Amplifiers – Involving structure other than that of transformers per se
Reexamination Certificate
2000-10-12
2002-05-28
Lee, Benny (Department: 2817)
Amplifiers
Involving structure other than that of transformers per se
C330S066000
Reexamination Certificate
active
06396342
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a microwave amplifier for amplifying microwave power, and more particularly to a microwave amplifier for generating high output microwave power that is reduced in distortion for applications to satellite and cellular communication, and industrial, scientific, and medical technology.
The microwave amplifier has a field effect transistor such as a compound semiconductor field effect transistor which is superior in high speed and high frequency performances, for example, a GaAs field effect transistor. The microwave amplifier is required to have high output and high efficient performances or characteristics for realizing further reductions in size and power consumption thereof. For these purposes, it is required that the microwave amplifier is superior in linearity with a reduced relative modulation distortion to avoid any undesirable influence to other channels. If plural microwaves including different carrier frequencies are inputted into the single microwave amplifier, non-linearity of the microwave amplifier generates not only the relative modulation distortion also a secondary distortion due to differential frequency of the different carrier frequencies.
The microwave amplifier is so designed that plural field effect transistors are connected in parallel to each other to form a multiple finger structure and to increase a gate width. If the microwave amplifier is high in impedance in a low frequency band, then the increased secondary distortion appears on the frequencies of the input signals, whereby the input signals show mixing with the amplified signals at drain electrodes of the field effect transistors. As a result, the relative modulation distortion is increased. This means that the linearity of the field effect transistors is never utilized effectively.
In order to solve the above problem, it was proposed to have improved the distortion characteristic of the microwave amplifier even for amplifying the microwave including plural different carrier frequencies. This conventional technique is disclosed in Japanese laid-open patent publication No. 10-233638.
FIG. 1
is a schematic diagram illustrative of a first conventional microwave amplifier having improved the distortion characteristic of the microwave amplifier for amplifying the microwave including plural different carrier frequencies, wherein plural field effect transistors are internally matched to each other for parallel operations thereof. The conventional microwave amplifier has an input gate electrode
70
for receiving inputs of plural input microwaves and an output drain electrode
76
from which a synthesized microwave is outputted. The conventional microwave amplifier has a distributor circuit
71
, a first impedance-matching circuit
72
, a second impedance matching circuit
82
, a first field effect transistor circuit
73
, a second field effect transistor circuit
83
, a first bonding pattern
77
, a second bonding pattern
87
, a first micro-strip line
51
, a second micro-strip line
52
, a first capacitor
55
, a second capacitor
56
, a third impedance-matching circuit
74
, a fourth impedance-matching circuit
84
, and a synthesizer circuit
75
. The distributor circuit
71
has a single input which is connected to the input gate
70
and a first output connected to the first impedance-matching circuit
72
and a second output connected to the second impedance matching circuit
82
. The first impedance-matching circuit
72
has an input side connected to the first output of the distributor circuit
71
and an output side connected to an input side of the first field effect transistor circuit
73
. The second impedance-matching circuit
82
has an input side connected to the second output of the distributor circuit
71
and an output side connected to an input side of the second field effect transistor circuit
83
. The first field effect transistor circuit
73
has an input side connected to the first impedance-matching circuit
72
and an output side connected through the first bonding pattern
77
to an input side of the third impedance-matching circuit
74
. The second field effect transistor circuit
83
has an input side connected to the second impedance-matching circuit
82
and an output side connected through the second bonding pattern
87
to an input side of the fourth impedance-matching circuit
84
. The third impedance-matching circuit
74
has the input side connected through the first bonding pattern
77
to the first field effect transistor circuit
73
and an output side connected to a first input side of the synthesizer circuit
75
. The fourth impedance-matching circuit
84
has the input side connected through the second bonding pattern
87
to the second field effect transistor circuit
83
and an output side connected to a second input side of the synthesizer circuit
75
. The synthesizer circuit
75
has the first input side connected to the third impedance-matching circuit
74
and the second input side connected to the fourth impedance-matching circuit
84
as well as has an output side connected to the drain output electrode
76
. Further, the first micro-strip line
51
and the first capacitor
55
are connected in series between the first bonding pattern
77
and a first ground electrode GND-1 to form a first LC circuit, wherein the first micro-strip line
51
is shorter than one-quarter microwave for smoothing the secondary distortion due to the differential frequency of the carrier frequencies. The second micro-strip line
52
and the second capacitor
56
are connected in series between the second bonding pattern
87
and a second ground electrode GND-2 to form a second LC circuit, wherein the second micro-strip line
52
is shorter than one-quarter microwave for smoothing the secondary distortion due to the differential frequency of the carrier frequencies.
The microwave signals including the plural different carrier frequencies are inputted into the input gate electrode
70
and the inputted microwave signals are then distributed by the distributor circuit
71
to both the first and second impedance-matching circuits
72
and
82
for executing the impedance-matching to the distributed microwave signals. The impedance-matched microwave signals are then amplified by the first and second field effect transistor circuits
73
and
83
. The amplified microwave signals are further transmitted through the first and second bonding patterns
77
and
87
to the third and fourth impedance-matching circuits
74
and
84
, wherein the secondary distortions of the amplified microwave signals due to the differential frequencies of the different carrier frequencies are smoothed by the first and second LC circuits having the first and second micro-strip lines
51
and
52
and the first and second capacitors
55
and
56
. The amplified and smoothed microwave signals are then transmitted to the third and fourth impedance-matching circuits
74
and
84
for executing further impedance-matching to the signals. The impedance matched microwave signals are then transmitted to the synthesizer circuit
75
for generating a synthesized microwave output signal which is to be outputted from the drain output terminal
76
.
If the microwaves including plural different carrier frequencies are inputted into the above conventional microwave amplifier, then the secondary distortion is generated due to the differential frequency of the carrier frequencies. If, for example, the microwave includes first and second carrier frequencies f
1
and f
2
different from each other, then the secondary distortion has a differential frequency defined to be |f2-f1| which increases the relative modulation distortion. For these reasons, the first and second LC circuits comprising the first and second micro-strip lines
51
and
52
and the first and second capacitors
55
and
56
are provided for reducing the impedance by the resonance. Further, the first and second LC circuits are connected to the first and second ground electrodes
55
a
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