving device has multiple paths (multipath). As a result of receiving the same broadcast wave signal from), noise may be generated in the received signal, or the encoded signal may not be decoded.

  Therefore, in order to reduce the influence of such multipath, a receiving apparatus including an adaptive-array antenna having a plurality of antennas has been adopted. In a receiving apparatus equipped with such an adaptive array antenna, by performing adaptive processing for controlling the phase and gain of the received signal with respect to the received signal, the antenna can have directivity and the directivity can be changed. It has become. As a result, directivity can be directed only in the direction of arrival of the desired wave, and a zero point (null) can be directed in the direction of arrival of non-desired waves such as delayed waves, resulting in multipath. It was possible to reduce the influence of.

  However, in a receiving apparatus equipped with such an adaptive array antenna, directivity is generated in the antenna when performing adaptive processing on the received signal, so that the directivity is not given to the broadcasting station that is not the desired station. In some cases, the above-described capture operation becomes redundant. That is, the adaptive array antenna directs directivity only in the direction of arrival of the desired wave based on adaptive processing. When the desired wave is a broadcast wave of the desired station, direct the directivity to the desired station. Thus, a control algorithm that maximizes the gain and minimizes the reception level by directing a zero point (null) to a broadcasting station (such as an interfering station) other than the desired station works.

  However, the adaptive array antenna may fix the directivity to broadcast stations other than the desired station, particularly when receiving a broadcast wave of the same reception level, particularly by an operation that maximizes the gain. There has been a cause of making the above-described capture operation redundant. For example, in the case of the first broadcast station ST1 and the second broadcast station ST2 shown in FIGS. 5 and 6, the reception level of the first broadcast station ST1 and the reception level of the second broadcast station ST2 are approximately the same. In certain areas, the directivity may be fixed to the second broadcasting station ST2 by the adaptive processing. As a result, as illustrated in FIG. 8, the reception electric field strength with respect to the second broadcasting station ST2 is increased, the capture operation is made redundant, and the reception range of the second broadcasting station ST2 that is an interfering station is expanded. It was.

As measures against such a capture operation, for example, as described in Patent Document 1, when a jamming station broadcast is received by a capture operation, the same broadcast content as the desired station is desired. There has been proposed an RDS receiver intended to continue receiving the same broadcast content by switching reception to an alternative station that is broadcasting at a different frequency (alternate frequency) from the station. As another technique related to this, for example, as described in Patent Document 2, when a broadcast of a disturbing station is received by a capture operation, it is determined that there is an error in adaptive processing for a received signal. There has also been proposed a receiving apparatus that performs control for initializing and restarting the adaptive processing.
Japanese Utility Model Publication No. 5-21530 JP 2006-238295 A

  As described above, in an apparatus for receiving a conventional RDS broadcast (FM broadcast wave), various measures have been taken to cope with the problem of the capture phenomenon (capture operation), but there are still effective proposals. The fact was not made.

  For example, even in the receiver described in Patent Document 1 above, when an alternative station broadcasting the same broadcast content as the desired station cannot be found, or the desired station is a local station and the alternative station itself does not exist In this case, the capture operation is still affected.

  On the other hand, the technique previously proposed by the applicant of the present application (the receiving apparatus described in Patent Document 2 above) discloses one effective technique for the capture operation. The receiving device disclosed here detects discrimination information (PI of RDS data included in the signal) for identifying the broadcast station that transmitted the broadcast wave from the received broadcast wave signal, and the discrimination If the broadcast station specified based on the information is not the desired station, it determines that there is an error in the adaptation process currently being performed, and initializes / restarts the adaptation process to direct the station to the desired station. The directivity of the antenna is corrected so as to be suitable, so that erroneous channel selection can be resolved reliably and promptly.

  The present invention was created in view of the above-mentioned problems of the prior art, and can effectively reduce redundant capture operations by an approach different from the method previously proposed by the applicant (Patent Document 2). An object of the present invention is to provide a broadcast wave receiving apparatus capable of stably receiving the same broadcast content.

  In order to solve the above-described problems of the prior art, according to the present invention, the adaptive processing is performed on each reception signal of a broadcast wave received from a broadcast station via the plurality of antennas. A broadcast wave receiving apparatus having a function of variably changing the directivity of the antenna, the first detecting means for detecting the electric field strength before the adaptive processing, and the second detecting means for detecting the electric field strength after the adaptive processing. The difference between the electric field intensities is higher than a predetermined threshold value for determining the capture status from the detection means and the detection signals indicating the electric field intensities detected by the first and second detection means, respectively. And a control means for performing control for initializing / restarting the adaptive process by determining that the adaptive process has an error when detected. The

  According to the broadcast wave receiving apparatus of the present invention, for each received signal of broadcast waves received via a plurality of antennas, the electric field strength before adaptive processing and the electric field strength after adaptive processing are detected and the difference between them is detected. If this difference is higher than a predetermined threshold for determining the capture status, it is determined that there is an error in the adaptive processing (that is, the capture operation is in a redundant state). The initialization and restart are performed. By initializing / restarting such adaptive processing, redundant capture operations can be effectively reduced, and as a result, the same broadcast content can be received stably.

  Other structural features of the broadcast wave receiving apparatus according to the present invention and specific operations, processes, and the like based thereon will be described with reference to embodiments of the invention described below.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.

  FIG. 1 schematically shows a part of the configuration of a broadcast wave receiving apparatus according to an embodiment of the present invention. In the present embodiment, it is assumed that the receiving apparatus is mounted on a vehicle as a moving body illustrated in FIGS. 5 and 6 and a plurality of broadcast waves having the same frequency are simultaneously received via an antenna. .

  As shown in FIG. 1, the broadcast wave receiving apparatus 10 according to the present embodiment includes two antennas 11 and 12 (for convenience, a “first antenna 11” and a “second antenna 12”) that constitute an adaptive array antenna. Called). The first antenna 11 and the second antenna 12 receive an FM signal transmitted from a broadcast station as a received signal, and output the received signal to the inside of the receiving apparatus. The received signal in this embodiment is a signal in which RDS data is multiplexed on an FM signal, but is not limited to this.

  A mixer 13 (referred to as “first mixer 13” for the sake of convenience) is connected to the output side of the received signal with respect to the first antenna 11, and this first mixer 13 is output from the first antenna 11. Received signals are input. Also, a mixer 14 (referred to as “second mixer 14” for convenience) is connected to the output side of the received signal with respect to the second antenna 12, and the output from the second antenna 12 is connected to the second mixer 14. The received signal is input.

  A local oscillator 15 is connected to the first mixer 13 and the second mixer 14, and the local oscillator 15 oscillates a local oscillation signal having a predetermined frequency. The first mixer 13 reduces the frequency of the reception signal to an intermediate frequency by mixing (mixing) the local oscillation signal input from the local oscillator 15 and the reception signal input via the first antenna 11. At the same time, a reception signal SG1 with a reduced frequency (the signal level is L1) is output. Thereby, the reception signal SG1 output from the first mixer 13 can be stably processed. Similarly, the second mixer 14 mixes (mixes) the local oscillation signal input from the local oscillator 15 and the reception signal input via the second antenna 12, thereby changing the frequency of the reception signal to an intermediate frequency. And a reception signal SG2 with a reduced frequency (the signal level is L2) is output. Thereby, the received signal SG2 output from the second mixer 14 can be stably processed.

  Further, a weighting unit 17 (referred to as “first weighting unit 17” for convenience) is connected to the output side of the received signal with respect to the first mixer 13, and the first mixer 17 is connected to the first mixer 13. The reception signal SG1 output from 13 is input. The first weighting unit 17 has the same configuration and function as an equalizer (FIR filter) that is generally used in the field of adaptive signal processing, and receives the received signal SG1 input from the first mixer 13. The weighting is performed according to the weighting coefficient variably set for the phase and gain, and the weighted reception signal is output.

  Similarly, a weighting unit 18 (referred to as a “second weighting unit 18” for convenience) is connected to the output side of the received signal with respect to the second mixer 14, and the second weighting unit 18 includes a second weighting unit 18. The reception signal SG2 output from the mixer 14 is input. The second weighting unit 18 has the same configuration and function as the first weighting unit 17, and uses a weighting coefficient that is variably set with respect to the phase and gain of the reception signal SG <b> 2 input from the second mixer 14. The weighting is performed in accordance with the weight, and the weighted reception signal is output.

  In this way, by weighting the reception signals SG1, SG2 by the first weighting unit 17 and the second weighting unit 18, the phase and gain of each reception signal SG1, SG2 are variably set to values according to the weighting factors, The directivity (that is, the radiation pattern) of the antennas 11 and 12 is formed.

  Further, an adder 19 is connected to the output side of the reception signal with respect to the first weighting unit 17 and the second weighting unit 18, and the reception signal output from the first weighting unit 17 is connected to the adder 19. The reception signal output from the second weighting unit 18 is input. The adder 19 adds the reception signal input from the first weighting unit 17 and the reception signal input from the second weighting unit 18, and adds the received signal SG3 (the signal level is L3). ) Is output.

  Furthermore, an adaptive processing unit 20 is connected to the output side of the received signal with respect to the adder 19. The adaptive processing unit 20 receives the received signal SG3 output from the adder 19 and The reception signal output from the first weighting unit 17 and the reception signal output from the second weighting unit 18 are respectively input. The adaptive processing unit 20 receives the received signal SG3 input from the adder 19 and the received signals input from the first weighting unit 17 and the second weighting unit 18 based on control from the control unit 21 described later. In comparison, a weighting factor for the optimum phase and gain to be set in the first weighting unit 17 and the second weighting unit 18 is determined, and the determined weighting factor is sent to the first weighting unit 17 and the second weighting unit 18. Each is set. At this time, the weighting coefficient set by the adaptive processing unit 20 is optimally optimized according to changes in each received signal input to the adaptive processing unit 20 by using an adaptive algorithm such as LMS (Least Mean Square), for example. It is updated to a new value.

  As a result, the phase and gain of the reception signals SG1 and SG2 can be changed to optimum values as the weighting factor is updated, and the antenna directivity can be corrected to the optimum state. That is, the first weighting unit 17 and the second weighting unit 18 perform adaptive weighting by changing the phase and gain of the received signals SG1 and SG2 according to the weighting factor set by the adaptive processing unit 20, respectively. An adaptive process for the received signal by the processing unit 20 can be performed.

  As specific contents of the adaptive processing, for example, when the received signal includes noise such as a received signal received from a broadcasting station (such as an interfering station) other than the desired station, the noise is minimized. For this purpose, an optimum weighting factor is set. As a result, the signal level in the direction of arrival of the received signal including the noise that becomes the interference can be attenuated. In addition, for example, when no noise is included in the received signal, an optimum weighting factor may be set to maximize the signal level of the received signal. By performing the adaptive process in this way, various directivities (radiation patterns) corresponding to the weighting factors are formed on the first antenna 11 and the second antenna 12.

  Further, an FM detection processing unit 22 is connected to the output side of the reception signal with respect to the adder 19, and the reception signal SG <b> 3 output from the adder 19 is input to the FM detection processing unit 22. It has become. The FM detection processing unit 22 acquires an audio signal by detecting the input reception signal SG3, and outputs the acquired audio signal. The sound signal output from the FM detection processing unit 22 is output as a sound through a sound output system such as a speaker (not shown).

  Further, an RDS data processing unit 23 is connected to the output side of the FM detection processing unit 22, and this RDS data processing unit 23 performs detection processing in the FM detection processing unit 22 based on control from the control unit 21 described later. RDS data including PI (Program Identity) is acquired from the received signal. The acquired RDS data is output to the control unit 21, and the control unit 21 can detect the broadcasting station that transmitted the received signal by detecting the PI from the RDS data.

  Further, on the output side of the received signal with respect to the first mixer 13 (the input side of the first weighting unit 17), the electric field intensity detection unit 25 characterizing the present invention (for convenience, referred to as “first electric field intensity detection unit 25”). The first electric field strength detector 25 is for detecting the electric field strength (signal level L1) of the received signal SG1 to be input to the first weighting unit 17. Similarly, an electric field strength detector 26 (referred to as “second electric field strength detector 26” for convenience) is also connected to the output side of the received signal (the input side of the second weighting unit 18) with respect to the second mixer 14. The second electric field strength detection unit 26 is for detecting the electric field strength (signal level L2) of the reception signal SG2 to be input to the second weighting unit 18. As will be described later, the detection signals indicating the signal levels L1 and L2 detected by the first electric field intensity detection unit 25 and the second electric field intensity detection unit 26 are improved by the control unit 21 to improve redundant capture operations. It is used when performing such processing.

  Further, an electric field intensity detector 27 (referred to as “third electric field intensity detector 27” for convenience) that characterizes the present invention is connected to the adder 19 on the output side of the received signal. The intensity detector 27 receives the received signal SG3 output from the adder 19 (that is, after the adaptive processing is performed on the received signals SG1 and SG2 through the first weighting unit 17 and the second weighting unit 18, the adder 19 This is for detecting the electric field strength (signal level L3) of the combined received signal). The detection signal indicating the detected signal level L3 is sent to the control unit 21 together with the detection signals indicating the signal levels L1 and L2, and is used when performing processing related to the redundant capture operation improvement. The

  Further, a switching processing unit 28 is connected to the control unit 21, and the switching processing unit 28 is connected to the first weighting unit 17 and the second weighting unit 18 based on control from the control unit 21 as described later. On the other hand, by setting specific weighting factors (phase and gain), either one of the reception signal SG1 output from the first mixer 13 and the reception signal SG2 output from the second mixer 14 is selectively output. It has become. That is, the switching processing unit 28 functions when the adaptive processing unit 20 is not functioning. In the present embodiment, specific weighting factors set for the first weighting unit 17 and the second weighting unit 18 are set as follows.

  That is, as shown in FIG. 4B as an example, the phase (φ) is fixed to φ = 0 because the received signals SG1 and SG2 are not combined. The gain (G) is set to G = 0 (or −∞) for the first weighting unit 17 and G = −∞ (or 0) for the second weighting unit 18. Thus, only one received signal SG1 (or SG2) is selectively output. In this case, which reception signal SG1 (or SG2) is selectively output is determined based on the control signal output from the control unit 21. This control signal is generated based on the result determined to be “larger” of the signal levels L1 and L2 detected by the first electric field intensity detection unit 25 and the second electric field intensity detection unit 26, respectively. That is, a specific gain (G) is set for each of the first weighting unit 17 and the second weighting unit 18 via the switching processing unit 28 based on the control signal from the control unit 21, and is output to the subsequent circuit. A received signal to be received (a signal having a higher electric field strength) can be switched.

  The control unit 21 is for controlling the entire receiving apparatus 10, and as processing related to the present invention, redundant processing is performed in cooperation with the adaptive processing unit 20 and the switching processing unit 28 as described later. A process for reducing the capture operation is controlled.

  In the broadcast wave receiving apparatus 10 of the present embodiment configured as described above, the control unit 21 is a “control unit”, and the first electric field strength detection unit 25 and the second electric field strength detection unit 26 are “first detection unit”. The third electric field strength detection unit 27 corresponds to the “second detection unit”, and the switching processing unit 28 corresponds to the “switching unit”.

  Next, FIG. 2 shows an example of processing related to improvement of redundant capture operations performed by the control unit 21 in cooperation with the adaptive processing unit 20 and the switching processing unit 28 in the broadcast wave receiving apparatus 10 of the present embodiment. This will be described with reference to FIG. In addition, a supplementary explanation will be given with reference to FIG.

  First, as an initial state, it is assumed that a vehicle on which the receiving device 10 is mounted is moving. Further, it is assumed that one of the “adaptive processing” by the adaptive processing unit 20 and the “switching processing” by the switching processing unit 28 is performed based on the control from the control unit 21. As shown in FIG. 4A, the adaptive processing is performed on the first weighting unit 17 and the second weighting unit 18 via the adaptive processing unit 20, respectively, with weighting factors (φ = arbitrary, This is done by setting G = arbitrary). On the other hand, as shown in FIG. 4B, the switching process is performed on the first weighting unit 17 and the second weighting unit 18 via the switching processing unit 28, respectively, with weighting coefficients (φ = 0, G = 0 or -∞).

  In such a state, in the first step S1, in the control unit 21, from the reception signals SG1 and SG2 detected by the first electric field intensity detection unit 25 and the second electric field intensity detection unit 26, the respective signal levels L1 and L2 The larger one is selected, and the selected signal level (electric field strength) is set as the signal level L of the reception signal SG1 (or SG2) before the adaptive processing.

  In the next step S2, the control unit 21 determines whether the set signal level L is lower (YES) or not (NO) than a predetermined threshold A for determining a weak electric field. That is, it is determined whether or not the vehicle equipped with the receiving device 10 is traveling in a weak electric field area. In this embodiment, “detection” and “release” of the weak electric field are performed in a range of about 10 to 20 dBμV, and a hysteresis of about 6 dBμV is set between the detection level and the release level in order to prevent unnecessary detection repetition. ing. Therefore, as the threshold value A used as the determination reference value in this step, for example, the detection level is set to 12 dBμV, and the release level is set to 18 dBμV. If the determination result is YES, the process proceeds to step S3, and if the determination result is NO, the process proceeds to step S4.

  In step S3 (when traveling in a weak electric field area), the process proceeds to “switching process” by the switching processing unit 28 based on the control from the control unit 21. Then, this processing flow is “end”.

  At this time, if “adaptive processing” is being performed as an initial state, the adaptive processing unit 20 is stopped based on the control from the control unit 21 and simultaneously the switching processing unit 28 is processed. The process is started. Further, if the “switching process” is being performed as an initial state, the switching process unit 28 continues the process as it is based on the control from the control unit 21. As described above, the reason why the “switching process” is performed in the weak electric field region is that when the “adaptive process” is performed, the signal-to-noise (S / N) ratio expected by combining the two reception signals SG1 and SG2 is improved. This is because the effect of is not great in practical use.

  On the other hand, in step S4, the control unit 21 determines whether the “adaptive process” is currently being performed (YES) or not (NO). When the determination result is YES, the process proceeds to step S5, and when the determination result is NO (that is, when the “switching process” is performed), the process proceeds to step S9.

  In step S5 (when “adaptive processing” has already been performed), the control unit 21 detects the signal level L (electric field strength before adaptive processing) set in step S1 and the third electric field strength detection unit 27. The difference between the received signal SG3 and the signal level L3 (the electric field strength after adaptive processing) is calculated, and this difference (L-L3) is higher than a predetermined threshold B for determining the capture status (YES) ) Or not (NO). In other words, the magnitude relationship between the electric field strengths before and after the adaptive processing is reversed (that is, the signal components after the adaptive processing are in spite of the fact that the electric field strength of the receiving station is greater than the desired station> the desired station). The signal component of the desired station is attenuated and the desired station is less than the desired station (the situation where the capture operation is redundant) occurs, and the electric field strength after adaptive processing is the electric field strength before adaptive processing. It is judged whether it is in a state greatly lowered compared with. In other words, it is determined whether there is an error in the adaptive processing currently being performed. In the present embodiment, it is assumed that the capture phenomenon occurs when the difference in electric field strength between the received signal of the desired station and the received signal of the undesired station is in the range of about 0 to 15 dB. Accordingly, in this step, the predetermined threshold value B is set within a range of about 10 to 20 dB (for example, 15 dB) in order to detect an operation that reverses the operation. If the determination result is YES, the process proceeds to step S6, and if the determination result is NO, the process flow is “end”.

  In the next step S <b> 6, a “process switching” process is performed based on the control from the control unit 21. This “process switching” process will be described later with reference to FIGS.

  In the next step S7, whether or not the interference signal included in the received signal has increased from the received signal SG3 detected by the third electric field intensity detecting unit 27 in the control unit 21 (YES). Determine whether. That is, it is determined whether or not the ratio of the disturbing signal in the received signal has increased before and after the “process switching” process performed in the previous step S6. If the determination result is YES, the process proceeds to step S8, and if the determination result is NO, the process flow ends.

  In the next step S8 (when the interference signal is increasing), before performing the “process switching” process performed in step S6 on the adaptive processing unit 20 or the switching processing unit 28 based on the control from the control unit 21. The process for returning to the set value is performed. Then, this processing flow is “end”.

  On the other hand, in step S9 (when the “switching process” is performed as an initial state), the control unit 21 continues the “switching process” measured by the timer based on the function of a built-in timer (not shown). It is determined whether the time Ts is longer (YES) or not (NO) than a predetermined threshold (setting time C for switching process continuation) for determining whether the switching process should be continued as it is. That is, it is determined whether to continue the “switching process” or to return to the “adaptive process” based on the duration Ts of the “switching process”. In the present embodiment, assuming that the traveling speed of the vehicle is 40 km / H, an operation in an area of about 50 m is assumed, and, for example, about 5 seconds is set as the set time C for switching processing. If the determination result is YES, the process proceeds to step S10. If the determination result is NO, the determination process is repeated (that is, the “switching process” is continued).

  In the next step S10 (when the duration of the “switching process” exceeds a predetermined time), the “adaptive process” is restarted via the adaptive processing unit 20 based on the control from the control unit 21 (“adaptive process”). Return to). Then, this processing flow is “end”.

  Next, the “process switching” process performed in step S6 will be described with reference to FIGS.

  In this processing flow, as an initial state, “adaptive processing” by the adaptive processing unit 20 is performed based on control from the control unit 21, and it is determined that there is an error in the adaptive processing. The “process switching” process here refers to “switching” between the process for initializing / restarting the adaptive process and the switching process by the switching processing unit 28. This determination of “switching” is performed based on the number of times this “process switching” process has been performed within a certain fixed time in the past. For this reason, the memory (not shown) built in the control unit 21 stores information on the number of times “process switching” (= N) is performed within a predetermined time, and is updated in the course of processing. It has become.

  In such a state, in the first step S11, the control unit 21 counts up (+1) the value of the “process switching” execution count N.

  In the next step S12, the control unit 21 determines whether or not the number N of times counted up is smaller (YES) or not (NO) than a predetermined set value D. In other words, when the number of “process switching” processes performed within a certain fixed time in the past is relatively small, it is highly possible that redundant capture operations can be avoided if adaptive processing is performed again. On the other hand, when the number of “process switching” processes is relatively large, it is assumed that there are many cases where the capture operation cannot be avoided even if the adaptive process is initialized and restarted. Therefore, in this step, it is determined whether the “adaptive processing” should be initialized or restarted or “switching processing” should be performed based on the “process switching” execution count N. In the present embodiment, in order to set the frequency that does not give the user a sense of incongruity, the set value (number of times) D is set to, for example, about 3 times in about 10 seconds. If the determination result is YES, the process proceeds to step S13, and if the determination result is NO, the process proceeds to step S14.

  In step S13, since it is determined that there is an error in the adaptive processing that is currently being executed to the adaptive processing unit 20 based on the control from the control unit 21, a command for performing the “adaptive processing” again. Is output (initialization / restart). That is, as shown in FIG. 4A, the weighting coefficient for the optimum phase and gain is reset for the first weighting unit 17 and the second weighting unit 18 via the adaptive processing unit 20. Then, this processing flow is “end”.

  On the other hand, in step S14, similarly to the process performed in step S3 (FIG. 2), the process proceeds to the “switching process” by the switching processing unit 28 based on the control from the control unit 21. That is, based on the control from the control unit 21, the adaptive processing unit 20 stops the process and the switching processing unit 28 starts the process (see FIG. 4B).

  In the next step S15, the control unit 21 resets the value of the number “N” of “process switching” performed so far to “0”. Then, this processing flow is “end”.

  As described above, according to the configuration of the broadcast wave receiving apparatus 10 according to the present embodiment (FIG. 1), the reception signals SG1 and SG2 of the broadcast waves received via the first antenna 11 and the second antenna 12 are used. On the other hand, the first electric field strength detector 25 and the second electric field strength detector 26 detect the electric field strength (signal levels L1 and L2) before the adaptive processing, respectively, and the third electric field strength detector 27 after the adaptive processing. The electric field strength (signal level L3) is detected, and the control unit 21 obtains a difference between the larger signal level L of the signal levels before the adaptive processing and the signal level L3 after the adaptive processing. When it is determined that L3) is higher than the predetermined threshold value B for determining the capture status, there is an error in the adaptive processing currently being performed (that is, the capture operation is in a redundant state) That) has determined that (step S5 in FIG. 2).

  Then, when this determination is made, based on the control from the control unit 21, the adaptive processing unit 20 is controlled to execute (initialize / restart) the adaptive processing again (step S13 in FIG. 3). Alternatively, based on control from the control unit 21, the switching processing unit 28 is caused to perform "switching processing" for selectively outputting one of the reception signals SG1 and SG2. By performing such initialization / restart of adaptive processing or “switching processing”, redundant capture operations can be effectively reduced. As a result, the same broadcast content can be received stably.

  In the embodiment described above, the case where the broadcast wave receiving apparatus according to the present invention is applied to a vehicle is described as an example. However, as apparent from the gist of the present invention, the scope of application of the present invention is not necessarily limited to a vehicle. Of course not. In short, an adaptive array antenna (antennas 11 and 12) and an adaptive processing function (weighting units 17 and 18, adder 19 and adaptive processing unit 20) are provided, and the electric field strength (signal level L1, L1) before the adaptive processing is further provided. L2) and means for detecting the electric field strength (signal level L3) after the adaptive processing (electric field strength detectors 25 to 27), and means for determining whether there is an error in the adaptive processing from each detected electric field strength The present invention can be applied in the same manner as long as the configuration of the receiving device including the (control unit 21).

  Further, in the above-described embodiment, the case where the number of antennas constituting the adaptive array antenna is two (antennas 11 and 12) has been described as an example for simplification of explanation, but it is also apparent from the gist of the present invention. Of course, the number of antennas is not limited to two, but may be three or more.

It is a block diagram which shows a part of structure of the broadcast wave receiver which concerns on one Embodiment of this invention typically. FIG. 2 is a flowchart showing an example of processing related to improvement of redundant capture operations performed by a control unit in cooperation with an adaptive processing unit and a switching processing unit in the receiving apparatus of FIG. 1. FIG. 3 is a flowchart showing an example of a “process switching” process performed in step S6 in the process flow of FIG. FIG. 4 is a supplementary explanatory diagram of the processing flow of FIG. 3. It is a figure for demonstrating an example in case the receiver mounted in a mobile body receives the some broadcast wave of the same frequency. It is a figure for demonstrating the other example in case the receiver mounted in a mobile body receives the some broadcast wave of the same frequency. It is a figure which shows the relationship between the received electric field strength and the fluctuation | variation of a demodulation audio | voice in the receiver provided with the omnidirectional antenna. It is a figure which shows the relationship between the received electric field strength and the fluctuation | variation of a demodulation audio | voice in the receiver provided with the adaptive array antenna.

Explanation of symbols

10 ... broadcast wave receiver,
11, 12 ... (first and second) antennas,
13, 14 ... (first and second) mixers,
17, 18 ... (first and second) weighting units,
19 ... adder,
20 ... adaptive processing unit,
21 ... control unit (control means),
22 ... FM detection processing unit,
23 ... RDS data processing unit,
25, 26 (first and second) electric field intensity detection units (first detection means),
27 (third) electric field intensity detection unit (second detection means),
28 ... switching processing unit (switching means),
SG1, SG2 ... received signals before adaptive processing,
SG3: Received signal after adaptive processing,
L1 to L3: Signal level (electric field strength).

Claims (6)

Broadcast wave reception having a plurality of antennas and having a function of variably changing the directivity of the antennas by performing adaptive processing on each received signal of broadcast waves received from a broadcast station via the plurality of antennas A device,
First detection means for detecting electric field strength before adaptive processing;
A second detecting means for detecting the electric field strength after the adaptive processing;
When it is detected from the respective detection signals indicating the electric field strengths respectively detected by the first and second detection means that the difference between the electric field strengths is higher than a predetermined threshold value for determining the capture status And a control means for performing control for initializing and restarting the adaptive process when it is determined that there is an error in the adaptive process. Furthermore, it comprises switching means for selectively outputting any one of the received signals of the broadcast waves received via the plurality of antennas,
The broadcast wave receiving apparatus according to claim 1, wherein the control unit causes the switching unit to function when the adaptive processing is not performed.   When the control means detects that the difference between the electric field strengths detected by the first and second detection means is higher than the predetermined threshold when the adaptive processing is performed, 3. The broadcast wave receiving apparatus according to claim 2, wherein the switching unit is made to function instead of performing control for initializing / restarting the adaptive processing.   When the switching process by the switching unit is performed, the control unit stops the function of the switching unit and returns to the adaptive process when the duration of the switching process exceeds a set time. The broadcast wave receiving apparatus according to claim 2, wherein control is performed.   The control means causes the switching means to function when it is determined that the electric field intensity detected by the first detection means is lower than a predetermined threshold value for determining a weak electric field. The broadcast wave receiver according to claim 2.   The broadcast wave receiving apparatus according to claim 1, wherein the broadcast wave receiving apparatus is mounted on a vehicle.

Images