DS335 Synthesized Function Generator

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2-2 Introduction DDS gives the DS335 greater flexibility and power than conventional synthesizers without the drawbacks inherent in PLL designs. DS335 Description Figure 2: DS335 Block Diagram A block diagram of the DS335 is shown in Figure 2. The heart of the DS335 is a 10 MHz crystal clock. The 10 MHz clock controls the DDS ASIC, waveform ROM, and high-speed 12bit DAC. Sampling theory limits the frequency of the waveform output from the DAC to about 40% of 10 MHz, or 3 MHz. The 48 bit length of the ASIC's PIR's sets the frequency resolution to about 36 nHz. These parameters and the DAC's 12 bit resolution define the performance limits of the DS335. The reconstruction filter is key to accurately reproducing a waveform in a sampled data system. The DS335 contains two separate filters. For sine wave generation the output of the DAC goes through a 7 th order Cauer filter, while ramps, and triangles pass instead through a 3.5 MHz 5 th order Bessel filter. The Cauer filter has a cutoff frequency of 3.4 MHz and a stopband attenuation of 86 dB, and includes a peaking circuit to correct for the sin(x)/x amplitude response characteristic of a sampled system. This filter eliminates any alias frequencies from the waveform output and allows generation of extremely pure sine waves. However, the Cauer filter has very poor time response and is only useful for CW waveforms. Therefore, the Bessel filter was chosen for its ideal time response, eliminating rings and overshoots from stepped waveform outputs. The output from the filter passes through pre-amplifier attenuators with a 0 to 14 dB range. The attenuators are followed with a wide bandwidth power amplifier that outputs a 10 V peak-to-peak into a 50 ohm load with a rise time of less than 15 ns. The output of the power amplifier passes through a series of four step attenuators (2, 4, 8, and 16 dB) that set the DS335's final output DS335 Synthesized Function Generator
Introduction 2-3 amplitude. The post amplifier attenuators allow internal signal levels to remain as large as possible, minimizing output noise and signal degradation. Square waves and waveform sync signals are generated by discriminating the function waveform with a high-speed comparator. The output of the comparator passes to the SYNC OUTPUT and, in the case of square waves, to the amplifier input. Generating square waves by discriminating the sine wave signal produces a square wave output with rise and fall times much faster than allowed by either of the signal filters. DS335 Synthesized Function Generator
Page 1 and 2: MODEL DS335 Synthesized Function Ge
Page 3 and 4: Table of Contents i Table of Conten
Page 5 and 6: Safety and Preparation for Use iii
Page 7 and 8: Specifications v SPECIFICATIONS FRE
Page 9 and 10: Specifications vii SYNC & SWP/FSK O
Page 11 and 12: Abridged Command List ix Abridged C
Page 13 and 14: Getting Started 1-1 Getting Started
Page 15: Introduction 2-1 Introduction to Di
Page 19 and 20: Features 2-5 Front Panel Features 1
Page 21 and 22: Features 2-7 Rear Panel Features 1)
Page 23 and 24: Function Setting 2-9 DS335 OPERATIO
Page 25 and 26: Function Setting 2-11 Vpp Vrms Func
Page 27 and 28: Sweeps & FSK 2-13 FREQUENCY SWEEPS
Page 29 and 30: Sweeps & FSK 2-15 External Frequenc
Page 31 and 32: DS335 Setup 2-17 INSTRUMENT SETUP I
Page 33 and 34: Programming Commands 3-1 PROGRAMMIN
Page 35 and 36: Programming Commands 3-3 parameters
Page 37 and 38: Programming Commands 3-5 *TRG The *
Page 39 and 40: Programming Commands 3-7 Hardware T
Page 41 and 42: Programming Commands 3-9 6 URQ Set
Page 43 and 44: Programming Examples 3-11 Program E
Page 45 and 46: Programming Examples 3-13 EXAMPLE 2
Page 47 and 48: Troubleshooting 4-1 TROUBLESHOOTING
Page 49 and 50: Troubleshooting 4-3 rate is 9600 ba
Page 51 and 52: Performance Tests 4-5 PERFORMANCE T
Page 53 and 54: Performance Tests 4-7 4) Increase t
Page 55 and 56: Performance Tests 4-9 2) Read the A
Page 57 and 58: Performance Tests 4-11 HARMONIC DIS
Page 59 and 60: Performance Tests 4-13 DS335 PERFOR
Page 61 and 62: Calibration 4-15 CALIBRATION Introd
Page 63 and 64: Calibration 4-17 Now the post ampli
Page 65 and 66: Calibration 4-19 NECESSARY EQUIPMEN
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Circuitry 5-1 DS335 Circuit Descrip
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Circuitry 5-3 System DAC and S/H's
Page 71 and 72:
Circuitry 5-5 Output Filters (DS335
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Circuitry 5-7 Power Supplies (DS335
Page 75 and 76:
DS335 Component Parts List 5-9 Powe
Page 77 and 78:
DS335 Component Parts List 5-11 REF
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DS335 Synthesized Function Generator

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