TWI705672B - Orthogonal frequency division multiplex line driver system - Google Patents

Abstract

The present invention discloses an orthogonal frequency division multiplex (OFDM) line driver system, comprising: a modulation circuit receives an input data for modulation to output an OFDM modulation signal; a voltage controller generates a voltage control signal according to the OFDM modulation signal; The variable voltage converter receives a voltage and converts the voltage to a control voltage according to the voltage control signal; and a line driving device determines when to output the control voltage and the output signal to a power line according to the OFDM modulation signal. Wherein, the value of the control voltage is received by the voltage controller in advance from the OFDM modulation signal, and the control voltage is determined according to the OFDM modulation signal.

Description

OFDM line drive system

The present invention relates to a line driver (Line Driver) system, and particularly relates to a line driver system using Orthogonal Frequency Division Multiplex (OFDM) communication.

A line driver is a component that converts an analog-to-digital converter (hereinafter referred to as DAC) from a small signal to a large signal. In the power line transmission system, the line driver is a necessary component to achieve long-distance transmission. In the early single carrier power line transmission system, the peak to average power ratio of the signal was small, so most of them used simpler fixed voltage line drivers. As the demand for big data and smart meters increases, many power line transmission systems adopt multi-carrier OFDM broadband transmission, which is characterized by a large signal power peak-to-average ratio. In this case, if fixed voltage line drivers are still used, It will cause problems such as high power consumption, system overheating, and component aging.

The fixed voltage line driver is more suitable for the traditional single carrier power line transmission system. Its advantage is low complexity, but if the signal has high power peak-to-average ratio characteristics, such as OFDM signal, the fixed voltage line driver will cause high power consumption, so it is not suitable for power line transmission system using OFDM.

The OFDM line drive system proposed by the present invention has a real-time adaptive line driver, combined with digital and analog control, real-time monitoring of the predicted signal size on the digital side, and adjusts the voltage of the line driver according to the small signal. The signal is converted to a large voltage, that is, the minimum voltage that does not cause signal distortion is provided to the line driver to achieve the purpose of low power consumption, prevent the system from overheating, and extend the life of the component. Compared with the traditional fixed voltage line driver, the present invention can save up to 60% of the power consumption.

The present invention provides an OFDM line drive system, including: a modulation circuit, which receives an input data and modulates to output an OFDM modulation signal; a voltage controller, which generates a voltage control signal according to the OFDM modulation signal; The variable voltage converter receives a voltage and converts the voltage into a control voltage according to the voltage control signal; and a line driving device determines when to output the control voltage and the output signal to a power line according to the OFDM modulation signal; wherein, control After the voltage controller receives the OFDM modulation signal in advance, the voltage controller determines the value of the control voltage according to the OFDM modulation signal.

In one embodiment, the line driving device includes: a delay circuit that receives the OFDM modulation signal and delays the OFDM modulation signal for a predetermined time; an interpolation circuit that performs interpolation on the OFDM modulation signal to increase the sampling rate and Reduce the error of the OFDM modulation signal; a DAC circuit to convert the OFDM modulation signal into an analog signal; and a line driver to receive and amplify the analog signal to generate an output signal to the power line.

100: OFDM line drive system

101: Modulation circuit

102: Voltage Controller

103: Variable voltage converter

104: Line drive device

104a: Delay circuit

104b: Interpolation circuit

104c: DAC circuit

104d: Line driver

MS: OFDM modulation signal

AS: analog signal

F1, F2: dotted frame

Fig. 1 shows a schematic diagram of an embodiment of an OFDM line driving system.

FIG. 2 shows a schematic diagram of an OFDM modulation signal and a control voltage VL according to an embodiment of the invention.

Please refer to FIG. 1, which shows a schematic diagram of an embodiment of an OFDM line driving system. The present invention provides an OFDM line drive system 100, which includes: a modulation circuit 101, a voltage controller 102, a variable voltage converter 103, and a line drive device 104.

The modulation circuit 101 receives an input data for modulation to output an OFDM modulation signal MS; the voltage controller 102 generates a voltage control signal CS according to the OFDM modulation signal MS; the variable voltage converter 103 receives a voltage Vc, According to the voltage control signal CS, the voltage Vc is converted into a control voltage VL; and the line driving device 104 determines when to output the control voltage VL and an output signal S to a power line according to the OFDM modulation signal MS; wherein, the value of the control voltage VL After receiving the OFDM modulation signal MS in advance, the voltage controller 102 determines the control voltage VL according to the value of the OFDM modulation signal MS.

In one embodiment, the line driving device 104 further includes: a delay circuit 104a, which receives the OFDM modulation signal MS and delays the OFDM modulation signal MS for a predetermined time; an interpolation circuit 104b, performs interpolation for the OFDM modulation signal MS Insert to increase the sampling rate and reduce the error of the OFDM modulation signal MS; the DAC circuit 104c converts the OFDM modulation signal MS into an analog signal AS; and a line driver 104d receives and amplifies the analog signal AS to generate an output signal S to the power line .

The following is the operation process of the present invention. First, the modulation circuit 101 performs OFDM modulation on the input data to generate an OFDM modulation signal MS. The voltage controller 102 selects an appropriate control voltage VL according to the magnitude of the OFDM modulation signal MS, the variable voltage converter 103 receives the voltage Vc and outputs the specified control voltage VL, and the variable voltage converter 103 provides the control voltage VL to Line driver 104d. The OFDM modulation signal MS is delayed for a preset time, and then the sampling rate is increased by the interpolation circuit 104b to reduce errors. The DAC circuit 104c converts the digital OFDM modulation signal MS into an analog signal AS, which is used as the input signal of the line driver 104d After being amplified by the line driver 104d, the line driver 104d outputs the output signal S and transmits it to the power line.

In this embodiment, the preset time of one OFDM symbol is 40 microseconds. In order to avoid distortion of the output signal S of the line driver 104d, the control voltage VL must be greater than the peak value of the output signal S by 1 volt, in other words, the control voltage VL is greater than Or equal to (peak value of output signal S+1) volt, as shown in the following formula:

For example, if the maximum value of the output signal S in a certain period of time is 5Volts, the control voltage VL of the line driver 104d during this period of time must be greater than 6Volts; if the maximum value of the output signal S is 3.5Volts, the line driver 104d The control voltage VL must be greater than 4.5Volts, and so on. Therefore, as long as the maximum value of the output signal S in a certain period of time is known, the minimum control voltage VL required for this period can be estimated. In other words, the maximum value of the control voltage VL required by the OFDM modulation signal MS in each interval determines a minimum control voltage required in each interval.

In this embodiment, the variable voltage converter 103 can convert the 12V fixed input voltage Vc into a variable 4.5-8V control voltage VL as the control voltage VL of the line driver 104d. Due to physical limitations, the voltage transition of the variable voltage converter 103 requires a certain time. In this embodiment, the time required for the variable voltage converter 103 to increase or decrease every 0.5V is 5 microseconds. Therefore, if the variable voltage converter 103 wants to increase the voltage from the lowest voltage value of 4.5V to the highest voltage value of 8V, the required time is 35 microseconds. Correspondingly, the variable voltage converter 103 needs to increase the voltage from the highest voltage value to 8V. The voltage value of 8V is reduced to the lowest voltage value of 4.5V, and the time required is also 35 microseconds.

In this embodiment, the OFDM line drive system 100 limits the control voltage VL to eight sections, and the control voltage VL values corresponding to the eight sections are 4.5V, 5V, 5.5V, 6V, 6.5V, 7V, 7.5V, 8V. The absolute difference between adjacent control voltage VL intervals is 0.5V, where the absolute difference is the absolute value after subtracting the voltage values of the adjacent intervals. Then we cut the OFDM modulation signal MS into a plurality of intervals, each interval is 5 microseconds, that is, the time required for the variable voltage converter 103 to adjust the voltage to 0.5V, so one interval can only change 0.5V at most. The maximum value of the OFDM modulation signal MS in each interval determines the minimum control voltage VL required in this interval. Since the variable voltage converter 103 requires up to seven conversions to increase the control voltage VL from 4.5V to 8V, as long as you observe in advance the minimum voltage required for the current and future seven sections (eight sections in total), you can Determine the minimum control voltage VL that should be set in the current interval to ensure that the control voltage VL of the next seven intervals can be satisfied.

As shown in FIG. 2, FIG. 2 shows a schematic diagram of an OFDM modulation signal and a control voltage VL according to an embodiment of the present invention. The OFDM line drive system 100 cuts the OFDM modulation signal MS into intervals B1 to B16, each interval is 5 microseconds, if the delay time is eight intervals, the delay is 40 microseconds, and the initial control voltage VL is 4.5V, when the OFDM modulation signal MS is in the B9 interval, the B1 interval of the delay signal of the OFDM modulation signal MS will appear at the output end of the line driver 104d, as shown by the circular solid box in FIG. Among them, the voltage value marked in the delayed signal is the corresponding control voltage VL required by the delayed OFDM modulation signal MS.

Assuming that the control voltage VL in the B1 interval of the delay signal is required to be 5V, the voltage controller 102 can calculate the B1 interval voltage adjustment model according to the OFDM modulation signal MS. Because the variable voltage converter 103 needs time to adjust the voltage to 5V, Each interval (every 5 microseconds) can only adjust 0.5V at most, so the B1 interval voltage adjustment model knows that the control voltage VL is gradually adjusted from 2V to 5V at the time point in the B2 interval of the OFDM modulation signal; in other words , The voltage controller calculates the control voltage VL corresponding to any interval before each interval according to the time point of each interval of the OFDM modulation signal; similarly, the voltage adjustment model for the interval B2~B12 is the same as the previous one. Narrated.

At the time point in the B1 interval of the delay signal, it can be known from the voltage adjustment model between B1 and B8 that the control voltage VL at this time point requires 5, 5, 5.5, 6, 3.5, 4, 2.5, 2V, respectively, such as The dashed box F1 is shown; in order to meet the control voltage VL required by the voltage adjustment model between B1 and B8 at this point in time, it is obtained that the minimum output control voltage VL necessary at present is the maximum value of the eight voltages, 6V, so the delay The control voltage VL at the time point in the B1 interval of the signal is 6V.

Please pay special attention that the B13 interval of the OFDM modulation signal MS corresponds to the B5 interval of the delay signal, as shown in the dashed box F2. As mentioned above, the eight intervals of the voltage adjustment model in the B5~B12 interval are satisfied. Although the minimum control voltage VL is 6V, because the control voltage VL at the time point of the B4 interval of the previous delay signal is 7V, since each interval 5 microseconds can only adjust the voltage of 0.5V at most, the control of the B5 interval of the delay signal The voltage VL can only drop to 6.5V.

Finally, the voltage controller determines the control voltage VL of each interval, and the control voltage VL of each interval cannot be less than 4.5V and not greater than 8V.

By dividing the signal into sections and calculating the minimum voltage required for each section in advance, the required control voltage VL of the final line driver can be simply determined. The required digital signal control cost is extremely low, and the resulting delay is about One OFDM symbol. According to the results of the analysis, compared to the fixed voltage line driver that must use a fixed voltage of 8V, the adaptive line driver used in the present invention can save up to 60% of the power consumption, which is very important for saving transmission power consumption and reducing operating temperature. Help.

Although the above embodiments illustrate the present invention, it does not limit the scope of the present invention. As long as it does not deviate from the gist of the present invention, various modifications or changes made by the industry will fall into the scope of the present invention.

100‧‧‧OFDM line drive system

101‧‧‧Modulation circuit

102‧‧‧Voltage Controller

103‧‧‧Variable voltage converter

104‧‧‧Line drive device

104a‧‧‧Delay circuit

104b‧‧‧Interpolation circuit

104c‧‧‧DAC circuit

104d‧‧‧Line Driver

MS‧‧‧OFDM modulation signal

AS‧‧‧Analog signal

Claims (8)

An OFDM line drive system includes: a modulation circuit that receives an input data and modulates it to output an OFDM modulation signal; a voltage controller generates a voltage control signal according to the OFDM modulation signal; a variable voltage The converter receives a voltage and converts the voltage into a control voltage according to the voltage control signal; and a line drive device determines when to output the control voltage and an output signal to a power line according to the OFDM modulation signal; wherein, After the voltage controller receives the OFDM modulation signal in advance, the value of the control voltage determines the value of the control voltage according to the OFDM modulation signal; the line driving device includes: a delay circuit that receives the OFDM modulation signal And delay the OFDM modulation signal for a preset time; an interpolation circuit to interpolate the OFDM modulation signal to increase the sampling rate and reduce the error of the OFDM modulation signal; a DAC circuit to modulate the OFDM The signal is converted into an analog signal; and a line driver receives and amplifies the analog signal to generate the output signal to the power line; wherein, the voltage controller divides the control voltage into N intervals, and the time of each interval has a preset Set time, each adjacent area There is a voltage difference between. The system according to claim 1, wherein the voltage controller determines the minimum required voltage for each interval according to the maximum value of the control voltage required by the OFDM modulation signal in each interval among the N intervals Control voltage. The system according to claim 2, wherein the voltage controller determines that the minimum absolute difference of the control voltage in each adjacent interval cannot be greater than the voltage difference. The system according to claim 3, wherein the preset time is 5 microseconds, and the voltage difference is 0.5V. The system according to claim 3, wherein the control voltage is ≥ (peak value of the output signal+1) volt. The system according to claim 3, wherein the control voltage is 4.5V-8V. The system according to claim 3, wherein the voltage is a certain voltage. The system according to claim 1, wherein the voltage controller calculates the control voltage corresponding to each interval according to the time point of each interval of the OFDM modulation signal to determine the required control voltage for each interval The minimum control voltage.

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