Wireless receiver circuit with merged ADC and filter
A CMOS hybrid analog-digital receiver core where filtering and gain functions are implemented in the digital domain. The analog portion of the receiver core includes standard circuits such as a low noise amplifier for receiving an RF input signal, and a mixer circuit for down-converting the RF input signal to a base band frequency signal. The analog to digital conversion function is provided by a merged ADC filter circuit having a low order filter stage and an ADC stage. The low order filter stage performs low order filtering of the base band signal to reduce dynamic range and clock requirements for subsequent analog to digital conversion the ADC stage. The two circuit stages are considered to be merged since they both consist of an interconnection of identical transconductance cells, where each transconductance cell includes a series of interconnected CMOS inverters.
1. A wireless device receiver for receiving an RF input signal comprising:
an input stage for converting the RF input signal to a baseband signal; and,
an analog to digital converter (ADC) circuit for receiving the baseband signal and generating a corresponding digital signal, the ADC circuit including
a low order filter stage for receiving the baseband signal, the low order filter stage reducing a dynamic range of the baseband signal to provide a filtered input signal, and
an analog to digital converter stage for converting the filtered input signal into the corresponding digital signal, the analog to digital converter stage and the low order filter stage including identical transconductance cells, each of the identical transconductance cells having an identical predetermined configuration of CMOS inverters.
2. The wireless device receiver of claim 1 , further including a digital processing circuit for executing high order filtering of the corresponding digital signal and digitally applying a gain factor to the filtered digital signal.
3. The wireless device receiver of claim 1 , wherein the input stage and the ADC circuit operate in an analog domain.
4. The wireless device receiver of claim 2 , wherein the digital processing circuit operates in a digital domain.
5. The wireless device receiver of claim 1 , wherein the input stage includes
a low noise amplifier for receiving the RF input signal and generating an intermediate input signal having a predetermined amount of gain, and
a mixer circuit for receiving the intermediate input signal and downconverting the intermediate input signal to a baseband frequency.
6. The wireless device receiver of claim 1 , wherein the analog to digital converter stage includes a delta-sigma analog to digital converter having single bit feedback.
7. The wireless device receiver of claim 1 , wherein the low order filter stage is configured as a second order filter.
8. The wireless device receiver of claim 1 , further including a monitoring circuit for monitoring one transconductance cell and for tuning both the low order filter stage and the analog to digital converter stage.
9. A merged analog to digital converter (ADC) and filter circuit comprising:
a low order filter stage for receiving a baseband signal, the low order filter reducing a dynamic range of the baseband signal to generate a filtered input signal; and
an analog to digital converter stage for converting the filtered input signal into a corresponding digital signal, the analog to digital converter stage and the low order filter stage are configured with an interconnection of identical transconductance cells, each of the identical transconductance cells having an identical predetermined configuration of CMOS inverters.
10. The merged ADC filter circuit of claim 9 , wherein the analog to digital converter stage includes a delta-sigma analog to digital converter core.
11. The merged ADC filter circuit of claim 10 , wherein the delta-sigma analog to digital converter core is configured for single bit feedback.
12. The merged ADC filter circuit of claim 9 , further including a monitoring circuit for monitoring one transconductance cell and for tuning both the low order filter stage and the analog to digital converter stage.