Device and method for radio transmission of local measurements of physical values, in particular by means of quasi-Gaussian PPM pulses
By combining the RC filter and SAW resonator in a pulse generation device driven by a low clock speed microcontroller, PPM pulses that comply with international standards are generated, and the problem that pulses do not comply with spurious emission regulations in the prior art is solved, and the problem of pulses not meeting spurious emission regulations is realized. Low power and low cost solutions.
Patent Information
- Application Number
- CN202380037401.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-05-04
- Filing Date
- 2023-05-02
- Publication Date
- 2024-12-13
AI Technical Summary
Existing PPM pulse generation techniques are not in compliance with spurious emission regulations in some countries and require high clock speed microcontrollers to increase power consumption and complexity for pulse shaping.
By using a low clock speed microcontroller in a pulse generation device driven by a microcontroller, combined with an RC filter and a SAW resonator, PPM pulses with a duration of several microseconds in the frequency band allowed by a short-range device are generated, using multiple PPM pulse pairs are used to encode the measured values and generate quasi-Gaussian-shaped pulses using an RC filter to reduce spurious emissions.
It realizes the generation of PPM pulses that meet international standards under low power consumption and low production costs, reducing stray emissions, and is suitable for physical devices in IoT networks.
Smart Images
Figure CN119136998A_ABST
Abstract
Description
[0001] The invention relates to a device and a method for the radio transmission of local measurements of physical values, in particular for the radio transmission of such measurements by means of quasi-Gaussian PPM pulses. The values of the locally performed measurements that are transmitted may be values of pressure, temperature, humidity, deformation, vibration, etc., collected by suitable sensors on a structure that rotates, oscillates or vibrates, for example. A specific but not exclusive use of the invention is vehicle telemetry, for example using the device on a tire in order to transmit by radio the tire internal pressure (tire pressure monitoring system TPMS) or other physical values or parameters measured on the tire or on a wheel containing the tire. However, the invention is not limited to the field of vehicles or the field of tires, and the invention is applicable in any context in which it is necessary to transmit locally performed measurements of some physical values or parameters by radio with low power consumption or over short distances.
[0002] It is known in the art that devices for transmitting measurement results of physical values, such as temperature, pressure, humidity, deformation, etc., are capable of converting such measurement results into data strings which are then transmitted via radio.
[0003] In order to significantly reduce the power consumption of these transmission devices, a transmitter device is known from US Pat. No. 10,284,120, which comprises a microcontroller configured to receive a signal related to at least one measured value and to control a pulse generator so that the pulse generator generates a corresponding pulse position modulation or PPM signal, which is then transmitted via radio. The pulse generator of the known solution comprises an oscillator and a power amplifier for amplifying the pulses from the output of the oscillator and transmitting the PPM signal. The microcontroller is configured to activate only the oscillator during a first time period for each pulse of the PPM signal to be generated, and then also to activate only the amplifier during a second time period following the first time period, and to deactivate both the oscillator and the amplifier at the end of the second time period.
[0004] One disadvantage of the solution known from US Pat. No. 10,284,120 is that pulses lasting a few microseconds generated in the manner described above may not comply with regulations of certain countries regarding spurious emissions, such as provided in the ETSI EN 300 220-1 and / or CFR 47 FCC part 15.231 standards.
[0005] To overcome this problem, a microcontroller can be used which is suitable for shaping the pulses to be transmitted by means of digital filters so that the pulses have the desired frequency behavior, i.e. any out-of-band peaks are below a certain threshold in dBm. However, in order to perform these operations, the microcontroller should have hardware with sufficient computing power, in particular with a speed of at least 100 MHz, as is currently the case in the DSPs of microcontrollers used in the field of mobile phones. However, this solution will increase the power consumption and in any case involve an increase in complexity.
[0006] It is an object of the present invention to provide a device and a method for radio transmission of PPM pulses which are able to improve the background art in one or more of the above aspects.
[0007] Within the scope of this aim, the invention has as its object to generate PPM pulses with a duration of a few microseconds in one of the (free) frequency bands allowed for Short Range Devices (SRDs), for example the ISM band or more generally one of the SRD bands, such as those around 434 MHz, 315 MHz, 868 MHz, 915 MHz, 2.4 GHz or 4.8 GHz, in order to reduce spurious emissions compared to the background art while maintaining the advantages of the ultra-low power consumption of the above-mentioned background art.
[0008] Another object of the invention is to design an RF transmission device suitable for use in a physical device in an IoT (Internet of Things) network and having in particular a small form factor, ultra-low power consumption and low production cost.
[0009] Yet another object of the present invention is to avoid microcontrollers with high clock speeds, especially clock speeds above 3 MHz-16 MHz, for PPM pulse generation.
[0010] An important object of the present invention is to overcome the disadvantages of the background art in a way that replaces any existing solutions.
[0011] This aim and these and other objects which will become more apparent hereinafter are achieved by a device according to claim 1 , optionally provided with one or more of the features of the dependent claims.
[0012] The aim and objects of the invention are also achieved by a method according to claim 9, optionally provided with one or more features of the dependent claims.
[0013] Further features and advantages of the invention will become more apparent from the description of a preferred but non-exclusive embodiment of the device and method according to the invention, illustrated by way of non-limiting example in the accompanying drawings, in which: Figure 1is a block diagram of a transmission device according to the present invention; Figure 2 is a more detailed block diagram of the pulse generating device of the device shown above; Figure 3 yes Figure 1 A detailed circuit diagram of a pulse generating device; Figure 4 The MOD1 and MOD2 drive signals are plotted as well as the Figure 3 the time behavior of the corresponding voltage generated on the capacitor at the input terminal of the corresponding transistor; Figure 5 Drawn in Figure 3 an RF pulse at an output of a pulse generating device; Figure 6 is a flow chart of a method according to the present invention; Figure 7 yes Figure 3 A legend of example values of components of the circuit; Figure 8 can be used as in the second embodiment Figure 3 A view of an oscillator that is an alternative to the oscillator used in; Fig. 9 yes Figure 8 A legend of example values for the components of the oscillator.
[0014] With reference to the cited figures, a device for radio transmission of PPM signals according to the invention, in particular for telemetry applications, is generally indicated by reference numeral 10 and comprises a microcontroller 15 and pulse generating means 33 connected to the microcontroller 15 so as to be driven by it. Advantageously, the transmission device 10 is a short-range device powered by a power source 20, for example a battery or an energy harvesting source.
[0015] The microcontroller 15 is adapted to receive in an input one or more detection signals representing one or more measured values of one or more physical values. Furthermore, the microcontroller 15 is adapted to drive the pulse generating means 33 such that the pulse generating means generates a pulse position modulated (PPM) signal comprising in coded form information corresponding to the measured values received by the microcontroller 15 via the detection signals.
[0016] The detection signal originates from a detection device 25 which is connected or connectable to the microcontroller 15 and is suitable for detecting one or more measurements of a certain physical value (e.g., one or more of pressure, temperature, acceleration, vibration, voltage, etc.) and generating a detection signal corresponding to the value of these measurements. The detection device 25 may essentially consist of at least one transducer (“DM” in the figure) for each physical value to be measured. The transducer DM may be connected to a suitable input of the microcontroller 15 and may be a sensor selected from the group comprising, for example, a pressure sensor, a temperature sensor, a vibration sensor, an accelerometer, a magnetometer, a strain gauge, an inductive sensor, a voltage or current detector, etc.
[0017] The detection device 25 and the optional RFID tag 30 of the transmission device 10 may optionally be powered by the same microcontroller 15 .
[0018] The pulse generating means 33 is connected at the output end to at least one antenna 50 via an optional impedance matching stage 51, so as to transmit the PPM signal generated by the generating means 33 by radio, so that the PPM signal is received by a remote receiver via radio. For example, the remote receiver (not shown) can be a remote receiver described in PCT application number WO 2012 / 150565 A2. The remote receiver can optionally be at a short distance from the transmission device 10, for example on the same vehicle on which one or more transducers DM are installed.
[0019] The PPM signal is a pulse signal ("PPM pulse"), which is known per se and is the result of a PPM modulation of a radio frequency ("RF") carrier. In the case of the present invention, the RF carrier is preferably selected in one of the free frequency bands for short-range devices (e.g. ISM). In the embodiment shown, this frequency is substantially 434.35 MHz, but it is clear that by appropriately assigning values to the electronic components of the circuits shown in detail herein, it is possible to have any carrier frequency among those available for short-range devices.
[0020] The PPM signal generated and transmitted by the transmission device according to the present invention is formed by at least one frame including a plurality of PPM pulse pairs, and the plurality of PPM pulse pairs encode a measured value or a sequence of measured values, such as values of pressure, temperature, deformation, voltage, acceleration, speed, current, etc. The first pulse in each pair ("trigger pulse") is generated periodically over time, for example, every S1 microseconds (where S1 is a fixed value preferably between 200 and 500, such as 400). In contrast, the second pulse in each pair ("data pulse") is at a variable distance relative to the first pulse based on the binary value to be encoded, within a window located at n·S2 microseconds after the first pulse, where n·S2 < S1 and "n" is an integer associated with the corresponding predetermined binary value. The distance between the first pulse and the second pulse can be between 30 microseconds and 120 microseconds, for example, between 50 microseconds and 90 microseconds, while the duration of each pulse is fixed and can be a few microseconds, for example, between 1 microsecond and 5 microseconds.
[0021] The message transmitted with one frame can be a 64-bit message, composed of 34 PPM pulses and having a duration of less than 6 milliseconds, where one PPM pulse pair can be used to identify the start of the frame, and the remaining 16 PPM pulse pairs contain the data items to be transmitted.
[0022] As an alternative, the PPM signal generated and transmitted by the transmission device according to the present invention can be provided with single pulses instead of pulse pairs, where each pulse of the PPM signal is a trigger pulse for a data pulse, and the data pulse follows the trigger pulse.
[0023] The transmission device 10 performs PPM modulation on the detection signal received by the microcontroller 15. In particular, a word corresponding to the measured value of at least one physical value, such as a bit sequence corresponding to the encoding of the measured value, is modulated (PPM). Then, downstream of the microcontroller, modulation is performed at the carrier frequency RF for radio transmission of the PPM signal as subsequently described in the present invention.
[0024] The microcontroller 15 can be a microcontroller with a low clock speed (e.g., approximately 1 MHz) and is programmed to generate a drive signal for the generating device at the output, which will be better described below. For example, the microcontroller 15 can be one of those microcontrollers in the series commercially known as MSP430 produced by Texas Instruments, such as MSP430F2012 or MSP430G2332.
[0025] The pulse generating device 33 comprises an oscillator 35, the output of which is connected to the input of a power amplifier ("PA") 40, so that the PA 40 amplifies the radio frequency signal ("RF signal") emitted by the oscillator 35 and generates at the output a PPM pulse to be transmitted via radio. The gain of the PA 40 may be between 10 and 20.
[0026] The oscillator 35 may have an RC stage 31 or 31' at the input. Figure 2 It is schematically represented by resistor R0 and capacitor C0.
[0027] Both the oscillator 35 and the power amplifier 40 are driven by a microcontroller 15, which is programmed to generate at its respective outputs a first signal MOD1 for driving the power amplifier 40 and a second signal MOD2 for driving the oscillator 35. The signals MOD1 and MOD2 consist essentially of rectangular voltage or current pulses, i.e. signals that exhibit only low (null) values and high values, wherein the low and high values are preferably independent of temperature, i.e. do not vary significantly within the operating temperature range of the transmission device 10, which may be between -25°C and +85°C or possibly between -40°C and +125°C. Each PPM pulse to be transmitted corresponds to a single rectangular pulse of the first signal MOD1 and a single rectangular pulse of the second signal MOD2 applied as described below.
[0028] exist Figure 2 and in more detail in Figure 3 In the embodiment shown in , the signals MOD1 and MOD2 consist of rectangular voltage pulses having a low value equal to zero volts and a high value which may be substantially equal to a DC power supply voltage +Vcc (e.g., 3 V or a value between 2.4 V and 3.6 V) of the transmission device 10. In the example shown, a CR lithium battery may be used to generate the voltage +Vcc.
[0029] Advantageously, the microcontroller 15 is connected to the input of the power amplifier 40 by inserting an RC filter 41 which is connected to the input of the power amplifier 40. Figure 21 is schematically represented by a resistor R101 (connected to the output MOD1 of the microcontroller 15) and a capacitor C101, which is connected to ground and to the base resistor R102 of the BJT transistor of the power amplifier 40. The rising and falling edges of the signal MOD1 applied to the input of the amplifier 40, which would otherwise be step-shaped, are slowed down between the output MOD1 of the microcontroller 15 and the input of the power amplifier 40 by the RC filter 41 as a low-pass filter, wherein the time constant is substantially defined by the resistor and capacitor of the low-pass filter 41, i.e. by the product of their respective resistance and capacitance values.
[0030] refer to Figure 3 In the embodiment shown in , which provides more details about the general structure of the transmission device 10 than the previous figures, the oscillator 35 of the pulse generation device 33 comprises a Colpitts oscillator in a "common base" configuration and coupled to a SAW (surface acoustic wave) resonator X1, which allows said oscillator 35 to achieve a stable frequency value Fo (equal to 434.35 MHz in the example shown). The oscillator 35 is an oscillator of a type known per se, for example from US Pat. No. 8,134,416 B2, incorporated herein by reference.
[0031] The oscillator 35 may comprise a single RF transistor Q1 which may be a BJT of the npn type and which, in the particular example shown, may have a cut-off frequency of 14 GHz at 40 mA. The switching on / off of the oscillator 35 is respectively effected by means of the high / low level of the voltage signal MOD2 arriving from the corresponding output MOD2 of the microcontroller 15 and applied to the base of the transistor Q1 via the base resistor R1. Advantageously, the same base of the transistor Q1 is connected to ground by means of a capacitor C4 which, together with the resistor R1, substantially defines a time constant R1·C4 suitable for determining the start-up time (T2) of the oscillator 35, i.e. the rate at which the oscillation amplitude rises to a stable value.
[0032] The SAW resonator X1 is connected between ground and the collector of the transistor Q1 of the oscillator 35, with an inductor-resistor stage formed by an inductor L2 and a resistor R2 inserted in series.
[0033] The oscillation frequency Fo is essentially determined by the inductor L1 (which is connected between the collector of transistor Q1 and the power supply +Vcc, possibly with the insertion of a low-resistance resistor R8), the capacitor C1 (which is between the collector and emitter of Q1) and the series capacitors C2 and C3 connected to ground. At the instant when the Colpitts oscillator is activated by the rising edge of the second drive signal MOD2, the (SAW) resonator X1 is a pure capacitor and the oscillation starts at a frequency slightly higher than the target frequency. Once the resonator X1 starts to oscillate (mechanically), the resonator X1 is equivalent to an LCR circuit with the effect of dragging the Colpitts oscillator to the target frequency. This frequency corresponds to the parallel resonant frequency of the resonator X1 and is about 150KHz to 250KHz higher than the nominal series resonant frequency of the resonator X1.
[0034] As Figure 3 As an alternative to the specific embodiment of the oscillator 35 shown in the device of FIG. 1 , a Hartley type oscillator, such as Figure 8 In this case, the Hartley oscillator is preferably in a "common emitter" configuration and the phase reversal that allows the oscillation is performed by an inductor L1' connected between the bipolar transistor Q1 (which may be Figure 3 and Figure 7 between the collector and base of the same npn transistor in FIG. 1 ), in parallel with series capacitors C1' and C2'.
[0035] Figure 8 The oscillator is stabilized at the oscillation frequency by a SAW resonator X1 connected between ground and the collector of transistor Q1, in which an inductor-resistor stage formed by a parallel connection between an inductor L3' and a resistor R3' is inserted in series.
[0036] Figure 8 The oscillator preferably uses an inductor L1' in parallel with a capacitive voltage divider C1'-C2' having a tap connected to ground, rather than using a tapped inductor in parallel with a single capacitor as is usually the case. In addition, Figure 8 The oscillator may also include a leveling inductor or choke L2' (which has a high reactance at the oscillation frequency) and a capacitor C5' to bring the RF signal to the base of the transistor Q1, thereby blocking the DC component. The transistor Q1 of the oscillator may include respective bypass capacitors C4' and C6' towards the DC power supply Vcc and ground to block RF noise, and in the case of the emitter capacitor C6', increase the gain of the amplifier by virtue of being connected in parallel with the resistor R2'.
[0037] The RC series group formed by resistor R5' and capacitor C7' transfers the signal from the output of the oscillator (the tap on the collector of Q1) to the input of the power amplifier 40, adapting it to the corresponding input impedance.
[0038] The power amplifier 40 is preferably adapted to achieve a peak power of +13 dBm or +14 dBm (25 mW conducted power at 50Ω) for the RF pulses of the oscillator 35 .
[0039] The power amplifier 40 advantageously comprises a single transistor Q2, which is preferably a bipolar junction transistor (BJT) of the npn type. In the case shown, the transistor Q2 operates at a collector current (Ic) at which the cut-off frequency is similar to that of the transistor Q1 of the oscillator 35, in particular, the cut-off frequency is still above 13 GHz, with Ic=60 mA and a power gain of more than 20 dB at 500 MHz.
[0040] As an alternative, the power amplifier 40 may be provided by means of any known type of RF power amplifier which can be amplitude modulated.However, for reasons of cost and low power consumption, a single transistor embodiment is preferred.
[0041] The transmission device 10 according to the present invention may be provided with an impedance matching stage 51 between the collector of the transistor Q2 and the RF output terminal (i.e., the impedance of the antenna 50), and the impedance matching stage 51 may include an inductor L3 between the collector and the power supply +Vcc, a capacitor C7 between the collector and the ground, and a capacitor C8 between the collector and the RF output terminal ( Figure 7 ). A reactance stage may also be provided to further attenuate harmonics, and in the example shown is formed by an inductor L4 (which is connected to the collector of transistor Q2 via capacitor C8) and two grounded capacitors C9 and C10 connected to the terminals of inductor L4.
[0042] Obviously, Figure 7 and Fig. 9 The values and specifications of the components shown in the figure are exemplified for a case where the carrier frequency is in a frequency band around 434 MHz. However, it is easy for a person skilled in the art to change Figure 3 or Figure 8 The values of the circuits, transistors, microchips and specific SAW resonators are adjusted to bring the carrier frequency into another frequency band (e.g., 315 MHz, 868 MHz, 915 MHz, 2.4 GHz or 4.8 GHz) that can be used for short-range devices.
[0043] According to one aspect of the invention, an RC filter 41 is provided between the output of the signal MOD1 of the microcontroller 15 and the input of the power amplifier 40 (which in the embodiment shown is the base of the transistor Q2). Since in the preferred embodiment the signal MOD1 for driving the amplifier 40 is a voltage signal, the base of the transistor Q2 is provided with a base resistor R6 so that current can be supplied to the base by the signal.
[0044] exist Figure 3 In a detailed embodiment of the invention, the RC filter 41 is inserted between the output terminal MOD1 and the base resistor R6 and comprises a resistor R5 between the terminals of the output terminal MOD1 and the base resistor R6 and a capacitor C12 connected to ground at the terminals. The peak level of the PPM pulse generated at the output of the amplifier 40 is substantially determined by the series resistors R5 and R6.
[0045] The RC filter 41 formed by R5 and C12 is essentially a low-pass filter which, by virtue of the relative time arrangement of the signals MOD1 and MOD2 explained below, allows to provide at the output of the amplifier 40 a PPM pulse having a quasi-Gaussian shape over time, i.e. an approximation of a Gaussian curve, which is free of spurious harmonics having a significant power level as far as frequency is concerned, i.e. in the frequency band between 25 MHz and 6 GHz, has no spurious harmonics having a power level greater than -36 dBm (for frequencies below 1 GHz) or -30 dBm (for frequencies above 1 GHz).
[0046] According to the invention, for each PPM pulse 200 to be generated at the output of the generating means 33, the microcontroller 15 drives the oscillator 35 and the power amplifier 40 as follows: - the microcontroller 15 keeps the oscillator 35 and the power amplifier 40 switched off (step 301 ), i.e. the microcontroller 15 keeps both the signal MOD1 for driving the power amplifier 40 and the signal MOD2 for driving the oscillator 35 at a low value (i.e. zero) in order to minimize the power consumption in the time between one PPM pulse and the next PPM pulse and between one message and the next message; - When there is a PPM pulse to be transmitted (step 302), the microcontroller 15 activates the oscillator 35 (step 303) only for a period T_OSC (also referred to herein as "oscillation time interval") equal to the sum of T1+T2+T3, i.e. the microcontroller 15 brings the signal MOD2 to a high value and keeps it high for the entire interval T_OSC and then returns it to zero. At the input of the oscillator 35, the current signal is defined by the RC stage 31 or 31 ' (e.g. Figure 3 In the case of Figure 8In the case of R1'·C3', the time constant rises;
[0047] - after a first time period T2 from the beginning of said interval T_OSC (i.e. from the rising edge of the rectangular pulse of the signal MOD2) (step 304), the microcontroller 15 also activates the power amplifier 40, but only for a second time period T1, such that the sum of the first and second time periods (T2+T1) is less than the oscillation time interval T_OSC (step 305). In other words, after the first time period T2, the microcontroller 15 brings the signal MOD1 to a high value and keeps it high exclusively for said second time period T1, and then returns it to zero. The time constant (R1·C4 or R1'·C3') defined by the RC stage 31 at the input of the oscillator 35 makes it possible to reach a substantially overdrive condition of the power amplifier 40 halfway along the second time period T1;
[0048] - After the second time period T1 has elapsed (step 306), the microcontroller 15 only deactivates the power amplifier 40 (step 307), and before the oscillation time interval T_OSC expires, that is, within a third time period T3 (non-zero), only keeps the oscillator 35 fully active (that is, only keeps the signal MOD2 at a high level), and after the third time period T3 (step 308), the microcontroller 15 deactivates the oscillator 35, causing the signal MOD2 to reach a low value (step 309), that is, to reach zero.
[0049] The values of T1, T2, T3 are advantageously selected as follows.
[0050] The first time period T2 or “pre-pulse time” is preferably the shortest time period required for oscillations in the output of the oscillator 35 to stabilize after the oscillator 35 is powered on by the drive signal MOD2 , but it may be shorter.
[0051] Preferably, T2 has a value between 0.5 microseconds and 5 microseconds. The frequency of the oscillation is preferably an RF frequency in one of the so-called free frequency bands, such as a frequency of the ISM band or the SRD band. In the embodiment shown, such a frequency is between 433.05 MHz and 434.79 MHz, for example 434.35 MHz.
[0052] The second time period T1 or "pulse time" or "activation time" of the amplifier 40 corresponds substantially to the duration of a single PPM pulse to be transmitted at radio frequency (i.e., the pulse width at -3 dB), and may be between 1 microsecond and 5 microseconds. A duration of T1 between 1.8 microseconds and 2.5 microseconds is preferred in order to reduce the risk of non-compliance with OBW tests of international standards such as those initially mentioned herein.
[0053] The third time period T3 or "post-pulse time" is selected so as to amplify the signal in the output of the oscillator 35 decreasingly over time, and is preferably between 0.5 microseconds and 5 microseconds. In particular, the RC filter 41 allows slowing down the falling edge of the drive signal MOD1 at the input of the amplifier 40, which would otherwise be step-shaped, thereby applying a gradually decaying amplification to the RF signal generated by the oscillator 35, which remains active throughout the third time period T3.
[0054] While the time constant R1·C4 or R1′·C3′ of the RC stage 31 or 31′ at the input of the oscillator 35 may be selected so as to substantially determine the decay time of the falling edge 204 of the PPM pulse, the time constant (R101·C101 or R5·C12) of the RC filter 41 at the input of the amplifier 40 is selected not only to determine the rise time of the rising edge 202 of the PPM pulse, but also to eliminate or in any case attenuate spurious emissions, which in the case of the present invention will substantially be harmonics.
[0055] In fact, it has surprisingly been found that this gradually decreasing amplification of the signal in the output of the still active oscillator 35 and obtained during the third time period T3 by means of the RC filter 41 allows smoothing of the falling edge of the PPM pulse 200 at the output of the amplifier 40, resulting in a substantially angular point-free knee 203 on the falling edge. The rising edge 202 of the PPM pulse is also substantially free of angular points or slope discontinuities.
[0056] In summary, the PPM pulse 200 at the output of the generating means 33 is therefore proven to be quasi-Gaussian or pseudo-Gaussian, i.e. suitable for avoiding the generation of out-of-band frequency peaks exceeding the threshold power levels (-30 dBm or -36 dBm) typically provided in the standards, i.e. avoiding spurious emissions and in this respect satisfying the international standards initially mentioned in the text.
[0057] If instead the third time period T3 is zero as described in the background art represented by the above-mentioned patent US 10,284,120, i.e. if the signals MOD1 and MOD2 are both brought to a low level at the same time and without any RC filter 41, the region 203 will have a concavity change, i.e. the power level of the spurious emission will increase.
[0058] The third time period T3 between the falling edge of the signal MOD1 for driving the amplifier 40 and the falling edge of the signal MOD2 for driving the oscillator 35 can have a value between 0.5 microseconds and 5 microseconds, that is, substantially equal to or lower than the time constant of the above-mentioned RC filter 41 placed between the output terminal MOD1 of the microcontroller 15 and the input terminal of the power amplifier 40.
[0059] Referring to the RC stage 31 at the input of the oscillator 35 and applying the drive signal MOD2, the resistor R1 (or Figure 2 R0 in ) preferably has a resistance between 1 kΩ and 100 kΩ, while capacitor C4 (or Figure 2 C0 in ) preferably has a capacitance between 22 pF and 2200 pF, so as to define a time constant of the RC stage 31 between 0.5 microseconds and 2 microseconds. Figure 8 The RC stage 31' of the oscillator is set with similar resistance and capacitance values.
[0060] In the RC filter 41, the resistor R5 (or Figure 3 R101 in the example may have a resistance between 1 kΩ and 100 kΩ, while capacitor C12 (or Figure 2 C101 in ) preferably has a capacitance between 100 pF and 10 nF so as to define a time constant of the RC filter 41 between 1 microsecond and 10 microseconds.
[0061] In practice, it has been found that the invention achieves the intended aim and objects.
[0062] The invention thus conceived is susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept; moreover, all the details may be replaced by other technically equivalent elements.
[0063] In practice, the materials used, as well as the possible shapes and dimensions, may be any according to requirements and the state of the art.
[0064] The disclosures in Italian Patent Application No. 102022000009020 from which this application claims priority are incorporated herein by reference.
[0065] In case the technical features mentioned in any claim are followed by reference signs, the sole purpose of including the reference signs is to improve the intelligibility of the claims and accordingly, these reference signs have no limiting effect on the interpretation of each element identified by these reference signs by way of example.
Claims
1. A transmission device (10) for radio transmission of local measurement results of physical values, comprising a microcontroller (15) and a pulse generator (33) connected to the microcontroller (15), the microcontroller (15) being adapted to receive at least one detection signal representing at least one measurement value and to control the pulse generator (33) so that the pulse generator (33) generates at least one PPM signal comprising information corresponding to the at least one measurement value, the transmission device (10) further comprising an antenna (50) for radio transmission of the PPM signal or being connectable to the antenna (50), the pulse generator (33) comprising an oscillator (35) and an input connected to the oscillator (35). The transmission device (10) comprises a power amplifier (40) of the oscillator (35) for amplifying the RF pulses in the output of the oscillator (35) and transmitting the PPM signal based on the selective activation of the oscillator (35) and the power amplifier (40) by a corresponding drive signal with rectangular pulses generated by the microcontroller (15), the transmission device (10) being characterized in that the microcontroller (15) is adapted to activate / deactivate the oscillator (35) and the power amplifier (40) for each PPM pulse (200) of the PPM signal to be generated, so that the oscillator (35) is activated before the activation of the power amplifier (40) and is deactivated after the deactivation of the power amplifier (40), The transmission device (10) is further characterized in that the transmission device (10) comprises a low-pass filter (41) between the microcontroller (15) and the power amplifier (40), the low-pass filter (41) being adapted to slow down the deactivation of the amplifier (40) while the oscillator (35) is still kept active by the corresponding drive signal (MOD2).
2. The transmission device according to claim 1, wherein: The microcontroller (15) is adapted to activate / deactivate the oscillator (35) and the power amplifier (40) according to the following sequence for each PPM pulse (200) of the PPM signal to be generated: activating the oscillator (35) only during an oscillation time interval (T_OSC), After a first time period (T2) from the start of the oscillation time interval (T_OSC), the power amplifier (40) is also activated only during a second time period (T1), such that a sum (T1+T2) of the first time period and the second time period is less than the oscillation time interval (T_OSC), and the amplifier is deactivated at the end of the second time period (T1); During a third time period (T3) after the second time period (T1), the oscillator (35) is activated only until the oscillation time interval (T_OSC) expires, and then the oscillator (35) is deactivated, The low pass filter (41) is adapted to slow down the deactivation of the amplifier (40) during the third time period (T3).
3. The transmission device according to claim 1 or 2, wherein: The microcontroller is suitable for generating the drive signal at its respective output terminals connected to the oscillator and the power amplifier, the drive signal comprising a first signal (MOD1) for driving the power amplifier (40) and a second signal (MOD2) for driving the oscillator (35), the first drive signal (MOD1) being provided by a first output terminal of the microcontroller connected to the power amplifier, and the second drive signal (MOD2) being provided by a second output terminal of the microcontroller connected to the oscillator (35), wherein each rectangular pulse of the first drive signal (MOD1) has a duration equal to the second time period (T1), and each rectangular pulse of the second drive signal (MOD2) has a duration equal to the oscillation time interval (T_OSC).
4. The transmission device according to one or more of the preceding claims, wherein: The first drive signal (MOD1) is provided by a first output terminal of the microcontroller connected to the power amplifier, the power amplifier comprises an input transistor (Q2), and the first output terminal of the microcontroller (15) is connected to an activation terminal of the transistor across the low pass filter.
5. The transmission device according to one or more of the preceding claims, wherein: The second drive signal (MOD2) is provided by a second output of the microcontroller (15) connected to the oscillator (35), the oscillator comprising an input RC stage (31), and the second output of the microcontroller (15) is connected to the oscillator (35) so as to apply the second drive signal (MOD2) to the RC stage.
6. The transmission device according to one or more of claims 2 to 5, wherein: The second time period (T1) is between 1 microsecond and 5 microseconds, more preferably between 1.8 microseconds and 2.5 microseconds.
7. The device according to claim 6, wherein: The first time period and / or the third time period is between 0.5 microseconds and 5 microseconds.
8. The device according to one or more of the preceding claims, wherein: The RC filter (41) has a time constant between 1 microsecond and 10 microseconds.
9. A method for radio transmission of local measurement results of physical values, the method being performed by a transmission device comprising a microcontroller (15), a pulse generator (33) connected to the microcontroller (15), and an antenna (50), the pulse generator comprising an oscillator (35) and a power amplifier (40) connected to the oscillator (35) at its input in order to amplify RF pulses at the output of the oscillator (35), the method being characterized in that the method comprises the following steps: Receiving in the microcontroller (15) at least one detection signal representing at least one locally detected measurement value; PPM modulates at least one information item contained in the at least one detection signal and generates, for each PPM pulse of the PPM signal to be generated using the pulse generator, a first rectangular pulse (MOD1) having a duration T1 and being supplied to the power amplifier so that the power amplifier remains active only during the duration T1, and a second rectangular pulse (MOD2) having a duration T_OSC greater than T1 and being supplied to the oscillator (35) so that the oscillator (35) remains active during the duration T_OSC, wherein for each PPM pulse (200), the oscillator (35) and the power amplifier (40) are activated / deactivated such that the oscillator (35) is activated before activation of the power amplifier (40) and is deactivated after deactivation of the power amplifier (40), The first rectangular pulse (MOD1) is provided to the power amplifier (40) after passing through a low-pass filter, so as to slow down the deactivation of the power amplifier (40).
10. The method according to the preceding claim, wherein: For each PPM pulse (200), the oscillator (35) and the power amplifier (40) are activated / deactivated according to the following sequence: applying the second rectangular pulse to the oscillator (35) so that the oscillator (35) remains active only for the duration T_OSC, applying the first rectangular pulse to the power amplifier (40) after a first time period T2 from the start of the second rectangular pulse (MOD2) so that the power amplifier (40) remains active only for the duration T1, such that T1+T2 is less than the duration T_OSC; During a first time period T3 after the duration T1, the oscillator (35) is kept active only until the duration T_OSC expires and then the oscillator (35) is deactivated, Therein, the deactivation of the power amplifier (40) is slowed down during the third time period (T3).
11. The method according to the preceding claim, wherein: The duration T1 is between 1 microsecond and 5 microseconds, more preferably between 1.8 microseconds and 2.5 microseconds.
12. The method according to one or more of claims 10 and 11, wherein: The first time period and / or the third time period is between 0.5 microseconds and 5 microseconds.