Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
2001-05-04
2002-11-19
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S101000, C333S109000, C455S078000, C455S083000
Reexamination Certificate
active
06483398
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a directional coupler, a high frequency circuit module comprising the same directional coupler and a wireless communication system comprising the same high frequency circuit module, and particularly to the technique that can effectively be adapted to the wireless communication technology to realize the communication under the stable output of a high frequency power amplifier controlled with high accuracy.
In a transmitting side output stage of a transmitter of wireless communication equipment (mobile communication equipment) such as a mobile telephone set and a hand-held telephone set or the like, an amplifier comprising in the multiple stages a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and a GaAs-MES (Metal Semiconductor) FET or the like is used.
For the hand-held telephone set, a system is already established so that the communication is performed by varying an output depending on the ambient environment with a power control signal transmitted from a base station considering the operational environment and thereby any interference is never generated against the other hand-held telephone sets.
For example, in view of avoiding the interference against the other systems, the power control signal is transmitted from the base station of a digital hand-held telephone system to the hand-held terminals (hand-held telephone sets) in order to provide the minimum output required for the communication. At the inside of a terminal utilizing a higher frequency power amplifier comprising FET such as MOSFET or the like, a microcomputer of the baseband unit monitors the power control signal transmitted from the base station and an output of the high frequency power amplifier to adjust the output power by changing a power control signal (Vapc) to be applied to the control terminal of the high frequency power amplifier.
This high frequency power amplifier is described in “The Nikkei Electronics”, Jan. 27, 1997, p115 to p126, published by the Nikkei BP Co., Ltd. This reference reports the standard system of the 900 MHz Band Cellular System Hand-Helt Telephone System in the North America and the GSM (Global System for Mobile Communications) system in Europe.
Moreover, “The Hitachi Review”, Vol. 79, No. 11 (1997), P63 to P38, published by the Hitachi Review Co., Ltd. reports an analog signal processing IC of high frequency unit for digital cellular standards “GSM/EGSM”. This reference discloses a block diagram for detecting an output of the high frequency power amplifier with a directional coupler and for controlling a power amplifier module with a power detection signal.
A directional coupler is described, for example, in the “Basic Items and Applications of a Microwave Circuit”, Jul. 10, 1997; P191 to P193, published by the General Electronics Publication Co., Ltd. This reference reports a distributed coupling type directional coupler.
On the other hand, “The Electronic Materials”, April, 1999, P91 to P95, published by the Industrial Investigation Society reports a ceramics-laminated low-pass filter and a directional coupler for 1608 type mobile communication. These low-pass filter and directional coupler are formed as the discrete parts.
SUMMARY OF THE INVENTION
In the hand-held telephone system, base stations transmit, to the hand-held terminals (hand-held telephone sets) the signal (power control signal) to control the transmission power to provide the minimum output required for communication. In the hand-held terminals, a high frequency power amplifier of the output stage in the transmitting side is controlled with an APC (Automatic Power Control) circuit operating based on such control signal. Namely, the high frequency amplifier is controlled to provide the output required for communication. To realize such control operation, a circuit for detecting the power of the power amplifier is required.
A directional coupler is used for detecting an output of the high frequency power amplifier and in addition employs a method of comprising a discrete directional coupler as an external part and a structure to form, through direct depiction, a part corresponding to a coupler on a dielectric material substrate based on the concept of &lgr;/4 line.
That is, the aforementioned reference (Basic Items and Applications of the Microwave Circuit) discloses a structure where a conductor pattern is provided at one surface of the dielectric material substrate as one of the directional couplers and a ground conductor is also provided at the rear surface. In this specification of the present invention, this structure is called a parallel type directional coupler. In this parallel type directional coupler, the conductor pattern is formed as the distributed coupling type parallel two lines. Namely, the main line as the transmission path and the sub-line as the line for detection are extended in the width of the same size for the predetermined distance in the constant interval.
Moreover, one of the other directional couplers disclosed has a structure that two strips are formed by overlapping the main line and sub-line within the dielectric material via the dielectric material layer. In this specification, this structure is called an overlapping type directional coupler. This overlapping type directional coupler also has the structure that the main line and sub-line of the width in the same size are also extended for the predetermined distance with a constant interval therebetween.
However, in these directional couplers, the line width is equal in the main line (transmission line) and sub-line (detection line). Therefore, particularly in the case of the overlapping type directional coupler, if the sub-line is deviated for the main line, an output value of the directional coupler will be changed easily. As a result, when the high frequency circuit module such as a high frequency power amplifier (high frequency power amplifier module) is controlled with this detection signal, it becomes difficult that an output of the high frequency circuit module is controlled with higher accuracy. Therefore, a wireless communication system comprising such high frequency circuit module has come to have a fear for disabling stable communication.
An object of the present invention is to provide a directional coupler that can detect a transmission output of a main line with higher accuracy.
Another object of the present invention is to provide a high frequency circuit module comprising a directional coupler that can detect an output with higher accuracy.
The other object of the present invention is to provide a wireless communication system assuring stable a communication by monitoring an output with higher accuracy.
The aforementioned and the other objects and novel characteristics of the present invention will become more apparent from the description of this specifications and the accompanying drawings thereof.
The summary of the typical inventions of those disclosed in the resent application will be briefly explained as follows.
(1) A directional coupler includes a main line forming the transmission line and a sub-line forming the detection line which are different respectively in the line width. For example, the width of the main line is wider than the sub-line. In the overlapping type directional coupler, both side edges of the sub-line are located, in the main line and sub-line that are overlapped with each other, at the inside of both side edges of the main line.
(2) In the high frequency circuit module comprising an amplifying system comprising a plurality of stages of the amplifying stage including at least the initial stage and the final stage and a directional coupler for detecting an output of the final stage of the amplifying system, the line width of the main line forming the transmission line of the directional coupler is wider than the sub-line forming the detection line. The directional coupler is of the overlapping type and both side edges of the sub-line, in the main line and sub-line that are mutually overlapped with each other, are neve
Akamine Hitoshi
Arai Satoshi
Imai Shun
Nagamori Hiroyuki
Nunogawa Yasuhiro
Hitachi , Ltd.
Pascal Robert
Takaoka Dean
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