System and method for tuning baseband filters in wireless transceivers

A method for tuning an analog baseband filter in a wireless receiver using a wireless transmitter co-located with the wireless receiver, the wireless receiver having an analog-to-digital (ADC) at an output of the analog baseband filter, the method comprising:

• cancelling a DC offset in the wireless receiver, wherein the cancelling comprises:
• injecting a zero signal into the wireless transmitter;
• coupling an first radio frequency (RF) signal generated by the wireless transmitter at the input of the wireless receiver, wherein the first radio frequency (RF) signal is resultant from the zero signal;
• measuring a magnitude of a signal at the output of the ADC resulting from the first radio frequency (RF) signal, producing the DC offset;
• and
• applying a digital control word based on the DC offset to a second ADC to cancel the DC offset;
• coupling a second radio frequency (RF) signal generated by the wireless transmitter at an input of the wireless receiver, the second radio frequency (RF) signal having a desired frequency;
• measuring a magnitude of the coupled second radio frequency (RF) signal at an output of the ADC, wherein the magnitude is measured at the desired frequency;
• and
• adjusting a corner frequency of the filter in response to the determining that the measured magnitude differs from a specified value.

A method for tuning an analog baseband filter in a wireless receiver using a wireless transmitter co-located with the wireless receiver, the wireless receiver having an analog-to-digital (ADC) at an output of the analog baseband filter, the method comprising:

• coupling a radio frequency (RF) signal generated by the wireless transmitter at an input of the wireless receiver, the radio frequency (RF) signal having a desired frequency;
• measuring a magnitude of the coupled radio frequency (RF) signal at an output of the ADC, wherein the magnitude is measured at the desired frequency;
• adjusting a corner frequency of the filter in response to the determining that the measured magnitude differs from a specified value;
• and
• wherein the analog baseband filter comprises a plurality of analog baseband filters, and the method is repeated for each analog baseband filter in the plurality of analog baseband filters, wherein only an analog baseband filter being tuned is active and all other analog baseband filters are bypassed or deactivated.

A transceiver comprising:

• a transmitter to generate and transmit radio frequency (RF) signals, and to generate an RF tuning signal having a desired frequency component;
• and
• a receiver co-located with the transmitter, the receiver having an analog baseband filter tunable by using a tuning RF signal parasitically coupled from the transmitter, the receiver to receive RF signals from over the air by an antenna, wherein the receiver comprises:
• a low noise amplifier coupled to the antenna, the low noise amplifier to amplify a received signal from the antenna and a signal parasitically coupled from the transmitter;
• a filter having a tunable corner frequency, the filter coupled to the low noise amplifier, the filter to eliminate signals outside a frequency band of interest, as specified by the tunable corner frequency, from the received RF signals;
• an analog-to-digital-converter coupled to the filter, the analog-to-digital-converter configured to digitize an output of the filter;
• a detector coupled to the analog-to-digital-converter, the detector configured to compare the digitized output of the filter at the corner frequency with a specified value;
• and
• a processor coupled to the detector and to the filter, the processor configured to select a filter control word to tune the corner frequency of the filter if the digitized output of the filter differs from the specified value, wherein the filter comprises:
• a low pass filter coupled to the low noise amplifier, the low pass filter to eliminate interferers from the received RF signal, the low pass filter comprising,
• a mixer coupled to the low noise amplifier and an RF signal source, the mixer to demodulate the coupled signal with a local oscillator signal provided by the RF signal source, the local oscillator signal having a frequency component substantially equal to the desired frequency component, and
• a capacitor coupled to the mixer;
• and
• a second filter coupled to the low pass filter, the second filter to further eliminate interferers from the received RF signal.

A method for tuning an analog baseband filter in a wireless receiver using a wireless transmitter co-located with the wireless receiver, the wireless receiver having an analog-to-digital (ADC) at an output of the analog baseband filter, the method comprising:

• cancelling a DC offset in the wireless receiver;
• coupling a first radio frequency (RF) signal generated by the wireless transmitter at an input of the wireless receiver, the first radio frequency (RF) signal having a desired frequency;
• measuring a reference value, comprising;
• injecting a direct current (DC) signal with an appropriate magnitude into the wireless transmitter;
• coupling a second radio frequency (RF) signal generated by the wireless transmitter at the input of the wireless receiver, wherein the second radio frequency (RF) signal is resultant from the DC signal;
• and
• measuring a magnitude of the coupled first radio frequency (RF) signal at an output of the ADC, wherein the magnitude is measured at the desired frequency;
• and
• adjusting a corner frequency of the filter in response to the determining that the measured magnitude differs from a specified value, wherein the cancelling comprises:
• injecting a zero signal into the wireless transmitter;
• coupling a third radio frequency (RF) signal generated by the wireless transmitter at the input of the wireless receiver, wherein the third radio frequency (RF) signal is resultant from the zero signal;
• measuring a magnitude of a signal at the output of the ADC resulting from the third radio frequency (RF) signal, producing the DC offset;
• and
• applying a digital control word based on the DC offset to a second ADC to cancel the DC offset.