EP1743434A1

EP1743434A1 - Method and device for demodulating

Info

Publication number: EP1743434A1
Application number: EP05706740A
Authority: EP
Inventors: Karl-Heinz Hahn; Jürgen DONAUBAUER; Bernhard Kufner; Karl Krammel; Frank Liesaus; Thomas Fleischer
Original assignee: Conti Temic Microelectronic GmbH
Current assignee: Conti Temic Microelectronic GmbH
Priority date: 2004-04-01
Filing date: 2005-02-05
Publication date: 2007-01-17
Also published as: DE112005000380D2; DE102004043635A1; FR2868625A1; WO2005101676A1

Abstract

The invention relates to a method and device for demodulating a received input signal (E1) containing a modulated up data signal (D). The input signal (E1) is mixed with a comparison signal (V) to form an intermediate frequency signal (ZF1) from which a conditioned intermediate frequency signal (ZF2) is generated. In a control unit (6), the data signal (D) is recovered from the conditioned intermediate frequency signal (ZF2), particularly by sampling the data signal (D). The comparison signal (V) used for mixing and, in particular, also a sampled signal (A1) used for scanning, as well as a transmitted signal (S1, S2) that underlies the input signal (E1) are derived from the clock signal (T) provided for the clock supply of the control unit (6). As a result, only a single clock generator (16) is required.

Description

Method and device for demodulation

The invention relates to a method and a device for demodulating an input signal comprising a modulated data signal according to the preambles of claims 1 and 7, respectively.

In the transmission of sensor data from the place of their detection to an evaluation or KontroUemheit increasingly also wireless (partial) transmission links are used. The data signal of the sensor is modulated on a high-frequency carrier signal and sent out. On the receiver side, the demodulation, ie the recovery of the data signal, is usually carried out by means of a mixer connected to a local oscillator and further electrical units. These demodulation methods and devices are too expensive for some applications. Thus, there is a need for very cost-effective solutions, especially in the automotive industry.

The invention is therefore based on the object to provide a method of the generic type so that it can be implemented inexpensively.

This Aufabe is solved by a method which is designed according to the features of claim 1. By deriving the comparison signal of the mixer from the clock signal necessary for the confusion unit, the otherwise required additional clock generator can be saved. As a result, the method and also a device performing the method can be implemented more cost-effectively. Advantageous embodiments of the method according to the invention will become apparent from the claims dependent of spoke 1.

If according to claim 2, the clock signal is used directly as a comparison signal, unnecessary further measures for deriving the comparison signal, so that a particularly inexpensive method results.

The variant according to claim 3 is characterized by a good suitability for the transmission of sensor data. The fixed phase reference of the individual signals to each other allows a particularly simple demodulation.

In the variant according to claim 4, the demodulation is particularly simple. To recover the data signal, a simple sampling of the processed intermediate frequency signal is used. Otherwise, units commonly needed for demodulation, such as a PLL circuit, are not required.

In the embodiment according to claim 5 signal transit times can be considered and ausgeghchen means of the adjustable time delay. The demodulation method can thus be operated particularly efficiently and error-prone.

The variant according to claim 6 leads to a substantially rectangular waveform of the processed intermediate frequency signal, so that a bit change due to the very steep edges in the following Kontxolleinheit can be particularly easily detected. The invention continues to be based on the abe to specify a device of the generic type so that it can be realized inexpensively.

This object is achieved with a device according to the features of claim 7. Advantageous embodiments of the device according to the invention will become apparent from the dependent of Speech 7 claims. The device according to the invention and its embodiments essentially offer the same advantages that have already been described in connection with the method according to the invention and its variants.

Further features, advantages and details of the invention will become apparent from the following description of Ausführangsbeispielen with reference to the drawing. It shows

1 shows a first embodiment of a device for sensor data transmission and for demodulation of a received input signal,

2 shows timing diagrams of signals occurring in the first embodiment according to FIG. 1,

3 shows a second exemplary embodiment of a device for sensor data transmission and for demodulation of a received input signal, and

Fig. 4 timing diagrams of occurring in the second embodiment of FIG. 3 signals. Corresponding parts are provided in FIGS. 1 to 4 with the same reference numerals.

FIG. 1 shows a first embodiment of a device 1 for data transmission and demodulation in the form of a sensor-transponder system. The device 1 is intended for batterieose Drackabfrage in a tire, not shown in Fig. 1 of a motor vehicle. The device 1 comprises a control unit 2 and a wheel module 3, between which there are wireless connections 4 and 5.

The control unit 2 contains as essential component a control unit 6, which is connected to an output for a low-frequency (= LF) signal by means of a signal conditioning unit 7 and a driver 8 to an LF transmission antenna 9. In addition, the controller 2 includes a

RF (= high frequency) receiving antenna 10, which is connected by means of an input amplifier 11, a mixer 12 and a signal conditioning unit 13 to a sampling input 14 and to a wake-up input 15 of the control unit 6. In addition, the control unit 6 is connected to an external clock generator 16.

The control unit 6 is designed in the example as a micro-processor. Alternatively, however, a design as a micro-controller or as a computer is conceivable. The control unit 6 includes a plurality of sub-assemblies or functional units, some of which are shown in the illustration of FIG. An internal clock unit 17 as well as a decoupler 18 and also a frequency divider 19 are connected to the input of the control unit 6, to which the external clock generator 16 is connected. With a second connection, the frequency consumer 19 is probably brought to a delay element 20 and the low-frequency output, which is connected to the signal conditioning unit 7. The decoupler 18 is guided to an output of the control unit 6, which is connected by means of a connecting line 18 a to a comparison input 20 a of the mixer 12.

The delay gate 20 is connected to an output of the control unit 6. Between this output and a sampling clock input 21 of the Kontro unit 6, an electrical connection is provided. The sampling clock input 21 leads internally to a sampling clock unit 22, which is connected to a sampling element 23 acting on the sampling input 14.

The wheel module 3 includes an LF receiving antenna 24, a control and KontroUeinheit 25, a sensor 26 and an RF transmitting antenna 27. The control and KontroUeinheit 25 is the central element to which all other components of the wheel module 3 are connected.

The operation of the device 1 will be described below.

From a provided by the external clock generator 16 clock signal T with the frequency fO a low-frequency signal of the frequency f 1 is generated in the frequency Teüer 19 and supplied via the signal conditioning unit 7 and the driver 8 as a transmission signal Sl of the LF transmission antenna 9. The frequency fO is 13.4975 MHz and the frequency f 1 is 124.977 kHz. The frequency divider 19 has a division factor of 108 in the Ausführangsbeispiel.

The transmission signal Sl is emitted and passes via the wireless connection 4 to the LF reception antenna 24, from which it is received signal E2 Will be received. The control and KontroUeinheit 25 wins from the received signal E2 on the one hand, the energy required for the operation of the wheel module 3 and derives on the other hand by means of frequency multiplication by a factor of 108.5 a significantly higher frequency £ 2 with a value of 13.56 MHz , The sensor 26 detects the pressure currently prevailing in the tire. This is modulated with further data as data signal D in the control and KontioUeinheit 25 to a carrier signal to a transmission signal S2. The data rate of the data signal D is also derived from the received frequency fl. It is for example 31.25 kBaud. The modulation method used is a PSK (Phase Shift Keying) method. However, an ASK (= Amphtude Shift Keying) method or another modulation method would also be possible. Since both the frequency f2 and the data rate of the data signal D are derived from the frequency f 1 of the received signal E2, the data information in the transmit signal S2 is also phase-locked to the frequency f0 of the clock generator 16.

The transmission signal S2 is transmitted from the RF transmission antenna 27 via the wireless connection 5 to the RF reception antenna 10 and received there as the reception signal El. It is fed via the input amplifier 11 in the mixer 12, in which a mixture with a comparison signal V to an intermediate frequency signal ZF1. The comparison signal V is derived from the clock signal T provided for clock supply to the control unit 6. In particular, it is substantially equal to the clock signal T, which is looped through the control unit 6 via the decoupler 18 designed as a driver or as a buffer circuit and is present at the comparison input 20a of the mixer 12. The decoupler 18 prevents unwanted feedback on the Clock generator 16. The comparison signal V has the same frequency f0 as the clock signal T, ie 13.4975 MHz. A separate LokalosziUator that would otherwise be anszuschheßen to the comparison input 20a of the mixer 12, so is not needed. This results in a cost-effective implementation of the demodulation subunit.

The intermediate frequency signal ZF1 first passes through a narrow-band frequency filter in the signal conditioning unit 13, for example a low-pass filter or a bandpass filter. Thereafter, by means of a suitable circuit, an amphetous limitation and a conversion into a rectangular signal can take place. Here, the use of a Schmitt trigger is possible. At the output of the signal processing unit 13 there is then a conditioned intermediate frequency signal ZF2 having a substantially rectangular waveform and a main frequency f3. The frequency f3 in the example has the value 62.5 kHz.

As soon as the intermediate-frequency signal ZF2 arrives at a value different from the quiescent level, the control unit 6 is awakened by a corresponding signal level at the wake-up input 15. This is done, for example, by means of a standard interrupt.

The intermediate frequency signal ZF2 is also at the sampling input 14, which is designed as an SPI (= Serial Peripheral Interface) input. This causes, that only at certain times, that of the in the example as

SPI clock trained sample clock unit 22 are given, the signal level of the pending intermediate frequency signal ZF2 as an input signal in the KontroUeinheit 6 arrive. At the sampling 14 so a sampling takes place, in the DarsteUung of FIG. 1 by the Abtastglied 23 and the sampling clock unit 22 is symbohsiert. In conjunction with the mixer 12 and the sign processing unit 13, this sampling results in synchronous demodulation. The demodulated data signal D either directly corresponds to the supplied by the Abtastghed 23 discrete input signal or can be generated in a simple manner and with purely digital combination operations from the discrete input signal.

Representing several conceivable embodiments, FIG. 2 illustrates a possible mode of action based on time diagrams. The above-mentioned data signal D corresponds to a bit string of "1", "0", "0" and "1". The associated conditioned intermediate frequency signal ZF2 is shown in the middle. For sampling purposes, a sampling signal AI reproduced below is provided by the sampling clock unit 22. In this case, the sampling signal AI has the same frequency f 1 as the transmission signal S 1. Both signals are derived from the output signal of the frequency divider 19, ie ultimately from the clock signal T of the clock generator 16. The sampling of the intermediate frequency signal ZF 2 takes place in each case at a flush edge of the sampling signal AI. This results in discrete samples with logic levels, which are marked with circles in FIG. 2 in the intermediate frequency signal ZF2. A Nutzsignalbit are assigned four samples in this choice of frequencies fO, fl, f2, f3 and the data bit rate of the data signal D. A useful signal bit with the logical value "1" corresponds to the sampled level sequence "1 0 1 0" and a useful signal bit with the logical value "0" corresponds to the sampled level sequence "0 1 0 1".

In order to ensure as smooth a sampling as possible, a sampling signal A diverted from the output signal of the frequency divider 19 can be delayed by means of the delay input element 20 by an adjustable period of time. to be cleaned. This allows a flexible adaptation to the transit times of the signals Sl, E2, S2, El, ZF1 and ZF2. The delay time can be acknowledged by the control unit 6 according to the specifications of a pre-runtime measurement. Alternatively, however, the required delay time can also be determined autonomously by the control unit 6 at the beginning of the operation, for example by means of a few previously transmitted synchronization bits which trigger a time measurement at each edge change of the intermediate frequency signal ZF2. This variant is particularly advantageous if no closed signal circuit as in the device 1 vorhelgt, but only a unidirectional subsystem with a signal path from the sensor 26 to KontroUeinheit 6. For example, three measurements to synchronization bits by averaging the required Zeitverzögerang for the sampling clock 22nd be determined and set.

A particular advantage of the device 1 is that all frequencies are derived from the clock signal T of the external clock generator 16. As a result, on the one hand eliminates the need for other clock generators and on the other hand, the various signals each have a fixed phase relationship to each other. As a result, the described, very simple and inexpensive to implement synchronous demodulation method, which makes do without the otherwise usual for a demodulation modules, allows. Due to the hardware and software technical integration of KontroUemheit 6 in the demodulation process results in a cost savings.

The demodulation method and the device 1 are also to be used in a very large frequency interval. The frequencies f0, f1, f2 and £ 3 used, as well as the data bit rate, can be in a wide range Range can be varied. The frequency f0 should only be chosen to be within the frequency range specified for the control unit 6. In addition, the frequencies should be chosen so that the condition f0 = f2 ± f3 is fulfilled. Compliance with these conditions is easily possible. Otherwise, there is extensive freedom of choice for the frequencies used. Also with regard to the modulation method used, there is a high degree of flexibility.

Furthermore, the device 1 is also suitable for bidirectional data transmission. The transmission signal Sl can nä hch except for energy transmission and data transmission from the controller 2 to the wheel module 3 are used. For this purpose, a carrier signal of the frequency f 1 in the control unit 6 modulates a corresponding data signal. Detection takes place in the KontioUeinheit 25 of the wheel module. 3

In Fig. 3 a second Ausführangsbeispiel a device 28 for data transmission and demodulation dargesteUt dargesteUt. The device 28 differs from the device 1 according to FIG. 1 only in a few aspects. A control device 29 contains a slightly differently constructed control unit 30. A first difference is that the delay element 20 is not guided to an output of the control unit, but is internally connected to the sampling clock unit 22 by means of a further optional frequency divider 31. In the Ausführangsbeispiel of Fig. 3, the frequency divider 31 causes a halving of the frequency fl of the sampling signal A, so that the scanning member 23 of the sampling clock 22, a sampling signal A2 is supplied with a frequency f4 of 62.5 kHz.

This results in the sampling ratios that are dargesteUt in the Zeitdiagra men of FIG. 4. For each useful signal bit, one then obtains two Tastwerte, which are indicated in Fig. 4 again by circles. A useful signal bit with the logical value "1" is then symbolized by the sampled level sequence "1 1" and a useful signal bit with the logical value "0" by the sampled level sequence "00".

Another difference is that the clock signal T is not looped through the control unit 30. Instead, an external connection line 32 is provided between the clock generator 16 and the mixer 12. If required, the external connection line 32 can also be equipped with a decoupler or a buffer circuit.

The described differences between the devices 1 and 28 do not affect the principle of operation and the advantages mentioned.

Claims

claims

1. A method for demodulation of a aufmoduhertes data signal (D) comprising input signal (El), in which - from the input signal (El) and a comparison signal (V) by means of mixing an intermediate frequency signal (ZF1) is generated from the intermediate frequency signal (ZF1) means a conditioned intermediate frequency signal (ZF2) is generated, and - the data signal (D) is recovered from the conditioned intermediate frequency signal (ZF2) by means of a control unit (6; 30) supplied with a clock signal (T), characterized in that the Comparison signal (V) is derived from the clock signal (T).

2. The method according to spoke 1, characterized in that the clock signal (T) is used directly as a comparison signal (V).

3. The method according to spoke 1, characterized in that the input signal (El) by means of receiving a transmission signal (S2) is obtained and the data signal (D) phase-locked to the clock signal (T) is modulated onto the transmission signal (S2).

4. The method according to any one of the preceding claims, character- ized in that the processed intermediate frequency signal (ZF2) for recovering the data signal (D) with a from the clock signal (T) derived scanning signal (AI, A2) is sampled.

5. The method according to spoke 4, characterized in that the scanning signal (AI, A2) is delayed relative to the clock signal (T) by a einsteUbare period.

6. The method according to any one of the preceding claims, characterized in that the intermediate frequency signal (ZF1) for generating the processed intermediate frequency signal (ZF2) subjected to a low-pass or bandpass filtering and then limited in particular in the amplitude and preferably converted into a square wave signal.

7. Device for demodulation of an up-modulated data signal (D) comprising an input signal (El) comprising at least one mixer (12) for mixing the input signal (El) with a at a comparison input (20a) of the mixer (12) pending comparison signal (V ) to an intermediate frequency signal (ZF1), a signal conditioning unit (13) connected to the mixer (12) for generating a processed intermediate frequency signal (ZF2) from the intermediate frequency signal (ZF1), a contrast unit (6) connected to the signal conditioning unit (13) 30) for recovering the data signal (D) from the conditioned intermediate frequency signal (ZF2), a clock generator (16) supplying the control unit (6; 30) with a clock signal (T), characterized in that a connection (18, 18a; 32) between the comparison input (20a) and the clock generator (16) and the comparison signal (V) is derived from the clock signal (T).

8. Device according to spoke 7, characterized in that the connection between the comparison input (20 a) and the clock generator (16) as an external connecting line (32) is formed.

9. Device according to spoke 7, characterized in that the connection (18) between the comparison input (20 a) and the clock generator (16) at least partially through the control unit (6).

10. Device according to one of claims 7 to 9, characterized in that the control unit (6, 30) has a scanning input (14), by means of which the control unit (6, 30) is connected to the signal-conditioning unit (13), and the recovery of the data signal (D) by means of a scan takes place.