Debugging method of evm based on fpga quadrature modulation circuit

Abstract

The invention discloses a quadrature modulation circuit based on FPGA and a method for debugging EVM thereof. The quadrature modulation circuit based on FPGA comprises an FPGA, a DA connected with the FPGA, a capacitance resistor network connected with the DA, and a quadrature modulator connected with the capacitance resistor network. The FPGA sends I-phase data and Q-phase data to DA through a time-sharing multiplexing means, the DA converts the I-phase data and Q-phase data into simulated I baseband signals and simulated Q baseband signals, and the I baseband signals are sent to the capacitance resistor network through an I channel. The Q baseband signals are sent to the capacitance resistor network through a Q channel. The capacitance resistor network conducts DC bias and filter processing on the I baseband signals and Q baseband signals. The quadrature modulator carries out quadrature modulation on the I baseband signals and Q baseband signals output by the capacitance resistor network to finally form RF signal output.

Description

technical field [0001] The invention relates to a quadrature modulation technology, in particular to an FPGA-based quadrature modulation circuit and a method for debugging its EVM. Background technique [0002] For some modulation schemes with constant envelope, such as GMSK (Gauss Minimum Shift Keying: Gauss Minimum Shift Keying) in the GSM mobile communication system, the phase error and frequency difference are used as indicators to measure the modulation accuracy. For QPSK, it is a non-constant envelope modulation. The above two indicators are not enough to reflect the modulation accuracy, because this modulation method makes the signal not only have errors in phase, but also in amplitude. Therefore, for the non-constant envelope modulation accuracy, an indicator Error Vector Magnitude (EVM: Error Vector Magnitude) that can comprehensively measure the signal amplitude error and phase error is proposed. [0003] EVM characterizes the modulation accuracy, which is a key i...

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Problems solved by technology

[0005] In the existing design process, the bias voltage and filter parameters of the coupling circuit are mainly determined according to the bias voltage requirements of the digital-to-analog conversion chip and the quadrature modulation chip and the signal frequency and bandwidth of the application. The coupling circuit is generally composed of resistors And capacitor network, which requires very accurate calculation of the values ​​of each resistor and capacitor, these values ​​may be non-standard, and non-standard resistors and capacitors are generally not available in the market, and only similar ones can be used in the final production circuit In addition, the difference in PCB routing and material and the individual differences of chips used in production will affect the EVM value of the modulated signal, making the signal quality worse

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