Space diversity receivers

Abstract: A space diversity receiver comprises a plurality of antenna connectors (11A-D), with each of which an antenna (12A-D) is to be connected, a signal selecting portion (47-54, 15A-D) for selecting one of signals from the antenna connectors (11A-D), a signal processing circuit block (30) for producing an output signal based on a signal selected by the signal selecting portion (47-54, 15A-D), wherein a signal sampling operation through which the signals obtained from the antenna connectors (11A-D) are sampled for every short period to be supplied to the signal processing circuit block (30) is performed by the signal selecting portion (42, 43) during a specific period so as to select one of the antenna connectors (11A-D) through which a signal giving rise to the best output signal of the signal processing circuit block (30) is introduced and the signal introduced through the selected antenna connector (11A-D) is continuously selected by the signal selecting portion (47-54, 15A-D) during a period successive to the specific period, the signal selecting portion (47-54, 15A-D) being controlled to perform the signal sampling operation in such a manner that noise components in the output signal of the signal processing circuit block (30) resulted from the signal sampling operation are effectively reduced.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to space diversity receivers, and more particularly, to an improved space diversity receiver which has at least two antennas spaced from each other and is operative to select the best one of signals received respectively by the antennas to obtain reproduced video and/or audio signals therefrom. Description of the Prior Art In a television broadcast signal receiving system provided in an automobile, it is prevalent to use a space diversity receiver since the location of the receiver changes over a relatively broad area and the intensity of the electric field of a television broadcast signal varies quite frequently. The space diversity receiver used in the automobile is accompanied with, for example, four antenna connectors mounted on middle and rear parts of each of left and right sides of a cabin portion each to be coupled with an antenna. In such a space diversity receiver, during a specific period corresponding to, for example, a beginning portion of a vertical blanking period of the television broadcast signal to be received, output signals of a signal processing circuit block produced respectively based on signals obtained from the antenna connectors are compared in quality with one another to select one of the antenna connectors through which a signal giving rise to the best output signal of the signal processing circuit block is introduced, and then during a period successive to the specific period, the signal introduced through a selected antenna connector is supplied to the signal processing circuit block. The signal processing circuit block produces a received signal output based on the signal introduced through the selected antenna connector, from which reproduced video and audio signals are produced. In the space diversity receiver as described above, the signal obtained from the antenna connector constitutes an antenna output signal when an antenna is connected with the antenna connector. However, it is not so rare practically that four antenna connectors are not provided with respective antennas, but some, for example, three of them are provided with respective antennas. In such a case, the signal obtained from the antenna connector with which any antenna is not connected does not constitute the antenna output signal. When one of four antenna connectors, through which the signal giving rise to the best output signal of the signal processing signals obtained respectively from four antenna connectors are selectively sampled for every predetermined short period to be successively supplied to the signal processing circuit block without checking whether four antenna connectors are provided with respective antennas or not. In the signal processing circuit block, output signals are produced based on the sampled signals, respectively, and compared with one another so as to determine the best output signal. Under a condition wherein the signal sampling operation is performed as described above, the output signals of the signal processing circuit block is derived to be interconnected with a discontinuous portion between each successive two so as to produce a received signal output. Since the signal sampling operation is performed in, for example, the vertical blanking period of the television broadcast signal to be received, no substantial trouble or problem is brought about on a picture.produced in accordance with the reproduced video signal which is obtained based on the received signal output derived from the signal processing circuit block even if the received signal output derived from the processing circuit block contains the discontinuous portions therein. However, in respect of a sound produced in accordance with the reproduced audio signal which is obtained based on the received signal output derived from the signal processing circuit block, there is a disadvantage that harsh noise occurs in response to each discontinuous portion contained in the received signal output derived from the signal processing circuit block. Accordingly, it is desired that the signal sampling operation for selecting the antenna connector through which the signal giving rise to the best output signal of the signal processing circuit block is performed minimum times under the necessity in order to suppress the harsh noise contained in the sound produced in accordance with the reproduced audio signal. Further, in the case where the signals obtained respectively from four antenna connectors, at least one of which is not provided with the antenna, are subjected to the signal sampling operation, the signal processing circuit block cannot produce a correct output signal thereof during a short period in which the signal obtained from the antenna connector with which the antenna is not provided is supplied thereto and therefore the received signal output is intermittently derived form the signal processing circuit block to include lacking portions. A sound produced in accordance with the reproduced audio signal obtained based on such a received signal output as to include the lacking portions contains also harsh noise resulting from the lacking portions of the received signal output. Patent Abstracts of Japan Vol. 10, No. 145 (E-407) (2202) 28/5/86 and in the corresponding JP-A-61 5 634 disclose a space diversity receiver for receiving broadcast signals comprising a plurality of antenna connectors, with each of which an antenna is to be connected, signal selecting means for selecting one of signals obtained respectively from the antenna connectors, signal processing circuit means operative to produce an output signal based on a signal selected by the signal selecting means, signal sampling control means operative to cause the signal selecting means to perform a signal sampling operation through which the signals obtained respectively from the antenna connectors are selectively sampled for every predetermined short period to be supplied to the signal processing circuit means during a predetermined specific period, antenna connector selecting means operative to compare in quality the output signals of the signal processing circuit means obtained successively based on signals sampled through the signals sampling operation performed by the signal selecting means with one another in order to select one of the antenna connectors through which a signal giving rise to the best output signal of the signal processing circuit means is introduced during said predetermined specific period, signal selecting control means operative to cause the signal selecting means to select the signal introduced through the antenna connector selected by the antenna connector selecting means during a period successive to said predetermined specific period. In Patent Abstracts of Japan Vol. 9, No. 315 (E-365) (2038) 11/12/85 and in the corresponding JP-A-60 148 236 a diversity receiver for receiving broadcast signals is disclosed, in which the optimum timing of the antenna selecting operation is controlled in response to the speed of a car carrying said diversity receiver. The diversity receivers disclosed in the above identified documents suffer the problems discussed above. Particularly, in the case where one of the antenna connectors is not provided with an antenna, the signal processing circuit block of the respective receiver can not produce a correct output signal. In Patent Abstracts of Japan Vol. 16, No. 73 (E-1169) 21/2/92 and in the corresponding JP-A-32 62 338 a space diversity receiver for receiving broadcast signals is disclosed, which comprises antenna occupancy checking means operative to detect one or more of the antenna connectors with which the antenna is not connected on the basis of the reception electric field and to cause the signal sampling operation in the signal selecting means not to sample the signal obtained from the antenna connector detected by said antenna occupancy checking means as being absent. This receiver suffers the problem that an antenna connector, to which an antenna is connected, can be detected as not being connected in the case that the reception electric field is weak but still sufficient. Accordingly, it is an object of the present invention to provide a space diversity receiver for receiving broadcast signals, which, in case that one of the antenna connectors is not provided with an antenna, can produce a correct output signal in a more reliable and effective way. A further object of the present invention is to provide a space diversity receiver for receiving broadcast signals, which can effectively reduce harsh noise occurring in a sound reproduced based on the received signal output derived from a signal processing circuit block as a result of the signal sampling operation, as a result of lacking portions of the received signal output resulting from the signal sampling operation, or resulting from discontinuous portions of the received signal output resulting from the signal sampling operation. This object is achieved by a space diversity receiver according to claims 1 and 2, respectively. Further advantageous embodiments are defined in subclaims 3 to 5. Fig. 1 is a schematic circuit diagram containing block expression and showing a first embodiment of space diversity receiver according to the present invention; Figs. 2 and 3 are illustrations used for explaining an antenna connector employed in the embodiment shown in Fig. 1; Fig. 4 is a schematic circuit diagram containing block expression and showing a second embodiment of space diversity receiver according to the present invention; and Fig. 5 is a flow chart used for explaining the operation of the embodiment shown in Fig. 4. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 shows a first embodiment of space diversity receiver according to the present invention. The embodiment shown in Fig. 1 constitutes a space diversity receiver for use in an automobile to receive a television broadcast signal. Referring to Fig. 1, antennas 12A, 12B and 12D are connected with antenna connectors 11A, 11B and 11D, respectively, but an antenna 12C which is to be connected with an antenna connector 11C is not connected actually with the antenna connector 11C, so that the antenna connector 11C constitutes an unoccupied antenna connector. The antenna connectors 11A to 11D are included in antenna connection detecting portions 13A, 13B, 13C and 13D, respectively. Each of the antenna connection detecting portions 13A to 13D constitutes a connecting jack with the same configuration as shown in Figs. 2 and 3, in each of which the antenna connection detecting portion 13A is schematically shown as representative of the antenna connection detecting portions 13A to 13D. In the jack constituted by the antenna connection detecting portion 13A, when the antenna 12A is not connected with the antenna connector 11A, an electrode 26 coupled with a grounded terminal 20 is not connected with an electrode 27 coupled with the antenna connector 11A and an electrode 29 coupled with a detecting terminal 23 and connected through an insulator with the electrode 27 is connected with an electrode 28 coupled with a grounded terminal 22, as shown in Fig. 2. The detecting terminal 23 is connected through a resistor 25 with a voltage source supplying a positive DC voltage Vb. Accordingly, an antenna connector signal SA obtained from the antenna connector 11A has a zero level and an antenna detection output signal SAA obtained from the detecting terminal 23 has a low level corresponding to the ground level. When the antenna 12A is connected with the antenna connector 11A, the electrode 26 coupled with the grounded terminal 20 is connected with a ground electrode 12AE of the antenna 12A and the electrode 27 coupled with the antenna connector 11A is connected with a signal electrode 12AS of the antenna 12A, as shown in Fig. 3. The electrode 27 is moved by the signal electrode 12AS of the antenna 12A and thereby the electrode 29 coupled with the detecting terminal 23 is also moved, together with the electrode 27, so as to be remove from the electrode 28 coupled with the grounded terminal 22. Accordingly, the antenna connector signal SA obtained from the antenna connector 11A constitutes an antenna output signal derived from the antenna 12A and the antenna detection output signal SAA obtained from the detecting terminal 23 has a high level corresponding to the positive DC voltage Vb because the positive DC voltage Vb is supplied through the resistor 25 to the electrode 29 coupled with the detecting electrode 23. As understood from the above, the antenna connector signal SA obtained from the antenna connector 11A has the zero level and the antenna detection output signal SAA obtained from the detecting terminal 23 has the low level when the antenna 12A is not connected with the antenna connector 11A, and the antenna connector signal SA obtained from the antenna connector 11A constitutes the antenna output signal derived from the antenna 12A and the antenna detection output signal SAA obtained though the antenna connection detecting portion 13A has the high level when the antenna 12A is connected with the antenna connector 11A. In the case of the embodiment shown in Fig. 1, since the antenna 12A is connected in actual with the antenna connector 11A, the antenna connector signal SA is the antenna output signal derived from the antenna 12A and the antenna detection output signal SAA obtained through the antenna connection detecting portion 13A has the high level. In like manner, since the antenna 12B is connected with the antenna connector 11B, an antenna connector signal SB obtained from the antenna connector 11B is an antenna output signal derived from the antenna 12B and an antenna detection output signal SAB obtained through the antenna connection detecting portion 13B has the high level. In the case of the antenna connector 11C, however, since there is no antenna connected with the antenna connector 11C, an antenna connector signal SC obtained from the antenna connector 11C has the zero level and an antenna detection output signal SAC obtained through the antenna connection detecting portion 13C has the low level. Further, since the antenna 12D is connected with the antenna connector 11D, an antenna connector signal SD obtained from the antenna connector 11D is an antenna output signal derived from the antenna 12D and an antenna detection output signal SAD obtained through the antenna connection detecting portion 13D has the high level. The antenna connector signals SA, SB, SC and SD obtained through the antenna connectors 11A to 11D, respectively, when the television broadcast signal is received by each of the antennas 12A, 12B and 12D, are supplied through a capacitor 14A to a switching diode 15A, through a capacitor 14B to a switching diode 15B, through a capacitor 14C to a switching diode 15C and through a capacitor 14D to a switching diode 15D, respectively. The switching diodes 15A, 15B and 15D are controlled as explained later in such a manner that only one of the switching diodes 15A, 15B and 15D is put in the ON state to allow a signal to pass therethrough and the switching diode 15C is continuously put in the OFF state. Therefore one of the antenna connector signals SA, SB and SD is supplied through one of the switching diodes 15A, 15B and 15D and a capacitor 16 to a tuner 31 which constitutes a part of a signal processing circuit block 30. In the tuner 31, the antenna connector signal SA, SB or SD is amplified and subjected to frequency conversion. Then, a video intermediate frequency signal SVI is obtained based on the antenna connector signal SA, SB or SD from the tuner 31 and supplied to an intermediate frequency amplifier 32. The video intermediate frequency signal SVI amplified by the intermediate frequency amplifier 32 is then supplied to a video detector 33. In the video detector 33, the video intermediate frequency signal SVI is demodulated to produce a video signal VD. The video signal VD derived from the video detector 33 is amplified by a video amplifier 34 and then further amplified by an output amplifier 35 to be supplied to a cathode ray tube 36, so that a reproduced picture is obtained based on the video signal VD on a display screen of the cathode ray tube 36. An audio intermediate frequency signal SAI separated from the video intermediate frequency signal SVI is also obtained from the intermediate frequency amplifier 32 to be supplied to an audio intermediate frequency amplifier 37. The audio intermediate frequency signal SAI amplified by the audio intermediate frequency amplifier 37 is supplied to an audio detector 38. In the audio detector 38, the audio intermediate frequency signal SAI is demodulated to produce an audio signal AU. The audio signal AU derived from the audio detector 38 is amplified by an audio amplifier 39 to be supplied to a speaker 40, so that a reproduced sound is obtained based on the audio signal AU from the speaker 40. In the tuner 31, a signal to noise ratio (S/N ratio) of the antenna connector signal SA, SB, or SD is detected and a detection output signal SSN produced thereby is sent out of the tuner 31. The video signal VD derived from the video detector 33 is also supplied to each of a synchronous signal separator 41, a signal sampling circuit 42 and a pedestal level detector 60. In the synchronous signal separator 41, a vertical synchronous signal SV and a horizontal synchronous signal SH are separated from the video signal VD, and in the pedestal level detector 60, a pedestal level of the video signal VD is detected to produce a detection output signal SPL which varies in response to variations in the pedestal level of the video signal VD. The antenna detection output signals SAA, SAB, SAC and SAD obtained respectively from the antenna connection detecting portions 13A to 13D are supplied to an unoccupied antenna connector detecting portion 45. The unoccupied antenna connector detecting portion 45 is operative to detect, on the strength of the level of each of the antenna detection output signals SAA, SAB, SAC and SAD, one or more of the antenna connectors 11A to 11D, each of which constitutes the unoccupied antenna connector to produce the antenna connector signal SA, SB, SC or SD having the zero level, if any. In the case of the embodiment of Fig. 1, since each of the antenna detection output signals SAA, SAB and SAD has the high level and the antenna detection output signal SAC has the low level, the unoccupied antenna connector detecting portion 45 detects the antenna connector 11C based on the antenna detection output signal SAC and supplies a signal sampling controller 46 with a detection output signal SX which indicates that the antenna connector 11C constitutes the unoccupied antenna connector. A vertical synchronous signal SV and a horizontal synchronous signal SH derived from a synchronous signal separator 41, a detection output signal SSN derived from a tuner 31, a detection output signal SPL derived from a pedestal level detector 60 and a comparison output signal SR derived from a comparator 43 are also supplied to the signal sampling controller 46. The signal sampling controller 46 supplies both of a diode driving signal generator and a signal sampling circuit 42 with a control signal SS which is produced based on the detection output signals SSN, SPL and SX and the comparison output signal SR during a specific period in a vertical blanking period of a video signal VD detected based on the vertical and horizontal synchronous signals SV and SH, such as a period corresponding to an equalizing pulse period next to the vertical synchronous signal SV. The diode driving signal generator 47 is operative to supply through three of four output terminals thereof respectively anodes of switching diodes 15A, 15B and 15D with driving signal C1, C2 and C4 successively for every predetermined short period, such as every period of several microseconds, in response to the control signal SS which is produced based the signals including the detection output signal SX indicating that the antenna connector 11C is the unoccupied antenna connector and supplied from the signal sampling controller 46 during the specific period detected by the signal sampling controller 46 and not to supply a switching diode 15C with any driving signal. The switching diodes 15A, 15B and 15D are successively put in the ON state respectively by the driving signals C1, C2 and C4 supplied to the cathodes of the switching diodes 15A, 15B and 15D, and the switching diode 15C is continuously put in the OFF state. With such an operation of the diode driving signal generator 47, during the specific period detected by the signal sampling controller 46, the switching diodes 15A, 15B and 15D are successively put in the ON state for every predetermined short period so that a signal sampling operation by which the antenna connector signals SA, SB and SD are successively sampled for every predetermined short period to be supplied to a tuner 31 and the switching diode 15C is continuously put in the OFF state so that the antenna connector signal SC is not sampled to be supplied to the tuner 31 is carried out. Accordingly, the switching diodes 15A to 15D and the diode driving signal generator 47 constitute an antenna connector signal selecting portion, and during the specific period, such as the period corresponding to the equalizing pulse period next to the vertical synchronous signal, in every vertical blanking period or every predetermined number of vertical blanking periods of the video signal VD, the video signal VD based on the antenna connector signal SA, video signal VD based on the antenna connector signal SB and video signal VD based on the antenna connector signal SD are successively obtained for every predetermined short period from a video detector 33. The video signals VD thus obtained based on the antenna connector signals SA, SB and SD, respectively, are supplied to a signal sampling circuit 42 to which and the vertical and horizontal synchronous signals SV and SH derived from the synchronous signal separator 41 and the control signal SS derived from the signal sampling controller 46 are also supplied. The signal sampling circuit 42 is operative to pick out successively each of the video signals VD obtained based on the antenna connector signals SA, SB and SD, respectively, to be supplied the comparator 43 in synchronism with the control signal SS derived from the signal sampling controller 46. The comparator 43 is operative to hold each of the video signals VD obtained based on the antenna connector signals SA, SB and SD, respectively, and selected successively by the signal sampling circuit 42 and to compare in quality the video signals VD obtained based on the antenna connector signals SA, SB and SD with one another so as to select the best one of the video signals VD obtained based on the antenna connector signals SA, SB and SD, respectively. The comparison output signal SR representing the best video signal VD selected by the comparator 43 is obtained from the comparator 43 to be supplied to a signal selecting controller 44. The signal sampling circuit 42 and the comparator 43 constitute a signal selecting portion for selecting one of the antenna connector signals SA, SB and SD which gives rise to the best one of the video signals VD obtained based on the antenna connector signals SA, SB and SD, respectively, during the specific period detected by the signal sampling controller 46. The signal selecting controller 44, to which the vertical and horizontal synchronous signals SV and SH derived from the synchronous signal separator 41 are supplied, is operative to supply the diode driving signal generator 47 with a control signal SZ which has different aspects respectively in the case where the comparison output signal SR represents the video signal VD obtained based on the antenna connector signal SA, in the case where the comparison output signal SR represents the video signal VD obtained based on the antenna connector signal SB, and in the case where the comparison output signal SR represents the video signal VD obtained based on the antenna connector signal SD, during a period successive to the specific period in the vertical blanking period of the video signal VD. The diode driving signal generator 47 does not supply each of the switching diodes 15B to 15D with any driving signal but supplies the switching diode 15A with the driving signal C1 so as to cause only the switching diode 15A to be in the ON state when the control signal SZ from the signal selecting controller 44 corresponds to the comparison output signal SR representing the video signal VD obtained based on the antenna conneotor signal SA; does not supply each of the switching diodes 15A, 15C and 15D with any driving signal but supplies the switching diode 15B with the driving signal C2 so as to cause only the switching diode 15B to be in the ON state when the control signal SZ from the signal selecting controller 44 corresponds to the comparison output signal SR representing the video signal VD obtained based on the antenna connector signal SB; and does not supply each of the switching diodes 15A to 15C with any driving signal but supplies the switching diode 15D with the driving signal C4 so as to cause only the switching diode 15D to be in the ON state when the control signal SZ from the signal selecting controller 44 corresponds to the comparison output signal SR representing the video signal VD obtained based on the antenna connector signal SD, in the period successive to the specific period in the vertical blanking period of the video signal VD. The change in one of the driving signals C1, C2 and C4 sent out of the diode driving signal generator 47 is carried out at a time point corresponding to the beginning end of the vertical blanking period of the video signal VD. Accordingly, during the period successive to the specific period in the vertical blanking period of the video signal VD, one of the switching diodes 15A, 15B and 15D is caused to be in the ON state in such a manner as mentioned above so that one of the antenna connector signals SA, SB and SD is supplied to the tuner 31 and thereby the best one of the video signals VD obtained based on the antenna connector signals SA, SB and SD, respectively, is derived from the video detector 33. As described above, since the antenna connector signals SA, SB and SD obtained respectively from the antenna connectors 11A, 11B and 11D with which the antennas 12A, 12B and 12D are connected are subjected to the signal sampling operation in the antenna connector signal selecting portion which comprises the switching diodes 15A to 15D and the diode driving signal generator 47 and the antenna connector signal SC obtained from the antenna connector 11C with which any antenna is not connected is not subjected to the signal sampling operation, the antenna connector signal SC is prevented from being supplied to the tuner 31 so that the video signal VD derived from the video detector 33 is prevented from including a lacking portion resulted from the antenna connector signal SC during the specific period. Accordingly, harsh noise resulting from the signal sampling operation to be contained in a reproduced sound which is obtained from a speaker 40 in accordance with an audio signal AU is effectively suppressed. Fig. 4 shows a second embodiment of space diversity receiver according to the present invention. In Fig. 4, elements and circuit blocks corresponding to those of Fig. 1 are marked with the same references and further description thereof will be omitted. Referring to Fig. 4, antennas 12A, 12B and 12D are connected with antenna connectors 11A, 11B and 11D, respectively, but an antenna 12C which is to be connected with an antenna connector 11C is not connected actually with the antenna connector 11C, so that the antenna connector 11C constitutes a vacant antenna connector. A vertical synchronous signal SV and a horizontal synchronous signal SH derived from a synchronous signal separator 41 are supplied to a synchronous signal evaluating portion 61, in addition to a signal sampling circuit 42, a signal selecting controller 44 and a signal sampling controller 46. The synchronous signal evaluating portion 61 is operative to supply the signal sampling controller 46 with antenna connector selecting signals A1, A2, A3 and A4 selectively and thereby to control the signal sampling controller 46 so as to supply a diode driving signal generator 47 with such a control signal SS as to cause the diode driving signal generator 47 to supply a switching diode 15A with a driving signal C1 in response to the antenna connector selecting signal A1, to supply a switching diode 15B with a driving signal C2 in response to the antenna connector selecting signal A2, to supply a switching diode 15C with a driving signal C3 in response to the antenna connector selecting signal A3, and to supply a switching diode 15D with a driving signal C4 in response to the antenna connector selecting signal A4. With the operation of the synchronous signal evaluating portion 61 thus performed, the switching diode 15A is put in the ON state to allow the antenna connector signal SA obtained from the antenna connector 11A to be supplied through the switching diode 15A to a tuner 31 so that a video signal VD based on the antenna connector signal SA is obtained from a video detector 33 and thereby vertical and horizontal synchronous signals SV and SH in the video signal VD obtained based on the antenna connector signal SA are derived from the synchronous signal separator 41 when the antenna connector selecting signal A1 is supplied to the signal sampling controller 46 from the synchronous signal evaluating portion 61. In like manner, the switching diode 15B is put in the ON state to allow the antenna connector signal SB obtained from the antenna connector 11B to be supplied through the switching diode 15B to the tuner 31 so that the video signal VD based on the antenna connector signal SB is obtained from the video detector 33 and thereby vertical and horizontal synchronous signals SV and SH in the video signal VD obtained based on the antenna connector signal SB are derived from the synchronous signal separator 41 when the antenna connector selecting signal A2 is supplied to the signal sampling controller 46 from the synchronous signal evaluating portion 61. The switching diode 15C is put in the ON state to allow the antenna connector signal SC obtained from the antenna connector 11C to be supplied through the switching diode 15C to the tuner 31 so that the video signal VD based on the antenna connector signal SC is obtained from the video detector 33 and thereby vertical and horizontal synchronous signals SV and SH in the video signal VD obtained based on the antenna connector signal SC are derived from the synchronous signal separator 41 when the antenna connector selecting signal A3 is supplied to the signal sampling controller 46 from the synchronous signal evaluating portion 61. Further, the switching diode 15D is put in the ON state to allow the antenna connector signal SD obtained from the antenna connector 11D to be supplied through the switching diode 15D to the tuner 31 so that the video signal VD based on the antenna connector signal SD is obtained from the video detector 33 and thereby vertical and horizontal synchronous signals SV and SH in the video signal VD obtained based on the antenna connector signal SD are derived from the synchronous signal separator 41 when the antenna connector selecting signal A4 is supplied to the signal sampling controller 46 from the synchronous signal evaluating portion 61. Under such a condition, the synchronous signal evaluating portion 61 evaluates the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SA, the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SB, the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SC, and the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SD. Then, the synchronous signal evaluating portion 61 produces a control signal Q1 having a high level for indicating that an antenna 12A is connected with the antenna connector 11A when the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SA are supplied from the synchronous signal separator 41 in an appropriate manner and a control signal Q1 having a low level for indicating that the antenna connector 11A constitutes an unoccupied antenna connector when the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SA are supplied from the synchronous signal separator 41 in an inappropriate manner. In like manner, the synchronous signal evaluating portion 61 produces a control signal Q2 having a high level for indicating that an antenna 12B is connected with the antenna connector 11B when the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SB are supplied from the synchronous signal separator 41 in an appropriate manner and a control signal Q2 having a low level for indicating that the antenna connector 11B constitutes an unoccupied antenna connector when the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SB are supplied from the synchronous signal separator 41 in an inappropriate manner. The synchronous signal evaluating portion 61 produces a control signal Q3 having a high level for indicating that an antenna 12C is connected with the antenna connector 11C when the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SC are supplied from the synchronous signal separator 41 in an appropriate manner and a control signal Q3 having a low level for indicating that the antenna connector 11C constitutes an unoccupied antenna connector when the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SC are supplied from the synchronous signal separator 41 in an inappropriate manner. Further, the synchronous signal evaluating portion 61 produces a control signal Q4 having a high level for indicating that an antenna 12D is connected with the antenna connector 11D when the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SD are supplied from the synchronous signal separator 41 in an appropriate manner and a control signal Q4 having a low level for indicating that the antenna connector 11D constitutes an unoccupied antenna connector when the vertical and horizontal synchronous signals SV and SH separated from the video signal VD obtained based on the antenna connector signal SD are supplied from the synchronous signal separator 41 in an inappropriate manner. The control signals Q1, Q2, Q3 and Q4 thus produced are supplied to the signal sampling controller 46. In such a manner as described above, one or more of the antenna connectors 11A, 11B, 11C and 11D, each of which constitutes the unoccupied antenna connector, are detected by the synchronous signal evaluating portion 61, if any, and one or more of the control signals Q1, Q2, Q3 and Q4, each of which corresponds to the unoccupied antenna connector, are supplied to the signal sampling controller 46 with the low level from the synchronous signal evaluating portion 61. In the case of the embodiment of Fig. 4, since the antenna connector 11C constitutes the unoccupied antenna connector, the control signals Q1, Q2 and Q4 each having the high level and the control signal Q3 having the low level for indicating that the antenna connector 11A constitutes the unoccupied antenna connector are supplied to the signal sampling controller 46 from the synchronous signal evaluating portion 61. A vertical synchronous signal SV and a horizontal synchronous signal SH derived from a synchronous signal separator 41, a detection output signal SSN derived from a tuner 31, a detection output signal SPL derived from a pedestal level detector 60 and a comparison output signal SR derived from a comparator 43 are also supplied to the signal sampling controller 46. The signal sampling controller 46 supplies both of a diode driving signal generator 47 and a signal sampling circuit 42 with a control signal SS which is produced based on the detection output signals SSN and SPL, the comparison output signal SR, the control signals Q1, Q2 and Q4 each having the high level and the control signal Q3 having the low level during a specific period in a vertical blanking period of a video signal VD detected based on the vertical and horizontal synchronous signals SV and SH, such as a period corresponding to an equalizing pulse period next to the vertical synchronous signal SV. The diode driving signal generator 47 is operative to supply through three of four output terminals thereof respectively anodes of switching diodes 15A, 15B and 15D with driving signals C1, C2 and C4 successively for every predetermined short period, such as every period of several microseconds, in response to the control signal SS which is produced based the signals including the control signals Q1, Q2 and Q4 each having the high level and the control signal Q3 having the low level for indicating that the antenna connector 11C is the unoccupied antenna connector and supplied from the signal sampling controller 46 during the specific period detected by the signal sampling controller 46 and not to supply a switching diode 15C with any driving signal. The switching diodes 15A, 15B and 15D are successively put in the ON state respectively by the driving signals C1, C2 and C4 supplied to the cathodes of the switching diodes 15A, 15B and 15D, and the switching diode 15C is continuously put in the OFF state. With such an operation of the diode driving signal generator 47, during the specific period detected by the signal sampling controller 46, the switching diodes 15A, 15B and 15D are successively put in the ON state for every predetermined short period so that a signal sampling operation by which the antenna connector signals SA, SB and SD are successively sampled for every predetermined short period to be supplied to the tuner 31 and the switching diode 15C is continuously put in the OFF state so that the antenna connector signal SC is not sampled to be supplied to the tuner 31 is carried out. Accordingly, the switching diodes 15A to 15D and the diode driving signal generator 47 constitute an antenna connector signal selecting portion, and during the specific period, such as the period corresponding to the equalizing pulse period next to the vertical synchronous signal SV, in every vertical blanking period or every predetermined number of vertical blanking periods of the video signal VD, the video signal VD based on the antenna connector signal SA, video signal based on the antenna connector signal SB and video signal VD based on the antenna connector signal SD are successively obtained for every predetermined short period from the video detector 33. The video signals VD thus obtained based on the antenna connector signals SA, SB and SD, respectively, are supplied to a signal sampling circuit 42 to which the vertical and horizontal synchronous signals SV and SH derived from the synchronous signal separator 41 and the control signal SS derived from the signal sampling controller 46 are also supplied. The signal sampling circuit 42 is operative to pick out successively each of the video signals VD obtained based on the antenna connector signals SA, SB and SD, respectively, to be supplied the comparator 43 in synchronism with the control signal SS derived from the signal sampling controller 46. Then, the signal selection for selecting one of the antenna connector signals SA, SB and SD which gives rise to the best one of the video signals VD obtained based on the antenna connector signals SA, SB and SD, respectively, is carried out by a signal selecting portion comprising the signal sampling circuit 42 and the comparator 43 in the same manner as that in the embodiment shown in Fig. 1. Accordingly, during a period successive to the specific period in the vertical blanking period of the video signal VD, one of the switching diodes 15A, 15B and 15D is caused to be in the ON state so that one of the antenna connector signals SA, SB and SD is supplied to the tuner 31 and thereby the best one of the video signals VD obtained based on the antenna connector signals SA, SB and SD, respectively, is derived from the video detector 33. As described above, in the embodiment of Fig. 4 also, since the antenna connector signals SA, SB and SD obtained respectively from the antenna connectors 11A, 11B and 11D with which the antennas 12A, 12B and 12D are connected are subjected to the signal sampling operation in the antenna connector signal selecting portion which comprises the switching diodes 15A to 15D and the diode driving signal generator 47 and the antenna connector signal SC obtained from the antenna connector 11C with which any antenna is not connected is not subjected to the signal sampling operation, the antenna connector signal SC is prevented from being supplied to the tuner 31 so that the video signal VD derived from the video detector 33 is prevented from including a lacking portion resulted from the antenna connector signal SC during the specific period. Accordingly, harsh noise resulting from the signal sampling operation to be contained in a reproduced sound which is obtained from a speaker 40 in accordance with an audio signal AU is effectively suppressed. The synchronous signal evaluating portion 61 employed in the embodiment shown in Fig. 4 to operate as aforementioned is composed of, for example, a microcomputor and examples of control programs carried out by such a microcomputor for controlling the signal sampling operation in the antenna connector signal selecting portion are shown by a flow charts of Fig. 5. Referring to the flow chart shown in Fig. 5, in step 171, the antenna connector selecting signal A1 is sent out to the signal sampling controller 46, and in step 172, it is checked whether the vertical synchronous signal SV arrives from the synchronous signal separator 41. When the vertical synchronous signal SV does not arrive, it is checked whether a timer flag FT is "1" or not, in step 173. If the timer flag FT is not "1", a timer is started operating in step 174 and the timer flag FT is set to be "1" in step 175, and then the process advances to step 176. If it is clarified in the step 173 that the timer flag FT is "1", the timer process advances to the step 176 directly from the step 173. In step 176, it is checked whether a time Tt measured by the timer is longer than or equal to a predetermined period Ta or not. If the time Tt is smaller than the predetermined period Ta, the process returns to the step 172. If the time Tt is longer than or equal to the predetermined period Ta, the timer is stopped operating in step 177 and the timer flag FT is set to be "0" is step 178, and then the process advances to step 179. In the step 179, it is checked whether a counter flag FC is "1" or not. When the counter flag FC is "1", a counter for counting the horizontal synchronous signals SH is stopped operation is step 180 and the counter flag FC is set to be "0" is step 181, and then the process advances to step 182. If it is clarified in the step 179 that the counter flag FC is "0", the process advances to the step 182 directly from the step 179. In the step 182, the control signal Q1 is formed to have a low level LL and stored in a memory device, and the process advances to step 193. When it is clarified in the step 172 that the vertical synchronous signal SV arrives from the synchronous signal separator 41, it is checked whether the timer flag FT is "0" or not, in step 183. If the timer flag FT is not "0", the timer is stopped operating in step 184 and the timer flag FT is set to be "0" in step 185, and then the process advances to step 186. If it is clarified in the step 183 that the timer flag FT is "0", the process advances to the step 186 directly from the step 183. In the step 186, it is checked whether the counter flag FC is "1" or not. If the counter flag FC is "0", the counter is started to count the horizontal synchronous signals SH arriving from the synchronous signal separator 41 in step 187 and the counter flag FC is set to be "1" in step 188, and then the process returns to the step 172. If it is clarified in the step 186 that the counter flag FC is "1", the counter is stopped counting the horizontal synchronous signals SH in step 189 and the counter flag FC is set to be "0" in step 190, and then the process advances to the step 191. In the step 191, it is checked whether a counted value of the horizontal synchronous signals SH obtained from the counter is appropriate or not. If the counted value is not appropriate, the process returns the step 182. If the counted value is appropriate, the control signal Q1 is formed to have a high level LH and stored in the memory device in step 192 and the process advances to step 193. With the processes described above, the check of the antenna 12A in which it is checked whether the antenna 12A is connected with the antenna connector 11A or not has finished. In the step 193, the antenna connector selecting signal A1 is stopped being sent out and instead the antenna connector selecting signal A2 is sent out to the signal sampling controller 46. Then, in step 194, the check of the antenna 12B in which it is checked whether the antenna 12B is connected with the antenna connector 11B or not is carried out in the same manner as the check of the antenna 12A and the control signal Q2 is formed to have the low level LL or high level LH and stored in the memory device. After the check of the antenna 12B has finished, the process advances to step 195. In the step 195, the antenna connector selecting signal A2 is stopped being sent out and instead the antenna connector selecting signal A3 is sent out to the signal sampling controller 46. Then, in step 196, the check of the antenna 12C in which it is checked whether the antenna 12C is connected with the antenna connector 11C or not is carried out in the same manner as the check of the antenna 12A and the control signal Q3 is formed to have the low level LL or the high level LH and stored in the memory device. After the check of the antenna 12C has finished, the process advances to step 197. In the step 197, the antenna connector selecting signal A3 is stopped being sent out and instead the antenna connector selecting signal A4 is sent out to the signal sampling controller 46. Then, in step 198, the check of the antenna 12D in which it is checked whether the antenna 12D is connected with the antenna connector 11D or not is carried out in the same manner as the check of the antenna 12A and the control signal Q4 is formed to have the low level LL or high level LH and stored in the memory device. After the check of the antenna 12D has finished, the process advances to step 199. In the step 199, the antenna connector selecting signal A4 is stopped being sent out. Then, each of the control signals Q1, Q2, Q3 and Q4 is set to be continuously sent out to the signal sampling controller 46, in step 200, and then the control program is completed.

Claims: A space diversity receiver for receiving broadcast signals comprising: a plurality of antenna connectors (11A-D), with each of which an antenna (12A-D) may be connected, signal selecting means (47-54, 15A-D) for selecting one from amongst the signals output respectively from the antenna connectors (11A-D), signal processing circuit means (30) operative to produce an output signal based on a signal selected by the signal selecting means (47-54, 15A-D), signal sampling control means (46) detecting a predetermined specific period, said predetermined specific period comprising predetermined short periods, and operative to cause the signal selecting means (47-54, 15A-D) to perform a signal sampling operation by which during said predetermined specific period, the signals obtained from the respective antenna connectors (11A-D) are successively sampled for every predetermined short period and supplied to the signal processing circuit means (30), antenna connector selecting means (42, 43) operative to compare in quality the output signals of the signal processing circuit means (30) obtained successively by the signal sampling operation with one another in order to select one of the antenna connectors (11A-D) through which a signal giving rise to the best output signal of the signal processing circuit means (30) is introduced during said predetermined specific period, signal selecting control means (44) operative to cause the signal selecting means (47-54, 15A-D) to select the signal introduced through the antenna connector (11A-D) selected by the antenna connector selecting means (42, 43) during a period successive to said predetermined specific period, and antenna occupancy checking means (45, 13A-D) operative to detect one or more of the antenna connectors (11A-D) with which an antenna (12A-D) is not connected and to cause the signal sampling operation in the signal selecting means (47-54, 15A-D) not to sample the signal output from said unoccupied antenna connector or connectors (11A-D), wherein said antenna occupancy checking means (45, 13A-D) comprises a plurality of antenna connection detecting means (13A-D) formed to include the antenna connectors (11A-D), respectively, and each adapted to produce an antenna detection output signal having a first level when an antenna (12A-D) is connected with the antenna connector (11A-D) included therein and a second level different from said first level when an antenna (12A-D) is not connected with the antenna connector (11A-D) included therein, and unoccupied antenna connector detecting means (45) for detecting an unoccupied antenna connector (11A-D) with which the antenna (12A-D) is not connected based on the antenna detection output signal and supplying the signal sampling control means (46) with a detection output signal indicating antenna occupancy on the antenna connectors (11A-D). A space diversity receiver for receiving broadcast signals comprising: a plurality of antenna connectors (11A-D), with each of which an antenna (12A-D) may be connected, signal selecting means (47-54, 15A-D) for selecting one from amongst the signals output respectively from the antenna connectors (11A-D), signal processing circuit means (30) operative to produce an output signal based on a signal selected by the signal selecting means (47-54, 15A-D), signal sampling control means (46) detecting a predetermined specific period, said predetermined specific period comprising predetermined short periods, and operative to cause the signal selecting means (47-54, 15A-D) to perform a signal sampling operation by which, during said predetermined specific period, the signals obtained from the respective antenna connectors (11A-D) are successively sampled for every predetermined short period and supplied to the signal processing circuit means (30), antenna connector selecting means (42, 43) operative to compare in quality the output signals of the signal processing circuit means (30) obtained successively by the signal sampling operation with one another in order to select one of the antenna connectors (11A-D) through which a signal giving rise to the best output signal of the signal processing circuit means (30) is introduced during said predetermined specific period, signal selecting control means (44) operative to cause the signal selecting means (47-54, 15A-D) to select the signal introduced through the antenna connector (11A-D) selected by the antenna connector selecting means (42, 43) during a period successive to said predetermined specific period, and antenna occupancy checking means (45, 13A-D) operative to detect one or more of the antenna connectors (11A-D) with which an antenna (12A-D) is not connected and to cause the signal sampling operation in the signal selecting means (47-54, 15A-D) not to sample the signal output from said unoccupied antenna connector or connectors (11A-D), wherein said antenna occupancy checking means (45, 13A-D) comprises signal evaluating means (61) operative to evaluate a predetermined signal component (SV, SH) contained in each of the output signals (VD) of the signal processing circuit means (30) obtained successively based on the signals sampled through the signal sampling operation performed by the signal selecting means (42-54, 15A-D) for detecting an unoccupied antenna connector (11A-D) with which an antenna (12A-D) is not connected based on results of evaluation of said predetermined signal components (SV, SH) and to supply the signal sampling control means (46) with a control signal indicating antenna occupancy on the antenna connectors (11A-D). A space diversity receiver according to claim 1 or 2, characterized in that said signal selecting means (47-54, 15A-D) comprises a plurality of switching devices (15A-D) having respective first ends connected with the antenna connectors (11A-D), respectively, and respective second ends connected in common to the signal processing circuit means (30) and a driving signal generator (47) for supplying each of said switching devices (15A-D) selectively with a driving signal. A space diversity receiver according to claim 3, characterized in that said switching device comprises a diode (15A-D) having one end connected through a capacitor (14A-D) with one of the antenna connectors (11A-D) and the other end connected through a capacitor (16) with the signal processing circuit means (30). A space diversity receiver according to anyone of the claims 1 to 4, characterized in that said antenna connector selecting means (42, 43) comprises a signal sampling circuit (42) for sampling each of the output signals of the signal processing circuit means (30) obtained based on the signals sampled through said signal sampling operation in the signal selecting means (47-52, 15A-D), respectively, and a comparator (43) for comparing in quality the output signals of the signal processing circuit means (30) sampled by said signal sampling circuit (42) with one another to supply the signal selecting control means (46) with a comparison output signal indicating said selected antenna connector (11A-D) through which the signal giving rise to the best output signal of the signal processing circuit means (30) is introduced.

Inventors: HAYASHI TOSHITADA, NAKAYAMA HIROSHI, OKAMOTO TADASHI, SHIMADA YOSHIHIRO, HAYASHI, TOSHITADA, NAKAYAMA, HIROSHI, OKAMOTO, TADASHI, SHIMADA, YOSHIHIRO, Hayashi, Toshitada, c/o Tokyo Electronic, Nakayama, Hiroshi, c/o Tokyo Electronic
Applicants: SONY CORP, SONY CORPORATION
Application year: 1992
Main classification: H04B7
IPC codes: H04B7