Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Reexamination Certificate
1998-12-01
2001-07-10
Maung, Nay (Department: 2681)
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
C455S091000, C330S065000, C330S133000, C330S134000, C330S254000, C330S255000
Reexamination Certificate
active
06259901
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a radio-frequency (RF) power amplifier of mobile communication equipment, and more particularly, to an RF power amplifier of portable mobile communication equipment which improves the quality of a transmission signal and reduces its electric power consumption.
2. Related Art
A mobile communication system has been widely utilized for radio-frequency communication between a number of pieces of mobile. communication equipment and base stations located at a distance from one another in a service area. Such communication system is constructed in various manners in accordance with the purpose of service or the like. For example, in a land-based mobile communication system, the mobile communication equipment is realized as a car telephone, a portable telephone or the like which, when used, is connected with a public telephone network through a base station and a radio link control station.
A typical portable telephone comprises an equipment body including transmission/receiver sections, a telephone set including telephone transmitter/receiver, and an antenna. The equipment body with which the telephone set and the antenna are formed into one piece accommodates therein a battery serving as a power source. The transmitter section includes a sonic-electric converter, modulator, frequency converter, and radio-frequency (RF) power amplifier. Voice applied through a telephone transmitter to the transmission section is subject to sonic-electric conversion, modulation, frequency conversion and power amplification and is radiated in the form of a radio wave.
Conventionally, an RF power amplifier of a transmission section is usually formed solely by single-ended circuits which have a proven track record in hybrid ICs, and is mounted on a printed circuit board or printed wiring board of mobile communication equipment, with the RF power amplifier connected with an RF grounding pattern formed in the circuit board. The RF power amplifier constructed as mentioned above is liable to be affected by the RF grounding pattern, so that the amplification gain and the distortion factor are likely to change, resulting in degraded quality of the transmission signal.
In the case of land-based mobile communication based on a code division multiple access (CDMA) system, the electric field strengths of radio waves transmitted from all the pieces of mobile communication equipment which commonly utilize the same frequency are preferably equalized at the base station. To this end, for example, each mobile communication equipment is arranged to adjust the transmission output power in accordance with a transmission power control signal (gain control signal) transmitted from the base station.
A conventional portable telephone whose transmission section includes an RF power amplifier composed of a single-ended circuit is arranged to make a transmission output adjustment, e.g., by applying the gain control signal to an automatic gain control (AGC) circuit disposed between a modulator and a frequency converter which are located upstream of the RF power amplifier. In other words, generally, the transmission output adjustment is not performed based on a gain adjustment of the single-ended circuit (RF power amplifier) for the reason that the single-ended circuit is likely to operate abnormally to cause undesired oscillation, etc., if the bias current applied thereto is changed so as to change the amplification gain of the single-ended circuit.
Therefore, the RF power amplifier of a conventional portable telephone is arranged to make an amplifying action at a fixed gain. This causes a significant reduction in the power efficiency of the RF power amplifier, especially, in a range of low transmission output level. On the other hand, at the time of transmission, the power consumption of the RF power amplifier makes up a large proportion of the entire power consumption of the mobile communication equipment. Thus, an improvement of power efficiency of an RF power amplifier is intensively demanded, especially in portable mobile communication equipment which is frequently operated in a low output level range and the power source of which is comprised of a battery.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a radio-frequency power amplifier of mobile communication equipment, which prevents a degraded quality of a transmission signal caused by affection of a radio-frequency grounding pattern of a circuit board of the mobile communication equipment on which board the amplifier is mounted.
Another object of the present invention is to provide a radio-frequency power amplifier of mobile communication equipment, which is excellent in power efficiency especially in a range of low transmission output level.
A still further object of the present invention is to provide a radio-frequency power amplifier of mobile communication equipment, the amplification gain of which can be controlled easily and stably.
A further object of the present is to provide a radio-frequency power amplifier of mobile communication equipment, which makes it possible to realize a compact, power saving radio-frequency module having a circuit board on which the radio-frequency power amplifier is mounted together with modulator and frequency converter sections to form a radio-frequency section of a transmitter system of the mobile communication equipment.
According to one aspect of the present invention, a radio-frequency power amplifier of mobile communication equipment comprises: an input stage comprised of at least one differential amplifier arranged to balanced-input and amplify a radio-frequency signal delivered from a frequency converter section of a transmission system of the mobile communication equipment located downstream of a modulator section of the transmission system; and a bias current circuit for supplying said at least one differential amplifier with a bias current varying in dependence on a gain control signal, to thereby variably set a gain of said at least one differential amplifier, said radio-frequency power amplifier being mounted on a circuit board of the mobile communication equipment, said circuit board being formed with a radio-frequency grounding pattern.
Preferably, said input stage of said radio-frequency power amplifier is comprised of a plurality of differential amplifiers which are direct-coupled to one another, and said bias current circuit is provided for each of said plurality of differential amplifiers.
With the radio-frequency power amplifier, the input stage comprised of a differential amplifier which inputs the radio-frequency signal in a balanced manner is virtually grounded with respect to the radio-frequency grounding pattern of the circuit board of the mobile communication equipment on which the radio-frequency power amplifier is mounted. In other words, the differential amplifier which forms the input stage of the radio-frequency power amplifier performs an amplification action under a floating state with respect to the radio-frequency grounding pattern, so that the power amplifier can amplify the radio-frequency signal while maintaining the linearity of the power amplifier, without being affected by the radio-frequency grounding pattern. Since the amplification gain of the differential amplifier can be changed by changing a bias current applied to the differential amplifier in accordance with a gain control signal, the amplification gain can be variably set with ease and stability.
According to another aspect of the present invention, a radio-frequency power amplifier of mobile communication equipment comprises: an output stage comprised of a push-pull circuit arranged to amplify and balanced-output a radio-frequency signal received through and input stage of said amplifier from a frequency converter of a transmission system of the mobile communication equipment located downstream of a modulator of the transmission system; and a bias current circuit for supplying said push-pull circuit with a bias current varying i
Imai Takeshi
Shinomiya Yoshitaka
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Maung Nay
Mobile Communications Tokyo Inc.
West Lewis G.
LandOfFree
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