Efficient modulation of RF signals
View Patent ↗Coherent modulator architectures of wireless communication devices are used for the processing of modulated RF signals. The circuitry comprises a DC/DC converter ( 204 ) which serves as an amplitude modulator, different amplification stages ( 204, 206, 212, 214 ), a bypass path ( 215 ) to selectively bypass at least one ( 214 ) of a cascade of class C, D, E, or F power amplifiers ( 212, 214 ), and an automatic power control (APC) loop ( 220 ) that guarantees power stability over time and temperature variations. To increase the efficiency of the amplification procedures needed for an amplitude modulation, the slow (narrowband) high-level components ( 222 ) and the fast (wideband) low-level components ( 224 ) of the signal representing the magnitude (I x Lp (t) 1) of an I/Q modulation state (x Lp (t)) are amplified in separate stages ( 204, 206 ) and are then combined by supplying the low-level components ( 224 ) to a power amplifier ( 206 ) whose gain is controlled depending on the amplified high-level components ( 222 ). At least one ( 214 ) of said cascade of power amplifiers ( 212, 214 ) can selectively be bypassed by a bypass circuitry ( 215 ), which is used for the sake of efficiency optimization. In the bypass mode, the DC power supply (V bat ) of the bypassed power amplifier ( 214 ) can selectively be switched off by means of a switch (SZ). It is used when the needed RF signal power is low and the driver PA ( 212 ) is able to produce enough gain.
1. A method for I/Q modulation, the method comprising:
converting an in-phase (I) and a quadrature (Q) component of a complex-valued analog baseband input signal into signals representing a magnitude and a phase of I/Q modulation states of the complex-valued analog baseband input signal, respectively; and
combining the signals representing the magnitude and phase to generate a modulated RF output transmission signal,
wherein slow high-level components and fast low-level components of the signal representing the magnitude are amplified in separate amplifier stages, and wherein the slow high-level components and the fast low-level components of the signal representing the magnitude are combined to provide a combined envelope representing signal by supplying the low-level components to a power amplifier whose gain is controlled based on the amplified high-level components.
2. A method according to claim 1 , wherein the slow high-level components of the signal representing the magnitude are amplified using a DC/DC converter.
3. A method according to claim 1 , wherein the combined envelope representing signal controls a gain of at least a second power amplifier supplied with an RE signal modulated with the signal representing the phase.
4. A method according to claim 1 , wherein the combined envelope representing signal controls a gain of at least one of a plurality of serially connected power amplifiers, and wherein a first one of the plurality of power amplifiers is supplied with an RF signal based on the signal representing the phase.
5. A method according to claim 4 , wherein at least one of the plurality of power amplifiers is configured to be selectively bypassed.
6. A method according to claim 5 , wherein a power supply of a bypassed one of the plurality of power amplifiers is configured to be selectively switched off.
7. A method according to claim 4 , wherein the combined envelope representing signal is configured to be selectively dampened.
8. A method according to claim 1 , wherein the high-level components of the signal representing the magnitude are represented by a ramp signal supplied from a baseband block to an amplifier.
9. An I/Q modulator configured to carry out a method according to claim 1 .
10. An I/Q modulator, comprising:
a conversion unit configured to convert an in-phase (I) and a quadrature (Q) component of a complex-valued analog baseband input signal into signals representing a magnitude and a phase of I/Q modulation states of the complex-valued analog baseband input signal, respectively;
a combination unit configured to combine the signals representing the magnitude and phase to generate a modulated RF output transmission signal;
a first amplifier stage configured to amplify slow high-level components of the signal representing the magnitude;
a second amplifier stage configured to amplify fast low-level components of the signal representing the magnitude; and
a power amplifier supplied with the fast low-level components and having a gain controlled based on the amplified slow high-level components,
wherein the power amplifier is configured to combine the slow high-level components and fast low-level components of the signal representing the magnitude to provide a combined envelope representing signal.
11. A modulator according to claim 10 , further comprising:
a DC/DC converter configured to amplify the slow high-level components of the signal representing the magnitude.
12. A modulator according to claim 10 , further comprising:
a second power amplifier supplied with an RF signal modulated with the signal representing the phase and having a gain controlled by the combined envelope representing signal.
13. A modulator according to claim 10 , further comprising:
a plurality of serially connected power amplifiers having respective gains controlled by the combined envelope representing signal,
wherein a first one of the plurality of power amplifiers is supplied with an RF signal based on the signal representing the phase.
14. A modulator according to claim 13 , further comprising:
a switch configured to selectively bypass at least one of the plurality of power amplifiers.
15. A modulator according to claim 14 , further comprising:
a second switch configured to selectively switch off a power supply of a bypassed one of the plurality of power amplifiers.
16. A modulator according to claim 13 , further comprising:
a switch configured to selectively dampen the combined envelope representing signal.
17. A wireless transmitter, comprising:
an I/Q modulator according to claim 10 .
18. A mobile telecommunications device, comprising:
an I/O modulator according to claim 10 .