Data converters operate at faster clock speeds each year, enabling RF/microwave receiver, transmitter, and transceiver designers to modify their system architectures to take advantage of improved digital signal processing (DSP). Even as components such as analog-to-digital converters (ADCs) allow elimination of intermediate-frequency (IF) stages in receivers, higher-speed digital-to-analog converters (DACs) are playing critical roles in commercial and military transmitters and in direct-digital synthesis (DDS) of complex RF waveforms.
The new ADC12Dxx00RF family of ADCs from National Semiconductor promises to dramatically change the IF structures of radios in both commercial and military applications. With 12-b resolution at sampling rates to 3.6 GSamples/s, these ADCs can digitize analog input signals through 2.7 GHz. The ADC12Dxx00RF ADCs are each based on a dual-converter architecture that allows dual-channel or interleaved single-channel operation. Five different models offer performance ranging from two channels at 500 MSamples/s to a single channel operating at 3.6 GSamples/s. The fastest member of the new product line is model ADC12D1800RF, with single-channel interleaved sampling rate of 3.6 Gsamples/s and sampling rate of 1.8 GSamples/s per channel in dual-channel mode.
Analog Devices recently added a pair of dual-on-chip ADCs for low-voltage (+1.8-VDC) applications with their models AD9613 and AD9643 converters. Both can operate as dual-channel-multiplexed or single-channel-interleaved devices, at sampling rates to 250 MSamples/s. The AD9613 offers 12-b resolution. It boasts signal-to-noise ratio (SNR) of 69.6 dB full scale (FS) for a 185-MHz input at 250 Msamples/s, with spurious-free dynamic range (SFDR) of 86 dB under the same conditions. the AD9643, with 14-b resolution, achieves SNR of 70.6 dB FS for a 185-MHz input at 250 MSamples/s, with SFDR of 85 dB.
The LTC2143-14, LTC-2144-14, and LTC2145-14 dual ADCs from Linear Technology are designed to run from a single +1.8-VDC supply. The 14-b ADCs operate at maximum respective sampling rates of 80, 105, and 125 MSamples/s. They consume only 113, 149, and 189 mW in dual-channel mode, and only 57, 75, and 95 mW per channel, respectively, at maximum sampling rates. they offer a 750-MHz full-power bandwidth, 73.1-dB FS SNR, and 90-dB SFDR.
The ADCs, which are supplied in 9 x 9 mm QFN packages, offer flexible outputs that can be full-rate CMOS, double-rate CMOS, or double-rate LVDs format.
Earlier this year, Intersil added high-speed 12-, 14-, and 16-b ADCs with sampling rates from 130 to 500 MSamples/s, including the 14-b model IS- LA214P50 ADC with maximum sampling rate of 500 MSamples/s. It achieves an SNR of 72.7 dB FS at 500 MSamples/s and SFDr of 84 dB for a 30-MHz input signal.
The TADC-1000 8-b ADC module from Tektronix Component Solutions is a near plug-in digitizing solution. It provides a single channel of signal capture at rates to 12.5 GSamples/s and two channels of signal capture at 6.25 Gsamples/s each channel. The module's ADCs are designed by Tektronix and fabricated on a silicon-germanium (SiGe) foundry process from IBM. The module requires an external clock and can accept input clock frequencies between 1.6 and 3.125 GHz.
The model MB86064 Dac from Fujitsu Semiconductor integrates a pair of 14-b, DAC cores each capable of better than 1 GSamples/s sampling rates. It is ideal for generating multicarrier transmit signals in third-generation (3G) and fourth-generation (4G) cellular/wireless communications systems.
Finally, the MaX19693 DAC from Maxim Integrated Products is a 12-b device capable of operating at 4 GSamples/s and can be used to generate signals to nearly 2 GHz at bandwidths exceeding 1.5 GHz. The DAC, which is supplied in an 11 x 11 mm CSBGA package, operates from +1.8 to +3.3 VDC and consumes 1180 mW at 4 GSamples/s.