Systems and methods for split-frequency amplification
A system for split-frequency amplification, preferably including: one or more primary-band amplification stages, one or more secondary-band amplification stages, one or more band-splitting filters, and/or one or more signal couplers. An analog canceller including one or more split-frequency amplifiers. A mixer including one or more split-frequency amplifiers. A voltage-controlled oscillator including one or more split-frequency amplifiers. A method for split-frequency amplification, preferably including: receiving an input signal, separating the input signal into signal portions, and/or amplifying the signal portions, and optionally including combining the amplified signal portions and/or providing one or more output signals.
1. A system for split-frequency amplification, comprising:
a plurality of circuit branches, the plurality comprising a first branch and a second branch;
an input coupler that:
receives an input signal comprising a first band and a second band; and
couples a respective portion of the input signal onto each circuit branch of the plurality; and
an output coupler that:
receives a plurality of amplified signals from the plurality of circuit branches; and
combines the plurality of amplified signals into an output signal;
wherein:
the first band comprises a first frequency and does not comprise a second frequency lower than the first frequency;
the second band comprises the second frequency and does not comprise the first frequency;
the first branch comprises:
a first high-pass filter (HPF) defining a first cutoff frequency between the first and second frequencies; and
a first amplifier stage coupled to the first HPF, wherein the first amplifier stage receives a first portion of the input signal and amplifies the first portion into a first amplified signal of the plurality of amplified signals;
the second branch comprises a second amplifier stage that receives a second portion of the input signal and amplifies the second portion into a second amplified signal of the plurality of amplified signals, wherein the second portion exhibits a different spectral characteristic than the first portion;
the second branch is electrically connected in parallel with the first branch between the input coupler and the output coupler;
the first amplifier stage exhibits a first high-frequency noise power at the first frequency and exhibits a first low-frequency noise power at the second frequency; and
the second amplifier stage exhibits a second high-frequency noise power, greater than the first high-frequency noise power, at the first frequency and exhibits a second low-frequency noise power, lesser than the first low-frequency noise power, at the second frequency.
2. The system of claim 1 , wherein:
the first amplifier stage exhibits a first high-frequency gain at the first frequency;
the second amplifier stage exhibits a second low-frequency gain at the second frequency; and
the second amplifier stage exhibits a second high-frequency gain at the first frequency, wherein the second high-frequency gain is substantially less than the first high-frequency gain and is substantially less than the second low-frequency gain.
3. The system of claim 2 , wherein the second high-frequency gain is less than the second low-frequency gain by more than 10 dB.
4. The system of claim 1 , wherein the second branch further comprises a first low-pass filter (LPF) coupled to the second amplifier stage, the first LPF defining a second cutoff frequency between the first and second frequencies.
5. The system of claim 4 , wherein the second cutoff frequency is greater than the first cutoff frequency.
6. The system of claim 1 , wherein:
the first and second amplifier stages cooperatively define a crossover frequency between the first and second frequencies, wherein:
for all frequencies below the crossover frequency, noise power of the first amplifier stage is greater than noise power of the second amplifier stage; and
between the crossover frequency and a maximum frequency of the first band, noise power of the first amplifier stage is less than noise power of the second amplifier stage; and
a difference between the crossover frequency and the first cutoff frequency is less than the first cutoff frequency.
7. The system of claim 6 , wherein the difference between the crossover frequency and the first cutoff frequency is less than 30% of the first cutoff frequency.
8. The system of claim 1 , further comprising an output stage that:
receives the output signal from the output coupler; and
amplifies the output signal.
9. The system of claim 8 , wherein the output stage comprises:
a third branch comprising:
a second HPF defining a second cutoff frequency between the first and second frequencies; and
a third amplifier stage coupled to the second HPF, wherein the third amplifier stage receives and amplifies a first portion of the output signal;
a fourth branch comprising a fourth amplifier stage that receives and amplifies a second portion of the output signal, wherein the second portion of the output signal exhibits a different spectral characteristic than the first portion of the output signal; and
a second output coupler that receives and combines the amplified first and second portions of the output signal.
10. The system of claim 9 , wherein the fourth branch further comprises a second LPF defining a third cutoff frequency between the first and second frequencies.
11. The system of claim 9 , wherein the third amplifier stage comprises an NMOS-based amplifier stage and the fourth amplifier stage comprises a CMOS-based amplifier stage.
12. The system of claim 1 , wherein the plurality of circuit branches further comprises a third branch comprising:
a second HPF defining a second cutoff frequency between the first and second frequencies; and
a third amplifier stage coupled to the second HPF, wherein the third amplifier stage receives a third portion of the input signal and amplifies the third portion into a third amplified signal of the plurality of amplified signals.
13. The system of claim 12 , wherein:
the second amplifier stage comprises:
an input sub-stage selected from the group consisting of: a BJT-based amplifier sub-stage and a JFET-based amplifier sub-stage; and
a current mirror sub-stage electrically connected in series between the input sub-stage and the output coupler; and
the third amplifier stage is electrically connected in parallel with the input sub-stage between the input coupler and the current mirror sub-stage.
14. The system of claim 13 , wherein the first amplifier stage comprises:
a telescopic amplifier sub-stage; and
a second current mirror sub-stage electrically connected in series between the telescopic amplifier sub-stage and the output coupler.
15. The system of claim 12 , wherein:
the telescopic amplifier sub-stage comprises a CMOS-based amplifier sub-stage; and
the input sub-stage of the second amplifier stage is a BJT-based amplifier sub-stage.
16. The system of claim 1 , wherein the first amplifier stage comprises a MOSFET-based amplifier sub-stage.
17. The system of claim 16 , wherein the second amplifier stage comprises a BJT-based amplifier sub-stage.
18. The system of claim 16 , wherein the second amplifier stage comprises a JFET-based amplifier sub-stage.
19. The system of claim 1 , further comprising a mixer circuit electrically coupled to the input coupler, wherein the mixer circuit:
receives an RF input;
generates a lower-frequency output based on the RF input; and
provides the lower-frequency output to the input coupler.
20. The system of claim 1 , further comprising a voltage-controlled oscillator, wherein the voltage-controlled oscillator comprises a negative feedback amplifier comprising the input coupler, the plurality of circuit branches, and the output coupler.