Patent Publication Number: US-9906251-B2

Title: Reception device and electronic apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of and claims the benefit under 35 U.S.C. § 120 of U.S. patent application Ser. No. 14/766,909, titled “RECEPTION DEVICE AND ELECTRONIC APPARATUS” filed on Aug. 10, 2015, which is a National Stage of International Application No. PCT/JP2014/000405, filed in the Japanese Patent Office as a Receiving Office on Jan. 28, 2014, which claims priority to Japanese Patent Application Number JP 2013-041070, filed in the Japanese Patent Office on Mar. 1, 2013, each of which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a reception device that receives a transmission signal such as a television broadcasting signal, and an electronic apparatus including the reception device. 
     BACKGROUND ART 
     Devices including a plurality of reception circuits are developed today as television receivers and recording devices that include reception circuits which receive television broadcasting. For example, television receivers including a plurality of reception circuits can concurrently display reception images of a plurality of channels on the display screen. Meanwhile, recording devices including a plurality of reception circuits can concurrently record broadcasting signals of a plurality of channels. 
       FIG. 8  is a diagram illustrating an example of a conventional device including a plurality of reception circuits. 
     Signals received by an antenna  1  are supplied to a first tuner unit  2  and a second tuner unit  3 . The first and second tuner units  2  and  3  individually include reception circuits  2   a  and  3   a , respectively. Each of the reception circuits  2   a  and  3   a  receives a broadcasting signal of a specific channel (frequency). A channel received by each of the reception circuits  2   a  and  3   a  is decided, for example, on the basis of an instruction from a control unit in the device which is not illustrated. 
     Each of the reception circuits  2   a  and  3   a  acquires a baseband signal or an intermediate frequency signal converted from a broadcasting signal. To acquire such a baseband signal or intermediate frequency signal, a frequency signal (locally generated signal) is necessary which is mixed with a reception signal by a mixer (not illustrated) in the reception circuits  2   a  and  3   a . A locally generated frequency signal that is mixed with a reception signal by this mixer is obtained by a phase locked loop (PLL) circuit multiplying reference frequency signals generated by oscillation circuits  2   d  and  3   d  built in the tuner units  2  and  3 , respectively. The oscillation circuits  2   d  and  3   d  use crystal oscillators  2   c  and  3   c  to acquire reference frequency signals, the crystal oscillators  2   c  and  3   c  being connected to the oscillation circuits  2   d  and  3   d , respectively. 
     Each of the reception circuits  2   a  and  3   a  then performs a demodulation process on a baseband signal or an intermediate frequency signal. An image signal and an audio signal obtained through this demodulation process are acquired by output terminals  2   b  and  3   b  of the reception circuits  2   a  and  3   a.    
     Patent Literature 1 describes a technique of supplying oscillation signals of a single reference signal oscillation circuit to a plurality of PLL circuits via a buffer amplifier. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2002-359556A 
     SUMMARY OF INVENTION 
     Technical Problem 
     When the plurality of tuner units  2  and  3  are installed as illustrated in  FIG. 8 , reference frequency signals supplied to the respective tuner units  2  and  3  have accuracy depending on the crystal oscillators  2   c  and  3   c  connected to the tuner units  2  and  3 , respectively. Crystal oscillators generally have a frequency error from a few of ppm to several tens of ppm, and reference frequency signals acquired by the respective tuner units  2  and  3  also have some frequency errors. 
     Locally generated frequency signals that are mixed with reception signals by the respective tuner units  2  and  3  are generated by multiplying reference frequency signals. Accordingly, even a minor error in the reference frequency signals may cause a frequency difference of several MHz in locally generated signals for the respective tuner units  2  and  3  to receive the same channel. 
     If such locally generated signals having a frequency error of several MHz are used by the two neighboring tuner units  2  and  3 , the respective locally generated signals leak to the other tuner unit. 
     Once such locally generated signals having slightly different frequencies leak to the other of the neighboring tuner unit  2  and  3 , the leaked signals serve as false locally generated signals for a reception operation in some cases. If locally generated signals that are slightly different leak, circuits that generate locally generated signals interfere with each other. The generation of false locally generated signals and the mutual interference of locally generated frequency signal generating circuits as discussed above cause radio disturbance. 
     A phenomenon called injection locking is known as a problem with such two frequency signals having close frequencies. For example, if an oscillation frequency ωinj and an oscillation current Iinj are injected from the outside to an oscillation circuit that is oscillating at a free running frequency ω 0  under an oscillation current Iosc, this oscillation circuit is pulled into the frequency ωinj, which is different from the original oscillation frequency ω 0 , and begins to oscillate at the frequency ωinj. 
     An object of the present disclosure is to provide a reception device and electronic apparatus that include a plurality of reception circuits and can prevent reference frequency signals from interfering with each other, the reference frequency signals being used by each reception circuit. 
     Solution to Problem 
     A reception device according to the present disclosure includes first and second reception circuits configured to receive transmission signals, and first and second oscillation circuits configured to supply reference frequency signals to the first and second reception circuits. 
     A first oscillation circuit generates a differential signal having a predetermined frequency on the basis of an oscillation signal acquired from a connected crystal oscillator, and supplies the generated differential signal to the first reception circuit as a reference frequency signal. 
     A second oscillation circuit is supplied with an oscillation signal having one of phases in the differential signal acquired by the first oscillation circuit, generates a differential signal having a predetermined frequency on the basis of the supplied oscillation signal, and supplies the generated differential signal to the second reception circuit as a reference frequency signal. 
     An electronic apparatus according to the present disclosure includes first and second reception circuits configured to receive transmission signals, first and second oscillation circuits configured to supply reference frequency signals to the first and second reception circuits, and a processing unit configured to process the transmission signals received by the first and second reception circuits. 
     A first oscillation circuit generates a differential signal on the basis of an oscillation signal acquired from a connected crystal oscillator, and supplies the generated differential signal to the first reception circuit as a reference frequency signal. 
     A second oscillation circuit is supplied with an oscillation signal having one of phases in the differential signal acquired by the first oscillation circuit, generates a differential signal having a predetermined frequency on the basis of the supplied oscillation signal, and supplies the generated differential signal to the second reception circuit as a reference frequency signal. 
     According to the present disclosure, the first oscillation circuit uses the connected crystal oscillator to generate a reference frequency signal as a differential signal. The second oscillation circuit is supplied with an oscillation signal alone that has one of phases in the differential signal output by the first oscillation circuit, and generates a reference frequency signal. Accordingly, the reference frequency signals of the oscillation circuits have the same frequency, thereby preventing radio disturbance due to an error in the reference frequency signals. 
     Advantageous Effects of Invention 
     According to the present disclosure, an oscillation circuit prepared for each reception circuit uses a frequency signal acquired from a single crystal oscillator to generate a reference frequency signal, causing no error in reference frequency signals and effectively avoiding radio disturbance due to the error in the reference frequency signals. Oscillation circuits included in a plurality of reception circuits use a common crystal oscillator, allowing the circuit configurations to be simple. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a circuit diagram illustrating an example of a configuration according to a first embodiment of the present disclosure. 
         FIG. 2  is a block diagram illustrating an example of a reception circuit according to the first embodiment of the present disclosure. 
         FIG. 3  is a frequency characteristic diagram illustrating an example of a characteristic (advantageous effect attained by sharing a crystal oscillator) according to the first embodiment of the present disclosure. 
         FIG. 4  is a frequency characteristic diagram illustrating an example of a characteristic (example of a change in noise of an oscillation signal in a tuner unit at each stage) according to the first embodiment of the present disclosure. 
         FIG. 5  is a circuit diagram illustrating an example (modified example) of a configuration according to the first embodiment of the present disclosure. 
         FIG. 6  is a circuit diagram illustrating an example of a configuration according to a second embodiment of the present disclosure. 
         FIG. 7  is a circuit diagram illustrating an example of disposition of a transmission path according to the second embodiment of the present disclosure. 
         FIG. 8  is a circuit diagram illustrating an example of a conventional reception device. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Examples of a reception device and an electronic apparatus according to an embodiment of the present disclosure will be described in the following order with reference to the appended drawings. 
     1. Example of First Embodiment ( FIGS. 1 to 4 ) 
     1. Modified Example of First Embodiment ( FIG. 5 ) 
     3. Example of Second Embodiment ( FIGS. 6 to 7 ) 
     4. Modified Example 
     1. Example of First Embodiment 
       FIG. 1  is a diagram illustrating an example of a configuration of a reception device according to an example of a first embodiment of the present disclosure. 
     The reception device according to the present disclosure is a device that receives a television broadcasting signal, and includes a first tuner unit  10 , a second tuner unit  20 , and a third tuner unit  30 . Signals received by an antenna  1  are supplied to input terminals  10   a ,  20   a , and  30   a  of these tuner units  10 ,  20 , and  30 . 
     The tuner units  10 ,  20 , and  30  individually include reception circuits  11 ,  21 , and  31 , respectively. Each of the reception circuits  11 ,  21 , and  31  receives a broadcasting signal of a specific channel (frequency). A channel received by each of the reception circuits  11 ,  21 , and  31  is decided, for example, on the basis of an instruction from a control unit that is not illustrated in the reception device. In this case, for example, the two reception circuits  11  and  21  can receive even the same channel. 
     Each of the reception circuits  11 ,  21 , and  31  acquires, through a reception process, a baseband signal or an intermediate frequency signal obtained by performing frequency conversion on a broadcasting signal. Each of the reception circuits  11 ,  21 , and  31  then performs a demodulation process on a baseband signal or an intermediate frequency signal. An image signal and an audio signal obtained through this demodulation process are supplied from output terminals  10   b ,  20   b , and  30   b  of the tuner units  10 ,  20 , and  30  to a television signal processing unit  90 . The three tuner units  10 ,  20 , and  30  are configured as individual integrated circuits. Alternatively, the three tuner units  10 ,  20 , and  30  may be configured as a single integrated circuit. 
     Additionally, each of the tuner units  10 ,  20 , and  30  is configured to perform a demodulation process on a reception signal in the example of  FIG. 1 , but each of the tuner units  10 ,  20 , and  30  may also be configured not to perform a demodulation process. That is to say, each of the tuner units  10 ,  20 , and  30  may be configured to output a baseband signal or an intermediate frequency signal, and a processing unit (television signal processing unit  90 ) connected to the later stage of the tuner units  10 ,  20 , and  30  may be configured to perform a demodulation process. 
       FIG. 2  is a diagram illustrating an example of a reception circuit  11  included in the first tuner unit  10 . Reception circuits  21  and  31  included in the second and third tuner units  20  and  30  are configured in the same way as the reception circuit  11 . 
     The reception circuit  11  includes a radio frequency unit  11   a  that mixes a locally generated signal with a radio frequency signal to convert the locally generated signal into a baseband signal or an intermediate frequency signal, and a demodulation unit  11   b  that demodulates the baseband signal or the intermediate frequency signal acquired by the radio frequency unit  11   a  to acquire an image signal or an audio signal. As discussed above, the first tuner unit  10  includes the demodulation circuit  11   b  as an example, so that the tuner unit may also be configured without any demodulation circuit. 
     In addition, the reception circuit  11  includes a locally generated signal generating unit  11   c  that generates a locally generated signal that is mixed with a reception signal by the radio frequency unit  11   a . A reference frequency signal is supplied to the locally generated signal generating unit  11   c  from an oscillation circuit  12  discussed below. In this case, a reference frequency signal supplied from the oscillation circuit  12  to the locally generated signal generating unit  11   c  is a differential signal including two signals CKx and CKy each of which has one of phases reversed to each other. 
     The locally generated signal generating unit  11   c  includes, for example, a PLL circuit and a frequency divider circuit, and generates a locally generated signal corresponding to a reception frequency from the reference frequency signal. The locally generated signal that is generated by the locally generated signal generating unit  11   c  is supplied to the radio frequency unit  11   a.    
     The demodulation unit  11   b  performs a demodulation process and a decoding process corresponding to a modulation scheme of a received broadcasting signal. When these demodulation process and decoding process are performed, the reference frequency signal supplied from the oscillation circuit  12  is used as a clock. A reference frequency signal for this demodulation unit  11   b  to perform a demodulation process and a decoding process is also a differential signal including two signals CKx and CKy each of which has one of phases reversed to each other. 
     Returning to the description of  FIG. 1 , the first tuner unit  10  includes the oscillation circuit  12 , which generates a reference frequency signal. Connected to the oscillation circuit  12  is a crystal oscillator  99  via terminals  10   c  and  10   d . An oscillation signal obtained by applying voltage to the crystal oscillator  99  is extracted by the oscillation circuit  12  as a reference frequency signal. A reference frequency signal output by the oscillation circuit  12  is a differential signal including two signals CKx and CKy each of which has one of phases reversed to each other as discussed above. 
     The reference frequency signal generated by the oscillation circuit  12  is supplied to the reception circuit  11 . The demodulation unit  11   b  and the locally generated signal generating unit  11   c  in the reception circuit  11  perform a process using the reference frequency signal. 
     In addition, the reference frequency signal generated by the oscillation circuit  12  is supplied to an amplifier circuit  13 . The amplifier circuit  13  amplifies the reference frequency signal serving as a differential signal. 
     A reference frequency signal (e.g. signal CKx) having one of the phases in the differential signal amplified by the amplifier circuit  13  of the first tuner unit  10  is then output from a terminal  10   e , and supplied to a terminal  20   d  of the second tuner unit  20 . Meanwhile, a termination resistor  14  is, for example, connected to an output unit for a reference frequency signal (e.g. signal CKy) having the other phase in the differential signal amplified by the amplifier circuit  13 . Connecting the termination resistor  14  to an output unit including no connection at the later stage is an example, so that nothing may be connected to an output unit including no connection at the later stage. Other termination resistors  24 ,  34 ,  35 ,  44 , and  45  discussed below are configured to be connected thereto as an example, but nothing may also be connected. 
     The reference frequency signal acquired by the terminal  20   d  of the second tuner unit  20  is supplied to an oscillation circuit  22  in the second tuner unit  20 . The oscillation circuit  22  generates, from a reference frequency signal having one of phases in the differential signal acquired by this terminal  20   d , a differential signal having the same frequency. The reference frequency signal generated by the oscillation circuit  22  is then supplied to the reception circuit  21 , and a reception process is performed using the reference frequency signal in the reception circuit  21 . 
     In addition, the reference frequency signal generated by the oscillation circuit  22  is supplied to an amplifier circuit  23 . The amplifier circuit  23  amplifies the reference frequency signal serving as a differential signal. 
     A reference frequency signal having one of phases in the differential signal amplified by the amplifier circuit  23  of the second tuner unit  20  is then output from a terminal  20   e , and supplied to a terminal  30   d  of the third tuner unit  30 . Meanwhile, a termination resistor  24  is, for example, connected to an output unit for a reference frequency signal having the other phase in the differential signal amplified by the amplifier circuit  23 . 
     The reference frequency signal acquired by the terminal  30   d  of the third tuner unit  30  is supplied to an oscillation circuit  32  in the third tuner unit  30 . The oscillation circuit  32  generates, from a reference frequency signal having one of phases in the differential signal acquired by this terminal  30   d , a differential signal having the same frequency. The reference frequency signal generated by the oscillation circuit  32  is then supplied to the reception circuit  31 , and a reception process is performed using the reference frequency signal in the reception circuit  31 . 
     In addition, the reference frequency signal generated by the oscillation circuit  32  is supplied to an amplifier circuit  33 . The amplifier circuit  33  amplifies the reference frequency signal serving as a differential signal. Termination resistors  34  and  35  are, for example, connected to an output unit for the differential signal amplified by this amplifier circuit  33 . 
     The terminal resistors  34  and  35  do not have to be connected to the third tuner unit  30 , which is the last tuner unit in a cascade connection, but the amplifier circuit  33  may be configured to enter a sleep state. 
     Additionally, the termination resistors  14 ,  24 ,  34 , and  35  that are connected to the amplifier circuits  13 ,  23 , and  33  may also be configured to be connected to the outside of each of the tuners  10 ,  20 , and  30 . 
     Image signals and audio signals acquired by the output terminals  10   b ,  20   b , and  30   b  of the tuner units  10 ,  20 , and  30  are then supplied to the television signal processing unit  90 . 
     If the reception device according to the present disclosure is a television receiver, the television signal processing unit  90  performs a process for displaying an image and a process for outputting a sound. 
     Meanwhile, if the reception device according to the present disclosure is a video recording device, the television signal processing unit  90  performs a process for recording an image signal and an audio signal. 
     This reception device according to the present disclosure illustrated in  FIG. 1  includes the three tuner units  10 ,  20 , and  30 , but reference frequency signals used by these three tuner units  10 ,  20 , and  30  to perform signal processing are oscillation signals acquired from a single crystal oscillator  99 . The reference frequency signals acquired by the oscillation circuits  12 ,  22 , and  32  in the three tuner units  10 ,  20 , and  30  thus have completely the same frequency. 
     That is to say, the oscillation circuit  12  in the first tuner unit  10  includes the crystal oscillator  99  and generates a reference frequency signal that is a differential signal, but the oscillation circuit  22  in the second tuner unit  20  is supplied from the oscillation circuit  12  in the first tuner unit  10  with a signal having one of phases in the differential signal. The oscillation circuit  32  in the third tuner unit  30  is supplied from the oscillation circuit  22  in the second tuner unit  20  with a signal having one of phases in the differential signal. Thus, the three oscillation circuits  12 ,  22 , and  32  generate reference frequency signals that are based on the same oscillation signal and have completely the same frequency. 
     Accordingly, the reception device according to the present disclosure has no error in reference frequency signals in the three tuner units  10 ,  20 , and  30 , causing no radio disturbance due to the error in the reference frequency signals. 
       FIG. 3  is a diagram illustrating advantageous effects attained by sharing the crystal oscillator  99  among the oscillation circuits  12 ,  22 , and  32  of the tuner units  10 ,  20 , and  30  in the reception device according to the present disclosure. The horizontal axis represents a frequency in  FIG. 3 , while the vertical axis represents necessary C/N [dB]. The necessary C/N uses a ratio of signals (carriers) to noise to show to what extent a signal is distortionless (clear) with respect to a reception signal necessary for each tuner unit to perform a reception process. Smaller value of the necessary C/N of the tuner unit shows higher performance that allows even a distorted reception signal to be demodulated. 
     A characteristic x illustrated in  FIG. 3  shows the necessary C/N [dB] at respective frequencies for a different crystal oscillator included in a neighboring tuner unit, and a characteristic y shows the necessary C/N [dB] at respective frequencies for a common crystal oscillator used by a neighboring tuner unit. As illustrated in  FIG. 3 , the characteristic y of the reception device according to the present disclosure, in which a neighboring tuner unit uses a common crystal oscillator, shows a lower necessary C/N and higher reception performance at any frequency than the characteristic x for a different crystal oscillator. 
       FIG. 4  is a diagram illustrating a change in phase noise included in reference frequency signals generated by the oscillation circuits  12 ,  22 , and  32  of the tuner units  10 ,  20 , and  30  in the reception device according to the present disclosure. The horizontal axis represents a frequency in  FIG. 4 , and the vertical axis represents phase noise [dBc/Hz]. Characteristics CK 1 , CK 2 , and CK 3  show reference frequency signals output by the oscillation circuits  12 ,  22 , and  32 , respectively. 
     The reception device according to the present disclosure supplies a reference frequency signal generated by the oscillation circuit  12  in the first tuner unit  10  to the second tuner unit  20 , and further supplies a reference frequency signal generated by the oscillation circuit  22  in the second tuner unit  20  to the third tuner unit  30 . Sending reference frequency signals sequentially in this way gradually increases phase noise of the reference frequency signals. 
     That is to say, as illustrated in  FIG. 4 , the phase noise CK 2  of a reference frequency signal generated by the oscillation circuit  22  in the second tuner unit  20  is deteriorated by about 1.6 [dBc/Hz] on average as compared to the phase noise CK 1  of a reference frequency signal generated by the oscillation circuit  12  in the first tuner unit  10 . Meanwhile, the phase noise CK 3  of a reference frequency signal generated by the oscillation circuit  32  in the third tuner unit  30  is deteriorated by about 1.6 [dBc/Hz] on average as compared to the phase noise CK 2  of a reference frequency signal generated by the oscillation circuit  22  in the second tuner unit  20 . 
     In this way, sequentially sending reference frequency signals to the tuner units at the next stages deteriorates phase noise of a reference frequency signal acquired by the tuner unit by about 1.6 [dBc/Hz] at each stage. 
     2. Modified Example of First Embodiment 
       FIG. 5  is a diagram illustrating a modified example of the configuration of the reception device according to the example of the first embodiment of the present disclosure. 
     The reception device according to the example of  FIG. 5  is obtained by further adding a fourth tuner unit  40  to the reception device including the first to third tuner units  10 ,  20 , and  30  illustrated in  FIG. 1 . 
     A reference frequency signal (signal having one of phases in a differential signal) output from the terminal  20   e  of the second tuner unit  20  is divided into two, and supplied to the third tuner unit  30  and the fourth tuner unit  40  in the example of  FIG. 5 . 
     The fourth tuner unit  40  is configured in the same way as the first to third tuner units  10 ,  20 , and  30 , and includes a reception circuit  41 , an oscillation circuit  42 , and an amplifier circuit  43 . The oscillation circuit  42  generates a differential signal on the basis of a reference frequency signal (signal having one of the phases in a differential signal) acquired by a terminal  40   d , and the differential signal is supplied to the reception circuit  41  and the amplifier circuit  43 . 
     Termination resistors  44  and  45  are, for example, connected to an output unit for an amplified signal of the amplifier circuit  43  of the fourth tuner unit  40 . No termination resistor has to be connected to this fourth tuner unit  40  as with the third tuner unit  30  described with reference to  FIG. 1 , and the amplifier circuit  43  may enter a sleep state. 
     An image signal and an audio signal received by the reception circuit  41  of the fourth tuner unit  40  and acquired by the output terminal  40   b  are then supplied to the television signal processing unit  90 . 
     The other parts in  FIG. 5  are configured in the same way as those of the reception device illustrated in  FIG. 1 . 
     As illustrated in  FIG. 5 , dividing and supplying a reference frequency signal output by the second tuner unit  20  to a plurality of tuner units  30  and  40  make it possible to supply a reference frequency signal to more tuner units. 
     3. Example of Second Embodiment 
     Next, an example of a second embodiment of the present disclosure will be described with reference to  FIGS. 6 and 7 . The parts that have been described in the first embodiment and correspond to those of  FIGS. 1 to 5  are denoted with the same reference numerals in  FIGS. 6 and 7 . 
       FIG. 6  is a diagram illustrating an example of a configuration of a reception device according to an example of the second embodiment of the present disclosure. 
     The reception device according to the example of the second embodiment of the present disclosure is also a device that receives a television broadcasting signal, and includes first to ninth tuner units  110  to  190 . A signal received by the antenna  1  is divided and supplied to input terminals  110   a  to  190   a  of these tuner units  110  to  190 . 
     The tuner units  110  to  190  include reception circuits  111  to  191 , respectively. Each of the reception circuits  111  to  191  receives a broadcasting signal of a specific channel (frequency), and image signals and audio signals obtained through the reception are outputted from output terminals  110   b  to  190   b . A channel received by each of the reception circuits  111  to  191  is decided, for example, on the basis of an instruction from a control unit that is not illustrated in the reception device. 
     Each of the tuner units  110  to  190  is configured in the same way as each of the tuner units  10  to  30  illustrated in  FIG. 1  for the example of the first embodiment. That is to say, each of the reception circuits  111  to  191  acquires a baseband signal or an intermediate frequency signal converted from a broadcasting signal. Each of the reception circuits  111  to  191  then performs a decoding process on a baseband signal or an intermediate frequency signal. An image signal and an audio signal obtained through this demodulation process are supplied from the output terminals  110   b  to  190   b  of the reception circuits  111  to  191  to the television signal processing unit  90 . The nine tuner units  110  to  190  are configured as individual integrated circuits. Alternatively, the nine tuner units  110  to  190  may be configured as a single integrated circuit. 
     Each of the tuner units  110  to  190  may also be configured not to perform a demodulation process in this example of  FIG. 6 . That is to say, each of the tuner units  110  to  190  may be configured to output a baseband signal or an intermediate frequency signal, and a processing unit connected to the later stage of the tuner units  110  to  190  may be configured to perform a demodulation process. 
     The tuner units  110  to  190  include oscillation circuits  112  to  192 , respectively, each of which generates a reference frequency signal, and the reception circuits  111  to  191  in each tuner unit  110  generate reference frequency signals necessary for signal processing. 
     In this case, connected to the oscillation circuit  112  of the first tuner unit  110  is the crystal oscillator  99  via terminals  110   c  and  110   d . The oscillation circuit  112  uses an oscillation signal obtained by applying voltage to the crystal oscillator  99  as a reference frequency signal. A reference frequency signal output by the oscillation circuit  112  is a differential signal including two signals CKx and CKy each of which has one of phases reversed to each other. 
     The reference frequency signal generated by the oscillation circuit  112  is supplied to the reception circuit  111 . The reception circuit  111  performs a reception process using the reference frequency signal. 
     In addition, the reference frequency signal generated by the oscillation circuit  112  is supplied to an amplifier circuit  113 . The amplifier circuit  113  amplifies the reference frequency signal serving as a differential signal. 
     A reference frequency signal (e.g. signal CKx) having one of phases in the differential signal amplified by the amplifier circuit  113  of the first tuner unit  110  is then output from a terminal  110   e , and supplied to a terminal  120   d  of the second tuner unit  120 . A reference frequency signal (e.g. signal CKy) having the other phase in the differential signal amplified by the amplifier circuit  113  is output from a terminal  110   f , and supplied to a terminal  130   d  of the third tuner unit  130 . 
     In this way, a reference frequency signal generated by each tuner unit  110  is sequentially supplied to the tuner units  120 ,  130 , and so on at the later stage. A path through which a reference frequency signal is supplied will be described below. A reference frequency signal having one of phases in the differential signal amplified by the amplifier circuit  123  of the second tuner unit  120  is supplied from a terminal  120   e  to a terminal  14   d  of the fourth tuner unit  140 . A reference frequency signal having the other phase in the differential signal amplified by the amplifier circuit  123  is supplied from a terminal  120   f  to a terminal  150   d  of the fifth tuner unit  150 . 
     A reference frequency signal having one of phases in the differential signal amplified by the amplifier circuit  133  of the third tuner unit  130  is supplied from a terminal  130   e  to a terminal  160   d  of the sixth tuner unit  160 . A reference frequency signal having the other phase in the differential signal amplified by the amplifier circuit  133  is supplied from a terminal  130   f  to a terminal  170   d  of the seventh tuner unit  170 . 
     Furthermore, a reference frequency signal having one of phases in the differential signal amplified by the amplifier circuit  143  of the fourth tuner unit  140  is supplied from a terminal  140   e  to a terminal  180   d  of the eighth tuner unit  180 . A reference frequency signal having the other phase in the differential signal amplified by the amplifier circuit  143  is supplied from a terminal  140   f  to a terminal  190   d  of the ninth tuner unit  190 . 
     Image signals and audio signals acquired by the output terminals  110   b  to  190   b  of the tuner units  110  to  190  are then supplied to the television signal processing unit  90 . 
     Although  FIG. 6  illustrates no termination resistor, termination resistors similar to the termination resistors  34  and  35  in the example of  FIG. 1  may also be, for example, installed at the tuner units  150 ,  160 ,  170 ,  180 , and  190 , which do not have another tuner unit connected thereto at the later stage. Alternatively, no termination resistor may also be configured to be connected thereto. The tuner units  150 ,  160 ,  170 ,  180 , and  190 , which do not have another tuner unit connected thereto at the later stage, may also have the amplifier circuits  153 ,  163 ,  173 ,  183 , and  193  enter a sleep state, respectively. No termination resistor has to be connected in the sleep state. 
     This reception device according to the present disclosure illustrated in  FIG. 6  includes the nine tuner units  110  to  190 , but reference frequency signals used by these nine tuner units  110  to  190  to perform signal processing are oscillation signals acquired from a single crystal oscillator  99 . The reference frequency signals acquired by the oscillation circuits  112  to  192  in the nine tuner units  110  to  190  thus have completely the same frequency. 
     Accordingly, the reception device according to the present disclosure has no error in reference frequency signals in the nine tuner units  110  to  190 , causing no radio disturbance due to the error in the reference frequency signals. 
     Furthermore, a signal having one of phase and a signal having the other phase in a reference frequency signal (signal having one of the phases in a differential signal) that is a differential signal generated by a single tuner unit (e.g. tuner unit  110 ) are supplied to two other tuner units (e.g. tuner units  120  and  130 ) in the example of  FIG. 6 . Accordingly, the oscillation circuits  112  to  192  in the tuner units  110  to  190  and the amplifier circuits  113  to  193  that amplify reference frequency signals can output differential signals without converting them into single type signals. There is no need to convert differential signals into single type signals, so that it is possible to simplify the circuit configurations and to prevent signals from being deteriorated in conversion. In addition, all the tuner units  110  to  190  can acquire reference frequency signals having preferable characteristics. 
     When a differential signal is supplied from the tuner unit at each stage to the tuner unit at the later stage, it is preferable to transmit a signal having each phase included in the differential signal through signal lines disposed as close as possible. 
     For example, as illustrated in  FIG. 7 , a transmission path  80  in which two signal lines  81  and  82  are close is used to supply differential signals (reference frequency signals) output from the terminals  110   e  and  110   f  of the first tuner unit  110  around the second and third tuner units  120  and  130 . In this case, it is preferable to dispose the second and third tuner units  120  and  13 , to which these differential signals are supplied, at close positions on a substrate, and to transmit the differential signals to as close positions as possible to the terminals  120   a  and  130   a  of the tuner units  120  and  130  through the transmission path  80 . 
     A differential signal output from the second tuner unit  120  and a differential signal output from the third tuner unit  130  are also transmitted through the transmission line  80  in which two signal lines are similarly close. 
     Transmission in a differential signal scheme as illustrated in  FIG. 7  causes two differential signals to reverse and neutralize magnetic fields and electric fields generated by the transmission, thereby providing a preferable characteristic with effects from the noise reduced. Thus, a reference frequency signal used by each of the tuner units  110  to  190  has a preferable characteristic. 
     4. Modified Example 
     Additionally, the number of tuner units disposed in the example of each of the embodiments illustrated in  FIGS. 1 and 6  is a preferred example. Any other number of tuner units may also be disposed. A reference frequency signal generated by an oscillation circuit in a tuner unit is amplified by an amplifier circuit, and supplied to the tuner unit at the later stage in each example. However, a reference frequency signal may also be supplied to the tuner unit at the later stage without being amplified by an amplifier circuit. 
     Signals received by a single antenna  1  are supplied to the tuner units  10  to  40  and  110  to  190  in the respective examples of  FIGS. 1, 5, and 6 . However, for example, the respective tuner units may also serve as both of tuners that receive terrestrial broadcasting signals and tuners that receive satellite broadcasting signals, and a plurality of antennas may be connected thereto. Alternatively, a first group of tuner units in a plurality of tuner units may serve as tuner units that receive terrestrial broadcasting signals, and a second group of tuner units may serve as tuner units that receive satellite broadcasting signals. 
     Additionally, the present technology may also be configured as below. 
     (1) 
     A reception device including: 
     first and second reception circuits configured to receive transmission signals; 
     a first oscillation circuit configured to generate a differential signal having a predetermined frequency on the basis of an oscillation signal acquired from a connected crystal oscillator, and to supply the generated differential signal to the first reception circuit as a reference frequency signal; and 
     a second oscillation circuit configured to be supplied with an oscillation signal having one of phases in the differential signal acquired by the first oscillation circuit, to generate a differential signal having a predetermined frequency on the basis of the supplied oscillation signal, and to supply the generated differential signal to the second reception circuit as a reference frequency signal. 
     (2) 
     The reception device according to (1), further including: 
     a third reception circuit configured to receive a transmission signal; and 
     a third oscillation circuit configured to be supplied with an oscillation signal having other of the phases in the differential signal acquired by the first oscillation circuit, to generate a differential signal having a predetermined frequency on the basis of the supplied oscillation signal, and to supply the generated differential signal to the third reception circuit as a reference frequency signal. 
     (3) 
     The reception device according to (2), 
     wherein a signal line that transmits the oscillation signal having the one of the phases from the first oscillation circuit to the second oscillation circuit is at least partially disposed close to a signal line that transmits the oscillation signal having the other of the phases from the first oscillation circuit to the third oscillation circuit. 
     (4) 
     The reception device according to (2) or (3), further including: 
     a fourth reception circuit configured to receive a transmission signal; and 
     a fourth oscillation circuit configured to be supplied with an oscillation signal having one of phases in the differential signal acquired by the second oscillation circuit, to generate a differential signal having a predetermined frequency on the basis of the supplied oscillation signal, and to supply the generated differential signal to the fourth reception circuit as a reference frequency signal. 
     (5) 
     The reception device according to any one of (1) to (5), including: 
     an amplifier circuit configured to amplify the differential signal acquired by the first oscillation circuit, 
     wherein an oscillation signal having one of phases in the differential signal amplified by the amplifier circuit is supplied to the second oscillation circuit. 
     (6) 
     The reception device according to any one of (1) to (5), including: 
     a termination resistor configured to be connected to an output unit of the amplifier circuit for an oscillation signal having other of the phases. 
     (7) 
     An electronic apparatus including: 
     first and second reception circuits configured to receive transmission signals; 
     a first oscillation circuit configured to generate a differential signal having a predetermined frequency on the basis of an oscillation signal acquired from a connected crystal oscillator, and to supply the generated differential signal to the first reception circuit as a reference frequency signal; 
     a second oscillation circuit configured to be supplied with an oscillation signal having one of phases in the differential signal acquired by the first oscillation circuit, to generate a differential signal having a predetermined frequency on the basis of the supplied oscillation signal, and to supply the generated differential signal to the second reception circuit as a reference frequency signal; and 
     a processing unit configured to process the transmission signals received by the first and second reception circuits. 
     Furthermore, the configurations and processes recited in the claims of the present disclosure are not limited to the examples of the embodiments described above. It is obvious to those skilled in the art that various modifications, combinations, and other embodiments are possible insofar as they are within the technical scope of the appended claims 
     REFERENCE SIGNS LIST 
     
         
           1  antenna 
           10 ,  20 ,  30 ,  40 ,  110 ,  120 ,  130 ,  140 ,  150 ,  160 ,  170 ,  180  tuner unit 
           11 ,  21 ,  31 ,  41 ,  111 ,  121 ,  131 ,  141 ,  151 ,  161 ,  171 ,  181  reception circuit 
           12 ,  22 ,  32 ,  42 ,  112 ,  122 ,  132 ,  142 ,  152 ,  162 ,  172 ,  182  oscillation circuit 
           13 ,  23 ,  33 ,  43 ,  113 ,  123 ,  133 ,  143 ,  153 ,  163 ,  173 ,  183  amplifier circuit 
           11   a  radio frequency unit 
           11   b  modulation unit 
           11   c  locally generated signal generating unit 
           14 ,  24 ,  34 ,  35  termination resistor 
           80  transmission path 
           81 ,  82  signal line 
           90  television signal processing unit 
           99  crystal oscillator