Communication Module

Abstract

To provide a communication module that can achieve an oscillation frequency with high accuracy even when an oscillation circuit without a temperature compensation function is used.SOLUTION: A communication module is provided, on a substrate, with: a communication unit that performs data communication with an external device via an antenna; a vibrator; an oscillation circuit that outputs an electric signal at an oscillation frequency according to a cycle of vibration by the vibrator; a temperature detection unit that detects a temperature around the vibrator; and a correction unit that corrects the oscillation frequency on the basis of the temperature detected by the temperature detection unit. On one or more layers among a plurality of layers constituting the substrate, a conductor pattern in an area including a position corresponding to a position where the vibrator and the temperature detection unit are located is disposed independently of other conductor patterns.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a communication module. [Background technology]

[0002] Conventionally, communication devices such as mobile phones include a communication module for performing data communication with an external device. The communication module includes an oscillator circuit that outputs an electrical signal at an oscillation frequency corresponding to the period of oscillation of a predetermined oscillator such as a quartz oscillator.

[0003] Generally, a vibrator has a temperature characteristic in which the period of vibration changes with temperature. Although there are oscillation circuits having a temperature compensation function based on the temperature characteristic of such a vibrator, they have a drawback in that they are expensive.

[0004] On the other hand, even in an oscillator circuit that does not have a temperature compensation function, there is a technology that can stabilize the oscillation frequency of the oscillator circuit even if the temperature of the resonator changes by using the temperature detection results from a temperature detection unit such as a thermistor. Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned conventional technology, when an oscillator circuit without a temperature compensation function is used, the temperature detection result by the temperature detection unit may differ from the temperature of the vibrator, so there is room for improvement in terms of the accuracy of the oscillation frequency of the oscillator circuit.

[0006] Therefore, the present invention has been made in consideration of the above circumstances, and has an object to provide a communications module that can achieve a highly accurate oscillation frequency even when using an oscillation circuit without a temperature compensation function. [Means for solving the problem]

[0007] The communication module of the embodiment includes a communication unit that performs data communication with an external device via an antenna, a vibrator, an oscillation circuit that outputs an electrical signal at an oscillation frequency corresponding to the period of oscillation by the vibrator, a temperature detection unit that detects the temperature around the vibrator, and a correction unit that corrects the oscillation frequency based on the temperature detected by the temperature detection unit, which are provided on a substrate, and in one or more of the multiple layers constituting the substrate, a conductor pattern in an area including positions corresponding to the positions of the vibrator and the temperature detection unit is arranged independently from other conductor patterns. Effect of the Invention

[0008] According to the present invention, it is possible to provide a communications module that can achieve a highly accurate oscillation frequency even when an oscillation circuit without a temperature compensation function is used. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a communication module according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing the temperature characteristics of a quartz crystal unit. [Diagram 3] FIG. 3 is a diagram showing a configuration of a circuit group that generates an electric signal using a crystal oscillator and a thermistor in the communication module of the first embodiment. [Figure 4] FIG. 4 is a diagram showing a mounting state of the communication module according to the first embodiment. [Diagram 5] FIG. 5 is a diagram showing a first layer of the communication module of FIG. [Figure 6] FIG. 6 is a diagram showing a second layer of the communication module of FIG. [Figure 7] FIG. 7 is a diagram showing a third layer of the communication module of FIG. [Figure 8] FIG. 8 is a diagram showing a fourth layer of the communication module of FIG. [Figure 9] FIG. 9 is a diagram showing a fifth layer of the communication module of FIG. [Figure 10]FIG. 10 is a diagram showing a sixth layer of the communication module of FIG. [Figure 11] FIG. 11 is a diagram illustrating a schematic configuration of a communication module according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a communication module according to an embodiment will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiment.

[0011] First, in order to facilitate understanding of the communication module of the embodiment, the conventional technology will be described again. Currently, LTE (Long Term Evolution) Cat-M1, Cat-NB1, etc. are being developed as wireless communication technologies for IoT (Internet of Things). In other words, application to IoT utilizing the LTE infrastructure of existing mobile phones is being promoted.

[0012] For example, in the case of reading gas meters, water meters, and the like, meter reading has traditionally been done manually, but progress is being made in making it smarter by automatically reading meters and notifying meter reading data via communication.

[0013] As gas and water meters become increasingly smarter, the fact that up until now the meters have been read by humans means that the devices have not been electrically wired, which has been an obstacle to making them smarter. There is therefore a demand for long-term operation using batteries that do not require electrical wiring.

[0014] Therefore, in the above-mentioned LTE Cat-M1 and Cat-NB1 standards, e-DRX, which extends the standby operation from 1.28 seconds for conventional mobile phones, has been standardized by 3GPP (Generation Partnership Project). Currently, the specifications allow for a long standby time of up to 43 minutes.

[0015] However, to achieve such long-term standby, the terminal device operates an independent timer during standby, and the accuracy of the timer operation is directly linked to the accuracy of standby for incoming calls. Therefore, if the accuracy of the timer operation is poor, the standby operation must be extended in order to synchronize the standby operation with the base station, which leads to increased power consumption.

[0016] In other words, improving the accuracy of timer operation is important as one of the factors for reducing the power consumption of terminal devices. And to improve the accuracy of timer operation, a highly accurate oscillation frequency is required by the oscillator circuit.

[0017] As described above, since an oscillator circuit having a temperature compensation function is expensive, there is a great need to use an oscillator circuit without a temperature compensation function. Therefore, in a communication module of a terminal device, it is required to realize a highly accurate oscillation frequency even when an oscillator circuit without a temperature compensation function is used. Such a communication module will be described below.

[0018] (First embodiment) First, a communication module 1 according to the first embodiment will be described. Fig. 1 is a diagram showing a schematic configuration of a communication module 1 according to the first embodiment. The communication module 1 is provided in a communication device such as a mobile phone, and performs data communication with an external device.

[0019] The communication module 1 mainly comprises a memory IC (Integrated Circuit) 2, a communication IC 3, an RF (Radio Frequency) circuit 4, a group of power supply chip components 5, a high-frequency oscillation circuit 6, a crystal unit 7, a thermistor 8, and a module substrate 10. The memory IC 2, the communication IC 3, the RF circuit 4, the group of power supply chip components 5, the high-frequency oscillation circuit 6, the crystal unit 7, and the thermistor 8 are mounted on the module substrate 10.

[0020] The memory IC2 is an IC for storing data and stores various data. The memory IC2 is realized by using, for example, a random access memory (RAM) or a read only memory (ROM).

[0021] The communication IC 3 is an IC for performing processing for communication with an external device, and includes a timer circuit 31 for measuring time. The communication IC 3 controls the RF circuit 4 based on an electrical signal output from the high-frequency oscillation circuit 6, thereby communicating with the external device.

[0022] The RF circuit 4 communicates with an external device via the antenna 100 based on a command from the communication IC 3. The RF circuit 4 may include one or more ICs, or may not include an IC. The communication IC 3 and the RF circuit 4 are an example of a communication unit that communicates data with an external device via the antenna 100.

[0023] The high-frequency oscillator circuit 6 is a circuit that outputs an electrical signal at a high-frequency oscillation frequency. The high-frequency oscillator circuit 6 is realized, for example, by a TCXO (Temperature Compensated Crystal Oscillator). A TCXO is a crystal oscillator that incorporates a temperature compensation circuit that has the opposite temperature characteristics to those of a crystal unit, and provides good temperature characteristics over a wide temperature range.

[0024] The power supply chip components 5 are a group of chip components that generate required output power from input power.

[0025] The crystal oscillator 7 is an oscillator that vibrates at a predetermined period due to the piezoelectric effect of crystal. The crystal oscillator 7 is selected to have a lower oscillation frequency than the high-frequency oscillation circuit 6. The oscillation frequency of the crystal oscillator 7 is, for example, 32.768 kHz. The crystal oscillator 7 is an example of an oscillator.

[0026] FIG. 2 is a diagram showing the temperature characteristics of the crystal unit 7. FIG. 2 shows the temperature characteristics of a tuning fork-type crystal unit 7 with an oscillation frequency of 32.768 kHz. In FIG. 2, the horizontal axis shows the temperature of the crystal unit 7, and the vertical axis shows the frequency deviation (the degree of change in frequency when the frequency at 20° C. is used as a reference). According to the example shown in FIG. 2, it can be seen that the oscillation frequency of the crystal unit 7 decreases as the temperature of the crystal unit 7 decreases from 20° C., and decreases as the temperature of the crystal unit 7 increases from 20° C. Note that the temperature characteristics of the crystal unit 7 shown in FIG. 2 are just an example. The temperature characteristics of the crystal unit 7 are not limited to the example shown in FIG. 2.

[0027] The thermistor 8 is disposed near the crystal oscillator 7, and outputs a detection signal corresponding to the temperature around the crystal oscillator 7. The thermistor 8 is an example of a temperature detection unit that detects the temperature around the oscillator.

[0028] The circuit group that generates an electric signal using the crystal oscillator 7 and thermistor 8 is provided at a position separated from the arrangement positions of the crystal oscillator 7 and thermistor 8. Here, as an example, the circuit group that generates an electric signal using the crystal oscillator 7 and thermistor 8 is included in the RF circuit 4. FIG. 3 is a diagram showing an example of the configuration of the circuit group that generates an electric signal using the crystal oscillator 7 and thermistor 8 in the communication module 1 of the first embodiment. As shown in FIG. 3, the RF circuit 4 includes a temperature detection circuit 41, a storage element 42, a compensation signal generation circuit 43, an oscillation circuit 44, a variable capacitance diode 45, and a capacitor 46.

[0029] The oscillator circuit 44 generates an electrical signal having a frequency corresponding to the oscillation frequency of the crystal oscillator 7. The electrical signal generated by the oscillator circuit 44 is output from an output terminal P via a capacitor 46.

[0030] One of the two terminals of the variable capacitance diode 45, more precisely the cathode terminal, is electrically connected to the oscillation circuit 44. When the capacitance of the variable capacitance diode 45 changes, the resonant frequency of the oscillation circuit 44 changes, thereby adjusting the frequency of the electrical signal output by the oscillation circuit 44. The compensation signal generating circuit 43 uses the thermistor 8, the temperature detection circuit 41, and the memory element 42 to control the capacitance of the variable capacitance diode 45 so that the frequency of the electrical signal output by the oscillation circuit 44 is constant.

[0031] More specifically, the temperature detection circuit 41 detects the temperature based on the detection signal from the thermistor 8 and outputs a temperature signal. The storage element 42 is composed of, for example, a PROM (Programmable Read Only Memory) and stores temperature compensation information. The storage element 42 outputs a signal according to the temperature based on the temperature signal input from the temperature detection circuit 41 and the stored temperature compensation information. The compensation signal generation circuit 43 generates a voltage according to the signal input from the storage element 42 as a compensation signal, and applies the generated voltage between two terminals of the variable capacitance diode 45. Here, the temperature compensation information indicates a voltage value for maintaining the capacitance of the variable capacitance diode 45 at a capacitance required to compensate for the frequency deviation of the crystal resonator 7 as illustrated in FIG. 2. Therefore, the compensation signal generation circuit 43 can control the capacitance of the variable capacitance diode 45 so that the frequency of the electrical signal output by the oscillation circuit 44 is constant regardless of the temperature. The compensation signal generation circuit 43 is an example of a correction unit that corrects the oscillation frequency based on the temperature detected by the temperature detection circuit 41.

[0032] The electrical signal output from the output terminal P is used, for example, in a timer circuit 31 in the communication IC 3. As a result, by using an electrical signal based on the low-frequency crystal oscillator 7 in the timer circuit 31 in the communication IC 3, energy savings can be achieved compared to using an electrical signal based on the high-frequency oscillator circuit 6.

[0033] In conventional designs, the thermistor is placed as close as possible to the crystal unit to minimize the temperature difference between the thermistor and the crystal unit. In addition, the compensation signal generation circuit performs frequency correction based on the inverse function of the temperature detection result from the thermistor, taking into account the temperature characteristics of the crystal unit shown in Figure 2, thereby stabilizing the oscillation frequency.

[0034] Furthermore, in conventional designs, when designing the surface and inner layers of the module substrate of a communication module, signal interference and other issues are taken into consideration, and wiring and GND (ground) patterns are arranged with shielding from other signal wiring in mind. However, no design has been done to thermally isolate the area containing the crystal unit and thermistor, or to intentionally give such an area heat capacity, in order to minimize the temperature difference between the thermistor and the crystal unit.

[0035] Therefore, in the communication module 1 of the first embodiment, the regions including the crystal unit 7 and thermistor 8 are thermally isolated to prevent a temperature difference between the crystal unit 7 and thermistor 8 from occurring, so that the conductor pattern in the region including the positions corresponding to the positions of the crystal unit 7 and thermistor 8 is isolated from other conductor patterns in one or more layers out of the multiple layers constituting the module substrate 10. This point will be described in detail below with reference to Figs. 4 to 10.

[0036] Fig. 4 is a diagram showing a mounting state of the communication module 1 of the first embodiment. Figs. 5 to 10 are diagrams showing the first to sixth layers of the communication module 1 of Fig. 4. In Figs. 5 to 9, an area AR indicates an area where the crystal oscillator 7 and thermistor 8 are arranged. In other words, the area AR indicates an area including positions corresponding to the positions where the crystal oscillator 7 and thermistor 8 are present.

[0037] As shown in Fig. 4, the crystal unit 7 and thermistor 8 are disposed in close proximity to each other. Furthermore, as shown in Figs. 6 to 9, the conductor patterns on the module substrate 10 are disposed so that the conductor pattern in the region AR is isolated from other conductor patterns. The other conductor patterns include, for example, a conductor pattern related to the memory IC 2, a conductor pattern related to the communication IC 3, a conductor pattern related to the RF circuit 4, a conductor pattern related to the power supply chip component group 5, and a conductor pattern related to the high-frequency oscillator circuit 6.

[0038] 5, a crystal unit mounting terminal 71 and a thermistor mounting terminal 81 are arranged in an area AR of the module substrate first layer 10-1. A memory IC 2, a communication IC 3, an RF circuit 4, a group of power supply chip components 5, and a high-frequency oscillator circuit 6 are arranged in an area other than the area AR of the module substrate first layer 10-1. The area in which the memory IC 2, the communication IC 3, the RF circuit 4, the group of power supply chip components 5, and the high-frequency oscillator circuit 6 are arranged is referred to as an other circuit area 20. In the other circuit area 20, terminals on which the memory IC 2, the communication IC 3, the RF circuit 4, the group of power supply chip components 5, and the high-frequency oscillator circuit 6 are mounted are appropriately arranged.

[0039] In the module substrate second layer 10-2 shown in FIG. 6, the quartz crystal resonator wiring 72 and thermistor wiring 82 are provided in the region AR as the conductor patterns of the region AR. The conductor patterns related to the memory IC 2, the conductor patterns related to the communication IC 3, the conductor patterns related to the RF circuit 4, the conductor patterns related to the power supply chip component group 5, and the conductor patterns related to the high-frequency oscillator circuit 6 are arranged in the other circuit region 20. In the region AR, none of the conductor patterns related to the memory IC 2, the conductor patterns related to the communication IC 3, the conductor patterns related to the RF circuit 4, the conductor patterns related to the power supply chip component group 5, and the conductor patterns related to the high-frequency oscillator circuit 6 are arranged. That is, in the module substrate second layer 10-2, the conductor patterns of the region AR are arranged so as to be independent from the other conductor patterns. Similarly, in the module substrate third layer 10-3 shown in FIG. 7, the module substrate fourth layer 10-4 shown in FIG. 8, and the module substrate fifth layer 10-5 shown in FIG. 9, the conductor patterns of the region AR are arranged so as to be independent from the other conductor patterns.

[0040] Note that one or more external connection terminals 30, which are terminals for connecting the communication module 1 to other devices, are arranged on the sixth layer 10-6 of the module substrate shown in Fig. 9. In the example shown in Fig. 9, a total of 30 external connection terminals 30 are arranged in 5 rows and 6 columns.

[0041] 6 to 9, in the module substrate second layer 10-2 to the module substrate fifth layer 10-5, the region AR is surrounded by the conductor pattern D. This increases the heat capacity of the region AR, which makes it possible to prevent a temperature difference between the crystal resonator 7 and thermistor 8. As shown in FIG. 9, in the module substrate fifth layer 10-5, the conductor pattern D is formed along the outer periphery of the crystal resonator wiring 72 and thermistor wiring 82 at the positions where the crystal resonator wiring 72 and thermistor wiring 82 are provided. This prevents the conductor pattern D from crossing either the crystal resonator wiring 72 or the thermistor wiring 82. As shown in FIG. 5 and FIG. 10, the conductor pattern D is not provided in the module substrate first layer 10-1 and the module substrate sixth layer 10-6.

[0042] In addition, since the crystal unit 7 is a low-frequency oscillator, it does not require a ground connection and has no ground terminal. Therefore, as shown in Figures 5 to 9, there is no need to place a solid ground in the area AR, and one is not placed therein. This makes the area AR even more thermally independent.

[0043] Furthermore, as shown in FIG. 9, by arranging the crystal oscillator wiring 72 and thermistor wiring 82 on the lower layer, the fifth module substrate layer 10-5, the area AR becomes even more thermally independent.

[0044] In this way, according to the communication module 1 of the first embodiment, the conductor pattern on the module substrate 10 is arranged so that the area AR including the quartz crystal oscillator 7 and thermistor 8 is thermally independent, thereby preventing the occurrence of a temperature difference between the quartz crystal oscillator 7 and thermistor 8, and achieving a highly accurate oscillation frequency even when using an oscillator circuit 44 without a temperature compensation function.

[0045] Therefore, the manufacturing cost of the communications module 1 can be reduced compared to when an oscillator circuit with a temperature compensation function is used.

[0046] Moreover, by surrounding the region AR with the conductor pattern D to increase the heat capacity, the occurrence of a temperature difference between the crystal resonator 7 and thermistor 8 can be further prevented.

[0047] Second embodiment Next, a communication module 1 according to a second embodiment will be described. Descriptions of matters similar to those in the first embodiment will be omitted as appropriate. Fig. 11 is a diagram showing a schematic configuration of the communication module 1 according to the second embodiment.

[0048] In the second embodiment, the crystal oscillator 7 and thermistor 8 are integrally formed as a molded member 40 by molding with resin.

[0049] Thus, according to the communication module 1 of the second embodiment, the quartz oscillator 7 and thermistor 8 are integrally constructed as a molded member 40 by molding with resin, thereby making it possible to further thermally isolate the quartz oscillator 7 and thermistor 8 from the surroundings and increase the heat capacity of the region AR compared to the first embodiment.

[0050] Therefore, it is possible to more effectively prevent the occurrence of a temperature difference between crystal resonator 7 and thermistor 8 not only due to temperature changes caused by heat generation from the various members on module substrate 10, but also due to changes in the outside air temperature.

[0051] Third embodiment Next, a communication module 1 according to a third embodiment will be described. Descriptions of the same matters as those in the first embodiment will be omitted as appropriate. In the third embodiment, a heating element such as a heater is provided near the crystal oscillator 7 and the thermistor 8.

[0052] The temperatures of the crystal oscillator 7 and thermistor 8 are maintained at a temperature higher than the upper limit of the temperature in the environment in which the communication module 1 is used.

[0053] In this way, according to the communication module 1 of the third embodiment, by providing a heating element near the crystal oscillator 7 and thermistor 8, the occurrence of a temperature difference between the crystal oscillator 7 and thermistor 8 can be further prevented.

[0054] In that case, for example, the detection result by the thermistor 8 may be used for temperature control.

[0055] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the invention and its equivalents described in the claims.

[0056] For example, in each of the above-described embodiments, the case of the crystal oscillator 7 is described as the target for stabilizing the oscillation frequency, but this is not limited thereto, and the present invention may be applied to a high-frequency oscillation circuit 6 that does not have a temperature compensation function. [Explanation of symbols]

[0057] 1...communication module, 2...memory IC, 3...communication IC, 4...RF circuit, 5...power supply chip component group, 6...high frequency oscillation circuit, 7...quartz crystal unit, 8...thermistor, 10...module substrate, 20...other circuit area, 30...external connection terminal, 31...timer circuit, 40...molded member, 41...temperature detection circuit, 42...memory element, 43...compensation signal generating circuit, 44...oscillator circuit, 45...variable capacitance diode, 46...capacitor, 71...quartz crystal unit mounting terminal, 72...quartz crystal unit wiring, 81...thermistor mounting terminal, 82...thermistor wiring, 100...antenna

Claims

1. A communication unit that performs data communication with an external device via an antenna; A vibrator; an oscillation circuit that outputs an electrical signal at an oscillation frequency corresponding to a period of oscillation by the oscillator; A temperature detection unit that detects a temperature around the vibrator; a correction unit that corrects the oscillation frequency based on the temperature detected by the temperature detection unit, the correction unit being provided on a substrate; A communication module, wherein the multiple layers constituting the substrate include a first layer having wiring extending from a first region including a position corresponding to the position where the vibrator and the temperature detection unit are present to a second region different from the first region, and one or more second layers having no wiring extending from the first region to the second region, and in the one or more second layers, a first conductor pattern arranged inside the first region is arranged independently from a second conductor pattern arranged outside the first region.

2. The second conductor pattern includes a third conductor pattern, The communication module according to claim 1 , wherein in one or more of the second layers, the first region is surrounded by the third conductor pattern.

3. The communication module according to claim 1 , wherein the first region is not provided with a solid ground.

4. The communication module according to claim 1 , wherein the vibrator and the temperature detection section are integrally formed by molding.

5. The communication module according to claim 1 , wherein a heating element is provided near the vibrator and the temperature detection unit.

6. The communication module according to claim 1 , wherein the oscillator is a quartz crystal oscillator.

7. The communication module according to claim 1 , wherein the temperature detection unit is a thermistor.

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