摘要: Until recently radio transmitters and receivers were almost exclusively implemented with analog electronic components. However, a new approach is now becoming popular -- one that employs digital electronics to implement most of th... 展开 Until recently radio transmitters and receivers were almost exclusively implemented with analog electronic components. However, a new approach is now becoming popular -- one that employs digital electronics to implement most of the analog signal processing functions in the radio. The evolution in radio system design is driven by the ever increasing speed and decreasing cost of microprocessors and high performance analog-to-digital (ADC) and digital-to-analog (DAC) converters. It is no longer uncommon to sample a received signal at the intermediate frequency (IF) stage and process the signal with numerical algorithms using specialized- digital signal processing (DSP) hardware. The DSP hardware performs a variety of operations on the signal including downconversion, demodulation, and filtering; all of which are inherently continuous-time (i.e., analog) processes. Modern field programmable gate arrays can implement functions beyond the capabilities of today's DSP micro-processors. In fact, they have the potential to provide performance increases of an order of magnitude or better over traditional DSP microprocessors, but with the same flexibility. These devices can provide the programmability of software, the high speed of hardware and can be reconfigured in-circuit with no physical change to the hardware. In fact, FPGAs are really soft hardware, in that they are a good compromise between flexible all-software approaches which unfortunately limit throughput, and custom hardware implementations, which are more expensive and inflexible. FPGAs offer a powerful approach -- an architecture tailored to the specific application. 收起