Digital display scope (DDS) signal generator and amplitude control method thereof

Abstract

The invention discloses a digital display scope (DDS) signal generator and an amplitude control method of the digital display scope (DDS) signal generator. The DDS signal generator comprises a main control unit, a field programmable gata array (FPGA) module connected with the main control unit and a composite DAC connected with the FPGA module, wherein the main control unit is used for allocating amplitude compensation coefficients and reference voltage values so as to enable a sum of a bit wide of the amplitude compensation coefficients and the bit wide of the reference voltage values to be bigger than or equal to the bit wide of wave form sampling points. The FPGA module comprises a wave form storage used for storing wave form sampling points, a digital multiplier used for multiplying the wave form sampling points by the amplitude compensation coefficients to obtain a wave form digital quantity and sending the wave form digital quantity to a data DAC installed inside the composite DAC and a signal program initiation (SPI) control module is used for converting the reference voltage values into an SPI form and sending to a gain DAC installed inside the composite DAC, and the composite DAC converts wave form figures in the data DAC into an analogy quantity according to the reference voltage values in the gain DAC.

Description

technical field [0001] The present invention relates to the technical field of signal generators, in particular to the amplitude control technology of a Direct Digital Frequency Synthesis (DDS, Direct Digital Frequency Synthesis) signal generator, specifically a DDS signal generator and an amplitude control method thereof. Background technique [0002] In the actual communication process, the system has high requirements on frequency accuracy and stability, and often needs to use a variety of signals with different frequencies and phases. Traditional waveform generators are implemented by analog circuits, limited by hardware circuits, not only generate fewer waveforms, but also have low precision, but also have large volume and poor flexibility. DDS technology is a new frequency synthesis technology that directly synthesizes the required waveform from the concept of phase; DDS signal generator has the advantages of fast frequency conversion, high resolution, wide frequency s...

AI Technical Summary

Problems solved by technology

[0005] (1) Its output waveform can only be a sine wave and cannot be used as a function / arbitrary waveform generator;

[0006] (2) The phase accumulator is 32 bits, and the frequency resolution can only be 29mHz, which is far from the 1uHz of the mainstream signal generator;

[0007] (3) The phase control word is 8 bits, and the phase resolution is only 1.4o, while many signal generators have a phase accuracy of 0.01o or even 0.001o;

[0008] (4) The sampling rate is only 125MHz, which cannot meet the current market demand for signal generators with high sampling rate and high bandwidth

[0010] (1) The multiplier and amplitude DAC will increase the area of ​​the printed circuit board, correspondingly increasing the cost and design complexity;

[0011] (2) The precision of amplitude control is limited, figure 1 The amplitude DAC in the medium controls the amplitude with 10-bit precision. Taking the reference voltage 2.5V as an example, the accuracy can only reach 0.005V;

[0012] (3) Due to the nonlinearity of analog devices, the analog multiplier will bring harmonic distortion to the output signal, and for high-speed signals, the distortion will be greater

[0015] but, figure 2 The scheme still has the following defects: the vertical resolution of the data DAC will be reduced due to the data bit width of the gain DAC

Final vertical resolution loses 6 bits of precision

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