The present patent application claims priority from Japanese application JP 2003-118030 filed on Apr. 23, 2003, the content of which is hereby incorporated by reference into this application.
The present invention relates to a radio frequency power amplifier used in the transmitting part of a radio communications apparatus, such as a cellular phone, and, more particularly to a radio frequency power amplifier module having a bias control circuit.
A radio frequency power amplifier used in a radio communications apparatus, such as a cellular phone, in a mobile communications system is classified roughly into a radio frequency power amplifier part that amplifies a radio frequency power and a bias control part that supplies the radio frequency power amplifier part with a direct current voltage. Further, usually, the power amplifier mounts these parts in a module substrate and is constituted as a radio frequency power amplifier module.
The bias control part controls an operating current and an operating voltage of the radio frequency power amplifier part so that the radio frequency power amplifier part can maintain a stable radio frequency characteristic against a change in the environment, such as a temperature change, and is very important. The radio frequency power amplifier part is usually controlled by changing a bias voltage at the input side of a semiconductor element that constitutes the radio frequency power amplifier part.
The bias voltage is supplied from the bias control part to the radio frequency power amplifier part via a bias supply line. At this occasion, if a radio frequency signal leaks to the bias control part through the bias supply line, the bias control part becomes unstable in an operation depending on the leakage signal. When the amount of leakage is increased, that results in an erroneous operation.
A series inductance is inserted into the bias supply line to suppress such an erroneous operation with a radio frequency signal. Consequently, the bias supply line reaches high impedance in the frequency of the radio frequency signal and the radio frequency signal arriving at the bias control part is attenuated. Conventionally, chip components or a spiral structure formed in a semiconductor element was used as this inductance.
Still more, there is an example that a bonding wire for wiring formed on a module substrate is used as an inductance. The example in which the inductance with such a bonding wire is used in a part of the wiring of a semiconductor amplifier element that is not for a bias supply line is disclosed in Japanese Patent Laid-Open No. H6(1994)-224660.
A radio frequency power module in which a series inductance is inserted into a bias supply line can be constituted as shown in
In a radio frequency power amplifier module used in a radio communications apparatus, such as a cellular phone, downsizing and weight reduction are advancing rapidly at present. In such circumstances, when the inductance chip components described in the Background of the Invention are used as the inductors 908 and 909, a problem is arisen that a degree of freedom of mounting other components is limited due to loading of relatively large inductance chip components on the module substrate the downsizing of which is advancing.
Further, if an attempt is made to obtain an inductance value with a fixed amount when an inductor having a spiral structure formed in a semiconductor element is used as the inductors 908 and 909, the inductor is formed in a thin pattern and the resistance component of an inductance increases. As a result, a problem is arisen that a bias voltage drop occurs, then semiconductor area increases to cause an increased chip price.
Further, when a bonding wire is utilized as the inductors 908 and 909, the bonding wire is limited in length that can be secured on a module substrate. Accordingly, a sufficient inductance value is not obtained and the attenuation of a radio frequency signal is inevitably insufficient.
The object of the present invention is to provide a radio frequency power amplifier module that brings sufficient attenuation to a radio frequency signal in a bias supply line that connects a bias control part and a radio frequency power amplifier part.
The aforementioned problem of the present invention can be dissolved effectively by using at least a bonding pad having a capacitance component to a ground and a bonding wire formed via the bonding pad in the bias supply line that connects the bias control part and the radio frequency power amplifier part.
If such a means is adopted, since a low pass filter is formed by a capacitance with the bonding pad and an inductance with the bonding wire, the filter can bring sufficient attenuation to the radio frequency signal. Further, because the bonding pad and the bonding wire can be arranged freely on a module substrate and even the occupied area is small, the module substrate area need not be increased. Still more, the bonding pad having a capacitance component to the ground can be realized by, for example, forming the bonding pad on the module substrate and a ground conductor on the surface at the opposite side of the bonding pad of the module substrate.
These and other objects and many of the attendant advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.
A radio frequency power amplifier module according to the present invention is described below with reference to the embodiments of the invention shown in the drawings. Identical symbols in
A radio frequency signal is input from a radio frequency signal input port (RF IN) 101, then amplified in the radio frequency power amplifier part 103 and output from a radio frequency signal output port (RF OUT) 102. A direct current voltage for the bias control part 104 is input from a direct current input port (Vbias) 107. The direct current voltage is converted to a first stage bias and a final stage bias of 2-stage amplification in the bias control part 104 and supplied to the first and final stages of the radio frequency power amplifier part 103 via the bias supply lines 109 and 108, respectively.
The bias supply lines 108 and 109 are composed of a bonding wire 105 formed via a bonding pad 106 having a capacitor component to a ground, and the bonding wire 105 assumes an inductance. Since the bonding wire 105 forms a shape exactly like a stitch by tracing a. bonding pad 106, a bias supply line is referred to as a “stitch structure inductance” anew.
The details of this stitch structure inductance 108 or 109 are shown in
The equivalent circuit of
In the circuit described in
The stitch structure inductance shown in
Further, although not shown, a stitch structure inductance is formed on a semiconductor substrate when a radio frequency power amplifier part and a bias control part are constituted as a semiconductor integrated circuit on the same semiconductor substrate.
Still more, to realize a stitch structure, all stitch structures can be constituted of mutual connection from a first dielectric substrate (second substrate) 703 having the stitch structure to a second dielectric substrate 702, as shown in
Further, the bias control part 104 is composed of a circuit that converts the direct current voltage input from the direct current input port 107 into a bias voltage using a transistor element, as shown in
According to the present invention, since a low pass filter is formed equivalently in the bias supply line connecting a bias control part and a radio frequency power amplifier part, the leakage of a radio frequency signal into the bias control part is suppressed, and, accordingly, the stable operation of the bias control part is obtained. As a result, the radio frequency characteristic of the radio frequency power amplifier part can be retained satisfactorily. Further, when inductance chip components or a spiral inductor is used or composed of a single bonding wire module by employing a combined bonding wire formed via a bonding pad having a capacitance, an increase in installation area is prevented. Consequently, a compact, lightweight, and low-cost radio frequency power module can be realized.
It is further understood by those skilled in the art that the foregoing description is a preferred embodiment of the disclosed device and that various changes and modifications may be made in the invention without departing from the spirit and scope thereof.
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Number | Date | Country | |
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