阅读说明：本技术 检测声音中频信号的制式的电路及方法 (Circuit and method for detecting system of sound intermediate frequency signal ) 是由 吴佳哲 于 2020-05-28 设计创作，主要内容包括：本发明揭露了一种检测声音中频信号的制式的电路,其包括有一中频至基频转换电路、一检测电路以及一解调/解码器。在该电路的操作中,该中频至基频转换电路用以对该声音中频信号进行处理以产生一主信号以及一子信号；该检测电路用以根据该子信号是否具有一导频信号、或是是否具有一数字帧,以判断该声音中频信号是否属于一第一制式或是一第二制式,并据以产生一检测结果；以及该解调/解码器用以根据该检测结果来至少对该主信号进行解调/解码操作,以产生一输出声音信号。(The invention discloses a circuit for detecting the standard of sound intermediate frequency signals, which comprises an intermediate frequency-to-base frequency conversion circuit, a detection circuit and a demodulator/decoder. In operation of the circuit, the IF-to-baseband conversion circuit is configured to process the IF audio signal to generate a main signal and a sub-signal; the detection circuit is used for judging whether the sound intermediate frequency signal belongs to a first system or a second system according to whether the sub-signal has a pilot signal or a digital frame, and generating a detection result; and the demodulator/decoder is used for at least demodulating/decoding the main signal according to the detection result so as to generate an output sound signal.)

1. A circuit for detecting the system of sound intermediate frequency signals comprises:

an intermediate frequency to fundamental frequency conversion circuit for processing the sound intermediate frequency signal to generate a main signal and a sub-signal;

the detection circuit is used for judging whether the sound intermediate frequency signal belongs to a first system or a second system according to whether the sub-signal has a pilot signal or whether the sub-signal has a digital frame, and generating a detection result according to the judgment result; and

the demodulator/decoder is coupled to the IF-to-baseband conversion circuit and the detection circuit, and is configured to perform a demodulation/decoding operation on at least the main signal according to the detection result to generate an output audio signal.

2. The circuit of claim 1, wherein the detection circuit comprises:

a pilot signal demodulator for demodulating the sub-signal to produce a demodulated signal;

a specific decoder for decoding the sub-signal to generate a decoded signal; and

a determining unit, configured to determine whether the sound intermediate frequency signal belongs to the first standard or the second standard according to whether the demodulated signal includes the pilot signal and whether the decoded signal includes the digital frame, so as to generate the detection result.

3. The circuit according to claim 2, wherein if the demodulated signal includes the pilot signal, the determining unit determines that the sound if signal belongs to the first system; and if the decoded signal comprises the digital frame, the judging unit judges that the sound intermediate frequency signal belongs to the second system.

4. The circuit of claim 1, 2 or 3, wherein the detection circuit determines whether the intermediate frequency audio signal belongs to the first standard, the second standard, or a third standard different from the first standard and the second standard according to whether the sub-signal has the pilot signal or the digital frame, and according to the strengths of the main signal and the sub-signal, and generates the detection result accordingly.

5. The circuit of claim 4, wherein the first standard is a2 standard, the second standard is near real-time companded audio multiplex broadcasting standard, and the third standard is frequency-modulated mono-channel standard.

6. The circuit of claim 1, wherein the detection circuit comprises:

a pilot signal demodulator for demodulating the sub-signal to produce a demodulated signal; and

a determining unit, configured to determine whether the sound intermediate frequency signal belongs to the first standard or the second standard according to whether the demodulated signal includes the pilot signal and the strength of the sub-signal, so as to generate the detection result.

7. The circuit of claim 6, wherein if the demodulated signal includes the pilot signal, the determining unit determines that the sound if signal belongs to a2 standard; and if the demodulated signal does not include the pilot signal and the intensity of the sub-signal is higher than the critical value, the judging unit judges that the sound intermediate frequency signal belongs to a near real-time companding audio multi-path broadcasting system.

8. The circuit of claim 1, wherein the detection circuit comprises:

a specific decoder for decoding the sub-signal to generate a decoded signal; and

a determining unit, configured to determine whether the sound intermediate frequency signal belongs to the first standard or the second standard according to whether the decoded signal includes the digital frame and the strength of the sub-signal, so as to generate the detection result.

9. The circuit of claim 8, wherein if the decoded signal includes the digital frame, the determining unit determines that the if-audio signal belongs to a near real-time companded audio multiplex broadcasting system; and if the decoded signal does not include the digital frame and the intensity of the sub-signal is higher than the threshold value, the determining unit determines that the sound intermediate frequency signal belongs to the A2 standard.

10. A method for detecting the standard of sound intermediate frequency signals comprises the following steps:

processing the sound intermediate frequency signal to generate a main signal and a sub-signal;

judging whether the sound intermediate frequency signal belongs to a first system or a second system according to whether the sub-signal has a pilot signal or whether the sub-signal has a digital frame, and generating a detection result according to the judgment result; and

at least the main signal is demodulated/decoded according to the detection result to generate an output sound signal.

Technical Field

The invention relates to a circuit and a method for detecting the standard of a sound intermediate frequency signal.

Background

In an analog television system, audio signals share several types of standards: frequency modulated MONO (FM-MONO), Near real time Companded Audio Multiplex (NICAM) format, a2, Broadcast Television Systems Committee (BTSC), amplitude modulated MONO (AM-MONO). Conventionally, the method for detecting the system type of the if signal is performed by detecting the strength of the if signal at different frequencies, however, since the if signal is easily affected by noise, the strength of the if signal at different frequencies is used as the determination criterion of the system type, which is prone to error, and affects the subsequent decoding/demodulation operations.

Disclosure of Invention

Therefore, an objective of the present invention is to provide a circuit and a method for detecting a format of an intermediate frequency audio signal, which can accurately detect the format type of the intermediate frequency audio signal to solve the problems described in the prior art.

In one embodiment of the present invention, a circuit for detecting a standard of an intermediate frequency audio signal is disclosed, which includes an intermediate frequency to baseband frequency conversion circuit, a detection circuit and a demodulator/decoder. In operation of the circuit, the IF-to-baseband conversion circuit is configured to process the IF audio signal to generate a main signal and a sub-signal; the detection circuit is used for judging whether the sound intermediate frequency signal belongs to a first system or a second system according to whether the sub-signal has a pilot signal (pilot signal) or a digital frame (digital frame), and generating a detection result; and the demodulator/decoder is used for at least demodulating/decoding the main signal according to the detection result so as to generate an output sound signal.

In another embodiment of the present invention, a method for detecting a standard of an intermediate frequency audio signal is disclosed, which comprises the following steps: processing the sound intermediate frequency signal to generate a main signal and a sub-signal; judging whether the sound intermediate frequency signal belongs to a first system or a second system according to whether the sub-signal has a pilot signal or a digital frame, and generating a detection result; and demodulating/decoding at least the main signal according to the detection result to generate an output sound signal.

Drawings

Fig. 1 is a schematic diagram of a circuit for detecting a standard of an if signal according to an embodiment of the present invention.

Fig. 2 shows a schematic diagram of a sound intermediate frequency signal having a frequency-modulated mono system in the B, G system.

Fig. 3 shows a schematic diagram of a sound intermediate frequency signal having a2 standard in an B, G system.

Fig. 4 shows a schematic diagram of a sound intermediate frequency signal having a NICAM system in the B, G system.

Fig. 5 is a flowchart of a method for detecting a standard of an if audio signal according to an embodiment of the present invention.

Detailed Description

Fig. 1 is a diagram of a circuit 100 for detecting a system of an if signal according to an embodiment of the invention. As shown in fig. 1, the circuit 100 includes an if-to-baseband conversion circuit 110, a detection circuit 120 and a demodulator/decoder 130, wherein the detection circuit 120 includes a determination unit 122, a pilot signal demodulator 124 and a specific decoder 126, and the determination unit 122 includes an energy intensity detection circuit 123. In the present embodiment, the circuit 100 is applied in an analog television system, and the circuit 100 can be used to detect whether the received sound intermediate frequency signal belongs to a frequency modulation MONO (MONO) system, a2 system or a NICAM system. Fig. 2 shows a schematic diagram of a sound intermediate frequency signal having a frequency-modulated mono system in the B, G system, wherein the sound intermediate frequency signal has only a main signal, and the main signal has a center frequency of 5.5MHz and a bandwidth of about 100 kHz. Fig. 3 shows a schematic diagram of an acoustic intermediate frequency signal having a2 standard in an B, G system, wherein the acoustic intermediate frequency signal has a main signal and sub-signals, and the main signal having a higher intensity has a center frequency of 5.5MHz and a bandwidth of about 100kHz, and the sub-signal having a lower intensity has a center frequency of 5.74MHz and a bandwidth of about 100 kHz. Fig. 4 shows a schematic diagram of an acoustic intermediate frequency signal having a NICAM system in the B, G system, wherein the acoustic intermediate frequency signal has a main signal and sub-signals, and the main signal having a higher intensity has a center frequency of 5.5MHz and a bandwidth of about 100kHz, and the sub-signal having a lower intensity has a bandwidth of about 510 kHz. It should be noted that the contents of fig. 2 to 4 are only for convenience of the following description and are not meant to be a limitation of the present invention, and in other systems, such as DK system and I system, the main signal and the sub signal may have different center frequencies.

In operation of the circuit 100, the if-to-bb conversion circuit 110 receives the sound if signal and down-converts the sound if signal to a baseband (base) to generate the main signal D _ M and the sub-signal D _ S. In the present embodiment, the main signal D _ M corresponds to the signal content with the center frequency of 5.5MHz and the bandwidth of about 100kHz in fig. 2 to fig. 4, and the sub-signal D _ S may correspond to the signal content with the center frequency of 5.74MHz and the bandwidth of about 100kHz shown in fig. 3, or the signal content with the bandwidth of 510kHz shown in fig. 4, and it should be noted that the sub-signal D _ S does not necessarily have valid content (for example, there is no substantial content in the case of the fm mono system). Then, the detection circuit 120 detects the main signal D _ M and the sub-signal D _ S to determine whether the if signal belongs to the fm mono system, the a2 system or the NICAM system. Specifically, since the main signal has higher intensity and the sub-signal has lower intensity in the systems shown in fig. 2, 3 and 4, the energy intensity detecting circuit 123 can determine whether the sound if signal is possibly in the systems shown in fig. 2 to 4 by detecting whether the power/intensity of the main signal D _ M generated by the if-to-baseband converting circuit 110 is higher than a first threshold value; and it can also be determined whether the sound if signal is likely to be in the standard shown in fig. 2 to 4 by detecting whether the power/strength of the main signal D _ M generated by the if-to-baseband conversion circuit 110 is higher than a second threshold. However, the detection result of the energy intensity detection circuit 123 may have errors due to the influence of noise, and therefore, the present embodiment additionally uses the pilot signal demodulator 124 and the specific decoder 126 to accurately determine which system the sound if signal belongs to in fig. 2 to 4.

The pilot signal demodulator 124 is specifically configured to perform a demodulation operation (e.g., demodulation) on the sub-signal D _ S to determine whether a pilot signal is included in the sub-signal D _ S, so as to determine whether the sound intermediate frequency signal is of the a2 format. Specifically, in the a2 format shown in fig. 3, the sub-signal includes information of stereo, binaural, or other audio modes, and the sub-signal using frequency modulation is added with a pilot signal using amplitude modulation. Therefore, the result generated by the pilot signal demodulator 124 (i.e., whether the pilot signal is included in the sub-signal D _ S) can be used to determine whether the sound intermediate frequency signal is of the a2 standard.

The specific decoder 126 may be a NICAM decoder, which is used to perform a decoding operation (e.g., content decoding) on the sub-signal D _ S to determine whether a digital frame is included in the sub-signal, so as to determine whether the sound intermediate frequency signal is NICAM. Specifically, in the NICAM format shown in fig. 4, the sub-signal includes a 728-bit digital frame, and the digital frame includes the following: an 8-bit Frame Alignment Word (FAW), a 5-bit handle (handle), 11-bit extra data, and channel data (64 × 11 bits), so that the specific decoder 126 can determine whether the sub-signal D _ S includes a digital Frame by decoding the sub-signal D _ S and detecting whether the Frame Alignment Word exists. As described above, the result generated by the specific decoder 126 (i.e., whether the sub-signal D _ S includes digital frames) can be used to determine whether the sound intermediate frequency signal is in the NICAM format.

In the present embodiment, the detection circuit 120 determines whether the sound if signal belongs to the fm mono system, the a2 system or the NICAM system according to whether the sub-signal has the pilot signal or the digital frame and the intensities of the main signal D _ M and the sub-signal D _ S, and generates the detection result accordingly. In detail, the determining unit 122 may determine whether the sound if signal is in the fm mono mode, the a2 mode or the NICAM mode according to the output results of the energy intensity detecting circuit 123, the pilot signal demodulator 124 and the specific decoder 126. Specifically, if the energy intensity detecting circuit 123 determines that the power/intensity of the main signal D _ M generated by the if-to-baseband converting circuit 110 is higher than the first threshold, the result generated by the pilot signal demodulator 124 indicates that the sub-signal D _ S does not include the pilot signal, and the result generated by the specific decoder 126 indicates that the sub-signal D _ S does not include the digital frame, the determining unit 122 may determine that the audio if signal is in the fm mono mode; if the energy intensity detecting circuit 123 determines that the power/intensity of the sub-signal D _ S generated by the if-to-baseband converting circuit 110 is higher than the second threshold value, and the result generated by the pilot signal demodulator 124 indicates that the sub-signal D _ S includes the pilot signal, the determining unit 122 may determine that the sound if signal is of a standard a 2; if the energy intensity detecting circuit 123 determines that the power/intensity of the sub-signal D _ S generated by the if-to-baseband converting circuit 110 is higher than the second threshold and the specific decoder 126 indicates that the sub-signal D _ S includes digital frames, the determining unit 122 may determine that the audio if signal is NICAM.

The determining unit 122 transmits the determination result to the demodulator/decoder 130, so that the demodulator/decoder 130 performs corresponding setting to demodulate/decode the main signal D _ M and the sub-signal D _ S to generate an output audio signal, wherein the output audio signal may be a Pulse-Code Modulation (PCM) signal including left and right channels. It should be understood that, when the determining unit 122 determines that the sound if signal is in the fm mono system, the demodulator/decoder 130 only demodulates/decodes the main signal D _ M to generate the output sound signal since the sound if signal has no substantial sub-signal content; when the determining unit 122 determines that the audio if signal is in the a2 mode or the NICAM mode, the demodulator/decoder 130 demodulates/decodes the main signal D _ M and the sub signal D _ S to generate the output audio signal.

In the above embodiment, the pilot signal demodulator 124 and the specific decoder 126 are independent from the demodulator/decoder 130, i.e. the sub-signal D _ S is demodulated and decoded to determine the a2 standard and the NICAM standard, and then the demodulator/decoder 130 is controlled to perform the appropriate operation. Since the detecting unit 120 of the present embodiment can accurately determine the system of the if signal, the whole operation of the circuit 100 can be prevented from being wrong.

In one embodiment shown in fig. 1, the system of the sound if signal is determined by considering the detection results of the energy intensity detection circuit 123 for the main signal D _ M and the sub-signal D _ S, however, the invention is not limited thereto. For example, if the result generated by the pilot signal demodulator 124 indicates that the sub-signal D _ S includes the pilot signal, the determining unit 122 can directly determine that the sound intermediate frequency signal belongs to the a2 standard; if the specific decoder 126 generates a result indicating that the sub-signal D _ S includes digital frames, the determining unit 122 can directly determine that the sound if signal is in the NICAM format. Such variations in design are intended to fall within the scope of the present invention.

In another embodiment shown in fig. 1, the detection circuit 120 includes a pilot signal demodulator 124 for accurately determining whether the sound if signal conforms to the a2 standard, and a specific decoder 126 for accurately determining whether the sound if signal conforms to the NICAM standard. In another embodiment, the detection circuit 120 may only include the pilot signal demodulator 124 for accurately determining whether the sound if signal conforms to the a2 standard, and the determination of whether the sound if signal conforms to the NICAM standard may be performed by the energy intensity detection circuit 123. For example, if the energy intensity detecting circuit 123 determines that the power/intensity of the sub-signal D _ S generated by the if-to-baseband converting circuit 110 is higher than the second threshold value, but the result generated by the pilot signal demodulator 124 indicates that the sub-signal D _ S does not include the pilot signal, the determining unit 122 may determine that the sound if signal is in NICAM format. In another embodiment, the detection circuit 120 may only include a specific decoder 126 for accurately determining whether the sound if signal conforms to the NICAM standard, but the determination of whether the sound if signal conforms to the a2 standard may be performed by the energy intensity detection circuit 123. For example, if the energy intensity detecting circuit 123 determines that the power/intensity of the sub-signal D _ S generated by the if-to-baseband converting circuit 110 is higher than the second threshold value, but the specific decoder 126 indicates that the sub-signal D _ S does not include digital frames, the determining unit 122 may determine that the sound if signal is of the a2 standard.

Fig. 5 is a flowchart of a method for detecting a standard of an if audio signal according to an embodiment of the present invention. The procedure is as follows with reference to the description of the above embodiments.

Step 500: the process begins.

Step 502: the sound intermediate frequency signal is processed to generate a main signal and a sub-signal.

Step 504: according to whether the sub-signal has a pilot signal or a digital frame, whether the sound intermediate frequency signal belongs to a first system or a second system is judged, and a detection result is generated accordingly.

Step 506: at least the main signal is subjected to a demodulation/decoding operation based on the detection result to generate an output sound signal.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.

[ notation ] to show

100: circuit arrangement

110: intermediate frequency to base frequency conversion circuit

120: detection circuit

122: judging unit

123: energy intensity detection circuit

124: pilot signal demodulator

126: specific decoder

130: demodulation/decoder

500 to 506: step (ii) of

D _ M: principal signal

D _ S: sub-signals