Polyphase phase shifter
In described examples, a quadrature phase shifter includes digitally programmable phase shifter networks for generating leading and lagging output signals in quadrature. The phase shifter networks include passive components for reactively inducing phase shifts, which need not consume active power. Output currents from the transistors coupled to the phase shifter networks are substantially in quadrature and can be made further accurate by adjusted by a weight function implemented using current steering elements. Example low-loss quadrature phase shifters described herein can be functionally integrated to provide low-power, low-noise up/down mixers, vector modulators and transceiver front-ends for millimeter wavelength (mmwave) communication systems.
1. A circuit, comprising:
an input transistor for modulating a first current in response to a first input frequency;
a first phase generator including the input transistor as a first-phase-generator first transistor, a first-phase-generator second transistor for phase shifting a first portion of the modulated first current in response to a first reactive network coupled to a control terminal of the first-phase-generator second transistor and in response to a voltage developed in response to the modulated first current, and a first-phase-generator third transistor for modulating the phase-shifted first portion of the modulated first current in response to a second input frequency to generate a first output signal; and
a second phase generator including the input transistor as a second-phase-generator first transistor, a second-phase-generator second transistor for phase shifting a second portion of the modulated first current in response to a second reactive network coupled to a control terminal of the second-phase-generator second transistor and in response to the voltage developed in response to the modulated first current, and a second-phase-generator third transistor for modulating the phase-shifted second portion of the modulated first current in response to the second input frequency to generate a second output signal;
wherein the first reactive network is configured to generate a first phase shift for phase shifting the first portion of the modulated first current and the second reactive network is configured to generate a second phase shift for phase shifting the second portion of the modulated first current, wherein the first and second phase shifts are different from each other, and wherein the input transistor is common to both the first and second phase generators.
2. The circuit of claim 1 , wherein the voltage developed in response to the modulated first current is developed at an emitter of the first-phase-generator second transistor.
3. The circuit of claim 2 , wherein the first reactive network generates AC signal components in response to an emitter-base current flowing across a junction of the first-phase-generator second transistor, wherein the first-reactive-network AC signal components are for phase shifting the first portion of the modulated first current.
4. The circuit of claim 3 , wherein the first-phase-generator third transistor is for controlling the emitter-base current flowing across the junction of the first-phase-generator second transistor.
5. The circuit of claim 4 , wherein the first-phase-generator third transistor includes an array of selectively paralleled transistors for selectively controlling an emitter-base current flowing across the emitter-base junction of the first-phase-generator second transistor.
6. The circuit of claim 5 , wherein the voltage developed in response to the modulated first current is also developed at an emitter of the second-phase-generator second transistor, wherein the second reactive network generates AC signal components in response to an emitter-base current flowing across an emitter-base junction of the second-phase-generator second transistor, wherein the second-reactive-network AC signal components are for phase shifting the second portion of the modulated first current, and wherein the second-phase-generator third transistor is for controlling the emitter-base current flowing across the junction of the second-phase-generator second transistor.
7. The circuit of claim 1 , wherein the first output signal leads the second output signal by a phase difference of approximately 90 degrees.
8. The circuit of claim 1 , comprising a first-phase-generator fourth transistor for modulating the phase-shifted first-transistor modulated current in response to an inverse phase of the second input frequency to generate an inverse phase of the first output signal, and comprising a second-phase-generator fourth transistor for modulating the phase-shifted first-transistor modulated current in response to the inverse phase of the second input frequency to generate an inverse phase of the second output signal.
9. A system, comprising:
an input transistor for modulating a first current in response to a first input frequency;
a first phase generator including the input transistor as a first-phase-generator first transistor and a first-phase-generator second transistor for phase shifting a first portion of the modulated first current in response to a first reactive network coupled to a control terminal of the first-phase-generator second transistor and in response to a voltage developed in response to the modulated first current;
a second phase generator including the input transistor as a second-phase-generator first transistor and a second-phase-generator second transistor for phase shifting a second portion of the modulated first current in response to a second reactive network coupled to a control terminal of the second-phase-generator second transistor and in response to the voltage developed in response to the modulated first current, wherein the first reactive network is configured to generate a first phase shift for phase shifting the first portion of the modulated first current and the second reactive network is configured to generate a second phase shift for phase shifting the second portion of the modulated first current, wherein the first and second phase shifts are different from each other, and wherein the input transistor is common to both the first and second phase generators; and
an amplifier for coupling to an antenna a signal generated in response to the phase-shifted first portion of the modulated first current and the phase-shifted second portion of the modulated first current.
10. The system of claim 9 , wherein the first and second phase generator and the amplifier collectively are multiply instantiated as instances of a beamforming transmitter array.
11. The circuit of claim 1 , wherein:
the first phase generator includes a first inductor network arranged between the first-phase-generator second transistor and the first-phase-generator third transistor; and
the second phase generator includes a second inductor network arranged between the second-phase-generator second transistor and the second-phase-generator third transistor.