Radio transmission apparatus

A radio transmission apparatus includes a radio transmission IC including a vibration element and a fractional N-PLL circuit and a power amplifier generating a radio transmission signal and a control device that controls the radio transmission IC, and a temperature detection element. The control device controls the fractional N-PLL circuit based on temperature information obtained from the temperature detection element such that a frequency of the radio transmission signal is temperature-compensated.

BACKGROUND

1. Technical Field

The present invention relates to a radio transmission apparatus.

2. Related Art

Since service providers can use specified low-power radio used for telemeter, telecontrol, data transmission, or the like without receiving license of radio stations in conformity to radio laws, the specified low-power radio has recently been used widely in various communication devices. In ARIB STD-T67 which is a standard of the specified low-power radio, multiple channels are defined at intervals of 12.5 kHz or intervals of 25 kHz in the 400 MHz bandwidth. Thus, in radio transmission apparatuses conforming to ARIB STD-T67, precision of a transmission frequency is requested to be within ±4 ppm in a full temperature range to be used in each channel to be used. In the related art, a radio transmission apparatus in which the request for such frequency precision is difficult includes a temperature compensated crystal oscillator (TCXO), a radio transmission integrated circuit (IC), and a controller, as illustrated inFIG. 11. The request for frequency precision has been satisfied by performing frequency conversion on an output signal of the temperature compensated crystal oscillator (TCXO) by the radio transmission IC under the control of the controller and generating a carrier wave of a desired frequency. Such a radio transmission apparatus is disclosed in, for example, JP-A-2008-85899.

However, since the temperature compensated crystal oscillator (TCXO) is an expensive component, there is a problem that a radio transmission apparatus of the related art including a temperature compensated crystal oscillator (TCXO) is necessarily expensive. In particular, since low cost is necessary in a miniature radio device such as a restaurant order-bell, it is difficult to use an expensive component such as a temperature compensated crystal oscillator (TCXO) included in a radio transmission apparatus.

SUMMARY

An advantage of some aspects of the invention is that it provides a radio transmission apparatus capable of realizing the same frequency precision as that of a radio transmission apparatus of the related art including a temperature compensated crystal oscillator (TCXO) further inexpensively.

Application Example 1

A radio transmission apparatus according to this application example includes: a vibration element; a radio transmission semiconductor device that includes a fractional N-PLL circuit generating a radio transmission clock signal based on an output signal of the vibration element and a power amplifier generating a radio transmission signal based on the clock signal; a control device that controls the radio transmission semiconductor device; and a temperature detection element that is connected to the control device. The control device controls the fractional N-PLL circuit based on temperature information obtained from the temperature detection element such that a frequency of the radio transmission signal is temperature-compensated.

In the radio transmission apparatus according to this application example, the control device can generate the radio transmission signal which is temperature-compensated appropriately without using an expensive temperature compensated crystal oscillator (TCXO) by adding the frequency temperature characteristics of the vibration element based on temperature information obtained from the temperature detection element and controlling the fractional N-PLL circuit. Accordingly, the radio transmission apparatus according to the application example can realize the same frequency precision as a radio transmission apparatus of the related art in which a temperature compensated crystal oscillator (TCXO) is included further inexpensively.

In the radio transmission apparatus according to this application example, the frequency of the transmission clock signal output by the fractional N-PLL circuit can be digitally set with excellent linearity. Therefore, an influence of manufacturing variation is smaller than in a temperature compensated crystal oscillator (TCXO) performing temperature compensation of an analog scheme and temperature compensation adjustment is also easy.

Application Example 2

In the radio transmission apparatus according to the application example, the temperature detection element may be a thermistor that detects temperature of the vibration element.

Application Example 3

In the radio transmission apparatus according to the application example, the vibration element may be an AT vibration element.

In the AT vibration element, the frequency temperature characteristics exhibit a cubic curve which has an inflexion point near 25° C. and a frequency deviation is relatively small in a broad temperature range (for example, −40° C. to +85° C.). Accordingly, in the radio transmission apparatus according to the application example, it is possible to set a frequency variable range and a resolution of the frequency of the fractional N-PLL circuit so that the temperature characteristics of the vibration element can be sufficiently compensated.

Application Example 4

In the radio transmission apparatus according to the application example, the radio transmission semiconductor device and the vibration element may be accommodated in one package.

According to this application example, it is possible to realize the miniature radio transmission apparatus compared to a case in which the radio transmission semiconductor device and the vibration element accommodated in separate packages are flatly disposed on the same substrate.

Application Example 5

In the radio transmission apparatus according to the application example, the temperature detection element and the vibration element may be accommodated in one package.

In the radio transmission apparatus according to this application example, it is possible to realize the miniature radio transmission apparatus compared to a case in which the temperature detection element and the vibration element accommodated in separate packages are flatly disposed on the same substrate.

In the radio transmission apparatus according to this application example, since the vibration element and the temperature detection element are disposed at spatially close positions one another, a difference between the actual temperature of the vibration element and the temperature detected by the temperature detection element decreases. As a result, since a temperature compensation error decreases, it is possible to improve the frequency precision of the radio transmission signal.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. The embodiments to be described below do not inappropriately limit content of the invention described in the appended claims. All of the elements to be described below may not be essential elements of the invention.

1. Radio Transmission Apparatus

1-1. First Embodiment

Configuration of Radio Transmission Apparatus

FIG. 1is a diagram illustrating the configuration of a radio transmission apparatus according to a first embodiment. As illustrated inFIG. 1, a radio transmission apparatus1according to the first embodiment is configured to include a radio transmission integrated circuit (IC)2(which is an example of a radio transmission semiconductor device), a vibration element3, a control device4, and a temperature detection element5.

The XG and XD terminals of the radio transmission IC2are electrically connected to two excitation elements (not illustrated) of the vibration element3(vibration element), respectively.

The EN, SCK, and SDIO terminals of the radio transmission IC2are terminals for 3-wire serial peripheral interface (SPI) communication with the control device4and are an enable input terminal, a clock input terminal, and a data input terminal in order.

The VSS terminal of the radio transmission IC2is a ground terminal which supplies a ground potential (0 V) to each circuit, excluding a power amplifier23(seeFIG. 2) to be described below. The VDD terminal is a power terminal which supplies a power voltage (for example, 3 V) to each circuit.

The PAOUT terminal of the radio transmission IC2is an output terminal of a radio transmission signal from the power amplifier23. The VSSPA terminal is a ground terminal which supplies the ground potential (0 V) to the power amplifier23.

The CKOUT terminal of the radio transmission IC2is an output terminal of a clock signal from an oscillation circuit21(seeFIG. 2) to be described below. The clock signal output from the CKOUT terminal is used as an interruption signal or a clock signal of the control device4.

The radio transmission IC2oscillates the vibration element3, generates a radio transmission clock signal based on the output signal of the vibration element3, and generates a radio transmission signal based on the clock signal.

As the vibration element3, for example, a quartz crystal vibration element, a surface acoustic wave (SAW) resonance element, another piezoelectric vibration element, or a micro electromechanical systems (MEMS) vibration element can be used. As a substrate material of the vibration element3, a piezoelectric single crystal such as quartz crystal, lithium tantalate, or lithium niobate, a piezoelectric material such as piezoelectric ceramics such as lead zirconate titanate, or a silicon semiconductor material can be used. As an excitation mechanism of the vibration element3, a mechanism by a piezoelectric effect may be used or electrostatic driving by the Coulomb force may be used.

The control device4is a device that controls the radio transmission IC2. Specifically, the control device4controls the radio transmission by the radio transmission IC2by writing desired setting values on various registers for radio transmission setting included in a logic circuit24(seeFIG. 2) to be described below via the EN, SCK, and SDIO terminals of the radio transmission IC2and further transmitting a radio transmission command. The control device4may be, for example, a micro controller unit (MCU).

The temperature detection element5outputs a signal according to the surrounding temperature (for example, a voltage according to temperature). The temperature detection element5may be a positive polarity element that has a higher output voltage as temperature is higher or may be a negative polarity element that has a lower output voltage as temperature is higher. The temperature detection element5may be, for example, a thermistor.

The temperature detection element5is disposed near the vibration element3and detects the temperature of the vibration element3(more accurately, the temperature near the vibration element3). For example, the temperature detection element5may be disposed alone near the vibration element3. The temperature detection element5may be included in the radio transmission IC2or the control device4and the radio transmission IC2or the control device4in which the temperature detection element5is included may be disposed near the vibration element3.

In the embodiment, the control device4controls a fractional N-PLL circuit22(seeFIG. 2) to be described below such that the frequency of the radio transmission signal output from the PAOUT terminal of the radio transmission IC2is temperature-compensated based on temperature information obtained from the temperature detection element5. Then, the radio transmission apparatus1wirelessly transmits the radio transmission signal with high precision of the frequency which is temperature-compensated via an antenna (not illustrated).

Configuration of Radio Transmission IC

FIG. 2is a diagram illustrating an example of the configuration of a radio transmission IC2. In the example ofFIG. 2, the radio transmission IC2is configured to include the oscillation circuit21, the fractional N-PLL circuit22, the power amplifier23, and the logic circuit24.

The oscillation circuit21is a circuit which oscillates the vibration element3electrically connected via the XG and XD terminals and amplifies an output signal of the vibration element3to give feedback to the vibration element3. The oscillation circuit21generates a clock signal (oscillation signal) based on the oscillation of the vibration element3and outputs the clock signal to the fractional N-PLL circuit22. The clock signal generated by the oscillation circuit21is output from the CKOUT terminal of the radio transmission IC2to be supplied as a clock signal or an interruption signal to the control device4.

A circuit formed by the vibration element3and the oscillation circuit21may be any of various types of oscillation circuits such as a pierce oscillation circuit, an inverter type oscillation circuit, a colpitts oscillation circuit, and a Hartley oscillation circuit.

The fractional N-PLL circuit22is configured to include a phase comparator (phase frequency detector: PFD), a charge pump (CP), a lowpass filter (LPF), a voltage controlled oscillator (VCO), and a divider (DIV).

The phase comparator (PFD) compares phase differences of the clock signal output by the oscillation circuit21and the clock signal output by the divider circuit (DIV) and outputs a comparison result as a pulse voltage.

The charge pump (CP) converts the pulse voltage output by the phase comparator (PFD) into a current and the lowpass filter (LPF) performs smoothing and voltage conversion on the current output by the charge pump (CP).

The voltage controlled oscillator (VCO) uses the output voltage of the lowpass filter (LPF) as a control voltage and outputs the clock signal (which is a radio transmission clock signal) of which the frequency varies according to the control voltage.

The divider (DIV) outputs a clock signal obtained by dividing the clock signal output by the voltage controlled oscillator (VCO) by a division ratio according to the control signal input from the logic circuit24.

The fractional N-PLL circuit22having such a configuration multiplies the frequency (for example, tens of MHz) of the clock signal from the oscillation circuit21according to the control signal input from the logic circuit24to generate a radio transmission clock signal (for example, a clock signal with hundreds of MHz) and outputs the radio transmission clock signal to the power amplifier23.

The power amplifier23generates a radio transmission signal based on the radio transmission clock signal output by the fractional N-PLL circuit22and outputs the radio transmission signal. The radio transmission signal output by the power amplifier23is output from the PAOUT terminal. In the embodiment, when an enable signal PA_EN from the logic circuit24is active (at a high level in the embodiment), the power amplifier23generates and outputs a radio transmission signal with power (amplitude) according to the control signal from the logic circuit24. When the enable signal PA_EN is inactive (at a low level in the embodiment), the power amplifier23stops an operation.

The logic circuit24operates in synchronization with the clock signal output by the oscillation circuit21and controls operations of the fractional N-PLL circuit22and the power amplifier23. In the embodiment, when the EN terminal is active (at a high level in the embodiment), the logic circuit24receives a command or data input from the SDIO terminal in synchronization with the clock signal input from the SCK terminal and performs a process according to the received command and data. Specifically, the logic circuit24includes a register group formed by various registers for radio transmission setting. When the logic circuit24receives a register writing command, a register address, and setting data, the logic circuit24performs a process of writing the setting data on the register designated with the register address. When the logic circuit24receives the radio transmission command, the logic circuit24sets the enable signal PA_EN to be active (at the high level) at a predetermined timing and controls the frequency of the radio transmission clock signal output by the fractional N-PLL circuit22or the power of the radio transmission signal output by the power amplifier23according to setting values of various registers for radio setting and transmission data (wirelessly transmitted data) input from the SDIO terminal.

In the embodiment, the control device4can select one of frequency shift keying (FSK) modulation and amplitude shift keying (ASK) modulation as a modulation scheme of the radio transmission signal by the radio transmission IC2. The modulation scheme of the radio transmission signal is designated with 1 bit of the radio transmission command.

FIG. 3is a timing chart illustrating examples of waveforms and timings of radio transmission signals output from the PAOUT terminal in a case in which the frequency shift keying (FSK) modulation is selected. InFIG. 3, data to be transmitted wirelessly is 4 bits of “0”, “1”, “0”, and “1”.

As in the example ofFIG. 3, for the radio transmission signal in the case in which the frequency shift keying (FSK) modulation is selected, a frequency (transmission frequency) corresponding to the transmission data “0” is FTX−FDEVand a frequency (transmission frequency) corresponding to the transmission data “1” is FTX+FDEVwithout a change in the constant amplitude. Here, FTXis a center frequency (carrier wave frequency) decided according to a setting value of the register and FDEVis a modulation width (modulation frequency) decided according to a setting value of the register.

In the embodiment, in the case in which the frequency shift keying (FSK) modulation is selected, the logic circuit24generates a control signal to control a division ratio of the fractional N-PLL circuit22based on the transmission data and the setting value of the register such that the transmission frequencies are FTX−FDEVand FTX+FDEVaccording to the transmission data “0” and “1”.

Here, when N is assumed to be an integer part (integer division ratio) of the division ratio of the fractional N-PLL circuit22and F/M is a fraction part (fractional division ratio), a relation of formula (1) below is established between a frequency (reference frequency) FREFof the clock signal from the oscillation circuit21and a frequency FPLLof the clock signal output by the fractional N-PLL circuit22.

Accordingly, for example, the register group of the logic circuit24is provided with a register for setting the values of the integer division ratio N and the fraction division ratio F/M and a register for setting the modulation width (modulation frequency) FDEV. Before the radio transmission command is transmitted, the control device4sets the desired modulation width (modulation frequency) FDEVin the register and sets the integer division ratio N and the fraction division ratio F/M in the register so that the frequency FPLLof the clock signal output by the fractional N-PLL circuit22is substantially identical to the center frequency (carrier wave frequency) FTXaccording to formula (1). After a radio transmission command by which the frequency shift keying (FSK) modulation is selected is received, the logic circuit24calculates a division ratio of the fractional N-PLL circuit22for each piece of transmission data using the setting values of the registers of the integer division ratio N, the fraction division ratio F/M, and the modulation width (modulation frequency) FDEVand performs delta-sigma modulation to generate a control signal of the fractional N-PLL circuit22so that a time average value of the division ratios is identical to the calculated value.

FIG. 4is a timing chart illustrating examples of waveforms and timings of radio transmission signals output from the PAOUT terminal in a case in which the amplitude shift keying (ASK) modulation is selected. InFIG. 4, data to be transmitted wirelessly is 4 bits of “0”, “1”, “0”, and “1”.

As in the example ofFIG. 4, for the radio transmission signal in the case in which the amplitude shift keying (ASK) modulation is selected, the transmission frequency remains unchanged as the center frequency (carrier wave frequency) FTX, the amplitude corresponding to the transmission data “0” becomes AML, and the amplitude corresponding to the transmission data “1” becomes AMH.

In the embodiment, in the case in which the amplitude shift keying (ASK) modulation is selected, the logic circuit24generates a control signal to control the division ratio of the fractional N-PLL circuit22based on the setting values of the registers so that the transmission frequency becomes FTX. The logic circuit24generates a control signal to control an output amplitude of the power amplifier23based on the setting values of the registers and the transmission data so that the amplitude of the radio transmission signal output by the power amplifier23becomes AML or AMH according to the transmission data “0” and “1”.

For example, the register group of the logic circuit24is provided with a register for setting the values of the integer division ratio N and the fraction division ratio F/M and a register for setting the amplitudes AML and AMH. Before the radio transmission command is transmitted, the control device4sets the desired amplitudes AML and AMH in the register and sets the integer division ratio N and the fraction division ratio F/M in the register so that the frequency FPLLof the clock signal output by the fractional N-PLL circuit22is substantially identical to the center frequency (carrier wave frequency) FTXaccording to formula (1). After a radio transmission command by which the amplitude shift keying (ASK) modulation is selected is received, the logic circuit24performs delta-sigma modulation using the setting values of the registers of the integer division ratio N and the fraction division ratio F/M to generate a control signal of the fractional N-PLL circuit22so that a time average value of the division ratios of the fractional N-PLL circuit22is identical to N+F/M. After the radio transmission command by which the amplitude shift keying (ASK) modulation is selected is received, the logic circuit24generates a control signal to control an output amplitude of the power amplifier23according to the transmission data using the setting values of the registers of amplitudes AML and AMH.

Incidentally, in a case in which a broad temperature range (for example, −40° C. to +85° C.) is defined as an operation guarantee temperature of the radio transmission apparatus1, a frequency (reference frequency FREF) of the clock signal output by the oscillation circuit21considerably varies according to the temperature due to the frequency temperature characteristics of the vibration element3. Therefore, in the embodiment, the control device4has information regarding the frequency temperature characteristics of the vibration element3and calculates the division ratios (the integer division ratio N and the fraction division ratio F/M) of the fractional N-PLL circuit22so that the transmission frequency of the radio transmission signal is temperature-compensated and a desired frequency is maintained regardless of temperature based on the information regarding the frequency temperature characteristics and temperature information obtained from the output signal of the temperature detection element5.

Then, as described above, before the radio transmission command is transmitted, the control device4sets the calculated integer division ratio N and fraction division ratio F/M in the register. Accordingly, the radio transmission IC2receiving the radio transmission command from the control device4can output the radio transmission signal with high frequency precision regardless of temperature.

In particular, in order to realize the radio transmission apparatus1in which the frequency precision of the radio transmission signal is equal to or less than ±4 ppm in conformity to ARIB STD-T67, the vibration element3is preferably an AT vibration element (AT cut quartz crystal vibration element). In the AT vibration element, the frequency temperature characteristics exhibit a cubic curve which has an inflexion point near 25° C. and a frequency deviation is relatively small in the broad temperature range (for example, −40° C. to +85° C.). Therefore, it is possible to set a variable range of the frequency of the clock signal output by the fractional N-PLL circuit22, that is, a variable range of the division ratio N+F/M of the fractional N-PLL circuit22, and a resolution of the division ratio N+F/M necessary to realize the frequency precision equal to or less than ±4 ppm so that the temperature characteristics of the vibration element3can be sufficiently compensated. Accordingly, it is possible to realize the miniature radio transmission apparatus1outputting the radio transmission signal with the high frequency precision.

Sequence of Radio Transmission

FIG. 5is a flowchart illustrating an example of a sequence of radio transmission by the radio transmission apparatus1.

In the example ofFIG. 5, the control device4first detects a start event of the radio transmission (S10). For example, in a case in which a desired signal (for example, a signal indicating that a button or a switch is pushed) from an input device (a button, a switch, or the like) (not illustrated) is received, the control device4may detect the start event of the radio transmission or may detect the start event of the radio transmission whenever a preset certain time passes.

Next, the control device4calculates the temperature (acquires the temperature information) based on the output signal of the temperature detection element5(S20). For example, the control device4may maintain a calculation formula or table information indicating a relation between the output voltage and the temperature of the temperature detection element5and calculate the temperature using the calculation formula or the table information.

Next, the control device4calculates the division ratio of the fractional N-PLL circuit22according to the temperature calculated in step S20so that the frequency of the radio transmission by the radio transmission IC2is temperature-compensated (S30). For example, the control device4maintains information regarding the frequency temperature characteristic of the vibration element3, calculates the frequency FREFof the vibration element3at the temperature calculated in step S20using the information regarding the frequency temperature characteristics, and calculates the integer division ratio N and the fraction division ratio F/M satisfying FPLL=FTXfrom formula (1).

Next, the control device4writes the setting value of the fractional N-PLL circuit22and the setting value of the power amplifier23on the register of the radio transmission IC2(S40). That is, the control device4transmits the register writing command to the radio transmission IC2and writes the modulation width (the modulation frequency) FDEVof the radio transmission signal and the division ratios (the integer division ratio N and the fraction division ratio F/M) and the like calculated in step S30as the setting values of the fractional N-PLL circuit22on the register. The control device4transmits the register writing command to the radio transmission IC2and writes the amplitudes AML and AMH of the radio transmission signal as the setting values of the power amplifier23on the register.

Next, the control device4transmits the radio transmission command and the transmission data to the radio transmission IC2(S50).

Finally, the radio transmission IC2receives the radio transmission command and the transmission data, generates the radio transmission signal of the desired frequency which is temperature-compensated according to the register setting value of the fractional N-PLL circuit22, the register setting value of the power amplifier23, and the received transmission data, and wirelessly transmits the radio transmission signal (S60).

After the start event of the radio transmission is detected in step S10, that is, immediately before the radio transmission is performed, the control device4acquires the output signal of the temperature detection element5in step S20to decrease the difference between the temperature used to calculate the division ratio of the fractional N-PLL circuit22in step S30and the temperature at the time of actual radio transmission in step S60, and therefore the temperature compensation precision can be improved and the radio transmission can be performed at high frequency precision.

Frequency Temperature Characteristics of Radio Transmission Signals

FIG. 6is a diagram illustrating an example of the frequency temperature characteristics of radio transmission signals output by the radio transmission apparatus1according to the embodiment. The horizontal axis represents the operation temperature (unit: ° C.) of the radio transmission apparatus1and the vertical axis represents a frequency deviation ΔF (unit: ppm) of the radio transmission signal.

InFIG. 6, G1is a graph which indicates an example of the frequency temperature characteristics of the vibration element3and corresponds to the temperature characteristics of the reference frequency FREFof formula (1). In the example ofFIG. 6, the vibration element3indicates an AT vibration element and the graph G1indicates a cubic curve which has an inflexion point near 25° C.

G2is a graph which indicates an example of the frequency temperature characteristics (the temperature characteristics of the frequency FPLL) of the clock signal output by the fractional N-PLL circuit22in a case in which the reference frequency FREFat 25° C. in formula 1 is assumed to be a fixed value (a value at 25° C.) regardless of temperature. In the example ofFIG. 6, the setting resolution of a division ratio N+F/M of the fractional N-PLL circuit22is about 0.5 ppm and the graph G2has the frequency characteristics reverse to the graph G1using 0.5 ppm as a minimum unit.

G3is a graph which indicates an example of the frequency temperature characteristics of the radio transmission signal output by the radio transmission apparatus1and corresponds to the temperature characteristics of the frequency FPLLof formula 1. The graph G3corresponds to a difference between the graphs G1and G2and has the frequency temperature characteristics of the radio transmission signal which is temperature-compensated. In the example ofFIG. 6, the frequency precision of the radio transmission signal equal to or less than ±4 ppm defined in ARIB STD-T67 is sufficiently achieved in the operation temperature range of −40° C. to +85° C.

The control device4may maintain, for example, a relation formula (approximation formula) or table information of the temperature and the frequency deviation corresponding to the graph G1as the information regarding the frequency temperature characteristics of the foregoing vibration element3, may maintain a relation formula (approximation formula) or table information of the temperature and the frequency deviation corresponding to the graph G2, or may maintain a relation formula (approximation formula) or table information of the division ratio N+F/M of the fractional N-PLL circuit22and the temperature used to obtain the graph G2.

Advantages

As described above, in the radio transmission apparatus1according to the first embodiment, the control device4can generate the radio transmission signal which is temperature-compensated appropriately using, for example, the inexpensive vibration element3such as an AT vibration element without using an expensive temperature compensated crystal oscillator (TCXO) by adding the frequency temperature characteristics of the vibration element3based on the temperature information obtained from the temperature detection element5and controlling the division ratio of the fractional N-PLL circuit22. Accordingly, the radio transmission apparatus1according to the first embodiment can realize the same frequency precision as a radio transmission apparatus of the related art in which a temperature compensated crystal oscillator (TCXO) is included further inexpensively.

In the radio transmission apparatus1according to the first embodiment, the frequency of the transmission clock signal output by the fractional N-PLL circuit22can be digitally set with excellent linearity. Therefore, an influence of manufacturing variation is smaller than in a temperature compensated crystal oscillator (TCXO) performing temperature compensation of an analog scheme and control (temperature compensation adjustment) of the fractional N-PLL circuit22by the control device4is also easy.

1-2. Second Embodiment

FIG. 7is a diagram illustrating the configuration of a radio transmission apparatus according to a second embodiment. InFIG. 7, the same reference numerals are given to the same constituent elements as those inFIG. 1. Hereinafter, the same reference numerals are given to the same configuration as that of the first embodiment. The different content from the first embodiment will be mainly described and the description of the common content to that of the first embodiment will be omitted or simplified. As illustrated inFIG. 7, a radio transmission apparatus1according to the second embodiment is the same as that of the first embodiment in that a radio transmission IC2(which is an example of a radio transmission semiconductor device), a vibration element3, a control device4, and a temperature detection element5are included, and the functions of the radio transmission IC2, the vibration element3, the control device4, and the temperature detection element5are the same as those of the first embodiment. The radio transmission apparatus1is different from that of the first embodiment in that the radio transmission unit6is configured such that the radio transmission IC2and the vibration element3are accommodated in one package.

In the embodiment, the radio transmission unit6includes eight EN, SCK, SDIO, VSS, VDD, PAOUT, VSSPA, and CKOUT terminals provided on the surface of the package which are electrically connected to EN, SCK, SDIO, VSS, VDD, PAOUT, VSSPA, and CKOUT terminals of the radio transmission IC2, respectively.

The EN, SCK, and SDIO terminals of the radio transmission unit6are terminals for 3-wire SPI communication with the control device4and are an enable input terminal, a clock input terminal, and a data input terminal in order.

The VSS terminal of the radio transmission unit6is a ground terminal which supplies a ground potential (0 V) to each circuit, excluding the power amplifier23(seeFIG. 2) of the radio transmission IC2. The VDD terminal is a power terminal which supplies a power voltage (for example, 3 V) to each circuit.

The PAOUT terminal of the radio transmission unit6is an output terminal of a radio transmission signal from the power amplifier23of the radio transmission IC2. The VSSPA terminal is a ground terminal which supplies the ground potential (0 V) to the power amplifier23of the radio transmission IC2.

The CKOUT terminal of the radio transmission unit6is an output terminal of a clock signal from the oscillation circuit21(seeFIG. 2) of the radio transmission IC2. The clock signal output from the CKOUT terminal is used as an interruption signal or a clock signal of the control device4.

The control device4controls the radio transmission IC2via the EN, SCK, and SDIO terminals of the radio transmission unit6.

In the second embodiment, the temperature detection element5is disposed near the radio transmission unit6and detects the temperature (the temperature of the vibration element3) of the radio transmission unit6. The temperature detection element5may be, for example, a thermistor. In the embodiment, the control device4controls the fractional N-PLL circuit22(seeFIG. 2) of the radio transmission IC2such that the frequency of the radio transmission signal output from the PAOUT terminal of the radio transmission unit6is temperature-compensated based on temperature information obtained from the temperature detection element5.

FIGS. 8A to 8Care diagrams illustrating an example of the structure of the radio transmission unit6.FIG. 8Ais a top view illustrating the radio transmission unit6.FIG. 8Bis a bottom view illustrating the radio transmission unit6.FIG. 8Cis a sectional view illustrating the radio transmission unit6taken along the line VIIIC-VIIIC ofFIG. 8Awhen viewed in a direction indicated by the arrow.FIG. 8Aillustrates a state in which a lid69inFIG. 8Cis not present.

As illustrated inFIGS. 8A to 8C, the radio transmission unit6is configured to include the radio transmission IC2, the vibration element (vibration element)3, a package61, a seaming ring62, and the lid (cover)69.

The package61accommodates the radio transmission IC2and the vibration element3in the same space. Specifically, an opening is formed in the upper surface of the package61and the seaming ring62disposed to surround the opening of the package61and the lid69are welded to seal the opening of the package61, so that the radio transmission IC2and the vibration element3are accommodated in the same space.

The vibration element3includes metal excitation electrodes3aand3bon the front and rear surfaces, respectively, and oscillates at a desired frequency according to the mass or the shape of the vibration element3including the excitation electrodes3aand3b. The vibration element3may be, for example, an AT vibration element. The vibration element3is fixed to electrode pads65disposed on the package61by a connection member66such as a conductive adhesive. The radio transmission IC2is joined to the package61by an adhesive member68such as lysine.

Wires (not illustrated) electrically connecting the two electrode pads63respectively bonded with the XG and XD terminals of the radio transmission IC2to the two electrode pads65connected to two terminals (the excitation electrodes3aand3b) of the vibration element3are provided inside or on the front surface of the package61.

Wires (not illustrated) electrically connecting the eight electrode pads63respectively bonded with the EN, SCK, SDIO, VSS, VDD, PAOUT, VSSPA, and CKOUT terminals of the radio transmission IC2to eight EN, SCK, SDIO, VSS, VDD, PAOUT, VSSPA, and CKOUT terminals (electrodes)67provided on the bottom surface of the package61are provided inside or on the front surface of the package61.

In this way, according to the second embodiment, as illustrated inFIGS. 8A to 8C, the radio transmission IC2and the vibration element3are accommodated in one package61. Further, in a plan view when the radio transmission unit6is viewed from the upper surface, the radio transmission IC2and the vibration element3overlap each other. Therefore, the radio transmission apparatus1can be miniaturized compared to a case in which the radio transmission IC2and the vibration element3accommodated in separate packages are flatly disposed on the same substrate.

FIG. 9is a diagram illustrating the configuration of a radio transmission apparatus according to a third embodiment. InFIG. 9, the same reference numerals are given to the same constituent elements as those inFIG. 1. Hereinafter, the same reference numerals are given to the same configuration as that of the first embodiment. The different content from the first embodiment will be mainly described and the description of the common content to that of the first embodiment will be omitted or simplified. As illustrated inFIG. 9, a radio transmission apparatus1according to the third embodiment is the same as that of the first embodiment in that a radio transmission IC2(which is an example of a radio transmission semiconductor device), a vibration element3, a control device4, and a temperature detection element5are included, and the functions of the radio transmission IC2, the vibration element3, the control device4, and the temperature detection element5are the same as those of the first embodiment. The radio transmission apparatus1is different from that of the first embodiment in that a vibrator7is configured such that the temperature detection element5and the vibration element3are accommodated in one package.

In the embodiment, the vibrator7includes four XG, XD, TS, and VS terminals provided on the front surface of the package.

The XG and XD terminals of the vibrator7are electrically connected to two excitation electrodes (not illustrated) of the vibration element3(vibration element) and XG and XD terminals of the radio transmission IC2, respectively.

The TS terminal of the vibrator7is electrically connected to an output terminal of the temperature detection element5, and thus an output signal of the temperature detection element5output from the TS terminal is input to the control device4.

The VSS terminal of the vibrator7is a ground terminal which supplies the ground potential (0 V) to the temperature detection element5.

In the third embodiment, the temperature detection element5in the vibrator7detects the temperature of the vibration element3. The control device4controls the fractional N-PLL circuit22(seeFIG. 2) of the radio transmission IC2such that the frequency of the radio transmission signal output from the PAOUT terminal of the radio transmission IC2is temperature-compensated based on temperature information obtained from the TS terminal of the vibrator7.

FIGS. 10A to 10Care diagrams illustrating an example of the structure of the vibrator7.FIG. 10Ais a top view illustrating the vibrator7.FIG. 10Bis a bottom view illustrating the vibrator7.FIG. 10Cis a sectional view illustrating the vibrator7taken along the line XC-XC ofFIG. 10Awhen viewed in a direction indicated by the arrow.FIG. 10Aillustrates a state in which a lid79inFIG. 10Cis not present.

As illustrated inFIGS. 10A to 10C, the vibrator7is configured to include the vibration element (vibration element)3, the temperature detection element5, a package71, a seaming ring72, and the lid (cover)79.

As illustrated inFIG. 10C, two concave portions are formed in facing surfaces in the package71. The vibration element3is accommodated in one concave portion and the temperature detection element5is accommodated in the other concave portion. Specifically, an opening is formed in the upper surface of the package71and the seaming ring72disposed to surround the opening of the upper surface of the package71and the lid79are welded to seal the opening of the upper surface of the package71, so that the vibration element3is accommodated in the concave portion on the upper side of the package71. An opening is also formed in the lower surface (bottom surface) of the package71. The opening of the lower surface (bottom surface) of the package71is not sealed and the temperature detection element5is accommodated in the concave portion on the lower side of the package71. Since the opening of the lower surface (bottom surface) of the package71is not sealed, the temperature detection element5can detect ambient temperature around the vibrator7(the vibration element3).

The vibration element3includes the metal excitation electrodes3aand3bon the front and rear surfaces, respectively, and oscillates at a desired frequency according to the mass or the shape of the vibration element3including the excitation electrodes3aand3b. The vibration element3may be, for example, an AT vibration element. The vibration element3is fixed to electrode pads75disposed on the package71by a connection member76such as a conductive adhesive. The temperature detection element5may be, for example, a thermistor and both ends of the temperature detection element5are joined to electrode pads73disposed on the package71by a connection member78such as a conductive adhesive.

Wires (not illustrated) electrically connecting the two electrode pads75connected to two terminals (the excitation electrodes3aand3b) of the vibration element3and two XG and XD terminals (electrodes)77formed on the bottom surface of the package71are provided inside or on the front surface of the package71.

Further, wires (not illustrated) electrically connecting the two electrode pads73respectively electrically connected to both ends of the temperature detection element5to the two TS and VSS terminals (electrodes)77formed on the bottom surface of the package71are provided inside or on the front surface of the package71.

The radio transmission apparatus1having such a configuration according to the third embodiment has the same advantages as the first embodiment. Further, according to the third embodiment, as illustrated inFIGS. 10A to 10C, the vibration element3and the temperature detection element5are accommodated in one package71. Further, in a plan view when the vibrator7is viewed from the upper surface, the vibration element3and the temperature detection element5overlap each other. Therefore, the radio transmission apparatus1can be miniaturized compared to a case in which the vibration element3and the temperature detection element5accommodated in separate packages are flatly disposed on the same substrate.

According to the third embodiment, since the vibration element3and the temperature detection element5are disposed at spatially close locations one another, a difference between the actual temperature of the vibration element3and the temperature detected by the temperature detection element5decreases. As a result, since a temperature compensation error decreases, it is possible to improve the frequency precision of the radio transmission signal.

2. Application Examples

The radio transmission apparatus1according to the above-described embodiments can be applied to various electronic apparatuses or systems. For example, the radio transmission apparatus1according to the above-described embodiments can be applied to, for example, a radio transmission apparatus which is included in a restaurant order-bell and wirelessly transmits information regarding pressing of a button, a radio transmission apparatus which is included in a remote controller for manipulation of a golf cart or the like and wirelessly transmits instruction information of a user to the golf cart, a radio transmission apparatus which is included in a temperature measurer of a green house or the like and wirelessly transmits temperature data, and a radio transmission apparatus which is included in an apparatus measuring vital data of a patient and wirelessly transmit the vital data. For example, it is also possible to construct a data collection system capable of collecting data measured and wirelessly transmitted by a plurality of data measurers in which the radio transmission apparatus1is included and performing various calculation processes.

The invention is not limited to the embodiment, but may be modified in various forms within the scope of the gist of the invention.

The above-described embodiments are merely examples and the invention is not limited thereto. For example, the embodiments can also be appropriately combined.

The invention includes configurations (for example, configurations of the same functions, methods, and results or configurations with the same objectives and advantages) which are substantially the same as the configurations described in the embodiments. The invention includes configurations in which portions not essential to the configurations described in the embodiments are substituted. The invention includes configurations in which configurations with the same operational advantages as the configurations described in the embodiments or the same objectives can be achieved. The invention includes configurations in which known technologies are added to the configurations described in the embodiments.

The entire disclosure of Japanese Patent Application No. 2015-095501, filed May 8, 2015 is expressly incorporated by reference herein.