Angular velocity sensor

An angular velocity sensor includes coupling beams supported afloat by highly flexible support beams so as to be movable relative to a substrate, with the support beams being flexible in the x-axis and a y-axis directions and being symmetrical with respect to the center of the sensor. A first vibrator and a second vibrator are supported by respective coupling beams through spring beams that are highly flexible in the x-direction, with the spring beams being symmetrical with respect to the x-axis passing through the center symmetrical to each other with respect to the y-axis passing through the center. Drive electrodes drive at least one of the first vibrator and the second vibrator to vibrate in the x-direction. First displacement detection electrodes detect a y-directional vibration of the first vibrator and second displacement detection electrodes detect a y-directional vibration of the second vibrator. Precision with respect to detecting the angular velocity is prevented from being lowered by electrical and mechanical disturbances.

This application is based on and claims priority under 35 U.S.C. .sctn. 119 
with respect to Japanese Application No. 10(1998)-176992 filed on Jun. 24, 
1998, the entire content of which is incorporated herein by reference. 
FIELD OF THE INVENTION 
The present invention generally relates to an angular velocity sensor. More 
specifically, the present invention pertains to an angular velocity sensor 
having a mass or vibrator which is supported in a floating manner with 
respect to a substrate. The angular velocity sensor may be of the type in 
which a floating semiconductor thin film formed by semiconductor 
micromachining technology is oscillated in an x-direction by electrically 
attracting/releasing it by way of comblike electrodes. 
BACKGROUND OF THE INVENTION 
Known types of angular velocity sensors include a floating comblike 
electrode (with one set of comb fingers or segments) at the left latus 
part of a floating thin film and a floating comblike electrode (with one 
set of comb fingers) at the right latus part of the floating thin film 
(left floating comb-like electrode and right floating comb-like 
electrode). Fixed comblike electrodes are provided and have two sets of 
comb fingers, a left fixed comb-like electrode and a right fixed comb-like 
electrode whose fingers interdigitate with the respective sets of fingers 
of the left and right floating comb-like electrodes in a non-contacting 
parallel fashion. The floating thin film is vibrated in an x-direction by 
applying voltages alternately between the left floating comb-like 
electrode and the left fixed comb-like electrode, and between the right 
floating comb-like electrode and the right fixed comb-like electrode. When 
the angular velocity of rotation about a z-axis acts on the floating thin 
film, this floating thin film is subjected to a Coriolis force, and the 
floating thin film undergoes an elliptic vibration in which it is also 
vibrated in the y-direction. When the floating thin film is made of an 
electric conductor or when an electrode is joined to the floating thin 
film, and when a detection electrode parallel to the xz-plane of the 
floating thin film is disposed on a substrate beforehand, the capacitance 
between the detection electrode and the floating thin film fluctuates or 
changes in correspondence with the y-component (angular velocity 
component) of the elliptic vibration. The angular velocity can be found by 
measuring the change (amplitude) of the capacitance. Angular velocity 
sensors of this type are described in, for example, Japanese Patent 
Application Laid-Open No. 248872/1993, Japanese Patent Application 
Laid-Open No. 218268/1995, Japanese Patent Application Laid-Open No. 
152327/1996, Japanese Patent Application Laid-Open No. 127148/1997, and 
Japanese Patent Application Laid-Open No. 42973/1997. 
U.S. Pat. No. 5,635,638 discloses an angular velocity sensor in which, as 
shown in FIG. 4 of the patent, a pair of vibrators are coupled by a pair 
of semicircular beams, with the pair of vibrators being supported by eight 
anchors through the beams which are highly flexible or bendable in the 
vibrating direction x of the respective vibrators. 
The angular velocity sensor has separate multipoint anchor portions which 
are distant from one another. Therefore, when subjected to an external 
force associated with a temperature change or the like, each of the beam 
spring portions for moving the vibrator as a simple harmonic motion 
undergoes a compressive or tensile stress. For this reason, the resonance 
frequency of the vibrator changes with temperature and exhibits hysteresis 
characteristics having discontinuous points. This undesirably lowers the 
precision of the sensor. 
With known angular velocity sensors having separate multipoint anchor 
portions as disclosed in, for example, Japanese Patent Application 
Laid-Open No. 218268/1995, it is found that the vibration of the vibrator 
during driving operation will leak into the vibration at the detection 
side due to the distant anchor portions, and so the precision will lower. 
Also, with the known angular velocity sensor in which the immobile points 
of a driving vibration mode and a detecting vibration mode do not 
coincide, as disclosed in, for example, Japanese Patent Application 
Laid-Open No. 218268/1995, it is found that the detection precision for an 
angular velocity will be reduced under the influences of the external 
force and the vibration leakages between the two modes. Moreover, when a 
vibrating component diminishing the vibration based on the Coriolis force 
is contained in the driving vibration mode, the detection output of the 
angular velocity is small. In this regard, there is an occasion where the 
vibration of the vibrator in the prior art becomes unstable due to 
different amplitudes in the +x-direction and -x-direction, and this is 
undesirable. 
With the angular velocity sensor disclosed in U.S. Pat. No. 5,635,638, 
oscillating springs are not connected to the center of gravity of each of 
the vibrators. It is therefore conjectured that the vibrations of the 
vibrators will become unbalanced when drive forces exerted on oscillating 
masses are nonuniform due to a discrepancy in manufacturing dimensions. 
Additionally, the vibrations become nonlinear. The unstable fluctuations 
of the detection outputs are accordingly incurred by the unbalance of the 
shift fluctuations of the resonance frequencies of the vibrators, and so 
the S/N ratio (signal-to-noise) of the angular velocity signal will be 
inferior. Also, because a vibration driving signal travels to a detecting 
capacitor, the S/N ratio of the angular velocity signal will be lowered. 
Further, with the known sensor, leakage of the driving oscillation flow as 
leakage signals to the respective detecting portions. In this regard, 
because electrical distances and geometrical distances from an oscillating 
portion to the respective detecting portions are not symmetrical, the 
leakage signals cannot be eliminated even by contriving or providing the 
operations of an electric circuit portion. A degradation in the S/N ratio 
is thus brought about. 
In light of the foregoing, a need exists for an angular velocity sensor 
that is able to prevent the detection precision from being lowered due to 
physical (electrical and mechanical) disturbances. 
A need also exists for an angular velocity sensor that is able to suppress 
the degradation of the signal-to-noise ratio associated with leaks of the 
vibration driving signal, to thereby heighten the detection precision for 
the angular velocity sensor. 
SUMMARY OF THE INVENTION 
According to one aspect of the invention, an angular velocity sensor 
includes a loop spring beam which is flexible in the x-axis direction and 
the y-axis direction, and which is supported by floating support members 
so as to be adapted to be vibrated in directions extending along an 
xy-plane relative to a substrate, and an oscillation device for driving at 
least one of the points of the loop spring beam that intersect with the 
x-axis and the y-axis so as to vibrate in the extending direction of the. 
A first drive frame and a second drive frame are continuous with 
respective intersection points of the loop spring beam with the x-axis and 
lie at positions symmetric with respect to the y-axis. The first and 
second drive frames are supported afloat to be movable relative to the 
substrate by support members that are flexible in the extending direction 
of the x-axis. A first vibrator is disposed in the first drive frame and 
is continuous with the spring beams that are flexible in the y-direction 
as well as the first drive frame. A second vibrator is disposed in the 
second drive frame and is continuous with spring beams that are flexible 
in the y-direction and continuous with the second drive frame. A first 
displacement detection device detects a y-directional vibration of the 
first vibrator and a second displacement detection device detects a 
y-directional vibration of the second vibrator. 
According to the present invention, when at least one of the intersection 
points of the loop spring beam with the x-axis and y-axis, for example the 
intersection points with the y-axis, are driven to vibrate in the 
extending direction of the y-axis by the oscillation device, the 
x-directional vibrations in which the phases shift 180 degrees from those 
of the y-directional vibrations appear at the intersection points of the 
loop spring beam with the x-axis, and the first drive frame and second 
drive frame vibrate in opposite phases in the x-direction. Likewise, the 
first vibrator and the second vibrator vibrate in opposite phases in the 
x-direction. When an angular velocity acts around a z-axis, the vibrations 
of the first vibrator and the second vibrator become elliptic vibrations 
in which the vibrators and vibrate also in the y-direction, for the reason 
that these vibrators are supported by the spring beams which are highly 
flexible in the y-direction. Because the x-directional vibrations of the 
first vibrator and the second vibrator are in relatively opposite phases, 
the y-directional vibrations thereof are in opposite phases relative to 
each other. The first and second displacement detection devices detect the 
y-directional vibrations. 
When the vibration detection signals of the first and second displacement 
detection devices are differentially amplified, a vibration detection 
signal at a level which is approximately double the level of the vibration 
detection signal of each displacement detection device is obtained. 
Simultaneously, electrical noise is reduced and signal components 
associated with any mechanical disturbance other than the angular velocity 
are canceled from each other. By way of example, in a case where an 
acceleration or a deceleration has acted in the y-direction, the resulting 
movements of the first vibrator and the second vibrator are in the same 
sense, and the levels of the displacement detection signals of the first 
and second displacement detection devices fluctuate to the same extent in 
the same sense. However, when the displacement detection signals are 
differentially amplified, the fluctuations of the signal levels are 
canceled from each other. Accordingly, the S/N ratio of the angular 
velocity signal is not degraded by disturbances such as the acceleration. 
The loop spring beam is supported by the floating support members so as to 
be adapted to be vibrated in the directions extending along the xy-plane, 
relative to the substrate. Moreover, the first drive frame and the second 
drive frame are supported afloat to move relative to the substrate by the 
support members which are highly flexible in the extending direction of 
the x-axis. Therefore, the first drive frame and the second drive frame 
are not highly susceptible to temperature distortions, and the 
x-directional vibrations of the frames and the first and second vibrators 
are stabilized. In addition, the first and second vibrators are supported 
afloat through the spring beams which are highly flexible in the 
y-direction. Therefore, the first and second vibrators are not 
significantly susceptible to temperature distortions, and their 
y-directional vibrations corresponding to the angular velocity are 
stabilized. Thus, the reliability (stability) of the angular velocity 
signal is high. 
When the intersection points of the loop spring beam with the y-axis are 
driven to vibrate in the extending direction of the y-axis by the 
oscillation device, the first and second vibrators are equally distant 
from the corresponding intersection points. Therefore, the leakage of the 
oscillating drive signals to the first and second displacement detection 
devices becomes equal, and they are canceled by the differential 
amplification mentioned above. It is accordingly possible to obtain the 
angular velocity detection signal having a high S/N ratio. 
When the intersection points of the loop spring beam with the x-axis are 
driven to vibrate in the x-direction, the two intersection points with the 
x-axis are respectively driven to vibrate by the pair of oscillation 
devices to thereby equalize the distances between the individual 
oscillation devices and the corresponding displacement detection devices. 
It is accordingly possible to similarly obtain the angular-velocity 
detection signal of high S/N ratio. 
The angular velocity sensor of the present invention may further include a 
third drive frame and a fourth drive frame which are respectively 
continuous with the intersection points of the loop spring beam with the 
y-axis, and are supported afloat so as to be movable relative to the 
substrate by support members that are highly flexible in the extending 
direction of the y-axis. The third drive frame and fourth drive frame lie 
at positions that are symmetrical with respect to the x-axis. A third 
vibrator is disposed in and continuous with the third drive frame and is 
continuous with spring beams that are highly flexible in the x-direction. 
A fourth vibrator is disposed in the fourth drive frame, is continuous 
with spring beams that are highly flexible in the x-direction, and is 
continuous with the fourth drive frame. A third displacement detection 
device detects the x-directional vibration of the third vibrator, and a 
fourth displacement detection device detects an x-directional vibration of 
the fourth vibrator. 
According to the present invention, signals similar to the displacement 
detection signals of the first and second displacement detection devices 
are also obtained by the third and fourth displacement detection devices. 
The signals of the third and fourth displacement detection devices are 
differentially amplified, and the resulting signal is added to the 
differential amplification signal of the first and second displacement 
detection devices in a phased state, whereby an angular velocity signal of 
high S/N ratio is obtained at a high level. Also, the first thru fourth 
drive frames and the first thru fourth vibrators are combined into sets, 
each consisting of one drive frame and one vibrator, and the respective 
sets are located at intervals of 90 degrees around the center of the 
sensor so as to be symmetric with respect to the x-axis and y-axis, 
whereby the angular velocity signal of high S/N ratio and high reliability 
(stability) is obtained and is little affected by a temperature change, 
electric noise, and a disturbing acceleration, deceleration or vibration. 
The vibrators are preferably members each being in the shape of a frame, 
and the displacement detection devices are located inside the respective 
vibrators. The floating support members include spring beams which lie on 
the x-axis and y-axis, and are highly flexible in the extending directions 
of the axes. Also, the floating support members include a frame member 
with which the spring beams that are highly flexible in the extending 
directions of the axes are continuous. The spring beams are highly 
flexible in the directions of the x-axis and y-axis, and each is 
continuous to the frame member at one end and is fixed to the substrate at 
the other end. 
According to another aspect of the invention, an angular velocity sensor 
includes coupling beams supported afloat to be movable relative to a 
substrate by floating support members that are highly flexible in the 
directions of the x-axis and the y-axis and symmetrical with respect to 
the center 0 of the sensor. A first vibrator and a second vibrator are 
respectively supported by the coupling beams through spring beams that are 
highly flexible in the x-direction, each of which is symmetric with 
respect to the x-axis passing through the center, and symmetric to each 
other with respect to the y-axis passing through the center. An 
oscillation device drives one or both of the first and second vibrators so 
as to vibrate in the x-direction. A first displacement detection device 
detects a y-directional vibration of the first vibrator, and a second 
displacement detection device detects a y-directional vibration of the 
second vibrator. 
In a preferred embodiment of the present invention, the elements of the 
angular velocity sensor are arrayed entirely in point symmetry with 
respect to the center of the sensor. With this construction, 
notwithstanding that the drive frames and the vibrators are anchored at 
multiple points, the symmetry with respect to the center is prevented from 
collapsing, by releasing thermal expansion, internal stresses, etc., and 
the reliability (stability) of the angular velocity signal is thus quite 
high.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates the angular velocity sensor according to a first 
embodiment of the present invention. The angular velocity sensor includes 
drive electrodes 5, 6, drive detection electrodes 15, 16, angular-velocity 
detection electrodes 12, 13 and 22, 23, frequency adjustment electrodes 
25, 26, and dummy electrodes 65, 66. 
In this embodiment, anchors are joined to a silicon substrate 100 formed 
with an insulator layer. The anchors are made of polycrystalline silicon 
which contains an impurity for establishing a conductivity (hereinbelow, 
termed conductive polycrystalline silicon). The anchors include floater 
anchors a1, a2, a3, a4, anchors for the drive electrodes 5, 6, anchors for 
the drive detection electrodes 15, 16, anchors for the angular-velocity 
detection electrodes 12, 13 and 22, 23, anchors for the frequency 
adjustment electrodes 25, 26, and anchors for the dummy electrodes 65, 66 
which are respectively located at positions symmetric to the drive 
detection electrodes 15, 16. These anchors, except the anchors 65, 66, are 
connected to connection electrodes (not specifically illustrated) by 
wiring lines which are formed on the insulator layer overlying the silicon 
substrate 100. 
Using a lithographic semiconductor process, spring beams b1, b2, b3, b4 of 
conductive polycrystalline silicon, each of which is in the shape of a 
flattened ring situated at an angle of 45 degrees to the x-axis as shown 
in FIG. 1, are formed to be afloat from the silicon substrate 100 and to 
be continuous to the respective corresponding floater anchors a1, a2, a3, 
a4. Similarly formed is a coupling frame c which is in the shape of a 
rectangular loop continuous to the spring beams b1.about.b4. The coupling 
frame c is symmetric with respect to the x-axis and the y-axis which pass 
through the center 0 of the sensor. The floater anchors a1, a2, a3, a4 and 
the spring beams b1, b2, b3, b4 connected to the coupling frame c are 
distributed symmetrically with respect to the x-axis and the y-axis. 
Two spring beams 1, 2 each in the shape of a flattened ring are 
respectively connected to and continuous with the midpoints of the 
adjoining two lateral sides c1, c3 of the coupling frame c which are 
parallel to the x-axis. A quadrilateral loop 3 forming a loop spring beam 
having round corners is connected to and continuous with both of the 
spring beams 1, 2, and y-axial vibration frames 4, 24 are connected to and 
continuous with the respective spring beams 1, 2. X-axial vibration frames 
14, 64 are connected to and continuous with those points of the 
quadrilateral loop 3 which intersect the x-axis. A first drive frame 7 and 
a second drive frame 17 are also connected to and continuous with the 
intersection points at which the quadrilateral loop 3 intersects the 
x-axis. The first and second drive frames 7, 17 are rectangular frames, 
the other intersection points of which with the x-axis are respectively 
connected to and continuous through spring beams 8, 18 having a flattened 
ring shape to the midpoints of those two latera or sides c4, c2 of the 
coupling frame c which are parallel to the y-axis. A first vibrator 11 and 
a second vibrator 21 are respectively connected to and continuous with the 
inner sides of the first drive frame 7 and the second drive frame 17 
through spring beams 9, 10 and 19, 20 having a flattened ring-shape. Also 
these constituents are afloat from the silicon substrate 100 and are made 
of conductive polycrystalline silicon. 
The first and second drive frames 7, 17, and the first and second vibrators 
11, 21 are symmetrical in shape and are symmetrically positioned with 
respect to the x-axis and the y-axis which pass through the center 0 of 
the sensor. The spring beams 1, 2, 8, 18, 9, 10, 19, 20 are also symmetric 
with respect to and symmetrically disposed with respect to the x-axis and 
the y-axis. 
Each of the y-axial vibration frames 4, 24 includes a comb-like movable 
electrode whose fingers or segments are distributed at equal pitches in 
the direction of the x-axis and extend or protrude in the direction of the 
y-axis. On the other hand, each of the drive electrodes 5, 6 and the 
frequency adjustment electrodes 25, 26, which are made of the conductive 
polycrystalline silicon and which are connected to and continuous with the 
corresponding electrode anchors, includes a comb-like fixed electrode 
whose fingers are distributed in the x-direction and protrude in the 
interspaces of the x-directional distribution of the fingers of the 
movable electrode. 
Voltages which are higher than the potential of the y-axial vibration frame 
4 (being substantially equal to the earth potential level of the equipment 
including the sensor), are applied alternately to the drive electrodes 5, 
6, whereby the y-axial vibration frame 4 is vibrated in the y-direction. 
Owing to the vibration in the y-direction of the y-axial vibration frame 
4, the two latera or sides of the quadrilateral loop 3 parallel to the 
x-axis are vibrated in the y-direction, and the y-axial vibration frame 24 
partly interposed between the frequency adjustment electrodes 25, 26 is 
vibrated in the y-direction. Further, the drive frames 7, 17 and the 
x-axial vibration frames 14, 64 are vibrated in the x-direction with a 
phase difference of 180 degrees from the y-directional vibration of the 
frame 24. The y-directional vibrations of the y-axial vibration frames 4, 
24 are in opposite phases relative to each other. The x-directional 
vibrations of the x-axial vibration frames 14, 64 are also in opposite 
phases relative to each other so that the first drive frame 7 and the 
second drive frame 17 perform tuning fork vibrations. The first vibrator 
11 and the second vibrator 21 which are respectively supported by the 
first drive frame 7 and the second drive frame 17 are similarly vibrated 
in the x-direction in opposite phases. That is, they perform tuning fork 
vibrations. 
A first vibration system consisting of the drive frame 7 and the vibrator 
11, and a second vibration system consisting of the drive frame 17 and the 
vibrator 21, are caused to perform the tuning fork vibrations in this 
manner, thereby to attain an x-directional oscillation of high energy 
consumption efficiency. 
Because the x-axial vibration frame 14 (64) is vibrated in the x-direction 
together with the drive frame 17 (7), the capacitances between the drive 
frame 17 and the drive detection electrodes 15, 16 fluctuate, and the 
capacitances between the drive frame 64 and the drive detection electrodes 
65, 66 also fluctuate in phases opposite to those of the capacitance 
fluctuations relating to the drive frame 17. 
Each of the vibrators 11, 21 is substantially in the shape of a frame, in 
which a plurality of gangway or separating beams extending in the 
x-direction are spaced apart at equal pitches in the y-direction. One pair 
of fixed detection electrodes 12, 13 and 22, 23 of conductive 
polycrystalline silicon exists in the interspace between each pair of 
gangway beams that are adjacent to each other in the y-direction. These 
electrodes are supported by the respectively corresponding anchors for the 
detection electrodes on the substrate 100, and are electrically connected 
to and continuous with the anchors. 
Although each pair of detection electrodes 12, 13 (22, 23) is insulated 
from each other, those detection electrodes of the pairs of detection 
electrodes 12, 13 (22 and 23) which are associated for detecting the 
y-directional vibration (y-directional displacement) of the vibrator 11 
(21) are connected in common to an electric lead and then to charge 
amplifiers 46, 47 (56 and 57) as shown in FIG. 1. 
When an angular velocity around the z-axis passing through the center 0 of 
the sensor acts during the x-directional fork vibrations of the vibrators 
11, 21, these vibrators 11, 21 come to perform elliptic vibrations which 
also have y-axial components and which are in relatively opposite phases. 
Thus, the electrodes 12, 13 and 22, 23 undergo capacitance fluctuations 
corresponding to the y-directional vibrations. The capacitance 
fluctuations of the electrodes 12, 13 are in relatively opposite phases, 
and those of the electrodes 22, 23 are similarly in relatively opposite 
phases. Here, because the y-directional vibrations of the vibrators 11, 21 
are in opposite phases, the capacitance fluctuations of the electrodes 12, 
22 are in relatively opposite phases, and those of the electrodes 13, 23 
are similarly in relatively opposite phases. 
The movable electrodes of the y-axial vibration frame 24 and the fixed 
electrodes of the frequency adjustment electrodes 25, 26 function to 
adjust the velocities (spring forces) of the y-directional vibrations of 
the two latera or sides of the quadrilateral loop 3 parallel to the x-axis 
(and the x-directional vibrations of the two latera thereof parallel to 
the y-axis, and the x-directional vibrations of the drive frame 7, 17, all 
the vibrations being forced by the y-directional vibrations of the two 
latera of the quadrilateral loop 3) and to lower the vibration frequencies 
of the drive frames 7, 17 down to values which are lower on the order of 
several hundred Hz relative to the resonance frequencies of the vibrators 
1, 21. The drive frames 7, 17 are oscillated in the x-direction at 
frequencies equivalent to their natural vibration frequencies by applying 
drive voltages. To heighten a sensitivity for detecting the angular 
velocity, the resonance frequencies (natural vibration frequencies) of the 
vibrators 11, 21 are designed to be several hundred Hz higher than the 
resonance frequencies (natural vibration frequencies) of the drive frames 
7, 17, and voltages proportional to the displacements of the x-axial 
vibration frame 14 (the displacements being zero at the rest point of the 
frame 14 and being taken in the +x and -x-directions) are applied to the 
frequency adjustment electrodes 25, 26 to adjust the levels of the 
voltages, whereby the resonance frequencies of the drive frames 7, 17 are 
finely adjusted to values near the designed value thereof. 
An angular-velocity detection circuit, including electric elements 41a-60, 
the timing signal generator TSG and the feedback processing circuit FCR as 
shown in FIG. 1, is connected to the angular velocity sensor which 
includes the mechanical elements described above. The timing signal 
generator TSG generates drive signals A and B for driving the drive frames 
7, 17 at the resonance frequencies in the x-direction, to apply the 
generated signals to the drive circuits 41a and 41b. The TSG also applies 
synchronizing signals for synchronous detection to the synchronous 
detection circuits 45, 50. FIG. 7 illustrates the drive signals A and B, a 
drive feedback signal as well as an angular velocity signal, and 
x-directional and y-directional vibrations. The drive circuits 41a, 41b 
apply drive voltages (pulses) to the drive electrodes 5, 6 in synchronism 
with the respective drive signals A and B. Thus the vibrators 11, 21 are 
vibrated in opposite phases in the x-direction together with the 
respective corresponding drive frames 7, 17 through the quadrilateral loop 
3. Owing to the vibrations, the capacitances of the drive detection 
electrodes 15, 16 fluctuate in opposite phases. The charge amplifiers 42, 
43 convert the fluctuations of the capacitances into voltage fluctuations 
(capacitance signals). 
The differential amplifier 44 differentially amplifies the capacitance 
signals (in opposite phases) of the amplifiers 42, 43. The differential 
amplifier 44 generates a differential signal in which the amplitude of the 
capacitance signal produced by one charge amplifier is substantially 
doubled, and in which the noise components of the capacitance signals are 
canceled from each other. The generated differential signal is applied to 
the synchronous detection circuit 45 and the feedback processing circuit 
FCR. The synchronous detection circuit 45 detects the differential signal 
applied by the differential amplifier 44, namely an x-directional 
vibration detection voltage expressive of the x-directional vibration, in 
synchronism with a synchronizing signal inphase with the drive signal. It 
generates a feedback signal which expresses the phase difference of the 
x-directional vibration relative to the drive pulse signal. The generated 
feedback signal is applied to the feedback processing circuit FCR. 
The feedback processing circuit FCR supplies the drive circuits 41a, 41b 
with phase shift signals for bringing the levels of the phase difference 
signals applied by the synchronous detection circuit 45 into agreement 
with preset values. The drive circuits 41a, 41b having received the phase 
shift signals shift the phases of the output drive voltages relative to 
the drive signals, in correspondence with the phase shift signals. In a 
state where the phase difference signal levels of the synchronous 
detection circuit 45 have substantially equalized to the preset values, 
the x-directional vibrations of the drive frames 7, 17 are stabilized. The 
frequency adjustment circuits 59, 60 apply D.C. voltages to the respective 
frequency adjustment electrodes 25, 26. The D.C. voltages serve to lower 
the vibration frequencies of the drive frames 7, 17 to values which are 
several hundred Hz lower than the resonance frequencies (designed values) 
of the respective vibrators 11, 21. 
When an angular velocity around the z-axis passing through the center 0 
acts during the stable resonant fork vibrations, Coriolis forces act on 
the drive frames 7, 17 and the vibrators 11, 21, which are caused to 
perform elliptic vibrations containing y-directional vibrations in 
addition to the x-directional vibrations. Herein, the drive frames 7, 17 
are supported by the respective spring beams 8, 18 which are highly 
flexible in the x-direction but highly rigid in the y-direction, and the 
two latera or sides of the quadrilateral loop 3 parallel to the y-axis, so 
that they vibrate little in the y-direction. In contrast, the vibrators 
11, 21 are supported by the spring beams 9, 10 and 19, 20 which are highly 
flexible in the y-direction and so they vibrate greatly in the 
y-direction. The y-directional vibrations of the vibrators 11, 21 are in 
opposite phases relative to each other. 
The capacitances of the pair of detection electrodes 12, 13 for detecting 
the y-directional vibration of the vibrator 11 fluctuate in opposite 
phases, and the charge amplifiers 46, 47 generate capacitance signals 
expressive of the fluctuations. The differential amplifier 48 generates 
the differential signal of both the capacitance signals, that is the 
differential signal in which the amplitude of the capacitance signal 
generated by one charge amplifier is substantially doubled and in which 
the noise components of the capacitance signals are canceled from each 
other. The generated differential signal is applied to the differential 
amplifier 49. On the other hand, the capacitances of the pair of detection 
electrodes 22, 23 for detecting the y-directional vibration of the 
vibrator 21 fluctuate in opposite phases, and the charge amplifiers 56, 57 
generate capacitance signals expressive of the fluctuations. The 
differential amplifier 58 generates the differential signal of both the 
capacitance signals, that is the differential signal in which the 
amplitude of the capacitance signal generated by one charge amplifier is 
substantially doubled and in which the noise components of the capacitance 
signals are canceled from each other. The generated differential signal is 
applied to the differential amplifier 49. The differential amplification 
signals of the differential amplifiers 49, 58 are in opposite phases 
relative to each other. Accordingly, the differential output of the 
differential amplifier 49 is a detection signal in which the y-directional 
vibration caused by the angular velocity is amplified by canceling noise 
components that simultaneously act on the correspondent signal processing 
circuits of the first vibrator 11 and the second vibrator 21 at 
substantially the same levels and by canceling the y-directional 
displacement components (being also noise components) of the first and 
second vibrators 11, 21 that simultaneously act on these vibrators in the 
same senses on account of any disturbance such as acceleration, 
deceleration or vibration. The detection signal affords a high sensitivity 
for detecting the angular velocity, and a high S/N ratio. 
The differential output, namely the detection signal, is applied to the 
synchronous detection circuit 50 which detects the detection signal in 
synchronism with a synchronizing signal inphase with the drive signal and 
which generates a signal expressive of the angular velocity. The polarity 
(.+-.) of the angular velocity signal represents the direction of the 
angular velocity having acted, while the absolute value of the level of 
the signal represents the magnitude of the angular velocity. 
As stated above, the angular velocity sensor of the first embodiment has a 
dual resonant fork structure of vibration type and is characterized in 
that improvements in temperature characteristics and enhancement of the 
S/N ratio have been realized. To improve the temperature characteristics, 
the coupling frame c being also a protective frame is provided, and the 
increase of a stress attributed to the difference of the thermal 
expansions of the substrate 100 and the vibrators (3, 7, 17, 11, 21) is 
relieved by the coupling frame c and the spring beams b1, b2, b3, b4. More 
specifically, the difference of the thermal expansions of the substrate 
100 and the vibrators (3, 7, 17, 11, 21, 14, 64) is absorbed by the spring 
shape of the spring beams b1, b2, b3, b4. Because the spring beam is in 
the form of a loop shape, it has no hysteresis when the expansion 
associated with temperature is absorbed by the elongation and contraction 
of the spring. Therefore, the temperature characteristics are improved 
still more. 
The spring beam 3 which connects the two vibrators (7, 11 and 17, 21) 
located inside the coupling frame c forming a protective frame, is in a 
shape near or approximating an annulus and is capable of vibration in 
simple harmonic motion having a linearity. In addition, the x-directional 
vibrations of the drive frame 7, the vibrator 11 and the drive frame 64, 
and the drive frame 17, the vibrator 21 and the drive frame 14 make 
possible the drive in opposite phase owing to the characteristics of the 
spring beam 3. These vibrators are connected by the four spring beams 1, 
2, 8, 18 with the protective frame, whereby the stress is relaxed. 
Therefore, the driving vibration in the x-direction becomes the linear 
simple harmonic motion. 
The configuration of the drive section is such that the oscillating portion 
(drive frame 14, spring beam 3) is separate from the vibrators (7, 17, 11, 
21, 14, 64) and it is arranged so as to be equally distant from the two 
vibrators (7, 11, 64 and (17, 21, 14). The detection sections (64, 65, 66 
and 14, 15, 16) for driving displacements are connected to the 
intersection points of the spring 3 with the x-axis and y-axis. This makes 
possible a configuration which diminishes the leakage of the drive signals 
to the driving-displacement detection sections (64, 65, 66 and 14, 15, 16) 
for feeding back the driving displacements of the vibrators, and in which 
the leakage signals leak as inphase components. Therefore, the S/N ratios 
of the detection sections can be enhanced. 
The sections 9-13 and 19-23 for detecting the angular velocity are 
constructed of the vibrators 11 and 21 which are connected to the 
loop-shaped spring beams 9, 10 and 19, 20 inside the drive frames 7 and 
17, and the fixed electrodes 12, 13 and 22, 23 which detect the 
y-directional displacements of the vibrators. Owing to this construction, 
in the vibration mode of the y-directional vibrations corresponding to the 
angular velocity, the drive frames 7 and 17 and the vibrators 11 and 21 
operate in opposite phases so that a balance is held. In this 
construction, therefore, the leakage of the vibrations for detecting the 
angular velocity are almost negligible, and the S/N ratio of the detection 
is enhanced. Additionally, the vibrations for detecting the angular 
velocity may well be inphase. 
FIG. 2 illustrates the angular velocity sensor according to the second 
embodiment of the present invention. According to the second embodiment, 
in order to enhance suppression of the y-directional vibrations of the 
first and second drive frames 7, 17, each of the flat loop spring beams 8, 
18 associated with the first embodiment is divided into two beams 8a, 8 
and 18a, 18b, which are arranged at positions symmetric with respect to 
the x-axis. That is, the beams 8a, 8b are symmetrically positioned on 
either side of the x-axis and the beams 18a, 18b are symmetrically 
positioned on either side of the x-axis. Also, to enhance suppression of 
the x-directional vibrations of the first and second vibrators 11, 22, 
each of the flat loop spring beams 9, 10 and 19, 20 associated with the 
first embodiment is divided into two beams 9a, 9b, 10a, 10b, 19a, 19b, 
20a, 20b. The two beams forming each pair of beams 9a/9b, 10a/10b, 
19a/19b, 20a/20b are arranged at positions symmetric with respect to the 
center line of the corresponding vibrator and parallel to the y-axis. 
Thus, the driving vibrations in the direction of the x-axis are 
effectively separated from vibrations in the direction of the y-axis as 
are to be detected for sensing an angular velocity, and the S/N ratio of 
an angular velocity signal is enhanced. 
FIG. 3 illustrates a third embodiment of the angular velocity sensor 
according to the present invention. According to the third embodiment, the 
drive frames and vibrators in pairs are additionally disposed in order to 
adjust the balance of vibrations caused by an angular velocity 
(y-directional vibrations in the first and second embodiments stated 
above) around the center 0 of the sensor. More specifically, the sensor is 
furnished with a third drive frame 77, flat loop spring beams 79, 80, a 
third vibrator 81, and vibration detection electrodes 82, 83, which are in 
the same configuration as the configuration obtained when the first drive 
frame 7, the flat loop spring beams 9, 10, the first vibrator 11 and the 
vibration detection electrodes 12, 13 as described above are rotated 90 
degrees clockwise. Also, a fourth drive frame 87, two flat loop spring 
beams 89, 90, a fourth vibrator 91, and two vibration detection electrodes 
92, 93 are provided. Once again, these components are in the same 
arrangement as the arrangement obtained when the first drive frame 7, the 
flat loop spring beams 9, 10, the first vibrator 11 and the vibration 
detection electrodes 12, 13 as described above are rotated 270 degrees 
clockwise. Here, all the elements are symmetrically distributed with 
respect to the x-axis and the y-axis. 
When drive voltages (pulses) synchronized with drive the signals A and B 
are respectively applied to the drive electrodes 5, 6 as stated before, 
the first and second drive frames 7, 17 are vibrated in opposite phases in 
the direction of the x-axis, and the third and fourth drive frames 77, 87 
are vibrated in opposite phases in the direction of the y-axis. When the 
angular velocity acts around the z-axis as described above, the first and 
second vibrators 11, 21 are vibrated in opposite phases in the 
y-direction, and the third and fourth vibrators 81, 91 are vibrated in 
opposite phases in the x-direction. 
Although not shown, circuit elements similar to the amplifiers 46, 47, 56, 
57 and differential amplifiers 48, 58, 49, which are connected to the 
first and second sets of vibration detection electrodes 12, 13 and 22, 23 
illustrated in FIG. 1, may be connected also to the third and fourth sets 
of vibration detection electrodes 82, 83 and 92, 93. The output of the 
differential amplifier 49 at the final stage of the first and second 
vibration detection electrode systems, and that of the 
differential-amplifier at the final stage of the third and fourth 
vibration detection electrode systems are applied to the additional 
differential amplifier. In this way, it is possible to produce a vibration 
detection signal caused by the angular velocity, in which the detection 
levels of both the systems are substantially doubled and in which noise 
components are canceled from each other. The produced signal is applied to 
the synchronous detection circuit 50 (in, for example, FIG. 1), whereby an 
angular velocity signal is obtained. In the first and second embodiments, 
the vibrations caused by the angular velocity are detected in the y-axial 
symmetry. Here in the third embodiment, the vibrations are also detected 
in x-axial symmetry. Therefore, the vibrations caused by the angular 
velocity are balanced more, and the angular velocity signal of higher S/N 
ratio can be obtained. 
FIG. 4 illustrates a fourth embodiment of the angular velocity sensor of 
the present invention. The fourth embodiment adopts a further construction 
to that shown in FIG. 3 in which the immobile points of the drive spring 
frame 3 are fixedly supported by anchors a5, a6, a7, a8 through 
loop-shaped spring beams b5, b6, b7, b8. Owing to this construction, the 
drive spring beam 3 is connected to the ground GND of a detection circuit. 
Accordingly, the leakage of drive signals is further diminished, and the 
S/N ratio of an angular velocity signal is further enhanced. 
FIG. 5 illustrates a fifth embodiment of the angular velocity sensor of the 
present invention. In this fifth embodiment, to more further suppress the 
y-directional vibrations of the first and second drive frames 7, 17 and 
the x-directional vibrations of the third and fourth drive frames 81, 91, 
each of the flat loop spring beams is divided into a pair of beams as in 
the second embodiment. Thus, the flat loop spring beams 8, 9, 10, 18, 19, 
20, 1, 89, 90, 2, 79, 80 is divided into a pair of flat loop spring beams 
8a/8b, 9a/9b, 10a/10b, 18a/18b, 19a/19b, 20a/20b, 1a/1b, 89a/89b, 90a/90b, 
2a/2b, 79a/79b, 80a/80b. Moreover, the immobile points of the drive spring 
beam 3 are supported by anchors a5, a6, a7, a8 through loop spring beams 
b5, b6, b7, b8 as in the fourth embodiment. Thus, driving vibrations in 
the x- and y-directions are effectively separated from vibrations in the 
x- and y-directions as are to be detected for sensing the angular 
velocity, and the S/N ratio of the angular velocity signal is enhanced. 
FIG. 6 illustrates a sixth embodiment of the angular velocity sensor 
according to the present invention. In this embodiment, anchors made of 
conductive polycrystalline silicon are joined to a silicon substrate 100 
formed with an insulator layer. The anchors include floater anchors a1, 
a2, a3, a4, anchors for the drive electrodes 5a, 5b and 6a, 6b, anchors 
for the drive detection electrodes 15a, 15b and 16a, 16b, and anchors for 
the angular-velocity detection electrodes 12, 13 and 22, 23. These anchors 
are connected to connection electrodes not specifically shown by wiring 
lines which are formed on the insulator layer overlying the silicon 
substrate 100. 
Using a lithographic semiconductor process, spring beams b1, b2, b3, b4 of 
conductive polycrystalline silicon, which are highly flexible in the 
directions of the x-axis and the y-axis, are formed so as to be afloat 
from the silicon substrate 100 and to be connected to and continuous with 
the respective corresponding floater anchors a1, a2, a3, a4. Similarly 
formed are coupling beams c1, c2 each of which is in the shape of a band 
plate, and connected to and continuous with the spring beams b1, b2, b3, 
b4. The coupling beams c1, c2 are symmetrical with respect to the x-axis 
and symmetrically positioned with respect to the y-axis which both pass 
through the center 0 of the sensor. The floater anchors a1, a2, a3, a4 and 
the spring beams b1, b2, b3, b4 are also distributed symmetrically with 
respect to both the x-axis and the y-axis. 
A first drive frame 7 is supported by the coupling beam c1 through four 
spring beams 31, 32, 33, 34 and a second drive frame 17 is supported by 
the coupling beam c2 through four spring beams 35, 36, 37, 38. The spring 
beams 31, 32, 33, 34, 35, 36, 37, 38 are highly flexible in the 
x-direction, are continuous to the coupling beams, and are connected to 
and continuous with the drive frames 7, 17. The first and second drive 
frames 7, 17 are rectangular frames, and a first vibrator 11 and a second 
vibrator 21 are connected to and continuous with the rectangular frames 
unitarily and inwards. Also these components are afloat from the silicon 
substrate 100 and are made of conductive polycrystalline silicon. 
The first and second drive frames 7, 17, and the first and second vibrators 
11, 21 are symmetrical in shape and are at symmetric positions with 
respect to the x-axis and the y-axis which pass through the center 0 of 
the sensor. The spring beams 31, 32, 33, 34 and 35, 36, 37, 38 are also 
symmetric with respect to and symmetrically positioned with respect to the 
x-axis and y-axis 
The two latera or sides of each of the first and second drive frames 7, 17 
which are parallel to the y-axis include comb-like movable electrodes 
having fingers or segments extending in the x-direction and distributed at 
equal pitches or spacing in the y-direction. Each of the drive electrodes 
5a, 5b and 6a, 6b and the drive detection electrodes 15a, 15b and 16a, 
16b, which are made of the conductive polycrystalline silicon and which 
are connected to and continuous with the respective corresponding 
electrode anchors, includes a comb-like fixed electrode having fingers 
that extend or protrude in the interspaces of the y-directional 
distribution of the fingers of the movable electrode and are distributed 
or spaced apart in the y-direction. 
Voltages which are higher than the potential of the drive frames 7, 17 
(being substantially equal to the earth potential level of the equipment 
including the sensor), are applied alternately to the drive electrodes 5a, 
5b and 6a, 6b, whereby the drive frames 7, 17 are vibrated in the 
x-direction. To bring the drive frames 7, 17 into resonant tuning fork 
vibrations, the x-directional vibrations of the drive frames 7, 17 are set 
in opposite phases relative to each other. 
A first vibration system consisting of the drive frame 7 and the vibrator 
11 and a second vibration system consisting of the drive frame 17 and the 
vibrator 21 are caused to perform the resonant fork vibrations, thereby to 
attain an x-directional oscillation of high energy consumption efficiency. 
Also, the resonance frequencies of the x-directional vibrations of the 
first and second drive frames 7, 17 are designed to be equal. To heighten 
the sensitivity for detecting the angular velocity, the resonance 
frequencies of the y-directional vibrations of the drive frames are 
designed to be several hundred Hz higher than the resonance frequencies of 
the x-directional vibrations. 
Because the drive frames 7, 17 perform the resonant fork vibrations in the 
x-direction, the capacitances between the drive frame 7 and the drive 
detection electrodes 15a, 16a fluctuate in opposite phases, and the 
capacitances between the drive frame 17 and the drive detection electrodes 
15b, 16b fluctuate in phases opposite to those of the capacitance 
fluctuations associated with the drive frame 7. 
Each of the vibrators 11, 21 that is unitary with the respective drive 
frame 7, 17 is substantially in the shape of a frame and includes a 
plurality of gangway or separating beams extending in the x-direction and 
spaced apart at equal pitches in the y-direction. One pair of fixed 
detection electrodes 12, 13 and 22, 23 of conductive polycrystalline 
silicon exists in each interspace between pairs of the gangway beams that 
are adjacent to each other in the y-direction. These electrodes are 
supported by the respective corresponding anchors for the detection 
electrodes on the substrate 100, and are electrically connected to and 
continuous with the anchors. 
Although each pair of detection electrodes 12, 13 (22, 23) is insulated 
from each other, the detection electrodes of each pair of detection 
electrodes 12, 13 (22 and 23) which are associated for detecting the 
y-directional vibration (y-directional displacement) of the vibrator 11 
(21) and which lie at corresponding positions between the pairs, are 
connected in common to an electric lead and then to respective charge 
amplifiers 46, 47 (56 and 57). 
When an angular velocity around the z-axis passing through the center 0 
acts during the x-directional fork vibrations of the vibrators 11, 21, 
these vibrators 11, 21 come perform elliptic vibrations which also have 
y-axial components and which are in relative opposite phases. Thus, the 
electrodes 12, 13 and 22, 23 undergo capacitance fluctuations 
corresponding to the y-directional vibrations. The capacitance 
fluctuations of the electrodes 12, 13 are in relative opposite phases, and 
those of the electrodes 22, 23 are similarly in relatively opposite 
phases. Here, because the y-directional vibrations of the vibrators 11, 21 
are in opposite phases, the capacitance fluctuations of the electrodes 12, 
22 are in relative opposite phases, and those of the electrodes 13, 23 are 
similarly in relative opposite phases. 
A measurement controller TCR generates drive signals A and B for driving 
the drive frames 7, 17 at the resonance frequencies in the x-direction and 
apply the generated signals to the drive circuits 41, 51. The TCR also 
applies synchronizing signals for synchronous detection to synchronous 
detection circuits 45a, 45b, 50a, 50b. 
The drive circuits 41, 51 apply drive voltages (pulses) to the drive 
electrodes 5a, 6a and 5b, 6b in synchronism with the respective drive 
signals A and B. Thus, the vibrators 11, 21 are vibrated in opposite 
phases in the x-direction together with the respective corresponding drive 
frames 7, 17. Owing to the vibrations, the capacitances of the drive 
detection electrodes 15a, 16a and 15b, 16b fluctuate in opposite phases. 
Charge amplifiers 42a, 43a and 42b, 43b convert the fluctuations of the 
capacitances into voltage fluctuations (capacitance signals). Output 
adjustment circuits (variable gain amplifiers) adjust the peak levels of 
the voltage fluctuations to be substantially equal, and they apply the 
adjusted levels to differential amplifiers 44a, 44b. 
The differential amplifiers 44a, 44b differentially amplify the applied 
capacitance signals in opposite phases. The differential amplifiers 44a, 
44b generate differential signals in each of which the amplitude of one 
capacitance signal is substantially doubled, and in each of which the 
noise components of the capacitance signals are canceled from each other. 
The generated differential signals are subjected to output adjustments 
(are amplified by variable gain amplifiers), and the resulting signals are 
applied to the measurement controller TCR and a differential amplifier 61. 
The differential amplifier 61 differentially amplifies the received 
signals, and applies the resulting signal to the synchronous detection 
circuits 45a, 45b. The synchronous detection circuit 45a detects the 
differential signal applied by the differential amplifier 61, namely an 
x-directional vibration detection voltage expressive of the x-directional 
vibration, in synchronism with a synchronizing signal inphase with the 
drive signal. The synchronous detection circuit 45a generates a phase 
signal which expresses the phase difference of the x-directional vibration 
relative to the drive pulse signal. The generated phase signal is applied 
to the measurement controller TCR. On the other hand, the synchronous 
detection circuit 45b detects the differential signal applied by the 
differential amplifier 61, namely an x-directional vibration detection 
voltage expressive of the x-directional vibration, in synchronism with a 
synchronizing signal inphase with the drive signal. The synchronous 
detection circuit 45b generates an amplitude signal which expresses the 
amplitude of the x-directional vibration. The generated amplitude signal 
is applied to the measurement controller TCR. 
The measurement controller TCR supplies the drive circuits 41, 51 with 
phase shift signals for bringing phases expressed by the phase signals 
into agreement with preset values and voltage command signals for bringing 
the amplitudes of the x-directional vibrations expressed by the amplitude 
signals into agreement with present values. The drive circuits 41, 51 
having received the phase shift signals and the voltage command signals, 
shift the phases of the output drive voltages relative to the drive 
signals in correspondence with the phase shift signals, and also shift the 
levels of the output voltages in correspondence with the voltage command 
signals. In a state where the phase shift signals and amplitude signals of 
the synchronous detection circuits 45a, 45b have substantially equalized 
to the preset values, the x-directional vibrations or resonant fork 
vibrations of the drive frames 7, 17 are stabilized. 
When an angular velocity around the z-axis passing through the center 0 
acts during the stable resonant fork vibrations, Coriolis forces act on 
the drive frames 7, 17 which cause elliptic vibrations containing 
y-directional vibrations in addition to the x-directional vibrations. 
Here, the drive frames 7, 17 are supported by the respective spring beams 
31, 32, 33, 34 and 35, 36, 37, 38 which are highly flexible in the 
x-direction but highly rigid in the y-direction, so that the coupling 
beams c1, c2 vibrate in the y-direction together with the drive frames 7, 
17. Because the y- directional vibrations of the drive frames 7, 17 are in 
opposite phases relative to each other, the coupling beams c1, c2 undergo 
torsion (swirl) vibrations about the z-axis passing through the center 0. 
The capacitances of the pair of detection electrodes 12, 13 for detecting 
the y-directional vibration of the vibrator 11 that is unitary with the 
drive frame 7 fluctuate in opposite phases, and the charge amplifiers 46, 
47 generate capacitance signals expressive of the fluctuations. Output 
adjustment circuits (variable gain amplifiers) adjust the peak levels of 
voltage fluctuations to be substantially equal, and apply the adjusted 
signals to a differential amplifier 48. The differential amplifier 48 
generates the differential signal of both the signals, that is the 
differential signal in which the amplitude of one capacitance signal is 
substantially doubled and in which the noise components of the capacitance 
signals are canceled from each other. The generated differential signal is 
applied to a differential amplifier 49 after its level has been adjusted 
by an output adjustment circuit (variable gain amplifier). A similar 
differential signal, which is based on the capacitances of the pair of 
detection electrodes 22, 23 for detecting the y-directional vibration of 
the vibrator 21 that is unitary with the drive frame 17, is applied to the 
differential amplifier 49. Accordingly, the differential output of the 
differential amplifier 49 is a detection signal in which the y-directional 
vibration caused by the angular velocity is amplified, by canceling noise 
components that simultaneously act on the correspondent signal processing 
circuits of the first vibrator 11 and second vibrator 21 at substantially 
the same levels and by canceling the y-directional displacement components 
(being also noise components) of the first and second vibrators 11 , 21 
that simultaneously act on these vibrators in the same senses on account 
of any disturbance such as acceleration, deceleration or vibration. The 
detection signal affords a high sensitivity for detecting the angular 
velocity, and a high SIN ratio. 
The differential output, namely the detection signal, is applied to the 
synchronous detection circuits 50a, 50b. The synchronous detection circuit 
50a detects the detection signal in synchronism with a synchronizing 
signal inphase with the drive signal, and generates a phase signal 
expressive of the direction of the angular velocity. The synchronous 
detection circuit 50b generates an amplitude signal expressive of the 
absolute value of the angular velocity. 
In this sixth embodiment of the angular velocity sensor, the output 
adjustment circuits (amplifiers whose gains are adjustable) are included. 
Therefore, even when the unbalance of the signals in the differential 
arrangement has developed by any of various reasons, the drive signals are 
adjusted at the output stages of the charge amplifiers, and if necessary 
at the input stages of the differential amplifiers, whereby the noise 
components of the signals for the drive detection and the angular velocity 
detection can be reduced. In addition, the unbalance between the detection 
signals can be adjusted. Therefore, the S/N ratio of the angular velocity 
detection can be, of course, heightened or improved and the available 
percentage of the articles of the sensor can be heightened to curtail 
cost. 
The principles, preferred embodiments and modes of operation of the present 
invention have been described in the foregoing specification. However, the 
invention which is intended to be protected is not to be construed as 
limited to the particular embodiments described. Further, the embodiments 
described herein are to be regarded as illustrative rather than 
restrictive. Variations and changes may be made by others, and equivalents 
employed, without departing from the spirit of the present invention. 
Accordingly, it is expressly intended that all such variations, changes 
and equivalents which fall within the spirit and scope of the invention be 
embraced thereby.