JP2012186585A - Television tuner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a television tuner capable of receiving television broadcast signals of plural frequency bands, without assigning a GPIO output terminal to be used for control of switching.SOLUTION: The television tuner is provided with: a tunable antenna; receiving circuits which respectively receive a broadcast signal of a first frequency band and that of a second frequency band; a first path which leads to a receiving circuit the broadcast signal of the first frequency band outputted from the tunable antenna tuned with the first frequency band; a second path which leads to a receiving circuit the broadcast signal of the second frequency band outputted from the tunable antenna tuned with the second frequency band; and a switching circuit which when a control voltage for tuning to be supplied to the tunable antenna is the tuning voltage of the first frequency band, connects the first path to the receiving circuit and disconnects the second path, and which when the control voltage for tuning is the tuning voltage of the second frequency band, connects the second path to the receiving circuit and disconnects the first path.

Description

  The present invention relates to a television tuner capable of receiving broadcast signals in a plurality of frequency bands.

  In recent years, terrestrial digital television broadcasting using a frequency band of 470 MHz to 710 MHz (770 MHz) has been popularized. In addition, with the spread of terrestrial digital television broadcasting, there is a plan to stop conventional terrestrial analog television broadcasting and to reallocate it to multimedia broadcasting for portable terminals in an empty frequency band by analog stopping. In digital terrestrial television broadcasting, a digital broadcasting standard called ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) is adopted. On the other hand, in multimedia broadcasting for mobile terminals by reassignment, a frequency band of 207.5 MHz to 222 MHz is used, and a digital broadcasting standard called ISDB-Tmm is scheduled to be adopted.

  In order to receive two broadcast signals having different standards, ISDB-T and ISDB-Tmm, the television tuner needs to include a receiving circuit capable of receiving signals corresponding to the respective standards. Since the configuration of the receiving circuit is different between ISDB-T and ISDB-Tmm, it is necessary to switch the receiving circuit to be used according to the frequency band of the received signal. As a television tuner that can receive broadcasts of different frequency bands, for example, by switching the connection destination using a switch means, a UHF band television signal and a VHF band television signal are sent to a corresponding receiving circuit. An apparatus configured to input data is known (for example, see Patent Document 1).

JP 2001-359005 A

  As described above, when the receiving circuit to be connected is switched using the switch means, the output voltage of GPIO (general-purpose input / output) is used to control the switch, and the signal path is switched by controlling the GPIO output voltage. . However, if the GPIO output terminal is assigned for switch control, there arises a problem that the use of the GPIO output terminal for other purposes is limited. In addition, when the GPIO terminal is used for such an application, the wiring from the antenna to the receiving circuit becomes complicated, and the antenna may be affected by noise. In addition, there is a possibility that the receiving circuit and the like are adversely affected by radiation of electromagnetic waves from the antenna or the like.

  The present invention has been made in view of such a point, and an object thereof is to provide a television tuner capable of receiving television broadcast signals in a plurality of frequency bands without assigning GPIO output terminals for switch control. .

  The television tuner of the present invention includes a tunable antenna that can be tuned to a broadcast signal in a first frequency band and a broadcast signal in a second frequency band that is separated from the first frequency band, and the first frequency band. Receiving the broadcast signal of the second frequency band and the broadcast signal of the second frequency band, and the broadcast signal of the first frequency band output from the tunable antenna tuned to the first frequency band. A first path leading to the receiving circuit; a second path guiding a broadcast signal of the second frequency band output from the tunable antenna tuned to the second frequency band to the receiving circuit; and the tunable If the tuning control voltage supplied to the antenna is a tuning voltage in the first frequency band, the first path is connected to the receiving circuit and the second path is cut off, A switching circuit for connecting the second path to the receiving circuit and blocking the first path if the tuning control voltage is a tuning voltage in the second frequency band. To do.

  According to this configuration, since the switch circuit is controlled using the tuning control voltage supplied to the tunable antenna when the resonance frequency of the antenna is controlled, the switch circuit is controlled using a control means such as GPIO. There is no need to do. For this reason, GPIO can be used for other purposes. In addition, since it is possible to prevent the wiring routing related to the tunable antenna and the like from being complicated, the possibility that the tunable antenna is affected by noise is reduced, and the reception circuit and the like may be adversely affected by radiation of electromagnetic waves from the antenna element and the like. Can be reduced. Thus, the above-described configuration provides a television tuner having a new configuration capable of receiving broadcasts of different frequency bands.

  In the television tuner of the present invention, the first path has a first switching element, the second path has a second switching element, and the receiving circuit of the first and second switching elements The same constant voltage may be applied to the side end portions, the tunable antenna side end portions of the first and second switching elements may be connected in common, and the tuning control voltage may be applied.

  In the television tuner of the present invention, the first and second switching elements may be constituted by diodes.

  In the television tuner of the present invention, the first frequency band is a band used for terrestrial digital television broadcasting, and the second frequency band is a band used for multimedia broadcasting for portable terminals. Also good.

  The television tuner of the present invention may be built in a portable device.

  According to the present invention, there is provided a television tuner capable of receiving television broadcast signals in a plurality of frequency bands without assigning GPIO output terminals for switch control.

It is a circuit diagram which shows the structural example of the television tuner which concerns on this Embodiment. It is a schematic diagram which shows operation | movement of the switch part of the television tuner which concerns on this Embodiment.

  Hereinafter, the configuration of a television tuner according to an embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a circuit diagram showing a configuration example of a television tuner according to an embodiment of the present invention. The television tuner 1 according to the present embodiment includes a tunable antenna including an antenna element 2 and a matching unit 3, a switch unit 4 that switches an output destination of a high-frequency reception signal output from the tunable antenna, and a switch unit 4. A filter unit 5 that passes only a reception signal in a desired frequency band among high-frequency reception signals supplied through the reception unit, and a reception unit 6 that decodes the reception signal from the filter unit 5 to generate a video signal. The television tuner 1 shown in FIG. 1 is mounted on a portable terminal such as a cellular phone, for example, and performs terrestrial digital television broadcasting using the ISDB-T standard and multimedia broadcasting for portable terminals using the ISDB-Tmm standard. Enable viewing.

The antenna element 2 is made of a radiating conductor composed of a dielectric pattern, for example, and is configured so that the tuning frequency can be switched over a wide band by the matching unit 3. The feeding line of the matching unit 3 is connected to the feeding unit of the antenna element 2. The matching unit 3 includes a variable capacitance element 31, inductance elements 32 to 34, a resistance element 35, and a capacitance element 36, and is configured to be able to control the tuning frequency of the antenna element 2. The variable capacitance element 31 is, for example, a variable capacitance diode (also referred to as a varactor diode or a varicap diode), and is connected in series between the antenna element 2 and the switch unit 4. The variable capacitance diode has a characteristic that the capacitance value decreases as the applied reverse voltage increases. Therefore, the tuning frequency of the antenna element 2 can be controlled by the antenna control voltage V ₁ applied to the variable capacitance element 31 via the resistance element 35.

  The inductance elements 32 to 34 are connected to the variable capacitance element 31 so that impedance matching between the antenna element 2 and the power feeding side circuit can be achieved. Specifically, an inductance element 32 is connected in parallel with the variable capacitance element 31, an inductance element 33 is connected in series with the variable capacitance element 31, and an inductance element 34 is provided between the inductance element 33 and the ground. Yes. The inductance element 33 is connected to the switch unit 4 via the capacitive element 36.

In the matching unit 3 having such a configuration, when the antenna control voltage V ₁ applied to the variable capacitance element 31 via the resistance element 35 or the like increases, the capacitance value of the variable capacitance element 31 decreases and the tuning frequency of the antenna element 2 is increased. Becomes higher. On the other hand, when the antenna control voltages V ₁ becomes smaller, the capacitance value is increased and the tuning frequency of the antenna element 2 of the variable capacitor 31 is lowered. For this reason, when receiving a high-band broadcast signal such as terrestrial digital television broadcasting (470 MHz to 710 MHz (770 MHz)), the antenna control voltage V ₁ becomes high, and multimedia broadcasting for portable terminals (207.5 MHz to when receiving a low-band broadcast signal, such as 222 MHz), the antenna control voltages _{V 1} becomes lower. That is, when receiving a broadcast signal of terrestrial digital television broadcasting (470 MHz to 710 MHz (770 MHz)) that is the first frequency band, the voltage range of the antenna control voltage V ₁ supplied to the antenna element 2, mobile terminal for multimedia broadcast as the frequency band of the antenna control voltage voltage range of _{V 1} supplied to the antenna element 2 when receiving the transmission signal towards (207.5MHz~222MHz) are spaced without overlapping is doing.

The switch unit 4 includes diodes 41 and 42 that function as switching elements and resistor elements 43 to 45, and is configured to be able to switch the output destination according to the frequency band of the high-frequency reception signal. Specifically, the anode terminal of the diode 41 and the cathode terminal of the diode 42 are commonly connected, and the common connection point is connected to the output terminal of the matching unit 3 (hereinafter, the connection point is referred to as a node A). . The antenna control voltage V ₁ is applied to the node A via the resistance element 43. A resistance element 44 is connected to the cathode terminal of the diode 41 (hereinafter, the connection point is referred to as a node B), and a reference voltage V _2, which is a constant voltage, is supplied to the node B via the resistance element 44. From the DC terminal. A resistance element 45 is connected to the anode terminal of the diode 42 (hereinafter, the connection point is referred to as a node C), and the reference voltage V ₂ is supplied from the DC terminal of the receiving unit 6 to the node C via the resistance element 45. Given.

The diode 41 is connected so that the node A and the node B are electrically connected when the node A has a higher voltage than the node B. The diode 42 is connected so that the node A and the node C are conductive when the node C has a higher voltage than the node A. Therefore, by selecting an appropriate reference voltage V ₂ to the antenna control voltages V _1, in accordance with the magnitude relationship between the antenna control voltages V ₁ and the reference voltage V _2, between the node A and the node B, Alternatively, either one of the node A and the node C becomes conductive. Specifically, the reference voltage V ₂ is lower than the antenna control voltages V ₁ supplied to the antenna element 2 at the time of the broadcast signal reception of digital terrestrial television broadcasting, and antenna during the broadcast signal reception of the mobile terminal for multimedia broadcast It is set higher than the antenna control voltage V ₁ supplied to the element 2.

  The filter unit 5 has a frequency characteristic filter 51 adapted to extract a broadcast signal of terrestrial digital television broadcasting, and a frequency characteristic filter 52 adapted to extract a broadcast signal of multimedia broadcast for portable terminals. Are provided in parallel. A path from the node A to the receiving unit 6 via the diode 41 and the filter 51 constitutes a first path. A path from the node A to the receiving unit 6 via the diode 42 and the filter 52 forms a second path.

  The receiving unit 6 includes a first receiving circuit 61 for terrestrial digital television broadcasting and a second receiving circuit 62 for multimedia broadcasting for portable terminals. Each of the first receiving circuit 61 and the second receiving circuit 62 includes a low noise amplifier, a mixer, a bandpass filter, and the like, and can decode a received signal having a predetermined frequency.

Since the above-described television tuner 1 controls the switching operation of the switch unit 4 using the antenna control voltage V ₁ supplied to the matching unit 3 in order to set the tuning frequency of the antenna element 2, such as GPIO There is no need to control the switch unit 4 using the control terminal. For this reason, the GPIO terminal can be used for other purposes. Further, since the wiring of the antenna element 2 and the like can be prevented from becoming complicated, the possibility that the antenna element 2 is affected by noise is reduced, and the reception unit 6 and the like are adversely affected by radiation of electromagnetic waves from the antenna element 2 and the like. Fear can be reduced.

  Hereinafter, the operation of the switch unit 4 in the above-described television tuner 1 will be described with reference to FIG. In FIG. 2, some components such as the matching unit 3 are omitted.

If the television tuner 1 receives a broadcast signal of terrestrial digital television broadcasting (high frequency band), antenna control voltages V ₁ is becomes 2V to 3V, receiving broadcast signals broadcast multimedia for mobile devices (low frequency band) If it, antenna control voltages _{V 1} is assumed to be a 0V～0.5V. Further, as the reference voltage V _2, it shall apply the voltage of 1.2V to be used in the mobile terminal.

When receiving a broadcast signal of terrestrial digital television broadcasting, so that the tuning frequency of the antenna element 2 matches the frequency band of terrestrial digital television broadcasting desired, antenna control voltages V ₁ is controlled. For example, it is assumed that the antenna control voltage V ₁ at the time of receiving a broadcast signal of terrestrial digital television broadcasting is controlled to ₂ V to ₃ V, and a reference voltage V _{2 of} 1.2 V is applied to the node C. In this case, 2V to 3V is applied to the node A of the switch unit 4, and 1.2V is applied to the node B and the node C. As a result, since the node A voltage (V ₁ )> the node B voltage (V ₂ ), the diode 41 is turned on, and the node A and the node B become conductive as indicated by the solid line arrow L1 in FIG. The reception signal received by the antenna element 2 is input to the first reception circuit 61 through the filter 51. On the other hand, since the node A voltage (V ₁ )> the node C voltage (V ₂ ), the diode 42 is turned off and the node A and the node C are not conducted.

When receiving multimedia broadcast for mobile devices, such that the tuning frequency of the antenna element 2 matches the frequency band of the desired mobile terminal for multimedia broadcast antenna control voltages V ₁ is controlled. In this case, the antenna control voltages _{V 1} shall be controlled to 0V～0.5V. Therefore, the antenna control voltage V ₁ of 0V to 0.5V is applied to the node A of the switch unit 4, and the reference voltage V _{2 of} 1.2V is applied to the nodes B and C. Then, since node A voltage (V ₁ ) <node C voltage (V ₂ ), diode 42 is turned on and conduction between node A and node C is established as indicated by broken line arrow L2 in FIG. The high frequency received signal received by the antenna element 2 is input to the second receiving circuit 62 via the filter 52. On the other hand, since the node A voltage (V ₁ ) <the node B voltage (V ₂ ), the diode 41 is turned off and the node A and the node B are not conducted.

As described above, switching operation in the switch section 4 is to utilize the difference between the antenna control voltages V ₁ at the time of low-band broadcast and reception antenna control voltages V ₁ at the time of high-band broadcast reception. Thus, between the lower limit value of the antenna control voltages V ₁ at the time of the high band broadcast reception (e.g. 2V), and the upper limit value of the antenna control voltages V ₁ at the time of low-band broadcast reception (e.g. 0.5V), to some extent The difference is necessary. In other words, when receiving two types of television signals, high-band broadcast reception and low-band broadcast reception, the high-band broadcast and the low-band broadcast need to be separated from each other. The reference voltage V ₂ should be a value between the lower limit value of the antenna control voltages V ₁ at the time of high-band broadcast reception, the upper limit value of the antenna control voltages V ₁ at the time of low-band broadcast reception.

As described above, the switch unit 4 in the television tuner 1 can switch the output destination of the high-frequency reception signal according to the magnitude relationship between the antenna control voltage V ₁ and the reference voltage V ₂ . In this case, since it is not necessary to control the switch unit 4 using a control terminal such as a GPIO terminal, the GPIO terminal can be used for other purposes. Further, since the wiring of the antenna element 2 and the like can be prevented from becoming complicated, the possibility that the antenna element 2 is affected by noise is reduced, and the reception unit 6 and the like are adversely affected by radiation of electromagnetic waves from the antenna element 2 and the like. Fear can be reduced.

In addition, this invention is not limited to description of the said embodiment, It can change suitably in the aspect in which the effect is exhibited, and can be implemented. For example, the characteristics of a variable capacitance element, an inductance element, a resistance element, a capacitance element, a diode, and the like constituting the television tuner can be set as appropriate within a range in which the television tuner operates. Further, the voltage values of the antenna control voltage and the reference voltage are not limited to those described in the above embodiment. As the reference voltage, V _IO (I / O terminal voltage) or the like may be used according to the range of the antenna control voltage, or various voltages may be divided and used. Further, the reference voltage is not limited to be supplied from the receiving unit. For example, the reference voltage may be given from a host device including a television tuner.

  Moreover, the frequency band of the broadcast received by the television tuner is not limited to 207.5 MHz to 222 MHz or 470 MHz to 710 MH (770 MHz). When receiving broadcasts in other frequency bands, the configuration of the television tuner may be changed as appropriate according to the target frequency band.

  The television tuner of the present invention is useful, for example, for receiving digital television broadcasts in a mobile phone.

DESCRIPTION OF SYMBOLS 1 Television tuner 2 Antenna element 3 Matching part 4 Switch part 5 Filter part 6 Receiving part 31 Variable capacity element 32-34 Inductance element 35, 43-45 Resistance element 36 Capacitance element 41, 42 Diode 51, 52 Filter 61 1st reception Circuit 62 Second receiving circuit

Claims (5)

A tunable antenna tunable to a broadcast signal in a first frequency band and a broadcast signal in a second frequency band spaced from the first frequency band;
A receiving circuit for receiving the broadcast signal of the first frequency band and the broadcast signal of the second frequency band, respectively;
A first path for guiding the broadcast signal of the first frequency band output from the tunable antenna tuned to the first frequency band to the receiving circuit;
A second path for guiding a second frequency band broadcast signal output from the tunable antenna tuned to the second frequency band to the receiving circuit;
If the tuning control voltage supplied to the tunable antenna is a tuning voltage in the first frequency band, the first path is connected to the receiving circuit and the second path is blocked, A switch circuit that connects the second path to the receiving circuit and cuts off the first path if the control voltage is a tuning voltage in the second frequency band;
A television tuner characterized by comprising:   The first path has a first switching element, the second path has a second switching element, and the receiving circuit side ends of the first and second switching elements have the same constant voltage. 2. The television tuner according to claim 1, wherein the tunable antenna side ends of the first and second switching elements are connected in common and the tuning control voltage is applied.   The television tuner according to claim 1 or 2, wherein the first and second switching elements are formed of diodes. The first frequency band is a band used for terrestrial digital television broadcasting,
The television tuner according to any one of claims 1 to 3, wherein the second frequency band is a band used for multimedia broadcasting for portable terminals.   The television tuner according to claim 1, wherein the television tuner is built in a portable device.

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