TW201947900A - 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 invention relates to a line driver system, in particular to a line driver system using orthogonal frequency division multiplex (Orthogonal Frequency Division Multiplex, hereinafter referred to as OFDM).

A line driver is a component that converts an analog-to-digital converter (hereinafter referred to as a DAC) from a small signal to a large signal. In power line transmission systems, line drivers are necessary components to achieve long-distance transmission. In the early single-carrier power line transmission systems, the signal peak-to-average power ratio was smaller, so more simple fixed-voltage line drivers were used. With the increase in demand for big data and smart meters, many power line transmission systems switch to multi-carrier OFDM wideband transmission, which is characterized by a large power peak-to-average ratio. In this case, if a fixed-voltage line driver is still used, Will cause high power consumption, system overheating, component aging and other problems.

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 the characteristics of high power peak-to-average ratio, such as OFDM signal, the fixed voltage line driver will cause high power consumption, so it is not suitable for power line transmission systems using OFDM.

The OFDM line driving system proposed by the present invention has real-time adaptive line drivers, combining digital and analog control, real-time monitoring of the size of the predicted signal at the digital end, thereby regulating the voltage of the line driver, and using smaller voltages and smaller signals at small signals. When 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 component life. 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 driving system, including: a modulation circuit that receives an input data for modulation to output an OFDM modulation signal; a voltage controller that generates a voltage control signal according to the OFDM modulation signal; A variable voltage converter receives a voltage and converts the voltage into a control voltage according to a voltage control signal; and a line driving device adjusts a signal according to OFDM to determine when to output a control voltage and the output signal to a power line; wherein, the 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 an OFDM modulation signal and delays the OFDM modulation signal by a preset time; an interpolation circuit that interpolates the OFDM modulation signal to increase the sampling rate and Reduce the error of the OFDM modulation signal; a DAC circuit that converts the OFDM modulation signal into an analog signal; and a line driver that receives and amplifies 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 driving 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 present invention.

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

The modulation circuit 101 receives an input data to perform 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. The voltage Vc is converted into a control voltage VL according to the voltage control signal CS; and the line driving device 104 adjusts the signal MS according to the OFDM to determine when to output the control voltage VL and an output signal S to a power line; wherein the value of the control voltage VL is 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 an embodiment, the line driving device 104 further includes: a delay circuit 104a that receives the OFDM modulation signal MS and delays the OFDM modulation signal MS by a preset time; the interpolation circuit 104b performs internal interpolation on the OFDM modulation signal MS 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. The variable voltage converter 103 provides the control voltage VL to Line driver 104d. The OFDM modulation signal MS is delayed by a preset time, and then the sampling rate is increased by the interpolation circuit 104b to reduce the error. The DAC circuit 104c converts the digital OFDM modulation signal MS into an analog signal AS as an 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 OFDM symbol time is 40 microseconds. In order to avoid distortion of the output signal S of the line driver 104d, the control voltage VL must be 1 volt greater than the peak value of the output signal S. In other words, the control voltage VL is greater than Or equal to (the peak value of the output signal S + 1) volts, as shown in the following formula:

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

In this embodiment, the variable voltage converter 103 can convert the fixed input voltage Vc of 12V into a variable control voltage VL of 4.5 to 8V, 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 needs to increase the voltage from the lowest voltage value of 4.5V to the highest voltage value of 8V, the time required is 35 microseconds. Accordingly, the variable voltage converter 103 needs to change the voltage from the highest value The voltage value of 8V is adjusted to the minimum voltage value of 4.5V, and the time required is also 35 microseconds.

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

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 driving system 100 cuts the OFDM modulation signal MS into B1 ~ B16 intervals, and the time of each interval is 5 microseconds. If the delay time is eight intervals, the delay is 40 microseconds. The initial control voltage VL is At 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 of the line driver 104d, as shown by the solid circle in FIG. 2. The voltage value indicated in the delay signal is the corresponding control voltage VL required for the delayed OFDM modulation signal MS.

Assuming that the control voltage VL in the B1 section of the delayed signal is 5V, the voltage controller 102 can calculate the voltage adjustment model in the B1 section according to the OFDM modulation signal MS. Because the variable voltage converter 103 needs time to adjust the voltage to 5V, Each section (every 5 microseconds) can only be adjusted up to 0.5V. Therefore, the voltage adjustment model of the B1 section knows that the control voltage VL is gradually adjusted from 2V to 5V from the time point of the B2 section 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 of the interval B2 ~ B12 is the same as the previous one. Described.

When at the time point of the B1 interval of the delayed signal, it can be known from the voltage adjustment model of the B1 to B8 interval that the control voltage VL at this time point needs 5, 5, 5.5, 6, 3.5, 4, 2.5, and 2 V, respectively, such as It is shown by the dashed box F1; in order to meet the control voltage VL required by the voltage adjustment model in the B1 ~ B8 interval at this point in time, the minimum output control voltage VL that is currently required is the maximum of the eight voltages 6V, so it is delayed The control voltage VL at the time point of the B1 interval of the signal is 6V.

Please note that the B13 interval of the OFDM modulation signal MS is the corresponding B5 interval of the delayed signal, as shown by the dashed box F2. As mentioned earlier, at this time, the eight intervals of the voltage adjustment model of 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 previous delay signal in the B4 section is 7V, since the maximum voltage can be adjusted to 0.5V in each section of 5 microseconds, the control of the delay signal in the B5 section The voltage VL can only be reduced to 6.5V.

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

By dividing the signal into sections and calculating the required minimum voltage 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 very low, and the delay caused is about One OFDM symbol. According to the results of the analysis, compared to the fixed-voltage line driver, a fixed voltage of 8V must be used. The adaptive line driver used in the present invention can save up to 60% of the power consumption. It has a great effect on saving transmission power consumption and reducing operating temperature. Help.

Although the present invention has been described by way of examples, the scope of the present invention is not limited thereby. As long as it does not deviate from the gist of the present invention, various modifications or changes made by those skilled in the art fall into the scope of the present invention.

Claims (10)

    An OFDM line driving system includes: a modulation circuit that receives an input data for modulation to output an OFDM modulation signal; a voltage controller that 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 driving device determines a time 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 determined by the voltage controller after receiving the OFDM modulation signal in advance, and determining the value of the control voltage according to the OFDM modulation signal.         The system according to claim 1, wherein the line driving device comprises: a delay circuit that receives the OFDM modulation signal and delays the OFDM modulation signal by a preset time; an interpolation circuit for the OFDM modulation The signal is interpolated to increase the sampling rate and reduce the error of the OFDM modulation signal; a DAC circuit converts the OFDM modulation signal into an analog signal; and a line driver receives and amplifies the analog signal to generate the output signal to The power line.         The system according to claim 2, wherein the voltage controller divides the control voltage into N sections, each section of time has a preset time, and each adjacent section has a voltage difference.         The system according to claim 3, wherein the voltage controller determines the minimum required voltage of each interval based on the maximum value of the control voltage required for the OFDM modulation signal in each interval of the N intervals. Control voltage.         The system according to claim 4, wherein the adjustable voltage controller determines that the minimum absolute difference of the control voltage in each adjacent section cannot be greater than the voltage difference.         The system according to claim 5, wherein the preset time is 5 microseconds and the voltage difference is 0.5V.         The system according to claim 5, wherein the control voltage ≧ (the peak value of the output signal +1) volts.         The system according to claim 5, wherein the control voltage is 4.5V to 8V.         The system according to claim 5, wherein the voltage is a certain voltage.         The system according to claim 2, 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 interval of each interval. Minimum of this control voltage