Amplifiers – Combined with automatic amplifier disabling switch means
Reexamination Certificate
1999-02-10
2001-03-27
Pascal, Robert (Department: 2817)
Amplifiers
Combined with automatic amplifier disabling switch means
C330S151000
Reexamination Certificate
active
06208202
ABSTRACT:
BACKGROUND INFORMATION
I. Field of the Invention
The present invention relates generally to power gain control for a power amplifier circuit and particularly to a power application circuit having greater power conservation in wireless communication device, such as a CDMA wireless phone.
2. Description of the Related Art
In many electronic environments, such as most hand-held communication systems including code-division-multiple-access (CDMA) or any form of time-division-multiple access (TDMA) technology, RF power output from a mobile unit varies in large dynamic ranges. In a CDMA radiotelephone system, multiple signals are transmitted simultaneously at the same frequency. The signals are spread with different digital codes, thus allowing detection of the desired signal while the unintended signals appear as noise or interference to the receiver. Spread spectrum systems can tolerate some interference, and the interference added by each new mobile station increases the overall interference in each cell site. Each mobile station introduces a unique level of interference, which depends on its received power level at the cell site.
The CDMA system uses power control to minimize mutual interference. A precise power control is critical to avoid excessive transmitter signal power that is responsible for contributing to the overall interference of the system. Power of the individual mobile stations varies with the distance between the mobile station and the base station and the number of other subscriber mobile stations in that base station or sector.
In a typical hand-held wireless unit, the power amplifier is biased class AB to reduce power consumption during periods of low transmit power, but power continues to be consumed. Typically an isolator is used to isolate the power amplifier from the effects of load impedance in subsequent stages. One method to avoid continuous battery draw is to employ a means to bypass the amplifier with switches, and then remove DC power from the amplifier. Such a power amplifier circuit has a power amplifier and an isolator. An RF-input is connected to a pole of a first switch. When the amplifier is on, the switch connects the RF-input to an input of the power amplifier. The RF-signal is amplified and output to the isolator, and then transmitted through the second switch to the RF-output of the power amplifier circuit. To bypass the power amplifier, the first switch connects the RF-input to the bypass path and the second switch transmits the signal to the RF-output. The switching employed introduces loss as the signal is processed. The drawback of this design is that the amplifier must overcome the added switching loss during times that higher transmit power is required. This can tend to cancel the benefits of bypassing.
SUMMARY OF THE INVENTION
What is needed in the art is a cellular phone or mobile station having power amplifier circuit which conserves power by turning off and bypassing the power amplifier when power demand is low and by using a driver amplifier (“DA”) as the power output amplifier.
An object of the present invention is to increase the efficiency of power amplifier usage by providing a circuit to bypass the power amplifier or power amplifiers when power demand is low.
Another object of the present invention is to reduce the effects of power loss after a signal is amplified by a power amplifier.
Another object of the present invention is to provide an improved power amplifier which requires less parts and is less complex to build.
Yet another object of the present invention is to provide an improved power amplifier which is less expensive to build.
These objects and others may be realized by the invention disclosed herein. In a mobile station having a power amplifier circuit, a switch operates to direct the received signal from a driver amplifier to either an amplifier path containing a band-pass filter and a power amplifier, or a bypass path. The bypass path bypasses the power amplifier when the power amplifier capability is not required. During the periods of low power operation, the amplifier is turned off. When the signal is passed through the bypass path it enters the isolated port of a hybrid circuit. The signal is transmitted to the output of the power amplifier. The power amplifier appears as a large impedance which is highly reflective because it is turned off. The reflected signal is then routed to the output port or front end of the circuit. With this configuration, an output switch becomes unnecessary and the power loss after the signal is amplified is reduced.
A first band-pass filter is placed in the amplification path such that filtering is also bypassed when the power amplifier is bypassed. When greater power amplification of the signal is needed, the signal flow is directed through a transmitter chain containing the first band-pass filter and a power amplifier (“PA”). The first filter in the transmitter chain cleans up noise added by the DA. The PA amplifies the signal which then is transmitted through an isolator and a second filter at the output of the circuit which cleans up noise added by the PA. A benefit of bypassing the PA is that it no longer adds noise to the signal. The second filter at the output of the circuit still filters the added effects of the PA, and when the signal routes through the bypass path, the second filter reduces noise added by the driver amplifier. Therefore, the first filter becomes unnecessary when the signal is passed through the bypass path.
This power amplification circuit provides reduced loss at the end of the amplifier, whereby greater power using less current at the output may be achieved. The configuration also reduces the loss in the bypass path when changing modes from amplification to bypass. The driver amplifier therefore becomes the output amplifier.
In another aspect of the present invention, bypassing the power amplifier enables the driver amplifier to be driven harder because it is the dominating source of distortion in the chain. The driver amplifier may be driven to a greater degree in the non-linear region than could be accomplished when using the power amplifier. By expanding the region over which the driver amplifier is driven, the cellular phone may be operated using the driver amplifier for a longer period of time, thus conserving battery power by keeping the power amplifier off for longer periods of time.
REFERENCES:
patent: 5423074 (1995-06-01), Dent
patent: 5661434 (1997-08-01), Brozovich et al.
patent: 5673003 (1997-09-01), Zocher
patent: 5793253 (1998-08-01), Kumar et al.
patent: 5872481 (1999-02-01), Sevic et al.
patent: 5909643 (1999-06-01), Aihara
patent: 5973557 (1999-10-01), Miyaji et al.
Camarillo Richard J.
Hunzeker Darin
Kaufman Ralph E.
Brown Charles D.
Nguyen Khanh Van
Pascal Robert
Qualcomm Inc
Wadsworth Philip
LandOfFree
High efficiency switched gain power amplifier does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High efficiency switched gain power amplifier, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High efficiency switched gain power amplifier will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2446437