A method for measuring signal modulation

Abstract

This invention discloses a method for measuring signal modulation depth. The method amplifies the received modulated signal using an amplifier module, then isolates it using an isolation module to cut off the interference of the back electromotive force of the power amplifier on the preceding stage, reducing distortion. The modulated signal is then demodulated using a demodulation module, and the effective value of the demodulated signal is measured using an RMS detection module. A signal conditioning module converts the analog signal into a digital signal within the voltage range that the microcontroller can receive. An FPGA frequency measurement module measures the modulation index and maximum frequency deviation. The microcontroller then determines the modulation scheme and obtains the modulation depth of the modulated signal by reading the amplitude modulation coefficient, frequency modulation index, and maximum frequency deviation. This effectively solves the problem of measuring parameters such as signal modulation depth. This invention can automatically determine the modulation scheme and effectively solve the problem of measuring signal modulation depth (i.e., amplitude modulation coefficient and frequency modulation index) and maximum frequency deviation.

Description

Technical Field

[0001] This invention relates to a method for measuring signal modulation. Background Technology

[0002] With the rapid development of wireless data transmission technology, in data transmission network systems, due to the limitation of transmission speed, it is often impossible to use a single baseband transmission. Modulation methods are employed, which not only allow for frequency shifting, moving the spectrum of the modulated signal to its desired propagation position and converting the modulated signal into a more suitable signal for propagation, but also significantly impact the transmission effectiveness and reliability of the system. The modulation method often determines the transmission characteristics of the entire communication system; therefore, quickly determining the signal modulation method in a communication system is crucial. Furthermore, in practical applications, due to noise and attenuation during transmission, timely detection of parameters such as modulation depth, frequency offset, and frequency is essential. Therefore, how to measure signal modulation depth has become an indispensable problem in the field of signal modulation. Summary of the Invention

[0003] The present invention provides a signal modulation measurement method to solve the problems existing in the prior art.

[0004] The technical solutions adopted in this invention are as follows:

[0005] A method for measuring signal modulation, including

[0006] 1) The modulated signal, which is generated by the signal generator as an AM or FM signal, is amplified and then input to the isolation module, which reduces the distortion of the modulated signal.

[0007] 2) If the modulated signal input to the isolation module is an AM signal, the AM signal is split into two paths after being output from the isolation module. One path enters the FPGA frequency measurement module and outputs a zero voltage signal, while the other path enters the demodulation module with AM demodulation unit and FM demodulation unit.

[0008] After the AM signal enters the demodulation module and is received by both the AM demodulation unit and the FM demodulation unit, the FM demodulation unit outputs a zero-voltage signal to the third effective value detection module connected to the FM demodulation unit, and the third effective value detection module outputs a zero-voltage signal.

[0009] The AM demodulation unit demodulates the AM signal to obtain a sine wave signal. The sine wave signal is input to the first RMS detection module and the second RMS detection module connected to the AM demodulation unit, and two DC voltage signals are obtained.

[0010] The DC voltage signal output from the second effective value detector module is input to the signal conditioning module, and then the signal conditioning module outputs the second judgment voltage.

[0011] The zero-voltage signal output by the third effective value detector module is input to the signal conditioning module, and the signal conditioning module outputs the third judgment voltage.

[0012] 3) If the modulated signal input to the isolation module is an FM signal, the FM signal is split into two paths after being output from the isolation module. One path enters the FPGA frequency measurement module to calculate the modulation degree and maximum frequency deviation of the FM signal.

[0013] Another signal enters the demodulation module and is simultaneously received by the AM demodulation unit and the FM demodulation unit. After receiving the FM signal, the AM demodulation unit outputs a zero-voltage signal, which is then input to the first RMS detector module and the second RMS detector module, respectively.

[0014] The second effective value detection module outputs a zero voltage signal to the signal conditioning module, and then the signal conditioning module outputs a second judgment voltage.

[0015] The FM demodulation unit demodulates the FM signal to obtain a sine wave signal. The sine wave signal is input to the third RMS detection module, and the third RMS detection module outputs a DC voltage signal.

[0016] The DC voltage signal output by the third effective value detector module is input to the signal conditioning module, and the signal conditioning module outputs the third judgment voltage.

[0017] 4) The microcontroller compares the magnitudes of the second and third judgment voltages and determines the type of the input modulated signal.

[0018] If the input is an AM signal, the microcontroller acquires the DC voltage signal output by the first effective value detector module, calculates the amplitude modulation coefficient, and displays the signal type and calculation result on the display module connected to the microcontroller.

[0019] If the input is an FM signal, the microcontroller acquires the signal output from the FPGA frequency measurement module and displays the signal type and the calculation result of the FPGA frequency measurement module on the display module.

[0020] Furthermore, the signal conditioning module includes an LM339 chip and a CD4011 chip.

[0021] If the output of the second or third RMS detector module is a zero voltage signal, the zero voltage signal will output 0V after passing through the LM339 chip, and then the 0V voltage will output 0-3.3V after passing through the CD4011 chip.

[0022] If the voltage signal output by the second or third effective value detector module is a DC voltage signal obtained by inputting a sine wave signal, the DC voltage signal is output as 5V after passing through the LM339 chip, and then the 5V voltage is output as 0V after passing through the CD4011 chip.

[0023] When the second judgment voltage is 0-3.3V and the third judgment voltage is 0V, the microcontroller determines that the input signal is an FM signal;

[0024] When the second judgment voltage is 0V and the third judgment voltage is 0-3.3V, the microcontroller determines that the input signal is an AM signal.

[0025] The formula for calculating the amplitude modulation coefficient ma of the AM signal is:

[0026] ma = UΩ / Uw;

[0027] In the formula: UΩ is the amplitude of the modulating signal in the AM signal, and Uw is the amplitude of the carrier signal in the AM signal;

[0028] The modulation frequency and maximum frequency deviation of the FM signal are calculated using a fast algorithm based on discrete Fourier transform.

[0029] The present invention has the following beneficial effects:

[0030] This invention can automatically identify the modulation mode and effectively solve the problem of measuring signal modulation degree (i.e., amplitude modulation coefficient and frequency modulation degree) and maximum frequency deviation. Attached Figure Description

[0031] Figure 1 This is a block diagram illustrating the principle of the present invention.

[0032] Figure 2 This is a block diagram illustrating the principle of the signal conditioning module of the present invention. Implementation

[0033] The invention will now be further described with reference to the accompanying drawings.

[0034] like Figure 1 The present invention provides a signal modulation measurement method, comprising:

[0035] 1) The modulated signal, either AM or FM, emitted by the signal generator is amplified by the VCA810 chip and then input to the isolation module, which reduces the distortion of the modulated signal.

[0036] 2) If the modulated signal input to the isolation module is an AM signal, the AM signal is split into two paths after being output from the isolation module. One path enters the FPGA frequency measurement module and outputs a zero voltage signal, while the other path enters the demodulation module.

[0037] The demodulation module includes an AM demodulation unit and an FM demodulation unit. AM signals are received by both the AM and FM demodulation units simultaneously upon entering the demodulation module.

[0038] After receiving the AM signal, the FM demodulation unit outputs a zero-voltage signal to the third RMS detector module, which then outputs a zero-voltage signal.

[0039] After receiving the AM signal, the AM demodulation unit demodulates the AM signal to obtain a sine wave signal. The sine wave signal is input to the first effective value detection module and the second effective value detection module, and the first effective value detection module and the second effective value detection module output two DC voltage signals.

[0040] The DC voltage signal output by the second effective value detector module is input to the signal conditioning module, and then the signal conditioning module outputs the second judgment voltage.

[0041] The zero-voltage signal output by the third effective value detector module is input to the signal conditioning module, and then the signal conditioning module outputs the third judgment voltage.

[0042] 3) If the modulated signal input to the isolation module is an FM signal, the FM signal is split into two paths after being output from the isolation module. One path enters the FPGA frequency measurement module to calculate the modulation degree and maximum frequency deviation of the FM signal. The other path enters the demodulation module and is simultaneously received by the AM demodulation unit and the FM demodulation unit.

[0043] After receiving the FM signal, the AM demodulation unit outputs a zero-voltage signal and inputs the zero-voltage signal to the first effective value detection module and the second effective value detection module respectively. Both the first effective value detection module and the second effective value detection module output zero-voltage signals, and the second effective value detection module outputs the zero-voltage signal to the signal conditioning module, which then outputs the second judgment voltage.

[0044] The FM demodulation unit demodulates the FM signal and obtains a sine wave signal. The sine wave signal is input to the third effective value detection module, and the third effective value detection module outputs a voltage DC signal. The voltage DC signal output by the third effective value detection module is input to the signal conditioning module, and the signal conditioning module outputs the third judgment voltage.

[0045] 4) The microcontroller compares the magnitudes of the second and third judgment voltages and determines the type of the input modulated signal. If the input is an AM signal, the microcontroller acquires the DC voltage signal output by the first effective value detector module, calculates the amplitude modulation coefficient, and displays the signal type and calculation result on the display module connected to the microcontroller.

[0046] If the input is an FM signal, the microcontroller acquires the signal output from the FPGA frequency measurement module and displays the signal type and the calculation result of the FPGA frequency measurement module on the display module.

[0047] like Figure 2 The signal conditioning module in this invention includes an LM339 chip and a CD4011 chip. The main function of the LM339 chip is to shape the AC signal from the preceding stage, while the main function of the CD4011 chip is to reduce the voltage level to a range acceptable to the microcontroller.

[0048] Specifically, if the output of the second effective value detector module or the third effective value detector module is a zero voltage signal, the zero voltage signal will output 0V voltage after passing through the LM339 chip, and then the 0V voltage will output a voltage of 0-3.3V after passing through the CD4011 chip.

[0049] If the voltage signal output by the second or third effective value detector module is a DC voltage signal obtained by inputting a sine wave signal, the DC voltage signal is output as 5V after passing through the LM339 chip, and then the 5V voltage is output as 0V after passing through the CD4011 chip.

[0050] When the microcontroller determines whether the signal is AM or FM, if the second judgment voltage is 0-3.3V and the third judgment voltage is 0V, the microcontroller determines the input signal to be an FM signal. If the second judgment voltage is 0V and the third judgment voltage is 0-3.3V, the microcontroller determines the input signal to be an AM signal.

[0051] The AM demodulation unit includes an NE564 chip and a 2AP9 diode. The envelope detection circuit composed of the 2AP9 diode demodulates the AM modulated signal (the NE564 chip and the envelope detection circuit are both existing conventional circuits, so this invention will not elaborate on them).

[0052] The FM demodulation unit uses the NE564 chip, which is an ultra-high frequency general-purpose microcontroller with integrated phase-locked loop circuit, and can be used as a high-speed demodulator.

[0053] The FPGA frequency measurement module includes an EP3C5 chip, which can measure the maximum frequency deviation and frequency modulation of a signal through a fast algorithm of discrete Fourier transform.

[0054] This invention amplifies the received modulated signal using an amplifier module (VCA810 chip), then uses an isolation module to cut off the interference of the back electromotive force of the power amplifier on the preceding stage, reducing distortion. A demodulation module then demodulates the modulated signal, and an RMS detection module measures the RMS value of the demodulated signal. A signal conditioning module converts the analog signal into a digital signal within the voltage range that the microcontroller can receive. An FPGA frequency measurement module measures the modulation index and maximum frequency deviation. Finally, the microcontroller determines the modulation method of the signal and obtains the modulation depth of the modulated signal by reading the amplitude modulation coefficient, modulation index, and maximum frequency deviation. This effectively solves the problem of measuring parameters such as signal modulation depth.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for measuring signal modulation, characterized in that: include 1) The modulated signal, which is generated by the signal generator as an AM or FM signal, is amplified and then input to the isolation module, which reduces the distortion of the modulated signal. 2) If the modulated signal input to the isolation module is an AM signal, the AM signal is split into two paths after being output from the isolation module. One path enters the FPGA frequency measurement module and outputs a zero voltage signal, while the other path enters the demodulation module with AM demodulation unit and FM demodulation unit. After the AM signal enters the demodulation module and is received by both the AM demodulation unit and the FM demodulation unit, the FM demodulation unit outputs a zero-voltage signal to the third effective value detection module connected to the FM demodulation unit, and the third effective value detection module outputs a zero-voltage signal. The AM demodulation unit demodulates the AM signal to obtain a sine wave signal. The sine wave signal is input to the first RMS detection module and the second RMS detection module connected to the AM demodulation unit, and two DC voltage signals are obtained. The DC voltage signal output from the second effective value detector module is input to the signal conditioning module, and then the signal conditioning module outputs the second judgment voltage. The zero-voltage signal output by the third effective value detector module is input to the signal conditioning module, and the signal conditioning module outputs the third judgment voltage. 3) If the modulated signal input to the isolation module is an FM signal, the FM signal is split into two paths after being output from the isolation module. One path enters the FPGA frequency measurement module to calculate the modulation degree and maximum frequency deviation of the FM signal. Another signal enters the demodulation module and is simultaneously received by the AM demodulation unit and the FM demodulation unit. After receiving the FM signal, the AM demodulation unit outputs a zero-voltage signal, which is then input to the first RMS detector module and the second RMS detector module, respectively. The second effective value detection module outputs a zero voltage signal to the signal conditioning module, and then the signal conditioning module outputs a second judgment voltage. The FM demodulation unit demodulates the FM signal to obtain a sine wave signal. The sine wave signal is input to the third RMS detection module, and the third RMS detection module outputs a DC voltage signal. The DC voltage signal output by the third effective value detector module is input to the signal conditioning module, and the signal conditioning module outputs the third judgment voltage. 4) The microcontroller compares the magnitudes of the second and third judgment voltages and determines the type of the input modulated signal. If the input is an AM signal, the microcontroller acquires the DC voltage signal output by the first effective value detector module, calculates the amplitude modulation coefficient, and displays the signal type and calculation result on the display module connected to the microcontroller. If the input is an FM signal, the microcontroller acquires the signal output from the FPGA frequency measurement module and displays the signal type and the calculation result of the FPGA frequency measurement module on the display module. The signal conditioning module includes an LM339 chip and a CD4011 chip. If the output of the second or third RMS detector module is a zero voltage signal, the zero voltage signal will output 0V after passing through the LM339 chip, and then the 0V voltage will output 0-3.3V after passing through the CD4011 chip. If the voltage signal output by the second or third effective value detector module is a DC voltage signal obtained by inputting a sine wave signal, the DC voltage signal is output as 5V after passing through the LM339 chip, and then the 5V voltage is output as 0V after passing through the CD4011 chip. When the second judgment voltage is 0-3.3V and the third judgment voltage is 0V, the microcontroller determines that the input signal is an FM signal; When the second judgment voltage is 0V and the third judgment voltage is 0-3.3V, the microcontroller determines that the input signal is an AM signal.

2. The signal modulation measurement method as described in claim 1, characterized in that: The formula for calculating the amplitude modulation coefficient ma of the AM signal is: ma = UΩ / Uw; In the formula: UΩ is the amplitude of the modulating signal in the AM signal, and Uw is the amplitude of the carrier signal in the AM signal; The modulation frequency and maximum frequency deviation of the FM signal are calculated using a fast algorithm based on discrete Fourier transform.

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