PDM medium wave transmitter digital pulse width modulator adaptive to DRM

Abstract

The utility model belongs to the technical field of pulse width modulators, and discloses a PDM medium wave transmitter digital pulse width modulator adaptive to a DRM, which comprises a DRM adaptation board, and a digital audio processing circuit, a power amplification circuit, a power control signal generation circuit and an FPGA are installed on the DRM adaptation board. A DRM modulation and decoding module, a DDS, a pulse width modulation wave generator and a power control signal processing module are written into the FPGA, the digital audio processing circuit inputs processed audio to the DRM modulation and decoding module, the DRM modulation and decoding module is connected with the DDS, the DDS inputs an audio signal amplitude value to the pulse width modulation wave generator, and the power control signal processing module is connected with the DDS. The power control signal generation circuit inputs a power control signal to the power control signal processing module in the FPGA and converts the power control signal into a direct current signal, and the pulse width modulation wave generator converts an audio signal amplitude value and the direct current signal into a pulse signal and inputs the pulse signal into the power amplification circuit. The power amplification circuit carries out power amplification on the pulse signal and inputs the pulse signal into the transmitter, and the performance is stable.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of pulse width modulator, and relates to a PDM medium wave transmitter digital pulse width modulator suitable for DRM. BACKGROUND

[0002] The PDM (pulse width modulation) medium wave transmitter is a medium wave broadcast transmitter using pulse width modulation technology. The modulator mainly converts audio signals into pulse signals. The audio signal is a continuous analog signal, which contains various information of sound, such as frequency, amplitude, phase, etc. The amplitude of the audio signal reflects the loudness of the sound, and the frequency determines the pitch of the sound. The pulse signal is a discrete digital signal, which has the advantages of easy processing and strong anti-interference ability. In the digital broadcast system, the pulse signal can be efficiently encoded, modulated and demodulated through digital signal processing technology.

[0003] The existing modulator is usually realized by using analog circuit, which needs a large number of electronic components and complex circuit board lines, thereby increasing the volume and cost of the equipment, and making it difficult to troubleshoot and maintain. UTILITY MODEL CONTENT

[0004] In view of the deficiencies in the prior art, the utility model aims to provide a PDM medium wave transmitter digital pulse width modulator suitable for DRM, which solves the technical problems of increasing the volume and cost of the equipment, increasing troubleshooting and maintenance by using a large number of electronic components and complex circuits in the existing modulator in the prior art.

[0005] In order to achieve the above-mentioned purpose, the utility model adopts the following technical scheme:

[0006] The utility model provides a PDM medium wave transmitter digital pulse width modulator suitable for DRM, which comprises a digital audio processing circuit, a power amplification circuit, a power control signal generation circuit, a DRM adaptation board and an FPGA. The output end of the digital audio processing circuit and the power control signal generation circuit is connected with the input end of the FPGA, the output end of the FPGA is connected with the input end of the power amplification circuit, the output end of the power amplification circuit is connected with the transmitter, and the digital audio processing circuit, the power amplification circuit, the power control signal generation circuit and the FPGA are all installed on the DRM adaptation board.

[0007] Further, the FPGA is written with a DRM modulation and decoding module, a DDS, a pulse width modulation wave generator, and a power control signal processing module; an input end of the DRM modulation and decoding module is connected with the digital audio processing circuit, and an output end thereof is connected with the DDS; an input end of the power control signal processing module is connected with an output end of the power control signal generation circuit; output ends of the DDS and the power control signal processing module are both connected with an input end of the pulse width modulation wave generator; and an output end of the pulse width modulation wave generator is connected with an input end of the power amplifier circuit.

[0008] Further, the digital audio processing circuit comprises an industrial computer and a serial circuit, the industrial computer is installed with an upper computer, and a digital audio signal of the industrial computer is input into the serial circuit through DRM encoding processing of the upper computer; and the serial circuit is connected with the modulation and decoding of the DRM through a filter circuit.

[0009] Further, a serial module is further included, one end of the serial module is connected with the serial circuit, and the other end thereof is connected with the modulation and decoding of the DRM.

[0010] Further, the power amplifier circuit comprises a DC power amplifier circuit, a power triode amplifier circuit, a pulse signal anomaly detection circuit, and a signal amplitude detection circuit; a pulse signal output by the pulse width modulation wave generator is transmitted to input ends of the power triode amplifier circuit and the pulse signal anomaly detection circuit; output ends of the DC power amplifier circuit and the pulse signal anomaly detection circuit are connected with an input end of the power triode amplifier circuit; and the signal amplitude detection circuit performs anomaly detection on a pulse signal output by the power triode amplifier circuit.

[0011] Further, a digital filter is further included, one end of the digital filter is connected with the pulse width modulation wave generator, and the other end thereof is connected with an input end of the power amplifier circuit.

[0012] Further, the pulse width modulation wave generator has 1300 gears, a frequency of a pulse signal output by the pulse width modulation wave generator is 72Khz, and a pulse peak value of the pulse signal output by the pulse width modulation wave generator is 13V.

[0013] Further, a serial baud rate of the upper computer is 115200Bd, and there is one stop bit.

[0014] Further, the power control signal generation circuit comprises a power control hand / auto switching switch, a power control signal manual controller, a power control signal automatic controller, and a digital control signal processing circuit.

[0015] Further, the power control hand / auto switch is connected with one end of a power control signal manual controller or a power control signal automatic controller, the other end of the power control signal manual controller or the power control signal automatic controller is connected with a digital control signal processing circuit, and the digital control signal processing circuit is connected with the pulse width modulation wave generator.

[0016] Compared with the prior art, the power control hand / auto switch has the following beneficial technical effects:

[0017] The PDM medium wave transmitter digital pulse width modulator of the utility model, FPGA integrates multiple functions (such as counter, comparator, flip-flop, etc.) originally needing independent devices to one chip, remarkably reduces the quantity of components and parts required by the system, thereby reducing the complexity and cost of the system.

[0018] The PDM medium wave transmitter digital pulse width modulator of the utility model, the programmable gate array, the internal flip-flop and the lookup table design pulse width modulation wave generator replace multiple classified devices used by the existing pulse width modulator, have high integration degree and deep digitalization degree, and guarantee the stability and reliability during work.

[0019] The PDM medium wave transmitter digital pulse width modulator of the utility model, the digital audio processing circuit adopts the combination of the industrial computer and the upper computer to input the audio signal to the DRM adaptation board through the serial module, and compared with the existing audio input circuit, has better interface display and controllability, and is easy to operate by operating personnel.

[0020] The PDM medium wave transmitter digital pulse width modulator of the utility model, the FPGA receives serial port information, combines the digital audio signal with the power control signal according to the set SPWM algorithm, converts into the duty cycle value and controls the pulse width modulation wave generator to generate the corresponding duty cycle pulse signal, and compared with the existing analog pulse width modulator, has higher modulation linearity and stable performance and is not influenced by problems such as aging and temperature drift of discrete components.

[0021] The PDM medium wave transmitter digital pulse width modulator of the utility model adopts the hardware logic language, and has simple circuit structure, easy-to-expand function and easy-to-modify parameter. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structural diagram of the PDM medium wave transmitter digital pulse width modulator of the utility model;

[0023] Figure 2 It is a structural diagram of the digital audio processing circuit in the embodiment of the utility model;

[0024] Figure 3 A structure diagram of the power amplification circuit in the embodiment of the utility model;

[0025] Figure 4 A structure diagram of the power control signal generation circuit in the embodiment of the utility model. DETAILED DESCRIPTION

[0026] In order to make the personnel in the technical field better understand the utility model scheme, the technical scheme in the embodiment of the utility model will be described clearly and completely below in combination with the drawings in the embodiment of the utility model, obviously, the described embodiment is only a part of the embodiment of the utility model, rather than all the embodiments. Based on the embodiment in the utility model, all other embodiments obtained by the person skilled in the art without making creative labor should belong to the protection scope of the utility model.

[0027] Embodiment 1

[0028] The utility model relates to a PDM medium wave transmitter digital pulse width modulator suitable for DRM, including DRM adaptation board, digital audio processing circuit, power amplification circuit, power control signal generation circuit, FPGA, write DRM modulation and decoding module on FPGA, DDS, pulse width modulation wave generator, power control signal processing module, as Figure 1 Shown.

[0029] As Figure 2 Shown, digital audio processing circuit includes industrial computer, host computer and serial circuit connected in sequence, and industrial computer generates digital audio signal through host computer DRM encoding processing, and the encoded serial port signal is input to the serial circuit, and the serial circuit inputs the digital audio signal to the FPGA.

[0030] The serial port baud rate of the host computer is 115200, and there is a stop bit, and the baud rate determines the speed of data transmission, when the baud rate is set higher, the data transmission speed is faster, and the stop bit provides the opportunity for the computer to correct the clock synchronization, so that the receiving end can correctly identify the end of the data packet.

[0031] The process of host computer encoding processing: first, read the audio file, then encode the audio file, encode the AAC encoder interface, encapsulate the encoded data according to the data format of MSC, read the fixed length audio data from the encoded data to form the audio frame, then encapsulate the audio frame into audio superframe, generate the data of FAC and SDC in the process of encapsulating the audio frame into audio superframe according to the requirements of DRM manual, and finally send the data of FAC, MSC and SDC to the DRM adaptation board in the FPGA through the serial port according to the fixed length.

[0032] Specifically, the host computer first needs to read the audio file to be processed from a storage medium (such as a hard disk, a U disk, etc.), and after reading the audio file, the host computer needs to call the AAC encoder interface to encode the audio file. AAC (Advanced Audio Coding) is a high-efficiency audio compression format that occupies less storage space. During the encoding process, the host computer will convert the audio file into encoded data in AAC format.

[0033] The encoded data needs to be packaged according to the MSC data format, and the data is organized into a specific data packet or frame structure. During the packaging process, the host computer reads fixed-length audio data from the encoded data to form an audio frame, where the audio frame is the basic unit of subsequent processing.

[0034] The audio frame is further packaged into an audio superframe, which usually contains multiple audio frames and possibly other additional information (such as synchronization information, error detection information, etc.). During the process of packaging the audio frame into the audio superframe, FAC (Frame Alignment Code) and SDC (Service Description Channel) data need to be generated according to the requirements of the DRM (Digital Broadcasting Technology) manual.

[0035] These data are used for synchronization, error detection, and service information description. Finally, the host computer needs to send the FAC, MSC, and SDC data to the DRM adapter board in the FPGA (Field Programmable Gate Array) through the serial port with a fixed length. During the transmission process, the host computer organizes the data into a format that conforms to the serial communication protocol (such as baud rate, data bits, stop bits, etc.), and sends it to the DRM adapter board through the serial port. After receiving the data, the DRM adapter board will perform further processing and decoding to restore the original audio signal or perform other processing and pass it to the DDS.

[0036] The DDS delivers the audio signal amplitude value in the digital audio signal to the pulse width modulation wave generator, which has a total of 1300 gears, generates a pulse wave frequency of 72Khz, and the pulse peak value is 13V. The frequency control word of the DDS is adjustable to be set by the host computer.

[0037] Pulse width modulation (PWM) obtains a smooth changing average voltage by outputting a fixed frequency pulse with different width, which is used to approximate analog output. In PWM, the duty cycle refers to the percentage of time that the pulse is at a higher voltage in the entire pulse period. By changing the duty cycle, the pulse width can be adjusted to simulate different voltage values.

[0038] The pulse width modulation wave generator has 1300 gears, and the pulse wave parameters such as pulse width and frequency can be selected from the 1300 different settings. The generated pulse wave frequency is 72Khz, and the pulse wave frequency is the number of pulse signals in a unit of time, which determines the speed of the pulse wave. There are 72000 pulse signals per second. The pulse peak is 13V, and the pulse peak is the maximum voltage value in the pulse wave, which determines the amplitude of the pulse wave. It is said that the maximum voltage of the pulse wave is 13 volts.

[0039] The digital audio processing circuit inputs the processed audio to the DRM modulation and decoding module, the DRM modulation and decoding module is connected with the DDS, the DDS inputs the audio signal amplitude value to the pulse width modulation wave generator, the power control signal generation circuit inputs the power control signal to the power control signal processing module to convert it into a direct current signal, the pulse width modulation wave generator converts the audio signal amplitude value and the direct current signal into a pulse signal and inputs it to the power amplifier circuit, and the power amplifier circuit amplifies the pulse signal and inputs it to the transmitter.

[0040] In summary, the digital pulse width modulator of the DRM adaptive PDM medium wave transmitter comprises a digital audio processing circuit, a power amplifier circuit, a power control signal generation circuit, an FPGA, and a DRM adaptive board. The FPGA is internally integrated with a power control signal processing module, a DDS, a DRM modulation and decoding module, and a pulse width modulation wave generator. The output end of the digital audio processing circuit is connected with the DRM modulation and decoding module. The digital audio signal is transmitted to the pulse width modulation wave generator through the DDS. The output end of the power control signal generation circuit is connected with one end of the power control signal processing module, and the other end of the power control signal processing module is connected with the pulse width modulation wave generator. The output end of the pulse width modulation wave generator is connected with the power amplifier circuit.

[0041] It should be noted that the output end of the power amplifier circuit is connected with the pulse amplitude detection circuit. The digital audio processing circuit generates a digital audio signal through an industrial computer and an upper computer, and the power control signal generation circuit generates a power control signal. After receiving the digital audio signal from the industrial computer and being encoded, the serial module in the FPGA converts it into a digital audio amplitude signal. The power control signal generation circuit generates a power control signal and sends it to the FPGA to obtain a corresponding digital power control signal after presetting. The two digital signals are processed and combined through the setting algorithm of the pulse width modulation wave generator, the duty cycle value is converted, and the corresponding duty cycle pulse signal is generated. The power amplifier circuit amplifies the signal and outputs it externally.

[0042] A serial module is installed between the digital audio processing circuit and the DRM modulation and decoding module, one end of the serial module is connected with the digital audio processing circuit, and the other end is connected with the DRM modulation and decoding module.

[0043] As shown in Figure 3 The power amplifier circuit includes a power triode amplifier circuit, a pulse signal anomaly detection circuit, a signal amplitude detection circuit and a DC power amplifier circuit, the pulse signal output by the pulse width modulation wave generator is transmitted to the input end of the power triode amplifier circuit and the pulse signal anomaly detection circuit, the output end of the DC power amplifier circuit and the pulse signal anomaly detection circuit is connected with the input end of the power triode amplifier circuit, and the signal amplitude detection circuit performs anomaly detection on the pulse signal output by the power triode amplifier circuit.

[0044] The power triode amplifier circuit amplifies the pulse signal generated by the pulse width modulation wave generator and outputs externally; the pulse signal anomaly detection circuit performs anomaly detection on the input pulse signal, and if there is no pulse signal input, the power triode amplifier circuit is closed, and the signal amplitude detection circuit detects the amplitude of the pulse signal after the power triode amplifier circuit, and reports an error when the amplitude of the pulse signal is less than 13V.

[0045] As shown in Figure 4 The power control signal generation circuit includes a power control hand / auto switching switch, a power control signal manual controller, a power control signal automatic controller and a digital control signal processing circuit, the power control manual switching switch is connected with the power control signal manual controller, the power control automatic switching switch is connected with the power control signal automatic controller, the power control signal manual controller is used for controlling manual control signal generation, the power control signal automatic controller is used for controlling automatic control signal generation, and the power control signal manual controller and the power control signal automatic controller are connected with the digital control signal processing circuit, and the power control hand / auto switching switch is used for changing the algorithm in the FPGA to realize the power control function.

[0046] The utility model converts digital audio signal and power control signal into duty cycle wallpaper in the range of 0 to 1300, and the specific process is as follows:

[0047] According to the power control signal, the duty cycle when there is no audio input is calculated:

[0048]

[0049] wherein, for calculating the DC signal value corresponding to the adapted transmitter audio-free rated power, for the peak value of the triangular wave in the comparator, the value is 5336.

[0050] According to the active power control signal, the duty cycle value when the audio input is calculated: :

[0051]

[0052] wherein, for the digital audio signal amplitude value, for the peak value of the triangular wave in the comparator, the value is 5336.

[0053] The period of the triangular wave and the sine wave is calculated differently, and the output pulse frequency calculation is related to the frequency of the triangular wave, and the output pulse frequency calculation formula is:

[0054]

[0055] wherein, for the system clock frequency, N is the sampling point in a triangular wave.

[0056] Embodiment 2

[0057] The utility model discloses a kind of PDM medium wave transmitter digital pulse width modulation methods suitable for DRM, comprising the following steps: digital audio processing circuit sequentially inputs to DRM modulation and decoding module and DDS by DRM encoding processing to digital audio signal through host computer DRM;DDS inputs the digital audio signal amplitude value into pulse width modulation wave generator;Power control signal generation circuit inputs power control signal into power control signal processing module and outputs direct current signal;Pulse width modulation wave generator converts audio signal amplitude value and direct current signal into pulse signal and inputs to power amplifier circuit;Pulse signal is amplified by power amplifier circuit and is input into transmitter.

[0058] Specifically, the digital audio signal is received and processed by the host computer, and the host computer encodes the digital audio signal by DRM. The encoded digital audio signal is input into a DRM modulation and decoding module, which converts the digital signal into a modulated signal suitable for transmission. At the receiving end, there is a corresponding decoding module to restore the original digital audio signal. The DDS receives the amplitude value of the digital audio signal processed by the DRM modulation and decoding module and inputs it into the pulse width modulation wave generator. The power control signal generation circuit inputs the power control signal into the pulse width modulation wave generator to convert it into a direct current signal. The pulse width modulation wave generator converts the amplitude value of the digital audio signal and the direct current signal into a pulse signal. The pulse signal is input into the power amplification circuit to perform power amplification on the pulse signal. The amplified pulse signal has sufficient power to drive the transmitter.

[0059] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0060] It should be noted that the terms "first", "second" and the like in the description of the present application and the claims and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

Claims

1. A DRM-adapted PDM medium wave transmitter digital pulse width modulator, characterized in that: it comprises a digital audio processing circuit, a power amplification circuit, a power control signal generation circuit, a DRM adaptation board and an FPGA; the output terminals of the digital audio processing circuit and the power control signal generation circuit are connected to the input terminal of the FPGA, the output terminal of the FPGA is connected to the input terminal of the power amplification circuit, the output terminal of the power amplification circuit is connected to the transmitter, and the digital audio processing circuit, the power amplification circuit, the power control signal generation circuit and the FPGA are all mounted on the DRM adaptation board.

2. The DRM-adapted PDM medium wave transmitter digital pulse width modulator according to claim 1, characterized in that: the FPGA is written with a DRM modulation and decoding module, a DDS, a pulse width modulation wave generator, and a power control signal processing module; the input terminal of the DRM modulation and decoding module is connected to the digital audio processing circuit, and the output terminal is connected to the DDS; the input terminal of the power control signal processing module is connected to the output terminal of the power control signal generation circuit; the output terminals of the DDS and the power control signal processing module are both connected to the input terminal of the pulse width modulation wave generator, and the output terminal of the pulse width modulation wave generator is connected to the input terminal of the power amplification circuit.

3. The DRM-adapted PDM medium wave transmitter digital pulse width modulator according to claim 1, characterized in that: the digital audio processing circuit comprises an industrial computer and a serial circuit, an upper computer is mounted on the industrial computer, the digital audio signal of the industrial computer is input to the serial circuit through DRM encoding processing of the upper computer, and the serial circuit is connected to the DRM modulation and decoding through a filter circuit.

4. The DRM-adapted PDM medium wave transmitter digital pulse width modulator according to claim 3, characterized in that: it further comprises a serial module, one end of which is connected to the serial circuit and the other end of which is connected to the DRM modulation and decoding.

5. The DRM-adapted PDM medium wave transmitter digital pulse width modulator according to claim 2, characterized in that: the power amplification circuit comprises a DC power amplification circuit, a power triode amplification circuit, a pulse signal anomaly detection circuit and a signal amplitude detection circuit; the pulse signal output by the pulse width modulation wave generator is transmitted to the input terminals of the power triode amplification circuit and the pulse signal anomaly detection circuit, the output terminals of the DC power amplification circuit and the pulse signal anomaly detection circuit are connected to the input terminal of the power triode amplification circuit, and the signal amplitude detection circuit performs anomaly detection on the pulse signal output by the power triode amplification circuit.

6. The DRM-adapted PDM medium wave transmitter digital pulse width modulator according to claim 2, characterized in that: it further comprises a digital filter, one end of which is connected to the pulse width modulation wave generator and the other end of which is connected to the input terminal of the power amplification circuit.

7. The DRM-adapted PDM medium wave transmitter digital pulse width modulator according to claim 6, characterized in that: ​ ​ ​ ​ ​ ​ ​ ​ ​ The pulse width modulation wave generator has 1300 gears, the frequency of the pulse signal output by the pulse width modulation wave generator is 72Khz, and the pulse peak of the pulse signal output by the pulse width modulation wave generator is 13V.

8. The DRM-adapted PDM medium wave transmitter digital pulse width modulator of claim 3, wherein: The serial port baud rate of the host computer is 115200 Bd, and there is one stop bit.

9. The DRM-adapted PDM medium wave transmitter digital pulse width modulator of claim 1, wherein: The power control signal generation circuit comprises a power control manual / automatic switching switch, a power control signal manual controller, a power control signal automatic controller and a digital control signal processing circuit.

10. The DRM-adapted PDM medium wave transmitter digital pulse width modulator of claim 9, wherein: The power control manual / automatic switching switch is connected with one end of the power control signal manual controller or the power control signal automatic controller, the other end of the power control signal manual controller or the power control signal automatic controller is connected with the digital control signal processing circuit, and the digital control signal processing circuit is connected with the pulse width modulation wave generator.

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