DE3912497A1 - SIMULTANEOUS ENERGY AND DATA RETURN TRANSFER OVER LOOSE TRANSFORMERAL COUPLING - Google Patents

Abstract

A loosely coupled transformer or rotary transformer L1, L2, via which measuring electronics, e.g. on a moving part of a vehicle, are supplied with energy, is loaded by the measuring electronics via a switch S at a rate f2 which is a sub-multiple of the energy supply frequency f1. This periodic loading is phase modulated when the level of a binary data signal to be transmitted by the measuring electronics changes. The modulated signal Umod is transferred back to the primary side of the transformer and for the recovery of the data, is demodulated by multiplication with a periodic signal UH at the frequency f2. The resulting signal, after averaging, is supplied to a comparator at the output of which the data signal is available again. Instead of employing a fixed rate f2, a pseudo-statistical signal stored in a ROM may be used. <IMAGE>

Description

 The invention relates to a method for the transmission of Data for use in particular in motor vehicles.

In applied measurement technology, there is often the task of difficult to access objects to obtain measurement data. As Examples are measuring objects in rotating parts or also in the human body.

In many cases, energy is supplied for such Systems over a more or less loose transformative Coupling in the LF range (up to 200 kHz, for example), each according to the distance between the transmitting and receiving coils geometrical boundary conditions and energy consumption the sensor electronics is given.

Difficult and cumbersome is the current one technical status the retransfer of the by the  Measurement data obtained from sensors. One possibility is the use of the high-frequency range, the data transmission takes place through radiation of electromagnetic waves.

The other option is to use the same Frequency range as for energy transmission, i.e. data transmission through an alternating magnetic field. Indeed is the power returned from the sensor electronics a data carrier frequency somehow modulated with the data usually so low that filtering out the low data signal amplitude from the energy signal amplitude is very difficult.

Often, therefore, for the time of data transmission disruptive transformer energy transmission switched off and the measuring electronics from a short-term energy storage, for example, a capacitor.

The invention has for its object a data transmission method specify the existing transmission problems eliminated.

The object is achieved by the method according to claim 1. Embodiments of the invention are part of subclaims.  

The invention relates to a method for simultaneous Transfer of electrical energy in the direction of operating electronics and data in the other direction. The advantages lie on the one hand in the interference immunity of the Data transmission and on the other hand in that for data retransmission practically no additional energy is required becomes.

The invention is explained in more detail with reference to figures. It shows

Fig. 1, the synchronous data retransmission by activating the electronic load with a half power frequency,

Fig. 2 shows the voltage curve,

Fig. 3 shows the data retransmission by switching on the electronic load with a synchronous pseudo-statistical noise.

The transmitter coil L ₁ is fed from the AC voltage source U ₁ with the frequency f ₁. The coupling flux Φ _k passing through the two coils L ₁ and L ₂ induces the voltage U ₂ at L ₂, which can be increased by the resonance capacitor C _Res if necessary.

If the electronic switch S is closed, the filter capacitor C _{s is} charged to the DC voltage U _S in cycles of the frequency f ₁ via the diode D. The following electronics are supplied with the current I _E from this DC voltage.

In this electronics a flip-flop is now available, which converts the frequency f ₁ of the voltage U ₂ into a rectangular signal U _{f 2} with the frequency f ₂ = f ₁ / 2.

f ₂ is supplied to a terminal of the antivalence (or equivalence) gate serving as a modulator. The digital, serial data signal Data generated and to be transmitted by the measuring electronics is connected to the other input of the modulator. The baud rate of data is significantly lower than the frequency f ₂ = f ₁ / 2.

The modulator has the function of a data-controlled converter / inverter. The logic output signal U _{MOD of} the modulator is either equal to U _{f 2} or the same, depending on whether Data = low or Data = high applies. U _MOD is therefore rectangular with the frequency f ₂ = f ½ / 2, but in this signal level change of data a phase jump of + 180 ° or -180 ° occurs.

With _MOD  now becomes the switchS controlled. The filter capacitor C. _s  is not in time with the front of the counter pending frequencyf₁, but only in time with the frequencyf₂ =f½ loaded. When data level changes this periodic reloading undergoes a phase change.

The coil L ₂ or the resonant circuit L ₂, C _Res is thus only taken in cycles of f ₂ = f ₁ / 2 and also because of the diode D only with the positive half-waves of U ₂, current or energy.

This current draw has the result that every second positive half-wave of U ₂ has a dip.

Depending on the size of the transformer coupling, this signal curve is transferred to the primary coil L ₁, that is, in U _{L 1} , the drop in amplitude can also be seen, albeit in a weakened form. The signal curve according to FIG. 2 results.

The Fourier decomposition of U _{L 1} results in addition to the fundamental wave with the frequency f ₁, the data transmission frequency f ₁ / 2 and their harmonics.

For the recovery of the data only the fundamental wave is the Data transmission frequency

U _x = Û _x cos 2 π f ₁ / 2 t

and their phase relationship in relation to the supply voltage

U ₁ = Û ₁ cos 2 π f ₁ t

of interest.

If at the times t ₁ and t ₂ the signal Data to be transmitted changes its level, the phase relationship between U _x and U ₁ also changes abruptly, which in turn is synonymous with a change of sign of Û _x .

Now it applies

Data = low Û _x <0

Data = high Û _x <0.

To demodulate the data, the auxiliary voltage is first obtained again from U ₁ by simple frequency division

U _H = Û _H cos 2 π f ₁ / 2 t

with an independent and constant amplitude Û _H of Û ₁. (In principle, a square wave voltage of the same frequency is also possible.) U _H is fundamentally phase-locked to U ₁ and also has basically the same frequency as the U _x to be detected, namely exactly f ₁ / 2.

The demodulation is now achieved by electronically multiplying U _{L 1,} including the U _x contained therein, by the auxiliary voltage U _H and then carrying out an averaging over time (for example with a low pass). The demodulated signal is obtained

As can be seen, only the portion in U _{L 1} that has the same frequency as U _H , namely only U _x , contributes to the mean value.

Is the showing of Û _H constant, so if e.g. B. applies

Û _H <0

so ultimately follows

Û _x <0 = < U _DEM <0 = <Data = low

Û _x <0 = < U _DEM <0 = <Data = high.

Data is then behind a subsequent comparator immediately available.

The lower the baud rate in relation to the frequency f ₂ = f ₁ / 2, the slower the averaging can be made and the more narrow-band and interference-free the data transmission is.

Another decisive advantage of the procedure lies in in that no additional data transmission Transmission energy is needed, but it results from the special type of load modulation that only the one to be operated Electronics themselves consume energy.

A more refined variant of data transmission arises when the opening and closing of the switch S on the sensor electronics side is not controlled with f 1/2, but with a pseudo statistical signal in a grid of f 1/2 ( FIG. 3). The pseudo-statistical signal is stored in the sensor electronics in a fixed value data memory (ROM).

The 8-bit word is an example

W _Stat = 10011010

accepted. The sequence of zeros and ones is chosen arbitrarily.

If Data = high, the switch is activated in the rhythm of the non-inverted W _Stat , if Data = low, the switch is activated in the rhythm of the inverted signal

operated.

The drop in amplitude in U _{L 1} is now corresponding.

For demodulation, the multiplier no longer has to be driven with f ½ / 2, but with the same pseudo-statistical signal W _Stat , which is also used for modulation in the sensor electronics.

A certain effort is to find the correct phase position for U _H = W _Stat , so that U _Dem also converges. However, this search algorithm is easy to implement with intelligent control.

The outstanding advantage of using a pseudo-statistical signal as a modulation carrier results in insensitivity to discrete Interference frequencies.

Possible applications for the method according to the invention arise, for example, in motor vehicles at Checking the tire pressure, the possibility of one Locking system with identification card or transmission for signals from the steering wheel. But also the data transfer other on moving or rotating Partially provided sensors are conceivable.

Claims (5)

1. A method for synchronous data transmission, in particular from fixed or moving parts in motor vehicles, characterized in that a loosely coupled transformer or rotary transformer, via which the energy supply to the measuring electronics to be operated, is loaded by the measuring electronics in rhythm with a divider factor of the energy frequency, and this periodic load undergoes a phase change with respect to the energy signal when the level of the binary data signal to be transmitted is transferred, the load is transferred to the supply voltage on the primary side of the transformer and is multiplied again by a periodic signal of the same divisor factor of the energy frequency in order to recover the data, after which the result of the multiplication is fed to a comparator after averaging, at whose output the data signal is again available. 2. The method according to claim 1, characterized in that the load with any division factor, for example with 1/2, 1/4 or 1/8 of the energy frequency, preferably with half the energy frequency.   3. The method according to claim 1 or 2, characterized in that the load is rhythmic to the energy signal or its divisor factors synchronous pseudo-statistical Noise occurs, its binary sequence as a fixed value on both the primary and the Secondary side is stored in a memory component. 4. The method according to claim 1 or 2, characterized in that frequency division is done by flip-flops becomes. 5. The method according to any one of claims 1 to 4, characterized characterized in that the load is not caused by the measuring electronics, but through an additional load resistance he follows.