选择最佳测试音和测试设备的成功高速ADC正弦波

Unfortunately, this very method will require a high-resolution signal synthesizer capable of supporting all the digits necessary to get an accurate reading on the input frequency. A different approach, which offsets the clock frequency from its exact value of 120MHz, yet still, obeying the rules for coherent sampling, can overcome such stringent demand. The next five steps show that the need for a high-resolution instrument is relaxed by 'distributing' the number of required digits between input and sampling frequency.

1. Determine the resolution of the sampling frequency that fits into an 8192-point record by
   
   Δf = fSAMPLE / NRECORD
   Δf = 120MHz / 8192 = 14.6484375kHz
   
   
2. Some of commonly available signal generators in the market may not offer enough resolution to offer this many digits to accurately capture both input and sampling frequency. To bypass this requirement and still meet the coherent sampling condition, it is recommended to select Δf based on the next highest integer number.
   
   Δf = int (fSAMPLE / NRECORD) = 15kHz
   
   
3. Based on the new Δf, the exact sampling frequency computes to
   
   fSAMPLE = Δf × NRECORD
   fSAMPLE = 15kHz × 8192 = 122.880MHz
   
   
4. Δf also helps to determine the size of NWINDOW. Again, use the next highest integer odd (or mutually prime) number, determined by the desired input test tone and Δf.
   
   NWINDOW = int (fIN / Δf)
   NWINDOW = 17MHz / 15kHz = 1133
   
   
5. Based on these findings, the near optimum input test tone fIN calculates as follows
   
   fIN = fSAMPLE × (NWINDOW / NRECORD)
   fIN = 122.88MHz (1133 / 8192) = 16.995MHz

Equipment and Set-Up Recommendations for a Successful High-Speed ADC Test

Table 1 lists some recommended hardware instruments and software products, which have proven to be quite valuable for data capture and analysis of high-speed ADC dynamic performance parameters.

Table 1. Equipment and software tool recommendations for high-speed ADC testing

Type Of Equipment	Equipment Count and Notes
Synthesized Signal Generator: HP/Agilent 8662/3A (10kHz to 1.28/2.56GHz, -139dBm to +13dBm) or HP/Agilent 8644A (252kHz to 1.030GHz, -140dBm to +20dBm)	2 generators for single-channel ADC input and clock 3 generators for IMD test (single-channel ADC) or 3 generators for dual-channel ADC inputs and clock 4 generators for IMD test (dual-channel ADC)
Logic Analyzer System: HP/Agilent 16500C mainframe (or similar) (1Gsps State Analyzer Card HP16517A optional and for ADCs with sampling speeds >100MHz only)	1 Logic analyzer (in default configuration, allows to evaluate up to 4 channels for ADCs with up to 16-bit resolution)
Band-Pass Filters: TTE's Q56/KC7 series for frequencies 100MHz/>100MHz (Other suitable filter suppliers are Allen Avionics or KL Microwave)	1 Filter for single-channel ADC 2 Filters for simultaneous evaluation of a dual-channel ADC
Power Combiner: Mini-Circuits 15542 ZSC-2-1W (or similar)	1 Combiner (used for two-tone IMD evaluation only)
RF FrequencyBalun/Transformer: MA/COM H-9-SMA (or similar)	2 Baluns for single-channel ADC and clock 3 Baluns for dual-channel ADC and clock
GPIB-Compatible Interface Card: National Instruments GPIB/IEEE?-488 Interface Card + driver and installation software (PC-/PCMCIA-card or GPIB-to-USB port adapter)	1 Interface card Note: This card is recommended for fast data transfer between logic analyzer and computer; requires C-based software platform (e.g. LabWindows/CVI) to control the interface. Data can also be extracted from the logic analyzer with a floppy disk.
Data Analysis Software: MATLAB from The Math Works Inc. or Measurement Studio with LabWindows/CVI from National Instruments	1 License for each software package Note: LabWindows/CVI provides a C-based platform to control the interface between logic analyzer and PC