Blocker-Tolerant Wideband Noise-Canceling Receivers
Because of associated disadvantages of narrow-band off-chip radio-frequency (RF) filtering, a mixer-first receiver front-end designed to tolerate blockers with minimal gain compression and noise factor degradation is disclosed. The mixer-first receiver front-end includes two separate down-conversion paths that help to minimize added noise and voltage gain prior to baseband filtering, which are critical factors in eliminating narrow-band off-chip RF filtering.
1 . A receiver front-end for receiving a radio-frequency (RF) signal represented by an RF voltage signal and an RF current signal from an antenna, the receiver front-end comprising:
a main down-conversion path comprising: a first passive mixer configured to mix the RF current signal with a local-oscillator (LO) signal to provide a first down-converted signal, and a first transimpedance amplifier configured to apply a first gain to the first down-converted signal to provide a first output signal; and
an auxiliary down-conversion path comprising: a transconductance cell configured to convert the RF voltage signal into a corresponding current signal, a second passive mixer configured to mix the corresponding current signal with the LO signal to provide a second down-converted signal, and a second transimpedance amplifier configured to apply a second gain to the second down-converted signal to provide a second output signal,
wherein the RF voltage signal is a voltage between a source impedance of the antenna and the main down-conversion path, and the RF current signal is a current flowing through the main down-conversion path.
2 . The receiver front-end of claim 1 , wherein the first gain is determined based on the second gain and the source impedance of the antenna.
3 . The receiver front-end of claim 1 , wherein the first gain is proportional to the product of the second gain and the source impedance of the antenna.
4 . The receiver front-end of claim 1 , wherein the transconductance cell is an inverter.
5 . The receiver front-end of claim 1 , further comprising:
a baseband processing block configured to process the first output signal and the second output signal as two ends of a differential signal.
6 . The receiver front-end of claim 1 , further comprising:
a baseband processing block configured to sense the first output signal and the second output signal differentially such that noise from an impedance of the main down-conversion path is canceled and the RF signal is reinforced.
7 . The receiver front-end of claim 6 , wherein the baseband processing block is further configured to low-pass filter and digitize the first output signal and the second output signal.
8 . The receiver front-end of claim 1 , wherein the first passive mixer is included within a first harmonic rejection mixer and the second passive mixer is included within a second harmonic rejection mixer.
9 . The receiver front-end of claim 1 , further comprising a low-pass filter configured to filter the first output signal.
10 . The receiver front-end of claim 9 , wherein the low-pass filter is a switched capacitor filter.
11 . A receiver front-end for receiving a radio-frequency (RF) signal represented by an RF voltage signal and an RF current signal from an antenna, the RF front-end comprising:
a first passive mixer configured to down-convert the RF current signal to provide a first down-converted signal;
a first transimpedance amplifier configured to receive the first down-converted signal from the first passive mixer at a first summing node at virtual ground and apply a first gain to the first down-converted signal to provide a first output signal;
a second passive mixer configured to down-convert a current signal corresponding to the RF voltage signal to provide a second down-converted signal; and
a second transimpedance amplifier configured to receive the second down-converted signal from the second passive mixer at a second summing node at virtual ground and apply a second gain to the second down-converted signal to provide a second output signal,
wherein the RF voltage signal is a voltage between a source impedance of the antenna and the first passive mixer, and the RF current signal is a current flowing through the first passive mixer.
12 . The receiver front-end of claim 11 , wherein the first gain is determined based on the second gain and the source impedance of the antenna.
13 . The receiver front-end of claim 11 , wherein the first gain is proportional to the product of the second gain and the source impedance of the antenna.
14 . The receiver front-end of claim 11 , further comprising:
a baseband processing block configured to process the first output signal and the second output signal as two ends of a differential signal.
15 . The receiver front-end of claim 11 , further comprising:
a baseband processing, block configured to sense the first output signal and the second output signal differentially.
16 . The receiver front-end of claim 15 , wherein the baseband processing block is further configured to low-pass filter and digitize the first output signal and the second output signal.
17 . The receiver front-end of claim 11 . wherein the first passive mixer is included within a first harmonic rejection mixer and the second passive mixer is included within a second harmonic rejection mixer.
18 . The receiver front-end of claim 11 , further comprising a low-pass filter configured to filter the first output signal.
19 . The receiver front-end of claim 18 , wherein the low-pass filter is a switched capacitor filter.
20 . A receiver front-end for receiving a radio-frequency (RF) signal represented by an RF voltage signal and an RF current signal from an antenna, the RF front-end comprising:
a main down-conversion path configured to down-convert the RF current signal to provide a first down-converted signal using a first passive mixer and apply a first gain to the first down-converted signal; and
an auxiliary down-conversion path configured to down-convert a current signal corresponding to the RF voltage signal using a second passive mixer to provide a second down-converted signal and apply a second gain to the second down-converted signal,
wherein the first gain is determined based on the second gain and a source impedance associated with the antenna.