Wideband Direct Digital Synthesizer

A new low power high speed design scheme was developed for GaAs HBT mixed signal circuits. In this new design scheme, most of the transistors are biased in quasi-saturation mode to reduce power supply from 5 V to 3.3 V. Due to electron drift velocity overshoots at low electric field for GaAs material, all the analysis including DC, RF/speed and thermal effects favor the GaAs HBT circuits biased in quasi-saturation mode for higher speed operation. This new design scheme offers two DDS architectures to achieve the analog bandwidth greater than 2.25 GHz. Low power consumption has been considered in the design from building block level up to architecture level. The conventional single sampling rate DDS was simulated with 4.5 GHz clock to have the worst spur of 60 dBc across the 2.25 GHz Nyquist band. The innovative double sampling rate DDS was simulated at 3 GHz and 4.5 GHz clock rates. At 3 GHz clock, the analog output is 6 Gsps and the worst SFDR across the 3 GHz Nyquist band is 50 dB. At 4.5 GHz clock rate, the worst SFDR across 4.5 GHz Nyquist band is limited to ~ 40 dB which can be further optimized in Phase II. Two wafer lots will be fabricated in Phase II. The packaged broadband DDS devices will be delivered with evaluation boards. A generic frequency hopping spread spectrum module with the developed DDS ICs will be demonstrated. BENEFIT: We have established many customer bases through the selling of our 2 ~ 3 GHz DDS and other 2 ~ 8 Gsps DAC-related products in the past 4 years. These customers include both defense industries and commercial companies. The applications covered satellite communication spread spectrum terminals, Radar, EW, DRFM, Software Defined Radio, scene generation, fast tuning frequency synthesizers, WLAN modem, hard drive testers and memory testers. We have frequently got requests from these customers about the availability and schedule for the next generation wider bandwidth DDS products. As the frequency band of commercial wireless communication systems are pushing from 900 MHz , 1.9 GHz to 5.8 GHz and even higher such as 60 GHz WPAN, there are big commercial opportunities to use the wideband DDS for frequency hopping wireless data modem applications. We believe once we release the availability of the new DDS product with wide bandwidth, not only many of our existing customers will start to design with this new product to improve their system performance, but also it will penetrate into consumer wireless communication markets. The commercialization channels already exist for Euvis and there will have more commercial markets to be explored as the wider bandwidth DDS is available.