U.S. patent application number 11/434889 was filed with the patent office on 2006-11-23 for matching circuit.
This patent application is currently assigned to NTT DoCoMo, Inc.. Invention is credited to Atsushi Fukuda, Shoichi Narahashi, Hiroshi Okazaki.
Application Number | 20060261911 11/434889 |
Document ID | / |
Family ID | 36609465 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060261911 |
Kind Code |
A1 |
Fukuda; Atsushi ; et
al. |
November 23, 2006 |
Matching circuit
Abstract
The present invention has for its object to provide a matching
circuit with multiband capability which can be reduced in size,
even if the number of handled frequency bands rises. The matching
circuit of the present invention comprises a load having
frequency-dependent characteristics, a first matching block
connected with one end to the load with frequency-dependent
characteristics, and a second matching block formed by lumped
elements connected in series to the first matching block. And then,
when a certain frequency band is used, matching is obtained with
the series impedance of the first matching block and the second
matching block. When a separate frequency band is used, a .pi.-type
circuit is constituted by connecting auxiliary matching blocks to
both sides of the second matching block. Next, at the same
frequency, by taking the combined impedance of this .pi.-type
circuit and a load whose characteristics do not depend on the
frequency to be Z0, the influence of the second matching block is
removed.
Inventors: |
Fukuda; Atsushi;
(Yokohama-shi, JP) ; Okazaki; Hiroshi;
(Yokosuka-shi, JP) ; Narahashi; Shoichi;
(Yokohama-shi, JP) |
Correspondence
Address: |
C. IRVIN MCCLELLAND;OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
NTT DoCoMo, Inc.
Chiyoda-ku
JP
|
Family ID: |
36609465 |
Appl. No.: |
11/434889 |
Filed: |
May 17, 2006 |
Current U.S.
Class: |
333/32 |
Current CPC
Class: |
H03H 7/383 20130101;
H04B 1/0458 20130101 |
Class at
Publication: |
333/032 |
International
Class: |
H03H 7/38 20060101
H03H007/38 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 2005 |
JP |
2005-148621 |
Claims
1. A matching circuit making the impedance at predetermined plural
frequencies match with an element whose impedance has
frequency-dependent characteristics, comprising: a first matching
block connected at one end to a first terminal to which said
element whose impedance has frequency-dependent characteristics is
connected; one or more second matching blocks consisting of lumped
elements and connected in series to said first matching block; one
or more switch elements; and one or more auxiliary matching blocks
connected to said second matching block(s) via said switch
element(s).
2. The matching circuit according to claim 1, comprising: N L-type
circuits each consisting of one said second matching block and a
series circuit of one first said switch element (below referred to
as the "first switch element"), connected to one end of said second
matching block, and one first said auxiliary matching block (below
referred to as the "first auxiliary matching block"); and N shunt
circuit block parts, each consisting of a series circuit of one
second said switch element (below referred to as the "second switch
element") and one second said auxiliary matching block (below
referred to as the "second auxiliary matching block"); and wherein
N is an integer equal to or greater than 1, said N L-type circuits
have one end of the second matching block of the first L-type
circuit connected in series to said first matching block and one
end of the second matching block of the next-stage L-type circuit
connected to the other end of said second matching block, N said
shunt circuit block parts are connected to the other end of the
second matching block of the last-stage L-type circuit, and a
.pi.-type circuit is formed by a second auxiliary matching block
connected to one said second switch element made to conduct, a
first auxiliary matching block connected to one said first switch
element made to conduct, and the second matching blocks between
these.
3. The matching circuit according to claim 1, comprising N L-type
circuits each consisting of said second matching block and a series
circuit of said switch element, connected to one end of said second
matching block, and said auxiliary matching block; and a series
second matching block; wherein N being an integer equal to or
greater than 1, said N L-type circuits have one end of the second
matching block of the first L-type circuit connected in series to
said first matching block and one end of the second matching block
of the next-stage L-type circuit connected to the other end of said
second matching block, one end of said second matching block is
connected to the other end of the second matching block of the
last-stage L-type circuit; the other end of said second matching
block is connected to an element whose characteristics do not
depend on the frequency, and a T-type circuit is constituted by one
said series circuit, said switch element of which is taken to be in
a conducting state, and the second matching blocks on both sides
thereof.,
4. The matching circuit according to claim 2 or 3, wherein N equals
1.
5. The matching circuit according to any of claims 1 to 4, wherein
said second matching block is constituted by an L-type circuit
consisting of a series matching block and a series circuit of a
switch element, connected to said series matching block, and a
matching element.
6. A matching circuit, comprising: a first matching block connected
at one end to a first terminal to which an element whose impedance
has frequency-dependent characteristics is connected; and a
matching circuit part constituting a .pi.-type circuit by a second
matching block connected in series to said first matching block,
and switch element and auxiliary matching block series circuits
respectively connected to both ends of said second matching block;
and wherein said second matching block is constituted by lumped
elements.
7. A matching circuit, comprising: a first matching block connected
at one end to a first terminal to which an element whose impedance
has frequency-dependent characteristics is connected; and a
matching circuit part constituting a T-type circuit by a second
matching block connected at one end to said first matching block,
the next second matching block connected at one end to the other
end of said second matching block, a series circuit of a switch
element, connected between said second matching block and the next
second matching block, and an auxiliary matching block; and wherein
said second matching block and said series second matching block
are constituted by lumped elements.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention pertains to a matching circuit handling
multiple bands which, in a plurality of frequency bands,
establishes matching between circuits having different impedances.
It pertains to matching circuits built into small-sized multiband
power amplifiers which amplify, with high efficiency, signals in a
plurality of frequency bands used e.g. in mobile communications and
satellite communications.
[0003] 2. Description of Related Art
[0004] Accompanying the diversification of services offered by
means of radio communications, conversion to multiband capability
for processing signals in a plurality of frequency bands is
required of radio equipment. As an indispensable device included in
radio equipment, there is the power amplifier. In order to carry
out efficient amplification, there is a need to obtain impedance
matching between the amplification element and its peripheral
circuits, so a matching circuit is used. As an example of a
conventional multiband power amplifier, technology as shown in
Reference 1 (NTT DoCoMo Technical Journal, Vol. 10, No. 1: "Mobile
Handsets") is disclosed.
[0005] The configuration of the 800 MHz/2 GHz band power amplifier
shown in Reference 1 is shown in FIG. 1, and the operation thereof
will be explained. The transmitted signal coming from the
transmitter is input into the single pole terminal of an input
switch 150, a Single Pole Double Throw (SPDT) switch. Next, the
transmitted signal, by being switched by input switch 150, is input
into an 800 MHz band amplifier 151 connected to a double throw
terminal of input switch 150, or a 2 GHz band amplifier 152. The
output signals of 800 MHz band amplifier 151 and 2 GHz band
amplifier 152 are switched by an output switch 153, a Single Pole
Double Throw switch, and supplied to an antenna.
[0006] In FIG. 2, the configuration of 800 MHz band amplifier 151
and 2 GHz band amplifier 152 is shown. Each amplifier is configured
with a series connection of an input matching circuit 160, an
amplification element 161, and an output matching circuit 162.
Input matching circuit 160 obtains matching between a signal source
163, whose output impedance does not depend on the frequency, and
amplification element 161. Output matching circuit 162 obtains
matching between the output impedance of amplification element 161
and a load 164.
[0007] Since the input impedance of amplification element 161
constituting each amplifier varies with frequency, input matching
circuit 160 and output matching circuit 162 are different depending
on the operation frequencies, even if the same amplification
element 161 is used. Accordingly, as shown in FIG. 1, separate
amplifiers 151, 152 handling each frequency band have been
necessary. Consequently, there has been the problem that the total
circuit area of the transmitter became larger as the operating
frequency bands rose.
[0008] In order not to increase the circuit area of an amplifier,
the method of designing matching circuits for wideband operation
can also be considered. However, compared to matching circuits
designed for narrowband operation, the result is that there occurs
a reduction in gain and efficiency. Accordingly, with respect to
these problems, the applicant of the present application first
proposed, in Reference 2 (International Publication No. WO
2004/082138 Pamphlet), a matching circuit which can handle the
conversion to multiband capability. The input matching circuit of
the amplifier disclosed in Reference 2 is shown in FIG. 3. E.g.,
the FET (Field Effect Transistor) input impedance can be expressed
as a load 170 (impedance Z.sub.L(f)) having frequency-dependent
characteristics. A first terminal P1 to which this load 170 is
connected has a main matching block 171 connected to it. The other
end (point A) of main matching block 171 is connected to one end of
a delay circuit 172 having a certain reactance value. The other end
(point B) of delay circuit 172 is connected to a signal source 173
having an impedance Z0 (below, the impedance not changing with
frequency is called Z0).
[0009] Main matching block 171 is designed to match the impedance
Z.sub.L(f1) of load 170 with the impedance Z0 of signal source 173,
in frequency band f1. In other words, main matching block 171
becomes a matching circuit with respect to frequency f1. Delay
circuit 172 is constituted by a distributed-parameter element, the
characteristic impedance of which is given, as is well known, by
the relationship shown in Eq. 1. Z0= {square root over (L/C)}
(1)
[0010] Here, L is the inductance of the distributed-parameter
element and C is the capacitance of the distributed-parameter
element. Consequently, by taking the characteristic impedance of
delay circuit 172 to be Z0, matching is obtained in frequency band
f1 between signal source 173 and load 170.
[0011] When operating in a frequency band f2, different from
frequency band f1 (e.g. when frequency band f2 is lower than
frequency band f1), the impedance of load 170 changes to
Z.sub.L(f2). Also, since main matching block 171 is a matching
circuit with respect to frequency f1, matching between signal
source 173 and load 170 is not obtained at frequency f2.
Accordingly, an auxiliary matching block 175 is connected via
switch element 174 to point B. And then, when operating in
frequency band f2, switch element 174 is taken to be in a
conducting state. By choosing a configuration like this, it is
possible, whichever is the value of the impedance estimated from
point A toward the side of load 170, to make the impedance Z0, seen
from point B toward the side of delay circuit 172. Here, the delay
value of delay circuit 172 is set to the delay value required to
match at point B in frequency band f2.
[0012] With the same approach as for the matching circuit shown in
FIG. 3, an example where the number of frequency bands which can be
handled has been increased to three is shown in FIG. 4. By the fact
that the number of frequency bands has increased from two to three,
the system increases by one additional set, the set of delay
circuit 180, switch element 181, and auxiliary matching block 182.
In a third frequency band f3, the impedance Z.sub.L(f3) of load 170
is regulated by means of delay circuit 180 and auxiliary matching
block 182 so that the impedance seen from point C toward the side
of delay circuit 180 becomes Z0. Further, since the characteristic
impedances of the delay circuits are fixed and do not depend on the
frequency, it is possible to obtain matching between signal source
173 and load 170 in each frequency band if switch element 174 and
switch element 181 are chosen to be in a non-conducting state in
the case of frequency band f1, switch element 174 is chosen to be
in a conducting state for in the case of frequency band f2, and
switch element 181 is chosen to be in a conducting state in the
case of frequency band f3.
[0013] In this way, by providing auxiliary matching blocks
connected via switch elements between the delay circuits along with
connecting in series in multiple stages delay circuits whose
impedances do not vary with frequency, there is implemented a
matching circuit capable of matching with respect to a plurality of
frequency bands. Further, the delay value required in frequency
band f3 can be considered to be the sum of the values for delay
circuit 172 and delay circuit 180.
[0014] As for delay circuits 172 and 180, it is realistic to choose
them to be transmission lines which are distributed parameter
networks. However, particularly in cases where the frequency is
low, transmission lines become comparatively large components
inside the circuit. E.g., if load 170 is taken to be a FET and in
case an amplifier for the 1 GHz band is designed, a 50.OMEGA.
transmission line has a width of 0.63 mm and a length of 9.22 mm,
so the result is a component having a length of about 10 mm.
[0015] In the technology shown in the aforementioned Reference 2,
the delay circuits are realistically constituted by transmission
lines. However, in the case of transmission lines, the length
easily becomes comparatively long. In particular, in the case where
the used frequency is low, the area of a transmission line serving
as a delay circuit becomes large, so there has been the problem
that the matching circuit as a whole also was made bigger. Further,
this problem increases as the frequency becomes lower, and as the
number of frequencies rises.
BRIEF SUMMARY OF THE INVENTION
[0016] The matching circuit of the present invention has a first
matching block, connected at one end to a load having an impedance
with frequency-dependent characteristics and a second matching
block formed by a lumped-parameter element connected in series to
the first matching block. E.g., the second matching block matches
the impedances of the signal source and the load in the lowest
frequency band. Moreover, for the purpose of impedance matching in
high frequency bands, it has a .pi.-type circuit. A .pi.-type
circuit is a circuit in which respective switch elements and
auxiliary matching blocks are connected to both ends of the second
matching block.
[0017] According to a configuration like this, the matching
conditions in the aforementioned low frequency band can be created
by a series connection of the first matching block and the second
matching block. Further, in the case of a high frequency band, by
setting an appropriate value for the .pi.-type circuit, it is
possible to choose the impedance of the .pi.-type circuit to be Z0
and to choose the impedance of the second matching block to be one
with no influence for the high frequency band. Moreover, since the
second matching block is constituted by lumped elements, it is
possible to make the matching circuit smaller-sized than the
conventional matching circuit constituted by transmission
lines.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a diagram showing the configuration of a
conventional 800 MHz/2 GHz band power amplifier
[0019] FIG. 2 is a diagram showing the configuration of each power
amplifier in FIG. 1.
[0020] FIG. 3 is a diagram showing a conventional matching
circuit.
[0021] FIG. 4 is a diagram showing an example where the number of
frequency bands which can be handled by the conventional matching
circuit has been taken to be three.
[0022] FIG. 5 is a diagram showing the base configuration of a
matching circuit of this invention.
[0023] FIG. 6A is a diagram explaining the operation in a low
frequency band f2.
[0024] FIG. 6B is a diagram explaining the operation in a high
frequency band f1.
[0025] FIG. 7 is a diagram showing the configuration where the
.pi.-type circuit of a matching circuit of this invention, shown in
FIG. 5, has been replaced with a T-type circuit.
[0026] FIG. 8 is a diagram where the matching circuit of the
present invention, shown in FIG. 5, has been generalized so that it
can be adapted to a plurality of frequency bands.
[0027] FIG. 9 is a diagram showing the image of N frequency
bands.
[0028] FIG. 10 is a diagram showing an embodiment of a matching
circuit using two T-type circuits.
[0029] FIG. 11 is a diagram where a matching circuit of the present
invention, using T-type matching circuits, has been generalized so
that it can be adapted to a plurality of frequency bands.
[0030] FIG. 12 is a diagram showing another configuration example
of a matching circuit of the present invention using T-type
matching circuits.
[0031] FIG. 13 is a diagram showing a configuration example of a
matching circuit of the present invention, using T-type matching
circuits where auxiliary matching blocks have been connected in
series.
[0032] FIG. 14 is a diagram showing an example where the second
matching block of FIG. 5 is configured with an L-type circuit.
[0033] FIG. 15 is a diagram showing the configuration of the second
matching block using a T-type circuit.
[0034] FIG. 16 is a diagram showing another configuration of the
second matching block using a T-type circuit.
[0035] FIG. 17 is a diagram showing an example where the first
matching block has been configured with a plurality of
elements.
[0036] FIG. 18 is a diagram showing an example where a matching
circuit of this invention has been applied to an amplification
circuit.
[0037] FIG. 19A is a diagram showing the simulation results in the
case of a setting for the 2 GHz band, with the configuration of
FIG. 18.
[0038] FIG. 19B is a diagram showing the simulation results in the
case of a setting for the 1 GHz band, with the configuration of
FIG. 18.
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
[0039] In FIG. 5, the basic configuration of a matching circuit of
the present invention is shown. The matching circuit of the present
invention is constituted by a first matching block 2 and a matching
circuit part 8 consisting of lumped elements. Matching circuit part
8 is a .pi.-type circuit constituted by a second matching block 3,
switch elements 4 and 5, and auxiliary matching blocks 6 and 7. One
end of first matching block 2 is connected to a first terminal P1
to which an element 1 (a load in this example) having an impedance
Z.sub.L(f) with frequency-dependent characteristics is connected.
To the other end of first matching block 2, one end of second
matching block 3 is connected in series. The other end of second
matching block 3 is connected, via a second terminal P2, to an
element 9, e.g. a signal source, with an impedance Z0 whose
impedance does not depend on the frequency. Also, to the terminal
on the first matching block 2 side of second matching block 3,
there is connected a series circuit of switch element 4 and
auxiliary matching block 6. To the other end of second matching
block 3, there is connected a series circuit of switch element 5
and auxiliary matching block 7. By being connected in this way,
matching circuit part 8 becomes a .pi.-type circuit.
[0040] The operation of the matching circuit in FIG. 5 will be
explained using FIG. 6A and FIG. 6B. FIG. 6A is a diagram showing
the operation in a low frequency band f2. FIG. 6B is a diagram
showing the operation in a high frequency band f1. In the case of
frequency band f2, switch elements 4 and 5 of FIG. 5 are
non-conducting. Consequently, in the case of frequency band f2,
impedance Z2 of the second matching block is set so that the sum
Z.sub.A of impedance Z.sub.L(f2) of element 1 in the frequency band
f2, impedance Z1 of first matching block 2, and impedance Z2 of
second matching block 3 (below, the impedances will be omitted in
portions where the same can be considered not to be particularly
necessary) becomes Z0. As a result, the impedances are matched at
second terminal P2.
[0041] In the frequency band f1, switch elements 4 and 5 in FIG. 5
are in a conducting state. Consequently, as shown in FIG. 6B,
matching circuit 8 becomes a .pi.-type circuit in which auxiliary
matching blocks 6 and 7 are respectively connected to both ends of
second matching block 3. Here, since first matching block 2 is a
matching circuit for the frequency band f1, impedance matching is
obtained with impedance Z0 of element 9 at point A at frequency f1.
Accordingly, by making a design so that, in the frequency band f1,
the combined impedance Z.pi. seen from point A toward the second
terminal P2 side becomes identical to Z0 (Z0=Z.pi.), it is possible
to remove the influence of the impedance of second matching block 3
in the frequency band f1. Specifically, if the impedance of
auxiliary matching block 6 is taken to be Z3 and the impedance of
auxiliary matching block 7 is taken to be Z4, Z3 and Z4 may be
designed so that the condition shown in Eq. 2 is met.
Z.pi.=(Z0Z2Z3+Z4Z2Z3+Z0Z4Z3)/(Z0Z4+Z0Z2+Z0Z3+Z4Z2+Z1Z3) (2)
[0042] As was stated above, in the frequency band f1, it is first
matching block 2 which operates to match impedance Z.sub.L(f1) of
element 1 to impedance Z0 of element 9. Also, it is second matching
block 3 which operates to match the impedance Z.sub.L(f2) of
element 1, changed by the modification of the frequency band from
f1 to f2, to the impedance Z0 of element 9. Further, it is
auxiliary matching blocks 6 and 7 which operate to remove the
influence of second matching block 3 which is a hindrance in
frequency band f1.
[0043] Matching circuit part 8 in FIG. 5 can also be configured
with a T-type circuit. An example where the matching circuit part
has been configured with a T-type circuit is shown in FIG. 7. In
FIG. 7, second matching block 3 in FIG. 5 is replaced by a second
matching block 31 and a series second matching block 32. One end of
second matching block 31 is connected to point A. The other end of
second matching block 31 is connected to one end of series second
matching block 32. The other end of series second matching block 32
is connected to second terminal P2. To the connection point of
second matching block 31 and series second matching block 32, there
is connected an auxiliary matching block 34 via a switching element
33.
[0044] The relationship between FIG. 5 and FIG. 7 cannot be
converted with the well known Y-.DELTA. conversion (T-.pi.
conversion) relationship. In order to adopt a matching circuit
equivalent to that of FIG. 5, first, the value of the impedance of
second matching block 3 must be Z2 as a condition in frequency band
f2. Consequently, if the impedance of second matching block 31 is
taken to be Za and the impedance of series second matching block 32
is taken to be Zb, the relationship Z2=Za+Zb must be satisfied. In
order to choose a T-type circuit which is equivalent to a .pi.-type
circuit, the impedance value of auxiliary matching block 34 may be
designed by adding this condition. Of course, it goes without
saying that matching block part 8 may be designed with a T-type
circuit from the beginning. In this way, it is possible for
matching circuit part 8 to have a configuration which is not
limited to a .pi.-type circuit but can also be a T-type
circuit.
Embodiment 2
[0045] FIG. 8 is an example where the basic structure of this
invention, shown in FIG. 5, has been generalized so that it can be
adapted to a plurality of frequency bands. This matching circuit is
composed of first matching block 2, L-type blocks 43a to 43n, and
shunt circuit blocks 46a to 46n. Each L-type block 43i (i=a to n)
is composed of a second matching block 40i, a first switch element
41i, and a first auxiliary matching block 42i. One terminal of
second matching block 40a is connected to first matching block 2.
Also, the other end of second matching block 40a is connected to
one terminal of second matching block 40b. In this way, each second
matching block 40i is connected in series. First auxiliary matching
block 42i is connected, via first switch element 41i, to the
terminal of second matching block 40i on the side of first terminal
P1. In other words, an L-type circuit is formed by means of second
matching block 40i, first switch element 41i, and first auxiliary
matching block 42i.
[0046] To the second terminal P2 side of L-type block 43n, there
are connected in parallel shunt circuit blocks 46a to 46n. Each
shunt circuit block 46i (i=a to n) is composed of a second switch
element 44i connected in series and a second auxiliary matching
block 45i.
[0047] Below, an explanation will be given on the operation and
design method of a matching circuit in which three L-type blocks
43a to 43c and three shunt circuit blocks 46a to 46c are
connected.
[0048] First, an explanation will be given for the case of
frequency band f4. In the case of frequency band f4, first switch
elements 41a to 41c and second switch elements 44a to 44c are all
in a non-conducting state. Element 1 (impedance Z.sub.L(f4)) is
connected, via three second matching blocks 40a to 40c connected in
series, to element 9 (impedance Z0). Here, the impedance Z.sub.L(f)
of element 1 changes with frequency. Also, element 9 is a signal
source or the like, the impedance of which does not depend on the
frequency. Here, second matching block 40c is designed so that the
combined impedance of element 1, first matching block 2, and second
matching blocks 40a and 40b is converted to Z0. If second matching
block 40c is designed in this way, the impedance Z0 is matched at
the second terminal P2 side end of second matching block 40c.
[0049] In the case of frequency band f3, switch element 41c of
L-type block 43c and second switch element 44a of shunt circuit
block 46a are chosen to be in a conducting state. In this case,
since first auxiliary matching block 42c and second auxiliary
matching block 45a are connected to both ends of second matching
block 40c, a .pi.-type circuit is configured. Here, second matching
block 40b is designed so that the combined impedance due to element
1 (impedance Z.sub.L(f3)), first matching block 2, and second
matching block 40a is matched to Z0. If second matching block 40b
is designed in this way, the impedance seen from the second
terminal P2 side of second matching block 40b (the first terminal
P1 side of second matching block 40c) toward element 1 becomes Z0.
Also, first auxiliary matching block 42c and second auxiliary
matching block 45a are designed so that Eq. 2 is satisfied at
frequency f3. By designing in that way, the impedance seen from the
first terminal P1 side of second matching block 40c (the second
terminal P2 side of second matching block 40b) toward element 9
also becomes Z0. In other words, it is possible to remove the
influence of the impedance of second matching block 40c, so the
impedances are matched.
[0050] In the case of frequency band f2, switch element 41b of
L-type block 43b and second switch element 44b of shunt circuit
block 46b are chosen to be in a conducting state. In this case,
since first auxiliary matching block 42b and second auxiliary
matching block 45b are connected to both ends, connected in series,
of second matching block 40c and second matching block 40b, a
.pi.-type circuit is configured. Second matching block 40a is
designed so that the combined impedance due to element 1 (impedance
Z.sub.L(f2)) and first matching block 2 is matched to Z0. If second
matching block 40a is designed in this way, the impedance seen from
the second terminal P2 side of second matching block 40a (the first
terminal P1 side of second matching block 40b) toward element 1
becomes Z0. Also, first auxiliary matching block 42b and second
auxiliary matching block 45b are designed so that Eq. 2 is
satisfied at frequency f2. By designing in that way, the impedance
seen from the first terminal P1 side of second matching block 40b
(the second terminal P2 side of second matching block 40a) toward
element 9 also becomes Z0. In other words, it is possible to remove
the influence of second matching blocks 40b and 40c, so the
impedances are matched.
[0051] In the case of frequency band f1, switch element 41a of
L-type block 43a and second switch element 44c of shunt circuit
block 46c are in a conducting state. In this case, since first
auxiliary matching block 42a and second auxiliary matching block
45c are connected to both ends of second matching blocks 40c to
40a, a .pi.-type circuit is configured. First matching block 2 is
designed so that impedance Z.sub.L(f1) of element 1 is matched to
Z0. If first matching block 2 is designed in this way, the
impedance seen from the second terminal P2 side of first matching
block 2 (the first terminal P1 side of second matching block 40a)
toward element 1 becomes Z0. Also, first auxiliary matching block
42a and second auxiliary matching block 45c are designed so that
Eq. 2 is satisfied at frequency f1. By designing in that way, the
impedance seen from the first terminal P1 side of second matching
block 40a (the second terminal P2 side of first matching block 2)
toward element 9 also becomes Z0. In other words, it is possible to
remove the influence of the impedances of second matching blocks
40a to 40c, so the impedances are matched.
[0052] As stated above, it is possible to combine three L-type
blocks and shunt circuits to match the impedances at four
frequencies. If this is generalized, the result is that it is
possible, with a combination of N L-type blocks and shunt circuits,
to match the impedances in N+1 frequency bands.
[0053] FIG. 9 expresses the image of N frequency bands. The
abscissa axis of FIG. 9 is the frequency and the ordinate axis is
the power of transmission. In this diagram, a relation that the
frequency becomes lower as N increases is shown as an example.
[0054] Further, in FIG. 8, the frequencies are arranged in the
order corresponding to shunt circuit blocks 46a to 46n. However, as
long as a one-to-one relationship with first auxiliary matching
blocks 42a to 42n is satisfied, the order of arranging shunt
circuit blocks 46a to 46n is indifferent.
[0055] Also, the second matching block is configured with lumped
elements connected in series between the conductively connected
first switch element and second switch element. Consequently, even
if the number of second matching blocks becomes large, it is
possible to make the whole circuit remarkably small, compared to
the case of a configuration with transmission lines.
Embodiment 3
[0056] A matching circuit generalized by using .pi.-type circuits
was explained in FIG. 8, but it is also possible to configure a
generalized matching circuit using T-type circuits. In FIG. 10,
there is shown an embodiment of a matching circuit using two T-type
circuits. This matching circuit is composed of first matching block
2, an L-type block part 63a, an L-type block part 63b, and a second
matching block 60c. One end of first matching block 2 is connected
to a first terminal P1 at which it is connected to element 1. Also,
the other end of first matching block 2 is connected to one end of
a second matching block 60a inside L-type block part 63a. To the
other end of second matching block 60a, there is connected an
auxiliary matching block 62a via a first switch element 61a.
Moreover, the other end of second matching block 60a is also
connected to one end of a second matching block 60b inside L-type
block part 63b. To the other end of second matching block 60b, an
auxiliary matching block 62b is connected via a second switch
element 61b. In addition, the other end of second matching block
60b is also connected to one end of second matching block 60c.
Here, L-type block part 63a is composed of second matching block
60a, first switch element 61a, and auxiliary matching block 62a.
Also, L-type block part 63b is composed of second matching block
60b, second switch element 61b, and auxiliary matching block 62b.
Also, T-type matching circuits 64 and 65 are composed of two L-type
block parts 63a and 63b and one second matching block 60c. T-type
matching circuit 64 is composed of second matching blocks 60a and
60b, first switch element 61a, and auxiliary block 62a. Also,
T-type matching circuit 65 is composed of second matching blocks
60c and 60b, second switch element 61b, and auxiliary matching
block 62b. In this way, a matching circuit which matches impedances
in three frequency bands is configured in two stages with T-type
matching circuits 64 and 65.
[0057] In the case of frequency band f3, switch elements 61a and
61b are chosen to be in a non-conducting state. The impedance of
element 1 changes with the frequency band. Element 1 with an
impedance Z.sub.L(f3) is connected, via the serially connected
first matching block 2 and second matching blocks 60a, 60b, and
60c, to element 9 which has an impedance of Z0.
[0058] Second matching block 60b and second matching block 60c are
designed so that the combined impedance with element 1, first
matching block 2, and second matching block 60a becomes Z0. By
designing second matching block 60b and second matching block 60c
in this way, it is possible to match the impedances at second
terminal P2 of second matching block 60c.
[0059] In the case of frequency band f2, switch element 61b
constituting T-type matching circuit 65 is in a conducting state.
Second matching block 60a is designed so that the combined
impedance with element 1, having an impedance Z.sub.L(f.sup.2), and
first matching block 2 is taken to be Z0. By designing second
matching block 60a in this way, the impedance seen from point D
toward element 1 becomes Z0. Also, auxiliary matching block 62b is
designed so that the combined impedance of second matching blocks
60b and 60c, auxiliary matching block 62b, and element 9 becomes
Z0. If auxiliary matching block 62b is designed in this way, the
impedance seen from point D toward the element 9 side becomes Z0.
Consequently, it is possible to match the impedances at point D.
Also, even on the side of second terminal P2, the impedance seen
toward element 1 is Z0. Consequently, the combined impedance of
second matching blocks 60c and 60b and auxiliary matching block 62b
does not exert any influence on the matching condition. In other
words, auxiliary matching block 62b removes the influence of second
matching blocks 60c and 60b at frequency f2.
[0060] In the case of frequency band f1, switch element 61b
constituting T-type matching circuit 65 is in a non-conducting
state, and switch element 61a constituting T-type matching circuit
64 is in a conducting state. First matching block 2 is designed so
that the the combined impedance with impedance Z.sub.L(f1) of
element 1 becomes Z0. By designing first matching block 2 in this
way, the impedance seen from point A toward element 1 becomes Z0.
Next, first auxiliary matching block 62a is designed so that the
combined impedance of second matching blocks 60a, 60b, and 60c,
auxiliary matching block 62a, and element 9 becomes Z0. By
designing first auxiliary matching block 62a in this way, the
impedance seen from point A toward element 9 becomes Z0.
Consequently, it is possible to obtain matching of the impedances
at point A. Also, on the second terminal P2 side as well, the
impedance seen toward element 1 is Z0. Consequently, the combined
impedance of second matching blocks 60a, 60b, 60c and auxiliary
matching block 62a does not exert influence any more on the
matching conditions. In other words, auxiliary matching block 62a
removes the influence of second matching blocks 60a, 60b, 60c at
the frequency f1.
[0061] With the aforementioned explanation, the case where switch
element 61b is non-conducting was explained. However, it is not
mandatory to take switch element 61b to be non-conducting. In case
switch element 61b is taken to be conducting when the frequency
band is f1, auxiliary matching block 62a may be designed with that
assumption.
[0062] In this way, it is possible to configure a matching circuit
handling three frequency bands by means of two T-type matching
circuits 64 and 65.
Embodiment 4
[0063] An example showing a generalization of the T-type matching
circuit explained in Embodiment 3 is shown in FIG. 11. The
configuration up to the second-stage L-type block 63b seen from
first matching block 2 is identical to that of FIG. 10. On the
second terminal P2 side of second-stage L-type block 63b, L-type
blocks are added. In FIG. 11, a total of N L-type blocks 63a to 63n
are connected. To the other end of L-type block 63n, one end of
series second matching block 70 is connected, the other end of
series second matching block 70 being connected to second terminal
P2. N is an integer equal to or greater than 1. The matching
circuit shown in FIG. 11 is a subordinate connection configuration
of N T-type matching circuits and is capable of matching in N+1
frequency bands. The operation is the same as in FIG. 10.
Embodiment 5
[0064] Another T-type matching circuit embodiment is shown in FIG.
12. In FIG. 10, a T-type circuit was formed using second matching
blocks of adjacent L-type blocks. FIG. 12 is an example in which a
plurality of auxiliary matching blocks are connected, via switch
elements, between two second matching blocks connected in series.
This matching circuit is composed of first matching block 2 and
T-type matching circuits 83a, 83b, and 83c. T-type matching circuit
83a is composed of second matching blocks 80a and 80b, a switch
element 81a, and an auxiliary matching block 82a. One end of second
matching block 80a is connected to first matching block 2. The
other end of second matching block 80a is connected to one end of
second matching block 80b. Also, auxiliary matching block 82a is
connected, via switch element 81a, between second matching block
80a and second matching block 80b. By this kind of connection
relationship, second matching blocks 80a and 80b, switch element
81a, and auxiliary matching block 82a make up a T-type circuit.
T-type matching circuit 83b is composed of second matching blocks
80c and 80d, a switching element 81b, and an auxiliary matching
block 82b. T-type matching circuit 83c is composed of second
matching blocks 80c and 80d, a second switching element 84, and an
auxiliary matching block 85. Here, second matching blocks 80c and
80d are constituent parts of both T-type matching circuit 83b and
T-type matching circuit 83c. With this configuration, auxiliary
matching block 82b is connected, via switch element 81b, to the
connection point of second matching block 80c and second matching
block 80d. Moreover, auxiliary matching block 85 is also connected,
via second switch element 84, to the connection point of second
matching block 80c and second matching block 80d. One end of second
matching block 80c is connected to second matching block 80b. Also,
the other end of second matching block 80d is connected to the
second terminal P2 to which element 9 is connected.
[0065] As stated above, a T-type matching circuit may be connected
in multiple stages between element 1 and element 9. The present
embodiment is capable of matching in three frequency bands by means
of three T-type matching circuits.
[0066] In the case of frequency band f3, switch elements 81a and
81b and second switch element 84 are non-conducting. Second
matching blocks 80c and 80d are designed so that the combined
impedance with element 1 (impedance Z.sub.L(f3)), first matching
block 2, and second matching blocks 80a, 80b is made to match the
impedance Z0 of element 9 in the frequency band f3. Consequently,
impedance matching can be obtained at second terminal P2.
[0067] In the case of frequency band f2, it is only switch element
81b forming T-type matching circuit 83b that is conducting. Second
matching blocks 80a and 80b are designed so that the combined
impedance of element 1 (impedance Z.sub.L(f.sup.2)) and first
matching block 2 is made to match the impedance Z0 of element 9 in
the frequency band f2. Consequently, the impedance seen from the
second terminal P2 side of second matching block 80b (the first
terminal P1 side of second matching block 80c) toward element 1
becomes Z0. Also, auxiliary matching block 82b is designed so that
the combined impedance of second matching blocks 80c and 80d,
auxiliary matching block 82b, and element 9 becomes Z0 at the
frequency f2. By designing auxiliary matching block 82b in this
way, the impedance seen from the first terminal P1 side of second
matching block 80c (the second terminal P2 side of second matching
block 80b) toward element 9 becomes Z0 at the frequency f2.
Consequently, the impedances are matched.
[0068] In the case of frequency band f1, switch element 81a and
second switch element 84 are conducting. First matching block 2 is
designed so that the impedance of element 1 (impedance Z.sub.L(f2))
is made to match the impedance Z0 of element 9 in the frequency
band f1. Consequently, the impedance seen from the second terminal
P2 side of first matching block 2 toward element 1 becomes Z0.
Auxiliary matching block 82a and 85 are designed so that, in the
frequency band f1, the combined impedance of second matching blocks
80a, 80b, 80c and 80d, auxiliary matching block 82a, and element 9
becomes Z0. Consequently, the impedance seen from the second
terminal P2 side of first matching block 2 (the first terminal P1
side of second matching block 80a) toward element 9 becomes Z0.
[0069] In this way, in the case of connecting T-type matching
circuits, the two second matching blocks and the auxiliary matching
block only make up a set with respect to one frequency band. In
order to make the second matching blocks handle a plurality of
frequency bands, a plurality of auxiliary matching blocks becomes
necessary.
Embodiment 6
[0070] As explained in Embodiment 5, in the case of connecting
T-type matching circuits, there are cases in which, for two second
matching blocks, a plurality of auxiliary matching blocks becomes
necessary. In FIG. 13, there is shown a configuration example of a
matching circuit using an additional auxiliary matching block. FIG.
13 shows a configuration example where a second switch element 90
and a second auxiliary matching block 91 have been connected in
series with auxiliary matching block 82b of FIG. 12. Having
auxiliary matching blocks connected in series in two stages is done
so that second matching blocks 80c and 80d constituting T-type
matching circuit 83b can handle two frequency bands.
[0071] In the case of this example, in order for the circuit to
function also in the case where only switch 81b is conducting, it
is necessary to choose auxiliary matching block 82b to be a
transmission line. In case it is not desired to provide such
conditions, switch element 81b may be configured with a Single Pole
Double Throw (SPDT) switch or a multi-contact switch, and switching
may be performed between auxiliary matching blocks with different
values.
[0072] If the circuit configuration is such that the impedance of
the second matching block inserted between element 1 and element 9
can be made Z0, seen from both the aforementioned matching point
and the element 9 directions, the invention is not limited to the T
type or the .pi. type.
Embodiment 7
[0073] In the explanations so far, the second matching blocks were
explained as black boxes. In FIG. 14, there is shown a
configuration example of second matching block 3 of FIG. 5. Second
matching block 3 is constituted by an L-type circuit consisting of
a series matching block 100, a switch element 101 for matching, and
a matching element 102. One end of series matching block 100 is
connected to first matching block 2. Matching element 102 is
connected to the other end of series matching block 100 via switch
element 101 for matching.
[0074] In the case of frequency band f1, switch elements 4 and 5
are in a non-conducting state, and only switch element 101 for
matching is conducting. At this point, the sum of the impedances of
element 1 and first matching block 2 are matched to impedance Z0 of
element 9 by means of series matching block 100 and matching
element 102.
[0075] In the case of frequency band f2, switch elements 4 and 5
are made to conduct and switch element 101 for matching is chosen
to be non-conducting. As for this configuration, it is possible, by
the existence of matching element 102, to broaden the options of
second matching block 3 and auxiliary matching block 6 and 7. In
other words, it is possible to increase the freedom in designing
second matching block 3 by configuring second matching block 3 with
series matching block 100, first switch element 101 for matching,
and matching element 102. In general, the values of the lumped
elements constituting second matching block 3 are discrete, making
delicate tuning difficult. However, according to this embodiment,
it is possible to broaden the lumped element options.
Embodiment 8
[0076] Another configuration of the second matching block is shown
in FIG. 15. Second matching block 3 in FIG. 15 is constituted by a
T-type circuit consisting of second matching blocks 60a and 60b, a
switch element 110 for matching, and a matching element 111. Second
matching block 60a and second matching block 60b are connected in
series. One end of second matching block 60a is connected to first
matching block 2. The other end of second matching block 60b is
connected to second terminal P2. Matching element 111 is connected,
via switch element 110 for matching, to the connection point of
second matching block 60a and second matching block 60b.
[0077] Switch element 110 for matching and matching element 111 are
provided in order to increase the freedom in designing the second
matching blocks and auxiliary matching block 7 and auxiliary
matching block 6. Regarding the function, it is the same as in
Embodiment 7.
Embodiment 9
[0078] Another configuration of the second matching blocks is shown
in FIG. 16. FIG. 16 differs from FIG. 7 in the point that, on the
second terminal P2 side of T-type matching circuit part 30, there
are provided a switch element 120 form matching and a matching
element 121. In the case of frequency f2, switch element 33 and
switch element 120 for matching are e.g. made to conduct
exclusively. Matching element 121 and second matching block 31 and
32 are designed so that the combined impedance with element 1 and
first matching block 2 is chosen to be Z0. By configuring the
circuit in this way, it is possible to increase the freedom in
designing the second matching blocks.
Embodiment 10
[0079] In the same way as configuring second matching block 3 by
using a plurality of elements, first matching block 2 may also be
configured with a plurality of elements. A configuration example
thereof is shown in FIG. 17. In this example, first matching block
2 is composed of a first series matching block 130 and an auxiliary
matching block 131 connected to one end thereof. Further, auxiliary
matching block 131 may be connected to either end of first series
matching block 130. First series matching block 130 is connected to
element 9 via matching circuit part 8.
[0080] As for the configuration of the first matching block, modes
other than this are possible. All things considered, in a
predetermined frequency band f, if the impedance seen from point A
toward element 1 (impedance Z.sub.L(f)) can be chosen to be Z0, any
circuit configuration is acceptable.
Application Example
[0081] An exemplification of the matching circuit which has been
gradually explained this far is shown in FIG. 18. FIG. 18 is an
example applied to an amplifying circuit operating in two frequency
bands, the 2 GHz band and the 1 GHz band. On the input side of an
FET 140, which is a power amplifier element, the matching circuit
shown in FIG. 17 is connected, and on the input side, the matching
circuit shown in FIG. 16 is connected. As for the matching circuit
on the input side, first matching block 2 has become a first
matching block 141. The output side matching circuit has, based on
the matching circuit shown in FIG. 16, first matching block 2
configured with a first matching block 142.
[0082] The operation has been explained this far, so an explanation
thereof will be omitted. In FIG. 19A and FIG. 19B, the simulation
results for the amplifier in FIG. 18 are shown. FIG. 19A is a
diagram showing the frequency characteristics in the case where the
circuit has been set for the 2 GHz band. The abscissa axis
indicates the frequency and the ordinate axis indicates the S
parameter. The reflection S.sub.11 of the signal input into first
terminal P1 gets attenuated abruptly at 2 GHz. The transmission
S.sub.21 of the signal input in first terminal P1 exhibits a value
of approximately 14 dB at 2 GHz, so the circuit transmits well.
FIG. 19B is a diagram showing the frequency characteristics in the
case where the circuit has been set for the 1 GHz band. The
reflection S.sub.11 of the signal input into first terminal P1 gets
attenuated abruptly at 1 GHz. The transmission S.sub.21 of the
signal input in first terminal P1 exhibits a value of approximately
19 dB at 1 GHz, so the circuit transmits well. It is seen that the
matching circuit according to the present invention functions as a
multiband matching circuit.
[0083] The matching circuit according to the present invention has
an impedance seen from both ends of a second matching block,
inserted between element 9 and element 1 and formed with
lumped-parameter elements, which is made to match the impedance Z0
by means of an auxiliary matching block. Also, by raising the
number of auxiliary matching blocks, a matching circuit handling a
plurality of frequency bands is adopted. Further, since the second
matching block is formed with lumped elements, it can be made
smaller than prior-art matching circuits configured with
transmission lines.
[0084] The effect of the reduction in size is possible to see by
comparing FIG. 3 showing a conventional matching circuit and FIG. 5
showing the matching circuit of the present invention. FIG. 3 and
FIG. 5 are diagrams of circuits made capable of matching in two
frequency bands together. As against the conventional matching
circuit (FIG. 3), the matching circuit of the present invention
(FIG. 5) requires in total two additional components, one switch
element and one auxiliary matching circuit. However, the delay
circuit 172 required in the conventional matching circuit is a
large-size component. The size thereof varies with the frequency
band and the used power amplification element, but when e.g., the
frequency band is taken to be 1 GHz with a certain amplification
element, the width is 0.63 mm and the length is 9.22 mm, or the
length is 15.32 mm.
[0085] On the other hand, the matching circuit of the present
invention can be configured with a chip circuit commonly known by
the name 0603 and having a width of 0.3 mm and a length of 0.6 mm
and a Monolithic Microwave Integrated Circuit several mm square. In
other words, all of the components constituting the matching
circuit of the present invention end up amply fitting into the
space of delay circuit 172. In order to handle still more frequency
bands, the number of delay circuits 172 must be increased.
Consequently, as a matching circuit for multiband use, the matching
circuit of the present invention can be further reduced in size,
compared to a conventional matching circuit.
* * * * *