High efficiency amplifier with amplifier element, radio...

Wave transmission lines and networks – Coupling networks – With impedance matching

Reexamination Certificate

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C333S001100

Reexamination Certificate

active

06833771

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high efficiency amplifiers, radio transmission devices and measuring devices for high efficiency amplifiers, and more particularly to high efficiency amplifiers used particularly in mobile communication apparatus, microwave band communication apparatus or the like, constituted of semiconductor amplifiers for amplification in devices, such as, FET's (Field Effect Transistors), transistors or the like, and, to radio transmission devices with the high efficiency amplifiers and measuring devices for the high efficiency amplifiers.
2. Description of the Background Art
With reference to
FIG. 35
, a conventional radio transmission unit (first example of a conventional art) used in portable remote terminals will be described. In
FIG. 35
, a radio transmission unit
9100
includes a high efficiency amplifier
101
, non-reciprocal circuit element
103
, and a transmission line
102
connecting high efficiency amplifier
101
and non-reciprocal circuit element
103
.
High efficiency amplifier
101
includes an input matching circuit
104
, a first-stage amplifier
105
, an interstage matching circuit
106
, a second-stage amplifier
107
and an output matching circuit
108
. Between an input terminal and an output terminal of high efficiency amplifier
101
, input matching circuit
104
, first-stage amplifier
105
, interstage matching circuit
106
, second-stage amplifier
107
and output matching circuit
108
are connected in this order.
Output matching circuit
108
includes a harmonic processing circuit
111
and a fundamental wave matching circuit
112
. Harmonic processing circuit
111
is a circuit for processing a harmonic and performs an operation such as impedance matching of a harmonic. Fundamental wave matching circuit
112
performs impedance matching of a fundamental wave.
In mobile communication apparatus or the like, a non-reciprocal circuit element is employed in an isolator or the like for achieving a highly efficient operation of an amplifier regardless of the condition of an antenna. Hereinbelow, as an example of the non-reciprocal circuit element, an isolator will be described. An isolator
103
includes an input matching circuit
109
connected to transmission line
102
and an isolator body
110
connected between input matching circuit
109
and an output terminal.
The output impedance of high efficiency amplifier
101
and input/output impedance of isolator
103
are 50&OHgr;, because a high-frequency measuring device conventionally used for the evaluation of high-frequency apparatus is formed to have 50&OHgr; (hereinafter the letter &OHgr; represents ohm) termination. On the other hand, the output impedance of second-stage amplifier
107
is 1~10&OHgr;. Therefore, fundamental wave matching circuit.
112
is formed as a converter circuit to convert the output impedance of second-stage amplifier
107
(1~10&OHgr;) to 50&OHgr;.
A signal input from the input terminal is amplified by high efficiency amplifier
101
. The amplified signal is output via transmission line
102
and isolator
103
. Reflected waves generated after the signal passed isolator
103
is blocked by isolator
103
. Therefore, the reflected wave does not go back to high efficiency amplifier
101
and highly efficient stable operation of high efficiency amplifier
101
is allowed.
In recent years, portable remote terminals are becoming smaller and lighter, and the reduction in size and weight are now key factors in the development. What contributes most to this purpose is reduction in size of battery. In order to realize smaller battery while enabling a certain length of conversation, implementation of a high efficiency amplifier is important because the amplifier consumes a large part of power consumed in the device.
In the structure of radio transmission unit
9100
as described above, however, loss in fundamental wave matching circuit
112
is large and it is difficult to realize a highly efficient amplifier.
One way to improve the efficiency is to establish the relation, 2&OHgr;<Z<12.5&OHgr;, between the output impedance of the high efficiency amplifier, the input impedance of the non-reciprocal circuit element (isolator) and impedance Z of the line connecting the high efficiency amplifier and the non-reciprocal circuit element, as described in “Non-reciprocal Circuit Element and Composite Electronic Component (Japanese Patent Laying-Open No. 10-327003)”.
An example of the radio transmission unit (second example of a conventional art) employing a low impedance isolator as described in the above cited document will be described with reference to
FIG. 36. A
radio transmission unit
9200
shown in
FIG. 36
is constituted of a low impedance high efficiency amplifier
113
, a low impedance transmission line
114
and a low impedance isolator
115
. The output impedance of low impedance high efficiency amplifier
113
is lower than 50&OHgr;, the input impedance of low impedance isolator
115
is lower than 50&OHgr; and the output impedance of low impedance isolator
115
is 50&OHgr;).
High efficiency amplifier
113
is constituted of an input matching circuit
104
, a first-stage amplifier
105
, an interstage matching circuit
106
and a second-stage amplifier
107
.
Isolator
115
includes an isolator body
110
and a low impedance input matching circuit
116
performing impedance matching between isolator body
110
and transmission line
114
.
In the second example of a conventional art, the output impedance of high efficiency amplifier
113
is 1&OHgr;~10&OHgr; (the output impedance of second-stage amplifier
107
.) Input matching circuit
116
in isolator
115
adjusts the input impedance of the low impedance isolator to match with the output impedance of high efficiency amplifier
113
.
Compared with the first example of a conventional art, the second example does not include the output matching circuit in the high efficiency amplifier. Hence, the loss generated in output matching circuit
108
is eliminated and the current consumption in the structure as a whole including the high efficiency amplifier and the isolator is reduced. The second example of a conventional art, however, has the following problems.
First, fundamental wave matching circuit
112
in the first example is constituted of a combination of a series inductance, a parallel capacitor and so on and serves as a reject filter for a harmonic such as a second harmonic and a third harmonic. On the other hand, in the second example, leakage power associated with harmonic increases, because the second example does not include fundamental wave matching circuit
112
.
To solve this problem, addition of a high harmonics reject filter circuit is effective. The filter circuit can be added in a low impedance line or in a high impedance line. The effect of harmonic rejection is more significant when the filter circuit is added to the high impedance circuit, in which the impedance of harmonic of the filter circuit appears to be relatively low. Therefore, in the second example of a conventional art, a filter circuit
117
may be added to the output side (where impedance is connected to the 50&OHgr; transmission line) of isolator
115
as shown in FIG.
36
.
When the leakage power associated with the harmonics is suppressed by the addition of the filter circuit, however, the current consumption of the high efficiency amplifier is increased because of the loss generated in the filter circuit.
In addition, as a conventional measuring device for evaluating these circuits is designed based on the standard value of 50&OHgr;, the measurement of the circuit with different impedance is difficult.
SUMMARY OF THE INVENTION
Hence, the present invention is made to solve the above described problems and its object is to provide high efficiency amplifiers with low current consumption and high efficiency and radio transmission devices, and measuring devices for evaluating the high efficiency amplifiers.
In one aspect of the present invention, a high effic

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