The Hardware Design Of The Dual-channel,40MSPS Arbitrary Waveform Generator Based On PXI Bus

In the modern testing system, the arbitrary waveform generator(AWG) is acommon signal source. It not only can generate functional waveforms and a variety ofmodulation waveforms, but also can generate arbitrary waveform according to user need.With the increasing complexity of aerospace, biomedical and other high-tech products,the AWG with dual or more channels is more widely applied as it can provide morecomplex waveforms, and can be more conveniently and efficiently to meet themulti-test target.According the arbitrary waveform generator’s structure, it is divided into benchinstruments and modular instruments. The dual-channel AWG with PXI bus has thecharacteristics of modular, miniaturization, and more suitable for automatic test system.The thesis is based on the research of the hardware circuit of dual-channel arbitrarywaveform generator module with PXI bus and3U single slot. The thesis mainlyincludes three parts of the PXI interface circuit, the waveform synthesis circuit and theanalog channel circuit. The main contributions are as follows:1. Miniature module design. According to the module’s small volume, high-densitycharacteristics and the requirement of the function integration, the thesis uses FieldProgrammable Gate Array（FPGA) to complete the main functional design and adoptsPCB lamination, chip miniaturization of package options, compact PCB layout andother measures to ensure that the design module volume meets3U single-slot size.2. The degign of the functional circuit. According to the index requirements, thethesis determines the module of general hardware scheme, and chooses the PLX9054todesign the PXI interface circuit, and the thesis realizes the PXI bus to the transformationof the local bus, and completes the instrument control command, the transmission of thedata message. Based on the principle of DDS, the thesis adopts "the FPGA+RAM+DAC" architecture to realize the waveform synthesis circuit, which not only canproduce functional waveforms and arbitrary waveforms, but also can be digitized toachieve AM, FM modulation waveform, the carrier wave or modulation wave can bearbitrary waveform, the carrier wave frequency and the modulation wave frequency can be individually controlled. Based on the analysis of the characteristic of the waveformsynthesizing circuit’s output signal, the thesis designs the signal conditioning circuit toensure the distortion indicators of the module output amplitude, offset, etc. According tothe characteristics of the output signal spectrum, the thesis determines the filter schemeand gives the index analysis and the method of filter design; according to signalamplitude characteristics, the thesis also designs the control scheme of the fineadjustment+coarse adjustment of amplitude and offset, and the high precision dc level,the impedance matching and other problems are analyzed; Based on advantages anddisadvantages of the square wave signal directly produced by the DDS technology, thehysteresis comparator is used to produce square wave signal; Finally, the modulecalibration methods are expounded.3. Testing and verification. the thesis designs appropriate test method based on theindicators of the module, and selects the relevant test equipment to build the testplatform, to verify the functional indicators and performance indicators, and test resultsare analyzed to verify the reasonableness of the design.The test results show that the PXI dual-channel arbitrary waveform generator with40MSa/s sampling rate,16bit vertical resolution and128k storage depth, thesinusoidal maximum output frequency of15MHz, and the maximum output amplitudeof10Vpp (50ohm load), reaches the domestic advanced level.