DE19739898C2 - Multipath reception method - Google Patents

Description

The invention relates to a method for multipath reception and for the selection of n multiple transmission paths incoming signals and circuit arrangements to carry out the method according to the invention.

The reception and playback of television pictures in fixed receiving stations poses no difficulties because the reception conditions are largely constant stay. In contrast, the reception conditions for a mobile receiving station can fluctuate considerably depending on the nature of the terrain. Is the mobile Receiving station z. B. in a mountainous landscape, echoes can receive significantly disrupt; in the radio shadow of mountains or hills, the radio connection can even collapse completely, so that instead of a television picture only Noise can be seen on the screen.

In the meantime, vehicles such as B. Cars and coaches, but also Railway vehicles equipped with television receivers and screens to one hand Display messages, for example traffic reports transmitted via teletext or on the other hand to be able to entertain the travelers with television programs. Due to the fact that due to the currently used terrain, considerable fluctuating reception conditions in a moving receiving station the eyes of traveling television viewers strained in an uncomfortable manner, because the image quality can fluctuate considerably. Passes through the vehicle z. B. a radio shadow, the viewer only sees noise on the screen. The Viewing a television program with such interference is more likely to cause fatigue the spectator as that it serves their entertainment.  

It is known to receive radio signals in mobile receiving stations To improve multi-path reception, in English called diversity. Under Antenna diversity is understood to mean that a receiver is usually spatially connected to one of several separate antennas can be connected, while with frequency diversity a system is called several receivers, the same on different frequencies Receive signals or the same programs. The antenna diversity of the Antennas and at frequency diversity signals provided by the receivers checked for quality in order to find the signal of the best quality manage and further process.

Antenna diversity systems are e.g. B. in DE 39 26 336 A1 and in DE 41 01 629 C2 described.

It is an object of the invention to provide a method for multipath reception of signals to be designed so that the reception of television signals in particular in mobile Receiving stations is improved while driving.

The invention solves this problem by the features of the patent saying 1.

An advantage of the method according to claim 1 is that a memory more is provided than there are transmission paths, so that the signal is always in one of the memories remains stored with the best quality, while the content of the remaining n Memory with the waveforms of the next periods of the n signals be overwritten. This measure has the when receiving television signals Advantage that if the reception is poor or if the reception collapses last partial, field or full image still received in sufficient quality or the last image line still received in sufficient quality in one of the n + 1 memories is saved and thus on the screen as a replacement for the current television picture or current image line of poor image quality can be displayed.

A second solution of the invention for receiving television signals provides that 2n Memory are provided in which two successive partial, half or Full images that arrive on the n transmission paths are stored line by line be that the quality of each line is evaluated using a specifiable criterion to create a television picture from the era of the highest quality.

According to the first solution according to the invention, one of the n memories is switched on Predeterminable time period of one received on one of n transmission paths Signal stored. The qualities of the individual over the n transmission paths received signals are compared to each other to get the best quality signal find out. Only this signal is used for further storage Signal processing forwarded. At the same time, the waveforms of the next  Periods of the signals arriving on n signal paths are read into the memories. As The criterion for the quality of a signal can be the signal level, the noise level or the Serve signal-to-noise ratio.

The n signals arriving on n transmission paths, e.g. B. television signals can for example received by n tuners on different frequencies. The Tuners can be connected to a common antenna, but they can also be connectable to one of several antennas according to the antenna diversity principle.

The invention will now be exemplified on the basis of circuit arrangements Implementation of the method according to the invention described and explained.

Show it

Fig. 1 shows a circuit arrangement for carrying out the method according to claim 1,

Fig. 2 shows an advantageous embodiment of the circuit arrangement from Fig. 1,

Fig. 3 shows a circuit arrangement for implementing the method according to claim 2

Fig. 4 shows an advantageous embodiment of the circuit arrangement from Fig. 3,

Fig. 5 shows the time course of the reception level and an adaptive quality threshold.

In Fig. 1, the outputs of n tuners T1 to Tn are connected to the inputs of n controllable tuner switches UT1 to UTn, which have n + 1 outputs, so that each tuner T1 to Tn is connected to a tuner switch UT1 to UTn. One output of each tuner switch UT1 to UTn is connected to a memory S1 to Sn + 1. In other words, for all tuner switches UT1 to UTn, the first output with the first memory S1, the second output with the second memory S2 etc. until finally the (n + 1) th output with the (n + 1 ) -th memory Sn + 1 is connected. The outputs of the n + 1 memory S1 to Sn + 1 are connected to the n + 1 inputs of a controllable memory switch U, at the output of which a screen BS, which, for. B. can be a liquid crystal screen is connected. The outputs of the tuners T1 to Tn, for each of which an antenna A1 to An or only one common antenna is provided, are connected to the n inputs E1 to En of a control processor QC whose n control outputs SA1 to SAn are connected to the control inputs of the controllable tuner switch UT1 are connected to UTn, during which the control output SA is connected to the control input of the controllable memory switch U.

To explain the circuit arrangement shown in FIG. 1, it is assumed, for example, that the circuit arrangement is installed in a moving car and that the tuners T1 to Tn receive the same television program on different frequencies. The control processor QC controls the controllable tuner switch UT1 to UTn such that the signal profiles of predeterminable time segments of the television signals supplied by the tuners T1 to Tn are read in n of the n + 1 memories S1 to Sn + 1. The signal curves can be a picture line, a field or a full picture.

The control processor QC constantly checks the quality of the outputs of the n tuners T1 to Tn tapped television signals and always switches the memory in which the The best quality television signal is available via the controllable memory switch U Screen BS through.

If not n but n + 1 memories are provided, as shown in FIG. 1, the last best partial, field or full image or the last best image line can always be stored in one of the n + 1 memories S1 to Sn + 1 , because n memories are available for reading in the signal curves of the next time segments, the old contents of which can be overwritten. If the quality of the current television picture drops below a predeterminable threshold value or if there is even noise, the last high-quality television picture stored in one of the n + 1 memories can be shown instead of the bad or noisy current television picture.

FIG. 2 shows an advantageous embodiment of the circuit arrangement from FIG. 1. Instead of providing an antenna A1 to An for each of the n tuners T1 to Tn, each tuner T1 to Tn is preceded by a controllable antenna switch UA1 to UAn, to which several antennas are connected. The antennas of the tuner T1 are denoted by A11 to A1m, those of the tuner T2 by A21 to A2m etc. and finally the antennas of the tuner Tn are denoted by A1n to Anm.

Depending on the quality of the antenna signals, the control processor controls QC the individual controllable antenna switch UA1 to UAn so that each tuner always receives the signal from the best receiving antenna.

The circuit arrangement shown in FIG. 3 for carrying out the method according to claim 2 will now be described and explained.

The outputs of n tuners T1 to Tn, to which an antenna A1 to An is connected is, with the inputs of n controllable tuner switches UT1 to UTn each two outputs connected. Each output of the controllable tuner switch UT1 to UTn is connected to one of 2n memories S11 to S2n.

The outputs of the 2n memories S11 to S2n are controllable with the 2n inputs Memory switch U, at the output of which a screen BS is connected, and with connected to the 2n inputs E11 to E2n of a control processor QC. The Control outputs SA1 to SAn of the control processor QC are with the control inputs the n controllable tuner switch UT1 to UTn connected while the control output SA of the control processor QC to the control input of the controllable memory switch U is connected.

As with the previously described circuit arrangement from FIG. 1, it is assumed by way of example that the circuit arrangement for receiving television programs is installed in a car.

The control processor QC controls the n controllable tuner switches UT1 to UTn so that in the 2n memories S11 to S2n the lines of two successive half or frames are stored so that two from each tuner successive fields or frames are stored.

The control processor QC evaluates the quality of all in the 2n memories S11 to S2n stored image lines and controls the controllable memory switch U so that each TV picture is generated from the picture lines with the best quality in each case. That can e.g. B. look so that the first image line from the memory S1n, the second from the Memory S11, the third from memory S25, the next from another Memory is read in order to get the best possible television picture on the screen BS to create. While with the n one memories the image lines to generate one TV picture are read out, are simultaneously in the n other memory new image lines are read in, which are then read out in the next step. The Storage tanks are therefore filled and emptied alternately.

In FIG. 4, an advantageous embodiment of the circuit arrangement in FIG. 3 is depicted. Instead of providing an antenna A1 to An for each of the n tuners T1 to Tn, each tuner T1 to Tn is preceded by a controllable antenna switch UA1 to UAn, to which several antennas are connected. It is Z. B. also possible to assign a different number of antennas to each tuner. The antennas of the tuner T1 are designated in FIG. 4 with A11 to A1m, those of the tuner T2 with A21 to A2m etc. and finally the antennas of the tuner Tn are designated with A1n to Anm.

Depending on the quality of the antenna signals, the control processor controls QC the individual controllable antenna switch UA1 to UAn so that each tuner always receives the signal from the best receiving antenna.

According to claim 22, it is provided to process sound and image separately. For the Television sound one or more tuners are provided, one of which is the control processor selects the one who delivers the sound signal of the best quality.

According to claim 9, the image quality of the current one is not provided as usual Compare the television picture with a fixed quality threshold; rather it is Quality threshold at which the quality of a current television picture is measured  designed so adaptively that it always has a predeterminable value under the quality of a previous television picture or several previous television pictures is or in other words a predetermined percentage of the quality of a previous television picture or several previous television pictures. The quality of the preceding television picture is preferably used as a criterion to assess the current television picture. But it is also possible to get out several previous television pictures a quality criterion for assessing the to form the current television picture.

If the picture quality of a current television picture z. B. under the previous TV picture set adaptive quality threshold decreases, rather than the current one TV picture to show the old picture repeated. Only after several z. B. 20 to 50 Repetitions of a television picture or if the picture quality is an absolute Below the quality threshold, a still image, e.g. B. a test pattern or the like instead of the repeated image. By adapting the quality threshold The viewer perceives the picture quality of the previous television picture Fluctuations in reception are less uncomfortable than with a television receiver that does not work according to the inventive method.

A compromise between image quality and timeliness is sought. At declining image quality, image quality is given higher priority than that Timeliness; it will therefore be the previous television picture instead of the current one TV picture shown expecting the quality of the next picture again will be satisfactory. However, if this is not the case, priority will be given changed. Up-to-dateness is now given higher priority than image quality; despite the poorer picture quality, the current television picture is now repeated instead of shown previous television picture shown on the screen to the To provide viewers with new information.

In the control processor QC z. B. the reception level, the noise level or the signal Noise ratio compared to the adaptive quality threshold.

In FIG. 5, by way of example the time profile of the signal level and the adaptive quality threshold is shown. The level is drawn as a solid line, while the adaptive quality threshold is shown in dashed lines.

Because the level of the television picture 2 is above the adaptive quality threshold of the television picture 1 , the television picture 2 is shown. The level of the television picture 3 , on the other hand, is below the adaptive quality threshold of the television picture 2 . Therefore, instead of showing the current television picture 3 , the old television picture 2 is repeated. The levels of television pictures 4 and 5 are above the relevant quality thresholds; these pictures are therefore shown. Because the levels of television images 6 and 7 are each below the adaptive quality threshold, television image 5 is repeated. Finally, the level of the television picture 8 is even below a predeterminable absolute threshold AS. In this case, a still picture, e.g. B. a test image shown on the screen.

The invention is generally suitable for receiving devices whose input signals are strong Subject to quality fluctuations. The invention is particularly advantageous in Use television receivers in vehicles such as cars, coaches or railway vehicles are installed.

Claims (23)

1. A method for multipath reception and for the selection of n signals arriving on several transmission paths , characterized in that at least n memories (S1, S2, ..., Sn) are provided for temporarily storing the signal profiles of the individual received n signals during predeterminable time periods, the Quality is evaluated on the basis of a predefinable criterion,
that at least one further memory (Sn + 1) is provided, that the memory content that last fulfills the quality criterion is retained during reading in, while the contents of the remaining n memories are overwritten,
and that the memory with the signal of the best quality is read out, while at the same time the next time period of the n signals is read into the n memories (S1, ..., Sn). 2. Methods for multipath reception and for the selection of n from several Incoming television signals, characterized in that that 2n memories (S11, ...; S2n) are provided, in which two successive fields, fields or frames that are on the transmission paths arrive, line by line, that the quality of each line is on hand of a predefinable criterion is evaluated in order to obtain a television picture from the Generate rows of the highest quality.   3. The method according to claim 1, characterized in that n tuners (T1, ..., Tn) for receiving the n signals are provided, the outputs of which are by means of n controllable tuner switch (UT1, ..., UTn) with the n or n + 1 memories (S1, ..., Sn + 1) can be connected. 4. The method according to claim 2, characterized in that the n television signals of n tuners (T1, ..., Tn), which can be controlled by means of n Tuner switch (UT1, ..., UTn) with two of the 2n memories (S11, ..., S2n) are connectable. 5. The method according to claim 3 or 4, characterized in that the n tuners (T1, ..., Tn) according to the frequency diversity method Frequencies are tunable. 6. The method according to claim 3, 4, or 5, characterized in that at least one of the n tuners (T1, ..., Tn) according to the antenna diversity method one of several antennas can be connected. 7. The method according to any one of the preceding claims, characterized in that that in the memories a picture line, a field or a full picture of a TV signal is stored. 8. The method according to any one of the preceding claims, characterized in that the picture quality of a current television picture with an adaptive Quality threshold is compared, each a predeterminable value below the picture quality of a previous television picture or several previous television pictures lies, and that when the adaptive Quality threshold the old television picture is shown instead of the current television picture becomes. 9. The method according to claim 8, characterized in that the adaptive Quality threshold each a predeterminable value below the image quality of the previous television picture lies.   10. The method according to claim 8 or 9, characterized in that at Fall below the picture quality of a television picture below an absolute Quality threshold (AS) a still image or the last one with satisfactory quality generated television picture is shown. 11. The method according to claim 8, 9 or 10, characterized in that after a predeterminable number of successive repetitions of the same TV picture due to falling below the adaptive quality threshold instead of repeated TV picture the current TV picture or a still picture is shown becomes. 12. The method according to claim 8, 9, 10 or 11, characterized in that as Criterion for the picture quality of a television picture of the signal level is provided. 13. The method according to claim 8, 9, 10, 11 or 12, characterized in that as Criterion for the picture quality of a television picture of the noise level is provided. 14. The method according to claim 8, 9, 10, 11, 12 or 13, characterized in that as a criterion for the picture quality of a television picture the signal-noise Ratio is provided. 15. Circuit arrangement for multipath reception and for the selection of n multiple incoming signals characterized in that the output one each of n tuners (T1, ..., Tn) to the Input of one of n controllable tuner switches (UT1, ..., UTn) with n Outputs is connected so that each tuner (T1, ..., Tn) with a Associated controllable tuner switch (UT1, ..., UTn) is connected that one output each of the n outputs of the n controllable tuner switches (UT1, ..., UTn) is connected to the input of one of n memories (S1, ..., Sn), so that each tuner (T1, ..., Tn) can be connected to each of the n memories (S1, ..., Sn) that the outputs of the n memories (S1, ..., Sn) with the n inputs of a controllable Memory switch (U) are connected, at the output of which a screen (BS) is connected that the outputs of the n tuners (T1, ..., Tn) with the n inputs (E1, ..., En) of a control processor (QC) are connected, whose n control outputs (SA1, ..., SAn) with the control inputs of the n controllable tuner switches (UT1,  ..., UTn) and its (n + 1) th control output (SA) with the control input of the controllable memory switch (U) is connected, and that the control processor (QC) depending on the quality of the n tuners (T1, ..., Tn) received signals the n controllable tuner switch (T1, ..., Tn) and the controllable memory switch (U) controls. 16. Circuit arrangement for performing the method according to claim 1, characterized in that the output each one of n tuners (T1, ..., Tn) the input of one of n controllable tuner switches (UT1, ..., UTn) with n + 1 Outputs is connected so that each tuner (T1, ..., Tn) with a Associated controllable tuner switch (UT1, ..., UTn) is connected that one output each of the n + 1 outputs of the n controllable tuner switches (UT1, ..., UTn) connected to the input one of each n + 1 memories (S1, ..., Sn + 1) so that each tuner (T1, ..., Tn) with each of the n + 1 memories (S1, ..., Sn + 1) it can be connected that the outputs of the n + 1 memories (S1, ..., Sn + 1) with the n + 1 Inputs of a controllable memory switch (U) are connected to the Output a screen (BS) is connected to the outputs of the n tuners (T1, ..., Tn) with the n inputs (E1, ..., En) of a control processor (QC) are connected, whose n control outputs (SA1, ..., SAn) to the control inputs the n controllable tuner switch (UT1, ..., UTn) and its (n + 1) -ter Control output (SA) with the control input of the controllable memory switch (U) is connected, and that the control processor (QC) depending on the Quality of the signals received by the n tuners (T1, ..., Tn) the n controllable Control tuner switch (T1, ..., Tn) and the controllable memory switch (U). 17. Circuit arrangement for performing the method according to claim 2, characterized in that the output each one of n tuners (T1, ..., Tn) with the input of one of n controllable tuner switches (UT1, ..., UTn) with each two outputs is connected so that each tuner (T1, ..., Tn) with one Associated controllable tuner switch (UT1, ..., UTn) is connected that each output of the controllable tuner switch (UT1, ..., UTn) with the input one of 2n memories (S11, ..., S2n) is connected that the outputs of the 2n Memory (S11, ..., S2n) with the inputs of a controllable memory switch  (U), at the output of which a screen (BS) is connected, and with the 2n Inputs (E11, ..., E2n) of a control processor (QC) are connected, the n Control outputs (SA1, ..., SAn) with the control inputs of the n controllable Tuner switch (UT1, ..., UTn) and its (n + 1) th control output (SA) with the control input of the controllable memory switch (U) is connected, and that the control processor (QC) depending on the quality of the in the 2n Save (S11, ..., S2n) stored image lines the n controllable Tuner switch (UT1, ..., UTn) and the controllable memory switch (U) controls. 18. Circuit arrangement according to claim 15, 16 or 17, characterized in that that the n tuners (T1, ..., Tn) are connected to a common antenna. 19. Circuit arrangement according to claim 15, 16 or 17, characterized in that an antenna (A1, A2, ..., An) is provided for each of the n tuners (T1, ..., Tn) is. 20. Circuit arrangement according to claim 15, 16 or 17, characterized in that one of several antennas by means of a controllable antenna switch, which is controlled by the control processor (QC) to the tuners (T1, ..., Tn) can be switched on. 21. Circuit arrangement according to claim 15, 16 or 17, characterized in that for each tuner (T1, ..., Tn) several antennas (A11, ..., A1m, A21, ..., Anm) are provided, one of which can be controlled by means of one each of n Antenna switch (UA1, UA2, ..., UAn) to one tuner each (T1, ..., Tn) can be connected, and that the n antenna switch (UA1, ..., UAn) from Control processor (QC) can be controlled. 22. Circuit arrangement according to claim 20 or 21, characterized in that the control processor (QC) the antenna switch (UA1, ..., UAn) in Controls dependence on the antenna signals. 23. The method or circuit arrangement according to one of the preceding claims, characterized in that when receiving television signals for reception of the sound one or more tuners are provided.