EP0762681B1 - Method and circuit for changing broadcast programmes during short signal interruptions - Google Patents

Abstract

An EON list of transmission frequencies of radio transmitters and an AF list of alternative transmission frequencies is transmitted with the RDS data. Attempts are made to change to an alternative frequency when the field strength of the received signal falls below a minimum value. After several futile attempts to switch to an alternative frequency, the frequency range of signals indicated to have a minimum field strength is scanned. The frequency of these signals is compared with the frequencies stored in the EON list and when there is a coincidence the transmission frequency is adjusted.

Description

The invention relates to a method for changing the program for a short time Signal dropout according to the preamble of claim 1.

In the radio data system RDS are from the associated broadcasting stations digital data broadcast parallel to the current radio program a recipient u. a. with the help of so-called AF codes (AF = alternative Frequencies) give information about which replacement frequencies are used for the same Program can be received again. That way it is possible, especially mobile receiving devices, if the Reception conditions automatically, without audible interruption for the Device users, on alternative frequencies with good ones Switch reception properties so that a largely undisturbed Sound reproduction is guaranteed. Details of digital Data transmission are in accordance with the European standard EN 50067 (Specification of the radio data system RDS) from April 1992.

The data transmitted in the radio data system also include extended information about other program chains (EON = Enhanced Other Networks Information). With the help of this information Receiver while receiving normal radio programs automatically tuned to the frequency of a traffic information station as long as this traffic information station is a current traffic report common. This gives the driver the opportunity to to receive any radio program without traffic announcements, without having to forego current traffic reports.

For the identification of traffic radio stations are the normal of the Radio program broadcasting transmitter and PI codes (Program Identification Codes) to identify the program chains as well as PS codes (Program Service Codes) to transmit the maximum of 8 Alphanumeric characters of existing program names (e.g. .. "Bayern 3") and AF codes (Alternative Frequencies Codes) for Provision of replacement frequencies for the respective traffic radio station transfer. This means that in countries such as Germany, the over country-based broadcasters have largely ensured that when automatically switching a receiver to the Receiving frequency of a traffic radio station one for the driver current traffic announcement with good reception quality is transmitted.

It is different in countries where the programs are less national program chains by transmitting stations with high transmitting power to be spread throughout the country, while for geographical Differentiation, especially for traffic news, local channels with low transmission powers are used. This currently applies. for England where the programs "BBC R1" to BBC R4 "throughout the country can be received. Since the local channels mostly from their own Radiate transmission towers with lower transmission power, they are only in locally or regionally limited areas with sufficient Receive transmission quality. Furthermore, due to the low transmission power of the local transmitters the frequency of interference, for example caused by radio shadows from houses, mountains or Tunnel, too. Nevertheless, a receiving device that is outside the the actual reception area of a local station, try to switch this local traffic information station as soon as it is over the current received national station the indication of an upcoming Receives traffic announcement. This initially becomes the one currently received national program muted until the receiving device determines that the PI code of the traffic radio station offered is not can be detected properly. This process can take up to one Last second before the receiver on the previously received Switches back program. Because the traffic announcement different Local stations are staggered in time, it can lead to the continuous disruption of the Reception of a nationally broadcast program.

Especially in tunnels, however, are often at least a small one Number of traffic radio stations via filling stations with special Antenna systems broadcast.

From DE-A1-39 36 577 a radio receiver is known which with the help address data transmitted in the RDS signal is able to standardized texts for the description of the Show traffic situation optically or acoustically. So that only certain the respective area of action of the mobile receiver Traffic information is issued, contains the Radio receiver a first memory in which a list of different Regions and the station frequencies receivable there are permanently stored is. The channels that can be received on-site are scanned via a channel search Transmission frequencies are written into a second memory and via a Comparison device with the frequencies stored in the first memory compared. The current reception region is then determined at the at least partial agreement between the frequencies in the Save 1 and 2 is detected.

The circuit arrangement mentioned has the disadvantage that it is the default the regional transmit frequency lists require additional memory, the content of which is only valid as long as it is not that of a region assigned transmission frequencies can be changed. Also for the Device export different device versions necessary.

In contrast, EPA-0 446 985 has a method with which a Current traffic announcement from the radiating traffic radio station in the RDS data stream is provided with a classification code word that one Receiver enables between local, regional and national Distinguish traffic news. Through manual programming of the receiving device, the device user can predetermine which type from traffic announcement he wishes to hear.

However, this method requires an intervention in the transmitter digital data stream broadcast parallel to the traffic announcement.

EP 0 459 360 describes an RDS radio receiver with a device known to seek alternative frequencies currently worth receiving. RDS radio receivers with only one receiving section must Deterioration in reception conditions on alternative frequencies fall back on their quality assessment at the time of switching is out of date. The many disadvantages of the one-receiver concept to bypass an RDS radio with two Receiving parts described, which with the help of a background receiver Reception quality of alternative frequencies continuously monitored and in a background memory empirically one arranged according to reception quality List of receivable RDS frequencies with and without Traffic announcements from the area of action of the mobile receiver builds. When receiving an RDS radio program without Traffic announcements can traffic announcements on other frequencies same broadcaster will be shown automatically.

The disadvantage here is that for the background receiver required effort is very high. In addition, with a very rapid change of reception conditions for the mobile receiver, such as a tunnel on the highway, also a Background receivers often search for several seconds do not avoid.

EP 0 443 501 describes an RDS radio receiver with a device known for accelerated finding of alternative frequencies. For the Quick build up of a list of alternative frequencies to one in the RDS station search found reception frequency becomes a facility with which has already been tested and confirmed in its reception quality Frequencies that use the same PI code, e.g. B. in the program memory of Device are stored, can be transferred directly to the main memory.

EP 0 428 866 describes a method for suppressing Channel changes in the event of local interference in RDS receivers are known. With RDS car radios, a station search is carried out automatically, if the reception quality drops below a predetermined limit and also the alternative frequencies cannot be received in sufficient quality or if there are no alternative frequencies, as in local stations is the case. In the event of short-term local malfunctions Suppressing station search is done after checking the alternative Frequencies no search started, even if these are not worth receiving but the last tuned station is tuned in again and for one received predetermined time.

This method has the disadvantage that in the event of a signal failure for there is no reception signal for a certain time and then there is again a long search is required. The length of time Noise is output or the output is muted, extended yourself in addition.

From DE 92 18 025 U1 an arrangement for limiting the Switching behavior of an RDS radio receiver in EON mode known. The frequency transmitted in EON mode Traffic information station is not automatically in a traffic announcement set by the receiver, but it is the reception field strength of the Program determined to receive a traffic announcement should be switched over briefly and only with sufficient field strength also switched to this program.

The disadvantage here is that it is almost in the event of a large signal loss all frequencies takes a long time until a received signal does not poor reception quality is determined and until then no signal or Noise is output.

From PAKNALL, S .: Extended information about others Program chains (EON). In: Broadcast communications Year 35 (1991) Issue 1, pages 17 to 22, XP 000224945 is a Procedure for changing the reception frequency in the event of a deterioration in reception in an RDS car radio with EON function known.

Long tunnels are usually equipped with a special one for radio coverage Filling transmitter equipped. This is then due to the large cost usually only one, which can also be received outside the tunnel Traffic program broadcast.

Is the car radio on a different program than the one broadcast in the tunnel synchronized, its receipt is entered after entering the tunnel mostly impossible due to the reduced field strength. A conventional one RDS car radio then tries to save the saved alternatives Frequencies for this program, which previously with the RDS signal were transferred to synchronize. However, this fails because in the tunnel this program is not broadcast. Then a conventional one RDS car radio perform a complete search and the Program memory with the programs with the highest field strength new occupy. Only then would the program sent in the tunnel be received become.

This has the disadvantages that it takes a long time to again a receivable station is set and on the other hand the Memory allocation was completely changed.

It is therefore the object of the present invention to provide one To design radio receivers such that in the event of a signal failure of the currently received program using all existing ones Information is synchronized as quickly as possible to a new program and therefore only a brief signal dropout should occur a storage of the available alternative frequencies of the new one Program can be suppressed.

This object is achieved in that in the event of a signal failure in received program is first determined whether a successful Switching to one of the saved alternative frequencies is possible. If a change is not possible due to insufficient field strength, the frequencies from the entire transmission frequency range temporarily stored, in which a minimum field strength is detected can and these frequencies are transmitted with those in EON mode Frequencies compared for traffic programs. At a The receiver is synchronized to this frequency.

Alternatively, only the frequencies stored in the EON list can be used set and the received signal can be checked for its field strength.

It is advantageous that in the event of a brief drop in field strength, such as that of him typically occurs when passing through a tunnel, using the EON list with Transmission frequencies for traffic programs quickly on Traffic program is changed without, in one time consuming programming process, the memory for alternative Frequencies is reassigned. The ones already available for the RDS signal Modules for RDS decoding, control of the receive modules and storage of the reception frequencies in the EON list or as alternative frequencies can be used.

In an advantageous embodiment, the Receiver synchronized again to the previous reception frequency and the field strength is detected. As soon as this is above a minimum field strength, is again on one of the transmission frequencies of the previously received Program changed.

The invention is explained and described in more detail below.

It is assumed below that the user with a Car, which has the radio receiver according to the invention, in one Tunnel is entering. The car radio attaches it to the entrance to a tunnel recognized that it tried on previously transmitted with the RDS signal and im Car radio to switch stored alternative frequencies and this fails several times due to insufficient field strength of the received signal. Because this reception situation that relatively quickly one or more Programs can no longer be received, almost exclusively in an extreme shading area such as a tunnel or a deep one Street canyon occurs, the recipient of it can be a relatively reliable one Perform detection.

Then the entire transmission frequency range from Receiver searched and the frequencies at which one Minimum field strength is received using the EON list frequencies compared that were previously transmitted with the EON signal. As soon as one If a match occurs, a traffic program is found and the receiver synchronizes to this frequency.

Alternatively, the receiver can also selectively set the frequencies that are in the EON list for receivable traffic programs is included, and determine whether a minimum field strength is received. Is that the case, a traffic program is found.

There is no storage of new frequencies since this is assumed is that the frequency found is only needed for a short time for reception and after leaving the shading area the previous program should be set again.

In order to recognize the leaving of the shading area, in the original reception frequency or the in the AF list entered alternative frequencies set to to detect the field strength. As soon as a minimum field strength at a of these frequencies is detected, is returned to the original set frequency or its alternative frequency changed. The Time intervals can be selected so that signal pauses are used to briefly switch to the original frequency. The Receiver is muted during this.

Claims (3)

1. Method of switching the broadcasting programme during a short-term reception disturbance, wherein an EON list comprising transmission frequencies of traffic broadcasting stations and an AF list comprising alternative transmission frequencies are transmitted with the RDS data and wherein attempts are made to switch to one of the alternative transmission frequencies if the field strength of the incoming signal drops below a minimum field strength, wherein, after a plurality of futile attempts to switch to one of the alternative transmission frequencies, the transmission frequency range is searched for signals that have at least a minimum field strength, characterized in that the transmission frequencies of said signals are compared with the transmission frequencies stored in the EON list, and in that said transmission frequency is selected in the event of a match.
2. Method of switching the broadcasting programme during a short-term reception disturbance, wherein an EON list comprising transmission frequencies of traffic broadcasting stations and an AF list comprising alternative transmission frequencies are transmitted with the RDS data and wherein attempts are made to switch to one of the alternative transmission frequencies if the field strength of the incoming signal drops below a minimum field strength, characterized in that, after a plurality of futile attempts to switch to one of the alternative transmission frequencies, successive transmission frequencies stored in the EON list are selected by the receiver, in that the field strength is determined in each case, and in that the transmission frequency remains selected if the field strength at said frequency exceeds a minimum field strength.
3. Method according to Claim 1 or 2, characterized in that the transmission frequency previously selected is stored, in that the field strength at the transmission frequency previously selected is determined at certain time intervals, and in that the transmission frequency previously selected is selected and retained if the field strength determined exceeds a minimum field strength or else the frequency selected from the EON list is retained.