U.S. patent application number 13/182444 was filed with the patent office on 2013-01-17 for signal modulator and signal modulating method.
The applicant listed for this patent is Chih-Hao Sun, Chi-Yao Yu. Invention is credited to Chih-Hao Sun, Chi-Yao Yu.
Application Number | 20130016796 13/182444 |
Document ID | / |
Family ID | 47483972 |
Filed Date | 2013-01-17 |
United States Patent
Application |
20130016796 |
Kind Code |
A1 |
Sun; Chih-Hao ; et
al. |
January 17, 2013 |
SIGNAL MODULATOR AND SIGNAL MODULATING METHOD
Abstract
A signal modulator includes: a modulating circuit; a first
signal trace block arranged to conduct a first in-phase oscillating
signal to the modulating circuit, and conduct a first
quadrature-phase oscillating signal to the modulating circuit; and
a second signal trace block arranged to conduct a second in-phase
oscillating signal to the modulating circuit, and conduct a second
quadrature-phase oscillating signal to the modulating circuit, and
a phase difference caused by the first signal trace block
substantially equals a phase difference caused by the second signal
trace block.
Inventors: |
Sun; Chih-Hao; (New Taipei
City, TW) ; Yu; Chi-Yao; (Hsinchu County,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sun; Chih-Hao
Yu; Chi-Yao |
New Taipei City
Hsinchu County |
|
TW
TW |
|
|
Family ID: |
47483972 |
Appl. No.: |
13/182444 |
Filed: |
July 14, 2011 |
Current U.S.
Class: |
375/298 ;
332/144 |
Current CPC
Class: |
H04L 27/361 20130101;
H04L 27/2075 20130101 |
Class at
Publication: |
375/298 ;
332/144 |
International
Class: |
H04L 27/36 20060101
H04L027/36; H03C 3/02 20060101 H03C003/02 |
Claims
1. A signal modulator, comprising: a modulating circuit, arranged
to modulate a wireless communication signal according to a first
oscillating signal, a second oscillating signal, a third
oscillating signal, and a fourth oscillating signal; a first signal
trace block, arranged to conduct a first in-phase oscillating
signal having a first phase to the modulating circuit such that the
modulating circuit receives the first oscillating signal having a
second phase, and conduct a first quadrature-phase oscillating
signal having a third phase to the modulating circuit such that the
modulating circuit receives the second oscillating signal having a
fourth phase; and a second signal trace block, arranged to conduct
a second in-phase oscillating signal having a fifth phase to the
modulating circuit such that the modulating circuit receives the
third oscillating signal having a sixth phase, and conduct a second
quadrature-phase oscillating signal having a seventh phase to the
modulating circuit such that the modulating circuit receives the
fourth oscillating signal having an eighth phase; wherein a phase
difference between the first phase and the second phase
substantially equals a phase difference between the eighth phase
and the seventh phase, and a phase difference between the fourth
phase and the third phase substantially equals a phase difference
between the sixth phase and the fifth phase.
2. The signal modulator of claim 1, wherein a phase of the first
in-phase oscillating signal is the same as a phase of the second
in-phase oscillating signal, and a phase of the first
quadrature-phase oscillating signal is the same as a phase of the
second quadrature-phase oscillating signal.
3. The signal modulator of claim 1, wherein the first signal trace
block comprises: a first conducting circuit, arranged to conduct
the first in-phase oscillating signal to the modulating circuit;
and a second conducting circuit, arranged to conduct the first
quadrature-phase oscillating signal to the modulating circuit; and
the second signal trace block comprises: a third conducting
circuit, arranged to conduct the second in-phase oscillating signal
to the modulating circuit; and a fourth conducting circuit,
arranged to conduct the second quadrature-phase oscillating signal
to the modulating circuit; wherein one of the first conducting
circuit and the second conducting circuit and one of the third
conducting circuit and the fourth conducting circuit are symmetric
to each other.
4. The signal modulator of claim 3, wherein the first conducting
circuit and the fourth conducting circuit are bilaterally symmetric
to each other, and the second conducting circuit and the third
conducting circuit are bilaterally symmetric to each other.
5. The signal modulator of claim 1, wherein the first in-phase
oscillating signal, the first quadrature-phase oscillating signal,
the second in-phase oscillating signal, the second quadrature-phase
oscillating signal are differential oscillating signals each
comprising a positive oscillating signal and a negative oscillating
signal; the first signal trace block comprises: a first conducting
circuit, comprising a first conducting trace and a second
conducting trace arranged to conduct the positive oscillating
signal and the negative oscillating signal of the first in-phase
oscillating signal to the modulating circuit, respectively; a
second conducting circuit, comprising a third conducting trace and
a fourth conducting trace arranged to conduct the negative
oscillating signal and the positive oscillating signal of the first
quadrature-phase oscillating signal to the modulating circuit,
respectively; the second signal trace block comprises: a third
conducting circuit, comprising a fifth conducting trace and a sixth
conducting trace arranged to conduct the positive oscillating
signal and the negative oscillating signal of the second in-phase
oscillating signal to the modulating circuit, respectively; a
fourth conducting circuit, comprising a seventh conducting trace
and an eighth conducting trace arranged to conduct the negative
oscillating signal and the positive oscillating signal of the
second quadrature-phase oscillating signal to the modulating
circuit, respectively; wherein one of the conducting traces of the
first signal trace block and one of the conducting traces of the
second signal trace block are symmetric to each other.
6. The signal modulator of claim 5, wherein the first conducting
trace and the eighth conducting trace are bilaterally symmetric to
each other, the second conducting trace and the seventh conducting
trace are bilaterally symmetric to each other, the third conducting
trace and the sixth conducting trace are bilaterally symmetric to
each other, and the fourth conducting trace and the fifth
conducting trace are bilaterally symmetric to each other.
7. The signal modulator of claim 5, wherein the first conducting
trace and the eighth conducting trace are equal in length, the
second conducting trace and the seventh conducting trace are equal
in length, the third conducting trace and the sixth conducting
trace are equal in length, and the fourth conducting trace and the
fifth conducting trace are equal in length.
8. The signal modulator of claim 1, wherein a first order of
coupling the first in-phase oscillating signal and the first
quadrature-phase oscillating signal to the first signal trace block
is the same as a second order of coupling the second in-phase
oscillating signal and the second quadrature-phase oscillating
signal to the second signal trace block.
9. The signal modulator of claim 1, wherein an effective phase
difference between the first oscillating signal and the second
oscillating signal is larger than a specific phase difference by a
phase value, and the effective phase difference between the third
oscillating signal and the fourth oscillating signal is smaller
than the specific phase difference by the phase value.
10. The signal modulator of claim 1, wherein the signal modulator
is a part of a receiver arranged to receive the wireless
communication signal being a radio frequency signal or a part of a
transmitter arranged to transmit the wireless communication signal
according to the first oscillating signal, the second oscillating
signal, the third oscillating signal, and the fourth oscillating
signal.
11. A signal modulating method, comprising: utilizing a modulating
circuit to modulate a wireless communication signal according to a
first oscillating signal, a second oscillating signal, a third
oscillating signal, and a fourth oscillating signal; utilizing a
first signal trace block to conduct a first in-phase oscillating
signal having a first phase to the modulating circuit such that the
modulating circuit receives the first oscillating signal having a
second phase, and to conduct a first quadrature-phase oscillating
signal having a third phase to the modulating circuit such that the
modulating circuit receives the second oscillating signal having a
fourth phase; and utilizing a second signal trace block to conduct
a second in-phase oscillating signal having a fifth phase to the
modulating circuit such that the modulating circuit receives the
third oscillating signal having a sixth phase, and to conduct a
second quadrature-phase oscillating signal having a seventh phase
to the modulating circuit such that the modulating circuit receives
the fourth oscillating signal having an eighth phase; wherein a
phase difference between the first phase and the second phase
substantially equals a phase difference between the eighth phase
and the seventh phase, and a phase difference between the fourth
phase and the third phase substantially equals a phase difference
between the sixth phase and the fifth phase.
12. The signal modulating method of claim 11, wherein a phase of
the first in-phase oscillating signal is the same as a phase of the
second in-phase oscillating signal, and a phase of the first
quadrature-phase oscillating signal is the same as a phase of the
second quadrature-phase oscillating signal.
13. The signal modulating method of claim 11, wherein the step of
utilizing the first signal trace block to conduct the first
in-phase oscillating signal having the first phase to the
modulating circuit such that the modulating circuit receives the
first oscillating signal having the second phase, and to conduct
the first quadrature-phase oscillating signal having the third
phase to the modulating circuit such that the modulating circuit
receives the second oscillating signal having the fourth phase
comprises: utilizing a first conducting circuit to conduct the
first in-phase oscillating signal to the modulating circuit; and
utilizing a second conducting circuit to conduct the first
quadrature-phase oscillating signal to the modulating circuit; and
the step of utilizing the second signal trace block to conduct the
second in-phase oscillating signal having the fifth phase to the
modulating circuit such that the modulating circuit receives the
third oscillating signal having the sixth phase, and to conduct the
second quadrature-phase oscillating signal having the seventh phase
to the modulating circuit such that the modulating circuit receives
the fourth oscillating signal having the eighth phase comprises:
utilizing a third conducting circuit to conduct the second in-phase
oscillating signal to the modulating circuit; and utilizing a
fourth conducting circuit to conduct the second quadrature-phase
oscillating signal to the modulating circuit; wherein one of the
first conducting circuit and the second conducting circuit and one
of the third conducting circuit and the fourth conducting circuit
are symmetric to each other.
14. The signal modulating method of claim 13, wherein the first
conducting circuit and the fourth conducting circuit are
bilaterally symmetric to each other, and the second conducting
circuit and the third conducting circuit are bilaterally symmetric
to each other.
15. The signal modulating method of claim 11, wherein the first
in-phase oscillating signal, the first quadrature-phase oscillating
signal, the second in-phase oscillating signal, the second
quadrature-phase oscillating signal are differential oscillating
signals each comprising a positive oscillating signal and a
negative oscillating signal; the step of utilizing the first signal
trace block to conduct the first in-phase oscillating signal having
the first phase to the modulating circuit such that the modulating
circuit receives the first oscillating signal having the second
phase, and to conduct the first quadrature-phase oscillating signal
having the third phase to the modulating circuit such that the
modulating circuit receives the second oscillating signal having
the fourth phase comprises: utilizing a first conducting circuit
comprising a first conducting trace and a second conducting trace
to conduct the positive oscillating signal and the negative
oscillating signal of the first in-phase oscillating signal to the
modulating circuit, respectively; utilizing a second conducting
circuit comprising a third conducting trace and a fourth conducting
trace to conduct the negative oscillating signal and the positive
oscillating signal of the first quadrature-phase oscillating signal
to the modulating circuit, respectively; the step of utilizing the
second signal trace block to conduct the second in-phase
oscillating signal having the fifth phase to the modulating circuit
such that the modulating circuit receives the third oscillating
signal having the sixth phase, and to conduct the second
quadrature-phase oscillating signal having the seventh phase to the
modulating circuit such that the modulating circuit receives the
fourth oscillating signal having the eighth phase comprises:
utilizing a third conducting circuit comprising a fifth conducting
trace and a sixth conducting trace to conduct the positive
oscillating signal and the negative oscillating signal of the
second in-phase oscillating signal to the modulating circuit,
respectively; utilizing a fourth conducting circuit comprising a
seventh conducting trace and an eighth conducting trace to conduct
the negative oscillating signal and the positive oscillating signal
of the second quadrature-phase oscillating signal to the modulating
circuit, respectively; wherein one of the conducting traces of the
first signal trace block and one of the conducting traces of the
second signal trace block are symmetric to each other.
16. The signal modulating method of claim 15, wherein the first
conducting trace and the eighth conducting trace are bilaterally
symmetric to each other, the second conducting trace and the
seventh conducting trace are bilaterally symmetric to each other,
the third conducting trace and the sixth conducting trace are
bilaterally symmetric to each other, and the fourth conducting
trace and the fifth conducting trace are bilaterally symmetric to
each other.
17. The signal modulating method of claim 15, wherein the first
conducting trace and the eighth conducting trace are equal in
length, the second conducting trace and the seventh conducting
trace are equal in length, the third conducting trace and the sixth
conducting trace are equal in length, and the fourth conducting
trace and the fifth conducting trace are equal in length.
18. The signal modulating method of claim 11, wherein a first order
of coupling the first in-phase oscillating signal and the first
quadrature-phase oscillating signal to the first signal trace block
is the same as a second order of coupling the second in-phase
oscillating signal and the second quadrature-phase oscillating
signal to the second signal trace block.
19. The signal modulator of claim 11, wherein an effective phase
difference between the first oscillating signal and the second
oscillating signal is larger than a specific phase difference by a
phase value, and the effective phase difference between the third
oscillating signal and the fourth oscillating signal is smaller
than the specific phase difference by the phase value.
Description
BACKGROUND
[0001] The present invention relates to a signal modulator and
related modulating method, and more particularly to an image-free
signal modulator and related modulating method.
[0002] In a wireless communication system, such as a low IF
(intermediate frequency) transceiving system or an OPLL (Offset
Phase-locked Loop) transceiving system, two oscillating signals
(i.e., the in-phase oscillating signal and the quadrature-phase
oscillating signal) having a 90 degree phase difference can be used
to modulate/down-convert a radio frequency (RF) receiving signal
via a frequency modulator in the receiver to obtain an in-phase
input signal and a quadrature-phase input signal, and used to
modulate/up-convert a base-band signal via a frequency modulator in
the transmitter to obtain an up-converted in-phase signal and a
up-converted quadrature-phase signal. When the phase difference
between the two oscillating signals is not perfectly 90 degrees,
however, some unwanted signal, e.g., the image signal, may be
induced in the output of the modulator. Conventionally, the phase
mismatch between the in-phase oscillating signal and the
quadrature-phase oscillating signal is mainly caused by the length
mismatch between the traces utilized for conducting the in-phase
oscillating signal and the quadrature-phase oscillating signal
respectively. Ideally, the problem of the image signal may be
improved by carefully routing the layout of the traces to make them
perfectly equal in length and parasitic condition. In practice,
however, the intrinsic layout mismatch problem may still cause
mismatch of the traces and inevitably generate the image signal.
Since the image signal may seriously affect quality of the wireless
communication system, such as the linearity, how to remove the
image signal that emerges in the output of the frequency modulator
in a wireless communication system has become an important issue in
this field.
SUMMARY
[0003] One of the objectives is to provide an image-free frequency
modulator and related modulating method.
[0004] According to a first embodiment of the present invention, a
signal modulator is provided. The signal modulator comprises a
modulating circuit, a first signal trace block, and a second signal
trace block. The modulating circuit is arranged to modulate a
wireless communication signal according to a first oscillating
signal, a second oscillating signal, a third oscillating signal,
and a fourth oscillating signal. The first signal trace block is
arranged to conduct a first in-phase oscillating signal having a
first phase to the modulating circuit such that the modulating
circuit receives the first oscillating signal having a second
phase, and conduct a first quadrature-phase oscillating signal
having a third phase to the modulating circuit such that the
modulating circuit receives the second oscillating signal having a
fourth phase. The second signal trace block is arranged to conduct
a second in-phase oscillating signal having a fifth phase to the
modulating circuit such that the modulating circuit receives the
third oscillating signal having a sixth phase, and conduct a second
quadrature-phase oscillating signal having a seventh phase to the
modulating circuit such that the modulating circuit receives the
fourth oscillating signal having an eighth phase. A phase
difference between the first phase and the second phase
substantially equals a phase difference between the eighth phase
and the seventh phase, and a phase difference between the fourth
phase and the third phase substantially equals a phase difference
between the sixth phase and the fifth phase.
[0005] According to a second embodiment of the present invention, a
signal modulating method is provided. The signal modulating method
comprises: utilizing a modulating circuit to modulate a wireless
communication signal according to a first oscillating signal, a
second oscillating signal, a third oscillating signal, and a fourth
oscillating signal; utilizing a first signal trace block to conduct
a first in-phase oscillating signal having a first phase to the
modulating circuit such that the modulating circuit receives the
first oscillating signal having a second phase, and to conduct a
first quadrature-phase oscillating signal having a third phase to
the modulating circuit such that the modulating circuit receives
the second oscillating signal having a fourth phase; and utilizing
a second signal trace block to conduct a second in-phase
oscillating signal having a fifth phase to the modulating circuit
such that the modulating circuit receives the third oscillating
signal having a sixth phase, and to conduct a second
quadrature-phase oscillating signal having a seventh phase to the
modulating circuit such that the modulating circuit receives the
fourth oscillating signal having an eighth phase; wherein a phase
difference between the first phase and the second phase
substantially equals a phase difference between the eighth phase
and the seventh phase, and a phase difference between the fourth
phase and the third phase substantially equals a phase difference
between the sixth phase and the fifth phase.
[0006] These and other objectives of the present invention will no
doubt become obvious to those of ordinary skill in the art after
reading the following detailed description of the preferred
embodiment that is illustrated in the various figures and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a layout illustrating a signal modulator according
to a first embodiment of the present invention.
[0008] FIG. 2 is an equivalent circuit diagram of the signal
modulator as shown in FIG. 1.
[0009] FIG. 3A is a diagram illustrating the relationship between a
phase of a first oscillating signal and a phase of a second
oscillating signal.
[0010] FIG. 3B is a diagram illustrating the relationship between a
phase of a third oscillating signal and a phase of a fourth
oscillating signal.
[0011] FIG. 4 is a flowchart illustrating a signal modulating
method according to a second embodiment of the present
invention.
DETAILED DESCRIPTION
[0012] Certain terms are used throughout the description and
following claims to refer to particular components. As one skilled
in the art will appreciate, electronic equipment manufacturers may
refer to a component by different names. This document does not
intend to distinguish between components that differ in name but
not function. In the following description and in the claims, the
terms "include" and "comprise" are used in an open-ended fashion,
and thus should be interpreted to mean "include, but not limited to
. . . ". Also, the term "couple" is intended to mean either an
indirect or direct electrical connection. Accordingly, if one
device is coupled to another device, that connection may be through
a direct electrical connection, or through an indirect electrical
connection via other devices and connections.
[0013] Please refer to FIG. 1 in conjunction with FIG. 2. FIG. 1 is
a layout illustrating a signal modulator 100 according to a first
embodiment of the present invention. FIG. 2 is an equivalent
circuit diagram of the signal modulator 100 as shown in FIG. 1. The
signal modulator 100 comprises a dividing circuit 102, a first
signal trace block 104, a second signal trace block 106, a coupling
circuit 108, a modulating circuit 110, and a combining circuit 112.
In this embodiment, the signal modulator 100 is a part of a
receiver arranged to receive a wireless communication signal Sr
being a radio frequency (RF) signal; however, this is not a
limitation of the present invention. After appropriately modifying
the signal modulator 100, the signal modulator 100 may also be used
in a transmitter arranged to transmit a base-band signal into an IF
(intermediate frequency) signal or an RF signal (e.g., the wireless
communication signal Sr) according to the first oscillating signal
Soc1, the second oscillating signal Soc2, the third oscillating
signal Soc3, and the fourth oscillating signal Soc4 as shown in
FIG. 1.
[0014] In this embodiment, the dividing circuit 102 is used to
divide an oscillating signal Soc to generate a first in-phase
oscillating signal Si1, a second in-phase oscillating signal Si2, a
first quadrature-phase oscillating signal Sq1, and a second
quadrature-phase oscillating signal Sq2. It is noted that the phase
difference between the phase P1 of the first in-phase oscillating
signal Si1 and the phase P2 of the first quadrature-phase
oscillating signal Sq1 is 90 degrees, and the phase difference
between the phase P3 of the second in-phase oscillating signal Si2
and the phase P4 of the second quadrature-phase oscillating signal
Sq2 is also 90 degrees.
[0015] The modulating circuit 110 is arranged to modulate the
wireless communication signal Sr according to a first oscillating
signal Soc1, a second oscillating signal Soc2, a third oscillating
signal Soc3, and a fourth oscillating signal Soc4. When the first
in-phase oscillating signal Si1, the second in-phase oscillating
signal Si2, the first quadrature-phase oscillating signal Sq1, and
the second quadrature-phase oscillating signal Sq2 are generated,
the first signal trace block 104 is arranged to conduct the first
in-phase oscillating signal Si1 to the modulating circuit 110 such
that the modulating circuit 110 receives the first oscillating
signal Soc1 having a phase of Po1, and conduct the first
quadrature-phase oscillating signal Sq1 to the modulating circuit
110 such that the modulating circuit 110 receives the second
oscillating signal Soc2 having a phase of Po2. The second signal
trace block 106 is arranged to conduct the second in-phase
oscillating signal Si2 to the modulating circuit 110 such that the
modulating circuit 110 receives the third oscillating signal Soc3
having a phase of Po3, and conduct the second quadrature-phase
oscillating signal Sq2 to the modulating circuit 110 such that the
modulating circuit 110 receives the fourth oscillating signal Soc4
having a phase of Po4. According to the arrangement of the first
signal trace block 104 and the second signal trace block 106, the
phase difference between the phase Po1 and the phase P1
substantially equals the phase difference between the phase Po4 and
the phase P4, and the phase difference between the phase Po2 and
the phase P2 substantially equals the phase difference between the
phase Po3 and the phase P3.
[0016] It should be noted that, in this embodiment, the signal
modulator 100 is installed in a part of a differential receiver,
therefore the signal modulator 100 is also a differential circuit
system, which means that the first in-phase oscillating signal Si1,
the first quadrature-phase oscillating signal Sq1, the second
in-phase oscillating signal Si2, the second quadrature-phase
oscillating signal Sq2, the first oscillating signal Soc1, the
second oscillating signal Soc2, the third oscillating signal Soc3,
and the fourth oscillating signal Soc4 are differential oscillating
signals each comprising a positive (+) oscillating signal and a
negative (-) oscillating signal. Therefore, the first signal trace
block 104 comprises a conducting circuit 1042 and a conducting
circuit 1044, wherein the conducting circuit 1042 further comprises
a conducting trace 1042a and a conducting trace 1042b arranged to
conduct the positive oscillating signal Si1+ and the negative
oscillating signal Si1- of the first in-phase oscillating signal
Si1 to the modulating circuit 110 to be Soc1+ and Soc1-
respectively; and the second conducting circuit 1044 further
comprises a conducting trace 1044a and a conducting trace 1044b
arranged to conduct the negative oscillating signal Sq1- and the
positive oscillating signal Sq1+ of the first quadrature-phase
oscillating signal Sq1 to the modulating circuit 110 to be Soc2-
and Soc2+ respectively. The second signal trace block 106 comprises
a conducting circuit 1062 and a conducting circuit 1064, wherein
the conducting circuit 1062 further comprises a conducting trace
1062a and a conducting trace 1062b arranged to conduct the positive
oscillating signal Si2+ and the negative oscillating signal Si2- of
the second in-phase oscillating signal Si2 to the modulating
circuit 110 to be Soc3+ and Soc3- respectively; and the conducting
circuit 1064 further comprises a conducting trace 1064a and a
conducting trace 1064b arranged to conduct the negative oscillating
signal Sq2- and the positive oscillating signal Sq2+ of the second
quadrature-phase oscillating signal Sq2 to the modulating circuit
110 to be Soc4- and Soc4+ respectively. It should be noted that the
conducting circuit 1042 and the conducting circuit 1064 are
bilaterally symmetric to each other, and the conducting circuit
1044 and the conducting circuit 1062 are bilaterally symmetric to
each other. More specifically, the conducting trace 1042a and the
conducting trace 1064b are bilaterally symmetric to each other, the
conducting trace 1042b and the conducting trace 1064a are
bilaterally symmetric to each other, the conducting trace 1044a and
the conducting trace 1062b are bilaterally symmetric to each other,
and the conducting trace 1044b and the conducting trace 1062a are
bilaterally symmetric to each other as shown in FIG. 1.
[0017] In other words, in this embodiment, the conducting trace
1042a and the conducting trace 1064b are equal in length, the
conducting trace 1042b and the conducting trace 1064a are equal in
length, the conducting trace 1044a and the conducting trace 1062b
are equal in length, and the conducting trace 1044b and the
conducting trace 1062a are equal in length. The order of coupling
the first in-phase oscillating signal Si1 and the first
quadrature-phase oscillating signal Sq1 to the first signal trace
block 104 (i.e., the order from left to middle in FIG. 1) is the
same as the order of coupling the second in-phase oscillating
signal Si2 and the second quadrature-phase oscillating signal Sq2
to the second signal trace block 106 (i.e., the order from the
middle to right in FIG. 1).
[0018] The coupling circuit 108 is an AC coupling circuit utilized
for coupling the first oscillating signal Soc1, the second
oscillating signal Soc2, the third oscillating signal Soc3, and the
fourth oscillating signal Soc4 to the modulating circuit 110, in
which the modulating circuit 110 is arranged to receive the first
oscillating signal Soc1, the second oscillating signal Soc2, the
third oscillating signal Soc3, and the fourth oscillating signal
Soc4 for down-converting the wireless communication signal Sr from
the radio frequency into the IF frequency. Furthermore, the
modulating circuit 110 comprises a first mixer 1102, a second mixer
1104, a third mixer 1106, and a fourth mixer 1108. The first mixer
1102 is coupled to the conducting circuit 1042 and arranged to
modulate the wireless communication signal Sr to generate a first
in-phase output signal Sio1 according to the first oscillating
signal Soc1. The second mixer 1104 is coupled to the conducting
circuit 1044 and arranged to modulate the wireless communication
signal Sr to generate a first quadrature-phase output signal Sqo1
according to the second oscillating signal Soc2. The third mixer
1106 is coupled to the conducting circuit 1062 and arranged to
modulate the wireless communication signal Sr to generate a second
in-phase output signal Sio2 according to the third oscillating
signal Soc3. The fourth mixer 1108 is coupled to the conducting
circuit 1064 and arranged to modulate the wireless communication
signal Sr to generate a second quadrature-phase output signal Sqo2
according to the fourth oscillating signal Soc4.
[0019] Furthermore, the combining circuit 112 is coupled to the
first mixer 1102, the second mixer 1104, the third mixer 1106, and
the fourth mixer 1108, the combining circuit 112 is arranged to
generate an in-phase signal Si by combining the first in-phase
output signal Sio1 and the second in-phase output signal Sio2 and
generate a quadrature-phase signal Sq by combining the first
quadrature-phase output signal Sqo1 and the second quadrature-phase
output signal Sqo2.
[0020] According to FIG. 1, it can be seen that the conducting
circuit 1042 and the conducting circuit 1064 are bilaterally
symmetric to each other, and the conducting circuit 1044 and the
conducting circuit 1062 are bilaterally symmetric to each other,
therefore the phase difference between the first oscillating signal
Soc1 and the first in-phase oscillating signal Si1, which is caused
by the conducting circuit 1042, is equal to the phase difference
between the fourth oscillating signal Soc4 and the second
quadrature-phase oscillating signal Sq2, which is caused by the
conducting circuit 1064, and the phase difference between the
second oscillating signal Soc2 and the first quadrature-phase
oscillating signal Sq1, which is caused by the conducting circuit
1044, is equal to the phase difference between the third
oscillating signal Soc3 and the second in-phase oscillating signal
Si2, which is caused by the conducting circuit 1062. Moreover, the
effective phase difference between the first oscillating signal
Soc1 and the second oscillating signal Soc2 is larger than a
specific phase difference (e.g., 90 degree) by a phase value (e.g.,
.phi.rr in the following FIG. 3A and FIG. 3B), and the effective
phase difference between the third oscillating signal Soc3 and the
fourth oscillating signal Soc4 is smaller than the specific phase
difference by the phase value. For simplicity, the following
mathematical calculation concerning the signal modulator 100
assumes that the first in-phase oscillating signal Si1 is the same
as the second in-phase oscillating signal Si2, and the first
quadrature-phase oscillating signal Sq1 is the same as the second
quadrature-phase oscillating signal Sq2. In other words, the phase
P1 of the first in-phase oscillating signal Si1 is the same as the
phase P3 of the second in-phase oscillating signal Si2, and the
phase P2 of the first quadrature-phase oscillating signal Sq1 is
the same as the phase P4 of the second quadrature-phase oscillating
signal Sq2.
[0021] If the wireless communication signal Sr is represented by
cos [(.omega..sub.LO+.DELTA..omega.)t], and the image signal of the
wireless communication signal Sr is represented by cos
[(.omega..sub.LOt-.DELTA..omega.)t], the first in-phase oscillating
signal Si1 and the second in-phase oscillating signal Si2 can be
represented by cos(.omega..sub.LOt), the first quadrature-phase
oscillating signal Sq1 and the second quadrature-phase oscillating
signal Sq2 can be represented by sin(.omega..sub.LOt), the phase
error induced by the difference between the conducting circuit 1042
and the conducting circuit 1044 is .phi.rr, and the phase error
induced by the difference between the conducting circuit 1062 and
the conducting circuit 1064 is also .phi.rr, then the first
oscillating signal Soc1 can also be represented by
cos(.omega..sub.LOt), the second oscillating signal Soc2 can be
represented by sin [(.omega..sub.LO)t+.phi.rr], the third
oscillating signal Soc3 can be represented by cos
[(.omega..sub.LO)t-.phi.rr], and the fourth oscillating signal Soc4
can be represented by sin(.omega..sub.LOt). Please also refer to
FIG. 3A and FIG. 3B. FIG. 3A is a diagram illustrating the
relationship between the phase Po1 of the first oscillating signal
Soc1 and the phase Po2 of the second oscillating signal Soc2. FIG.
3B is a diagram illustrating the relationship between the phase Po3
of the third oscillating signal Soc3 and the phase Po4 of the
fourth oscillating signal Soc4. Therefore, the phase mismatch
(i.e., .phi.rr) between the phase Po1 of the first oscillating
signal Soc1 and the phase Po2 of the second oscillating signal Soc2
is equal to the phase mismatch (i.e., .phi.rr) between the phase
Po3 of the third oscillating signal Soc3 and the phase Po4 of the
fourth oscillating signal Soc4.
[0022] For the wireless communication signal Sr of cos
[(.omega..sub.LOt+.DELTA..omega.)t]: the output signal of the first
mixer 1102 combined with the output signal of the second mixer 1104
can be represented by equation (1):
Sc 1 = cos ( .DELTA. .omega. t ) + 1 2 .phi. rr sin ( .DELTA.
.omega. t ) ( 1 ) ##EQU00001##
[0023] The output signal of the third mixer 1106 combined with the
output signal of the fourth mixer 1108 can be represented by
equation (2):
Sc 2 = cos ( .DELTA. .omega. t ) + 1 2 .phi. rr sin ( .DELTA.
.omega. t ) ( 2 ) ##EQU00002##
[0024] For the image signal cos
[(.omega..sub.LOt-.DELTA..omega.)t]: the output signal of the first
mixer 1102 combined with the output signal of the second mixer 1104
can be represented by equation (3):
Sc 3 = 1 2 cos ( .DELTA. .omega. t ) - 1 2 cos ( .DELTA. .omega. t
) + 1 2 .phi. rr sin ( .DELTA. .omega. t ) ( 3 ) ##EQU00003##
[0025] The output signal of the third mixer 1106 combined with the
output signal of the fourth mixer 1104 can be represented by
equation (4):
Sc 4 .apprxeq. 1 2 cos ( .DELTA. .omega. t ) - 1 2 .phi. rr sin (
.DELTA. .omega. t ) - 1 2 cos ( .DELTA. .omega. t ) ( 4 )
##EQU00004##
[0026] Therefore, according to the above mathematical calculation
concerning the signal modulator 100, when the signal Sc3 is
combined with the signal Sc4, the signal Sc3 and the signal Sc4
cancel each other, which means that the image signal cos
[(.omega..sub.LOt-.DELTA..omega.)t] of the wireless communication
signal Sr will substantially contribute no signal component in the
output of the combining circuit 112. It should be noted that, in
this embodiment, the wanted signal is obtained by combining the
signal Sc1 and the signal Sc2.
[0027] Accordingly, the operation of the above embodiment can be
summarized in the steps shown in FIG. 4. FIG. 4 is a flowchart
illustrating a signal modulating method 400 according to a second
embodiment of the present invention. For brevity, details of the
signal modulating method 400 can be obtained by referring to the
above paragraphs concerning the signal modulator 100. Provided that
substantially the same result is achieved, the steps of the
flowchart shown in FIG. 4 need not be in the exact order shown and
need not be contiguous, that is, other steps can be intermediate.
The signal modulating method 400 comprises the steps:
[0028] Step 402: Utilize the conducting circuit 1042 to conduct the
first in-phase oscillating signal Si1 to the modulating circuit
110;
[0029] Step 404: Utilize the conducting circuit 1044 to conduct the
first quadrature-phase oscillating signal Sq1 to the modulating
circuit 110;
[0030] Step 406: Utilize the conducting circuit 1062 to conduct the
second in-phase oscillating signal Si2 to the modulating circuit
110;
[0031] Step 408: Utilize the conducting circuit 1064 to conduct the
second quadrature-phase oscillating signal Sq2 to the modulating
circuit 110;
[0032] Step 410: Arrange the modulating circuit 110 to modulate the
wireless communication signal Sr according to the first oscillating
signal Soc1, the second oscillating signal Soc2, the third
oscillating signal Soc3, and the fourth oscillating signal Soc4 to
generate the first in-phase output signal Sio1, the first
quadrature-phase output signal Sqo1, the second in-phase output
signal Sio2, and the second quadrature-phase output signal Sqo2
respectively;
[0033] Step 412: Combine the first in-phase output signal Sio1 and
the second in-phase output signal Sio2 to generate the in-phase
signal Si and combine the first quadrature-phase output signal Sqo1
and the second quadrature-phase output signal Sqo2 to generate the
quadrature-phase signal Sq.
[0034] According to the embodiment, the objective is to make the
phase difference between the first oscillating signal Soc1 and the
first in-phase oscillating signal Si1, caused by the conducting
circuit 1042, substantially equal to the phase difference between
the fourth oscillating signal Soc4 and the second quadrature-phase
oscillating signal Sq2, which is caused by the conducting circuit
1064, and the phase difference between the second oscillating
signal Soc2 and the first quadrature-phase oscillating signal Sq1,
which is caused by the conducting circuit 1044, equal to the phase
difference between the third oscillating signal Soc3 and the second
in-phase oscillating signal Si2, which is caused by the conducting
circuit 1062, therefore the conducting circuit 1042 and the
conducting circuit 1064 are designed to be bilaterally symmetric to
each other, and the conducting circuit 1044 and the conducting
circuit 1062 are also designed to be bilaterally symmetric to each
other. Then, according to the above-mentioned mathematical
calculation concerning the signal modulator 100, the signal
component induced by the image signal cos
[(.omega..sub.LOt-.DELTA..omega.)t] of the wireless communication
signal Sr cancel each other at the output of the combining circuit
112.
[0035] Briefly, the present exemplary embodiments use four mixers
(i.e., 1102-1108) to modulate the wireless communication signal Sr
according to four oscillating signals (i.e., Soc1-Soc4) to generate
the first in-phase output signal Sio1, the first quadrature-phase
output signal Sqo1, the second in-phase output signal Sio2, and the
second quadrature-phase output signal Sqo2 respectively, then the
in-phase signal Si is obtained by combining the first in-phase
output signal Sio1 and the second in-phase output signal Sio2, and
the quadrature-phase signal Sq is obtained by combining the first
quadrature-phase output signal Sqo1 and the second quadrature-phase
output signal Sqo2. By appropriately designing the conducting
circuits 1042, 1044, 1062, and 1064 that conduct the first in-phase
oscillating signal Si1, the first quadrature-phase oscillating
signal Sq1, the second in-phase oscillating signal Si2, the second
quadrature-phase oscillating signal Sq2 respectively, the signal
component induced by the image signal cos
[(.omega..sub.LOt-.DELTA..omega.)t] of the wireless communication
signal Sr can cancel each other after being combined by the
combining circuit 112.
[0036] Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made
while retaining the teachings of the invention.
* * * * *