Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Reexamination Certificate
1997-01-13
2001-03-27
Tsang, Fan (Department: 2746)
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
C455S091000, C455S069000, C330S051000, C330S151000
Reexamination Certificate
active
06208846
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a radio frequency (RF) power level control circuit and, more particularly, to a circuit for increasing the efficiency of the power amplifier in mobile telephone units.
BACKGROUND OF THE INVENTION
In all radio frequency (RF) communication systems, the power needed to transmit a signal consumes a large proportion of the available energy. An increase in the efficiency of the transmitting circuit of a communication device would decrease its power consumption. In addition, low power consumption due to higher efficiency reduces the heat generated in each communication device due to internal power dissipation.
Compact size and low weight are desirable features in cellular and other portable radio telephones (hereinafter referred to as mobile units). The power needed to operate a mobile unit is usually drawn from a battery. Since the battery is typically the largest and heaviest device in a mobile unit, increasing the efficiency of the mobile unit—and specifically of the transmitting circuit—would allow a smaller battery to be used, thereby decreasing the overall size and weight of the mobile unit.
The transmitting circuit of a typical mobile unit includes an RF source, a driver amplifier circuit, a power amplifier circuit and an antenna. (The driver amplifier and the power amplifier are sometimes referred to together as a two-stage power amplifier circuit.) The driver amplifier circuit and the power amplifier circuit include power transistors which amplify an RF signal generated by the RF source.
When the typical mobile unit is active, the driver and power amplifier are continuously on. Applicants have recognized, however, that the power needed to transmit a signal from the mobile unit to a base station does not always require the full operating power of the driver and power amplifiers. That is, it is estimated that for many applications the power amplifier is actually only required approximately twenty percent of the time (e.g., near the fringe of a cell, behind a structure, etc.) Accordingly, during the majority of the time the mobile unit is being used, the driver amplifier alone can produce a signal strong enough so that it will be detected by the base station.
Presently, several techniques have been devised that attempt to increase the efficiency of power amplifiers. These techniques include circuits that control the drain or collector supply voltage of the transistors used in a linear power amplifier; utilization of quasi-linear amplifiers; and utilization of non-linear precompensation circuits (e.g., a feedback controlled predistortion circuit). However, each of the aforementioned techniques require additional—and usually complex—circuitry and have difficulty maintaining the desired linear amplification (this is especially true because of the harsher environmental conditions to which mobile units are exposed). Furthermore, these techniques usually increase the heat generated in the mobile unit due to internal power dissipation of the additional circuitry.
SUMMARY OF THE INVENTION
The subject invention includes a method and apparatus for increasing the efficiency of the transmitter circuit of a mobile unit. Specifically, the subject invention includes a power control circuit that regulates the operation of the power amplifier stage of the transmitter circuit.
In accordance with the subject invention, the power control circuit includes a driver amplifier and a power amplifier, each having an input and an output, and two three-way switches. The input of the driver amplifier defines the input of the power control circuit. The output of the power control circuit is switchable between the output of the driver amplifier or the output of the power amplifier.
Each three-way switch has two terminals which are selectably connected to a common terminal. The common terminal of a first three-way switch is connected to the output of the driver amplifier; a first selectable terminal of the first switch is connected to the input of the power amplifier. The common terminal of the second three-way switch generally defines the output of the power control circuit and is connected to the antenna of the mobile unit. A first selectable terminal of the second switch is connected to the output of the power amplifier, and the second selectable terminal of the second switch is connected to the second selectable terminal of the first switch.
Control means is used to control the operation of said power amplifier and said first and second switches. The control means cooperates with the receiver circuitry of the mobile unit. During regular operation, the power amplifier is not used and the control means bypasses the power amplifier. This is accomplished by deactivating the power amplifier and routing the output signal from the driver amplifier through the first switch, then to the second switch and, finally, to the antenna.
If the receiver circuitry detects that the signal strength from the base station is too weak or below a predetermined value, it sends a “weak signal strength” control signal to the control means. When the control means receives the weak signal strength control signal, it activates the power amplifier, connects the driver amplifier to the power amplifier via the first switch, and connects the output of the power amplifier to the antenna via the second switch. That is, the connection between the first and second switches via the second selectable terminals is interrupted and the first selectable terminal of each switch is connected to its respective common terminal.
In some cellular telephone systems, the base station monitors the signal it receives from the mobile unit. When the base station detects that the signal it is receiving falls below a predetermined level, the base station sends a command signal back to the mobile unit directing the mobile unit to increase its transmitting power. (This can be done by changing the output power of the RF source, increasing the gate voltage of one of the power transistors or increasing the base current of one of the power transistors.) The control means of the subject power control circuit can be easily adapted to communicate with the receiver circuit of the mobile unit for using the command signal from the base station to regulate the operation of the power amplifier and the three-way switches.
REFERENCES:
patent: 4613990 (1986-09-01), Halpern
patent: 4811421 (1989-03-01), Havel et al.
patent: 5101507 (1992-03-01), Jung
patent: 5152004 (1992-09-01), Vaisanen et al.
patent: 5175871 (1992-12-01), Kunkel
patent: 5426641 (1995-06-01), Afrashten et al.
patent: 5530923 (1996-06-01), Heinonen et al.
patent: 5548246 (1996-08-01), Yamamoto et al.
patent: 5661434 (1997-08-01), Brozovich et al.
patent: 5872481 (1999-02-01), Sevic et al.
patent: 5909643 (1999-06-01), Aihara
High-Efficiency Amplifiers for Portable Handsets; T. Mader, M. Marković, Z. Popvić and R. Tayrani; Sixth IEEE Int'l Symposium on Personal, Indoor and Mobile Radio Communications, Sep. 27-29, 1995; pp. 1242-1245.
Analysis and Design of a Two-Loop Controlled Switching Power Amplifier; H. Endo, T. Yamashita and T. Sugiura; IEICE Trans. Commun., vol. E76-B, No. 9, Sep. 1993; pp. 1193-1201.
High Efficiency Transmitting Power Amplifiers for Portable Radio Units; T. Nojima, S. Nishiki and K. Chiba; IEICE Transactions, vol. E74, No. 6, Jun. 1991, pp. 1563-1570.
Chen Young-Kai
Kasturia Sanjay
Lin Jenshan
Tsai Huan-Shang
Lucent Technologies - Inc.
Sobutka Philip J.
Synnestvedt & Lechner LLP
Tsang Fan
LandOfFree
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