SBIR-STTR Award

Ridgetop Group will design a radiation-hardened, high speed (2 GS/S) analog-to-digital converter (ADC) with high-bit precision for use in low bit error rate (BER) Quadrature Amplitude Modulation (QAM) demodulator applications. Due to its high linearity and dynamic range, the ADC block can be incorporated into critical communications systems where radiation exposure would otherwise cause degradation of performance. Ridgetop will employ an innovative time-interleaved pipeline ADC approach, based on the most advanced silicon-germanium (SiGe) BiCMOS technology available, providing more than 2 bits higher effective number of bits (ENOB = 11.0 bits) than the best commercially available radiation-tolerant 2 GS/s ADCs (ENOB = 8.9 bits). In addition, the ADC consumes 70% less power than the commercial ADCs, conserving valuable spacecraft power. Due to the inherent radiation tolerance of the SiGe heterojunction bipolar transistors (HBT) and 130 nm thin-oxide CMOS transistors (in combination with radiation-hardening-by-design, (RHBD) techniques) the ADC will be tolerant to 1 Mrad of total ionizing dose (TID) radiation. The ADC will be also sufficiently hardened against single-event effects (SEL) of 120 Mev-cm2/mg, making it an ideal building block for advanced space-based communication systems.

Benefit:
Precision data converters are critical to the performance of high speed Digital Processing (DSP) Systems. The sampling rate and resolution of the converters define the performance aspects of the entire system. With the aggressive performance improvements of 2 GS/S sampling rate, high Effective Number of Bits (ENOB), and low power, this ADC overcomes a significant barrier to higher performance communications systems. Ridgetop’s innovative time-interleaved SiGe-based ADC will improve the resolution, linearity, power consumption and radiation hardness of state-of-the art of ADCs used in advanced communication systems. As a modular, self-contained building block based on a popular, Trusted Foundry process, the ADC will be an important library element for future system designs. The high-performance ADC finds wide applicability in satellite communication systems, space-based radar applications, medical imaging devices, software defined radio applications, power amplifier linearization, high speed data acquisition applications, high speed test and instrumentation equipment.

Keywords:
Analog-To-Digital Converter (Adc), Data Conversion, Quadrature Amplitude Modulation (Qam), Satellite Communication Systems, Silicon-Germanium (Sige), Ionizing Radiation, Radia

In Phase II, Ridgetop Group will develop a high-performance radiation-hardened ADC suitable for use in satellite communication (SATCOM) systems where radiation exposure would otherwise degrade performance. This proposal responds to Air Force topic AF103-092, with the objective of designing a radiation-hardened, high speed (2 GSPS) analog-to-digital data converter (ADC) with high bit precision for use in low bit error rate (BER) 16-quadrature amplitude modulation (QAM) demodulator applications. The significance of this innovation is that high speed and high performance communication systems, incorporating QAM demodulator subsystems, require digitization with extremely high linearity and dynamic range to achieve system performance targets. With the added requirement of radiation hardness, the ADC is a critical chokepoint that must meet demanding standards. Accordingly, Ridgetop’s ADC will be highly linear with an INL and DNL of no more than ±0.5 LSB, a flat gain of <0.1 dB, a channel-to-channel isolation of >80 dB, an operating temperature range of at least -40 to 80 °C, a very high effective number of bits (ENOB) of 11, and a TID tolerance better than 300 krad(Si). The proposed ADC can be used as an integral part of Air Force’s SATCOM low BER, 16 QAM demodulator applications. Ridgetop’s ADC is much more suitable for this purpose than currently commercially available ADCs due to its high radiation hardness and significant performance improvement compared to the radiation-hardened ADCs that are commercially available.

Benefit:
Precision data converters are critical to the performance of high-speed digital signal processing (DSP) systems. The sampling rate and resolution of the converters define the performance aspects of the entire system. Because of its aggressive 2 GSPS sampling rate, high ENOB (11 bits), and low power dissipation (720 mW), this ADC overcomes a significant barrier to higher performance communications systems. Ridgetop’s innovative time-interleaved silicon germanium (SiGe)-based ADC will improve the resolution, linearity, power consumption and radiation hardness of current state-of-the art ADCs used in advanced communication systems. As a modular, self-contained building block from a popular trusted foundry, this ADC will become an important library element in future system designs. High-performance ADCs are widely used in satellite communication systems, space-based radar applications, medical imaging devices, software-defined radio applications, linear power amplifiers, high-speed data acquisition applications, high-speed test and instrumentation equipment, and high-speed digital signal processing (DSP) systems.

Keywords:
Analog-To-Digital Converter (Adc), Data Conversion, Quadrature Amplitude Modulation (Qam), Satellite Communication Systems, Silicon Germanium (Sige), Ionizing Radiation, Radia