Voltage-controlled oscillator, wireless sensor and wireless sensor network

Abstract

The invention relates to the technical field of sensors, and provides a voltage-controlled oscillator, a wireless sensor and a wireless sensor network, and the voltage-controlled oscillator comprises a current conversion module, a first current mirror, a second current mirror, an oscillation generation module and a sensing module. The current conversion module converts an input reference voltage into a reference current; the sensing module outputs a first voltage and a second voltage, and at least one of the first voltage and the second voltage is a variable voltage changing along with the change of a sensing target; the two current mirrors respectively generate a first mirror current and a second mirror current according to the reference current; the oscillation generation module generates a high-level signal according to the first voltage and the first mirror current, generates a low-level signal according to the second voltage and the second mirror current, and determines the duration of the high-level signal and the low-level signal according to the variable voltage. According to the voltage-controlled oscillator, the sensing module is integrated, and an independent sensor for sensing the change of a sensing target in an environment is not needed, so that the energy consumption of a wireless sensor node is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular, to a voltage-controlled oscillator, a wireless sensor, and a wireless sensor network. Background Art

[0002] Since the energy of a self-powered wireless sensor network comes from the environment, the energy is very weak, so the power consumption requirements for wireless sensor nodes are very stringent, for example: less than 1 mW. As Figure 1 shown, currently, the temperature information of a temperature sensor is characterized by an analog signal output by an acquisition circuit, and the analog signal also needs to be processed by a digital circuit to be converted into a temperature value, that is, the analog signal is converted into a digital signal by an analog-to-digital converter (ADC), and then the temperature value is read through digital processing. Among them, the acquisition circuit, ADC, and digital circuit in the temperature sensor all increase the power consumption. Summary of the Invention

[0003] The present invention provides a voltage-controlled oscillator, a wireless sensor, and a wireless sensor network to solve the technical problem of high power consumption of wireless sensor nodes in the prior art.

[0004] The present invention provides a voltage-controlled oscillator, including: a current conversion module, a first current mirror, a second current mirror, an oscillation generation module, and an induction module.

[0005] The current conversion module is used to convert an input reference voltage into a reference current.

[0006] A first voltage is output from a first voltage output end of the induction module, and a second voltage is output from a second voltage output end of the induction module. At least one of the first voltage and the second voltage is a variable voltage that changes with the induction target.

[0007] The first current mirror is used to generate a first mirror current according to the reference current.

[0008] The second current mirror is used to generate a second mirror current according to the reference current.

[0009] The oscillation generation module is used to generate a high-level signal according to the first voltage and the first mirror current, generate a low-level signal according to the second voltage and the second mirror current, and determine the duration of the high-level signal and the low-level signal according to the variable voltage.

[0010] A voltage-controlled oscillator provided according to the present invention, wherein the current conversion module includes: an operational amplifier, a first NMOS transistor, and a reference resistor. The positive input terminal of the operational amplifier is used to input the reference voltage. The negative input terminal of the operational amplifier is connected to the source of the first NMOS transistor and the first end of the reference resistor. The second end of the reference resistor is grounded. The output terminal of the operational amplifier is connected to the gate of the first NMOS transistor. The drain of the first NMOS transistor is connected to the control side of the first current mirror.

[0011] A voltage-controlled oscillator provided according to the present invention further includes: a third current mirror; the third current mirror is used to generate a third mirror current according to the reference current, and the second current mirror is used to generate a second mirror current according to the third mirror current.

[0012] The first current mirror includes: a first PMOS transistor and a second PMOS transistor. The first PMOS transistor and the second PMOS transistor form a current mirror structure. The first PMOS transistor is located on the control side of the first current mirror, and the second PMOS transistor is located on the mirror side of the first current mirror.

[0013] The second current mirror includes: a second NMOS transistor and a third NMOS transistor. The second NMOS transistor and the third NMOS transistor form a current mirror structure. The second NMOS transistor is located on the control side of the second current mirror, and the third NMOS transistor is located on the mirror side of the second current mirror.

[0014] The third current mirror includes: the first PMOS transistor and a third PMOS transistor. The first PMOS transistor and the third PMOS transistor form a current mirror structure. The first PMOS transistor is located on the control side of the third current mirror, and the third PMOS transistor is located on the mirror side of the third current mirror. And the control side of the second current mirror is connected to the mirror side of the third current mirror.

[0015] A voltage-controlled oscillator provided according to the present invention, wherein the oscillation generation module includes: a comparator, a variable capacitor, a first switch, a second switch, a third switch, and a fourth switch.

[0016] The first end of the variable capacitor is connected to the negative input terminal of the comparator. The second end of the variable capacitor is grounded. And the negative input terminal of the comparator is connected to the mirror side of the first current mirror through the first switch and to the mirror side of the second current mirror through the second switch.

[0017] The positive input terminal of the comparator is connected to the first voltage output terminal of the induction module through the third switch and to the second voltage output terminal of the induction module through the fourth switch. And the first voltage is greater than the second voltage.

[0018] The control terminals of the first switch, the second switch, the third switch, and the fourth switch are each connected to the output terminal of the comparator. When the input voltage at the inverting input terminal of the comparator is less than the input voltage at the non-inverting input terminal of the comparator, the output terminal of the comparator outputs a high-level signal, the first switch and the third switch are turned on, and the second switch and the fourth switch are turned off, so as to form a charging branch for connecting the mirror side of the first current mirror to the variable capacitor; when the input voltage at the inverting input terminal of the comparator is greater than the input voltage at the non-inverting input terminal of the comparator, the output terminal of the comparator outputs a low-level signal, the first switch and the third switch are turned off, and the second switch and the fourth switch are turned on, so as to form a discharging branch for connecting the variable capacitor to the mirror side of the second current mirror.

[0019] According to a voltage-controlled oscillator provided by the present invention, the variable capacitor includes: n fixed capacitors and n control switches. The i-th fixed capacitor and the i-th control switch are connected in series to form the i-th capacitor branch. The capacitor branches are connected in parallel. The first ends of the fixed capacitors are the first end of the variable capacitor, and the second ends of the fixed capacitors are the second end of the variable capacitor, where i = 1, 2,..., n, and n is greater than or equal to 2.

[0020] According to a voltage-controlled oscillator provided by the present invention, the control switch includes: a fourth PMOS transistor, a fifth PMOS transistor, a fourth NMOS transistor, and a fifth NMOS transistor.

[0021] The source of the fourth PMOS transistor is connected to the drain of the fourth NMOS transistor, and the drain of the fourth PMOS transistor is connected to the source of the fourth NMOS transistor.

[0022] The sources of the fifth PMOS transistor and the fifth NMOS transistor are both connected to the gate of the fourth NMOS transistor. The drain of the fifth PMOS transistor is connected to the power supply terminal, and the drain of the fifth NMOS transistor is grounded.

[0023] The gates of the fourth PMOS transistor, the fifth PMOS transistor, and the fifth NMOS transistor are connected to form the control terminal of the control switch.

[0024] According to a voltage-controlled oscillator provided by the present invention, the sensing module includes: a first resistor, a second resistor, a third resistor, and a fourth resistor.

[0025] The first resistor and the second resistor are connected in series to form a first voltage output branch. The third resistor and the fourth resistor are connected in series to form a second voltage output branch. The first voltage output branch and the second voltage output branch are connected in parallel, and one end of each is connected to the power supply terminal, and the other end is grounded.

[0026] The connection point of the first resistor and the second resistor on the first voltage output branch is the first voltage output end of the sensing module, and the connection point of the third resistor and the fourth resistor on the second voltage output branch is the second voltage output end of the sensing module.

[0027] At least one of the first resistor, the second resistor, the third resistor, and the fourth resistor is a sensing resistor whose resistance value changes with the change of the sensing target.

[0028] A voltage-controlled oscillator provided by the present invention further includes: a calibration module, and the calibration module is used to output a calibrated reference voltage to the current conversion module.

[0029] The present invention also provides a wireless sensor, including the voltage-controlled oscillator described in any one of the above.

[0030] The present invention also provides a wireless sensor network, including a plurality of the above wireless sensors.

[0031] The voltage-controlled oscillator, wireless sensor, and wireless sensor network provided by the present invention. The voltage-controlled oscillator includes: a current conversion module, a first current mirror, a second current mirror, an oscillation generation module, and a sensing module; the current conversion module is used to convert the input reference voltage into a reference current; the first voltage output end of the sensing module outputs a first voltage, and the second voltage output end outputs a second voltage, and at least one of the first voltage and the second voltage is a variable voltage that changes with the change of the sensing target; the first current mirror is used to generate a first mirror current according to the reference current, and the second current mirror is used to generate a second mirror current according to the reference current; the oscillation generation module is used to generate a high-level signal according to the first voltage and the first mirror current, generate a low-level signal according to the second voltage and the second mirror current, and determine the duration of the high-level signal and the low-level signal according to the variable voltage. The sum of the durations of two adjacent high-level signals and low-level signals is a period, and the period can be converted into a frequency, that is, the oscillation frequency output by the voltage-controlled oscillator can be changed by the change of the sensing target. Since the voltage-controlled oscillator integrates a sensing module for sensing the change of the sensing target in the environment, the change of the sensing target directly sensed by the sensing module can output a corresponding oscillation frequency. When the wireless sensor network is formed, there is no need for a separate sensor for sensing the change of the sensing target in the environment in the wireless sensor node, thereby reducing the energy consumption of the wireless sensor node and improving the integration degree of the wireless sensor node. Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a schematic structural diagram of a wireless sensor node in the prior art.

[0034] Figure 2 It is a schematic circuit diagram of a voltage-controlled oscillator provided by the present invention.

[0035] Figure 3 It is a schematic circuit diagram of a variable capacitor in the circuit of the voltage-controlled oscillator provided by the present invention.

[0036] Figure 4 It is a schematic diagram of the frequency band division of the voltage-controlled oscillator provided by the present invention.

[0037] Figure 5 It is a schematic circuit diagram of a control switch for the variable capacitor in the circuit of the voltage-controlled oscillator provided by the present invention.

[0038] Figure 6 It is a schematic structural diagram of a wireless sensor node provided by the present invention. Detailed implementation manners

[0039] To make the objectives, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present invention belong to the scope of protection of the present invention.

[0040] The voltage-controlled oscillator in the embodiment of the present invention includes: a current conversion module, a first current mirror, a second current mirror, an oscillation generation module, and an induction module.

[0041] The current conversion module is used to convert the input reference voltage into a reference current.

[0042] The first voltage output terminal of the induction module outputs a first voltage, and the second voltage output terminal outputs a second voltage. At least one of the first voltage and the second voltage is a variable voltage that changes with the change of the induction target. Among them, the induction module is used to sense the change of the induction target in the environment. The induction target can be temperature, pressure, brightness, or harmful gases in the environment, etc. When the induction target (such as temperature) changes, the variable voltage will change.

[0043] The first current mirror is configured to generate a first mirror current according to the reference current, and the second current mirror is configured to generate a second mirror current according to the reference current. The function of a current mirror is to copy the current on the control side of the current mirror to the mirror side of the current mirror according to a set ratio, so as to control the magnitude of the current on the mirror side by the current on the control side.

[0044] The oscillation generation module is configured to generate a high-level signal according to the first voltage and the first mirror current, generate a low-level signal according to the second voltage and the second mirror current, and determine the duration of the high-level signal and the low-level signal according to the variable voltage. An adjacent high-level signal and a low-level signal form an oscillation period, thereby forming a square-wave clock signal. The period can be converted into a frequency. Since the variable voltage determines the duration of the high-level signal and the low-level signal, both the oscillation period and the oscillation frequency are related to the variable voltage. Also, since the variable voltage is related to the sensed target, the oscillation frequency of the oscillation generation module is related to the sensed target. That is, a change in the sensed target can change the oscillation frequency output by the voltage-controlled oscillator. Moreover, both the first mirror current and the second mirror current are determined by the reference current, and the reference current is determined by the reference voltage. That is, the oscillation frequency of the voltage-controlled oscillator in this embodiment is affected by the reference voltage and the sensed target. When the input reference voltage is given, a relationship between the oscillation frequency and the sensed target can be established. Therefore, the corresponding sensed target value can be obtained through the output frequency of the voltage-controlled oscillator.

[0045] The voltage-controlled oscillator of this embodiment integrates an induction module for sensing changes in the sensed target in the environment, and can directly output a corresponding oscillation frequency according to the change in the sensed target sensed by the induction module. When forming a wireless sensor network, there is no need for a separate sensor for sensing changes in the sensed target in the environment in the wireless sensor node, thereby reducing the power consumption of the wireless sensor node and improving the integration of the wireless sensor node.

[0046] As Figure 2 shown, in some embodiments, the current conversion module includes: an operational amplifier AMP, a first NMOS transistor NM1, and a reference resistor R. The positive input terminal of the operational amplifier AMP is used to input the reference voltage V REF , the negative input terminal of the operational amplifier AMP is connected to the source of the first NMOS transistor NM1 and the first end of the reference resistor R, the second end of the reference resistor R is grounded (i.e., the GND terminal), the output terminal of the operational amplifier AMP is connected to the gate of the first NMOS transistor NM1, and the drain of the first NMOS transistor NM1 is connected to the control side of the first current mirror.

[0047] Specifically, due to the connection structure of the operational amplifier AMP, the first NMOS transistor NM1, and the reference resistor R, the voltage at the first end of the reference resistor R will be clamped to the reference voltage V REF , such that the reference current I REF flowing through the reference resistor R is inversely proportional to the magnitude of its resistance r, that is, I REF = V REF / r, which also means that the control current on the control side of the first current mirror is I REF . When the reference resistor R is determined and the reference voltage V REF is given, I REF remains unchanged.

[0048] The current conversion module in this embodiment has a simple structure. By using the reference resistor R, the reference voltage V REF is converted into a stable reference current I REF . Moreover, the drain of the first NMOS transistor NM1 is connected to the control side of the first current mirror, such that a stable control current is maintained on the control side of the first current mirror, that is, a stable mirror current is provided to the oscillation generation module. Given the reference voltage V REF , the oscillation frequency generated by the oscillation generation module is only related to the sensed target. Therefore, after networking, the target sensed value of its environment can be determined based on the oscillation frequency uploaded by the wireless sensor node.

[0049] In some embodiments, as Figure 2 shown, the voltage-controlled oscillator further includes: a third current mirror; the third current mirror is configured to generate a third mirror current according to the reference current, and the second current mirror is configured to generate a second mirror current according to the third mirror current.

[0050] The first current mirror includes: a first PMOS transistor PM1 and a second PMOS transistor PM2. The first PMOS transistor PM1 and the second PMOS transistor PM2 form a current mirror structure. The first PMOS transistor PM1 is located on the control side of the first current mirror, and the second PMOS transistor PM2 is located on the mirror side of the first current mirror. Based on the current mirror principle, the second PMOS transistor PM2 will copy the control current flowing through the first PMOS transistor PM1 in proportion (this proportion is determined by the specifications of the two MOS transistors constituting the current mirror, specifically determined by the ratio of the aspect ratios of the lengths and widths of the two MOS transistors constituting the current mirror) to obtain the mirror current flowing through the second PMOS transistor PM2, that is, the first mirror current. Specifically, the source of the first PMOS transistor PM1 is connected to the power supply terminal (i.e., the VDD terminal), and the drain is connected to the drain of the first NMOS transistor NM1, so that the drain of the first NMOS transistor NM1 is connected to the control side of the first current mirror.

[0051] The second current mirror includes: a second NMOS transistor NM2 and a third NMOS transistor NM3. The second NMOS transistor NM2 and the third NMOS transistor NM3 form a current mirror structure. The second NMOS transistor NM2 is located on the control side of the second current mirror, and the third NMOS transistor NM3 is located on the mirror side of the second current mirror. Based on the current mirror principle, the third NMOS transistor NM3 will proportionally copy the control current flowing through the second NMOS transistor NM2 to obtain the mirror current flowing through the third NMOS transistor NM3, that is, the second mirror current.

[0052] The third current mirror includes: the first PMOS transistor PM1 and the third PMOS transistor PM3. The first PMOS transistor PM1 and the third PMOS transistor PM3 form a current mirror structure. The first PMOS transistor PM1 is located on the control side of the third current mirror, and the third PMOS transistor PM3 is located on the mirror side of the third current mirror. And the control side of the second current mirror is connected to the mirror side of the third current mirror. Specifically, the drain of the second NMOS transistor NM2 is connected to the drain of the third PMOS transistor PM3.

[0053] It should be noted that: in the current mirror structure of this embodiment, the second PMOS transistor PM2 can directly copy the current of the first PMOS transistor PM1. However, the current directions of the third NMOS transistor NM3 and the first PMOS transistor PM1 are inconsistent. Therefore, the current of the first PMOS transistor PM1 cannot be directly copied. It is necessary to copy the current by the third PMOS transistor PM3 and then convert it into the current of the second NMOS transistor NM2, so that the current directions of the second NMOS transistor NM2 and the third NMOS transistor NM3 are the same, and then the third NMOS transistor NM3 can copy the current of the second NMOS transistor NM2.

[0054] As Figure 2 shown, in some embodiments, the oscillation generation module includes: a comparator COMP, a variable capacitor C, a first switch K1, a second switch K2, a third switch K3, and a fourth switch K4.

[0055] The first end of the variable capacitor C is connected to the inverting input terminal of the comparator COMP, the second end of the variable capacitor C is grounded, and the inverting input terminal of the comparator COMP is connected to the mirror side of the first current mirror through the first switch K1 and to the mirror side of the second current mirror through the second switch K2. Specifically, the inverting input terminal of the comparator COMP is connected to the drain of the second PMOS transistor PM2 through the first switch K1 and to the drain of the third NMOS transistor NM3 through the second switch K2.

[0056] The non-inverting input terminal of the comparator COMP is connected to the first voltage output terminal of the induction module through the third switch K3 and to the second voltage output terminal of the induction module through the fourth switch K4, and the first voltage VH greater than a second voltage V L .

[0057] Control terminals of the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 are each connected to an output terminal of the comparator COMP. When an input voltage at a non-inverting input terminal of the comparator COMP is less than an input voltage at a positive input terminal of the comparator COMP, the output terminal of the comparator COMP outputs a high-level signal, the first switch K1 and the third switch K3 are turned on, and the second switch K2 and the fourth switch K4 are turned off, so as to form a charging branch in which a mirror side of a first current mirror is connected to a variable capacitor C; when the input voltage at the non-inverting input terminal of the comparator COMP is greater than the input voltage at the positive input terminal of the comparator COMP, the output terminal of the comparator COMP outputs a low-level signal, the first switch K1 and the third switch K3 are turned off, and the second switch K2 and the fourth switch K4 are turned on, so as to form a discharging branch in which the variable capacitor C is connected to a mirror side of a second current mirror.

[0058] Specifically, when the output terminal of the comparator COMP outputs a high-level signal CK+, the first switch K1 and the third switch K3 are turned on. At this time, a first voltage output terminal of the sensing module outputs a first voltage V H to the positive input terminal of the comparator COMP. Since the first switch K1 is turned on, a first mirror current of the first current mirror charges the variable capacitor C, and a voltage V C at a first end of the variable capacitor C gradually increases, that is, the voltage at the non-inverting input terminal of the comparator COMP gradually increases, and the comparator COMP continuously outputs the high-level signal CK+. When the voltage at the non-inverting input terminal of the comparator COMP increases to exceed the first voltage V H , the comparator COMP outputs a low-level signal CK-, the second switch K2 and the fourth switch K4 are turned on, and the first switch K1 and the third switch K3 are turned off. At this time, a second voltage output terminal of the sensing module outputs a second voltage V L to the positive input terminal of the comparator COMP. Since the first switch K1 is turned off and the second switch K2 is turned on, the variable capacitor C discharges through the mirror side of the second current mirror, and the voltage V C at the first end of the variable capacitor C gradually decreases, that is, the voltage at the non-inverting input terminal of the comparator COMP gradually decreases, and the comparator COMP continuously outputs the low-level signal CK-. When the voltage at the non-inverting input terminal of the comparator COMP decreases to exceed the second voltage V L , the comparator COMP outputs a high-level signal CK+ again, and thus it cycles repeatedly, thereby generating oscillation of a square-wave clock signal.

[0059] Among them, the discharge current is the second mirror current, and the magnitude of the discharge current replicates the magnitude of the current on the control side of the second current mirror in proportion. The current on the control side of the second current mirror is the third mirror current on the mirror side of the third current mirror.

[0060] As Figure 3 shown, in some embodiments, the variable capacitor C includes: n fixed capacitors C01 to C0n and n control switches T01 to T0n. The i-th fixed capacitor and the i-th control switch are connected in series to form the i-th capacitor branch. The capacitor branches are connected in parallel. The first ends of the fixed capacitors are the first end of the variable capacitor, and the second ends of the fixed capacitors are the second end of the variable capacitor, where i = 1, 2, …, n, n is greater than or equal to 2, and the capacitance values of each fixed capacitor can be the same or different. In this embodiment, by turning on different fixed capacitors or the control switches corresponding to different numbers of fixed capacitors, the variable capacitor C in different voltage-controlled oscillators in the wireless sensor network has different capacitance values, so that different voltage-controlled oscillators have different frequency band ranges. As Figure 4 shown, it can be seen from the coordinate diagram of the oscillation frequency and the oscillation amplitude that when there are m wireless sensors in the wireless sensor network, the variable capacitor C in each wireless sensor takes different capacitance values c j , different capacitance values c j correspond to different frequency band ranges TX_F j , where j = 1, 2, …, m, m is greater than or equal to 2, that is, the different oscillation frequencies output by the voltage-controlled oscillator with the change of the induction target are all within the corresponding frequency band range, so that the host computer in the wireless sensor network can determine which voltage-controlled oscillator sent the frequency according to the received frequency, and thus determine the induction target value in the environment where the voltage-controlled oscillator is located.

[0061] As Figure 5 shown, in some embodiments, the control switch includes: a fourth PMOS transistor PMa, a fifth PMOS transistor PMb, a fourth NMOS transistor NMa, and a fifth NMOS transistor NMb.

[0062] The source of the fourth PMOS transistor PMa is connected to the drain of the fourth NMOS transistor NMa, and the drain of the fourth PMOS transistor PMa is connected to the source of the fourth NMOS transistor NMa.

[0063] The sources of the fifth PMOS transistor PMb and the fifth NMOS transistor NMb are both connected to the gate of the fourth NMOS transistor NMa. The drain of the fifth PMOS transistor PMb is connected to the power supply terminal, and the drain of the fifth NMOS transistor NMb is grounded.

[0064] The gates of the fourth PMOS transistor PMa, the fifth PMOS transistor PMb, and the fifth NMOS transistor N Mb are connected to form the control terminal of the control switch.

[0065] Specifically, Figure 5 In the circuit structure of, the fourth PMOS transistor PMa and the fourth NMOS transistor NMa form a transmission gate, and the fifth PMOS transistor PMb and the fifth NMOS transistor N Mb form an inverter. When the level V CT of the control terminal is low, the nodes 1 and 2 of the transmission gate are conducting, which is equivalent to the control switch being conducting, and the corresponding fixed capacitors are connected in parallel to form a variable capacitor C; when the level V CT of the control terminal is high, the nodes 1 and 2 of the transmission gate are disconnected, which is equivalent to the control switch being disconnected.

[0066] In this embodiment, after the wireless sensor nodes are networked, the V CT of the control switch in the variable capacitor C circuit of the voltage-controlled oscillator in each wireless sensor is controlled by an external signal respectively, so that the variable capacitor C in different voltage-controlled oscillators has different capacitance values.

[0067] As Figure 2 shown, in some embodiments, the sensing module includes: a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4.

[0068] The first resistor R1 and the second resistor R2 are connected in series to form a first voltage output branch, the third resistor R3 and the fourth resistor R4 are connected in series to form a second voltage output branch, the first voltage output branch and the second voltage output branch are connected in parallel, and one end of each is connected to the power supply terminal and the other end is grounded.

[0069] The connection point of the first resistor R1 and the second resistor R2 on the first voltage output branch is the first voltage output terminal of the sensing module, and the connection point of the third resistor R3 and the fourth resistor R4 on the second voltage output branch is the second voltage output terminal of the sensing module.

[0070] At least one of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 is a sensing resistor whose resistance value changes with the sensing target. For the convenience of control, one of the resistors can be selected as the sensing resistor. For example: the second resistor R2 is the sensing resistor. As the sensing target in the environment changes, the second resistor R2 changes, and the first voltage V H changes, and the difference between the first voltage V H and the second voltage V L changes. V C changes from V H to V L or changes from V L to VH The time will also change, that is, the oscillation period and oscillation frequency change with the induction target, so that the induction target value can be determined according to the oscillation frequency.

[0071] The induction target can be temperature, pressure, brightness or harmful gases in the environment. Correspondingly, the second resistor R2 can be a thermistor, a varistor, a photoresistor and a gas sensor.

[0072] Since the resistors and capacitors on the voltage-controlled oscillator chip have at least a plus or minus 15% deviation, this will cause a deviation in the oscillation frequency. Therefore, in some embodiments, the voltage-controlled oscillator further includes: a calibration module, which is configured to output a calibrated reference voltage to the current conversion module, adjust the reference voltage through the calibration module, and at the same time test the deviation between the output oscillation frequency of the oscillator and the target frequency, so as to calibrate the output oscillation frequency of the test oscillator.

[0073] Specifically, as Figure 2 shown, the calibration module can be a digital-to-analog converter (DAC). Input the digital quantity Din, and convert the digital quantity Din into a reference voltage V REF output. The DAC adjusts the accuracy of the reference voltage V REF through the number of bits of the digital quantity Din, that is, one over 2 to the Nth power represents the accuracy of the reference voltage V REF , N represents the number of bits of Din. The more bits, the higher the adjustment accuracy of the reference voltage V REF . And because the reference voltage V REF and the oscillation frequency are linearly proportional, therefore, the accuracy of the oscillation frequency can be calibrated through the number of bits of the digital quantity Din. For example: if it is required that the error of the oscillation frequency does not exceed 1%, then the number of bits of the input digital quantity of the DAC is at least more than 7 bits (1 / 2 7 =1 / 128<1%), and the error of the oscillation frequency will be less than 1%.

[0074] In this embodiment, the reference voltage is calibrated by the calibration module, avoiding the oscillation frequency error caused by the deviation of the resistor and capacitor, making the oscillation frequency output by the voltage-controlled oscillator more accurate, that is, the induction of the induction target in the environment is more accurate.

[0075] The working principle of the voltage-controlled oscillator of the present invention will be described below through a specific embodiment. As Figure 2 shown, in this embodiment, taking the second resistor R2 as a thermistor to detect the environmental temperature as an example: the positive input terminal of the operational amplifier AMP inputs a reference voltage V REF , the output terminal is directly connected to the gate of NM1, and the source of NM1 is fed back to the negative input terminal of the operational amplifier AMP. Based on this connection structure, the voltage at the upper end of the reference resistor R is clamped to V REF, so that the reference current I flowing through the reference resistor R REF is inversely proportional to the resistance value r of the reference resistor R, that is, I REF =V REF / r. I REF The first current mirror structure composed of PM1 and PM3 provides a charging current for the variable capacitor C, and the second current mirror structure composed of NM2 and NM3 provides a discharging current for the variable capacitor C. The comparator COMP generates a clock signal CK, and CK is used as the clock output of this voltage-controlled oscillator. At the same time, it controls the charging and discharging of the variable capacitor C. When the CK signal is the high-level signal CK+, K1 and K3 are closed, the positive input terminal of the comparator COMP is connected to the first voltage V H , the charging branch of the variable capacitor C is turned on, K2 and K4 are turned off, and the discharging branch of the variable capacitor C is turned off. At this time, the variable capacitor C starts to charge, and the voltage V C rises. Until V C exceeds the voltage V H , CK jumps to the low-level signal CK-, K2 and K4 are closed, the positive input terminal of the comparator COMP is connected to the second voltage V L , the discharging branch of the variable capacitor C is turned on, K1 and K2 are turned off, and the charging branch of the variable capacitor C is turned off. At this time, the variable capacitor C starts to discharge, and the voltage V C drops. Until V C is less than V L , CK jumps back to the high-level signal CK+ again. So on and so forth, a square-wave clock signal CK is generated at the output terminal of the comparator COMP, and the frequency of the square-wave clock signal CK is also the oscillation frequency.

[0076] For the convenience of calculation and understanding, the current replication ratios of each current mirror can be designed so that the charging current and discharging current of the variable capacitor C are equal in magnitude, both being I C , for example: the replication ratios of the first current mirror and the third current mirror are M, and the replication ratio of the second current mirror is 1. Therefore, the charging and discharging current I C of the variable capacitor is: I C =M·I REF =M·V REF / r (1).

[0077] The period T and frequency freq of the square-wave clock signal CK are respectively: T=2c(V H -V L ) / I C (2); freq= I C / [2c(V H -V L )] (3).

[0078] Among them, c represents the capacitance value of the variable capacitor. Substituting formula (1) into formula (3), we can get: freq = M·V REF / [2rc(V H -V L )] (4).

[0079] Among them, the first voltage V H and the second voltage V L are respectively: V H = VDD·r2 / (r1 + r2) (5); V L = VDD·r4 / (r3 + r4) (6).

[0080] Among them, r1, r2, r3, and r4 are the resistance values of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 respectively.

[0081] From the above formulas (4) to (6), it can be seen that the oscillation frequency freq is related to V REF , c, r, M, r1, r2, r3, r4, and VDD. After the design of the voltage-controlled oscillator chip is completed, r, M, r1, r3, r4, and VDD are all fixed values. After the networking is completed, the capacitance value c of the variable capacitor C and V REF in each voltage-controlled oscillator are also fixed values. Therefore, this voltage-controlled oscillator can directly output the corresponding oscillation frequency according to the detected environmental temperature, eliminating the temperature sensor in the wireless sensor node, reducing power consumption, and improving the integration of the wireless sensor. Of course, before networking, V REF can be adjusted and determined through the Din input by the DAC to improve the accuracy of the oscillation frequency output by the voltage-controlled oscillator.

[0082] The embodiment of the present invention also provides a wireless sensor, including the voltage-controlled oscillator described in any of the above embodiments. Specifically, as Figure 6 shown, it further includes: a thermoelectric power generation device TEG, an energy management circuit, an energy storage unit, and an antenna. The thermoelectric power generation device TEG supplies electric energy to the voltage-controlled oscillator through the energy management circuit. The excess energy is stored through the energy storage unit. The voltage-controlled oscillator sends the oscillation frequency to the aggregation node in the wireless sensor network through the antenna, and the aggregation node forwards the oscillation frequency to the upper computer. A mapping table of the oscillation frequency and the induction target value is preset in the upper computer, and the induction target value of the wireless sensor node in the environment can be obtained by looking up the table through the oscillation frequency.

[0083] An embodiment of the present invention further provides a wireless sensor network, which includes a plurality of wireless sensors in the above embodiments. Of course, it also includes a sink node connected to the plurality of wireless sensors, and a host computer connected to the sink node.

[0084] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the essence of the above technical solution, or the part that contributes to the prior art, can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it is still possible to modify the technical solutions described in the foregoing embodiments, or to equivalently replace some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A voltage-controlled oscillator, characterized in that, Comprising: A current conversion module, a first current mirror, a second current mirror, an oscillation generation module, and an induction module; The current conversion module is configured to convert an input reference voltage into a reference current; A first voltage is output from a first voltage output terminal of the induction module, and a second voltage is output from a second voltage output terminal of the induction module, and at least one of the first voltage and the second voltage is a variable voltage that varies with the induction target; The first current mirror is configured to generate a first mirror current according to the reference current; The second current mirror is configured to generate a second mirror current according to the reference current; The oscillation generation module is configured to generate a high-level signal according to the first voltage and the first mirror current, generate a low-level signal according to the second voltage and the second mirror current, and determine the duration of the high-level signal and the low-level signal according to the variable voltage.

2. The voltage-controlled oscillator according to claim 1, wherein The current conversion module includes: an operational amplifier, a first NMOS transistor, and a reference resistor. The positive input terminal of the operational amplifier is configured to input the reference voltage. The negative input terminal of the operational amplifier is connected to the source of the first NMOS transistor and the first end of the reference resistor. The second end of the reference resistor is grounded. The output terminal of the operational amplifier is connected to the gate of the first NMOS transistor. The drain of the first NMOS transistor is connected to the control side of the first current mirror.

3. The voltage-controlled oscillator according to claim 1, wherein Further comprising: A third current mirror; The third current mirror is configured to generate a third mirror current according to the reference current, and the second current mirror is configured to generate a second mirror current according to the third mirror current; The first current mirror includes: a first PMOS transistor and a second PMOS transistor. The first PMOS transistor and the second PMOS transistor form a current mirror structure. The first PMOS transistor is located on the control side of the first current mirror, and the second PMOS transistor is located on the mirror side of the first current mirror; The second current mirror includes: a second NMOS transistor and a third NMOS transistor. The second NMOS transistor and the third NMOS transistor form a current mirror structure. The second NMOS transistor is located on the control side of the second current mirror, and the third NMOS transistor is located on the mirror side of the second current mirror; The third current mirror includes: the first PMOS transistor and a third PMOS transistor. The first PMOS transistor and the third PMOS transistor form a current mirror structure. The first PMOS transistor is located on the control side of the third current mirror, and the third PMOS transistor is located on the mirror side of the third current mirror, and the control side of the second current mirror is connected to the mirror side of the third current mirror.

4. The voltage-controlled oscillator according to claim 1, characterized in that The oscillation generation module includes: a comparator, a variable capacitor, a first switch, a second switch, a third switch, and a fourth switch; The first end of the variable capacitor is connected to the negative input terminal of the comparator. The second end of the variable capacitor is grounded. The negative input terminal of the comparator is connected to the mirror side of the first current mirror through the first switch and to the mirror side of the second current mirror through the second switch; The positive input terminal of the comparator is connected to the first voltage output terminal of the induction module through the third switch and to the second voltage output terminal of the induction module through the fourth switch, and the first voltage is greater than the second voltage; The control terminals of the first switch, the second switch, the third switch, and the fourth switch are each connected to the output terminal of the comparator. When the input voltage at the inverting input terminal of the comparator is less than the input voltage at the non-inverting input terminal of the comparator, the output terminal of the comparator outputs a high-level signal, the first switch and the third switch are turned on, and the second switch and the fourth switch are turned off, so as to form a charging branch for connecting the mirror side of the first current mirror to the variable capacitor; when the input voltage at the inverting input terminal of the comparator is greater than the input voltage at the non-inverting input terminal of the comparator, the output terminal of the comparator outputs a low-level signal, the first switch and the third switch are turned off, and the second switch and the fourth switch are turned on, so as to form a discharging branch for connecting the variable capacitor to the mirror side of the second current mirror.

5. The voltage-controlled oscillator according to claim 4, wherein The variable capacitor includes: n fixed capacitors and n control switches. The i-th fixed capacitor and the i-th control switch are connected in series to form the i-th capacitor branch, and the capacitor branches are connected in parallel. The first ends of the fixed capacitors are the first end of the variable capacitor, and the second ends of the fixed capacitors are the second end of the variable capacitor, where i = 1, 2,..., n, and n is greater than or equal to 2.

6. The voltage-controlled oscillator according to claim 5, characterized in that, The control switch includes: a fourth PMOS transistor, a fifth PMOS transistor, a fourth NMOS transistor, and a fifth NMOS transistor; The source of the fourth PMOS transistor is connected to the drain of the fourth NMOS transistor, and the drain of the fourth PMOS transistor is connected to the source of the fourth NMOS transistor; The sources of the fifth PMOS transistor and the fifth NMOS transistor are both connected to the gate of the fourth NMOS transistor. The drain of the fifth PMOS transistor is connected to the power supply terminal, and the drain of the fifth NMOS transistor is grounded; The gates of the fourth PMOS transistor, the fifth PMOS transistor, and the fifth NMOS transistor are connected to form the control terminal of the control switch.

7. The voltage-controlled oscillator according to claim 1, characterized in that The sensing module includes: a first resistor, a second resistor, a third resistor, and a fourth resistor; The first resistor and the second resistor are connected in series to form a first voltage output branch, the third resistor and the fourth resistor are connected in series to form a second voltage output branch, the first voltage output branch and the second voltage output branch are connected in parallel, and one end of each is connected to the power supply terminal and the other end is grounded; The connection point of the first resistor and the second resistor on the first voltage output branch is the first voltage output terminal of the sensing module, and the connection point of the third resistor and the fourth resistor on the second voltage output branch is the second voltage output terminal of the sensing module; At least one of the first resistor, the second resistor, the third resistor, and the fourth resistor is a sensing resistor whose resistance value changes with the sensing target.

8. The voltage-controlled oscillator according to any one of claims 1 to 7, characterized in that It further includes: a calibration module, and the calibration module is used to output a calibrated reference voltage to the current conversion module.

9. A wireless sensor, characterized in that, It includes the voltage-controlled oscillator according to any one of claims 1 to 8.

10. A wireless sensor network, characterized in that, It includes a plurality of wireless sensors as claimed in claim 9.

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