Receiver configurable in a plurality of modes

Abstract

Methods and corresponding systems for receiving a radio frequency signal include a receiver capable of switching operating modes and operable to receive the radio frequency signal in any of the operating modes. A metric monitor is coupled to the receiver and operable to provide a metric. A controller is responsive to the metric and operable to switch the receiver between the operating modes. The operating modes can include a zero intermediate frequency (ZIF) mode and a very low intermediate frequency (VLIF) mode. The metric can include a received signal strength indicator (RSSI) and an adjacent channel indicator. The receiver can be configured to operate in the ZIF mode in response to the RSSI value satisfying a threshold and configured to operate in the VLIF mode in response to the RSSI value failing to satisfy the threshold.

What is claimed is: 
     
         1 . A receiver for receiving a selected signal in a communication system, the receiver operable using a plurality of modes, the receiver comprising:
 a first mixer for performing a first mixer function, wherein the first mixer has a signal input, a first local oscillator input, and a first mixer output;   a first local oscillator having a first local oscillator output coupled to the first local oscillator input of the first mixer, and having a first control input for setting a first local oscillator frequency;   a second mixer for performing a second mixer function, wherein the second mixer has a second mixer input coupled to the first mixer output, a second local oscillator input, and a second mixer output for outputting a baseband signal;   a second local oscillator having a second local oscillator output coupled to the second local oscillator input of the second mixer;   a metric monitor for monitoring a metric of the receiver the metric corresponding to the selected signal;   a second mixer bypass for bypassing the second mixer; and   a controller for selecting one of the plurality of modes in response to the metric, wherein the controller is coupled to the first local oscillator, the metric monitor, and the second mixer bypass.   
     
     
         2 . The receiver according to  claim 1  wherein the metric monitor is coupled to the second mixer input, and wherein the metric monitor comprises a received signal strength indication (RSSI) detector for monitoring an RSSI of the selected signal as processed through the receiver up to the second mixer. 
     
     
         3 . The receiver according to  claim 1  wherein the metric monitor is coupled to the first mixer output, and wherein the metric monitor comprises an adjacent channel detector for monitoring a value indicating a presence of an adjacent channel to the selected signal. 
     
     
         4 . The receiver according to  claim 1  wherein the controller for selecting one of the plurality of modes comprises a controller for selecting, in response to the metric, one of a zero intermediate frequency (ZIF) mode and a very low intermediate frequency (VLIF) mode. 
     
     
         5 . The receiver according to  claim 4  wherein the second mixer bypass comprises a switched second mixer bypass signal path for bypassing the second mixer in response to the controller selecting the ZIF mode. 
     
     
         6 . The receiver according to  claim 4  wherein the second mixer bypass comprises a zero frequency function, coupled to the controller and the second local oscillator, for setting the second local oscillator output to a zero frequency in response to the controller selecting the ZIF mode. 
     
     
         7 . The receiver according to  claim 4  wherein the controller for selecting one of the plurality of modes in response to the metric comprises a controller for selecting the VLIF mode in response to the RSSI value being less than an RSSI threshold, and selecting the ZIF mode in response to an RSSI value exceeding the RSSI threshold. 
     
     
         8 . The receiver according to  claim 4  wherein the controller for selecting one of the plurality of modes in response to the metric comprises a controller for selecting the VLIF mode in response to the RSSI value being less than an RSSI threshold and an adjacent channel indicator indicating an absence of an adjacent channel, and for selecting the ZIF mode in response to the RSSI value exceeding the RSSI threshold and the adjacent channel indicator indicating a presence of the adjacent channel. 
     
     
         9 . A method in a receiver for receiving a selected signal in a communication system, the receiver operable using a plurality of modes, the method comprising:
 performing a first mixer function with a first mixer, wherein the first mixer has a signal input, a first local oscillator input, and a first mixer output;   providing a first local oscillator signal using a first local oscillator, the first local oscillator having a first local oscillator output coupled to the first local oscillator input of the first mixer, and having a first control input for setting a first local oscillator frequency;   performing a second mixer function with a second mixer, wherein the second mixer has a second mixer input coupled to the first mixer output, a second local oscillator input, and a second mixer output for outputting a baseband signal;   providing a second local oscillator signal using a second local oscillator, the second local oscillator having a second local oscillator output coupled to the second local oscillator input of the second mixer;   monitoring a metric of the receiver using a metric monitor, the metric corresponding to the selected signal;   selectively bypassing the second mixer using a second mixer bypass; and   selecting, using a controller, one of the plurality of modes in response to the metric, wherein the controller is coupled to the first local oscillator, the metric monitor, and the second mixer bypass.   
     
     
         10 . The method according to  claim 9  wherein the monitoring a metric comprises monitoring an RSSI of the selected signal as processed through the receiver up to the second mixer, the metric monitor further coupled to the second mixer input, and comprising a received signal strength indication (RSSI) detector. 
     
     
         11 . The method according to  claim 9  wherein the monitoring a metric comprises monitoring a value indicating a presence of an adjacent channel to the selected signal, the metric monitor further coupled to the first mixer output, and comprising an adjacent channel detector. 
     
     
         12 . The method according to  claim 9  wherein the selecting, using a controller, one of the plurality of modes in response to the metric further comprises selecting in response to the metric, one of a zero intermediate frequency (ZIF) mode and a very low intermediate frequency (VLIF) mode. 
     
     
         13 . The method according to  claim 12  wherein the selectively bypassing the second mixer using a second mixer bypass comprises using a switched second mixer bypass signal path for bypassing the second mixer in response to the controller selecting the ZIF mode. 
     
     
         14 . The method according to  claim 12  wherein the second mixer bypass comprises a zero frequency function, coupled to the controller and the second local oscillator, for setting the second local oscillator output to a zero frequency in response to the selecting the ZIF mode. 
     
     
         15 . The method according to  claim 12  wherein the selecting one of the plurality of modes in response to the metric comprises selecting the VLIF mode in response to the RSSI value being less than an RSSI threshold, and selecting the ZIF mode in response to an RSSI value exceeding the RSSI threshold. 
     
     
         16 . The method according to  claim 12  wherein the selecting one of the plurality of modes in response to the metric comprises selecting the VLIF mode in response to the RSSI value being less than an RSSI threshold and an adjacent channel indicator indicating an absence of an adjacent channel, and selecting the ZIF mode in response to the RSSI value exceeding the RSSI threshold and the adjacent channel indicator indicating a presence of the adjacent channel.