JPH07297623A - Antenna circuit and arm loaded type radio equipment - Google Patents

Abstract

PURPOSE:To automatically compensate the difference of resonance frequency of an antenna circuit caused between both cases when a loop antenna is loaded and not loaded on an arm respectively. CONSTITUTION:A loop antenna can be loaded and unloaded at the part of a connector 302 which functions as a switch that connects DC-electrically the antenna 301 to a capacitor 304. The DC voltage is applied to the antenna 301 from a terminal 303a via a resistance 303. A terminal 315 monitors the DC voltage. A capacitor 305 is connected in series to a variable capacity diode 306 and functions to make a radio equipment synchronize with the desired frequency. The DC voltage is applied to the diode 306 for channel selection from a terminal 311 via a resistance 307 and the capacity of the diode 306 is decided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small portable wireless device, particularly to an antenna circuit and a wrist-worn wireless device using the antenna circuit.

[0002]

2. Description of the Related Art Conventionally, there has been a problem of a shift of an antenna resonance circuit due to the influence of a human body when an arm is worn and when the arm is not worn.

[0003]

The present invention is applied to an antenna circuit having a loop antenna integrated with an arm band for mounting on an arm, and an arm mounting type wireless device.

That is, since the loop antenna is worn around the arm, the length of the loop antenna differs depending on the individual who uses it. Then, since the value of the inductance of the loop antenna varies from person to person, the resonance frequency of the antenna circuit varies from person to person, resulting in variations in the gain of the loop antenna. This affects the sensitivity of the wireless device of each individual, and is extremely large, and if the resonance frequency shifts, transmission / reception may not be possible.

On the other hand, when the loop antenna is attached to the arm, the resonance frequency shifts due to the influence of the human body. This means that even if transmission / reception can be performed while worn on the arm, transmission / reception may not be possible if the device is worn on the arm.

Since these are phenomena that occur because the resonance frequency of the antenna circuit shifts, it is sufficient to restore the resonance frequency to the original one, but it is very difficult for the user of the loop antenna to manually perform this. Awkward and unrealistic.

Therefore, an object of the present invention is to provide an antenna circuit capable of automatically correcting the deviation of the resonance frequency of the antenna circuit and always maintaining the resonance frequency at a constant frequency.

The arm-mounted wireless device of the present invention to which such an antenna circuit is attached has a constant sensitivity irrespective of the thickness of the arm of an individual to be used and whether or not the arm is worn. You can send and receive with.

[0009]

In order to solve the above-mentioned problems, an antenna circuit according to the present invention comprises a loop antenna integrated with an arm band to be worn on an arm, and a first antenna connected to the loop antenna. In an antenna circuit in which the variable capacitance diode resonates with respect to a specific frequency, a second variable capacitance diode connected to the antenna circuit,
A voltage generation circuit for generating a DC voltage applied to the second variable capacitance diode for changing the capacitance of the second variable capacitance diode at any time according to the length of the loop antenna. .

Further, the arm-mounted type radio of the present invention includes a loop antenna provided on the arm band, band coupling means for attaching the arm band to the arm, and a capacitive element forming a resonance circuit with the loop antenna. And a control means for controlling the capacitance value of the capacitance element to change to a predetermined value when the loop antenna is worn on the arm and when the arm is not worn. .

Further, the loop antenna comprises a first loop antenna provided in the first arm band and a second loop antenna provided in the second arm band. To do.

Also, the band coupling means has a detection means for detecting whether or not the first loop antenna and the second loop antenna are electrically coupled, and the control means has the It is characterized by being controlled by a detection means.

[0013]

As described above, the object of the present invention is to automatically change the resonance frequency caused by the change in the thickness of the arm and the inductance value of the loop antenna depending on whether the arm is worn or not worn. To correct it. As a means for this, an electrical coupling capacitance is included in the connector portion attached to the loop antenna, or a variable capacitance diode is connected, and these electrical coupling capacitances are automatically changed.
Generally, as the loop antenna becomes longer, the inductance increases, so that the electrical coupling capacitance is reduced. vice versa,
When the loop antenna becomes shorter, the inductance decreases, so that the electrical coupling capacitance increases. By changing in this way, the resonance frequency can be kept constant.

Further, when the inductance changes between when the wrist is worn and when the wrist is not worn, if a DC voltage change corresponding to the change is applied to the variable capacitance diode, the electrical coupling capacitance is automatically changed. Can be
The resonance frequency can be kept constant.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the present invention in which an antenna circuit in which a connector portion of a loop antenna has an electric coupling capacity is applied to a wristwatch band and a connector. The arm bands 101 and 102 are made of an insulating material such as synthetic leather, and are connected to each other by a buckle 103. The buckle 103 has
A metal plate 105 is attached. The metal plate 105 is a buckle 1
It is attached in the middle of 03 so as to cross the arm band 102, and as shown in the figure, it has a sufficiently large area compared to the area of the buckle 103 seen from the surface. Also, the metal plate 105
Is connected from the back side to the loop antenna 106 included in the arm band 10l. Loop antenna l
04 and 106 are made of a conductor such as copper.

The loop antenna 104 inside the arm band 102 becomes narrower in width as it goes to the end of the arm band 102. In the case of a person with thin arms, the arm band 102 has a large number of remaining portions.

That is, although the arm circumferences of the arm bands 101 and 102 are short, the metal plate 105 and the loop antenna 104 are short.
The overlapping area becomes larger. An electrical coupling capacitance is generated in this overlapping portion, and the electrical coupling capacitance in this case becomes large.

On the contrary, in the case of a person with thick arms, the arm band 102
The remaining part of is reduced. That is, the arm band 101,
Although the arm circumference of 102 is long, the overlapping area of the metal plate 105 and the loop antenna 104 is small.

In this case, the electrical coupling capacity becomes small.

The loop antenna 1 included in the arm band
04 does not function as an antenna at the tip of the metal plate 105. Therefore, the long loop antenna means that the loop antenna l
The tip portion of 04 indicates that the opposite side portion is long.

FIG. 2 is an electrical equivalent circuit of the structure of FIG. The loop antennas 104 and 106 are represented by coils and have inductances 104a and 106a. In addition, there are an electric coupling capacitance l07a formed by overlapping the metal plate 105 and the loop antenna l04, and another electric coupling capacitance l08a forming a resonance circuit.

The electrical coupling capacitance 108a is a fixed capacitance or a combination of a variable capacitance diode and a fixed capacitance.
Variable capacity is possible. Both terminals 10 of this capacitance 108a
A high-frequency signal is extracted using either 9a or 10b.

By keeping the product of the sum of the inductances 104a and 106a and the reciprocal of the sum of the reciprocals of the electric coupling capacitors 107a and 108a constant, the same resonance frequency can be always maintained.

[0024] These are expressed by the equation, the inductance L04a, 106a to _{L 104a,} L l06a, electrically coupling capacitance 107a, L08a the _C l07a, C _108a, if the resonance frequency f,

[0025]

[Equation 1]

The following relationship holds. To make f a constant value,

[0027]

[Equation 2]

It suffices if

The loop antenna 1 while maintaining the relationship of the three equations
The value of the electrical coupling capacitance 107a that compensates for the changes in the inductances 104a and 106a when the lengths of 04 and 106 become slightly shorter is theoretically obtained.

The inductances 104a and 106a are connected in a high frequency manner by the buckle 103 and become 1 inductance.

If the value of this inductance is L _total ,

[0032]

[Equation 3]

It becomes

Here, K is the Nagaoka coefficient, μο is the magnetic permeability in vacuum, and S is the loop antenna 104, 106 and the buckle 1
The open area after connection at 03, N is the number of turns of the loop antenna, and is the width of the loop antenna.

The opening area S formed by the loop antenna is
If the opening is circular and its radius is a, then S = πα ² (Equation 5). Now, assuming that the length of the loop antenna is slightly shorter, if the amount of shortening is Δα, then the aperture area S ′ at this time is

[0036]

[Equation 4]

By substituting the equation (6) into the equation (4), L _total when the length of the loop antenna becomes short can be obtained.

L before and after the loop antenna is shortened
The ratio of the _total value is proportional to the ratio of the open area S, and the ratio ΔL
_total is

[0039]

[Equation 5]

Looking at equation (7), when Δα becomes large,
ΔL _total becomes smaller than 1, and Δα = 0, that is,
It can be seen that the value of L _total is smaller than that when the length of the loop antenna is not changed.

Now, next, the electric coupling capacitance 107a is obtained.

[0042]

[Equation 6]

Σ is the dielectric constant of the substance, A is the area of the portion where the loop antenna 104 overlaps the metal plate 105, and d
Is the distance between the two metal surfaces. Σ is obtained from the material of the arm band 102 that covers the loop antenna 104 and the dielectric constant of the minute space between the back surface of the arm band 102 and the metal plate 105.

Here, _assuming that C _l08a >> C _l07a , FIG.
Coupling Capacitance Affecting Resonant Frequency of Resonant Circuit
Can be approximated by C _107a . Therefore,

[0045]

[Equation 7]

As shown in equations (3) and (4), L _total and C
The product of _total must be constant. Therefore, when the loop antenna becomes short, ΔL
The value of the _total may do it to compensate the ratio △ C _total change in C _total. By transforming Equation 3 and expressing this meaning by an equation,

[0047]

[Equation 8]

It becomes From Equations 8 and 9, the value of _{ΔC total} can be replaced with the amount of change of the area A of the electrical coupling capacitance C _107a . Therefore, the area A is regarded as a function of Δα,

[0049]

[Equation 9]

It becomes β is the area when Δα = 0. As _Δα increases, that is, as the length of the loop antenna decreases, the value of A ( _Δα ) increases and the value of C _107a increases. Therefore, the ratio of change of L _{total ΔL}
You can compensate for _total . Then, FIG. 3 is a diagram expressing the l3 equation, and ΔL _total can be compensated by changing A (Δα) in the range of Δα and 2πa. The width of the loop antenna 104 shown in FIG. 1 becomes narrower toward the tip thereof, and the width is such that the area where the loop antenna 104 and the metal plate 105 overlap is 1
You may decide to follow formula 3.

On the other hand, when C _l08a >> C _l07a does not hold, it is necessary to consider the value of C _{l08a in} C _total , but even in that case, C _l08a is included in the expression of A ( _Δα ). Although included, the width of the loop antenna 104 may be determined by theoretical calculation and according to the function.

In this way, when the length of the loop antenna changes by Δα, A (Δα) is automatically determined, and the compensated electrical coupling capacitance C _107a is determined.

The C _l07a determined in this way _forms a _{co-propulsion} circuit together with L _{to tal} when the length of the loop antenna is shortened, but its resonance frequency is _lower than that before the length of the loop antenna is shortened. ,does not change. In this way, the object of the present invention is achieved.

That is, in the case of a person with a thin arm, the loop length of the loop antennas 104 and 106 included in the arm bands 101 and 1.02 that circulate around the arm becomes short, and the inkstances 104a and 106a thereof become small, but the metal The area formed by the plate 105 and the loop antenna 104 becomes large, and the capacitance l07a becomes large. Indant Tax 10
Capacitance 107a captures the reduced amount of 4a and 106a, and the product of the reciprocals of the sums of the reciprocals of inductances 104a,] 06a and cabasitances 107a and 108a becomes constant.

For persons with thick arms, the loop antenna l0
The circumference of 4,106 becomes longer, and its inductance is 1
04a and 106a are large, but capacitance 10
7a becomes smaller. Inductance l04a, l06a
The increase in capacitance is offset by the capacitance l07a,
Inductance l04a, l06a and capacitance l
The product of the reciprocals of the sum of the reciprocals of 07a and 108a is constant.

FIG. 4 is a side view of the buckle portion of FIG. Since the arm band 102 is simply sandwiched between the buckle 103 and the metal plate 105, the attachment / detachment is easy. Further, since the buckle 103 holds the arm band 102 at two places, it cannot be easily pulled out even if the arm band 102 is pulled from both sides.

FIG. 5 is a cross-sectional view of an arm band using the antenna circuit similar to that of FIG. A loop antenna 112 is included inside the arm band 111. And, a large number of burrs 113 for connecting both arm bands are attached. The bristles 113 allow both arm bands to be superposed and connected at any position. And
When overlapping, when the circumference of the arm band 111 is shortened, the overlapping area of the loop antenna 11 is increased, and the portion has a large capacitance. On the other hand, if the circumference of the arm band 11l is increased, the loop antenna ll is increased.
Since the overlapping area of 2 becomes small, the capacitance of that portion becomes small.

FIG. 6 is a view of the embodiment of FIG. 5 as seen from diagonally above. Also in this case, the electrical equivalent circuit is the same as that in FIG. 2, and if the length of the loop antenna 11 changes, the overlapping area of the loop antenna 11 changes automatically.
Since the electrical coupling capacitance l07a changes, the resonance frequency can always be kept at a constant value.

The narrow part of the width of the loop antenna 11 may be determined so as to satisfy the expression (13).

FIG. 7 shows an example in which the present invention is applied to a wristwatch type wireless device. The body 114 includes a radio. This style, which is very simple and does not make you feel like a radio,
It is suitable for simple transceivers and selective call receivers.

FIG. 8 is an antenna circuit diagram in which a variable capacitance diode is attached to a conventional antenna circuit of the present invention.

FIG. 9 shows an example of an antenna circuit used conventionally. This embodiment also shows an embodiment for suppressing the change in the resonance frequency due to the change in the length of the loop antenna.

The loop antenna 201 has a connector 202.
It can be attached and detached at the part of, and electrically,
By connecting the connector 202, the loop antenna 20
1, the loop antenna 201 and the variable resistor 204 are configured.
Will be connected. The variable resistor 204, together with the resistor 203, determines the DC voltage of the variable capacitance diode 206. The power supply voltage is supplied from the terminal 212. This power supply is a power supply that always generates a constant voltage. Then, the loop antenna 201 is connected to the ground 2l.
It is grounded by 1. Therefore, depending on the resistance ratio of the resistor 203 and the variable resistor 204, the variable capacitance diode 20
The voltage applied to 6 is determined. Furthermore, the variable resistor 204
When the resistance value of is changed, the voltage applied to the varactor diode 206 changes, and the capacitance can be changed. Since the resistance value of the variable resistor 204 is a large value of several tens to 100 kΩ, Q of the resonance circuit of the antenna circuit including the loop antenna 201 cannot be lowered, and the sensitivity of the antenna circuit is not lowered.

The capacitors 5, 7 and 10 are for DC interruption.

The variable capacitance diode 208 is originally used for tuning. From the terminal 214, the DC voltage for tuning is applied to the resistor 20.
9 is applied. Conventionally, as shown in FIG. 9, the variable capacitance diode 208, the capacitor 207, and the loop antenna 20l constitute an antenna circuit. This variable capacitance diode 208 can eliminate the variation in the resonance frequency of the antenna circuit for the purpose of always resonating the antenna circuit at the same frequency, or can replace it with a simple capacitor if there is no variation. Is.

Since the object of the present invention is to automatically compensate for the deviation of the resonance frequency when the length of the loop antenna is changed, the antenna circuit which realizes the object has a variable frequency. A major feature is the addition of the capacitance diode 206.

FIG. 10 is a diagram showing the resonance characteristic of the antenna circuit when the length of the loop antenna 20l is long, using the conventionally used antenna circuit as shown in FIG.
FIG. 11 is a diagram showing resonance characteristics when the length of the loop antenna 201 is short similarly.

When the length of the loop antenna 201 is long,
Since the loop antenna 20l has a large inductance, it receives a transmitting station with a low frequency f ₁ . Therefore, when the length of the loop antenna 201 is shortened, its inductance becomes small, so that the sensitivity of the transmitting station f ₁ which has been receiving until now becomes small, and instead, f ₂ at a high frequency is received.
The sensitivity of the transmitting station increases. That is, the tuning shift is caused by changing the length of the loop antenna 201.

According to the antenna circuit of the present invention, it is possible to prevent the shift in tuning caused by such a cause.

Since the inductance is reduced by the length of the loop antenna 201 in FIG. 1L, the capacitance of the variable capacitance diode 206 is increased in order to maintain the maximum sensitivity at the frequency f ₁ . Variable capacitance diode 2
In order to increase the capacitance of 06, the DC voltage applied to the cathode side is lowered. To reduce the DC voltage, the variable resistor 204 may be made smaller. This variable resistor 204 is
It is composed of a connector 202 portion and a resistance plate 212 formed inside the arm band. By doing this,
Even if the loop antenna 201 is shortened, the frequency can be kept at f ₁ . With respect to the value of the resistance plate 212, since this value is used to compensate for the increase or decrease of the inductance, the value of l2 is used as the capacitance for compensating the change ΔL _{total of the} inductance.
The formula ΔC _total can be used. That is, when the loop antenna length is shortened by Δα, the change amount of the equivalent capacitance connected in parallel to the loop antenna is ΔC _total , so that the variable capacitance is adjusted so that the change amount of C _total follows Equation 12. The value of the diode 206 may be changed at any time.

That is, in the variable capacitance diode 206,
It suffices to apply a DC voltage that matches the voltage. In addition, it is only necessary to attach the necessary resistance.

FIG. 12 is a diagram showing the structure of the variable resistor 204. The connector 202 connects the loop antennas 201 a and 20 lb included in the arm band 222. The arm band 222a on the side where the loop antenna 201a is located further includes a resistance plate 221. The resistance plate 22l has sections of different resistance values connected in series, and each of the sections has an electrically conductive hole 220. These holes 220
Has a structure that penetrates from the front surface to the back surface of the arm band. One of the holes 220 is connected to the loop antenna 201b by coupling with a protrusion inside the connector 202.

FIG. 13 is a vertical sectional view of the connector 202. A metal fitting 224 is attached to the tip of the loop antenna 201b, and a metal fitting 225 is attached in the middle of the arm band 222a having the loop antenna 201a. The metal fittings 224 and 225 are electrically connected to the loop antennas 201a and 201b.
6, the hook 227, and the holding metal fitting 228 are used. The loop antenna 201 is crimped by these three metal fittings.
a and 20 lb are joined.

Now, the metal fitting 224 has a projection 223. This is the hole 22 provided on one side of the arm band 222a.
Inserted in one of 0. The hole 220 is electrically conductive and is opened in the resistance plate 221. The projection 223 and the hole 220 have a constricted cross section to ensure electrical continuity. In this way, the resistance plate 221
Then, the metal fitting 224 and the loop antenna 20 lb are connected.

When the loop antenna 201 becomes long, the projection 223 has a hole 2 on the tip side of the loop antenna 201a.
20 will be inserted. Then, since the length of the resistance plate 221 is to be lengthened and used, the resistance value between the projection 22 and the variable capacitance diode 206 increases. Therefore, the voltage applied to the cathode of the variable capacitance diode 206 increases, and the loop antenna 20l
In order to compensate for the increase in the inductance of the capacitor, the capacitance becomes smaller, and as a result, the tuning deviation does not occur and a constant sensitivity can be maintained.

On the contrary, if the loop antenna 201 becomes shorter, the hole 220 on the radio device main body side of the loop antenna 201a is formed.
Since the resistance plate 22l is used by shortening it, the applied voltage is lowered, the amount of the variable capacitance diode 206 is increased in a form of compensating for the decrease of the inductance of the loop antenna 201, and the deviation of the tuning is prevented. It can be done.

As described above, when the antenna circuit of the present invention is used, even if the length of the arm band integrated with the loop antenna is changed, the tuning deviation is automatically compensated. Can always be kept constant.

Further, it goes without saying that the present invention can be applied to a circuit in which the antenna circuit is a balanced output type as shown in FIG.

FIG. 15 is an antenna circuit diagram in which a variable capacitance diode is attached to the conventional antenna circuit of the present invention, but the purpose is different in the embodiment of FIG. Figure 15
In, there is shown an embodiment in which the deviation of the resonance frequency of the antenna circuit is automatically compensated when the loop antenna is worn on the arm and when it is not worn.

The loop antenna 301 has a connector 302.
It can be attached and detached at the part. At the same time, the connector 302 serves as a switch for DC-electrically connecting the loop antenna 301 side and the capacitor 304 side. The connector 302 may be located anywhere on the loop antenna 30l. A DC voltage is applied from the terminal 303a via the resistor 303. The terminal 315 is a terminal for monitoring a DC voltage. Capacitor 305 and variable capacitance diode 3 connected in series
06 is a capacitor provided so that the radio device can be tuned to a target frequency. It is, so to speak, a capacitor for tuning. Then, a DC voltage for channel selection is applied from the terminal 31l via the resistor 307 to determine the capacitance of the variable capacitance diode.

The characteristic of the antenna circuit of the present invention is that, apart from the variable capacitance diode 306 for tuning described above, a variable capacitance diode 309, a capacitor 308 connected in series with the variable capacitance diode 309, and a DC voltage The point is that a resistor 310 for application and a terminal 312 are provided.

First, in a state where the loop antenna 301 does not go around the arm, the loop antenna 301 is used by using the tuning capacitor 305 and the variable capacitance diode 306.
It is assumed that tuning is achieved by configuring a resonant circuit with. In this state, it is assumed that the loop antenna 301 is cut off at the connector 302, and that the loop antenna 30l is connected to the connector 302 this time around the arm.

Then, the value of the inductance of the loop antenna 301 changes due to the influence of the arm of the human body, and the resonance frequency of the antenna circuit shifts as compared with the case where the arm does not circulate around the arm. Therefore, the DC voltage applied to the variable capacitance diode 310 is changed to equivalently change the capacitance of the capacitor connected in parallel to the loop antenna 301, and the antenna circuit is set to the resonance frequency when the original arm is not rotated. Retune. As a result, the sensitivity of the wireless device can be stably maintained without the resonance frequency shifting due to the influence of the arm. Of course, even if the user first removes the arm from the arm after orbiting the arm, the resonance frequency shift can be corrected by these operations.

The high frequency signal of the wireless device is amplified by the high frequency circuit connected to the end of the terminal 313, and a stable output can be obtained.

FIG. 16 is a circuit block diagram showing an embodiment of an arm-mounted receiver incorporating the antenna circuit of the present invention.

The signal received by the loop antenna 301 is
The high frequency amplifier circuit 3 is passed through the antenna circuit 320 of the present invention.
It is amplified at 24, mixed with the signal from the local oscillator circuit 325, and converted to an intermediate frequency. Further, after passing through the amplifier circuit 327, it is detected by the detection circuit 328, the demodulated signal is processed by the reproduction circuit 329, and various information signals are obtained.

For example, it is assumed that the arm is not first worn on the arm. In this state, the DC voltage from the tuning circuit 330 is applied to the terminal 307, tuned to a certain frequency f ₁ and receiving a high frequency signal. Then, at the output of the intermediate frequency amplifier circuit 327, the high frequency amplifier circuit 324
The AGC circuit 331 is connected to adjust the gain of the. With this circuit, the input signal of the detection circuit 328 is always adjusted to a constant level.

FIG. 17 is a spectrum diagram showing the resonance characteristic of the antenna circuit in this state. Resonance characteristic 3
At the highest gain frequency of 40 is the signal spectrum 34l.

Next, it is assumed that the connector 302 is cut off and the loop antenna 301 is DC-cut off from the antenna circuit 320. Then, the voltage of the terminal 3l5 rises from the ground potential until now to the power supply potential. Then, this time, the loop antenna 301 to be worn on the arm goes around the arm and is connected to the connector 302. Then, the terminal 315 becomes the ground potential again. Here, there is no change in the DC voltage from the tuning circuit 330. However, in the switch circuit 32l, when the terminal 315 reaches the ground potential, a signal for stopping the operation of the AGC circuit 33l is output. Further, a signal for operating the frequency correction circuit 322 is output. Further, a signal for operating the frequency correction data output circuit 323 is output.

In this state, since the AGC circuit 331 does not operate, the output of the intermediate frequency amplification circuit 327 is proportional to the output level of the antenna circuit 320. Then, the resonance frequency of the antenna circuit, in order to attached to the arm, offset from the frequency f ₁ before mounting, and is f _2.

At this time, the frequency correction data output circuit 32
3 outputs a signal so as to shift the resonance frequency by a minute frequency Δf with respect to the currently resonant frequency f ₂ .

Upon receiving this signal, the frequency correction circuit 322
Outputs a DC voltage corrected for Δf and is applied to the terminal 312, and the antenna circuit 320 has a resonance frequency of f ₂ + Δf.

FIG. 18 is a diagram showing the resonance characteristic when the resonance frequency becomes f ₂ + Δf. At this time, at the output of the intermediate frequency amplifier circuit 327, a level signal proportional to the resonance characteristic of the antenna circuit 320 is obtained. That is, in this case, the level of this output increases as much as the signal gain 345 increases to the signal gain 344. This output is input to the frequency correction data output circuit 323 and compared with the level at the resonance frequency f ₂ stored in advance. If it is larger, the frequency of f ₂ + Δf is selected. If so, the frequency f ₂ is selected. f ₂ + △
When the level of f is large, that is, when the signal gain 344 is increased as in the case of FIG. 16, the frequency correction data output circuit 323 outputs a signal to resonate at a frequency higher by Δf.

In response to this signal, the frequency correction circuit 322
Determines a new DC voltage, applies a DC voltage to the terminal 312, and the antenna circuit 320 has a resonance frequency equal to f ₂ + 2Δf. Then, the intermediate frequency amplifier circuit 32
The level of 7 is compared with the level of the resonance frequency of f ₂ + Δf detected one time before, that is, the level proportional to the signal gain 344 of FIG. The resonance correction frequency is selected by the frequency correction data output circuit 323.

By repeating these series of operations, the intermediate frequency amplifier circuit 32 having a resonance frequency of f ₂ + nΔf (n is an integer)
When the output level of 7 is below the level of f ₂ + (n-1) Δf, the frequency correction data output circuit 323 sets the resonance frequency to f ₂ + (n-1) Δf. Finally, it selects and outputs a signal to the frequency correction circuit 322. And
Upon receiving this signal, the frequency correction circuit 322 outputs the newly set last DC voltage. At the same time, a correction end signal is output to the switch circuit 321. The switch circuit 32l receives the correction end signal, holds the signal for stopping the operation of the frequency correction data output circuit 323 and the last DC voltage of the frequency correction circuit 322, and outputs the signal for stopping the operation. Further, a signal for reactivating the AGC circuit 331 is output and sent to the AGC circuit 331. In this way, the frequency correction operation is completed.

FIG. 19 is a timing chart showing a signal change of the circuit which the antenna circuit of the present invention operates to automatically correct the deviation of the resonance frequency.

The series of work described above is represented in this figure.

Before mounting on the arm, the antenna circuit 320 kept the resonance frequency f ₁ , but in order to fit it on the arm, the arm band connector is cut off. Then, the voltage 3 of the terminal 3l5
46 rises to the power supply voltage. At that time, the antenna circuit 3
The signal gain 350 at the frequency f ₁ of 20 is almost absent because the loop antenna is cut off. Then, next, an arm band is attached to the arm. Then, the voltage 346 of the terminal 3l5 drops to the ground potential. This gives A
In order to stop the GC circuit 331 and to operate the frequency correction data output circuit 323 and the frequency correction circuit 322, a signal 347 for controlling them rises to the power supply voltage.

When the frequency correction data output circuit 323 outputs the correction signal 348Δf, the frequency correction circuit 322
Causes the DC voltage 349 to increase a little in order to change the resonance frequency from f ₂ to f ₂ + Δf. Then, the signal gain 350 at the frequency f ₁ of the antenna circuit 320 also slightly increases, and the signal 351 level of the intermediate frequency amplifier circuit 327 also slightly increases. At this time, since the AGC circuit 331 is stopped, it is proportional to the signal gain 350 level at the frequency f ₁ of the antenna circuit 320.

Since the signal 351 level of the intermediate frequency amplifier circuit 327 has increased, the frequency correction data output circuit 323 is
The correction signal 3482Δf is output to change the resonance frequency to f ₂ + 2Δf for the next correction.

By repeating these steps, nΔf at which the output signal 351 of the intermediate frequency amplifier circuit 327 becomes maximum is searched for.

In FIG. 19, after the 6Δf correction, the signal 35l level of the intermediate frequency amplifying circuit 327 dropped for the first time. Therefore, the frequency correction data is output in order to change the resonance frequency to f ₂ + 5Δf, which is one level before. The circuit 323 outputs the correction signal 3485Δf and sends the signal 3 to the switch circuit 321.
52 manpower. Detect the trigger pulse of signal 352,
Frequency correction data output circuit 323 and frequency correction circuit 3
The signal 347 controlling 22 falls, and the frequency correction circuit 322 holds the DC voltage 349 when f ₂ + 5Δf and stops. At the same time, the signal 347 that controls the AGC circuit 331 also falls, and the AGC circuit 331 restarts. Then, the signal level of the intermediate frequency amplifier circuit 327 returns to the level before the series of 351 correction operations, and the correction operation ends.

As described above, the tuning frequency of the antenna circuit 320 when worn on the arm is f ₂ + (n-1) Δf
Therefore, if Δf is made small, the frequency f ₁ when not worn on the arm approaches as close as possible. For Af, an appropriate value may be selected according to the resonance characteristic of the antenna circuit. That is, the frequency difference Δf corrected at one time is determined in consideration of the correction accuracy and the time required for the correction.

An algorithm for obtaining the resonance frequency that maximizes the output signal 35l level of the intermediate frequency amplifier circuit 327 during the correction operation is a so-called method for obtaining the maximum value of data executed by a computer. It is possible to use any of them.

In this way, the resonance frequency f ₂ when worn on the arm and the frequency f ₁ when not worn on the arm can be corrected. All of these operations are performed by one's own work, and the user can correct the resonance frequency without any trouble.

Also, the receiving sensitivity is the same as when it is worn on the arm.
When it is not, the difference due to the frequency shift can be eliminated.

[0107]

As described above, according to the antenna circuit of the present invention, depending on the length of the loop antenna, that is, the thickness of the arm of the person who wears it, or when it is worn on the arm and when not. Then, in order to prevent the resonance frequency of the antenna circuit from changing, the deviation of the resonance frequency is automatically compensated, and it is possible to always tune to a constant frequency.

Also, in the arm-mounted type wireless device with such an antenna circuit attached, even when the thickness of the arm of the person who wears it changes and the length of the arm band changes, or when the wireless device is attached to the arm. Even when it is not, it is possible to automatically receive a constant frequency signal stably with a constant sensitivity without special adjustment.

[Brief description of drawings]

FIG. 1 is an embodiment diagram showing a connector portion of a loop antenna of an antenna circuit of the present invention.

FIG. 2 is an equivalent circuit diagram of the antenna circuit of the present invention.

FIG. 3 is a diagram showing a relationship between an area A (Δα) and a change amount Δα of the length of the loop antenna.

FIG. 4 is a side view of FIG.

FIG. 5 is an embodiment diagram showing a connector portion of a loop antenna of the antenna circuit of the present invention.

FIG. 6 is a diagram of FIG. 5 viewed from diagonally above.

FIG. 7 is a diagram showing an embodiment in which the antenna circuit of the present invention is applied to a wrist-worn radio device.

FIG. 8 is a diagram showing an embodiment of an antenna circuit of the present invention.

FIG. 9 is a diagram showing an example of a conventional antenna circuit.

FIG. 10 is a diagram showing the resonance characteristic of the antenna circuit when the length of the loop antenna is long.

FIG. 11 is a diagram showing the resonance characteristic of the antenna circuit when the length of the loop antenna is short.

FIG. 12 is a diagram for explaining the mechanism of the variable resistance in the connector section when the antenna circuit of the present invention is applied to a wrist-worn radio device.

FIG. 13 is a vertical sectional view of a connector portion.

FIG. 14 is a diagram showing an embodiment of an antenna circuit of the present invention.

FIG. 15 is a diagram showing an embodiment of an antenna circuit of the present invention.

FIG. 16 is a circuit block diagram showing an embodiment of an arm-mounted wireless device incorporating the antenna circuit of the present invention.

FIG. 17 is a diagram showing the resonance characteristic of the antenna circuit when the arm is not worn and the resonance frequency is f ₁ .

FIG. 18 is a diagram showing the resonance characteristic of the antenna circuit when the resonance frequency becomes f ₂ and f ₂ + Af when worn on the arm.

FIG. 19 is a timing chart showing a signal change of a circuit operated by the antenna circuit of the present invention to automatically correct the deviation of the resonance frequency.

[Explanation of symbols]

10l, 102, arm band 103, ... buckle 104, 106 ... loop antenna 104a, 106a, loop antenna inductance 105, metal plate 107a Electrical coupling capacity of the connector part. 108a ...- Another electrical coupling capacitance forming a resonance circuit. 109a, 109b · Terminals l10 ···· Curve representing A (Δα) 111 ··· Arm band l12 ··· Loop antenna 113 ··· Hair Pari ll4 ··· Radio unit 201, 20la, 201b ··· Loop antenna 202 ··· Connector 203, 209 · · Resistor 204 ··· Variable resistor 205, 207, 210 ··· Capacitor 206 ··· Resonant frequency deviation compensation variable capacitance diode 208 ··· Tuning channel variable capacitance diode 211 ···・ ・ ・ Earth 212, 214 ・ ・ ・ DC voltage application terminal 213 ・ ・ ・ ・ High frequency signal output terminal 220 ・ ・ ・ ・ ・ ・ Hole 22l ・ ・ ・ ・ ・ ・ ・ ・ Resistance plate 222a, 222b ・ Arm Band 223 ...・ ・ ・ Protrusions 224, 225 ・ ・ ・ Metal fittings 226 ・ ・ ・ ・ ・ ・ Shaft 227 ・ ・ ・ ・ ・ ・ ・ ・ Hook 228 ・ ・ ・Variable capacitance diode 232, 233 ... Tuning variable amount diode 234, 235 ... High frequency step choke coil 236, 237 ... Capacitor 238, 239 ... High frequency signal output terminal 301 .. Loop antenna 302..connector 303,307,310 ... resistor 304,305,308 ... capacitor 306,309 ... variable capacitance diode 311,312,313,315,303a ..・ ・
... Terminal 314 ... Ground 320 ... Antenna circuit 321 ... Switch circuit 322 ... Frequency correction circuit 323 ...・ ・ ・ Frequency correction data output circuit 324 ・ ・ ・ ・ ・ High-frequency amplifier circuit 325 ・ ・ ・ ・ Local oscillation circuit 326 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Mixing circuit 327 ・ ・ ・Frequency amplification circuit 328 ··· Detection circuit 329 ··· Regeneration circuit 330 ··· Channel selection circuit 331 ···· AGC circuit 340, 342, 343 · ...... resonance characteristics 34l ....... signal gain 344 ....... arm resonance frequency when mounting when the arm is not mounted in the resonance frequency f ₁ is f ₂ + △
Signal gain at f 345 ···················· When worn on the wrist, signal gain at resonance frequency f ₂ 346 ···· Terminal 3l5 DC voltage 347 ··· AGC A signal for controlling the circuit 331, the frequency correction circuit 322, and the frequency correction data output circuit 323 .....
Output signal 349 ... Frequency correction data output circuit 322
Output voltage 350 ... The frequency of the antenna circuit 320 is f
Signal gain when ₁ is 351 ..... Signal of intermediate frequency amplifier circuit 327 ..... Frequency correction data output circuit 323
Is a signal for controlling the switch circuit 32l 353 ..... Time interval in which the antenna circuit 320 maintains the resonance frequency indicated by each

Claims (4)

[Claims] 1. An antenna circuit in which a loop antenna integrated with an arm band for mounting on an arm and a first variable capacitance diode connected to the loop antenna resonate at a specific frequency, A second variable capacitance diode connected to the antenna circuit, and a DC voltage applied to the second variable capacitance diode for changing the capacitance of the second variable capacitance diode at any time according to the length of the loop antenna. An antenna circuit, comprising: 2. A wrist-worn radio device comprising: a loop antenna provided on an arm band; band coupling means for attaching and detaching the arm band to and from the arm; and a capacitive element forming a resonance circuit with the loop antenna. The arm-worn radio device according to claim 1, further comprising control means for controlling the capacitance value of the capacitive element to change to a predetermined value when the loop antenna is worn on the arm and when the arm is not worn. 3. The loop antenna comprises a first loop antenna provided in a first arm band and a second loop antenna provided in a second arm band. The wrist-worn radio device according to claim 2. 4. The band coupling means has a detection means for detecting whether or not the first loop antenna and the second loop antenna are electrically coupled, and the control means comprises: The wrist-worn radio device according to claim 2 or 3, which is controlled by a detection means.