Tunable notch filter using feedback through an existing feedback receiver

Abstract

A wireless communication device configured for reducing Tx leakage in a receive signal is described. The wireless communication device includes a transceiver chip. The transceiver chip includes a receiver, a feedback receiver and a transmitter. The wireless communication device also includes a Tx leakage signal reduction module. The Tx leakage signal reduction module reuses the feedback receiver.

What is claimed is: 
     
         1 . A wireless communication device configured for reducing Tx leakage in a receive signal, comprising:
 a transceiver chip, comprising:
 a receiver; 
 a feedback receiver; and 
 a transmitter; and 
   a Tx leakage signal reduction module, wherein the Tx leakage signal reduction module reuses the feedback receiver.   
     
     
         2 . The wireless communication device of  claim 1 , wherein the Tx leakage signal reduction module comprises a notch filter that reduces Tx leakage in the receive signal. 
     
     
         3 . The wireless communication device of  claim 2 , wherein the notch filter is located on the transceiver chip, and wherein the notch filter is coupled to an output of a low noise amplifier that receives the receive signal. 
     
     
         4 . The wireless communication device of  claim 2 , wherein the notch filter is located off the transceiver chip, wherein the notch filter receives the receive signal, and wherein an output of the notch filter is coupled to an input of a low noise amplifier on the transceiver chip. 
     
     
         5 . The wireless communication device of  claim 1 , wherein the receiver provides a feedback signal to the feedback receiver, and wherein the feedback receiver provides a digital leakage reduction signal to the Tx leakage signal reduction module. 
     
     
         6 . The wireless communication device of  claim 5 , wherein the digital leakage reduction signal tunes a notch filter in the Tx leakage signal reduction module to minimize Tx leakage in the receive signal. 
     
     
         7 . The wireless communication device of  claim 6 , wherein the notch filter comprises a first variable capacitor, a second variable capacitor, a first resistor, a second resistor and an inductor. 
     
     
         8 . The wireless communication device of  claim 6 , wherein the notch filter is tuned to provide reliable rejection of Tx leakage across process, voltage and temperature. 
     
     
         9 . The wireless communication device of  claim 5 , wherein the digital leakage reduction signal tunes a balancing impedance in a hybrid transformer on the wireless communication device. 
     
     
         10 . The wireless communication device of  claim 9 , wherein the hybrid transformer comprises a first inductor, a second inductor and a third inductor, and wherein the balancing impedance is coupled between the second inductor and ground. 
     
     
         11 . The wireless communication device of  claim 5 , wherein the feedback signal is provided to a feedback downconverter in the feedback receiver by a first amplifier in a cascode stage in the receiver. 
     
     
         12 . The wireless communication device of  claim 11 , wherein an output of the feedback downconverter is coupled to an analog-to-digital converter via a feedback baseband filter, and wherein an output of the analog-to-digital converter is converted to the digital leakage reduction signal by a digital signal processor. 
     
     
         13 . A method for reducing Tx leakage in a receive signal, comprising:
 receiving the receive signal;   processing the receive signal in a receiver;   providing a feedback signal from the receiver to a feedback downconverter;   converting the feedback signal to a digital leakage reduction signal using an analog-to-digital converter and a digital signal processor; and   using the digital leakage reduction signal to reduce Tx leakage in the receive signal.   
     
     
         14 . The method of  claim 13 , further comprising:
 downconverting the feedback signal using the feedback downconverter; and   filtering the downconverted feedback signal using a feedback baseband filter.   
     
     
         15 . The method of  claim 13 , wherein processing the receive signal in the receiver comprises passing the receive signal through a notch filter. 
     
     
         16 . The method of  claim 13 , wherein the method is performed by a wireless communication device comprising:
 a transceiver chip, comprising:
 the receiver; 
 a feedback receiver; and 
 a transmitter; and 
   a Tx leakage signal reduction module, wherein the Tx leakage signal reduction module reuses the feedback receiver.   
     
     
         17 . The method of  claim 16 , wherein the Tx leakage signal reduction module comprises a notch filter, and further comprising performing process tuning on the notch filter using the digital leakage reduction signal. 
     
     
         18 . The method of  claim 17 , wherein the notch filter is located on the transceiver chip, and wherein the notch filter is coupled to an output of a low noise amplifier that receives the receive signal. 
     
     
         19 . The method of  claim 17 , wherein the notch filter is located off the transceiver chip, wherein the notch filter receives the receive signal, and wherein an output of the notch filter is coupled to an input of a low noise amplifier on the transceiver chip. 
     
     
         20 . The method of  claim 16 , wherein the receiver provides the feedback signal to the feedback receiver, and wherein the feedback receiver provides the digital leakage reduction signal to the Tx leakage signal reduction module. 
     
     
         21 . The method of  claim 20 , wherein the digital leakage reduction signal tunes a notch filter in the Tx leakage signal reduction module to minimize Tx leakage in the receive signal. 
     
     
         22 . The method of  claim 21 , wherein the notch filter comprises a first variable capacitor, a second variable capacitor, a first resistor, a second resistor and an inductor. 
     
     
         23 . The method of  claim 22 , further comprising:
 determining a measured notch frequency of the notch filter;   determining a process error;   calculating a first capacitor code and a second capacitor code that meet requirements for a channel; and   applying the first capacitor code to the first variable capacitor and the second capacitor code to the second variable capacitor.   
     
     
         24 . The method of  claim 23 , wherein determining a measured notch frequency of the notch filter comprises:
 applying a transmit tone on three different frequencies to the notch filter;   measuring a DC gain through the feedback receiver;   calculating a gradient; and   determining the measured notch frequency using a gradient search algorithm.   
     
     
         25 . The method of  claim 21 , wherein the notch filter is tuned to provide reliable rejection of Tx leakage across process, voltage and temperature. 
     
     
         26 . The method of  claim 20 , wherein the digital leakage reduction signal tunes a balancing impedance in a hybrid transformer on the wireless communication device. 
     
     
         27 . The method of  claim 26 , wherein the hybrid transformer comprises a first inductor, a second inductor and a third inductor, and wherein the balancing impedance is coupled between the second inductor and ground. 
     
     
         28 . The method of  claim 20 , wherein the feedback signal is provided to a feedback downconverter in the feedback receiver by a first amplifier in a cascode stage in the receiver. 
     
     
         29 . The method of  claim 28 , wherein an output of the feedback downconverter is coupled to an analog-to-digital converter via a feedback baseband filter, and wherein an output of the analog-to-digital converter is provided to a digital signal processor that outputs the digital leakage reduction signal. 
     
     
         30 . An apparatus for reducing Tx leakage in a receive signal, comprising:
 means for receiving the receive signal;   means for processing the receive signal in a receiver;   means for providing a feedback signal from the receiver to a feedback downconverter;   means for converting the feedback signal to a digital leakage reduction signal; and   means for using the digital leakage reduction signal to reduce Tx leakage in the receive signal.   
     
     
         31 . The apparatus of  claim 30 , further comprising:
 means for downconverting the feedback signal; and   means for filtering the downconverted feedback signal.   
     
     
         32 . The apparatus of  claim 30 , wherein the means for processing the receive signal in the receiver comprise means for passing the receive signal through a notch filter. 
     
     
         33 . The apparatus of  claim 30 , wherein the apparatus is a wireless communication device comprising:
 a transceiver chip, comprising:
 the receiver; 
 a feedback receiver; and 
 a transmitter; and 
   a Tx leakage signal reduction module, wherein the Tx leakage signal reduction module reuses the feedback receiver.   
     
     
         34 . A computer-program product for reducing Tx leakage in a receive signal, the computer-program product comprising a non-transitory computer-readable medium having instructions thereon, the instructions comprising:
 code for causing a wireless communication device to receive the receive signal;   code for causing the wireless communication device to process the receive signal in a receiver;   code for causing the wireless communication device to provide a feedback signal from the receiver to a feedback downconverter;   code for causing the wireless communication device to convert the feedback signal to a digital leakage reduction signal using an analog-to-digital converter and a digital signal processor; and   code for causing the wireless communication device to use the digital leakage reduction signal to reduce Tx leakage in the receive signal.   
     
     
         35 . The computer-program product of  claim 34 , wherein the instructions further comprise:
 code for causing the wireless communication device to downconvert the feedback signal; and   code for causing the wireless communication device to filter the downconverted feedback signal.   
     
     
         36 . The computer-program product of  claim 34 , wherein the code for causing the wireless communication device to process the receive signal in the receiver comprise code for causing the wireless communication device to pass the receive signal through a notch filter. 
     
     
         37 . The computer-program product of  claim 34 , wherein the wireless communication device comprises:
 a transceiver chip, comprising:
 the receiver; 
 a feedback receiver; and 
 a transmitter; and 
   a Tx leakage signal reduction module, wherein the Tx leakage signal reduction module reuses the feedback receiver.