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US 8,103,226 B2Granted
Power amplifier saturation detection
AssigneeSkyworks Solutions, Inc.
InventorsPaul R. Andrys, Michael L. Gerard, Terry J. Shie
Life of this patent
Estimating the term…
Abstract
In a portable radio transceiver, a power amplifier system includes a saturation detector that detects power amplifier saturation in response to duty cycle of the amplifier transistor collector voltage waveform. The saturation detection output signal can be used by a power control circuit to back off or reduce the amplification level of the power amplifier to avoid power amplifier control loop saturation.
Claims13
A power amplifier circuit for a radio frequency (RF) transmitter, the power amplifier circuit comprising:
- a power amplifier having at least one output transistor having an output transistor terminal coupled to a supply voltage, the power amplifier including a high-band output transistor and a low-band output transistor selectably activatable in response to a band-select signal, the high-band output transistor having a high-band output transistor terminal coupled to a supply voltage, the low-band output transistor having a low-band output transistor terminal coupled to a supply voltage;
- a duty cycle detector having an input coupled to the output transistor terminal, the duty cycle detector including:
- a limiter section coupled to the output transistor terminal, the limiter section blocking positive voltage excursions and passing negative voltage excursions, the limiter section including a first limiter and a second limiter, the first limiter being coupled to the high-band output transistor terminal, the first limiter blocking positive voltage excursions and passing negative voltage excursions, the second limiter being coupled to the low-band output transistor terminal, the second limiter blocking positive voltage excursions and passing negative voltage excursions;
- and an averaging filter section coupled to an output of the limiter section, the averaging filter section including a first averaging filter coupled to an output of the first limiter and a second averaging filter coupled to an output of the second limiter;
- and
- a comparator section having first and second comparator inputs and producing a saturation detection output signal, one of the first and second comparator inputs being coupled to an output of the duty cycle detector, and the other of the first and second comparator inputs being coupled to a reference voltage circuit, the comparator section including a switching section responsive to the band-select signal, the switching section coupling the first comparator input to an output of the first averaging filter and coupling the second comparator input to a reference voltage circuit when the band-select signal indicates high-band operation, the switching section further coupling the first comparator input to an output of the second averaging filter and coupling the second comparator input to a reference voltage circuit when the band-select signal indicates low-band operation.
3 more elements
A method for detecting power amplifier saturation in a radio frequency (RF) transmitter, the method comprising:
- amplifying an RF signal using an output transistor, the output transistor having an output transistor terminal coupled to a supply voltage, said amplifying including amplifying a high-hand RF signal using a high-band output transistor of a power amplifier and amplifying a low-band RF signal using a low-band output transistor, the high-band output transistor having a high-band output transistor terminal coupled to a supply voltage, the low-band output transistor having a low-band output transistor terminal coupled to a supply voltage;
- detecting a duty cycle of the amplified RF signal, said detecting including:
- limiting positive voltage excursions of the amplified RF signal while passing negative voltage excursions of the amplified RF signal to produce a limited signal, said limiting including limiting positive voltage excursions of the amplified high-band RF signal while passing negative voltage excursions of the amplified high-band RF signal to produce a first limited signal and limiting positive voltage excursions of the amplified low-band RF signal while passing negative voltage excursions of the amplified low-band RF signal to produce a second limited signal;
- and averaging the limited signal to produce an averaged signal, said averaging including averaging the first limited signal to produce a first averaged signal and averaging the second limited signal to produce a second averaged signal;
- providing a signal representing the duty cycle to a first input of a comparator section and a reference voltage to a second input of the comparator section, said providing including coupling the first averaged signal to the first input of a comparator section and coupling a reference voltage to the second input of the comparator section when a band-select signal indicates high-band operation, and coupling the second averaged signal to the second input of the comparator section and coupling a reference voltage to the first input of the comparator section when the band-select signal indicates low-band operation;
- and
- producing a saturation detection output signal in response to a comparison of the signal representing the duty cycle with the reference voltage.
4 more elements
A mobile wireless telecommunication device, comprising:
- a user interface;
- an antenna;
- a baseband subsystem coupled to the user interface;
- and
- a radio frequency (RF) subsystem coupled to the baseband subsystem and the antenna, the RF subsystem including a transmitter portion and a receiver portion, the transmitter portion including a modulator, an up converter and a power amplifier system, the power amplifier system including:
- a power amplifier having a high-band output transistor and a low-band output transistor, the high-band output transistor having a high-band output transistor terminal coupled to a supply voltage, the low-band output transistor having a low-band output transistor terminal coupled to a supply voltage;
- a first limiter section coupled to the high-band output transistor terminal, the first limiter section blocking positive voltage excursions and limiting negative voltage excursions;
- a first averaging filter section coupled to an output of the first limiter section;
- a second limiter section coupled to the low-band output transistor terminal, the second limiter section blocking positive voltage excursions and passing negative voltage excursions;
- a second averaging filter section coupled to an output of the second limiter section;
- and a comparator section, the comparator section having first and second comparator inputs and producing a saturation detection output signal, the comparator circuit further including a switching section responsive to a band-select signal, the switching section coupling the first comparator input to an output of the first averaging filter and coupling the second comparator input to a reference voltage circuit when the band-select signal indicates high-band operation, the switching section further coupling the first comparator input to an output of the second averaging filter and coupling the second comparator input to a reference voltage circuit when the band-select signal indicates low-band operation.
8 more elements
Dependencies are inferred from the claim text.