Patent Publication Number: US-9431697-B2

Title: USB cable antenna

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application is a national stage of International Application No. PCT/JP2012/059885 filed on Apr. 11, 2012 and claims priority to Japanese Patent Application No. 2011-111163 filed on May 18, 2011, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a USB cable antenna obtained by extending the function of a USB (Universal Serial Bus) cable used for input/output of an information terminal device. 
     To receive TV broadcasting by an information terminal device such as a mobile phone, one of the method of providing a dedicated receiving antenna inside the information terminal device and the method of capturing antenna input from an earphone terminal to listen to an audio signal is generally used. 
     There is also a desire to receive TV broadcasting in a room in which there is no antenna receptacle for TV broadcasting such as a kitchen in the home. In such a case, using a power transmission cable as an antenna for TV broadcasting is proposed (see, for example, Patent Literature 1). 
     According to the technology described in Patent Literature 1, the distance between an inductor for high-frequency cutoff provided on the side of a power supply circuit of a power transmission cable and an inductor for high-frequency cutoff provided on the side of a mobile terminal is set to an integral multiple of the ¼ wavelength of the carrier frequency of received TV broadcasting or the like. Accordingly, TV broadcasting or the like in a wide frequency band can be received. 
     Also, a receiving apparatus capable of obtaining sufficient antenna characteristics even if a connector is shared when a cable used as an antenna is caused to transmit another signal whose frequency overlaps is proposed by the present inventors (see Patent Literature 2). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2010-157991A 
     Patent Literature 2: JP 2010-219904A 
     SUMMARY 
     Technical Problem 
     Under such circumstances, there is as much need to desire to listen to FM radio or view TV on an information terminal device as in the past. However, with an increasingly thinner and smaller size of information terminal devices in recent years, there is a shortage of space in which many connectors are arranged. 
     Thus, if a USB cable used for signal transmission and power supply of all information terminal devices can be used as an antenna to receive a radio wave of television broadcasting or the like, the effect thereof is powerful. 
     An object of the present disclosure is to provide a USB cable antenna capable of receiving a radio wave of FM radio or TV by using a USB cable connected to a USB terminal of an information terminal device and provided with an antenna function of a high-frequency signal. 
     Solution to Problem 
     To solve the above issues, according to an embodiment of the present disclosure, there is provided a USB cable antenna which also uses a USB cable as an antenna that receives a high-frequency signal in a desired band, by connecting a metal shield of the USB cable to an ID terminal of a USB connector connected to the USB cable of a predetermined length connected to an information terminal device, connecting a high-frequency cutoff element having a high impedance for the high-frequency signal in the desired band to both ends of a power supply line and a ground line of the USB cable, and connecting a common mode choke having the high impedance for the high-frequency signal in the desired band to both ends of a transmission line of a differential signal of the USB cable. 
     The high-frequency signal in the desired band received by the antenna is a signal of one or a plurality of bands of a FM band, a VHF band, and a UHF band. 
     Advantageous Effects of Invention 
     According to a USB cable antenna in the present disclosure, a USB cable necessary for connecting an information terminal device and a host computer can be used as a high-frequency antenna to receive television broadcasting or the like and therefore, there is no need to provide a built-in antenna on the side of the information terminal device. In addition, there is no need to provide a dedicated connector to connect a receiving antenna of television broadcasting or the like on the side of the information terminal device and therefore, further miniaturization and slimming down of the information terminal device can be realized. 
     Additional features and advantages are described herein, and will be apparent from the following Detailed Description and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic diagram showing an embodiment of a USB cable antenna according to the present disclosure. 
         FIGS. 2(A) to 2(D)  are diagrams showing concrete examples of the USB cable antenna having an A-type USB connector connected to one end thereof and a B-type USB connector connected to the other end thereof. 
         FIGS. 3(A) and 3(B)  are diagrams showing eye patterns when compliance tests of a differential signal of USB 1.1 and USB 2.0 are performed by setting the DC resistance of a ferrite bead (FB) inserted into a ground line to 1Ω and the high-frequency resistance of a common mode choke inserted into a differential signal line to 90Ω (100 MHz) in the USB cable antenna shown in  FIG. 2 . 
         FIGS. 4(A) and 4(B)  are diagrams showing eye patterns when compliance tests of a differential signal of USB 1.1 and USB 2.0 are performed by setting the DC resistance of a ferrite bead (FB) inserted into a ground line to 0.05Ω and the high-frequency resistance of a common mode choke inserted into a differential signal line to 90Ω (100 MHz) in the USB cable antenna shown in  FIG. 2 . 
         FIGS. 5(A) and 5(B)  are diagrams showing eye patterns when compliance tests of a differential signal of USB 1.1 and USB 2.0 are performed by setting the DC resistance of a ferrite bead (FB) inserted into a ground line to 0.05Ω and the high-frequency resistance of a common mode choke inserted into a differential signal line to 120Ω (100 MHz) in the USB cable antenna shown in  FIG. 2 . 
         FIGS. 6(A) and 6(B)  are diagrams showing frequency-gain characteristics when TV waves of the VHF band (A) and the UHF band (B) are received using the USB cable antenna shown in  FIG. 2 . 
         FIG. 7  is a diagram showing the relationship between the frequency and high-frequency impedance when a current is passed to the ferrite bead (FB) provided in a power transmission line of the USB cable antenna. 
         FIG. 8  is a diagram showing a concrete configuration of a USB-A connector to which the USB cable connector is connected. 
         FIG. 9  is a diagram (when a ferrite core is inserted) showing frequency-gain characteristics when (A) no AC adapter is connected to the USB cable antenna and (B) the AC adapter is connected to the USB cable antenna. 
         FIG. 10  is a diagram (when a ferrite core is not inserted) showing frequency-gain characteristics when (A) no AC adapter is connected to the USB cable antenna and (B) the AC adapter is connected to the USB cable antenna. 
     
    
    
     DETAILED DESCRIPTION 
     As described above, with further slimming down and miniaturization of recent information terminal devices, it is becoming more difficult to secure a space to provide an antenna needed to receive a radio wave of TV broadcasting on the side of the information terminal device or a special connector connected to an external antenna. For example, some earphone antennas have been proposed by inventors and the like as an antenna to receive a radio wave of TV broadcasting. However, the size of diameter of a terminal for earphone needed for the earphone antenna is also an obstacle to further slim down the information terminal device. 
     Thus, some thin information terminal devices in recent years are provided with only a USB terminal without having any earphone terminal Such information terminal devices are charged from a host computer and various signals are transmitted between the host computer and the information terminal devices by using the USB cable. 
     To solve the above problem, the inventors focused on a USB terminal mounted on many information terminal devices and a USB cable connected thereto and attempted various ideas and experiments by considering whether the USB cable can be used as a receiving antenna of television broadcasting or the like. As a result, as will be described below, the inventors devised a method of using a USB cable as an antenna capable of receiving a radio wave of television broadcasting or the like. 
     An embodiment (hereinafter, called the “present example”) of a USB cable antenna according to the present disclosure will be described below with reference to  FIGS. 1 to 10  and the description will be provided in the order shown below: 
     1. Schematic configuration of a USB cable antenna 
     2. Concrete example of the USB cable antenna 
     3. Verification of maintenance of the USB cable function of the USB cable antenna 
     4. Frequency-gain characteristics of the USB cable antenna 
     5. High-frequency impedance characteristics of FB inserted into a power supply line of the USB cable antenna 
     6. Concrete example of the USB-A connector to which the USB cable connector is connected 
     7. Characteristics comparison when an AC adapter is connected to the USB cable antenna 
     &lt;Schematic Configuration of a USB Cable Antenna&gt; 
       FIG. 1  is a diagram illustrating the configuration of a USB cable antenna in the present example and the operation principle thereof. As shown in  FIG. 1 , a female USB connector for USB cable connection is provided on the side of an information terminal device (hereinafter, also called a “set”). The USB connector provided on the set side will be called a “set-side USB connector  10 ” below. 
     Then, a male B-type USB connector is attached to one end of a coaxial shielding wire of an appropriate length (for example, about 95 to 115 cm). Hereinafter, the male USB connector will be called a “cable-side USB-B connector  20 ” to distinguish from the set-side USB connector  10 . 
     A male A-type USB connector is attached to the other end of the USB cable. The USB connector will be called a “cable-side USB-A connector  30 ”. The USB connector is a standard-type USB connector and is connected to the host computer side. 
     First, the set-side USB connector  10  will be described with reference to  FIG. 1  and then a concrete connecting relation to the USB cable antenna in the present example will be described. 
     In general, the set-side USB connector  10  (female type) and the cable-side USB-B connector  20  (male type) each have five connection pins and a shielding terminal. A μUSB-B connector is normally used as the set-side USB connector  10  and the cable-side USB-B connector  20 . In contrast, the cable-side USB-A connector  30  connected to the host computer side is a standard-type A-type USB connector capable of supplying power. 
     In recent years, however, the distinction between the A type and the B type has become blurry and an A-type or AB-type (USB connector used for both of the host side and the set side) μUSB connector may be used as the set-type USB connector  10 . 
     As shown in  FIG. 1 , 1-pin of the set-side USB connector  10  is a Vbus/MIC terminal for power supply and power is fed from the side of the host computer (not shown) to the information terminal device (set) via 1-pin and also a voltage is supplied to an earphone microphone or the like connected to the set. A ferrite bead  11  for high-frequency cutoff is connected in series to a line to which 1-pin of the set-side USB connector  10  is connected. Hereinafter, the ferrite bead may be abbreviated simply as “FB”. 
     2-pin and 3-pin of the set-side USB connector  10  are terminals of a signal line of differential signals to be transmitted and received through the USB cable, and when an audio signal is input into these terminals, 2-pin (D− terminal) functions as a terminal of an L channel and 3-pin (D+ terminal) functions as a terminal of an R channel. A common mode choke  12  is connected to a line to which 2-pin and 3-pin used for differential are connected. Then, high-frequency signals are cut off and only an audio signal is passed by the common mode choke  12 . In the description that follows, the high-frequency signal may also be called an “RF signal” or “antenna signal”. 
     4-pin of the set-side USB-B connector  10  is an ID terminal (ID is an abbreviation of Identification, also called an “identification terminal”) to identify the type of an inserted plug and the use to which the plug is applied. 
     In the set-side USB connector  10  in the present example, as shown in  FIG. 1 , 4-pin used as the ID terminal is used as an antenna terminal to receive TV broadcasting or the like. Thus, a capacitor  14  of about 1000 pF is connected in series to a line to which 4-pin is connected and an antenna signal supplied to 4-pin via the capacitor  14  is supplied to a tuner circuit (not shown) in the set. 
     4-pin of the set-side USB-B connector  10  is a pin naturally used as a normal ID terminal. High-frequency signals of television and the like can be an obstacle in realizing the function as a normal ID terminal and an FB  13  as a high-frequency cutoff element is connected in parallel with the capacitor  14  to the line to which 4-pin is connected to remove such high-frequency signals. Accordingly, an ID signal from which high-frequency antenna signals such as a television signal have been removed is output to an ID identification circuit (not shown) on the set side. 
     Incidentally, 5-pin of the set-side USB connector  10  is a ground terminal for grounding and a line to which 5-pin is connected is connected and grounded to each of external shields of the cable-side USB-B connector  20  and set described later. 
     As described above, a substrate  22  is provided at one end of a coaxial shielding wire  21  in the USB cable antenna shown in  FIG. 1  and the male cable-side USB-B connector  20  is connected to the substrate  22 . Like the set-side USB connector  10 , a μUSB connector is used normally for the cable-side USB-B connector  20 , but in addition, a μUSB connector of the A type or AB type may also be used. 
     A resistor  23  is connected between the ID terminal (4-pin) of the cable-side USB-B connector  20  and the ground line and based on the value of the resistor  23 , the USB connector of which use is connected and how the USB cable is used can be known. 
     In addition, a metal shield  27  of the coaxial shielding wire  21  is connected to the ID terminal and the metal shield  27  functions as a monopole antenna described later. 
     Also, an FB  24  as an element to cut off high-frequency signals is connected to a power supply line to which 1-pin of the cable-side USB-B connector  20  shown in  FIG. 1  is connected. A common mode choke  25  is connected to 2-pin (D− terminal) and 3-pin (D+ terminal) that transmit a differential signal. Like the common mode choke  12  provided in the set-side USB connector  10 , the common mode choke  25  also has a function to cut off high-frequency waves. Similarly, an FB  26  as an element to cut off high-frequency waves is connected to the ground line to which 5-pin of the cable-side USB-B connector  20 . 
     As shown in  FIG. 1 , the standard A-type cable-side USB-A connector  30  is connected to the other end of the coaxial shielding wire  21 . An FB  31  for cutting off high-frequency waves is connected to 1-pin of the cable-side USB-A connector  30 . A common mode choke  32  is connected to the signal line to which 2-pin and 3-pin to which a differential signal is supplied are connected. Further, an FB  33  for cutting off high-frequency waves is connected to the ground line to which 5-pin is connected. To satisfy both of the ordinary USB cable signal function and the antenna function of a high-frequency signal like a television signal, the DC resistance of the FB  33  inserted into the ground line is desirably 0.25Ω or less. As the common mode choke  32 , for example, a product having 90Ω for high-frequency waves or a product having 120Ω is used. 
     In the USB cable antenna in the present example, the metal shield  27  as a skin conductor of the coaxial shielding wire  21  is connected to the ID terminal (4-pin) of the cable-side USB-B connector  20 . As shown in  FIG. 1 , the metal shield  27  connected to the ID terminal is a shielding line that is different from the ground line. 
     The reason why the metal shield  27  is connected to the ID terminal (4-pin) to receive a radio wave like a television signal is as follows: 
     The transfer clock used for signal transfer in USB 2.0 is fixed to 480 Mbps. A signal of the transfer clock operates between the differential signal line and the ground line and thus, if the ground line of a USB cable is used as an antenna of a television signal, the antenna is in a state in which the clock signal of 480 Mbps of USB is superimposed on a RF signal of television or the like. The so-called “fogging” occurs. 
     Therefore, when a USB cable is used as an antenna for television broadcasting, the ground line cannot be used as an antenna. As a result of experiment, the inventors found that the problem can be solved by using the metal shield  27  that is different from the ground line. 
     Incidentally, the clock of 480 Mbps in USB 2.0 corresponds to a frequency of 240 MHz and thus, the band particularly affected adversely is the VHF-H (high) band. 
     When the male cable-side USB-B connector  20  is inserted into the female set-side USB-B connector  10 , it is necessary to discriminate (detect) whether an antenna capable of receiving a radio wave of television broadcasting or the like is inserted. Thus, the resistor  23  is inserted between the line to which the ID terminal (4-pin) of the cable-side USB-B connector  20  and the ground line to which 5-pin is connected. The value of resistance of the resistor  23  is different depending on the type of the cable-side USB-B connector  20 , in other words, what the cable-side USB-B connector  20  is used for. 
     Therefore, by detecting the value (value of resistance) of the resistor  23 , whether a USB connector having an antenna function of television broadcasting or the like is inserted can be detected. 
     The value of resistance of the resistor  23  is normally high impedance (hundreds of kΩ) and thus, the ID line and the ground line are open at high frequencies and antenna characteristics are not affected from the ground line to the ID line. However, to be noted is a case of high-frequency connection by a capacitor of connection capacity or the like after passing FB  64  to  67  connected to each line other than the ID line. In such a case, a high-frequency current flows to each terminal, causing the degradation of antenna characteristics. 
     &lt;Concrete Example of the USB Cable Antenna&gt; 
       FIGS. 2(A) to 2(D)  show samples of the above USB cable antenna.  FIG. 2(A)  is a plan view when viewed from above,  FIG. 2(B)  is a sectional view of the B-type cable-side USB-B connector  20  (here, a μUSB-B connector),  FIG. 2(C)  is a sectional view of the A-type cable-side USB-A connector  30  (here, a standard-type USB-A connector), and  FIG. 2(D)  is a front view. The dimension of each figure is based on the standard of the USB connector and μUSB connector. In  FIGS. 2(A) to 2(D) , the same reference signs are attached to the same members as those in  FIG. 1 . 
     As shown in  FIG. 2 , the narrower side of the cable-side USB-B connector  20  has a width of 7 mm, which is suitable as a connection terminal of a mobile phone or the like proceeding toward further slimming down in the future. On the other hand, the narrower side in the section of the cable-side USB-A connector  30  connected to the host computer has a width of 7.8 mm. 
     In the Japanese television broadcasting, the VHF band of 90 to 108 MHz (1 to 3 ch) and 170 to 222 MHz (4 to 12 ch) and the UHF band of 470 to 770 MHz (13 to 62 ch) are used. Incidentally, the VHF band may be divided to call 90 to 108 MHz as the VHF-L (low) band and 170 to 222 MHz as the VHF-H (high) band. In the USB cable antenna in the present example, the length of the cable is adjusted to 115 cm, which is about ¾ the wavelength (¾·λ) of 200 MHz so as to be able of receive both of the VHF-H (high) band and the UHF band. Incidentally, UHF is received by high-frequency excitation. 
     &lt;Verification of Maintenance of the USB Cable Function of the USB Cable Antenna&gt; 
     When a television signal is received by connecting the cable-side USB-B connector  20  of the above USB cable antenna in the present example to the set-side USB connector  10 , whether the original USB function is maintained is important. Thus, a compliance test to verify whether the function of USB is degraded in the USB cable antenna of the present example was performed.  FIGS. 3(A) to 5(B)  are diagrams showing eye patterns of the compliance test to check whether the USB cable antenna in the present example satisfies two standards of USB 1.1 and USB 2.0. 
       FIGS. 3(A) and 3(B)  shows results of the compliance test of USB by setting the DC resistance of the FB  26 ,  33  of the ground line to 1Ω and the common mode chokes  25 ,  32  connected to the D− line and D+ line that transmit a differential signal to 90Ω (100 MHz) in the USB cable antenna shown in  FIG. 2 .  FIG. 3(A)  shows an eye pattern  40   a  of the compliance test of USB 1.1 and  FIG. 3(B)  shows an eye pattern  40   b  of the compliance test of USB 2.0. 
     The eye pattern is also called an eye diagram or an eye opening ratio and is created by sampling and superimposing the transition of a signal waveform many times and graphically showing the result. The horizontal axis represents the time and the vertical axis represents the voltage. If the eye pattern is viewed and a plurality of signal waveforms is superimposed in the same position (timing and voltage), the waveform is considered to be a high-quality waveform and conversely, if positions (timing and voltage) of signal waveforms are shifted and signal waveforms overlap with a hexagonal shape (template) in the center, the waveform is considered to be a low-quality waveform. It is also known that a waveform of degraded transmission characteristics has a hexagonal shape (template  43 ) in the center that is thin and flat and the area thereof is small. The test is called an eye pattern test (or an eye diagram test) because the relation between the signal lines and the template is similar to the shape of an open human eye. 
     The eye pattern  40   a  shows the compliance test result of USB 1.1 when the DC resistance of FB inserted into the ground line is 1Ω and the impedance of the common mode choke at 100 MHz is 90Ω. In the compliance test of USB 1.1, differential signals  41   a ,  42   a  passing through the signal lines of D+=0.35 V and D−=−0.35 V and having a phase difference of 180° are simultaneously displayed. Viewing the displayed eye pattern  40   a  shows that a portion of waveforms of the differential signal  41   a  or  42   a  overlaps with a template  43   a  in the hexagonal shape. From the above result, the USB cable antenna in the present example does not satisfy the function of USB 1.1, that is, the USB cable antenna failed (NG) in the compliance test of USB 1.1. 
     On the other hand, the eye pattern  40   b  in  FIG. 3(B)  shows the compliance test result of USB 2.0 when the DC resistance of FB inserted into the ground line is 1Ω and the impedance of the common mode choke at 100 MHz is 90Ω. In the compliance test of USB 2.0, differential signals  41   b ,  42   b  passing through the signal lines of D+=0.4 V and D−=−0.4 V and having a phase difference of 180° are simultaneously displayed. Viewing  FIG. 3(B)  shows that differential signals  41 ,  42  propagated through the line to which 2-pin and 3-pin are connected are positioned between parallel lines of D+=0.4 V, D−=−0.4 V and further, the hexagonal template  43  is positioned inside a region surrounded by these two differential signals  41 ,  42 . 
     That is, as far as USB 2.0 is concerned,  FIG. 3(B)  shows that even if 4-pin of the USB connector to which a cable is connected is used also as an antenna input terminal, the eye pattern test is passed, in other words, standards of USB 2.0 are satisfied. In the standards of USB 2.0, the clock of transmission of a USB signal is 480 Mbps and belongs to the VHF band (240 MHz) as a frequency band. 
       FIGS. 4(A) and 4(B)  show eye patterns  50   a ,  50   b  showing results of performing the compliance test of differential signals of USB 1.1 and USB 2.0 using the USB cable antenna shown in  FIG. 2 .  FIGS. 4(A) and 4(B)  are different from  FIGS. 3(A) and 3(B)  in that the DC resistance of the FB  26 ,  33  inserted into the ground line is set to 0.05Ω. The impedance of the common mode chokes  25 ,  32  at 100 MHz remains 90Ω. 
     In the eye pattern  50   a , as shown in  FIG. 4(A) , all differential signal lines  51   a ,  52   a  of D+ and D− surround an eye pattern  53   a . Also in the eye pattern  50   b  shown in  FIG. 4(B) , differential signal lines  51   b ,  52   b  of differential signal lines D+ and D− surround an eye pattern  53   b  and do not overlap with each other. The result means that the USB cable antenna passes the compliance tests of USB 1.1 and USB 2.0, that is, the standards of both of USB 1.1 and USB 2.0 are satisfied. 
       FIGS. 5(A) and 5(B)  also show eye pattern diagrams showing compliance test results of the USB cable antenna shown in  FIG. 2 .  FIGS. 5(A) and 5(B)  are different from  FIGS. 4(A) and 4(B)  in that a product whose impedance at 100 MHz is 120Ω is used as the common mode choke  25 ,  32  inserted into the differential signal lines. The DC resistance of the FB  26 ,  33  of the ground line remains the same resistance of 0.05Ω as in  FIG. 4 . 
     In the compliance test of USB 1.1 shown in  FIG. 5(A) , all differential signal lines  61   a ,  62   a  of D+ and D− surround an eye pattern  63   a  and also in the compliance test of USB 2.0 shown in  FIG. 5(B) , all differential signal lines  61   b ,  62   b  of D+ and D− are similarly outside an eye pattern  63   b  and do not overlap with each other. 
     From the above results, it is verified that a USB cable antenna satisfying both standards of USB 1.1 and USB 2.0 can be obtained by appropriately selecting the DC resistance of the FB  26 ,  33  inserted into the ground line and the impedance of the common mode chokes  25 ,  32  inserted into the differential signal lines. 
     &lt;Frequency-Gain Characteristics of the USB Cable Antenna&gt; 
     The USB cable antenna in the present example shown in  FIGS. 1 and 2  constitutes, as described above, a monopole antenna between the set and the ground (GND). An experiment of receiving radio waves of television broadcasting in the VHF-H band and the UHF band using the USB cable antenna was conducted. That is, a sample of the USB cable antenna shown in  FIG. 2  is connected to the female set-side USB connector  10  (see  FIG. 1 ) to investigate transmission characteristics of a high-frequency signal such as a television wave. 
     Table 1 and  FIG. 6(A)  show frequency-gain characteristics when television broadcasting in the VHF band is received by the USB cable antenna shown in  FIG. 1 . 
     In the VHF band of 170 to 220 MHz, as shown in Table 1 and  FIG. 6(A) , gain characteristics of −5 dB (−4.04 dB at 210 MHz) or more are exhibited in vertical polarization and gain characteristics of −20 dB (−17.24 dB at 210 MHz) or more are exhibited in horizontal polarization (see Table 1). 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Frequency [MHz] 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 188.5 
                 192.5 
                 194.5 
                 198 
                 204 
                 210 
                 216 
                 222 
               
               
                   
                   
               
            
           
           
               
               
            
               
                   
                 Vertical polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak [dBd] 
                 −3.27 
                 −2.89 
                 −2.97 
                 −3.10 
                 −3.40 
                 −4.04 
                 −4.68 
                 −4.24 
               
            
           
           
               
               
            
               
                   
                 Horizontal polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak [dBd] 
                 −15.67 
                 −15.49 
                 −15.37 
                 −15.30 
                 −16.00 
                 −17.24 
                 −18.08 
                 −17.90 
               
               
                   
               
            
           
         
       
     
     Table 2 and  FIG. 6(B)  show frequency-gain characteristics when television broadcasting in the UHF band is received and in the UHF band of 470 to 870 MHz, as shown in  FIG. 6(B) , gain characteristics of −12 dB or more are exhibited in vertical polarization and gain characteristics of −8 dB or more are exhibited in horizontal polarization. 
     These results show that the USB cable antenna shown in  FIGS. 1 and 2  sufficiently fulfills the function as an antenna of the VHF-H band and the UHF band of television broadcasting. These results mean that the USB cable antenna is also applicable as an antenna for multimedia broadcasting planned to be broadcast using the VHF band. 
     
       
         
           
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                 Frequency [MHz] 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 470 
                 520 
                 570 
                 620 
                 670 
                 720 
                 770 
                 906 
               
               
                   
                   
               
            
           
           
               
               
            
               
                   
                 Vertical polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak 
                 −8.80 
                 −10.09 
                 −9.53 
                 −11.61 
                 −10.36 
                 −3.18 
                 −7.85 
                 −3.98 
               
               
                 [dBd] 
               
            
           
           
               
               
            
               
                   
                 Horizontal polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak 
                 −5.00 
                 −4.29 
                 −1.64 
                 −7.34 
                 −5.96 
                 −5.15 
                 −5.25 
                 −2.58 
               
               
                 [dBd] 
               
               
                   
               
            
           
         
       
     
     &lt;High-Frequency Impedance Characteristics of FB Inserted into a Power Supply Line of the USB Cable Antenna&gt; 
     Next, the FB  24 ,  31  connected to a power supply line (Vbus line) shown in  FIG. 1  will further be described. In contrast to the FB  26 ,  33  connected to the ground line, the FB  24 ,  31  are special ferrite beads (FB) capable of maintaining high-frequency characteristics even if a current flows. 
     The FB normally used like the FB  26 ,  33  inserted into the ground line has a magnetic material around a coil and removes a high-frequency current by converting the high-frequency current into heat using a high impedance state at high frequencies, that is, a state of high high-frequency losses. That is, the FB plays the role as a high-frequency signal cutoff element. 
     The normal FB  26 ,  33  described above are produced while a coil is inside a magnetic material and thus, the magnetic material is saturated when the current increases. That is, in the normal FB, a closed magnetic circuit is formed and magnetic fluxes are confined and thus, saturation is more likely to be reached when a large current flows. Therefore, it becomes more difficult to maintain original characteristics. 
     In contrast, the FB  24 ,  31  provided in the line for power supply to which 1-pin of a USB terminal is connected are produced by taking a case when a large current flows into consideration and an open magnetic circuit is formed by a coil and a magnetic material. Thus, magnetic fluxes are not confined even if a magnetic material is present and therefore, even if a large current flows to the coil, the current is converted into heat only inside the coil and the magnetic material is structured to be less likely to be saturated. 
       FIG. 7  shows high-frequency impedance characteristics of the FB  24 ,  31  when a current is stepwise passed to a line to which the Vbus/MIC terminal (1-pin) of the USB cable antenna is connected. 
     As is evident from  FIG. 7 , approximately the same frequency characteristics are exhibited when no current is passed to the line to which 1-pin is connected (0 mA) and when currents are passed (100 mA, 300 mA, 500 mA, 700 mA). However, as shown in  FIG. 7 , it is verified that a little different frequency characteristics are exhibited when the magnitude of the current is 1 A (1000 mA). 
     It also turned out that insertion losses are about −20 dB to −27.5 dB in the band of 200 MHz to 700 MHz corresponding to the VHF band to the UHF band of television broadcasting. 
     Such a level of insertion losses can be considered to be a level allowing reception of the VHF band to the UHF band of television broadcasting. 
     &lt;Concrete Example of the USB-A Connector to which the USB Cable Connector is Connected&gt; 
     Next, a concrete example of the USB-A connector to which the USB cable antenna is connected will be described with reference to  FIG. 8 . 
     The dotted line in the center of  FIG. 8  shows a substrate  70  and the left side of the substrate  70  shows a USB-A plug inserted into the host. The right side of the substrate  70  shows a connector portion to which the USB cable antenna in the present example is connected. 
     In the USB-A plug on the left side of the substrate  30 , socket pins are arranged in a portion surrounded by a thick dotted line. That is, 1-pin  71  to which the power supply line (Vbus) is connected, 2-pin  72  to which the D− line of a differential signal is connected, 3-pin  73  to which similarly the D+ line is connected, and a socket pin of 4-pin  74  as the ID terminal are arranged in parallel from below. 5-pin  75  to which the ground line (GND) is connected is arranged above the 4-pin  74 . 
     The right side of the substrate  70  is a portion to which the USB cable antenna of the present example is connected. 1-pin  71   a  to which a line of Vbus is connected, 2-pin  72   a  and 3-pin  73   a  to which lines of differential signals D−, D+ are connected respectively, and 4-pin  74   a  to which a line of GND is connected are arranged from below. 5-pin  75   a  to which the metal shield  27  shown in  FIG. 1  is connected is provided above the 4-pin  74   a . The metal shield  27  connected to the 5-pin  75   a  fulfills, as described above, the function as an antenna by being connected to 4-pin (ID terminal) of the set-side USB connector  10  (μUSB-B connector) in  FIG. 1 . 
     The 1-pin  71   a  on the right side of the substrate  70  is connected to the 1-pin  71  of the USB-A plug on the left side of the substrate  70  via the FB  31  and the 2-pin  72   a  and the 3-pin  73   a  on the right side of the substrate  70  are connected to the 2-pin  72  and the 3-pin  73  of the USB-A plug on the left side of the substrate  70  via the common mode choke  32 . The 4-pin  74   a  to which the GND line is connected on the right side of the substrate  70  is connected to the 5-pin  75  as the GND terminal on the left side of the substrate  70 . 
     The 5-pin  75   a  to which the metal shield  27  of the USB cable antenna is connected on the right side of the substrate  70  is not connected to any terminal on the left side of the substrate  70  and is in an open state. 
     In general, a USB-A connector provided at one end of the USB cable antenna in the present example is connected to the host side including a power unit and so is more likely to be affected by noise generated by the power unit. Thus, in  FIG. 8 , pins are arranged on a straight line to make respective signal lines parallel so as to be less likely to be affected by noise from the unit. Accordingly, a USB cable antenna having the function as an antenna and less likely to be affected by noise from the power unit can be produced. 
     &lt;Characteristics Comparison when an AC Adapter is Connected to the USB Cable Antenna&gt; 
     If a charger (AC adapter) for USB is connected to the tip of a USB-A connector, the USB cable antenna in the present example can receive a television signal while being charged. Thus, an experiment to investigate to which extent frequency-gain characteristics of the USB cable antenna change when an AC adapter is connected to the tip of the USB-A connector and no AC adapter is connected was conducted. 
     Table 3, Table 4, and  FIGS. 9(A) and 9(B)  show frequency-gain characteristics in the VHF band of the USB cable antenna in the present example when no AC adapter is connected to the USB-A connector side to which the USB cable antenna is connected (A) and an AC adapter is connected (B). In the examples shown in  FIGS. 9(A) and 9(B) , a ferrite core (not shown) is arranged near the USB-A plug and the USB antenna cable wound around the ferrite core once or twice before making measurements. 
     It is clear from  FIGS. 9(A) and 9(B)  that if the ferrite core is inserted, changes of frequency-gain characteristics are small when the USB-A plug is not connected to the AC adapter (A) and the USB-A plug is connected to the AC adapter (B). 
     That is, viewing  FIGS. 9(A) and 9(B)  shows that near 210 MHz used for the USB cable antenna, frequency-gain characteristics hardly change when the USB cable antenna is not connected to the AC adapter in  FIG. 9(A)  (−26.06 dBd in vertical polarization and −7.84 Bd in horizontal polarization) and the USB cable antenna is connected to the AC adapter in  FIG. 9(B)  (−25.95 dBd in vertical polarization and −7.75 dBd in horizontal polarization) (see Table 3 and Table 4). 
     
       
         
           
               
               
             
               
                   
                 TABLE 3 
               
             
            
               
                   
                   
               
               
                   
                 Frequency [MHz] 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 188.5 
                 192.5 
                 194.5 
                 198 
                 204 
                 210 
                 216 
                 222 
               
               
                   
                   
               
            
           
           
               
               
            
               
                   
                 Vertical polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak [dBd] 
                 −26.01 
                 −25.15 
                 −25.49 
                 −25.28 
                 −25.40 
                 −26.06 
                 −27.13 
                 −26.21 
               
            
           
           
               
               
            
               
                   
                 Horizontal polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak [dBd] 
                 −10.17 
                 −8.95 
                 −8.61 
                 −7.86 
                 −7.40 
                 −7.84 
                 −8.70 
                 −9.19 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                   
                 TABLE 4 
               
             
            
               
                   
                   
               
               
                   
                 Frequency [MHz] 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 188.5 
                 192.5 
                 194.5 
                 198 
                 204 
                 210 
                 216 
                 222 
               
               
                   
                   
               
            
           
           
               
               
            
               
                   
                 Vertical polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak [dBd] 
                 −26.81 
                 −26.69 
                 −26.21 
                 −26.23 
                 −26.00 
                 −25.95 
                 −26.15 
                 −25.21 
               
            
           
           
               
               
            
               
                   
                 Horizontal polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak [dBd] 
                 −10.72 
                 −9.72 
                 −9.41 
                 −8.66 
                 −7.84 
                 −7.75 
                 −7.90 
                 −7.99 
               
               
                   
               
            
           
         
       
     
     Table 5, Table 6, and  FIGS. 10(A) and 10(B)  show changes of frequency-gain characteristics when no ferrite core is used. Like in  FIGS. 9(A) and 9(B) ,  FIG. 10(A)  shows a case when the USB cable antenna is not connected to the AC adapter and  FIG. 10(B)  shows a case when the USB cable antenna is connected to the AC adapter. Comparison of gains near 210 MHz in  FIGS. 10(A) and 10(B)  shows that while the gain is −26.75 dB in vertical polarization (see Table 5) and −8.15 dB in vertical polarization (see Table 5) when the AC adapter is present, the gain is −23.26 dB in vertical polarization (see Table 6) and −5.66 dB in vertical polarization (see Table 6) when no AC adapter is inserted. 
     The above results show that when television broadcasting in the VHF band is received, inserting a ferrite core on the side of the USB-A connector is effective in receiving a television signal in the VHF-H band regardless of whether or not an AC adapter is present. 
     
       
         
           
               
               
             
               
                   
                 TABLE 5 
               
             
            
               
                   
                   
               
               
                   
                 Frequency [MHz] 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 188.5 
                 192.5 
                 194.5 
                 198 
                 204 
                 210 
                 216 
                 222 
               
               
                   
                   
               
            
           
           
               
               
            
               
                   
                 Vertical polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak [dBd] 
                 −26.81 
                 −26.45 
                 −26.21 
                 −25.43 
                 −24.49 
                 −23.26 
                 −21.63 
                 −21.61 
               
            
           
           
               
               
            
               
                   
                 Horizontal polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak [dBd] 
                 −12.47 
                 −11.52 
                 −10.93 
                 −10.06 
                 −7.77 
                 −5.66 
                 −4.10 
                 −4.75 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                   
                 TABLE 6 
               
             
            
               
                   
                   
               
               
                   
                 Frequency [MHz] 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 188.5 
                 192.5 
                 194.5 
                 198 
                 204 
                 210 
                 216 
                 222 
               
               
                   
                   
               
            
           
           
               
               
            
               
                   
                 Vertical polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak [dBd] 
                 −25.81 
                 −25.65 
                 −25.77 
                 −25.73 
                 −26.15 
                 −26.75 
                 −28.75 
                 −29.37 
               
            
           
           
               
               
            
               
                   
                 Horizontal polarization 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Peak [dBd] 
                 −9.67 
                 −9.09 
                 −8.81 
                 −8.48 
                 −8.20 
                 −8.15 
                 −9.33 
                 −9.24 
               
               
                   
               
            
           
         
       
     
     In the foregoing, the USB cable antenna has been described as an embodiment of the present disclosure. A USB cable antenna according to the present disclosure naturally includes, in addition to the embodiment disclosed herein, various application examples and modifications without deviating from the spirit and scope of the present disclosure described in claims. 
     Additionally, the present technology may also be configured as below. 
     (1) A USB cable antenna which also uses a USB cable as an antenna that receives a high-frequency signal in a desired band, 
     by connecting a metal shield of the USB cable to an ID terminal of a USB connector connected to the USB cable of a predetermined length connected to an information terminal device, 
     connecting a high-frequency cutoff element having a high impedance for the high-frequency signal in the desired band to both ends of a power supply line and a ground line of the USB cable, 
     and connecting a common mode choke having the high impedance for the high-frequency signal in the desired band to both ends of a transmission line of a differential signal of the USB cable. 
     (2) The USB cable antenna according to (1), 
     wherein the high-frequency signal in the desired band received by the antenna is a signal of one or a plurality of bands of a FM band, a VHF band, and a UHF band. 
     (3) The USB cable antenna according to (1) or (2), 
     wherein a resistor to identify a type of the USB cable connected to the ID terminal is connected between an ID line to which the ID terminal is connected and the ground line of the USB cable. 
     (4) The USB cable antenna according to any one of (1) to (3), 
     wherein the high-frequency cutoff element inserted into the power supply line has the high impedance also when a current flows to the power supply line. 
     (5) The USB cable antenna according to any one of (1) to (4), 
     wherein a DC resistance of the high-frequency cutoff element inserted into the ground line is 0.25Ω or less. 
     (6) The USB cable antenna according to any one of (1) to (5), 
     wherein the impedance in the desired band of the common mode choke inserted into both ends of D− and D+ differential signal lines of the USB cable is 90Ω or more. 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims. 
     REFERENCE SIGNS LIST 
     
         
           21  coaxial shielding wire 
           10  set-side usb connector 
           20  cable-side usb-b connector 
           30  cable-side usb-a connector 
           11 ,  13 ,  26 ,  33  ferrite bead (fb) 
           12 ,  25 ,  32  common mode choke 
           24 ,  31  ferrite bead (fb: for power supply line) 
           14  capacitor 
           23  resistor 
           27  metal shield 
           40   a ,  40   b ,  50   a ,  50   b ,  60   a ,  60   b  eye pattern 
           41   a ,  42   a ,  41   b ,  42   b ,  51   a ,  52   a ,  51   b ,  52   b ,  61   a ,  62   a ,  61   b ,  62   b  d− or d+ differential signal 
           43   a ,  43   b ,  53   a ,  53   b ,  63   a ,  63   b  template