NL8602996A - Digital data diversity radio broadcasting system - includes in transmitted signals enabling car radio to re-tune automatically to alternative frequency if signal fades - Google Patents

Abstract

Incorporated in the broadcast signal is a repeated digital signal which can be interpreted as a physical matrix showing the relative positions of transmitters which carry the same programme. The signal from the aerial (A) is fed via an r.f. amplifier (1) to the frequency synthesis tuner (2). The signal is then fed via the i.f. system (3) and frequency detector (4) to the stereo demultiplexer (5) and thence to the loudspeakers (6). The detected signal is also fed to an RDS decoder (8) which provides fault correction facilities and the alternative frequency matrix data. The data, which are demodulated from its 57 kHz carrier, are then fed to an auxiliary microcomputer (9) which has an auxiliary memory (10). The main microcomputer (11) produces a signal which is fed back to the digital tuning input (7) to control the reception frequency.

Description

* I * PHN 11,969 1 N.V. Philips' Incandescent light factories in Eindhoven.

System for the transfer of digital information.

The invention relates to a system for the transmission of digital information in a radio broadcast signal, comprising a number of alternative frequencies, on which the same program signal can be received, as well as containing information regarding a matrix, within which the alternative frequencies can be arranged.

The transmission of alternative frequencies makes it possible to automatically tune a radio receiver to the radio signal with the same program, which has the best reception quality for the location of the respective receiver. Such automatic tuning is especially important for car radios.

The above system has been proposed to minimize the redundancy in the transmission of the alternative frequencies.

For this purpose, the alternative frequencies are arranged in a matrix according to the geographical location of the associated channels. The alternative frequencies are transmitted in a predetermined row or column order, preceded by an indication of the size of the matrix. For example, 20 alternative frequencies f · ^ (i = 1 ... 5, j = 1 ... 4) which can be arranged in a 5x4

Af J

Matrix are transferred sequentially in a column order, for example, preceded by the matrix size 5.4 as matrix information.

Since the entire matrix is already lost in the event of an error in the reception of a single alternative frequency or of the matrix information, it has been proposed to divide the matrix into rows or columns and to transfer the alternative frequencies in groups per row or column, preceded by the address and length of the appropriate row or column. Thus, the above 20 alternative frequencies can be transmitted in the following row-wise grouping .: 1.4, f15 (j = 1 ... 4), 2.4, f2j (3-1 ... 4), ... 5.4, f5j (j = 1 ... 4).

The consequence of an error in one of the alternative frequencies or in the sub-matrix information (address and length indication) is now limited to the 8602996 t PHN 11.969 2 concerning row or column.

The object of the invention is to indicate in a system of the type mentioned in the opening paragraph an opportunity to minimize the information lost due to an error in transmission and to realize in the receiver a reliable recognition of correctly received alternative frequencies. .

To this end, such a system according to the invention is characterized in that the alternative frequencies are preceded singly or in groups and are followed by first and second address words, respectively, each containing first and second location variables, of which the first location variables of both address words mutually are equal and the difference between the second location variables is equal to the number of alternative frequencies enclosed between the two address words.

When applying the measure according to the invention it is possible to divide each row or column of the matrix, in which the alternative frequencies to be transmitted are arranged into several groups of alternative frequencies of any desired, even variable, group length. An individual transfer of 20 alternative frequencies is also possible and, because of the addressing per group or individually, one is not bound to a transfer sequence related to the matrix location. An error in transmission now results in the loss of only a small group of alternative frequencies and in individual transmission, the loss of only a single alternative frequency.

Moreover, the method of addressing according to the invention offers the possibility of a fast and reliable error detection: correct reception has only taken place if each of the two location variables of the two address words satisfies the aforementioned conditions.

In order to enable a rapid selection of alternative frequencies within a matrix on which, for example, a different program is temporarily broadcast than the other alternative frequencies within the matrix, the system according to the invention is characterized in that the digital information also comprises a number of further alternative frequencies on which a further program signal can be received which deviates from the first mentioned program signal 8602996% r PHN 11,969 3, as well as a program indication for identifying each of the two program signals.

A receiver for use in a system according to the invention is preferably characterized by means in which the first 5 location variables of two address words are mutually compared and the difference between the second location variables is determined, in which this difference is compared to the number of alternative frequencies enclosed between the two address words and in which, with mutually equal first location variables and a difference between the second second location variables, corresponding to the latter number, the alternative frequencies are stored in an addressed matrix memory.

The invention will be explained in more detail with reference to the figures shown in the drawing, which serve only as example 15.

In it shows:

Figures 1A and 1B show a number of alternative frequencies arranged in a matrix;

Figure 2 shows a radio receiver for receiving addressed groups of alternative frequencies in a system according to the invention.

Figure 1A shows the locations of 20 transmitters, which mutually transmit the same program signal, respectively modulated on 20 different carrier frequencies f; ^

J

25 (i = 1 ... 5, j = 1 ... 4) in a certain geographical area. For example, six stations, namely those with carrier frequencies f ^ j (j = 1 ... 4), f21 and f22, broadcast regional or local programs at certain times, which deviate from the program of the other 14 stations. After a suitable compression, these 20 transmitters can be arranged in a geographically oriented matrix as shown in figure 1B.

In the context of the Radio Data System (RDS) as described in Doc. Techn. No. 3244 of the European Broadcasting Union, a block of 2 bytes in a certain standardized word format has been made available for the transmission of alternative frequencies. A practical grouping of alternative frequencies within the RDS is obtained by dividing the alternative frequencies in pairs, for example in a row-wise sequence. Each alternative frequency 8602996 t * PHN 11.969 4 pair can then be transmitted in one block, preceded and followed by address blocks, which contain the first and second address words, respectively. Upon receipt of two address blocks and the alternative frequency block therebetween - hereinafter referred to as block triplet 5 - an error detection can be performed as described below.

When the latter paired arrangement of alternative frequencies is applied to the matrix of Figure 1B, the following sequence of address words and alternative frequencies is transmitted: Y = 1 X = 1 Y = 1 X = 3 f13f14 Y = 1 X = 5 Y = 2 X = 1 12 ^ 22 Y = 2 x = 3 f23f24 Y = 2 x = 5 Y = 3 X = 1 f3lf32 Y = 3 x = 3 f33f34 Y = 3 x = 5 Y = 4 X = 1 f41f42 Y = 4 X = 3 f43f44 Y = 4 X = 5 Y = 5 X = 1 f51f52

Y = 5 X = 3 f53f54 Y = 5 X = 5. In it, Y sets the value of the first and X

15 the value of the second location variable for.

The address words at the end of each row of alternative frequencies refer to the matrix locations, which do not exist, i.e. in which no alternative frequency occurs. It will be understood that in a columnwise distribution of alternative frequencies, the address values at the end of each column refer to nonexistent matrix locations.

Because of the addressing, it is not necessary to follow a matrix oriented sequence upon transmission, but the block triplets may follow each other in any sequence upon transmission.

The availability of 2 bytes in the alternative frequency block also allows individual transfer of the alternative frequencies. One byte then remains per block, which can be used by a program indication or to indicate a specific deviating channel grid (for example 50 KHz), in which the relevant alternative frequency is rasterized.

It will be clear that with an individual transmission of alternative frequencies the second location variation of the second address word differs only one from that of the first address word.

Furthermore, it is also possible to include several alternative frequency blocks between the first and second address words.

8602996% v PHN 11,969 5

The difference between the second location variables of these two address words should then be equal to the number of alternative frequencies included in the alternative frequency blocks. In the latter mode of transmission of alternative frequencies, an error will cause the information of 3 blocks, ie one alternative frequency pair, to be lost. However, since the undisturbed part of the aatrix in the receiver can be reconstructed correctly, the time to obtain the full aatrix information will be much shorter than in the known system.

An FM radio receiver suitable for receiving and processing the addressed groups of alternative frequencies in the radio signal of the system according to the invention in a sequence as shown above in figure 2.

This FM receiver successively comprises an HF input part 1, a frequency synthesis division part 2 with a digital tuning input 7 for supplying a digital tuning number, a medium frequency part 3, a frequency detector 4 and a frequency detector connected to an antenna-input 15. the multiplexer / audio signal processing unit 5, which supplies audio frequency left and right stereo signals to two 20 speakers 6.

The signal processing in this part of the FM receiver is known per se: a desired FM-HF reception signal is fed after an amplification in the HF part 1 to the tuning part 2, in which a conversion to a certain FM center frequency takes place. In the MF-25 part 3, a selection of the MF-FM signal takes place followed by an FM deodulation in the FM detector 4. The baseband stereo-audio signal thus obtained is then decoded into left and right stereo signals in demultiplexer 5 and displayed with the speakers 6.

Starting from the RDS as described in the aforementioned EBU publication, the baseband multiplex signal also contains digital information in the form of standardized word formats sequentially broadcast, modulated on a 57 KHz carrier. In the so-called word group 0, a 2-byte block is reserved for the transmission of alternative frequencies and / or other information, for example a program or station grid indication. Furthermore, the alternative frequencies can be distinguished from other types of information 8602996 PHN 11.969 6 on the basis of the bit pattern and encoding takes place in the transmitter in such a way that a certain error detection and correction is possible on the receiver side. The receiver is also provided with a main microcomputer 11, in which a number of alternative frequencies are stored and which supplies tuning control signals to the tuning unit 2 for a repetitive measurement of the reception quality of the radio signal of at least part of the stored alternative frequencies. The reception quality of the current radio reception signal is continuously compared with that of the monitored alternative frequencies. The main microcomputer 11 automatically tunes the receiver to an alternative frequency if the reception quality of the latter alternative frequency becomes better than that of the current radio reception signal.

The receiver described so far is known as a so-called MCC receiver. This MCC receiver does not use the RDS information and is described in Revised European Patent Application 0 098 634. In such an MCC receiver, the alternative frequencies must be pre-entered by the user.

In order to automate this input of alternative frequencies, the receiver shown is provided with a so-called RDS decoder 8, which is coupled to the output of the FM detector 4 and in which a decoding, error correction and synchronization of the digital RDS signals takes place. The contents of the address and alternative frequency blocks are supplied byte-wise to an auxiliary microcomputer 9, which stores a received first address word and a subsequent alternative frequency pair mutually separated in an auxiliary memory 10. When a second address word is supplied the auxiliary microcomputer 9 the first location variable of this second address word with that of the first address word and the mutual difference of the second location variables of both address words by 2, ie with the number of alternative frequencies enclosed by the two address words. With a correct comparison result, ie mutually equal first location variables and a difference of the local variables, which in the present case is equal to 2, a transport of the alternative frequencies takes place under the control of the auxiliary microcomputer 9. auxiliary memory 10 to two memory locations in 8602996 PHN 11.969 7 a matrix memory (not shown), which is included in the main microcomputer 11. When, for example, the block triplet Y = 3 X = 1 fgi f ^ 2 Y = 3 X = 3, the alternative frequencies f ^ f32 are stored at the memory locations 3,1 and 3,2, i.e. f31 5 at the memory address Y = 3 given by the first address word X = 1 and f32 at the between the first and second address words given memory address Y = 3 X = 2. The auxiliary microcomputer 10 then writes in the auxiliary memory 10 the second address word over said first address word. The above error detection and eventual storage is repeated upon receipt of a further alternative frequency and second address block.

In this way, a gradual reconstruction of an alternative frequency matrix in the main microcomputer 11 of the receiver can be realized.

An error in the transmission of one of the bits in the above blocking triplet results in a comparison result which deviates from the aforementioned correct comparison result. There is then no storage of the alternative frequencies in the matrix memory until this triplet is correctly received in a subsequent transmission cycle.

This matrix, thus reconstructed, is selected in the main microcomputer 11 a group of alternative frequencies located in the vicinity of the current receiver location on the basis of the address information. For example, if the receiver is tuned to the alternative frequency f33, the alternative frequencies become f42, f43, f44, f32 »f34. f22 »f23 and f24 selected and monitored for reception quality. The other less relevant alternative frequencies are skipped, so that a quick scan can take place and the most recent measurement data are continuously available. When the reception location is changed, the area 30 to which the most relevant alternative frequencies are selected also changes, so that the receiver remains continuously tuned to the radio signal with the highest reception quality for the reception location, quickly and with a high degree of reliability. Tuning to the latter radio signal takes place with the aid of a tuning number 35 which is supplied by the main microcomputer 11 via the tuning input 7 to the frequency synthesizer of the tuning unit 2.

At certain times, the alternative frequencies 860 2 S 9 6 PHN 11.969 8 f 11 f. | 2 f13 f- | 4 f2i and f22 in the given example of Figure 1A can transmit a program signal which deviates from the program signal of the other alternative frequencies in the matrix. Since the alternative frequency block in the RDS comprises 2 bytes, it is possible to use one byte of the alternative frequency block for an individual transmission of alternative frequencies and one byte for program induction. The second location of the second address word must thereby differ one from that of the first address word and the error detection in the receiver must be adapted accordingly. In the matrix reconstruction, the storage of the program indication can be linked to or combined with the storage of the alternative frequencies, so that the group of alternative frequencies to be monitored can be selected not only by location but also by program.

Furthermore, it is possible with individual transmission of alternative frequencies to use the remaining byte to indicate a channel grid, which deviates from the normal channel grid. Thus, the digital numbers indicating an alternative frequency in the RDS signal can be correctly interpreted on the receiver side.

It goes without saying that application of the invention is also possible by transferring several alternative frequency blocks between first and second address words. The second location variable of the second address word should then show a difference with that of the first address word, which is equal to the number of alternative frequencies placed in these alternative frequency blocks. In addition, the first location variable in an address word does not necessarily precede the second, but the order can also be reversed. Of course, once selected order must be maintained for all address words.

It will be understood that in any arbitrary transfer of addressed groups of alternative frequencies, each group must be enclosed between first and second address words and no address words can be used in common. Furthermore, in practice it may occur that in certain geographical matrix locations no alternative frequencies occur. Such "holes" can be identified by appropriate addressing of one or more alternative 8602996 PHN 11.969 9 frequencies in adjacent matrix locations.

8602996

Claims (9)

System for the transmission of digital information in a radio broadcast signal, comprising a number of alternative frequencies, on which the same program signal can be received, as well as containing information regarding a matrix, within which the alternative frequencies can be arranged, characterized in that: that the alternative frequencies are preceded singly or in groups and followed by first and second address words, respectively, each containing first and second location variables, of which the first location variables of both address words are equal and the difference between the second location variables is equal is the number of alternative frequencies enclosed between the two address words. System according to claim 1, characterized in that the second address word of a single or group of alternative frequencies is also the first address word of a subsequent single or group of alternative frequencies. System according to claim 1 or 2, characterized in that the digital information also contains a number of further alternative frequencies at which a further program signal can be received, which deviates from the first-mentioned program signal, as well as a program indication. to identify each of the two program signals. System according to claim 3, characterized in that the program indication is transmitted at a fixed location relative to at least one of the two address words. 5. Receiver for receiving digital information in a radio broadcast signal of the system according to any one of the preceding claims. 6. Receiver according to claim 5, characterized by means in which the first location variables of two address words are mutually compared and the difference between the second location variables is determined, wherein this difference is compared with the number of alternative words enclosed between the two address words. frequencies and in which mutually equal first location variables and a difference between the second location variables, corresponding to the latter number, the alternative frequencies stored in an addressed matrix memory. 7. Receiver according to claim 6, characterized in that the alternative frequencies within one contiguous group are stored at an address in the matrix memory, indicated by one of the two address words in case the group is a single alternative frequency and also at addresses located between those indicated by the two address words, in case the group 5 comprises several alternative frequencies. The receiver of claim 5 for receiving alternative frequencies with a program indication characterized by means for adding the program indication to the associated group of alternative frequencies in the matrix memory. 10 Receiver according to claim 8, characterized by selection means for a program-wise selection of alternative frequencies. 8602996