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| 型号： | IPR-NCO |
| 厂商： | Altera |
| 文件页数： | 33/54页 |
| 文件大小： | 0K |
| 描述： | IP NCO COMPILER RENEW |
| 标准包装： | 1 |
| 系列： | * |
| 类型： | MegaCore |
| 功能： | 数控振荡器编译器 |
| 许可证： | 续用许可证 |
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4. Functional Description
Numerically Controlled Oscillators
A numerically controlled oscillator (NCO) synthesizes a discrete-time, discrete-valued
representation of a sinusoidal waveform.
There are many ways to synthesize a digital sinusoid. For example, a popular method
is to accumulate phase increments to generate an angular position on the unit circle
and then use the accumulated phase value to address a ROM look-up table that
performs the polar-to-cartesian transformation. You can reduce the ROM size by
using multipliers. Multipliers provide an exponential decrease in memory usage for a
given precision but require more logic.
Another method uses the coordinate rotation digital computer (CORDIC) algorithm
to determine, given a phase rotation, the sine and cosine values iteratively. The
CORDIC algorithm takes an accumulated phase value as input and then determines
the cartesian coordinates of that angle by a series of binary shifts and compares.
f For more information about the CORDIC algorithm, refer to A Survey of CORDIC
Algorithms for FPGAs by Andraka, Ray, FPGA ‘98 Proceedings of the ACM/SIGDA
Sixth International Symposium on Field Programmable Gate Arrays.
In all methods, the frequency at which the phase increment accumulates and the size
directly determines the normalized sinusoidal frequency. (Refer to the equation on
page 4–3 .)
When deciding which NCO implementation to use in programmable logic, you
should consider several parameters, including the spectral purity, frequency
resolution, performance, throughput, and required device resources. Often, you need
to consider the trade-offs between some or all of these parameters.
Spectral Purity
Typically, the spectral purity of an oscillator is measured by its signal-to-noise ratio
(SNR) and its spurious free dynamic range (SFDR).
The SNR of a digitally synthesized sinusoid is a ratio of the signal power relative to
the unavoidable quantization noise inherent in its discrete-valued representation.
SNR is a direct result of the finite precision with which NCO represents the output
sine and cosine waveforms. Increasing the output precision results in an increased
SNR.
The following equation estimates the SNR of a given sinusoid with output precision b :
SNR = 6 b – 1.8
? db ?
Each additional bit of output precision leads to an additional 6 dB in SNR.
November 2013
Altera Corporation
NCO MegaCore Function
User Guide
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相关代理商/技术参数 |
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|---|---|
| IPR-NIOS | 功能描述:开发软件 Nios II MegaCore RENEWAL RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
| IPROBER 520 | 制造商:TTi-Thurlby Thandar Instruments 功能描述:Bulk 制造商:Aim & Thurlby Thandar Instruments 功能描述:PROBE, CURRENT, POSITIONAL, ON PCB TRACK 制造商:Aim & Thurlby Thandar Instruments 功能描述:PROBE, CURRENT, 5MHZ, 2M; Test Probe Ratio:-; Connector Type A:-; Connector Type B:-; Lead Length:2m; Bandwidth:5MHz; SVHC:No SVHC (19-Dec-2012) ;RoHS Compliant: NA |
| IPR-PCI/MT32 | 功能描述:开发软件 PCI 32b MasterTarget MegaCore RENEWAL RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
| IPR-PCI/MT64 | 功能描述:开发软件 PCI 64b MasterTarget MegaCore RENEWAL RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
| IPR-PCI/T32 | 功能描述:开发软件 PCI 32-bit Target MegaCore RENEWAL RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
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