JP4728973B2 - FM transmitter, electronic device using the same, and automatic channel selection method - Google Patents

Description

  The present invention relates to an FM transmitter that supports RDS (Radio Data System) or RBDS (Radio Broadcast Data System).

  In recent years, European FM radio stations and US radio broadcast stations have transmitted additional information such as text as European RDS (Radio Data System) or US RBDS (Radio Broadcast Data System) information. . By using RDS / RBDS, various information such as the name of a broadcast station currently received and the genre of music can be used in a car radio receiver (Patent Documents 1 and 2).

  On the other hand, FM transmitters that convert an audio signal into a stereo composite signal, perform frequency modulation using a frequency modulator, and output the same are known (Patent Documents 3 to 5). If an FM transmitter is used, an audio signal can be transmitted without going through a wiring such as an RCA cable. Therefore, the FM transmitter can be used for transmission of a signal between a car audio CD changer and a head unit. In recent years, hard disk audio devices, memory audio devices, and mobile phone terminals with music playback functions have been remarkably widespread. Music data stored in such small electronic devices can be played from speakers such as stationary audio components. FM transmitters are also used for such applications.

JP-A-8-256135 JP-A-8-191232 Japanese Patent Laid-Open No. 9-069729 JP-A-10-013370 JP-A-9-312588 NATIONAL RADIO SYSTEMS COMMITTEE, “UNITED STATES RBDS STANDARD”, USA, April 9, 1998

  If data in the RDS / RBDS format can be loaded not only on the broadcast wave from the broadcast station but also on the radio wave transmitted by the FM transmitter, the data can be used conveniently on the receiver side.

  The present invention has been made in view of these problems, and a comprehensive object thereof is to provide an FM transmitter capable of transmitting data in the RDS / RBDS format.

  One embodiment of the present invention relates to an FM transmitter capable of transmitting a signal conforming to an RDS (Radio Data System) or RBDS (Radio Broadcast Data System) format. This FM transmitter uses an interface unit that receives data to be transmitted from an external host processor via a predetermined bus, a memory that stores data received by the interface unit, and data that is stored in the memory. A data generation unit that generates group data that conforms to the format, and a frequency modulator that frequency-modulates and outputs the group data generated by the data generation unit.

  According to this aspect, the host processor may generate only the data to be transmitted and output it via the bus without being aware of the RDS / RBDS format. In RDS / RBDS, the same data may be repeatedly transmitted. However, data transmission from the host processor to the FM transmitter may be performed only once, and the power consumption of the circuit can be reduced.

  The data to be transmitted received by the interface section includes “broadcast station name”, “RT (Radio Text: hereinafter referred to as character information)”, “music / speech (music / speech)”, “program type”, “PI (program identification). ) "May be included.

It may also operate in a general-purpose mode in which RDS or RBDS format data generated in the host processor is received, a check word is added thereto, and output.
In this case, when the FM transmitter is connected to a host processor capable of generating data in the RDS / RBDS format, the data generated by the host processor can be used effectively.

  The FM transmitter of an aspect may be integrated on a single semiconductor substrate. “Integrated integration” includes the case where all of the circuit components are formed on a semiconductor substrate and the case where the main components of the circuit are integrated. A resistor, a capacitor, or the like may be provided outside the semiconductor substrate. By integrating these circuits as one LSI, the circuit area can be reduced.

  Another embodiment of the present invention is an electronic device. This electronic device is connected to a host processor that generates additional data other than an audio signal, and the host processor via a predetermined bus, receives the additional data, converts it to RDS or RBDS format, Any of the above-mentioned FM transmitters that perform frequency modulation and output.

  According to this aspect, since the number of data transmission / reception between the host processor and the electronic device can be reduced, the power consumption of the electronic device can be reduced.

  It should be noted that any combination of the above-described constituent elements, and those obtained by replacing constituent elements and expressions of the present invention with each other among methods, apparatuses, systems, etc. are also effective as embodiments of the present invention.

  According to the present invention, data in the RDS / RBDS format can be transmitted from the FM transmitter.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, “the state in which the member A and the member B are connected” means that the member A and the member B are physically directly connected, or the member A and the member B are in an electrically connected state. Including the case of being indirectly connected through other members that do not affect the above.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as an electrical connection. The case where it is indirectly connected through another member that does not affect the state is also included.

  FIG. 1 is a block diagram showing an overall configuration of an electronic device 200 equipped with an FM transmitter 100 according to an embodiment of the present invention. The electronic device 200 is, for example, a mobile phone terminal, a radio receiver, or a silicon audio player, and has an audio playback function. The reproduced audio signal can be output from an electroacoustic conversion element itself such as a speaker or an earphone included in the electronic apparatus 200 itself. In addition to this, the electronic device 200 can modulate the frequency of an audio signal and transmit it as a radio wave to the outside in order to enable audio reproduction with higher sound quality. The user can receive the transmitted signal by an external audio player and reproduce it with higher sound quality.

  The FM transmitter 100 according to the present embodiment can transmit character data in addition to audio data. For this purpose, the FM transmitter 100 and the host processor 120 generate a signal compliant with RDS / RBDS. Note that when RDS / RBDS is written, it means either one or both.

  The electronic device 200 includes a sound source 110, a host processor 120, an FM transmitter 100, and an antenna 112. The sound source 110 and the host processor 120 may be the same IC.

  The sound source 110 outputs an audio signal S1. For example, the audio signal S1 may be a signal obtained as a result of receiving and demodulating a broadcast wave, or may be a signal obtained by reproducing data stored in a memory, and its generation method is not limited. The sound source 110 and the FM transmitter 100 are connected by a bus 114 having a predetermined format. For example, the bus 114 is an I2S bus. In this case, the audio signal S1 is transmitted as serial data between the sound source 110 and the FM transmitter 100.

  The FM transmitter 100 receives the audio signal S1 from the sound source 110. The FM transmitter 100 includes an interface unit 20, a stereo modulator 22, a frequency modulator 24, a power amplifier 26, a memory 10, and a data generation unit 12, and is integrated as a function IC (Integrated Circuit) on a single semiconductor substrate. Has been. FIG. 1 shows only main circuit blocks extracted, and other blocks are omitted as appropriate.

  The interface unit 20 receives the audio signal S <b> 1 from the sound source 110 via the input terminal 102. The interface unit 20 receives the audio signal S 1 and outputs it to the stereo modulator 22. The stereo modulator 22 performs stereo modulation on the audio signal S1 to generate a stereo composite signal S2.

  Details of RDS / RBDS are described in detail in Non-Patent Document 1 and the like, so please refer to them. The host processor 120 outputs data D1 to be transmitted as RDS / RBDS. The data D1 itself to be transmitted is not text data in the RDS / RBDS format but only text data. The host processor 120 and the FM transmitter 100 are connected by a bus 116 having a predetermined format. For example, the bus 116 is an I2C bus. The interface unit 20 receives the data D1 through the bus 116 and the input terminal 104. Data D1 is additional data to be transmitted from the antenna 112 together with the audio signal S1. Further, it is desirable that data transmission from the host processor 120 to the FM transmitter 100 is performed only at a timing at which RDS / RBDS data to be transmitted from the antenna 112 is changed. In this case, the contents of the memory 10 are updated only when the data is changed.

  The memory 10 is composed of a register or the like and stores data D1 received by the interface unit 20. In the RDS / RBDS format, the same data is repeatedly transmitted. The host processor 120 collectively outputs data as a repetition unit to the FM transmitter 100.

For example, the data D1 is
1) Broadcaster name 2) Text information (Radio Text)
3) Music / Voice 4) Program type 5) PI (Program identification)
Including at least one of or a combination thereof. 1) includes “broadcasting station name” as text data. “Music / voice” in 3) indicates whether the data being broadcast is music or voice. The “program type” in 4) indicates the genre of data being broadcast. For example, “0 no definition”, “1 news”, “3 sports”, “14 jazz”, “15 classic”, and the like are set. The PI of 5) is a code that enables the receiver to identify the country.

  The data generation unit 12 appropriately rearranges the data D1 stored in the memory 10, and generates group data G1 that conforms to the RDS / RBDS format. The group data G1 is generated every predetermined timing, for example, every 87.6 ms. Accordingly, the group data G1 is repeatedly output to the adder 28 every 87.6 ms. The adder 28 adds the stereo composite signal S2 from the stereo modulator 22 and the group data G1. The frequency modulator 24 frequency-modulates the carrier wave using the group data G1 as a modulation signal. The modulated signal output from the frequency modulator 24 is amplified by the power amplifier 26 and output to the antenna 112 via the output terminal 106 and a matching circuit (not shown). The antenna 112 transmits frequency-modulated data.

FIG. 2 shows the format of the RDS group data G1. The group data 40 (G1) is composed of 104 bits. The group data G1 is generated every 87.6 ms and output from the data generation unit 12. Group data G1 includes four blocks 41-44. Each block is composed of 26 bits and includes a 16-bit information word 50 and a 10-bit check word 52. The information word of the first block 41 includes a PI code.
The information word includes a 4-bit (A3 to A0) group type code 54, a 1-bit (B0) version code 60, a 1-bit (TP) traffic program identification code 62, and a 5-bit (PT4 to PT0) program type code. 64.
A group type code 54 for designating the use of the group is assigned to the head of the second block 42 of each group. The program type code 64 and the traffic program identification code 62 are assigned to predetermined positions in the second block 42 of each group.

  The check word includes 10 bits, and is a bit for detecting and correcting an error caused by transmission on the transmission side and the reception side. The offset is data indicating the number of the block that includes the offset. The check word is generated according to a predetermined rule defined by the standard.

  The remaining data to be transmitted is assigned to the remaining bits. Two characters of data can be transmitted per block. The data generation unit 12 in FIG. 1 refers to the memory 10 every predetermined timing, that is, every 87.6 ms, and generates group data G1 conforming to the format in FIG.

The FM transmitter 100 configured as described above has the following effects.
First, it is not necessary for the host processor 120 to generate RDS / RBDS format data. Therefore, a conventional host processor can be used, and data to be transmitted may be transmitted to the FM transmitter 100 using a conventional bus (for example, I2C).

  Further, as described above, data transmitted by RDS / RBDS includes data that is repeatedly transmitted for each block or group. Therefore, if RDS / RBDS data is generated in the host processor 120, all bits of the group data G1 that are repeatedly transmitted are generated, and 104 bits of data are generated every 87.6 ms (f = 1.19 kHz). It is necessary to transmit from the host processor 120 to the FM transmitter 100 every time via the 116. Whatever the format of the bus 116, power transmission occurs for data transmission therethrough. Therefore, in this method, the same data is retransmitted each time for the bits to be transmitted in duplicate, so that useless power is generated. On the other hand, according to the FM transmitter 100 according to the present embodiment, data to be transmitted is transmitted from the host processor 120 to the FM transmitter 100 in a lump and is held in the memory 10. As a result, data transmission after the next time is not required, and redundant data transfer is reduced, so that power consumption is reduced.

Further, from the host processor 120,
1) Broadcaster name 2) Text information 3) Music / voice 4) Program type 5) PI (program identification)
The data that can be generated in the FM transmitter 100 such as a check word is not transmitted from the host processor 120 to the FM transmitter 100, so that the FM transmitter 100 and the host processor 120 can further transmit data. The amount of data transmitted can be reduced.

  The host processor 120 performs overall processing of the entire electronic device 200. Therefore, when RDS / RBDS data is generated every 87.6 ms and transmitted to the FM transmitter 100, the processing capability of the host processor 120 is occupied, which is not desirable. In this embodiment, the load on the host processor 120 can be reduced.

  Further, data transmission through the bus 116 may generate noise, adversely affect stereo modulation and frequency modulation, and deteriorate the characteristics of the FM transmitter 100. Since the number of data transmissions and the amount of data can be reduced, the characteristics of the FM transmitter can also be improved.

If the host processor 120 can generate data in the RDS / RBDS format, the FM transmitter 100 may be implemented with a general-purpose mode described below.
The host processor 120 generates RDS / RBDS format data therein and outputs the data to the FM transmitter 100 via the bus 116. The data in the RDS / RBDS format at this time does not include a check word. The data generation unit 12 adds a check word to the RDS / RBDS format data received from the host processor 120 and outputs the check word to the adder 28.
If the general-purpose mode is implemented, various data other than the data described above can be transmitted. Further, although data transmission via the bus 116 occurs every 87.6 ms of transmission timing, check data is not transmitted, so that power consumption can be reduced.

  Although the present invention has been described based on the embodiments, the embodiments merely illustrate the principle and application of the present invention, and the embodiments are intended to include the idea of the present invention defined in the claims. Many modifications and changes in arrangement are possible within the range not leaving.

It is a block diagram which shows the whole structure of the electronic device carrying the FM transmitter which concerns on embodiment of this invention. It is a figure which shows the format of the group data of RDS.

Explanation of symbols

  10 memory, 12 data generation unit, 20 interface unit, 22 stereo modulator, 24 frequency modulator, 26 power amplifier, 28 adder, 100 FM transmitter, 102 input terminal, 104 input terminal, 106 output terminal, 114 bus, 116 buses, 110 sound sources, 112 antennas, 120 host processors, 200 electronic devices.

Claims (5)

An FM transmitter capable of transmitting a signal compliant with RDS (Radio Data System) or RBDS (Radio Broadcast Data System) format,
An interface unit for receiving data to be transmitted from an external host processor via a predetermined bus;
A memory for storing data received by the interface unit;
A data generation unit that generates group data compliant with the format using data stored in the memory;
A frequency modulator for frequency-modulating and outputting the group data generated by the data generation unit for each predetermined period ;
Equipped with a,
The host processor is configured to transmit the same data that the FM transmitter should repeatedly transmit over a plurality of cycles to the interface unit only once instead of every cycle,
The FM transmitter, wherein the data generator generates the group data by repeatedly reading out the same data stored in the memory over a plurality of periods .   2. The FM according to claim 1, wherein the data to be transmitted received by the interface unit includes at least one code of a broadcasting station name, character information, music / voice, program type, and PI (program identification). Transmitter.   3. The FM transmitter according to claim 1, wherein the FM transmitter operates in a general-purpose mode in which RDS or RBDS format data generated in the host processor is received and a check word is added to the data.   The FM transmitter according to claim 1, wherein the FM transmitter is integrated on a single semiconductor substrate. A host processor that generates additional data other than audio signals;
3. The FM transmitter according to claim 1, wherein the FM transmitter is connected to the host processor via a predetermined bus, receives the additional data, converts the data into an RDS or RBDS format, and frequency-modulates the output.
An electronic device comprising:

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