Xilinx Frequency Generator manual Final Output Spectrum

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Final Output Spectrum

Observing the frequency spectrum of the final output reveals that you can not get something for nothing and helps us to understand when the frequency aligned mode should and should not be used. I have used the infinite persistence display again and this time it was even more useful to do so. As before, plots on the left cover up to up to 50MHz and on plots on the right show ±5MHz centred on 12.5MHz.

3rd

12.5MHz Harmonic Fundamental

12.4125MHz Fundamental

These plots show that the 12.5MHz signal is actually not as good as that generated directly at the output of the phase accumulator. Although clearly centred at 12.5MHz the spectrum shows that there is an increased bandwidth. This reflects that the DCM is tracking the input frequency even though it doesn’t really need to do anything. It is rather like balancing on a wall; we know the wall isn’t moving but we still wobble a bit to stay balanced because we are unable to freeze completely due to other influences on us and the need to breath etc!

5MHz/division

 

1MHz/division

10dB/division

 

10dB/division

 

 

 

The full spectrum of the 12.4125MHz case shows how the previous ‘family of spectral components’ associated with the 5ns of cycle jitter have been removed and that the noise floor has been returned to normal levels. The zoomed plot now shows a fundamental with what looks like modulation sidebands rather than fixed spectral components at ±0.74MHz. This again reflects average frequency tracking as well as the removal of the 5ns cycle jitter. Note that an agile frequency component has a lower energy (W/Hz) than a static component.

12.5MHz Fundamental

12.4125MHz Fundamental

±1.3MHz

Hint – If you can synthesize a perfect waveform with a phase accumulator or other direct clock division circuit then it does NOT make sense to use a DCM in frequency aligned mode. In all non integer division cases the DCM will dramatically help jitter performance but some frequency ‘tracking’ must be accepted.

Frequency Generator for the Spartan-3E Starter Kit 12

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Contents Frequency Generator Limitations Double click on ‘installfrequencygenerator.bat’ Design OverviewEdit cursor position mode Edit digit value modeOperating Instructions PicoBlaze Design Size MAP reportFpga Editor view Design Files Direct Digital Synthesis DDS Circuit Diagram ×16PicoBlaze Circuit Diagram On the LCDPhase Accumulator Waveforms Phase Accumulator Spectrum 12.5MHz Harmonic Fundamental 12.4125MHz FundamentalPhase Accumulator Final Output WaveformsFinal Output Spectrum 12.5MHz Fundamental 12.4125MHz Fundamental ±1.3MHzSetting DCM Frequency Aligned Mode Exercises, Experiments and Suggestions

Frequency Generator specifications

The Xilinx Frequency Generator is a versatile and robust solution designed for a variety of applications requiring precise frequency generation and control. This device capitalizes on Xilinx's proven technology in programmable logic, enabling engineers to implement custom frequency generation schemes tailored to specific application needs.

One of the main features of the Xilinx Frequency Generator is its flexible frequency range. It supports a wide spectrum of frequencies, making it suitable for applications in telecommunications, aerospace, automotive, and industrial automation. The ability to generate frequencies from kilohertz to gigahertz opens up possibilities for diverse scenarios, such as clock generation, signal synthesis, and modulation tasks.

Another significant characteristic of this frequency generator is its programmability. Leveraging Xilinx's FPGA architecture, users can easily configure and program the frequency generator to meet changing requirements. This programmability allows for rapid prototyping and design iterations, enabling engineers to achieve optimal configurations with minimal downtime.

The device also employs advanced phase-locked loop (PLL) technology, ensuring excellent stability and low phase noise. PLLs enable the generation of output frequencies that are phase-coherent with an input signal, which is critical for applications requiring precise synchronization. This feature is especially beneficial in communication systems, where accurate timing and frequency stability are essential.

Furthermore, the Xilinx Frequency Generator supports multiple output formats, including sinusoidal, square, and triangle waves. This versatility in signal output enhances its usability across different applications, allowing for easy integration into existing systems.

Another innovative aspect of this frequency generator is its integration with Xilinx's software tools, such as Vivado and ISE. These tools facilitate the design, simulation, and implementation of frequency generation strategies, enhancing productivity and ensuring robustness in design processes.

In addition, the frequency generator's power efficiency is noteworthy. By employing cutting-edge low-power design techniques, it reduces energy consumption without compromising performance, making it an ideal choice for battery-powered or energy-sensitive applications.

All in all, the Xilinx Frequency Generator exemplifies cutting-edge technology in frequency generation, offering flexible configuration, excellent stability, and user-friendly integration, making it a compelling choice for engineers across various industries seeking a reliable frequency generation solution.
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