Oscillation module, electronic device, and moving object

An oscillation module includes: an oscillation circuit; a multiplication circuit which is provided at a stage subsequent to the oscillation circuit and is operated by differential motion; and an output circuit which is provided at a stage subsequent to the multiplication circuit.

BACKGROUND

1. Technical Field

The present invention relates to an oscillation module, an electronic device, and a moving object.

2. Related Art

JP-A-2004-040509 discloses an oscillation circuit including: a differential amplifier for oscillation configured with an ECL line receiver; a differential amplifier for feedback buffering which is configured with an ECL line receiver and in which an output terminal is terminated due to emitter terminating resistance; a switch circuit; a voltage-controlled phase-shift circuit; a SAW resonator having a predetermined resonance frequency; and an impedance circuit, in which a positive feedback oscillation loop is formed with at least the differential amplifier for oscillation, the differential amplifier for feedback buffering, the voltage-controlled phase-shift circuit, and the SAW resonator. According to this oscillation circuit, the emitter terminating resistance of the differential amplifier for feedback buffering is changed to increase a drive level of the SAW resonator, and accordingly, the amplitude of a signal from the SAW resonator is relatively greater than that of the noise superimposed thereon. That is, since a large SN ratio is obtained, it is possible to decrease jitter caused by noise superimposed on the signal from the SAW resonator.

This oscillation circuit outputs an oscillation signal at a frequency close to a resonance frequency of the SAW resonator, but it is possible to generate a signal at a frequency which is N times the frequency described above by providing a multiplication circuit at a subsequent stage. JP-A-2007-013565, for example, discloses an oscillation circuit in which a multiplication circuit is provided at a stage subsequent to a ring oscillator. This multiplication circuit has a configuration of outputting an exclusive OR of two signals extracted from inverters in any two stages among inverters of odd stages configuring the ring oscillator, and when the multiplication circuit disclosed in JP-A-2007-013565 is provided at a stage subsequent to the oscillation circuit disclosed in JP-A-2004-040509, for example, it is possible to obtain a multiplied output while preventing an increase in circuit area.

However, noise may be superimposed on power supplied to the multiplication circuit due to an oscillation operation of the oscillation circuit, and an oscillation signal output by the multiplication circuit may be significantly degraded due to the effect of this power supply noise.

SUMMARY

An advantage of some aspects of the invention is to provide an oscillation module capable of outputting an oscillation signal having reduced degradation due to an effect of power supply noise generated due to an operation of the oscillation circuit. Another advantage of some aspects of the invention is to provide an electronic device and a moving object using the oscillation module.

APPLICATION EXAMPLE 1

An oscillation module according to this application example includes: an oscillation circuit; a multiplication circuit which is provided at a stage subsequent to the oscillation circuit and is operated by differential motion; and an output circuit which is provided at a stage subsequent to the multiplication circuit.

According to the oscillation module according to this application example, even when noise is superimposed on the power supplied to the multiplication circuit due to the operation of the oscillation circuit, since the multiplication circuit is operated by differential motion, the power supply noise superimposed on a pair of signals (oscillation signals) output by the multiplication circuit becomes common mode noise. Therefore, according to the oscillation module of the application example, it is possible to output oscillation signals in which degradation due to the effect of power supply noise generated due to the operation of the oscillation circuit is reduced.

According to the oscillation module according to this application example, since the multiplication circuit is provided at a stage subsequent to the oscillation circuit, it is possible to output oscillation signals (for example, oscillation signals at higher frequency) at a frequency different from that of the oscillation signals output by the oscillation circuit.

APPLICATION EXAMPLE 2

In the oscillation module according to the application example, the oscillation circuit may be operated by differential motion.

According to the oscillation module according to this application example, since the oscillation circuit is operated by differential motion, the power supply noise which is superimposed on one pair of signals (oscillation signals) propagating on the feedback path of the oscillation circuit as common mode noise is significantly reduced. Therefore, according to the oscillation module according to the application example, it is possible to improve frequency accuracy and S/N of the oscillation signal.

APPLICATION EXAMPLE 3

In the oscillation module according to the application example, the multiplication circuit may be an equilibrium modulation circuit.

According to the oscillation module according to this application example, since the multiplication circuit is an equilibrium modulation circuit, a signal at the same frequency as that of the signal input to the multiplication circuit is not output from the multiplication circuit in principle (only a signal obtained by the multiplication of the frequency of the signal input is output). Therefore, according to the oscillation module according to the application example, an oscillation signal at a multiplication frequency having high purity (high frequency accuracy) is obtained.

APPLICATION EXAMPLE 4

In the oscillation module according to the application example, the oscillation circuit may include a SAW filter including a first input port, a second input port, a first output port, and a second output port, and a first differential amplifier provided on a feedback path from the first output port and the second output port to the first input port and the second input port.

According to the oscillation module according to this application example, the oscillation circuit oscillates by amplifying one pair of signals output from the first output port and the second output port of the SAW filter by the differential amplifier and causing feedback of the signals to the first input port and the second input port of the SAW filter to configure a feedback path of a closed loop. The power supply noise superimposed on one pair of signals propagating on the feedback path of the oscillation circuit as common mode noise is significantly decreased by the first differential amplifier. Therefore, according to the oscillation module according to the application example, it is possible to output oscillation signals in which degradation due to the effect of the power supply noise is reduced.

APPLICATION EXAMPLE 5

In the oscillation module according to the application example, a signal propagating from the first output port to the first input port and a signal propagating from the second output port to the second input port on the feedback path may have phases opposite to each other.

According to the oscillation module according to this application example, since one pair of signals propagating on the feedback path are differential signals, the one pair of signals (differential signals) are amplified by the differential amplifier, and the power supply noise superimposed as common mode noise is significantly reduced. Therefore, according to the oscillation module according to the application example, it is possible to improve frequency accuracy and S/N of the oscillation signal.

APPLICATION EXAMPLE 6

In the oscillation module according to the application example, a member having inductance may be provided on the feedback path.

The member having inductance may be an electronic component such as a coil having inductance, or may be a bonding wire or a substrate wiring having parasitic inductance.

According to the oscillation module according to this application example, it is possible to change an oscillation frequency over a variable range according to the inductance value of the feedback path.

APPLICATION EXAMPLE 7

In the oscillation module according to the application example, the oscillation circuit may include a phase shift circuit which is provided on the feedback path and includes a first coil, a second coil, and a variable capacitance element.

According to the oscillation module according to this application example, it is possible to change the frequency of the oscillation signal output by the oscillation circuit over a variable range according to the inductance of the first coil and the inductance of the second coil, by changing a capacitance value of the variable capacitance element.

A SAW resonator has rapidly-changing frequency characteristics with respect to reactance, whereas a SAW filter has linear (slowly-changing) frequency characteristics with respect to reactance, and accordingly, according to the oscillation module according to the application example, the variable range of the frequency is easily controlled, compared to a case where the oscillation circuit is replaced with an oscillation circuit using a SAW oscillator.

APPLICATION EXAMPLE 8

In the oscillation module according to the application example, the first differential amplifier and the phase shift circuit may be a part of an integrated circuit, and the first differential amplifier and the variable capacitance element may be arranged so as to intersect a virtual straight line equidistant from the center of the first coil and the center of the second coil, in a plan view of the integrated circuit.

According to the oscillation module according to this application example, it is possible to decrease a distance between a wiring length of a signal path from the first output port to the first input port of the SAW filter and a wiring length of a signal path from the second output port to the second input port of the SAW filter. Therefore, a difference in parasitic capacitance or parasitic resistance of two signal paths is decreased and it is possible to reduce deviation of a phase difference of one pair of signals propagating or a difference in a noise level superimposed on the one pair of signals.

APPLICATION EXAMPLE 9

In the oscillation module according to the application example, currents having opposite phases may flow to the first coil and the second coil.

According to the oscillation module according to this application example, since a direction of a magnetic field generated by the first coil and a direction of a magnetic field generated by the second coil are opposite to each other and are weakened, it is possible to reduce the degradation of the oscillation signal due to the effect of the magnetic field.

APPLICATION EXAMPLE 10

In the oscillation module according to the application example, the oscillation circuit may output a differential signal, and the circuits on a signal path from the oscillation circuit to the output circuit may be operated by differential motion.

According to the oscillation module according to this application example, since the power supply noise generated by the operation of the oscillation circuit is superimposed on the differential signal input to each circuit provided at a stage subsequent to the oscillation circuit as a common mode noise, each circuit can output a differential signal having significantly reduced power supply noise by being operated by differential motion. Therefore, according to the oscillation module according to the application example, it is possible to output an oscillation signal having high frequency accuracy in which degradation due to the effect of the power supply noise generated by the operation of the oscillation circuit is reduced.

APPLICATION EXAMPLE 11

In the oscillation module according to the application example, the oscillation module may further include: a second differential amplifier which is provided on a signal path from the oscillation circuit to the multiplication circuit; and a filter circuit which is provided on a signal path from the multiplication circuit to the output circuit.

The filter circuit may be a high pass filter or a band pass filter containing a frequency (multiplication frequency) of a signal output by the multiplication circuit in a passband, for example.

According to the oscillation module according to this application example, it is possible to optimally set a frequency accuracy of an oscillation signal by suitably selecting an amplification factor of the first differential amplifier provided in the oscillation circuit and an amplification factor of the second differential amplifier provided at a stage subsequent to the oscillation circuit. According to the oscillation module according to the application example, since it is possible to reduce a signal at an unnecessary frequency component contained in the oscillation signal output by the multiplication circuit by the filter circuit, it is possible to improve frequency accuracy of the oscillation signal.

APPLICATION EXAMPLE 12

An electronic device according to this application example includes: the oscillation module according to the application example.

APPLICATION EXAMPLE 13

A moving object according to this application example includes: the oscillation module according to the application example.

According to these application examples, since an oscillation module capable of outputting an oscillation signal having reduced degradation due to an effect of power supply noise generated due to an operation of the oscillation circuit is provided, it is possible to realize an electronic device and a moving object having high reliability, for example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the preferred embodiments of the invention will be described in detail with reference to the drawings. The embodiments which will be described hereinafter do not unjustly limit the contents of the invention disclosed in the aspects. All of configurations which will be described later is not always compulsory configuration requirements of the invention.

1-1. Structure of Oscillation Module

FIG. 1is a view showing an example of a structure of an oscillation module1of the embodiment and is a perspective view of the oscillation module1.FIG. 2is a sectional view of the oscillation module1which is cut along line A-A′ ofFIG. 1andFIG. 3is a sectional view of the oscillation module1which is cut along line B-B′ ofFIG. 1.FIG. 1toFIG. 3show the oscillation module1without a lid (cover), but the oscillation module1is actually configured by covering an opening of a package4with a lid (cover) (not shown).

As shown inFIG. 1, the oscillation module1of the embodiment is a surface acoustic wave (SAW) oscillator, and includes a surface acoustic wave filter (SAW filter)2, an integrated circuit (IC)3, and the package4.

The package4is, for example, a stacked package such as a ceramic package or the like, and accommodates the SAW filter2and the integrated circuit3in the same space. Specifically, an opening is provided on the upper portion of the package4, the opening is covered with a lid (cover) (not shown) to form an accommodation chamber, and the SAW filter and the integrated circuit3are accommodated in the accommodation chamber.

As shown inFIG. 2, a lower surface of the integrated circuit3is bonded and fixed to an upper surface of a first layer4A of the package4. Each electrode (pad)3B provided on the upper surface of the integrated circuit3and each electrode6B provided on an upper surface of a second layer4B of the package4are bonded to each other through a wire5B.

One end portion of the SAW filter2is fixed to the package4. More specifically, a lower surface of one end portion (first end portion)2A of the SAW filter2in a longitudinal direction is bonded and fixed to an upper surface of a third layer4C of the package4with an adhesive7. The other end portion (second end portion)2B of the SAW filter2in the longitudinal direction is not fixed and a gap is provided between the second end portion2B and the inner surface of the package4. That is, the SAW filter2is fixed to the package4in a cantilever state.

As shown inFIG. 1, four electrodes functioning as a first input port IP1, a second input port IP2, a first output port OP1, and a second output port OP2in the first end portion2A are provided on the upper surface of the SAW filter2. As shown inFIG. 1andFIG. 3, the first input port IP1, the second input port IP2, the first output port OP1, and the second output port OP2of the SAW filter2are bonded to four electrodes6A provided on the upper surface of the third layer4C of the package4through wires5A.

Wirings (not shown) for electrically connecting the four electrodes6A and the four predetermined electrodes6B respectively are provided in the package4. That is, the first input port IP1, the second input port IP2, the first output port OP1, and the second output port OP2of the SAW filter2are respectively connected to the four different electrodes (pads)3B of the integrated circuit3through the wires5A, the wires5B, and internal wirings of the package4.

A plurality of external electrodes (not shown) functioning as power terminals, grounding terminals, or output terminals are provided on the surface (external surface) of the package4, and wirings (not shown) for electrically connecting each of the plural external electrodes and each of the plural predetermined electrodes6B respectively are also provided in the package4.

FIG. 4is a plan view of the SAW filter2and the integrated circuit3in a plan view of the oscillation module1ofFIG. 1from the top.

As shown inFIG. 4, the SAW filter2includes a first interdigital transducer (IDT)201, a second IDT202, a first reflector203, and a second reflector204provided on a surface of a piezoelectric substrate200.

The piezoelectric substrate200can be manufactured by using a single crystal material such as crystal, lithium niobate (LiNbO3), lithium tantalate (LiTaO3), or lithium tetraborate (Li2B4O7, LBO), a piezoelectric thin film such as zinc oxide (ZnO) or aluminum nitride (AlN), or a piezoelectric ceramic material.

The first IDT201and the second IDT202are provided between the first reflector203and the second reflector204, and each IDT is disposed so that two pectinate electrodes including a plurality of electrode fingers provided at regular intervals oppose each other in a mutually inserted manner. As shown inFIG. 4, both of an electrode finger pitch of the first IDT201and an electrode finger pitch of the second IDT202is a constant value d1.

The SAW filter2includes the first input port IP1connected to the first IDT201, the second input port IP2connected to the first IDT201, the first output port OP1connected to the second IDT202, and the second output port OP2connected to the second IDT202which are provided on the surface of the piezoelectric substrate200.

Specifically, a first wiring205and a second wiring206are provided on the surface of the piezoelectric substrate200, the first input port IP1is connected to one electrode (upper electrode inFIG. 4) of the first IDT201through the first wiring205, and the second input port IP2is connected to the other electrode (lower electrode inFIG. 4) of the first IDT201through the second wiring206. A third wiring207and a fourth wiring208are provided on the surface of the piezoelectric substrate200, the first output port OP1is connected to one electrode (upper electrode inFIG. 4) of the second IDT202through the third wiring207, and the second output port OP2is connected to the other electrode (lower electrode inFIG. 4) of the second IDT202through the fourth wiring208.

In the SAW filter2configured as described above, when an electric signal having a frequency close to f=v/(2d1) (v is velocity at which the propagating of surface acoustic waves is carried out along the surface of the piezoelectric substrate200) is input from the first input port IP1and the second input port IP2, surface acoustic waves having one wavelength equivalent to 2d1is excited by the first IDT201. The surface acoustic waves excited by the first IDT201are reflected between the first reflector203and the second reflector204and become stationary waves. The stationary waves are converted into electric signals in the second IDT202and output from the first output port OP1and the second output port OP2. That is, the SAW filter2functions as a band pass filter in a narrowband in which a center frequency is f=v/(2d1).

In the embodiment, as shown inFIG. 4, at least a part of the SAW filter2is overlapped with the integrated circuit3in a plan view. In a plan view, the first end portion2A (portion with oblique lines inFIG. 4) of the SAW filter2is not overlapped with the integrated circuit3. As described above, in the embodiment, the SAW filter2is set in a cantilever state by fixing the first end portion2A to the package4, and the integrated circuit3is disposed in a space formed under the SAW filter2, to realize miniaturization of the oscillation module1.

According to the oscillation module1of the embodiment, since not the entire surface of the SAW filter2, but the first end portion2A which is a part thereof is fixed to the package4, an area of the portion to be fixed is small and the portion which is easily deformed due to stress applied from the package4is small. Therefore, according to the oscillation module1of the embodiment, it is possible to decrease degradation of an oscillation signal due to stress applied to the SAW filter2.

Since the rear surface of the piezoelectric substrate200of the first end portion2A of the SAW filter2is fixed to the package4with the adhesive7, the first end portion2A is also easily deformed due to shrinkage of the adhesive7. Therefore, in the embodiment, as shown inFIG. 4, the first IDT201, the second IDT202, the first reflector203, and the second reflector204are not provided on the surface of the piezoelectric substrate200of the first end portion2A. Accordingly, the deformation of the first IDT201and the second IDT202is significantly alleviated. Therefore, according to the embodiment, since it is possible to reduce errors with respect to a target value of the electrode finger pitch d1caused by deformation of the first IDT201or the second IDT202caused by the stress due to shrinkage of the adhesive7, it is possible to realize the oscillation module1with high frequency accuracy.

In the embodiment, since the SAW filter2is in a cantilever state, stress due to contact with the package4is not applied to the second end portion2B which is a free end. Accordingly, according to the embodiment, since the deformation of the first IDT201and the second IDT202caused by the stress due to the contact with the package4does not occur, it is possible to realize the oscillation module1with high frequency accuracy.

In the embodiment, the first input port IP1, the second input port IP2, the first output port OP1, and the second output port OP2, the characteristics of which do not change due to the modification, are provided on the surface of the piezoelectric substrate200of the first end portion2A of the SAW filter2. Therefore, an unnecessary increase in size of the SAW filter2is avoided and the oscillation module1can be miniaturized.

In the embodiment, as shown inFIG. 4, the SAW filter2has a rectangular shape including long sides2X and short sides2Y, and the first input port IP1, the second input port IP2, the first output port OP1, and the second output port OP2are arranged along the long side2X of the SAW filter2in a plan view. Therefore, according to the embodiment, as shown inFIG. 1, since all of four wires5A respectively connected to the first input port IP1, the second input port IP2, the first output port OP1, and the second output port OP2can be provided on the long side2X side in the outer portion of the SAW filter2, it is possible to reduce the space on a side of the short side by efficiently using the space on a side of the long side of the SAW filter2in the package4, therefore, it is possible to miniaturize the oscillation module1.

In the embodiment, as shown inFIG. 4, the first input port IP1and the second input port IP2are arranged to be equidistant from the long side2X and the first output port OP1and the second output port OP2are arranged to be equidistant from the long side2X, in a plan view. Accordingly, according to the embodiment, the length of the wirings (wire5A and substrate wiring) connected to the first input port IP1and the length of the wirings connected to the second input port IP2easily become to be equidistant from each other, the length of the wirings connected to the first output port OP1and the length of the wirings connected to the second output port OP2easily become to be equidistant from each other, and therefore, it is possible to reduce a deviation from 180° of a phase difference of differential signals input to or output from the SAW filter2.

In addition, in the embodiment, as shown inFIG. 4, the first input port IP1, the second input port IP2, the first output port OP1, the second output port OP2are arranged to be equidistant from the long side2X, in a plan view. Accordingly, the heights of the four wires5A respectively connected to the first input port IP1, the second input port IP2, the first output port OP1, the second output port OP2easily become the same. Particularly, in the embodiment, since the first input port IP1, the second input port IP2, the first output port OP1, the second output port OP2are provided at a position close to the long side2X along the long side2X, it is possible to reduce a height H1from the upper surface of the SAW filter2to the highest part of the wire5A, as shown in a sectional view on the left side ofFIG. 5(sectional view showing a part ofFIG. 3). The drawing on the right side ofFIG. 5shows a sectional view of a case where the first input port IP1, the second input port IP2, the first output port OP1, the second output port OP2are provided at a position far from the long side2X, and a height H2from the upper surface of the SAW filter2to the highest part of the wire5A is higher than the height H1. As described above, according to the embodiment, since the height of the wire5A can be decreased, it is possible to reduce the size of the package4in the height direction and to realize miniaturization of the oscillation module1.

In the embodiment, as shown inFIG. 4, the first input port IP1, the first output port OP1, the second output port OP2, and the second input port IP2are arranged in this order in a direction along the long side2X in a plan view. Therefore, in a case where the first IDT201and the second IDT202are arranged in a direction along the long side2X, it is easy to provide the first wiring205, the second wiring206, the third wiring207, and the fourth wiring208without causing intersection, and thus, it is possible to reduce the length of the wirings.

The SAW filter2is not limited to the configuration ofFIG. 4and may be a transversal SAW filter which propagates surface acoustic waves between an IDT for input and an IDT for output without including a reflector, for example.

1-2. Functional Configuration of Oscillation Module

FIG. 6is a block diagram showing an example of a functional configuration of the oscillation module1of the embodiment. As shown inFIG. 6, the oscillation module1of the embodiment includes the SAW filter2, a phase shift circuit10, a differential amplifier20(first differential amplifier), a capacitor32, a capacitor34, a differential amplifier40(second differential amplifier), a capacitor52, a capacitor54, a multiplication circuit60, a high pass filter70(filter circuit), and an output circuit80. Some elements of the oscillation module1of the embodiment may be suitably omitted or changed or other elements may be added.

The phase shift circuit10, the differential amplifier20, the capacitor32, the capacitor34, the differential amplifier40, the capacitor52, the capacitor54, the multiplication circuit60, the high pass filter70, and the output circuit80are contained in the integrated circuit3. That is, these circuits are some parts of the integrated circuit3.

The first output port OP1of the SAW filter2is connected to an input terminal T1of the integrated circuit3. The second output port OP2of the SAW filter2is connected to an input terminal T2of the integrated circuit3. The first input port IP1of the SAW filter2is connected to an output terminal T3of the integrated circuit3. The second input port IP2of the SAW filter2is connected to an output terminal T4of the integrated circuit3.

A power supply terminal T7of the integrated circuit3is connected to a VDD terminal which is an external terminal (external electrode provided on the surface of the package4) of the oscillation module1, and a desired power supply potential is supplied to the power supply terminal T7through the VDD terminal. A grounding terminal T8of the integrated circuit3is connected to a VSS terminal which is an external terminal of the oscillation module1, and a grounding potential (0 V) is supplied to the grounding terminal T8through the VSS terminal. The phase shift circuit10, the differential amplifier20, the capacitor32, the capacitor34, the differential amplifier40, the capacitor52, the capacitor54, the multiplication circuit60, the high pass filter70, and the output circuit80operate with a potential difference between the power supply terminal T7and the grounding terminal T8as a power supply voltage. Each power supply terminal and each grounding terminal of the differential amplifier20, the differential amplifier40, the multiplication circuit60, the high pass filter70, and the output circuit80are respectively connected to the power supply terminal T7and the grounding terminal T8and the connection thereof is not shown inFIG. 6.

The phase shift circuit10and the differential amplifier20are provided on a feedback path from the first output port OP1and the second output port OP2to the first input port IP1and the second input port IP2of the SAW filter2.

The phase shift circuit10includes a coil11(first coil), a coil12(second coil), and a variable capacitance element13. Inductance of the coil11and inductance of the coil12may be the same with each other (difference due to variation in manufacturing processes is allowable) or substantially the same with each other.

One end of the coil11is connected to the input terminal T1of the integrated circuit3and the other end of the coil11is connected to one end of the variable capacitance element13and a non-inversion input terminal of the differential amplifier20. One end of the coil12is connected to the input terminal T2of the integrated circuit3and the other end of the coil12is connected the other end of the variable capacitance element13and an inversion input terminal of the differential amplifier20.

The variable capacitance element13may be, for example, a varactor (also referred to as a varicap or a variable capacitance diode) of which a capacitance value changes according to a voltage applied, or may be a circuit which includes a plurality of capacitors, and a plurality of switches for selecting at least some of the plurality of capacitors and switches a capacitance value according to the capacitor selected by opening or closing the plurality of switches according to a selected signal.

The differential amplifier20outputs a pair of signals input to the non-inversion input terminal and the inversion input terminal from the non-inversion output terminal and the inversion output terminal by amplifying a potential difference therebetween. The non-inversion input terminal of the differential amplifier20is connected to the output terminal T3of the integrated circuit3and one end of the capacitor32. The inversion input terminal of the differential amplifier20is connected to the output terminal T4of the integrated circuit3and one end of the capacitor34.

FIG. 7is a view showing an example of a circuit configuration of the differential amplifier20. In the example ofFIG. 7, the differential amplifier20is configured to include a resistor21, a resistor22, a negative-channel metal oxide semiconductor (NMOS) transistor23, an NMOS transistor24, a constant current source25, an NMOS transistor26, an NMOS transistor27, a resistor28, and a resistor29. InFIG. 7, an input terminal IP20is a non-inversion input terminal and an input terminal IN20is an inversion input terminal, for example. In addition, an output terminal OP20is a non-inversion output terminal and an output terminal ON20is an inversion output terminal.

In the NMOS transistor23, a gate terminal is connected to the input terminal IP20, a source terminal is connected to one end of the constant current source25, and a drain terminal is connected to the power supply terminal T7(seeFIG. 6) through the resistor21.

In the NMOS transistor24, a gate terminal is connected to the input terminal IN20, a source terminal is connected to one end of the constant current source25, and a drain terminal is connected to the power supply terminal T7(seeFIG. 6) through the resistor22.

The other end of the constant current source25is connected to the grounding terminal T8(seeFIG. 6).

In the NMOS transistor26, a gate terminal is connected to the drain terminal of the NMOS transistor23, a source terminal is connected to the grounding terminal T8(seeFIG. 6) through the resistor28, and a drain terminal is connected to the power supply terminal T7(seeFIG. 6).

In the NMOS transistor27, a gate terminal is connected to the drain terminal of the NMOS transistor24, a source terminal is connected to the grounding terminal T8(seeFIG. 6) through the resistor29, and a drain terminal is connected to the power supply terminal T7(seeFIG. 6).

The source terminal of the NMOS transistor26is connected to the output terminal ON20and the source terminal of the NMOS transistor27is connected to the output terminal OP20.

The differential amplifier20configured as described above performs non-inversion amplification of a pair of signals input to the input terminal IP20and the input terminal IN20and outputs the signals from the output terminal OP20and the output terminal ON20.

Returning toFIG. 6, in the embodiment, one pair of signals is propagated on a signal path from the first output port OP1and the second output port OP2to the first input port IP1and the second input port IP2of the SAW filter2by the SAW filter2, the phase shift circuit10, and the differential amplifier20to configure a positive feedback closed loop and the one pair of signals become oscillation signals. That is, the oscillation circuit100is configured with the SAW filter2, the phase shift circuit10, and the differential amplifier20. Some elements of the oscillation circuit100of the embodiment may be suitably omitted or changed or other elements may be added.

An upper drawing ofFIG. 8shows a waveform of a signal (frequency f0) output from the first output port OP1of the SAW filter2using a solid line and a waveform of a signal (frequency f0) output from the second output port OP2of the SAW filter2using a broken line. A lower drawing ofFIG. 8shows a waveform of a signal (frequency f0) input to the first input port IP1of the SAW filter2using a solid line and a waveform of a signal (frequency f0) input to the second input port IP2of the SAW filter2using a broken line.

As shown inFIG. 8, the signal (solid line) propagating from the first output port OP1to the first input port IP1of the SAW filter2and the signal (broken line) propagating from the second output port OP2to the second input port IP2of the SAW filter2have phases opposite to each other. Here, “opposite phases” is an expression including not only a case where a phase difference is accurately 180°, but also a case where a phase difference between the wiring of the feedback path from the first output port OP1to the first input port IP1of the SAW filter2and the wiring of the feedback path from the second output port OP2to the second input port IP2of the SAW filter2is deviated from 180° by an amount of a difference in length, resistance, or capacitance, or a difference of characteristics of elements included in the differential amplifier20generated due to manufacturing errors.

As described above, the oscillation circuit100of the embodiment oscillates by amplifying the differential signals (one pair of signals having phases opposite to each other) output from the first output port OP1and the second output port OP2of the SAW filter2by the differential amplifier20and causing feedback of the signals to the first input port IP1and the second input port IP2of the SAW filter2to configure a feedback path of a closed loop. That is, the oscillation circuit100is operated by differential motion and oscillates at a frequency f0according to an electrode finger pitch d1of the first IDT201and the second IDT202.

Since power supply noise superimposed on the differential signal propagating on the feedback path from the first output port OP1and the second output port OP2to the first input port IP1and the second input port IP2of the SAW filter2through the power supply line is common mode noise, the power supply noise is significantly reduced by the differential amplifier20. Therefore, according to the oscillation circuit100, it is possible to reduce degradation of the oscillation signal due to the effect of the power supply noise and to improve frequency accuracy and S/N of the oscillation signal.

The oscillation circuit100of the embodiment changes a capacitance value of the variable capacitance element13of the phase shift circuit10, and accordingly, it is possible to change the frequency f0of the oscillation signal over a variable range according to the inductance of the coil11and the inductance of the coil12in a passband of the SAW filter2. As the inductance of the coil11and the inductance of the coil12are great, the variable range of frequency f0is great.

In the oscillation circuit100of the embodiment, current having phases opposite to each other flow to the coil11and the coil12. Accordingly, since a direction of a magnetic field generated by the coil11and a direction of a magnetic field generated by the coil12are opposite to each other and are weakened, it is possible to reduce the degradation of the oscillation signal due to the effect of the magnetic field.

A SAW resonator has rapidly-changing frequency characteristics with respect to reactance, whereas the SAW filter2has linear (slowly-changing) frequency characteristics with respect to reactance, and accordingly, the oscillation circuit100of the embodiment can easily control a variable range of the frequency f0compared to an oscillation circuit using the SAW resonator.

Returning toFIG. 6, the oscillation module1is provided with the capacitor32, the capacitor34, the differential amplifier40, the capacitor52, the capacitor54, the multiplication circuit60, the high pass filter70, and the output circuit80at a stage subsequent to the oscillation circuit100.

One end of the capacitor32is connected to the non-inversion output terminal (output terminal OP20ofFIG. 7) of the differential amplifier20and the other end thereof is connected to the non-inversion input terminal of the differential amplifier40. One end of the capacitor34is connected to the inversion output terminal (output terminal ON20ofFIG. 7) of the differential amplifier20and the other end thereof is connected to the inversion input terminal of the differential amplifier40. The capacitor32and the capacitor34function as capacitors for DC cut and removes DC components of each signal output from the non-inversion output terminal (output terminal OP20ofFIG. 7) and the inversion output terminal (output terminal ON20ofFIG. 7) of the differential amplifier20.

The differential amplifier40is provided on a signal path from the oscillation circuit100to the multiplication circuit60. The differential amplifier40outputs differential signals obtained by amplifying differential signals input to the non-inversion input terminal and the inversion input terminal from the non-inversion output terminal and the inversion output terminal.

FIG. 9is a view showing an example of a circuit configuration of the differential amplifier40. In the example ofFIG. 9, the differential amplifier40includes a resistor41, a resistor42, an NMOS transistor43, an NMOS transistor44, and a constant current source45. InFIG. 9, an input terminal IP40is a non-inversion input terminal and an input terminal IN40is an inversion input terminal, for example. In addition, an output terminal OP40is a non-inversion output terminal and an output terminal ON40is an inversion output terminal.

In the NMOS transistor43, a gate terminal is connected to the input terminal IP40, a source terminal is connected to one end of the constant current source45, and a drain terminal is connected to the power supply terminal T7(seeFIG. 6) through the resistor41.

In the NMOS transistor44, a gate terminal is connected to the input terminal IN40, a source terminal is connected to one end of the constant current source45, and a drain terminal is connected to the power supply terminal T7(seeFIG. 6) through the resistor42.

The other end of the constant current source45is connected to the grounding terminal T8(seeFIG. 6).

The drain terminal of the NMOS transistor43is connected to the output terminal OP40and the drain terminal of the NMOS transistor44is connected to the output terminal ON40.

The differential amplifier40configured as described above performs inversion amplification of the differential signals input to the input terminal IP40and the input terminal IN40and outputs the amplified differential signals from the output terminal OP40and the output terminal ON40.

Returning toFIG. 6, one end of the capacitor52is connected to the non-inversion output terminal (output terminal OP40ofFIG. 9) of the differential amplifier40and the other end thereof is connected to the non-inversion input terminal of the multiplication circuit60. One end of the capacitor54is connected to the inversion output terminal (output terminal ON40ofFIG. 9) of the differential amplifier40and the other end thereof is connected to the inversion input terminal of the multiplication circuit60. The capacitor52and the capacitor54function as capacitors for DC cut and remove DC components of each signal output from the non-inversion output terminal (output terminal OP40ofFIG. 9) and the inversion output terminal (output terminal ON40ofFIG. 9) of the differential amplifier40.

The multiplication circuit60is operated by differential motion and outputs differential signals obtained by multiplying the frequency f0of differential signals input to the non-inversion input terminal and the inversion input terminal from the non-inversion output terminal and the inversion output terminal.

FIG. 10is a view showing an example of a circuit configuration of the multiplication circuit60. In the example ofFIG. 10, the multiplication circuit60is configured to include a resistor61, a resistor62, an NMOS transistor63, an NMOS transistor64, an NMOS transistor65, an NMOS transistor66, an NMOS transistor67, an NMOS transistor68, and a constant current source69. InFIG. 10, an input terminal IP60is a non-inversion input terminal and an input terminal IN60is an inversion input terminal, for example. In addition, an output terminal OP60is a non-inversion output terminal and an output terminal ON60is an inversion output terminal.

In the NMOS transistor63, a gate terminal is connected to the input terminal IP60, a source terminal is connected to a drain terminal of the NMOS transistor65, and a drain terminal is connected to the power supply terminal T7(seeFIG. 6) through the resistor61.

In the NMOS transistor64, a gate terminal is connected to the input terminal IN60, a source terminal is connected to the drain terminal of the NMOS transistor65, and a drain terminal is connected to the power supply terminal T7(seeFIG. 6) through the resistor62.

In the NMOS transistor65, a gate terminal is connected to the input terminal IP60, a source terminal is connected to one end of the constant current source69, and a drain terminal is connected to the source terminal of the NMOS transistor63and the source terminal of the NMOS transistor64.

In the NMOS transistor66, a gate terminal is connected to the input terminal IN60, a source terminal is connected to a drain terminal of the NMOS transistor68, and a drain terminal is connected to the power supply terminal T7(seeFIG. 6) through the resistor61.

In the NMOS transistor67, a gate terminal is connected to the input terminal IP60, a source terminal is connected to the drain terminal of the NMOS transistor68, and a drain terminal is connected to the power supply terminal T7(seeFIG. 6) through the resistor62.

In the NMOS transistor68, a gate terminal is connected to the input terminal IN60, a source terminal is connected to one end of the constant current source69, and a drain terminal is connected to the source terminal of the NMOS transistor66and the source terminal of the NMOS transistor67.

The other end of the constant current source69is connected to the grounding terminal T8(seeFIG. 6).

The drain terminal of the NMOS transistor63and the drain terminal of the NMOS transistor66are connected to the output terminal OP60, and the drain terminal of the NMOS transistor64and the drain terminal of the NMOS transistor67are connected to the output terminal ON60.

The multiplication circuit60configured as described above generates differential signals of a frequency 2f0which is double of the frequency f0of the differential signals input to the input terminal IP60and the input terminal IN60and outputs the differential signals from the output terminal OP60and the output terminal ON60. Particularly, the multiplication circuit60is an equilibrium modulation circuit and has a configuration in which the differential signals (signal of f0) input to the input terminal IP60and the input terminal IN60are not output from the output terminal OP60and the output terminal ON60in principle. According to the multiplication circuit60, even after considering a manufacturing variation of each NMOS transistor or each resistor, it is possible to decrease the amount of signal components of f0output from the output terminal OP60and the output terminal ON60, differential signals of 2f0having high purity (high frequency accuracy) are obtained and the circuit area is also comparatively small.

Returning toFIG. 6, the non-inversion output terminal (output terminal OP60ofFIG. 10) of the multiplication circuit60is connected to the non-inversion input terminal of the high pass filter70. The inversion output terminal (output terminal ON60ofFIG. 10) of the multiplication circuit60is connected to the inversion input terminal of the high pass filter70.

The high pass filter70is provided on a signal path from the multiplication circuit60to the output circuit80. The high pass filter70is operated by differential motion and outputs differential signals having low frequency components attenuated from the differential signals input to the non-inversion input terminal and the inversion input terminal from the non-inversion output terminal and the inversion output terminal.

FIG. 11is a view showing an example of a circuit configuration of the high pass filter70. In the example ofFIG. 11, the high pass filter70is configured to include a resistor71, a capacitor72, a capacitor73, a coil74(third coil), a capacitor75, a capacitor76, and a resistor77. InFIG. 11, an input terminal IP70is a non-inversion input terminal and an input terminal IN70is an inversion input terminal, for example. In addition, an output terminal OP70is a non-inversion output terminal and an output terminal ON70is an inversion output terminal.

In the resistor71, one end is connected to the input terminal IP70and one end of the capacitor72and the other end is connected to the input terminal IN70and one end of the capacitor73.

In the capacitor72, one end is connected to the input terminal IP70and one end of the resistor71and the other end is connected to one end of the coil74and one end of the capacitor75.

In the capacitor73, one end is connected to the input terminal IN70and the other end of the resistor71and the other end is connected to the other end of the coil74and one end of the capacitor76.

In the coil74, one end is connected to the other end of the capacitor72and one end of the capacitor75and the other end is connected to the other end of the capacitor73and one end of the capacitor76.

In the capacitor75, one end is connected to the other end of the capacitor72and one end of the coil74and the other end is connected to one end of the resistor77.

In the capacitor76, one end is connected to the other end of the capacitor73and the other end of the coil74and the other end is connected to the other end of the resistor77.

In the resistor77, one end is connected to the other end of the capacitor75and the other end is connected to the other end of the capacitor76.

The other end of the capacitor75and one end of the resistor77are connected to the output terminal OP70and the other end of the capacitor76and the other end of the resistor77are connected to the output terminal ON70.

The high pass filter70configured as described above generates differential signals having low frequency components attenuated from the differential signals input to the input terminal IP70and the input terminal IN70and outputs the differential signals from the output terminal OP70and the output terminal ON70.

FIG. 12is a view showing an example of frequency characteristics of the high pass filter70.FIG. 12also shows frequency spectra of the output signal of the multiplication circuit60which is the input signal of the high pass filter70, using a broken line. InFIG. 12, a horizontal axis indicates the frequency and a vertical axis indicates the gain (case of frequency characteristics of high pass filter70) or power (case of frequency spectra of output signal of multiplication circuit60). As shown inFIG. 12, a resistance value of each resistor, a capacitance value of each capacitor, and an inductance value of the coil74are set so that the cut-off frequency fcof the high pass filter70is between f0and 2f0. As described above, the multiplication circuit60outputs differential signals of 2f0having a small amount of signal components of f0having high purity (high frequency accuracy), but as shown inFIG. 12, the signal components of f0which is lower than the cut-off frequency fcare attenuated by the high pass filter70, and accordingly, differential signals of 2f0having high purity (high frequency accuracy) are obtained.

Returning toFIG. 6, the non-inversion output terminal (output terminal OP70ofFIG. 11) of the high pass filter70is connected to the non-inversion input terminal of the output circuit80. The inversion output terminal (output terminal ON70ofFIG. 11) of the high pass filter70is connected to an inversion input terminal of the output circuit80.

The output circuit80is provided at a stage subsequent to the multiplication circuit60and the high pass filter70. The output circuit80is operated by differential motion, generates differential signals obtained by converting differential signals input to the non-inversion input terminal and inversion input terminal into signals at a desired voltage level (or current level), and outputs the differential signals from the non-inversion output terminal and the inversion output terminal. The non-inversion output terminal of the output circuit80is connected to the output terminal T5of the integrated circuit3and the inversion output terminal of the output circuit80is connected to the output terminal T6of the integrated circuit3. The output terminal T5of the integrated circuit3is connected to a CP terminal which is an external terminal of the oscillation module1and the output terminal T6of the integrated circuit3is connected to a CN terminal which is an external terminal of the oscillation module1. The differential signals (oscillation signals) converted by the output circuit80are output to the external portion from the CP terminal and the CN terminal of the oscillation module1through the output terminal T5and the output terminal T6of the integrated circuit3.

FIG. 13is a view showing an example of a circuit configuration of the output circuit80. In the example ofFIG. 13, the output circuit80is configured to include a differential amplifier81, an NPN transistor82, and an NPN transistor83. InFIG. 13, an input terminal IP80is a non-inversion input terminal and an input terminal IN80is an inversion input terminal, for example. In addition, an output terminal OP80is a non-inversion output terminal and an output terminal ON80is an inversion output terminal.

In the differential amplifier81, a non-inversion input terminal is connected to the input terminal IP80, an inversion input terminal is connected to the input terminal IN80, a non-inversion output terminal is connected to a base terminal of the NPN transistor82, and an inversion output terminal is connected to a base terminal of the NPN transistor83, and the differential amplifier is operated with a power supply voltage VDD supplied from the power supply terminal T7(seeFIG. 6) and the grounding terminal T8.

In the NPN transistor82, a base terminal is connected to the non-inversion output terminal of the differential amplifier81, a collector terminal is connected to the power supply terminal T7(seeFIG. 6), and an emitter terminal is connected to the output terminal OP80.

In the NPN transistor83, a base terminal is connected to the inversion output terminal of the differential amplifier81, a collector terminal is connected to the power supply terminal T7(seeFIG. 6), and an emitter terminal is connected to the output terminal ON80.

The output circuit80configured as described above is a positive emitter coupled logic (PECL) circuit or a low-voltage positive emitter coupled logic (LV-PECL) circuit, and pulls down the output terminal OP80and the output terminal ON80to a predetermined voltage V1to convert differential signals input from the input terminal IP80and the input terminal IN80into differential signals in which a high level is set as VDD-VCEand a low level is set as V1, and outputs the differential signals from the output terminal OP80and the output terminal ON80. The voltage VCEis a voltage between the collector and emitter terminals of the NPN transistor82or the NPN transistor83.

According to the oscillation module1of the embodiment described above, even when noise is superimposed on the power supplied to each circuit (the differential amplifier40, the multiplication circuit60, the high pass filter70, and the output circuit80) at a stage subsequent to the oscillation circuit100due to the operation of the oscillation circuit100, since all of the circuits are operated by differential motion, the power supply noise superimposed on the differential signals (oscillation signals) output by each circuit becomes common mode noise. Therefore, according to the oscillation module1of the embodiment, it is possible to output oscillation signals in which degradation due to the effect of the power supply noise generated due to the operation of the oscillation circuit100is reduced.

According to the oscillation module1of the embodiment, since the multiplication circuit60is provided at a stage subsequent to the oscillation circuit100, it is possible to output oscillation signals at a frequency obtained by the multiplication of a frequency of the oscillation signal output by the oscillation circuit100.

According to the oscillation module1of the embodiment, since the oscillation circuit100is operated by differential motion, the amount of power supply noise to be superimposed on the differential signals (oscillation signals) propagating on the feedback path of the oscillation circuit100as common mode noise is significantly decreased. Therefore, according to the oscillation module1of the embodiment, it is possible to improve frequency accuracy and S/N of the oscillation signal.

According to the oscillation module1of the embodiment, since the multiplication circuit60is an equilibrium modulation circuit, a signal at the same frequency as that of the signal input to the multiplication circuit60is not output from the multiplication circuit60, in principle (only signal obtained by the multiplication of the frequency of the signal input is output). Therefore, according to the oscillation module1of the embodiment, an oscillation signal at a multiplication frequency having high frequency accuracy is obtained.

In addition, in the oscillation module1of the embodiment, the oscillation circuit100outputs the differential signals and the circuits (the differential amplifier40, the multiplication circuit60, and the high pass filter70) on the signal path from the oscillation circuit100to the output circuit80is operated by differential motion. Since the power supply noise generated by the operation of the oscillation circuit100is superimposed on the differential signal input to each circuit through the power supply line as common mode noise, each circuit can output a differential signal having significantly reduced power supply noise by being operated by differential motion. The power supply noise (common mode noise) superimposed on the input signal of the output circuit80through the power supply line is also significantly reduced by operating the output circuit80by differential motion, in the same manner as described above. As described above, the oscillation module1of the embodiment can output an oscillation signal having high frequency accuracy in which degradation due to the effect of the power supply noise generated by the operation of the oscillation circuit100is reduced.

According to the oscillation module1of the embodiment, it is possible to optimally set a frequency accuracy of an oscillation signal by suitably selecting an amplification factor of the differential amplifier20provided in the oscillation circuit100and an amplification factor of the differential amplifier40provided at a stage subsequent to the oscillation circuit100. According to the oscillation module1of the embodiment, since it is possible to reduce the signal of unnecessary frequency components contained in the oscillation signal output by the multiplication circuit60by the high pass filter70, it is possible to improve frequency accuracy of the oscillation signal.

1-3. Layout of Integrated Circuit

In the oscillation module1of the embodiment, the layout of the integrated circuit3is worked in order to improve frequency accuracy of the differential signal output from the integrated circuit3.FIG. 14is a view showing an example of the layout arrangement of each circuit (excluding some) contained in the integrated circuit3.FIG. 14is a view when the integrated circuit3is seen in a plan view from a direction orthogonal to a surface of a semiconductor substrate where various elements (transistors or resistors) are laminated.FIG. 15is an enlarged view of parts of the input terminal T1, the input terminal T2, the phase shift circuit10, the differential amplifier20, and the high pass filter70among the view of the layout arrangement ofFIG. 14. InFIG. 15, the layout arrangement or some wiring patterns of the coil11, the coil12, and the variable capacitance element13contained in the phase shift circuit10, and the coil74contained in the high pass filter70are shown.

InFIG. 15, a virtual straight line VL is a straight line which passes a center point P between a center O1of the coil11and a center O2of the coil12and is orthogonal to a line segment L connecting the center O1of the coil11and the center O2of the coil12, that is, a straight line which is equidistant from the center O1of the coil11and the center O2of the coil12.

In the embodiment, as shown inFIG. 15, the differential amplifier20and the variable capacitance element13are arranged so as to cross the virtual straight line VL which is equidistant from the center O1of the coil11and the center O2of the coil12in a plan view of the integrated circuit3. With such layout arrangement, it is possible to reduce a difference between the length of the wiring connecting the other end of the coil11and the non-inversion input terminal of the differential amplifier20and the length of the wiring connecting the other end of the coil12and the inversion input terminal of the differential amplifier20. In the same manner as described above, it is possible to reduce a difference between the length of the wiring connecting one end of the variable capacitance element13and the non-inversion input terminal of the differential amplifier20and the length of the wiring connecting the other end of the variable capacitance element13and the inversion input terminal of the differential amplifier20. Accordingly, a difference in parasitic capacitance or parasitic resistance of a signal path from the other end of the coil11to the non-inversion input terminal of the differential amplifier20and a signal path from the other end of the coil12to the inversion input terminal of the differential amplifier20is reduced, and it is possible to reduce deviation from 180° of a phase difference of a differential signal propagating on the two signal paths or a difference in a noise level superimposed on the differential signals. Therefore, it is possible to improve frequency accuracy and S/N of the oscillation signal output by the oscillation circuit100.

In the embodiment, as shown inFIG. 15, the coil74is arranged so as to cross the virtual straight line VL which is equidistant from the center O1of the coil11and the center O2of the coil12in a plan view of the integrated circuit3. As shown inFIG. 15, the coil74may be arranged so that a center O3thereof is on the virtual straight line VL. When the wiring pattern of the coil11and the wiring pattern of the coil12are the same with each other, the directions of a current I1flowing to the coil11and a current I2flowing to the coil12are opposite to each other (opposite phases). That is, when the clockwise current I1flows to the coil11, the counterclockwise current I2flows to the coil12, and when the counterclockwise current I1flows to the coil11, the clockwise current I2flows to the coil12. Accordingly, on the virtual straight line VL, a direction of a magnetic field generated by the coil11and a direction of a magnetic field generated by the coil12are opposite to each other and are weakened. When the wiring pattern of the coil11and the wiring pattern of the coil12are the same with each other, ideally the inductance of the coil11and the inductance of the coil12are the same with each other and the current I1and the current I2are the same with each other. Practically, even after considering a manufacturing variation of wirings or various elements, since a difference between the inductance of the coil11and the inductance of the coil12or a difference between the current I1and the current I2is small, strength of a magnetic field generated by the coil11and strength of a magnetic field generated by the coil12are substantially the same with each other on the virtual straight line VL and are substantially canceled. Accordingly, with a magnetic field coupling between the coil74arranged so as to cross with the virtual straight line VL and the coil11and the coil12, it is possible to decrease a level of a signal of f0superimposed on a signal of 2f0output by the high pass filter70, and the oscillation module1can output an oscillation signal having high frequency accuracy.

In the embodiment, as shown inFIG. 15, the variable capacitance element13is arranged between the coil11and the coil12in a plan view of the integrated circuit3. As described above, the variable capacitance element13which is hardly affected by the magnetic field is arranged close to the coil11and the coil12and between the coil11and the coil12where the effect of the magnetic field generated by the coil11or the magnetic field generated by the coil12is easily received, it is possible to prevent an unnecessary increase in layout area. In addition, since both of the wiring connecting the other end of the coil11and one end of the variable capacitance element13and the wiring connecting the other end of the coil12and the other end of the variable capacitance element13are shortened, it is possible to reduce the layout area and to decrease parasitic capacitance or parasitic resistance of the wirings.

In the embodiment, as shown inFIG. 15, the differential amplifier20is arranged between the variable capacitance element13and the coil74in a plan view of the integrated circuit3. With such layout arrangement, it is possible to increase the distance between the coil11and the coil74or the distance between the coil12and the coil74by the length of the differential amplifier20while preventing an unnecessary increase in layout area, and therefore, it is possible to decrease strength of the magnetic field from the coil11and strength of the magnetic field from the coil12received by the coil74. Accordingly, it is possible to further decrease a level of the signal of f0superimposed on the signal of 2f0output by the high pass filter70due to the magnetic field coupling of the coil11, the coil12, and the coil74, and the oscillation module1can output an oscillation signal having higher frequency accuracy.

By shortening the distance between the variable capacitance element13and the differential amplifier20, both of the wiring connecting the other end of the coil11and the non-inversion input terminal of the differential amplifier20and the wiring connecting the other end of the coil12and the inversion input terminal of the differential amplifier20are shortened as a result. Accordingly, it is possible to reduce the layout area, parasitic capacitance or parasitic resistance of the signal path from the other end of the coil11to the non-inversion input terminal of the differential amplifier20and the parasitic capacitance or parasitic resistance of the signal path from the other end of the coil12to the inversion input terminal of the differential amplifier20are decreased, and it is possible to reduce deviation from 180° of a phase difference of a differential signal propagating on the two signal paths or a noise level superimposed on the differential signals.

In the embodiment, as shown inFIG. 15, the distance (for example, center-to-center distance) between the coil11and the input terminal T1(first pad) connected to the coil11with a wiring is shorter than the distance (for example, center-to-center distance) between the coil74and the input terminal T1. In addition, the distance (for example, center-to-center distance) between the coil12and the input terminal T2(second pad) connected to the coil12with a wiring is shorter than the distance (for example, center-to-center distance) between the coil74and the input terminal T2. With such layout arrangement, since the wiring connecting the input terminal T1and the coil11or the wiring connecting the input terminal T2and the coil12is shortened, it is possible to reduce the layout area and to decrease the parasitic capacitance or parasitic resistance of the wirings. Therefore, both of parasitic capacitance or parasitic resistance of a signal path from the input terminal T1to one end of the coil11and parasitic capacitance or parasitic resistance of a signal path from the input terminal T2to one end of the coil12are decreased, and it is possible to reduce deviation from 180° of a phase difference of a differential signal propagating on the two signal paths or a noise level superimposed on the differential signals.

With such layout arrangement, the distance between the input terminal T1and the coil74or the distance between the input terminal T2and the coil74(that is, distance from the output terminal of the high pass filter70) is increased. Accordingly, it is possible to reduce a possibility that the frequency component f0of the current flowing to the coil11or the coil12is coupled with the current of frequency 2f0flowing to the coil74through the input terminal T1or the input terminal T2. That is, the signal of f0input to the input terminal T1or the input terminal T2is hardly superimposed on the signal of 2f0output by the high pass filter70, and the oscillation module1can output an oscillation signal having high frequency accuracy.

In the embodiment, as shown inFIG. 14, the differential amplifier40is provided to be close to the differential amplifier20, the multiplication circuit60is provided in a position close to both of the differential amplifier40and the high pass filter70, the output circuit80is provided to be close to the high pass filter70, and the output terminal T5and the output terminal T6are provided to be close to the output circuit80. With such layout arrangement, it is possible to shorten each wiring connecting each circuit. Accordingly, it is possible to reduce the layout area of the integrated circuit3, and it is possible to reduce deviation from 180° of a phase difference of a differential signal propagating from the input terminal T1and the input terminal T2to the output terminal T5and the output terminal T6or a noise level superimposed on the differential signals.

As described above, according to the oscillation module1of the embodiment, it is possible to satisfy both of reduction (size reduction) of the layout area of the integrated circuit3and output of the differential signal having high frequency accuracy, by using the layout arrangement shown inFIG. 14andFIG. 15.

1-4. Modification Examples

In the embodiment, a variable range of the oscillation frequency is widened by providing the coil11and the coil12as members having inductance, on a feedback path from the first output port OP1and the second output port OP2to the first input port IP1and the second input port IP2of the SAW filter2. With respect to this, other members having inductance may be provided on the feedback path, instead of the coil11and the coil12or together with the coil11and the coil12. As members having inductance other than the coils, a bonding wire or a substrate wiring is used, for example, and the oscillation circuit100can change an oscillation frequency over a variable range according to an inductance value of the bonding wire or the substrate wiring.

In the oscillation module1of the embodiment, the high pass filter70containing the cut-off frequency fchigher than the frequency f0and containing the frequency 2f0in a passband at a stage subsequent to the multiplication circuit60, but the high pass filter may be replaced with a band pass filter containing the cut-off frequency on a low band side higher than the frequency f0and containing the frequency 2f0in a passband.

2. Electronic Device

FIG. 16is a functional block diagram showing an example of a configuration of an electronic device of the embodiment. An electronic device300of the embodiment is configured to include an oscillation module310, a central processing unit (CPU)320, an operation unit330, a read only memory (ROM)340, a random access memory (RAM)350, a communication unit360, and a display unit370. In the electronic device300of the embodiment, some of the constituent elements (units) ofFIG. 16may be omitted or modified, and the other constituent elements may be added.

The oscillation module310includes an oscillation circuit312. The oscillation circuit312includes a SAW filter (not shown) and generates an oscillation signal at a frequency based on a resonance frequency of the SAW filter.

The oscillation module310may include a multiplication circuit314or an output circuit316at a stage subsequent to the oscillation circuit312. The multiplication circuit314generates an oscillation signal obtained by multiplying the frequency of the oscillation signal generated by the oscillation circuit312. The output circuit316outputs the oscillation signal generated by the multiplication circuit314or the oscillation signal generated by the oscillation circuit312to the CPU320. The oscillation circuit312, the multiplication circuit314, and the output circuit316may be operated by differential motion.

The CPU320performs various calculation processes or control processes by using the oscillation signal input from the oscillation module310as a clock signal according to a program stored in the ROM340or the like. Specifically, the CPU320performs various processes according to an operation signal from the operation unit330, a process of controlling the communication unit360for performing data communication with an external device, or a process of transmitting a display signal for displaying various information items on the display unit370.

The operation unit330is an input device configured with an operation key or a button switch, and outputs the operation signal according to the operation performed by a user to the CPU320.

The ROM340stores a program or data allowing the CPU320to perform various calculation processes or control processes.

The RAM350is used as an operation area of the CPU320, and temporarily stores a program or data read out from the ROM340, data input from the operation unit330, and an operation result executed according to various programs by the CPU320.

The communication unit360performs various controls for satisfying data communication between the CPU320and an external device.

The display unit370is a display device configured with a liquid crystal display (LCD) or the like, and displays various information items based on a display signal input from the CPU320. A touch panel functioning as the operation unit330may be provided in the display unit370.

It is possible to realize an electronic device having high reliability, by using the oscillation circuit100of the embodiment, for example, as the oscillation circuit312or using the oscillation module1of the embodiment described above, for example, as the oscillation module310.

Various electronic devices are considered as the electronic device300. For example, a network device such as a beam transmission device using optical fiber, a broadcasting device, a communication device used in a satellite or a base station, a global positioning system (GPS) module, a personal computer (for example, a mobile-type personal computer, a laptop-type personal computer, or a tablet-type personal computer), a moving object terminal such as a smart phone or a mobile phone, a digital still camera, an ink jet type discharging apparatus (for example, ink jet printer), a storage area network apparatus such as a router or a switch, a local area network apparatus, an apparatus for moving object terminal base station, a television, a video camera, a video recorder, a car navigation apparatus, a real-time clock device, a pager, an electronic organizer (including a communication function), an electronic dictionary, a calculator, an electronic game device, a game controller, a word processer, a work station, a video phone, a security monitor, electronic binoculars, a point of sale (POS) terminal, medical equipment (for example, an electronic thermometer, a blood pressure meter, a blood glucose meter, an ECG measuring device, an ultrasound diagnostic device, an electronic endoscope), a fishfinder, a variety of measurement equipment, a meter (for example, meters for vehicles, aircraft, ships), a flight simulator, a head mounted display, motion tracing, motion tracking, a motion controller, PDR (pedestrian position and azimuth measurement), and the like can be exemplified.

As an example of the electronic device300of the embodiment, a transmission device functioning as an apparatus for terminal base station which performs communication with a terminal in a wired or wireless manner, for example, using the oscillation module310described above as a reference signal source is exemplified. By using the oscillation module1of the embodiment, for example, as the oscillation module310, it is possible to realize the desired electronic device300having higher frequency accuracy, higher performance, and higher reliability than the related art, which can be used in a communication base station, for example.

Another example of the electronic device300of the embodiment may be a communication device in which the communication unit360receives an external clock signal and the CPU320(processing unit) includes a frequency control unit which controls a frequency of the oscillation module310based on the external clock signal and an output signal of the oscillation module310.

3. Moving Object

FIG. 17is a view (top view) showing an example of a moving object of the embodiment. A moving object400shown inFIG. 17is configured to include an oscillation module410, controllers420,430, and440which perform various controls of an engine system, a brake system, a keyless entry system and the like, a battery450, and a backup battery460. In the moving object400of the embodiment, a part of the constituent elements (units) shown inFIG. 17may be omitted or modified, or other constituent elements may be added.

The oscillation module410includes an oscillation circuit (not shown) including a SAW filter (not shown) and generates an oscillation signal at a frequency based on a resonance frequency of the SAW filter.

The oscillation module410may include a multiplication circuit or an output circuit which is at a stage subsequent to this oscillation circuit. The multiplication circuit generates an oscillation signal obtained by multiplication of the frequency of the oscillation signal generated by the oscillation circuit. The output circuit outputs an oscillation signal generated by the multiplication circuit or an oscillation signal generated by the oscillation circuit. The oscillation circuit, the multiplication circuit, and the output circuit may be operated by differential motion.

The oscillation signal output by the oscillation module410is supplied to the controllers420,430, and440and is used, for example, as a clock signal.

The battery450supplies electric power to the oscillation module410and the controllers420,430, and440. The backup battery460supplies electric power to the oscillation module410and the controllers420,430, and440, when an output voltage of the battery450is decreased than a threshold value.

It is possible to realize a moving object having high reliability, by using the oscillation circuit100of each embodiment described above, for example, as an oscillation circuit included in the oscillation module410or the oscillation module1of each embodiment described above, for example, as the oscillation module410.

Various moving objects are considered as the moving object400, and include a vehicle (including an electric vehicle), an aircraft such as a jet or a helicopter, a ship, a rocket, or a satellite, for example.

The invention is not limited to the embodiments and various modifications can be made within a range of a gist of the invention.

The embodiments and the modification examples described above are merely examples and the invention is not limited thereto. For example, each embodiment and each modification example can be suitably combined with each other.

The invention includes substantially the same configuration as the configuration described in the embodiments (for example, a configuration having the same functions, methods, and results, or a configuration having the same object and effects). The invention includes a configuration obtained by replacing the non-essential parts of the configuration described in the embodiments. The invention includes a configuration for realizing the same operation effects or a configuration for reaching the same object as the configuration described in the embodiments. The invention includes a configuration obtained by adding the related art to the configuration described in the embodiments.

The entire disclosures of Japanese Patent Application Nos. 2015-209934, filed Oct. 26, 2015 and 2015-209935, filed Oct. 26, 2015 are expressly incorporated by reference herein.