US 20050021580 A1 Abstract A time domain data converter with output frequency domain conversion. A data conversion circuit is operable to receive a signal in the time domain and provide an output in the frequency domain. It includes a data converter for converting data from an analog format to a digital format in the time domain. It also includes a processor for processing the data in the digital format output from the data converter through a time domain/frequency domain transform to provide data in the digital format in the frequency domain.
Claims(20) 1. A data conversion circuit for receiving a signal in the time domain and providing an output in the frequency domain, comprising:
a data converter for converting data from an analog format to a digital format in the time domain; a transform processor for processing the data in the digital format output through a time domain/frequency domain transform to provide data in a digital format in the frequency domain; and an interface for interfacing the output of said data converter to the input of said transform processor. 2. The data conversion circuit of 3. The data conversion circuit of 4. The data conversion circuit of _{s }and wherein said time domain/frequency domain transform operates on a predetermined number of samples as a block of samples, wherein said calculations performed by said time domain/frequency domain transform require all of said samples in said block. 5. The data conversion circuit of 6. The data conversion circuit of 7. The data conversion circuit of 8. The data conversion circuit of 9. The data conversion circuit of 10. The data conversion circuit of 11. The data conversion circuit of 12. The data conversion circuit of 13. The data conversion circuit of 14. The data conversion circuit of 15. The data conversion circuit of 16. The data conversion circuit of 17. The data conversion circuit of 18. The data conversion circuit of 19. A method for receiving a signal in the time domain and providing an output in the frequency domain, comprising the steps of:
converting data with a data converter from an analog format to a digital format in the time domain; processing the data with a transform processor in the digital format output through a time domain/frequency domain transform to provide data in a digital format in the frequency domain; and interfacing the output of the data converter to the input of the transform processor. 20. The method of Description This application is a Continuation application of U.S. Ser. No. 09/376,761, filed on Aug. 17, 1999, titled “TIME DOMAIN DATA CONVERTER WITH OUTPUT FREQUENCY DOMAIN CONVERSION (Atty. Dkt. No. HCAI-24,725.), and is related to U.S. Pat. No. 6,369,738, issued on Apr. 9, 2002, titled “TIME DOMAIN/FREQUENCY DOMAIN DATA CONVERTER WITH DATA READY FEATURE, (Atty. Dkt. HCAI-24,766). The present invention pertains in general to data converters and, more particularly, to a time domain data converter with the output thereof processed through a frequency domain transform to provide an output in the frequency domain. Conventional data converters provide either conversion from the analog domain to the digital domain in a typical analog-to-digital converter, or from the digital domain to an analog domain as a digital-to-analog converter. Typical analog-to-digital (A/D) converters of the delta sigma type provide some type of analog modulator for providing the initial data conversion, which is then followed by some type of filtering step. Conventionally, the filtering is performed in part in the digital domain. This requires some type of digital processing of the digital output of the modulator in the form of a digital filter such as a Finite Impulse Response (FIR) filter. However, the digital values output therefrom are values that exist in the time domain. In some applications, it is desirable to determine information in the frequency domain after the conversion operation. Such applications as spectrum analyzers, for example, require such information. Therefore, the output of the data converter in the digital domain is then processed through some type of transform for converting time domain information to frequency domain information, this all completed in the digital domain. The types of transform engines that are utilized to convert time domain information to digital domain information typically utilize some type of Fourier Transform, the most common being a Discrete Fourier Transform (DFT). The DFT is a one-to-one mapping of any finite sequence {y(r)}, r=0,1,2 . . . , N-1 of N complex samples onto another sequence. This is defined by the following relationship:
In general, a DFT algorithm requires a plurality of multiplication/accumulation operations. To reduce the number of these multiplication/accumulations, a Fast Fourier Transform (FFT) can be implemented to provide a rapid means for computing a DFT with Nlog In general, there does not exist a commercial monolithic solution providing both the benefits of a data converter with that of a frequency domain converter such that an analog input can be received, converted to the digital domain and this digital value processed to provide a frequency domain output. In general, typical solutions utilize a data converter that provides a digital value in the time domain which is then input to a processor. This processor can be in the form of a microcontroller or a DSP. A data converter, due to its inherent construction, basically provides the ability to convert an analog input signal to a digital time domain output signal with a defined bit-resolution. This, of course, provides an output in the time domain. When processing this time domain signal to provide a frequency domain output, the processor is programmed to process some type of Discrete Fourier Transform or Fast Fourier Transform. Any type of algorithm that provides such a transform can be utilized. However, in order for a designer to utilize such a transform, this requires programming of the processor or microcontroller. Therefore, if an existing design must be upgraded to provide such a function or be required to process in the frequency domain, then a more complex DSP or microcontroller must be utilized. This is due to the fact that any processing in the frequency domain requires a more complex processing capability. The result is that an upgrade to a frequency domain solution from a time domain solution will probably require the designer to change his design to incorporate a much more complex processing section, in addition to also requiring a significant amount of programming of that processing section, this programming being the most expensive aspect of such an upgrade. It is desirable to utilize the pre-upgrade processing section, which is typically a relatively simple processor, and merely upgrade the data converter. However, the mere change of a design to process in the frequency domain as opposed to the time domain will necessitate additional processing capability and programming. The present invention disclosed and claimed herein comprises a data conversion circuit for receiving a signal in the time domain and providing an output in the frequency domain. A data converter is provided for converting data from an analog format to a digital format in the time domain. A processor is provided for processing the data in the digital format output from the data converter through a time domain/frequency domain transform to provide output data in the frequency domain. For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying Drawings in which: Referring now to Typically, the data converter The output of the IC Referring now to In general, by incorporating both the data conversion operation and the frequency domain transformation circuit in the same monolithic circuit, a single measurement module is provided wherein the functions of a data converter and a processing circuit are incorporated into a single monolithic solution, which processing circuit can incorporate the functions that are normally associated with DFT-type calculations. As will be described hereinbelow, this is facilitated without requiring the full capability of a DSP. Referring now to Referring now to The output of the A/D converter Once the time domain information has been processed, it is output on the bus Typically, the DFT algorithm will operate on a block of samples which will then provide frequency information in various “bins.” These frequency bins are generated such that one is generated for each input sample output from the data converter The output of the transform processor engine The post processor Although the time domain processor Referring now to The timing information is generally provided by a master clock The frequency domain output of the transform operation can be stored in frequency bins Since the entire string of processing for the time domain and the frequency domain is contained on a single integrated circuit chip, this removes the requirement for an I/O interface between two chips. As such, it can be seen that the various bus widths can be increased internal to the chip and then decreased or truncated for output therefrom. For example, the AID converter could be realized with a SAR to provide a 12-bit output. The digital filter section Referring now to In order to control the overall operation of the frequency domain integrated circuit described hereinabove, a control interface Referring now to Referring now to Referring now to Referring now to The transforms described hereinabove were the DFT and the FFT transforms. However, there were many other transforms that can be utilized in transforming a time domain value to a frequency domain value. These transforms can result in significantly less calculations. For example, the Goertzel transform is a transform that allows the transform to be carried out for a single bin with a relatively simplistic algorithm. This requires a very small number of clock cycles in order to perform this operation. This algorithm is described in Goertzel, “An Algorithm for the Evaluation of Finite Trigonometric Series,” American Math Monthly, 65, pp. 34-35, January 1958, which reference is incorporated herein by reference. Therefore, if only the information for a single bin were required, the Goertzel algorithm would be sufficient and this algorithm could easily be facilitated in a hardware application. Further, since the Goertzel algorithm is relatively straight forward, it would be relatively easy to change to a different bin number. Referring now to Referring now to The output of the transform block This receives a control signal external to the system to select a bin for output therefrom. Further, there could be a situation wherein the bins are sequentially output and the control block Although the preferred embodiment has been described in detail, it should be understood that various changes, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Referenced by
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