Saw-less receiver with notch at transmitter frequency
View Patent ↗A circuit includes a local oscillator of a transmitter, the local oscillator to generate a transmitter local oscillator signal. A switch controlled by the transmitter local oscillator signal connects with a baseband impedance element to generate a notch frequency signal. The notch frequency signal is added to a transmitter leakage signal to attenuate the transmitter leakage signal prior to demodulation of a desired receiver signal by a receiver.
1. A circuit, comprising:
a local oscillator, the local oscillator configured to generate a transmitter local oscillator signal;
a low noise amplifier; and
a switch configured to be controlled by the transmitter local oscillator signal, the switch coupled to an impedance element configured to generate a notch frequency signal, the switch configured to apply the notch frequency signal to a transmitter leakage signal in a receiver signal output by the low noise amplifier to attenuate the transmitter leakage signal prior to demodulation of the receiver signal.
2. The circuit of claim 1 , where the impedance element includes an inverter coupled to a resistor capacitor (RC) filter and a frequency limiting capacitor.
3. The circuit of claim 1 , where the impedance element includes an operational amplifier coupled to a feedback resistor.
4. The circuit of claim 1 , further comprising a transmitter path, the transmitter leakage signal imparted by the transmitter path, the transmitter path comprising:
a buffer configured to store a pre-distortion signal; and
a digital configured to analog converter coupled to the buffer.
5. The circuit of claim 4 , where the pre-distortion signal is applied to communication information processed by the digital to analog converter to pre-distort the communication information.
6. The circuit of claim 5 , where the impedance element is further configured to generate the pre-distortion signal.
7. The circuit of claim 1 , where the impedance element is configured to generate the notch frequency based on I+, I−, Q+ and Q− signals generated by the local oscillator.
8. The circuit of claim 1 , where the impedance element is configured to band pass filter the notch frequency signal.
9. A circuit, comprising:
a transmitter including a transmitter mixer, the transmitter mixer to generate a modulated transmitter signal based on a local oscillator signal;
a receiver including a receiver mixer configured to receive a transmitter leakage signal from the transmitter; and
an impedance element including an inverter coupled to a resistor capacitor (RC) filter and a frequency limiting capacitor, the impedance element coupled to the receiver mixer, the impedance element configured to generate a notch frequency signal, the receiver mixer configured to apply the notch frequency signal to the transmitter leakage signal to attenuate the transmitter leakage signal.
10. The circuit of claim 9 , where the transmitter further includes a digital to analog converter coupled to the transmitter mixer, where the digital to analog converter is configured to send a communication signal to the transmitter mixer, and where the transmitter mixer is configured to apply a pre-distortion signal to the communication signal to pre-distort the communication signal.
11. The circuit of claim 10 , further including a Class 2 power amplifier driver coupled to the transmitter mixer to drive the modulated transmitter signal.
12. The circuit of claim 9 , further including a low noise amplifier coupled to the receiver mixer, where the receiver mixer configured to apply the notch frequency signal to the transmitter leakage signal after the signal passes the low noise amplifier.
13. The circuit of claim 9 , where the impedance element includes an operational amplifier coupled to a feedback resistor.
14. The circuit of claim 9 , where the impedance element is configured to band pass filter the notch frequency signal.
15. The circuit of claim 9 , where the receiver is configured to demodulate a receiver signal including the transmitter leakage signal.
16. The circuit of claim 15 , where the receiver mixer is configured to apply the notch frequency signal prior to demodulation of the receiver signal.
17. A circuit, comprising:
a digital to analog converter configured to convert an analog communication signal to a digital communication signal;
a digital buffer coupled to the digital to analog converter, the digital buffer configured to:
store pre-distortion information about the digital communication signal; and
apply the pre-distortion information to the digital communication signal to generate a pre-distorted digital communication signal, the pre-distortion information being determined from an impedance element configured to generate a notch frequency signal at a transmitter leakage frequency; and
a power amplifier driver configured to drive to drive the pre-distorted digital communication signal.
18. The circuit of claim 17 , where the power amplifier comprises a Class B power amplifier.
19. The circuit of claim 17 , where the digital buffer is configured to apply the notch frequency signal to a transmitter leakage signal to attenuate the transmitter leakage signal prior to demodulation of a desired receiver signal by a receiver.
20. The circuit of claim 17 , where the impedance element includes an operational amplifier.