High-speed multi-type substrate analog to digital converter
High conversion rates are achieved in an analog to digital converter by tailoring the substrate type to specific operational elements of the converter. Embodiments place sample and hold processing circuitry on a substrate type having properties that allow for faster processing at high sampling/clock frequencies. Other operational elements of the converter are constructed on at least one other substrate type in keeping with the remainder of the circuitry for which the converter is being implemented. The sample and hold substrate may be implemented on any material which is capable of faster processing, such as silicon germanium, gallium arsenide, silicon bipolar, BiCMOS, and the like. Other portions may be implemented on a more CMOS substrate. Such systems and methods are able to implement analog-to digital conversion for broadband signals at high speeds without the need for extensive timing compensation, while also avoiding problems due to noise from further digital processing circuitry.
1. A tuner system comprising:
input circuitry configured to receive a broadband transmission signal having a plurality of channels;
an analog-to-digital converter (ADC) comprising a sample and hold portion implemented on a first substrate and a conversion portion implemented on a second substrate, said first substrate having superior frequency response characteristics with respect to high sampling frequencies than does said second substrate, wherein said ADC is configured to convert said broadband transmission signal to a digital signal; and
digital signal processing circuitry configured to receive the converted input signal and to tune to at least one channel within said broadband transmission signal.
2. The tuner system of claim 1 wherein said sample and hold portion comprises bipolar sample and hold circuitry.
3. The tuner system of claim 1 wherein the sampling frequency of said sample and hold portion is at least 2.5 GHz.
4. The tuner system of claim 1 wherein said second substrate is CMOS substrate.
5. The tuner system of claim 4 wherein the first substrate is one of:
a silicon germanium, gallium arsenide, silicon bipolar, and a BiCMOS substrate.
6. The tuner system of claim 5 wherein said first substrate further comprises a phase-locked loop (PLL) circuit configured to provide a sampling frequency signal to said sample and hold portion.
7. The tuner of claim 6 wherein said PLL is configured to provide a clock signal to said digital signal processing circuitry which is located on said second substrate.