DYNAMIC BANDWIDTH CONTROL SCHEME OF A FRAC-N PLL IN A RECEIVER
A receiver includes a mixer, a filter, a received signal strength indicator, and a control loop. The mixer is adapted to convert the frequency of a received signal. The filter is adapted to filter out undesired signals that may be present in the output signal of the mixer. The received signal strength indicator is adapted to detect blocker (also known as jammer) signals that may be present in the output signal of the low-pass filter and generate a feedback signal in response. The control loop is adapted to vary its bandwidth in response to the feedback signal of the received signal strength indicator. The control loop supplies an oscillating signal to the mixer.
1 . A receiver comprising:
a mixer;
a filter responsive to the mixer;
a received signal strength indicator (RSSI) adapted to detect one or more blocker signals; and
a control loop adapted to vary its bandwidth in response to an output signal of the RSSI, said control loop supplying an oscillating signal to said mixer.
2 . The receiver of claim 1 wherein said control loop is adapted to have a first bandwidth in response to detection of the blocker signal by the RSSI, and a second bandwidth in response to no detection of the blocker signal by the RSSI.
3 . The receiver of claim 1 wherein said RSSI detects the blocker signal if the blocker signal is detected as having a strength greater than a predefined threshold value, and wherein said RSSI does not detect the blocker signal if the blocker signal is not detected as having a strength greater than the predefined threshold value
4 . The receiver of claim 1 wherein said receiver is a wireless receiver.
5 . The receiver of claim 1 wherein the bandwidth of the control loop is varied by varying a current supplied to a charge pump disposed in the control loop.
6 . The receiver of claim 1 wherein said control loop is selected from a group consisting of a phased-locked loop and a delay-locked loop.
7 . A method of controlling a bandwidth of a control loop, the method comprising:
setting a feedback signal to a first state if the received signal is detected as having a strength greater than a first predefined threshold value;
setting the feedback signal to a second state if the received signal is detected as not having a strength greater than the first predefined threshold value; and
varying a bandwidth of a control loop in response to the feedback signal.
8 . The method of claim 7 further comprising:
using an output signal of the control loop to control a conversion frequency of the received signal.
9 . The method of claim 8 further comprising:
filtering the frequency converted signal.
10 . The method of claim 8 wherein said control loop is a phase-locked loop.
11 . The method of claim 8 wherein said received signal is received wirelessly.
12 . The method of claim 8 further comprising:
varying a bandwidth of a control loop in response to the feedback signal by varying a current supplied to the control loop.