High frequency module and receiver

There are provided a high frequency module and a receiver capable of exhausting an electric field and a magnetic field to the outside of a shield, more closely arranging electronic components inside the shield, and being downsized. The high frequency module has integrated circuits (IC) 112, 113 each incorporating an oscillator including an inductor, and a shield case 114 as a shield for covering the ICs 112, 113, and the shield case 114 as a shield is formed with openings 116A, 116B having a size equal to or more than half the shape size of the ICs 112, 113 in areas opposed to the arrangement positions of the ICs 112, 113.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a national stage of International Application No. PCT/JP2010/067353 filed on Oct. 4, 2010 and claims priority to Japanese Patent Application No. 2009-242756 filed on Oct. 21, 2009, the disclosure of which is incorporated herein by reference.

BACKGROUND

The present invention relates to a high frequency module and a receiver applicable to a television tuner and the like.

In recent years, a television (TV) tuner as exemplary high frequency module has been incorporated not only in a TV receiver but also in an IT device such as personal computer (PC).

The receiver is configured as a so-called double-tuner receiver mounting a terrestrial tuner and a satellite tuner for enabling terrestrial television broadcast and satellite television broadcast to be received.

FIG. 1is a block diagram showing an exemplary structure of a typical double-tuner broadcasting receiver applied to an IT device.

A receiver1inFIG. 1has a satellite tuner2, a terrestrial tuner3, an input terminal4, a splitter5, a PCI-Express bridge6, a power supply7, a memory8and a card edge connector9.

FIG. 1shows an exemplary application in a PC using a computer interface called PCI-Express.

A circuit in the structure is standardized in its height to be incorporated into a predetermined slot, and the height needs to be within 3.75 mm.

In the receiver1, a high frequency signal input from the input terminal4is split via the splitter5and then is supplied to the two tuners2and3and decoded to output data.

The data is output to a digital data PCI-Express interface via the PCI-Express bridge6.

At this time, the power supply7supplies a necessary voltage and current and the memory8operates to hold necessary storage data.

The double-tuner receiver is required to be downsized and simplified in its mounting design. In order to address the requirements, a receiver in which two tuners are arranged in one double-tuner module is put into practical use.

FIG. 2is a block diagram showing an exemplary structure of a broadcasting receiver to which a double-tuner module is applied.

The functional parts denoted with the same numbers asFIG. 1operate in the same way asFIG. 1.

FIG. 3is a diagram showing a schematic structure of a double-tuner module arranged on a PCI-Express board.

There is exemplified that the double-tuner module10is designed on a board11to have a height of 2.3 mm.

In this way, a satellite tuner12and a terrestrial tuner13are mounted as integrated circuits (IC) on the board11and are covered with a shield case14so that a thin module is configured.

As described above, a more integrated IC is suitable for a semiconductor used for realizing the thin tuner, and the internal satellite tuner12and the internal terrestrial tuner13inFIG. 3similarly each incorporate a local oscillator and its inductor for enhancing the degree of integration.

FIG. 4is a diagram for explaining an exemplary inductor incorporated in an IC.

In a semiconductor operating in a high frequency band, a voltage controlled oscillator (VCO) typically implemented by an external circuit is an on-chip type VCO21laid on an IC chip20inFIG. 4. An inductor22essential for the VCO21is realized by an aluminum wiring in a spiral shape having a concentric shape.

The present example is an exemplary IC in which the inductor used for the local oscillator (VCO21in the drawing) is configured in pattern layout of the IC in the explanatory diagram of a process called QUBIC4 by NXP Semiconductors.

Typically, the inductor incorporated in the IC is arranged on a plane and thus has a spiral structure in which a concentric circle is spirally rounded as shown inFIG. 4.

Thus, an electric field and a magnetic field induced from the inductor are radiated in the vertically direction on the sheet during the IC operation.

Thus, when multiple ICs each incorporating the local oscillator circuit and the inductor are used, an effect of an electric field occurring around the ICs needs to be considered.

FIG. 5AandFIG. 5Bare diagrams showing a concept of an electric field radiated by an IC incorporating an inductor therein.

FIG. 5Ashows an example in which a radio wave31is radiated from an IC30mounted on the circuit board11.

In this case, the electric field intensity is circular near the IC30but is parallel to the radiation surface with a distance from the IC30as radiation element.

FIG. 5Bshows how the IC30is actually mounted on a tuner module.

That is, a copper foil surface33is covered with the shield case14in the lateral direction and in the top surface direction at the bottom of the IC30mounted on the circuit board11. In this case, since the radiated radio wave31is reflected near the shield case14and the copper foil surface33, the circular electric field is propagated via a path32while being reflected.

The shield case14is made of a metal typically called nickel silver as alloy of copper, nickel and zinc which is a thin material and is excellent in solderability, but any material excellent in conductivity is typically nonproblematic, and a low-cost tin material or its similar materials may be used when a limitation on shape is not severe.

FIG. 6AandFIG. 6Bare diagrams showing a concept of a magnetic field radiated by the IC incorporating the inductor therein.

InFIG. 6AandFIG. 6B, the same components as those inFIG. 5are denoted with the same numerals.

InFIG. 6A, there is formed a loop in which a magnetic field40is induced in the upward direction from the IC30and returns to the bottom surface.

Similarly, as shown inFIG. 6B, the magnetic field hit on the shield case14and the conductor surface of the copper foil surface33on the surface of the circuit board11generates eddy currents41. Then, the eddy currents are propagated inside the conductor and diffused therein.

FIG. 7AandFIG. 7Bare diagrams equivalently showing propagation of a high frequency signal due to the electric field and the magnetic field inFIG. 5andFIG. 6.

InFIG. 7A, when the shield case14is present near the top surface of the IC30, the electric field and the magnetic field replace the propagation of a signal due to reflection or current induction via the case with a stray capacitance50.

FIG. 7Bis an explanatory diagram in which the stray capacitance is applied to the double-tuner module inFIG. 3, and shows how the satellite tuner12and the terrestrial tuner13are connected with each other via the stray capacitance50.

It can be easily understood that the inductor incorporated in the IC30is also an element for generating an electromagnetic field when a current is flowed similarly to typical components, and conversely is an element for inducing a current in the electromagnetic field.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

A progress in IC operation frequency needs to be considered as a cause of easy radiation of a high frequency signal as described above.

As shown inFIG. 4, it is typical that an inductor suitable for a circuit operation is used in an IC incorporating a VCO, but it is typical that only a space of several-millimeter angle is given because of a limitation on the IC size.

The inductance value accomplished in this case is only about 10 nH.

For example, when parallel resonators are configured and a resonant frequency is calculated under the condition, f=½π√LC and C=1/(2πf)2L are obtained. For example, in the case of f=200 MHz, C=63 pF is required.

However, the capacitance of 63 pF to be created in the IC is so large and accordingly a chip size and cost increase in order to secure an area for opposed electrode surfaces configuring the capacitor.

On the other hand, in the semiconductor process which is faster and finer in recent years the operation frequency is on gigahertz band, and the inductor can operate at an area having several times higher than the frequency of the satellite tuner and the terrestrial tuner.

As a result of the technical progress in which the components in the semiconductor and the process operation frequency are balanced, mainly the VCO oscillating at a frequency several times higher than the reception frequency is used to divide the frequency for frequency conversion.

In the satellite tuner12, the local frequency is around 2 to 4 GHz, and thus its wavelength is around 70 to 140 mm.

When the double tuners are to be realized in one module, an interval between the tuner ICs is easily accommodated within a size of λ/4.

A distance of λ/4 causes resonance which is efficient in receiving a radio wave, and particularly causes a situation where a radio wave is easily propagated.

FIG. 8is a diagram showing an example in which an interference occurs between the tuners.

The example inFIG. 8shows that the VCO oscillation of one tuner is at a local frequency.

The side bands SB1and SB2due to an electromagnetic field spurious generated by the other tuner are produced at both sides of the local frequency near the IF where the ½ local and the RE signal are frequency-converted. Thereby, the frequency conversion is performed at both sides of the IF.

In this way, an interference between the tuners occurs at a high frequency in gigahertz band, and thus the side bands are frequency-converted together with the originally necessary RF signal and appear in the IF band.

The frequency conversion is performed in multiple ways, for example, the interference between the VCO circuits or the electromagnetic field spurious overlapped on other circuit is frequency-converted together in a mixer unit for performing frequency conversion.

As described above, the IC having the RF circuit, including oscillator such as VCO, is covered with a thin metal casing, an electromagnetic wave is propagated to the surroundings with a smaller casing, and thus a spurious noise easily occurs in the reception band.

Patent Literature 1 describes therein an electronic device which is configured such that the shield case is deformed to efficiently cause noises occurring on the circuit board to escape, thereby reducing an effect on adjacent circuits.

The electronic device is mainly directed for drawing a metal part of the shield case and bringing it close to the IC having a frequency conversion circuit inside the tuner, and employs the shield case as a ground conductor for absorbing radio waves issued from the IC.

A slit for radiating a heat is formed in the drawing unit.

The electronic device has a function of absorbing electromagnetic waves into the shield case and not leaking them, but is difficult to prevent an interference between the tuners due to an effect of the electric field and the magnetic field.

It is an object of the present invention to provide a high frequency module and a receiver capable of exhausting an electric field and a magnetic field to the outside of a shield, more closely arranging electronic components inside the shield, and thereby being downsized.

Solution to Problem

A high frequency module according to a first aspect of the present invention has an integrated circuit incorporating an oscillator therein, and a shield for covering the integrated circuit, wherein the shield is formed with an opening having a size equal to or more than half the shape size of the integrated circuit in an area opposed to the arrangement position of the integrated circuit.

A receiver according to a second aspect of the present invention comprises an input terminal to which a satellite broadcast signal or a terrestrial broadcast signal is input, a satellite broadcast receiving circuit including a satellite tuner having a function of frequency-converting the satellite broadcast signal, a terrestrial broadcast receiving circuit including a terrestrial tuner having a function of frequency-converting the terrestrial broadcast signal, and a branching circuit for putting the satellite broadcast signal input from the input terminal into the satellite broadcast receiving circuit and putting the terrestrial broadcast signal into the terrestrial broadcast receiving circuit, wherein the satellite tuner and the terrestrial tuner are formed as a satellite tuner integrated circuit and a terrestrial tuner integrated circuit each incorporating an oscillator, respectively, and include a shield for covering at least the satellite tuner integrated circuit and the terrestrial tuner integrated circuit, and the shield is formed with an opening having a size equal to or more than half the shape size of the integrated circuit in an area opposed to the arrangement position of at least one integrated circuit among the satellite tuner integrated circuit and the terrestrial tuner integrated circuit.

Advantageous Effects of Invention

According to the present invention, it is possible to exhaust an electric field and a magnetic field to the outside of a shield, to more closely arrange electronic components inside the shield and thereby to downsize the module.

DESCRIPTION OF EMBODIMENTS

Embodiments according to the present invention will be described below with reference to the drawings.

The explanation will be made in the following order.1. First embodiment2. Second embodiment

1. First Embodiment

FIG. 9is a diagram showing an exemplary structure of a broadcast signal receiver employing a high frequency module according to a first embodiment of the present invention.

FIG. 10is a diagram showing a schematic structure of essential parts of a double-tuner module employed as an exemplary high frequency module according to the first embodiment.

FIG. 11is a diagram showing an exemplary specific structure of the double-tuner module employed as an exemplary high frequency module according to the present embodiment.

A receiver100has a double-tuner module110, an input terminal120, a PCI-Express bridge130, a power supply140, a memory150, and a card edge connector160.

The receiver100ofFIG. 9is an exemplary application inside a PC using a computer interface called PCI-Express.

In the present embodiment, the double-tuner module110as an exemplary high frequency module is configured to receive satellite TV broadcast and terrestrial TV broadcast.

There is exemplified that the double-tuner module110is designed to have a height of 2.3 mm on a tuner board111as shown inFIG. 10.

The double-tuner module110configured as a thin module is configured such that a satellite tuner112and a terrestrial tuner113are mounted as ICs on the tuner board111to be covered with a shield case114as a shield.

In this way, more integrated ICs are suitable also in the semiconductor used for realizing a thin tuner.

The satellite tuner112and the terrestrial tuner113according to the present embodiment each incorporate a local oscillator and its inductor therein in order to enhance the integration as shown inFIG. 4, for example.

Numeral115inFIG. 10indicates a copper foil surface as ground surface.

The double-tuner module110is such that openings116A and116B having a size equal to or more than half the IC shape size are formed on the shield case114positioned on the top of the satellite tuner IC112and the terrestrial tuner IC113formed of the ICs as shown inFIG. 10.

The openings116A and116B are formed to efficiently exhaust an electric field an a magnetic field occurring in the shield case114to the outside.

As is clear fromFIG. 10, the shield case114having the openings formed on the top of the satellite tuner IC112and the terrestrial tuner IC113is used to prevent a stray capacitance shown inFIG. 7from occurring.

In the thus-configured double-tuner module110, even when multiple tuner ICs are mounted which are not capable of securing a sufficient distance as compared with the wavelength of the oscillation frequency of a VCO, a mutual interference between the high frequency signals can be avoided.

The size, shape, function and the like of the openings116in the high frequency module (the double-tuner module in the present embodiment) will be described in detail.

The shield case114according to the first embodiment is made of a metal typically called silver nickel as alloy of copper, nickel and zinc which is a thin material and is excellent in solderability.

Any material excellent in conductivity is typically nonproblematic for the shield ease114, and thus a low-cost tin material or its similar materials may be used when a limitation on shape is not severe.

The inductor used as an IC-incorporated oscillator is configured to have a concentric wiring.

The inductor used as the IC-incorporated oscillator is configured to have multiple concentric wirings.

For example, a spiral inductor may be formed for a mask pattern inside the IC.

The IC may be configured such that the concentric inductor is arranged for a wiring pattern, an electronic component or a wiring.

[Description of Functions of Double-tuner Module]

A circuit configuration and functions of the double-tuner module110will be described in connection withFIG. 11.

The double-tuner module200inFIG. 11has an input terminal201, a branching circuit202, a high pass filter (HPF)203, a low noise amplifier (LNA)204, a satellite tuner205and a satellite demodulator206.

The double-tuner module200has a band pass filter (BPF)207, an attenuator circuit (ATT)208, a LAN209, a terrestrial tuner210, and a terrestrial demodulator211.

The double-tuner module200has an output matrix unit212, switches213,214, and transport stream (TS) output ports215,216.

The double-tuner module200has an inductor217and a low noise blockdown converter (LNB) terminal218.

The double-tuner module200has a satellite tuner VCCA1terminal219and a terrestrial tuner VCCA2terminal220as power supply terminals.

In the double-tuner module200, a satellite broadcast receiving circuit230is formed of the HPF203, the LNA204, the satellite tuner205and the satellite demodulator20.

A terrestrial broadcast receiving circuit240is formed of the BPF207, the attenuator circuit208, the LNA209, the terrestrial tuner210and the terrestrial demodulator211.

In the double-tuner module200, a high frequency signal applied to the input terminal201is divided into a satellite broadcast receiving side and a terrestrial broadcast receiving side by the branching circuit202.

In the satellite broadcast receiving circuit230, a satellite broadcast signal is amplified by the LNA204via the HPF203and is input into the satellite tuner205to be frequency-converted. Thereafter, the satellite broadcast signal is converted to TS data in the satellite demodulator206and is sent to the output matrix unit212.

On the other hand, in the terrestrial broadcast receiving circuit240, a terrestrial broadcast signal is branched in the branching circuit202to be limited in its band in the BPF207, is adjusted to a proper signal level in the attenuator circuit208, and then is amplified in the LNA209to be input into the terrestrial tuner210.

The terrestrial broadcast signal is frequency-converted in the terrestrial tuner210and then is converted to TS data in the terrestrial demodulator211similar to the satellite demodulation to be sent to the output matrix unit212.

The output matrix unit212has the switches213and214, and can select and output TS needed for the TS output ports215and216.

The inductor217serves to shield a DC supply and a high frequency signal to the LNB, is connected to a satellite line between the terminal218and the branching circuit (splitter)202, and galvanically passes through the branching circuit202to supply a DC voltage from the input terminal201to the outside.

The terminal223is an input terminal of the I2C bus for controlling the satellite demodulator206and the terrestrial demodulator211, and is configured to control the satellite tuner205and the terrestrial tuner210via the respective demodulators.

The entire structure of the broadcast signal receiver100according to the present embodiment has been described above about the double-tuner module as exemplary high frequency module.

The properties of the high frequency module having an opening according to the present embodiment will be described below.

[Description of Principle of High Frequency Module Having Opening]

FIG. 12AandFIG. 12Bare diagrams for explaining a principle of the high frequency module having an opening according to the first embodiment.

Like reference numerals are denoted to the same components as those in the double-tuner module for easy understanding.

FIG. 12Ashows radiation of radio waves due to the high frequency module according to the present embodiment.

The opening116is formed at a predetermined position and a predetermined aperture such that the radio wave301is radiated to the outside from the opening116on the shield case114having the opening according to the present embodiment, and thus the radio wave301does not reflect in the shield case114and is not propagated in the lateral direction.

InFIG. 12B, the opening116is formed at the predetermined position and the predetermined aperture such that the shield case114having the opening116does not generate an eddy current for the magnetic field400.

The magnetic field400is diffused to the outside of the module via the opening116, thereby preventing the eddy current propagating through the shield case114from occurring.

The double-tuner module110using the shield case ofFIG. 10is formed based on the above principle.

As stated above, as is clear fromFIG. 10, the shield case having the openings provided on the top of the satellite tuner IC112and the terrestrial tuner IC113is used to prevent a stray capacitance shown inFIG. 7from occurring.

In the thus-configured tuner module, even when multiple tuner ICs are mounted which are not capable of securing a sufficient distance as compared with the wavelength of the oscillation frequency of the VCO, a mutual interference between the high frequency signals can be avoided.

FIG. 13is a diagram for explaining an exemplary specific structure of the openings formed on the shield case114according to the present embodiment.

The top diagram inFIG. 13shows an example in which the square holes on top of the mounted ICs are formed as the openings116C and116D, where the center position is the same as that of each IC.

The aperture has a notable effect with a side equal to or more than half of each side of the IC chip, and the aperture in this case is desirable at (½)2=¼ or more and is 25% or more of the IC size.

In the present example, the square hole size is 4.7 mm×4.7 mm and the tuner IC size is 4.3 mm×4.3 mm.

The shield case114has a size of 23 mm×23 mm.

The bottom diagram inFIG. 13shows that the shape of the openings116E and116F on the shield case114according to the present embodiment is circular.

Also in this case, when the aperture is 25% or more of the IC size, satisfactory effects can be expected.

In the present example, the diameter of the circular openings116E and116F is 6 mm.

FIG. 14AandFIG. 14Bare diagrams for explaining other exemplary specific structure of the openings formed on the shield case114according to the present embodiment.

InFIG. 14A, the square holes corresponding to those in the exemplary structure in the top diagram inFIG. 13are denoted with numerals116C and116D, and in the present example, an opening116G is formed as an oval hole containing both the square holes.

The stray capacitance can be avoided from occurring also in the present structure, and thus a mutual interference between the high frequency signals can be prevented.

Similarly, in the example ofFIG. 14B, an oval opening116H contains the square holes116C and116D, andFIG. 14Cshows an example in which multiple holes are present under the condition that the same openings116I and116J do not take the same centers as the IC positions.

FIG. 14Dshows a case in which only one opening116K is present.

In the tuner module having the above structure, an actual difference in performance is expressed as a bit error rate (BER).

FIG. 15is a diagram showing an example in which an interference from the terrestrial tuner to the satellite tuner is measured.

InFIG. 15, the horizontal axis indicates a channel name and the longitudinal axis indicates a CN value.

The CN ratio in the longitudinal axis indicates a standardized Carrier/Noise ratio of an input signal necessary for so excellent a state of the BER called required CN.

InFIG. 15, the property indicated by A is when two openings are formed, the property indicated by B is when one opening is formed, and the property indicated by C is when no opening is formed.

Particularly, the effects of the holes near the BS15 channel used for the satellite broadcast in Japan are indicated.

When two openings are formed, an interference can be sufficiently prevented.

Also when only one opening is formed, a sufficient interference preventing effect is indicated as compared with the case with no hole.

That is, the effect of the required CN inFIG. 15is for the local frequency of 2636 MHz which is twice the input frequency of 1318 MHz near the BS-15 channel, and it is most effective that as many holes as the ICs to be mounted are provided.

It is clear that only one hole achieves the effect.

2. Second Embodiment

FIG. 16is a diagram showing an exemplary structure of a double-tuner module in a broadcast signal receiver according to a second embodiment of the present invention.

A double-tuner module110A according to the second embodiment is different from the double-tuner module110according to the first embodiment in that a conductive paste117is applied to form a conductive application film as a shield instead of the shield case.

That is, in the double-tuner module110A, a mold filling material118is sealed around the satellite tuner IC112and the terrestrial tuner IC113mounted on the tuner board111for protection.

The double-tuner module110A is applied with the conductive paste117at its outer periphery for sealing thereby to have the same effects as those of the shield case.

At this time, the opening116A and the opening116B are formed on the application film117A of the conductive paste117having the same operation as the shield case, thereby to exhaust the radio waves and the magnetic field line to the outside of the shield body made of the conductive paste.

The detailed operation principle is exactly the same as that of the shield case, and thus an explanation thereof will be omitted.

The ground surface115on the board111is electrically connected to the conductive paste117at its walls thereby to form the shield body.

As described above, the following effects can be obtained according to the present embodiment. The electric filed and the magnetic field can be exhausted to the outside of the shield, the electronic components inside the shield can be more closely arranged, and thereby the module can be downsized.

For example, the present embodiment is effective when the satellite tuner IC or the terrestrial tuner IC using the shield case incorporates an oscillator such as VCO using a spiral inductance.

That is, the present embodiment is effective when the electric field and the magnetic field radiated by the oscillation circuit electromagnetically combine or magnetically combine the surrounding circuits thereby to generate a spurious noise, or the ICs are mounted so closely that a deterioration in the phase noise of the oscillator cannot be ignored.

Particularly, since a group of more strongly occurring noises can be radiated to the outside of the shield due to the shield case, thereby arranging the components so closely.

Particularly when multiple tuners are configured on the same board, the same effect can be obtained as when the electric field and the magnetic field are exhausted to the outside of the shield, and the effect is conspicuous particularly when the tuners are simultaneously operated.

The present embodiment is effective also when an independent oscillator having a transmission and reception function like a transceiver is used.

Further, since only one oscillator can cause a noise in another path to the mixer circuit or the input circuit, the shield having the openings is provided and thus the effect can be expected.

Additionally, the present embodiment is effective also for a transmitter/receiver having multiple bands such as 2.4 GHz band and 5 GHz band like a wireless LAN.

The semiconductor to which the present structure is applied includes monolithic IC incorporating a spiral inductance in the IC mask pattern.

The semiconductor includes an IC having an inductance formed on a small board on which a silicon bare chip called SIP (System In Package) is mounted.

Alternatively, the semiconductor includes an IC using a spiral inductance as a typical external device.

The present embodiment is effective also for any IC, and can be applied thereto.

REFERENCE SIGNS LIST