Variable bandwidth filter

1. A semiconductor chip comprising:

a variable bandwidth filter that is configured to filter an analog signal, wherein a bandwidth of a passband of the variable bandwidth filter is dynamically programmable, the variable bandwidth filter comprising a transconductor, the transconductor comprising:

a differential pair of transistors comprising a first transistor and a second transistor, the first transistor has a first drain, the second transistor has a second drain; and

a plurality of tuning transistors that are placed across the first drain of the first transistor and the second drain of the second transistor, wherein a first tuning transistor in the tuning transistors comprises a source and a drain, the source of the first tuning transistor connected to the first drain of the first transistor in the differential pair of transistors, the drain of the first tuning transistor connected to the second drain of the second transistor in the differential pair of transistors.

2. The semiconductor chip of claim 1 , further comprising a control circuit that transmits a control signal to the variable bandwidth filter, the passband of the variable bandwidth filter is set based upon the control signal.

3. The semiconductor chip of claim 2 comprised by a radar receiver.

4. The semiconductor chip of claim 3 , the control circuit generates the control signal based upon a pulse width of radio energy transmitted by a radar transmitter.

5. The semiconductor chip of claim 1 , the variable bandwidth filter comprising a finite impulse response (FIR) filter.

6. The semiconductor chip of claim 5 , the variable bandwidth filter comprising a plurality of FIR filters that are electrically connected to one another in series.

7. The semiconductor chip of claim 5 , the FIR filter comprises a plurality of transconductors, wherein each transconductor in the plurality of transconductors is tunable in transconductance gain.

8. The semiconductor chip of claim 1 , wherein the bandwidth of the passband is tunable from about 1.5 MHz to about 15 MHz.

9. A method comprising:

forming a variable bandwidth filter on a semiconductor chip, wherein a bandwidth of a passband of the variable bandwidth filter is dynamically tunable, wherein forming the variable bandwidth filter comprises forming a transconductor, and wherein forming the transconductor comprises:

forming a differential pair of transistors; and

forming a plurality of tuning transistors that are placed across drains of the transistors in the differential pair such that a source of a first tuning transistor in the plurality of tuning transistors is connected to a drain of a first transistor in the differential pair of transistors and a drain of the first tuning transistor is connected to a drain of a second transistor in the differential pair of transistors.

10. The method of claim 9 , wherein forming the variable bandwidth filter comprises forming a finite impulse response (FIR) filter, the FIR filter comprises a plurality of tunable transconductors.

11. The method of claim 10 , wherein forming the variable bandwidth filter comprises:

forming an anti-alias filter on the semiconductor chip, wherein the anti-alias filter is a low-pass filter that is configured to filter a received analog signal; and

electrically coupling the FIR filter with the anti-alias filter, wherein the FIR filter is configured to receive a derivative of a filtered signal output by the anti-alias filter.

12. The method of claim 11 , wherein forming the variable bandwidth filter further comprises:

forming a sample and hold circuit on the semiconductor chip, wherein the sample and hold circuit is configured to receive the filtered signal output by the anti-alias filter and generate a discretized signal, and further wherein the FIR filter is configured to receive the discretized signal.

13. The method of claim 10 , wherein each of the tunable transconductors is tunable in gain.

14. The method of claim 13 , wherein forming the variable bandwidth filter further comprises:

forming a plurality of FIR filters on the semiconductor chip; and

electrically coupling the plurality of FIR filters to one another.

15. The semiconductor chip of claim 1 , wherein the bandwidth of the passband of the variable bandwidth filter is dynamically programmable by way of the plurality of tuning transistors.

16. The method of claim 9 , wherein the bandwidth of the passband of the variable bandwidth filter is dynamically programmable by way of the plurality of tuning transistors.