High frequency mixer with tunable dynamic range
View Patent ↗A high frequency mixer with a tunable dynamic range is disclosed. One embodiment provides a mixer apparatus including multiple first transistors at an input branch that receive a differential radio frequency (RF) signal, and multiple second transistors at a second branch that receive a differential local oscillator (LO) signal. The second transistors generate an intermediate frequency (IF) differential output signal. The bias current that flows at the input branch and the output branch can be independently adjusted to allow the conversion gain, linearity, or the output noise of the mixer to be controlled.
1. A mixer apparatus, comprising:
a first plurality of transistors, including a pair of n-type metal oxide semiconductor (NMOS) transistors, configured to receive a radio frequency (RF) signal and to provide a mixer input signal;
a second plurality of transistors configured to frequency translate the mixer input signal with a local oscillator (LO) signal to provide an intermediate frequency (IF) signal; and
a comparator configured to compare a common mode voltage of the IF signal to a reference voltage to provide a sensing signal,
wherein the first plurality of transistors further includes a pair of p-type metal oxide semiconductor (PMOS) transistors configured to provide a mixer input current based on the sensing signal to drive the common mode voltage to substantially equal the reference voltage.
2. The mixer apparatus of claim 1 , further comprising:
a second pair of NMOS transistors coupled to the pair of NMOS transistors, the second pair of NMOS transistors being configured to receive a second RF signal, wherein the pair of NMOS transistors and the second pair of NMOS transistors are configured to provide either the RF signal or the second RF signal as the mixer input signal.
3. The mixer apparatus of claim 1 , wherein the first plurality of transistors includes a first current source configured to provide the mixer input current, and
wherein the second plurality of transistors includes a second current source, the second current source being configured to provide a mixer output current, and wherein the second plurality of transistors is further configured to adjust the common mode voltage based on variations in the mixer output current.
4. The mixer apparatus of claim 1 , further comprising:
a first plurality of switches coupled to a first plurality of corresponding current sources;
a second plurality of switches coupled to a second plurality of corresponding current sources; and
first and second diode-connected transistors, each of the first and second diode-connected transistors being coupled to each switch from among the plurality of switches,
wherein the first plurality of switches is configured to selectively couple each current source from among the first plurality of current sources to the first diode-connected transistor,
wherein the second plurality of switches is configured to selectively couple each current source from among the second plurality of current sources to the second diode-connected transistor, and
wherein the first and second diode-connected transistors are further configured to provide first and second bias voltages, respectively.
5. The mixer apparatus of claim 4 , wherein the first plurality of transistors is further configured to adjust a bias current level of the RF signal using the first bias voltage, and
wherein the second plurality of transistors is further configured to adjust the common mode voltage using the second bias voltage.
6. The mixer apparatus of claim 4 , wherein the first plurality of current sources and the second plurality of current sources comprise:
weighted current sources.
7. The mixer apparatus of claim 1 , further comprising:
a first bias circuit configured to provide a first bias voltage to said first plurality of transistors, and a second bias circuit configured to provide a second bias voltage to said second plurality of transistors, said first and second bias voltages determined to independently adjust respective first and second mixer characteristics that are different from each other.
8. The mixer apparatus of claim 7 , wherein the first bias voltage is adjusted to increase a first bias current in the first plurality of transistors to effect the first mixer characteristic, and the second bias voltage is adjusted to decrease a second bias current in the second plurality of transistors to effect the second mixer characteristic, and wherein the first mixer characteristic is gain and the second mixer characteristic is noise figure.
9. A mixer apparatus, comprising:
a first plurality of transistors configured to receive a radio frequency (RF) signal and a first bias voltage to provide a mixer input signal having an RF bias current;
a second plurality of transistors configured to provide a mixer input current; and
a third plurality of transistors configured to frequency translate the mixer input signal with a local oscillator (LO) signal to deliver an intermediate frequency (IF) signal to a load having a common mode voltage,
wherein the load is configured to adjust the common mode voltage based on a second bias voltage, the load including a pair of transistors having their gate electrodes coupled to one another and to a biasing device, the biasing device being configured to supply the second bias voltage, and the pair of transistors being configured to adjust the common mode voltage in response to the second bias voltage,
wherein the first plurality of transistors is further configured to adjust the RF bias current based on the first bias voltage, and
wherein the second plurality of transistors is further configured to adjust the mixer input current based on the common mode voltage.
10. The mixer apparatus of claim 9 , further comprising:
a comparator configured to compare the common mode voltage to a reference voltage to provide a sensing signal, and
wherein the second plurality of transistors is further configured to adjust the mixer input current based on the sensing signal.
11. The mixer apparatus of claim 10 , wherein the second plurality of transistors is further configured to provide the mixer input current to drive the common mode voltage to substantially equal the reference voltage.
12. The mixer apparatus of claim 9 , wherein the biasing device comprises:
a plurality of switches coupled to a plurality of corresponding current sources; and
a diode-connected transistor coupled to each switch from among the plurality of switches,
wherein the plurality of switches is configured to selectively couple each current source from among the plurality of current sources to the diode-connected transistor, and
wherein the diode-connected transistor is further configured to provide the second bias voltage.
13. The mixer apparatus of claim 12 , wherein the biasing device is from among a plurality of biasing devices, and wherein a second biasing device from among the plurality of biasing devices is further configured to provide the first bias voltage.
14. The mixer apparatus of claim 9 , further comprising:
a fourth plurality of transistors coupled to the first plurality of transistors, the fourth plurality of transistors being configured to receive a second RF signal, wherein the first plurality of transistors and the fourth plurality of transistors are configured to provide either the RF signal or the second RF signal as the mixer input signal.
15. A mixer apparatus, comprising:
a plurality of n-type metal oxide semiconductor (NMOS) transistors configured to receive a radio frequency (RF) signal and to provide a mixer input signal;
a plurality of p-type metal oxide semiconductor (PMOS) transistors coupled to the plurality of NMOS transistors, the plurality of PMOS transistors being configured to frequency translate the mixer input signal with a local oscillator (LO) signal to provide an intermediate frequency (IF) signal having a common mode voltage;
a first current source coupled to the plurality of NMOS transistors, the first current source being configured to provide a mixer input current based on the common mode voltage; and
a second current source coupled to the plurality of PMOS transistors, the second current source being configured to provide a mixer output current and to set the common mode voltage to substantially equal a reference voltage by adjusting the mixer output current.
16. The mixer apparatus of claim 15 , further comprising:
a comparator configured to compare the common mode voltage to the reference voltage to provide a sensing signal, and
wherein the first current source is further configured to adjust the mixer input current based on the sensing signal.
17. The mixer apparatus of claim 15 , wherein the plurality of NMOS transistors is coupled to a first biasing device, the first biasing device being configured to supply a first bias voltage and to bias the RF signal with the first bias voltage to provide the mixer input signal, and wherein the second current source comprises:
a pair of transistors having their gate electrodes coupled to one another and to a second biasing device, the second biasing device being configured to supply a second bias voltage, and to adjust the common mode voltage in response to variations in the second bias voltage.
18. The mixer apparatus of claim 17 , wherein the second current source is further configured to adjust the mixer output current based on the second bias voltage.
19. The mixer apparatus of claim 17 , wherein the first and second biasing devices comprise:
a plurality of switches coupled to a plurality of corresponding third current sources; and
a diode-connected transistor coupled to each switch from among the plurality of switches,
wherein the plurality of switches is configured to selectively couple each third current source from among the plurality of third current sources to the diode-connected transistor, and
wherein the diode-connected transistor is configured to provide the first bias voltage and the second bias voltage.
20. The mixer apparatus of claim 19 , wherein the plurality of corresponding third current sources comprise:
weighted current sources.