JP2011004046A - Broadcast receiving device and portable terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broadcast receiving device and a portable terminal device, which can remove an undesired high-frequency signal possibly causing some damage of a broadcast receiving circuit without dependence on a set frequency of a communication signal.SOLUTION: A portable terminal device 1 comprises: a transmitting circuit 2; and a broadcast receiving device 3, and in the broadcast receiving device 3 of the present embodiment, a high-frequency protection circuit 7 connected between an input terminal and an output terminal of a circuit block 6, in parallel with the block 6, is provided. In the high-frequency protection circuit 7, a switching element 9 is installed for on/off controlling of connection between a first capacitor 8 for attenuating a high-frequency signal having a predetermined level or higher and a ground 10, and when a high-frequency signal of the predetermined level or higher has been inputted to the input terminal 4, a detection means 13 turns on the switching element 9.

Description

  The present invention relates to a broadcast receiving apparatus and a portable terminal, and in particular, a broadcast receiving apparatus and a portable terminal that can be suitably used for a mobile phone that can be used in both regions where broadcast signal standards are different and a broadcast receiving apparatus incorporated therein. About.

  As mobile phones have become more sophisticated in recent years, as shown in FIG. 4, not only communication signal transmitting / receiving device 102 preinstalled in mobile phone 101, but also broadcast receiving device 103 that receives terrestrial digital television broadcasts. Is increasingly being installed.

  As an example, the conventional broadcast receiving apparatus 103 includes an input terminal 117 to which an antenna 112 is connected and a broadcast reception circuit 106 connected to a subsequent stage of the input terminal 117, as shown in FIG. The broadcast receiving circuit 106 includes, for example, a packaged LNA (low noise amplifier) 105 and a tuner circuit 107. The tuner circuit 107 includes a variable amplifier 108, a mixer 109, an IF (intermediate frequency) amplifier 110, a demodulator 113, The composite circuit 114, the AGC control circuit 115, the local oscillator 116, and the like are used.

  Further, the transmission frequency band of the mobile phone 101 is often close to the reception frequency band of the broadcast receiving circuit 106. Therefore, in the conventional broadcast receiving apparatus 103, a filter circuit 104 such as a SAW filter or a low-pass filter for attenuating the transmission wave of the mobile phone 101 is connected in series between the input terminal 117 and the tuner circuit 107 of the broadcast receiving circuit 106. Was connected to.

JP 2006-80871 A

  Here, since recent mobile phones 101 are often compatible with calls made in other countries even in models produced in Japan, there is an opportunity to take mobile phones 101 sold in Japan and use them overseas. It is increasing.

  However, the conventional broadcast receiving apparatus 103 has a problem that the broadcast receiving circuit 106 is damaged when a call is made overseas. The cause of the damage is that the frequency of the overseas communication signal is set regardless of the frequency of the television broadcast in Japan, so that the broadcast receiving circuit 106 receives the high-frequency signal used for the overseas communication signal. This is due to the fact that it is difficult to take measures to prevent this, and that the maximum transmission power in Japan is 24 dBm, whereas the maximum transmission power overseas is 33 dBm, which is larger than the maximum transmission power in Japan. it seems to do.

  Therefore, the present invention has been made in view of these points, and a broadcast receiving apparatus capable of removing an unnecessary high-frequency signal that causes damage to the broadcast receiving circuit without depending on the set frequency of the communication signal, and It is an object of the present invention to provide a portable terminal.

  In order to achieve the above-described object, the broadcast receiving apparatus according to the present invention has, as a first aspect thereof, an input terminal to which a broadcast signal received from an antenna is input, and a broadcast receiving circuit connected to a subsequent stage of the input terminal. And a circuit block connected in series between the input terminal and the broadcast receiving circuit, and a high-frequency protection circuit connected in parallel between the input end and the output end of the circuit block. The protection circuit is connected in series between the output terminal of the circuit block and the ground, and has a first capacitor for attenuating a high-frequency signal of a predetermined level or more input from the input terminal, and a first capacitor When the switching element connected in series and the input terminal of the circuit block are connected in parallel and a high frequency signal of a predetermined level or higher is input to the input terminal The current or voltage to turn on the switching element is characterized by having a detecting means for supplying to the switching element.

  According to the broadcast receiving apparatus of the first aspect of the present invention, the switching element is turned on when a high-frequency signal of a predetermined level or higher is input to the input terminal, and the first capacitor is connected to the ground. Only when a high-frequency signal of a predetermined level or higher is input, the high-frequency signal can be automatically attenuated. Further, the circuit block can make the switching element perform a stable switching operation by utilizing the property of stabilizing the impedance between the input and output terminals.

  The broadcast receiving apparatus according to the second aspect of the present invention is the broadcast receiving apparatus according to the first aspect, wherein the detection means includes a detection diode connected in series between the input terminal and the switching element, and a stage subsequent to the detection diode. The switching element is a switching transistor that is turned on when a current or a voltage supplied from the detection means is input from the control terminal thereof, and is formed by using a smoothing capacitor connected in parallel. The capacitor is characterized in that it is connected between the output terminal of the circuit block and the switching element.

  According to the broadcast receiving apparatus of the second aspect of the present invention, it is possible to form suitable detection means and switching elements with a simple circuit configuration.

  The broadcast receiving apparatus according to the third aspect of the present invention is the broadcast receiving apparatus according to the first or second aspect, wherein the circuit block is a filter circuit formed by connecting a SAW filter, a low-pass filter, or a SAW filter and a low-pass filter in series. In addition, the first capacitor is characterized in that it is set to a capacitance value such that the cutoff frequency in the circuit block is lowered when the switching element is turned on.

  According to the broadcast receiving apparatus of the third aspect of the present invention, the cutoff frequency can be automatically changed according to the power level of the high-frequency signal.

  The broadcast receiving device according to a fourth aspect of the present invention is the broadcast receiving device according to any one of the first to third aspects, wherein the detection means connects the input terminal and the input end of the detection means in series. It is characterized by having a capacitor.

  According to the broadcast receiving apparatus of the fourth aspect of the present invention, the DC component of the high frequency signal can be cut.

  A broadcast receiving apparatus according to a fifth aspect of the present invention is the broadcast receiving apparatus according to any one of the first to fourth aspects, wherein the broadcast receiving circuit is a digital terrestrial broadcast receiving circuit.

  According to the broadcast receiving apparatus of the fifth aspect of the present invention, the present invention can be applied to many terrestrial digital broadcast receiving circuits mounted on portable terminals.

  In order to achieve the above-described object, the portable terminal of the present invention includes, as a first aspect thereof, the broadcast receiving apparatus according to any one of the first to fifth aspects described above and an antenna or other antenna. A high-frequency signal having a predetermined level or higher input from the input terminal is a communication signal output from the transmission circuit, and the first capacitor is a communication signal. It is characterized in that the capacitance value is set to such a low impedance that it can be handled in the same or approximated manner as the ground state with respect to the frequency band.

  According to the mobile terminal of the first aspect of the present invention, since the high-frequency signal of a predetermined level or higher is specified, the attenuation characteristic of the first capacitor can be set more effectively.

  According to the broadcast receiving apparatus and portable terminal of the present invention, the high frequency signal is automatically attenuated only when a high frequency signal of a predetermined level or more is input, and therefore depends on the set frequency of the communication signal. In addition, an unnecessary high-frequency signal that causes damage to the broadcast receiving circuit can be removed.

The block diagram which shows one Embodiment of the portable terminal of this invention Equivalent circuit diagram showing a part of the broadcast receiving apparatus of the present embodiment The graph which shows the attenuation characteristic by the broadcast receiver of this embodiment Block diagram showing an example of a conventional portable terminal Equivalent circuit diagram showing an example of a conventional broadcast receiving apparatus

  Hereinafter, a portable terminal and a broadcast receiver according to the present invention will be described with reference to an embodiment thereof.

  As shown in FIG. 1, the mobile terminal 1 of this embodiment includes a transmission circuit 2 and a broadcast receiving device 3. The transmission circuit 2 is configured to output a communication signal transmitted from the first antenna 11 suitable for transmission / reception of a communication signal. As the transmission circuit 2, a communication transmission / reception circuit conventionally used in a mobile phone or the like is selected.

  In addition, the broadcast receiving device 3 of this embodiment includes an input terminal 4, a broadcast receiving circuit 5, a circuit block 6 and a high frequency protection circuit 7.

  The input terminal 4 is a terminal connected to the second antenna 12 suitable for transmission / reception of broadcast signals. A broadcast signal received from the second antenna 12 is input from the input terminal 4.

  The broadcast receiving circuit 5 is a circuit composed of an LNA and a tuner circuit as in the prior art, and is generally packaged in an IC package. The broadcast receiving circuit 5 and the input terminal 4 are connected to the subsequent stage. The broadcast receiving circuit 5 is preferably a digital terrestrial broadcast receiving circuit.

  The circuit block 6 represents a unit of a group of circuits and is connected in series between the input terminal 4 and the broadcast receiving circuit 5. The circuit block 6 is preferably a filter circuit formed by connecting a SAW filter, a low-pass filter, or a SAW filter and a low-pass filter in series. As the circuit block 6 of this embodiment, as shown in FIG. 2, a π-type filter including one inductor 6a and two capacitors 6b and 6c connected in parallel on both sides thereof is used.

  As shown in FIG. 1, the high-frequency protection circuit 7 is connected in parallel between the input end and the output end of the circuit block 6. As shown in FIG. 2, the high-frequency protection circuit 7 includes at least a first capacitor 8, a switching element 9, and detection means 13.

  The first capacitor 8 is connected in series between the output terminal of the circuit block 6 and the ground 10, preferably between the output terminal of the circuit block 6 and the switching element 9. The first capacitor 8 is set to a capacitance value suitable for attenuating at least a high-frequency signal input from the input terminal 4 and having a predetermined level or higher.

  Here, the high-frequency signal of a predetermined level or higher is assumed to be a communication signal output from the transmission circuit 2 mounted on the portable terminal 1 or another portable terminal of the present embodiment. Further, as the capacitance value of the first capacitor 8, for example, a capacitance value that attenuates a high-frequency signal of a predetermined level or higher to about +10 dB is set. Furthermore, it is assumed that the broadcast receiving apparatus 3 of this embodiment is mounted on the mobile terminal 1 of this embodiment in which the transmission circuit 2 is mounted.

  In view of the above points, the first capacitor 8 has a capacitance that is low enough to handle the frequency band of the communication signal handled by the transmission circuit 2 of the present embodiment in the same or approximate manner as the ground state. It is preferable that the value is set. Furthermore, it is preferable that the first capacitor 8 is set to a capacitance value such that the cut-off frequency in the circuit block 6 is lowered when the switching element 9 is turned on.

  The switching element 9 is an element formed so as to be turned on in response to a predetermined current or voltage supplied from the detection means 13, and is connected in series to the first capacitor 8 (this embodiment) as shown in FIG. In FIG. 2, the first capacitor 8 and the ground 10 are connected. The switching element 9 is preferably a switching transistor that is turned on when a current or voltage supplied from the detection means 13 is input from its control terminal.

  As shown in FIG. 2, the detection means 13 is a circuit or element that supplies a predetermined current or voltage to the switching element 9 when a high-frequency signal of a predetermined level or higher is input to the input terminal 4. It is connected in parallel with the input terminal. The predetermined current or voltage is a current or voltage suitable for turning on the switching element 9.

  In the present embodiment, the detection means 13 preferably includes at least the detection diode 14 and the smoothing capacitor 15, and in addition to these, includes the second capacitor 17 and the resistor 16. The detection diode 14 is connected in series between the input terminal 4 and the switching element 9. The detection diode 14 is preferably a high-frequency rectifier diode. The smoothing capacitor 15 is connected in parallel at the output terminal of the detection diode 14. The second capacitor 17 is a capacitor that determines the operating power of the high-frequency protection circuit 7 by adjusting the degree of coupling according to the coupling capacitance value, and is connected in series between the input terminal 4 and the input terminal of the detection means 13. ing. The resistor 16 controls the current or voltage supplied from the detection means 13 to a value suitable for supplying to the switching element 9 when the current or voltage is excessive as compared with a value suitable for the switching operation of the switching element 9. The smoothing capacitor 15 and the switching element 9 are connected in series.

  Next, the operation of the mobile terminal 1 and the broadcast receiving device 3 of this embodiment will be described.

  As shown in FIG. 1, the mobile terminal 1 of this embodiment includes a transmission circuit 2 and a broadcast receiving device 3. Moreover, in the broadcast receiving apparatus 3 of this embodiment, as shown in FIG. 2, the high frequency protection circuit 7 connected in parallel between the input end and output end of the circuit block 6 is formed. In the high-frequency protection circuit 7, the first capacitor 8 that attenuates a high-frequency signal of a predetermined level or higher, the switching element 9 that controls on / off of the connection between the first capacitor 8 and the ground 10, and a predetermined Detection means 13 is provided for turning on the switching element 9 when a high-frequency signal of a level equal to or higher than that level is input to the input terminal 4. Thereby, only when a high-frequency signal of a predetermined level (for example, about +15 to +33 dBm) or more is input to the second antenna 12, the detection unit 13 turns on the switching element 9 and the first capacitor 8 is connected to the ground 10. Since it is connected, the power of the high-frequency signal is grounded via the first capacitor 8. As a result, only the high-frequency signal of a predetermined level or higher is automatically attenuated, so that the broadcast receiving circuit 5 can be protected from the high-frequency signal that causes the broadcast receiving circuit 5 to be destroyed.

  Further, the circuit block 6 stabilizes the impedance between its input / output terminals. Therefore, by connecting the high frequency protection circuit 7 to the circuit block 6 in parallel, the voltage or current supplied from the detection means 13 is stabilized, so that the switching operation of the switching element 9 can be stabilized.

  As shown in FIG. 2, the circuit block 6 for stabilizing the impedance is preferably a filter circuit formed by connecting a SAW filter, a low-pass filter, or a SAW filter and a low-pass filter in series. Further, the first capacitor 8 of the high frequency protection circuit 7 is preferably set to a capacitance value such that the cutoff frequency in the circuit block 6 is lowered when the switching element 9 is turned on. Thus, the cutoff frequency can be automatically changed according to the power level of the high frequency signal.

  For example, when the maximum input sensitivity of the broadcast receiving circuit 5 is 0 dBm and the first capacitor 8 is grounded, the cut-off frequency of the π-type filter serving as the circuit block 6 is set to a value lower than the UHF band, The capacitance value of the first capacitor 8 is set so that the UHF band broadcast signal is attenuated by about 15 dB when the capacitor 8 is grounded. As a result, as shown in FIG. 3, when a high frequency signal of a predetermined level or higher is input to the broadcast receiving device 3, the switching element 9 is turned on and the first capacitor 8 is grounded, so that the circuit block 6 It is possible to reduce the cut-off frequency of the π-type filter. As a result, the maximum input sensitivity of the broadcast receiving circuit 5 viewed from the second antenna 12 is +15 dBm, so that the maximum input sensitivity of the broadcast receiving circuit 5 can be improved.

  In the detection means 13 of the high-frequency protection circuit 7 according to the present embodiment, it is preferable that at least the detection diode 14 and the smoothing capacitor 15 are provided, and a switching transistor is used as the switching element 9. Further, the first capacitor 8 of the high frequency protection circuit 7 is preferably connected between the output terminal of the circuit block 6 and the switching element 9. Thereby, the suitable detection means 13 and the switching element 9 can be formed with a simple circuit configuration.

  As shown in FIG. 2, it is preferable that a second capacitor 17 is connected in series between the input terminal 4 and the input terminal of the detection unit 13 with respect to the detection unit 13. As a result, the second capacitor 17 becomes a coupling capacitor, so that the DC component of the high-frequency signal can be cut and the operating power of the high-frequency protection circuit 7 can be determined.

  The broadcast receiving circuit 5 of the present embodiment is preferably a terrestrial digital broadcast receiving circuit. As a result, the broadcast receiving device 3 of the present embodiment can be applied to many terrestrial digital broadcast receiving circuits mounted on the mobile terminal 1.

  Further, in the mobile terminal 1 of the present embodiment, the communication signal output from the transmission circuit 2 of the present embodiment is set as a high-frequency signal having a predetermined level or higher, and the first capacitor 8 is used for the communication signal. The capacitance value is set so that the impedance is low enough to handle the frequency band in the same or approximate manner as the ground state. When the transmission circuit 2 is mounted on the mobile terminal 1 in which the broadcast receiving device 3 is mounted as in the mobile terminal 1 of the present embodiment, a high-frequency signal having a predetermined level or higher can be specified. A large attenuation can be finely set according to the high-frequency signal. As a result, the attenuation characteristic of the first capacitor 8 can be set more effectively.

  That is, according to the broadcast receiving device 3 and the mobile terminal 1 of the present embodiment, the high frequency signal is automatically attenuated only when a high frequency signal of a predetermined level or higher is input. There is an effect that it is possible to remove an unnecessary high-frequency signal that causes damage to the broadcast receiving circuit 5 without depending on the frequency.

  In addition, this invention is not limited to embodiment mentioned above etc., A various change is possible as needed.

DESCRIPTION OF SYMBOLS 1 Mobile terminal 2 Transmission circuit 3 Broadcast receiving apparatus 4 Input terminal 5 Broadcast receiving circuit 6 Circuit block 7 High frequency protection circuit 8 First capacitor 9 Switching element 10 Ground 11 First antenna 12 Second antenna 13 Detection means 14 Detection Diode 15 Smoothing capacitor 16 Resistor 17 Second capacitor

Claims (6)

An input terminal for receiving a broadcast signal received from an antenna;
A broadcast receiving circuit connected to a subsequent stage of the input terminal;
A circuit block connected in series between the input terminal and the broadcast receiving circuit;
A high-frequency protection circuit connected in parallel between the input end and the output end of the circuit block,
The high-frequency protection circuit is
A first capacitor connected in series between the output terminal of the circuit block and the ground, and attenuating a high-frequency signal of a predetermined level or more input from the input terminal;
A switching element connected in series to the first capacitor;
A current or voltage that is connected in parallel with the input terminal of the circuit block and that turns on the switching element when a high-frequency signal of the predetermined level or higher is input to the input terminal is supplied to the switching element. A broadcast receiving apparatus comprising: a detecting unit. The detection means is formed using a detection diode connected in series between the input terminal and the switching element, and a smoothing capacitor connected in parallel at a subsequent stage of the detection diode,
The switching element is a switching transistor that is turned on by inputting a current or a voltage supplied from the detection means from its control terminal,
The broadcast receiving apparatus according to claim 1, wherein the first capacitor is connected between an output terminal of the circuit block and the switching element. The circuit block is a filter circuit formed by connecting a SAW filter or a low-pass filter or the SAW filter and the low-pass filter in series.
3. The capacitor according to claim 1, wherein the first capacitor is set to have a capacitance value such that a cutoff frequency in the circuit block is lowered when the switching element is turned on. Broadcast receiving device. The broadcast according to any one of claims 1 to 3, wherein the detection means includes a second capacitor that connects the input terminal and an input terminal of the detection means in series. Receiver device. The broadcast receiving apparatus according to claim 1, wherein the broadcast receiving circuit is a terrestrial digital broadcast receiving circuit. The broadcast receiving device according to any one of claims 1 to 5,
A transmission circuit that outputs a communication signal transmitted from the antenna or other antenna,
The high-frequency signal of the predetermined level or more input from the input terminal is a communication signal output from the transmission circuit,
The first capacitor is set to a capacitance value such that the first capacitor has a low impedance that can be handled in the same or approximate manner as a grounded state with respect to the frequency band of the communication signal. Machine.

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