Wave transmission lines and networks – Coupling networks – Delay lines including long line elements
Reexamination Certificate
1999-09-22
2002-01-08
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Coupling networks
Delay lines including long line elements
C333S156000
Reexamination Certificate
active
06337609
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a delay compensation device and a delay line component for a radio frequency low distortion power amplifier used in a radio base station of portable phone communication systems and to a manufacturing method of the delay line component.
BACKGROUND ART
In a radio base station of potable phone communication system, the final stage of a radio frequency power amplifier is required to simultaneously amplify a number of different radio frequency signals which are amplitude modulated or frequency modulated for communication. In such a high power radio frequency amplifier used in the radio base station, the signals are usually affected by non-linear operation characteristics of used active components like transistors. Once the signals are affected by such non-linear characteristics, third harmonic inter modulation distortion (hereinafter called as “IMD ”) is caused and unnecessary radiation interference is resulted. To suppress such interference, some linearisation processing is necessary in radio frequency power amplification. To prevent IMD, an amplifier by feed-forward method (hereinafter called as “FF”) is used as shown in FIG. 1 (Japanese Unexamined Patent Publication No.6-224650).
In the figure, the reference number
10
is an input terminal of radio frequency signals for amplification,
11
is the first directional coupler connected with the input terminal
10
,
12
is a main amplifier connected with the coupling port of the first directional coupler
11
,
13
is a first delay compensation device connected with the primary output port of the first directional coupler
11
,
14
is a second directional coupler connected with the output of the main amplifier
12
,
15
is a third directional coupler connected with the output of the first delay compensation device
13
and with the coupling port of the second directional coupler
14
,
16
is an error amplifier connected with the primary output port of the third directional coupler
15
,
17
is a second delay compensation device connected with the primary output port of the third directional coupler
14
,
18
is a fourth directional coupler connected with the output of second delay compensation device
17
and with the output of the error amplifier
16
, and
19
is an output terminal of amplified radio frequency signals connected with the primary output port of the directional coupler
18
.
As will be apparent from
FIG. 1
, an input radio frequency signal via the input terminal
10
is divided into two signals by the first directional coupler
11
, and one of the divided signal is amplified by the main amplifier
12
which generates IMD components (distortion signals) resulted from its non-linearity characteristics in addition to the main signals. The other of the divided signal propagates the first delay compensation device
13
which has a similar delay characteristic as the main amplifier
12
. By the directional coupler
15
, the output of the delay compensation device
13
is inversely added with the signal, which is adjusted by signal level and phase controllers not shown in the
FIG. 1
, from the coupling port of the directional coupler
14
. As a result, the two main signal components are canceled each other, and only IMD component (distortion signals) is left. The IMD component is amplified at the error amplifier
16
up to the level that is needed to cancel the IMD component generated in the main amplifier
12
.
The output signal of the main amplifier
12
propagates the second delay compensation device
17
which has a similar delay characteristic as the error amplifier
16
. And the output signal of the second delay line device
17
is inversely added with the IMD component from the error amplifier
16
by the fourth directional coupler
18
. Consequently, the two components of IMD are canceled each other and only the amplified radio frequency signal via the input terminal
10
is output via the output terminal
19
. By this configuration, a radio frequency amplifier system with good distortion characteristics can be built.
However, this kind of FF type amplifier has problems shown below.
(1) The typical requirement of delay time of the delay compensation device for such amplifier is tens of nanoseconds. If a coaxial cable type of delay line is used for the delay compensation device, the delay time of tens of nanoseconds requires a few meters length of the coaxial cable. That results in very large physical size. And definite propagation loss is resulted when small diameter coaxial cable is applied for physical size reduction.
(2) If a filter by combined resonators is applied for the delay compensation device, more than 10 stages of the resonators are required to achieve tens of nanoseconds. This results in large propagation loss, increased work load of assembling and difficulty in parameter adjusting.
(3) If a micro strip line structure is used as shown in Japanese Unexamined Patent Publication No.2-24120, the propagation loss becomes very large because of electromagnetic energy concentration at the side edges of strip line conductor.
(4) In an actual power amplifier system, the main amplifier and the error amplifier have independent and different frequency transfer characteristics. And in order to completely remove IMD components, the frequency transfer characteristics of the two different amplifiers must be adjusted to be matched each other in a certain frequency range. This requires very complicated and careful tests and adjustments of the main amplifier and the error amplifier after the build of the power amplifier system. The work load of manufacturing is remarkably increased.
DISCLOSURE OF INVENTION
It is therefore an object of the present invention to solve the problems in the conventional art, and to provide a delay compensation device, a delay line component and manufacturing method of the delay line component that can contribute to realize small propagation loss in a radio frequency and a very small physical bodied device.
Another object of the invention Is to provide a delay compensation device, whereby two frequency transfer characteristics of a main amplifier and an error amplifier can be easily adjusted and matched each other.
The present invention provides a delay line component with coaxial cable structure, including a center conductor, a dielectric which surrounds the center conductor and an outer conductor which is formed outside the dielectric. The dielectric is made of a ceramic dielectric with a large dielectric constant.
In order to get for example 35 nanoseconds of delay time, 10.5 meters length of a line in vacuum environment is needed. An usually widely used coaxial cable uses dielectric insulator with the dielectric constant of ∈r=2-3, and around 7 meters of such cable is necessary for 35 nanoseconds delay. In the present invention, a large dielectric constant ceramic insulator is used for the coaxial cable dielectric material, and consequently the cable length can be greatly reduced. If the used ceramic insulator's dielectric constant is ∈r=92, the propagation velocity factor expressed by root square of ∈r becomes about 9.6. The necessary length by such coaxial cable for 35 nanoseconds delay is only about 1.1 meters.
It is preferred that the ceramic dielectric in the coaxial cable structure is made of sintered ceramic materials or a dielectric with a resin in which ceramic particles are included.
It is preferred that at least the center conductor is made of a metal conductor with no grain boundary
It is also preferred that the center conductor is formed by a metal conductor melted and sintered in a center hole of the ceramic dielectric, by a pipe-shaped metal conductor inserted and rolled in a center hole of the ceramic dielectric, or by a wire-shaped solid metal conductor inserted into a center hole of the ceramic dielectric.
If the center conductor is formed by a pipe-shaped metal conductor rolled in the center hole of the ceramic dielectric, preferably, this center conductor is formed by a metal conduc
Endou Kenji
Fujii Tadao
Yasukawa Yoshiyuki
Arent Fox Kintner & Plotkin & Kahn, PLLC
Glenn Kimberly E
Lee Benny
TDK Corporation
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