The Elusive Software-Defined Radio

National Instruments' PCI-5640R reconfigurable IF transceiver uses the Xilinx Virtex-II Pro FPGA and Lab-VIEW FPGA for communications system design and research in universities and industry. The 5640R is a two-channel IF input and two-channel IF output PCI board with 2 Mbytes of SRAM. ICs handle DDC and DUC, thereby offloading the FPGA.

Keep in mind that you won't get very far in your designs without a way to test and measure your system. Tektronix's AWG400 family of arbitrary waveform generators (AWGs) offers one way to test an SCA receiver. With the RSA6100A real-time spectrum analyzer, designers can test SDR transmitters at frequencies to 14 GHz, with a bandwidth up to 110 MHz and a SFDR of 73 dB (Fig. 6).

SDR isn't for every wireless application. It's even overkill for many simple wireless tasks. But it will gradually find its way into more commercial and consumer products. For now, it's a high-end technology that will greatly benefit satellite communications and a wide range of military needs—not only JTRS radios, but also signals intelligence (SIGINT) for the NSA, CIA and DIA, and electronic warfare (EW) equipment.

One big hope is that SDR will help solve the widespread incompatibility of the public safety, public service, and military radios that need to communicate during emergencies. Also anticipated is increased application in cellphone and broadband wireless basestations.