JP2830095B2 - Antenna circuit and wrist-mounted radio - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a small portable wireless device, in particular, an antenna circuit,
The present invention relates to an arm-mounted wireless device using the same.

[Conventional technology]

2. Description of the Related Art Conventionally, there is an example in which an antenna circuit of a portable small wireless device is provided with a variable capacitance diode in order to eliminate variation in resonance frequency of the antenna circuit during mass production.

However, in this case, once the resonance frequency is adjusted by the variable capacitance diode, the resonance frequency does not deviate thereafter, so that the variable capacitance diode is used in a passive manner.

On the other hand, in a small wireless device capable of continuously receiving a certain frequency range, a variable capacitance diode is used because the resonance frequency of the antenna circuit needs to be continuously changed. However, it is not used for the purpose of correction when the resonance frequency of the antenna circuit shifts for some reason, and the frequency hardly shifts.

Furthermore, AFC (A
uto Frequency Control) circuit system, which also uses a variable capacitance diode to correct the deviation of the transmission and reception frequency. This is to correct the oscillation frequency of the local oscillator in the superheterodyne system. Is different from

[Problems to be solved by the invention]

INDUSTRIAL APPLICABILITY The present invention is applied to an antenna circuit having a loop antenna integrated with an arm band to be worn on an arm, and an arm-mounted wireless device.

That is, since the loop antenna is mounted so that the arm orbits around, the length of the loop antenna differs depending on the individual who uses the loop antenna. Then, since the value of the inductance of the loop antenna differs depending on the individual, the resonance frequency of the antenna circuit varies depending on the individual, and the gain of the loop antenna varies. this is,
Affecting the sensitivity of each person's radio, and remarkably, if the resonance frequency is shifted, there is a possibility that transmission and reception cannot be performed.

Since these are phenomena caused by the shift of the resonance frequency of the antenna circuit, it is sufficient to return to the original resonance frequency. However, it is very troublesome for the user of the loop antenna to manually perform this operation. Realistic.

Therefore, an object of the present invention is to provide an antenna circuit that can automatically correct the deviation of the resonance frequency of the antenna circuit and always maintain the resonance frequency at a constant frequency.

Further, the wrist-mounted wireless device of the present invention equipped with such an antenna circuit can always transmit and receive at a constant sensitivity irrespective of the thickness of the arm of the individual who uses the device.

[Means for solving the problem]

In order to solve the above-described problems, the antenna circuit of the present invention includes:
A first metal plate loop antenna provided on a first arm band, a second metal plate loop antenna provided on a second arm band, the first arm band and the second arm band; And a coupling means for coupling the first metal plate loop antenna when the arm is worn, wherein the end of the first metal plate loop antenna on the coupling means side is the end of the second metal plate loop antenna on the coupling means side. And the first metal plate loop antenna has an end on the coupling means side,
It is characterized in that the tip has a shape that becomes thinner.

Further, the wrist-mounted wireless device of the present invention includes a first metal plate loop antenna provided on the first arm band, a second metal plate loop antenna provided on the second arm band, A coupling means for coupling the first arm band and the second arm band when already worn, wherein the end of the first metal plate loop antenna on the coupling means side is The second metal plate loop antenna is capacitively coupled with the end on the coupling means side, and the end of the first metal plate loop antenna on the coupling means side has a shape whose tip becomes thin. It is characterized by the following.

Further, the wrist-mounted radio of the present invention has a wrist-mounted radio having an antenna circuit in which a loop antenna integrated with the wristband and a capacitive element connected to the loop antenna resonate at a specific frequency. In the wireless device, a part of the wristband can be cut off together with the loop antenna to be worn on an arm, and a connector part that can be connected by changing the wearing length of the wristband is provided. Is configured to form an electrical coupling capacitance that electrically couples between the disconnecting portions of the loop antenna in the connected state, and the electrical coupling capacitance is a value of the connector portion accompanying the change in the mounting length. It changes in accordance with a change in the connection mode, and compensates for a change in the length of the loop antenna due to a change in the mounting length, and holds the resonance frequency of the loop antenna. Characterized in that it is configured urchin.

(Operation)

As described above, it is an object of the present invention to automatically correct a change in resonance frequency caused by a change in the inductance value of the loop antenna depending on the thickness of the arm and whether the arm is worn or not. It is in. As a means for this, an electric coupling capacitance is included in a connector attached to the loop antenna, and these electric coupling capacitances are automatically changed. Generally, as the length of the loop antenna increases, the inductance increases, so that the amount of electric coupling solution is reduced. Conversely, when the loop antenna is shortened, the inductance is reduced, so that the electric coupling capacity is increased. With such a change, the resonance frequency can be kept constant.

〔Example〕

FIG. 1 shows an example in which, in the present invention, an antenna circuit for providing an electrical coupling capacitance to a connector portion of a loop antenna is applied to a wristwatch band and a connector. Arm bands 101,10
2 are made of insulating material such as synthetic leather,
Connected with 03. A metal plate 105 is attached to the buckle 103. The metal plate 105 is attached to the middle of the buckle 103 so as to cross the arm band 102, and has a sufficiently large area compared to the area of the buckle 103 viewed from the surface as shown in the figure. Further, the metal plate 105 is connected to the loop antenna 106 included in the arm band 101 from the back. The loop antennas 104 and 106 are made of a conductor such as copper.

The width of the loop antenna 104 inside the wristband 102 becomes narrower toward the end of the wristband 102. In the case of a person with a thin arm, the surplus portion of the arm band 102 increases. In other words, the arm orbital length of the arm bands 101 and 102 is reduced, but the area where the metal plate 105 and the loop antenna 104 overlap is increased. An electric coupling capacity is generated in the overlapping portion, and the electric coupling capacity in this case becomes large.

Conversely, in the case of a person with a thick arm, the surplus portion of the arm band 102 is reduced. In other words, the arm orbital length of the arm bands 101 and 102 becomes longer, but the overlapping area of the metal plate 105 and the loop antenna 104 becomes smaller.

 In this case, the electric coupling capacity becomes small.

It should be noted that the loop antenna 104 included in the arm band does not function as an antenna at a more distal end portion than the metal plate 105.
Therefore, the meaning that the loop antenna is long means that a portion on the opposite side from the tip of the loop antenna 104 from the position of the metal plate 105 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. Further, there are an electric coupling capacitance 107a formed by the metal plate 105 and the loop antenna 104 overlapping each other, and another electric coupling capacitance 108a forming a resonance circuit.

The electric coupling capacitance 108a may be a fixed capacitance or a variable capacitance obtained by combining a variable capacitance diode and a fixed capacitance. A high-frequency signal is extracted using one or both terminals 109a and 109b of the capacitor 108a.

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

If these are expressed by equations, the inductances 140a, 106
a is L _104a , L _106a , and the electric coupling capacity 107a, 108a is C _107a , C
_108a , if the resonance frequency is f, The relationship holds. To make f a constant value, (L _104a + L _106a ) · C _total = C _oustant (Equation 3) may be used.

The value of the electrical coupling capacitance 107a that compensates for the change in the inductances 104a and 106a when the lengths of the loop antennas 104 and 106 are slightly shortened is theoretically obtained while maintaining the relationship of Equation 3.

The inductances 104a and 106a are connected at a high frequency by the buckle 103 and become one inductance.

Assuming that the value of this inductance is L _total , L _total = K _uo SN ² / l = (= L _104a + L _106a ) (Equation 4).

Where K is the Nagaoka coefficient, μo is the magnetic permeability in vacuum,
S is the opening area after connecting the loop antennas 104 and 106 with the buckle 103, N is the number of turns of the loop antenna, and l is the width of the loop antenna. The opening area S of the loop antenna is as follows: S = πa ² (Equation 5), where the opening is a circle and the radius is a. Now, assuming that the length of the loop antenna is slightly shortened, and if the shortened amount is Δα, the opening area S ′ at this time is By substituting Equation (6) into Equation (4), L _total when the length of the loop antenna is shortened can be obtained.

Before the loop antenna becomes short, the ratio of the value of L _total is proportional to the ratio of the opening area S, and the ratio ΔL _total is According to equation (7), when Δα increases, ΔL _total becomes 1
It can be seen that the value of L _total becomes smaller than that when Δα = 0, that is, the length of the loop antenna is not changed.

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

Σ is the dielectric constant of the substance, A is the loop antenna 104,
The area of the portion that overlaps the metal plate 105, d, is the distance between both metal surface windings. Σ is determined from the material of the arm band 102 covering the loop antenna 104 and the dielectric constant of the smiling space between the back surface of the arm band 102 and the metal plate 105.

Here, _assuming that C _108a >> C _107a , the electric coupling capacitance affecting the resonance frequency of the resonance circuit in FIG. 2 can be approximated by C _107a . Therefore, C _total ÷ C _107a (Equation 9) As shown in Equations 3 and 4, the product of L _total and C _total needs to be constant. Therefore, the value of ΔL _total when the loop antenna is shortened obtained by equation (7) is C _total
May be compensated by the change ratio ΔC _total . By transforming equation (3) and expressing the meaning by an equation, L _total · ΔL _total · C _total · ΔC _total = Constant (Equation 10) ΔL _total · ΔC _total = 1 (Equation 11) Equations 11 and 7 From the equation, the ratio of change in the value of ΔC _total is Becomes From Expressions 8 and 9, the value of ΔC _total is replaced with the amount of change in the area A of the electric coupling capacitance C _107a . Therefore, considering the area A as a function of Δα, Becomes β is the area when Δα = 0. When Δα increases, that is, when the length of the loop antenna decreases, the value of A (Δα) increases, and the value of _C107a increases. Therefore, it is possible to compensate for the ratio [Delta] L _total of the change in L _total.

FIG. 3 is a view showing the surface of Equation 13, where − <Δα <2.
By changing A (Δα) in the range of πa, Δ
L _total can be compensated. The width of the loop antenna 104 shown in FIG. 1 becomes narrower toward the tip, but the width should be determined so that the area where the loop antenna 104 and the metal plate 105 overlap obeys the equation (13). I just need.

On the other hand, if C _108a >> C _107a does not hold, C _total
It is necessary to consider the value of C _108a , but even in this case, although the expression of A (Δα) includes C _108a , it is obtained by theoretical calculation, and according to the function, the loop antenna 104a is obtained.
What is necessary is just to decide the width.

In this way, when the length of the loop antenna changes by Δα, A (Δα) is automatically determined, and the compensated electric coupling capacitance C _107a is determined. C _107a determined in this way is L when the length of the loop antenna is shortened.
_{Although a} co-propulsion circuit is formed together with the _total , the resonance frequency does not change as compared with before reducing the length of the loop antenna. Thus, the object of the present invention is achieved.

In other words, in the case of a person with a thin arm, an arm band that goes around the arm
The loop lengths of the loop antennas 104 and 106 included in 101 and 102 are reduced, and the inductances 104a and 106a are reduced, but the area where the metal plate 105 and the loop antenna 104 overlap is increased, and the capacitance 107a is increased. The decrease in the inductances 104a and 106a is supplemented by the capacitance 107a, and the inductances 104a and 106a and the capacitances 107a and 10
The product of the reciprocals of the sum of the reciprocals of 8a is constant.

In the case of a person with a thick arm, the loop length of the loop antennas 104 and 106 becomes longer, and the inductances 104a and 106a become larger, but the capacitance 107a becomes smaller. The increase in the inductances 104a and 106a is offset by the capacitance 107a, and the product of the reciprocal of the sum of the reciprocals of the inductances 104a and 106a and the capacitances 107a and 108a is constant.

FIG. 4 is a side view of the buckle portion of FIG. 1;
Since the arm band 102 is merely inserted between the buckle 103 and the metal plate 105, attachment and detachment is easy. Also, the buckle 103 presses the arm band 102 at two places, so that it does not easily come off even if the band 102 is pulled from both sides.

FIG. 5 is a cross-sectional view of an arm band using the same antenna circuit as in FIG. A loop antenna 112 is included inside the arm band 111. A large number of bristles 113 for connecting both arm bands are attached. Hair 1
13 allows both arm bands to be overlapped and connected at any position. Then, when overlapping, if the circumference of the arm band 111 is shortened, the loop antenna 1
The overlapping area of the twelve becomes large and has a large capacitance at that part. On the other hand, if the loop length of the arm band 111 is increased, the overlapping area of the loop antenna 112 is reduced, so that the capacitance of that portion is reduced.

FIG. 6 is a view of the embodiment of FIG. 5 as viewed obliquely from above. Also in this case, the electrical equivalent circuit is the same as that of FIG. 2. If the length of the loop antenna 112 changes, the overlapping area of the loop antenna 112 changes automatically, and the electrical coupling capacitance 107a changes. The resonance frequency can always be kept constant.

The narrow portion of the width of the loop antenna 112 may be determined so as to satisfy Expression 13.

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

FIG. 8 is an antenna circuit diagram of the present invention in which a variable capacitance diode is attached to a conventional antenna circuit. FIG. 9 is an example of an antenna circuit conventionally used.
The embodiment shown in FIG. 8 also shows an embodiment that suppresses a change in resonance frequency due to a change in the length of the loop antenna.

The loop antenna 201 can be attached and detached at the connector 202.Electrically, by connecting the connector 202, the loop antenna 201 is configured, and the loop antenna 201 and the variable resistor 204 are connected. Will be. The variable resistor 204 determines the DC voltage of the variable capacitance diode 206 together with the resistor 203. A power supply voltage is supplied from a terminal 212. This power supply is a power supply that always generates a constant voltage. And loop antenna 201
Are grounded by a ground 211. Therefore, the voltage applied to the variable capacitance diode 206 is determined by the resistance ratio between the resistor 203 and the variable resistor 204. In addition, variable resistor 204
Is changed, the voltage applied to the variable capacitance 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 hundreds of kΩ, Q as a resonance circuit of the antenna circuit including the loop antenna 201 is not reduced, and the sensitivity of the antenna circuit is not reduced.

The capacitors 205, 207, and 210 are for DC cutoff.

The variable-capacitance diode 208 is originally used for tuning. Terminal 2
From 14, a DC voltage for channel selection is applied via a resistor 209. Conventionally, as shown in FIG.
That is, an antenna circuit is configured by the 208, the capacitor 207, and the loop antenna 201. This variable capacitance diode 208 eliminates variations in the resonance frequency of the antenna circuit when the antenna circuit always resonates at the same frequency or, if there is no variation, can be replaced with a simple capacitor. .

An object of the present invention is to automatically compensate for a shift in resonance frequency when the length of a loop antenna changes. Therefore, as an antenna circuit that achieves the object, a variable capacitance diode 206 is included therein. There is a great feature in adding.

FIG. 10 is a diagram showing the resonance characteristics of the antenna circuit when the length of the loop antenna 201 is long using a conventionally used antenna circuit as shown in FIG. 9, and FIG.
FIG. 8 is a diagram illustrating resonance characteristics when the length of the loop antenna 201 is short.

When the length of the loop antenna 201 is long, the inductance of the loop antenna 201 increases, so that the low frequency f ₁
Of the transmitting stations. Therefore, loop antenna 201
If you reduce the length of, the inductance thereof to become smaller, the sensitivity of the transmission station f ₁ which has been received until now is decreased, behalf increases or the sensitivity of f ₂ transmission station in the high frequencies. That is, the tuning deviation occurred because the length of the loop antenna 201 was changed.

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

In Figure 11, the inductance by the amount of shortening the loop antenna 201 is reduced, in order to keep the coming maximum sensitivity to frequencies f _1, increases the capacitance of the variable capacitance diode 206. In order to increase the capacity of the variable capacitance diode 206, the DC voltage applied to the cathode side is reduced.
To reduce the DC voltage, the variable resistor 204 may be reduced. The variable resistor 204 includes a connector 202 and a resistor plate 221 formed inside the arm band.
In this way, even with a shorter loop antenna 201, it is possible to maintain the frequency f _1. Regarding the value of the resistance plate 221, since this value is used to compensate for the increase or decrease of the inductance, ΔC _{total of} Expression 12 can be used as a capacity for compensating the change ΔL _total of the inductance. 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
Therefore, the value of the variable capacitance diode 206 may be changed at any time such that the amount of change of C _total follows Expression 12. In other words, it is only necessary to apply a DC voltage appropriate to the variable capacitance diode 206. It also means that the necessary resistors need to be installed.

FIG. 12 is a diagram showing the structure of the variable resistor 204. The connector 202 connects the loop antennas 201a and 201b included in the arm bands 222a and 222b. The arm band 222a on the side where the loop antenna 201a is located further includes a resistance plate 221. In the resistance plate 221, sections each having a different resistance value are continuously connected, and each of the resistance plates 221 is provided with a hole 220 capable of electrically conducting. These holes 220 have a structure penetrating from the front surface to the back surface of the arm band. One of the holes 220 is connected to a protrusion inside the connector 202 and is connected to the loop antenna 201b.

FIG. 13 is a longitudinal sectional view of the connector 202. At the end of the loop antenna 201b, a bracket 224 and the loop antenna 201
A metal fitting 225 is attached in the middle of the arm band 222a having a. The metal fittings 224 and 225 are electrically connected to the loop antennas 201a and 210b, and a shaft 226, a hook 227, and a holding metal 228 are used for coupling the two. It is crimped by these three metal fittings, and the loop antenna 201a, 201
b is joined.

Now, the metal fitting 224 has a projection 223. This is an arm band
It is inserted into one of the holes 220 provided on one side of 222a. Hole 2
Reference numeral 20 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 conduction. Thus, the resistance plate 221, the metal fitting 224, and the loop antenna 201 b
Is connected.

When the length of the loop antenna 201 becomes longer, the protrusion 223 is inserted into the hole 220 on the tip end side of the loop antenna 201a. Then, since the length of the resistance plate 211 is increased, the resistance between the projection 223 and the variable capacitance diode 206 increases. Therefore, the voltage applied to the cathode of the variable capacitance diode 206 increases, and the capacitance decreases in a form that compensates for the increase in the inductance of the loop antenna 201. As a result, no tuning deviation occurs, and a certain sensitivity is obtained. Can be kept.

Conversely, if the loop antenna 201 becomes shorter, it is inserted into the hole 220 of the loop antenna 201a on the wireless device main body side, so that the resistor plate 221 is used shorter, the applied voltage decreases, and the loop antenna 201 By compensating for the decrease in inductance, the capacitance of the variable capacitance diode 206 is increased, and tuning deviation can be prevented.

Thus, using the antenna circuit of the present invention, even if the length of the arm band integrated with the loop antenna is changed,
Since the tuning deviation is automatically compensated, the sensitivity can always be kept constant.

Further, it is needless to say 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 of the present invention in which a variable capacitance diode is attached to a conventional antenna circuit.
The configuration is different from the embodiment of FIG. In FIG. 15,
When the loop antenna is worn on the arm and when it is not,
One embodiment is shown for automatically compensating for a shift in the resonance frequency of the antenna circuit.

The loop antenna 301 can be attached and detached at the connector 302. At the same time, the connector 302 serves as a switch for connecting the loop antenna 301 side and the capacitor 304 with each other in a direct current manner. The connector 302 may be located at any position of the loop antenna 301. A DC voltage is supplied from a terminal 303a via a resistor 303. Terminal 315 is a terminal for monitoring a DC voltage. The capacitor 305 and the variable capacitance diode 306 connected in series are capacitors provided so that the radio device can tune to a target frequency. In other words, it is a tuning capacitor. Then, a DC voltage for channel selection is applied from the terminal 311 via the resistor 307, and the capacitance of the variable capacitance diode is determined.

Now, the characteristics of the antenna circuit of the present invention are as described above.
Aside from the variable capacitance diode 306 for tuning, a variable capacitance diode 309 and a capacitor 30 connected in series with the variable capacitance diode 309 are provided.
8. The point is that a resistor 310 for applying a DC voltage and a terminal 312 are further provided.

First, when the loop antenna 301 does not go around the arm, the tuning capacitor 305 and the variable capacitance diode 3
It is assumed that tuning is achieved by configuring a resonance circuit with the loop antenna 301 using the 06. In this state, the loop antenna 301 is cut off at the connector 302, and this time, the loop antenna 301 is
Suppose you connect to 02.

Then, due to the effect of the arm of the human body, the loop antenna 301
Of the antenna circuit changes, and the resonance frequency of the antenna circuit is shifted as compared with the case where the arm does not go around. Therefore, by changing the DC voltage applied to the variable capacitance diode 309, the capacitance of the capacitor connected in parallel to the loop antenna 301 is equivalently changed, and the antenna circuit is set to the resonance frequency when the original arm does not go around. Retune. Thus, the sensitivity of the wireless device can be stably maintained without a shift in the resonance frequency due to the influence of the arm. Needless to say, even if the user goes around the arm first and removes it from the arm, these operations can correct the deviation of the resonance frequency.

The high frequency signal of the wireless device is amplified by a high frequency circuit connected to 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 passes through the antenna circuit 320 of the present invention, is amplified by the high-frequency amplifier circuit 324, is mixed with the signal from the local oscillation circuit 325, and is converted to an intermediate frequency. Further, the signal is detected by the detection circuit 328 via the amplification circuit 327, and the demodulated signal is processed by the reproduction circuit 329 to obtain various information signals.

For example, it is assumed that the user does not wear the arm at first.
In this state, the DC voltage from the tuning circuit 330 is applied to the terminal 3
Is applied to 11, is tuned to a certain frequency f _1, it is receiving the high frequency signal. Then, at the output of the intermediate frequency amplifier circuit 327, A is used to adjust the gain of the high frequency amplifier circuit 324.
The GC circuit 331 is connected. 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 resonance characteristics of the antenna circuit in this state. At the highest frequency of the resonance characteristic 340, there is a signal spectrum 341.

Now, it is assumed that the connector 302 is cut off and the loop antenna 301 is cut off from the antenna circuit 320 by DC. Then, the voltage of the terminal 315 rises from the ground potential to the power supply potential. Then, this time, the loop antenna 301 to be attached to the arm is in a state of orbiting 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 321, when the terminal 315 becomes the ground potential, a signal for stopping the operation of the AGC circuit 331 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 32. 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.

In this case, the frequency correction data output circuit 323, with respect to the frequency f ₂ which is currently resonance, micro frequency Δf component only, and outputs a signal so as to shift the resonance frequency.

In response to 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 resonance characteristics when the resonance frequency becomes f ₂ + Δf. At this time, the intermediate frequency amplifying circuit 327
, A signal having a level proportional to the resonance characteristic of the antenna circuit 320 is obtained. That is, in this case, the signal gain is 345
However, as the signal gain 344 increases, the level of this output increases. The current force is previously inputted to the frequency correction data output circuit 323 is compared with the level at the resonance frequency f ₂ that has been stored, if large, f ₂ + delta
The frequency of f is selected. Smaller, the frequency of f ₂ is selected. When the level of f ₂ + Δf is large, that is, when the signal gain is increased to 344 as shown in FIG. 18, 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 newly determines the DC voltage and
12, a DC voltage is applied to the antenna circuit 320, and f ₂ + 2Δ
The resonance frequency matches f. Then, the level of the intermediate frequency amplifying circuit 327 is set to f
The level of the resonance frequency of ₂ + Δf, that is, the level proportional to the signal gain 344 in FIG. 18, is compared.

By repeating these series of operations, the resonance frequency becomes f ₂ + nΔ
When the output level of the intermediate frequency amplification circuit 327 at f (n is an integer) is lower than the level at f ₂ + (n−1) Δf, the frequency correction data output circuit 323 sets the resonance frequency to f ₂ + ( n
-1) The frequency correction circuit 322 is finally selected as Δf.
Output the signal. Then, upon receiving this signal, the frequency correction circuit 322 outputs the newly set final DC voltage. At the same time, it outputs a correction end signal to the switch circuit 321. The switch circuit 321 receives the correction end signal, and outputs a signal for stopping the operation of the frequency correction data output circuit 323 and the last DC voltage of the frequency correction circuit 322 to stop the operation. Further, a signal for restarting the AGC circuit 331 is output, and the AGC circuit 331 is output.
Sent to 331. In this way, the frequency correction operation ends.

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

 The series of operations described above is illustrated in this figure.

Arm before putting the antenna circuit 320, which had kept the resonance frequency f _1, in order to fit to the arm, release off connector wrist band. Then, the voltage 346 of the terminal 315 rises to the power supply voltage. At that time, the signal gain 350 at the frequency f ₁ of the antenna circuit 320 is separated from the loop antenna,
rare. Then, an arm band is attached to the arm. Then, the voltage 346 of the terminal 315 decreases to the ground potential. Accordingly, in order to stop the AGC circuit 331 and to operate the frequency correction data output circuit 323 and the frequency correction circuit 322, the signal 347 for controlling them rises to the power supply voltage.

Frequency correction data output circuit 323, and outputs a correction signal 348Derutaf, frequency correction circuit 322, in order to change the resonant frequency from f ₂ to f ₂ + Delta] f. Slightly increase DC voltage 349. Then, the signal gain 350 at the frequency f ₁ of the antenna circuit 320 is slightly increased, and the signal 35 of the intermediate frequency amplifier 327 is increased.
One level increases a little. In this case, since the AGC circuit 331 is stopped, it is not 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 outputs a correction signal to change the resonance frequency to f ₂ + 2Δf for the next correction.
This gives 3482Δf.

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

In FIG. 19, since the level of the signal 351 of the intermediate frequency amplification circuit 327 dropped for the first time after the 6Δf correction,
The frequency correction data output circuit 323 outputs a correction signal 3485Δf in order to change the resonance frequency to f ₂ + 5Δf immediately before,
The signal 352 is input to the switch circuit 321. Trigger pulse of signal 352 is detected, frequency correction data output circuit 323,
The signal 347 for controlling the frequency correction circuit 322 falls, and the frequency correction circuit 322 stops while holding the DC voltage 349 at the time of f ₂ + 5Δf. At the same time, the signal 347 for controlling the AGC circuit 331 falls, and the AGC circuit 331 operates again. Then, the signal level of the intermediate frequency amplifying circuit 327 returns to the level before the 351 series of correction operations, and the correction operation ends.

As described above, the antenna circuit 32 when worn on the arm
The tuning frequency of 0 is f ₂ + (n−1) Δf. If Δf is reduced, the frequency f ₁ approaches the frequency f ₁ when not worn on the arm. An appropriate value of Δf may be selected according to the resonance characteristics of the antenna circuit. That is, the frequency difference Δ to be corrected at one time
f is determined in consideration of the correction accuracy and the time required for the correction.

The algorithm for obtaining the resonance frequency, such as maximizing the level of the output signal 351 of the intermediate frequency amplification circuit 327 during the correction operation, can use any of the so-called methods for obtaining the maximum value of data executed by a computer. It is feasible.

In this way, it corrects the frequency f ₁ when not wearing the resonance frequency f ₂ when mounted on the arm on the arm. All of these operations are performed automatically, and the user can have the resonance frequency corrected without any trouble.

In addition, the difference in reception sensitivity due to a frequency shift between when worn on the arm and when not worn can be eliminated.

〔The invention's effect〕

As described above, the antenna circuit of the present invention automatically adjusts the resonance frequency to prevent the resonance frequency of the antenna circuit from being changed by the length of the loop antenna, that is, the thickness of the arm of the wearer. And can always be tuned to a constant frequency.

In addition, the wrist-mounted radio equipped with such an antenna circuit has a constant frequency automatically without any special adjustment even when the thickness of the wrist of the wearer changes and the length of the wristband changes. Signals can be received stably with a certain sensitivity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an embodiment diagram showing a connector portion of a loop antenna of an antenna circuit according to 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 Δα in length of a loop antenna. FIG. 4 is a view of FIG. 1 as viewed from the side. 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 as viewed obliquely from above. FIG. 7 is a diagram showing an embodiment in which the antenna circuit of the present invention is applied to a wrist-mounted radio. FIG. 8 is a diagram showing an embodiment of the 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 resonance characteristics of the antenna circuit when the length of the loop antenna is long. FIG. 11 is a diagram showing resonance characteristics of the antenna circuit when the length of the loop antenna is short. FIG. 12 is a view for explaining a mechanism of a variable resistor in a connector portion when the antenna circuit of the present invention is applied to a wrist-mounted radio. FIG. 13 is a longitudinal sectional view of a connector section. FIG. 14 is a diagram showing an embodiment of the antenna circuit of the present invention. FIG. 15 is a diagram showing an embodiment of the antenna circuit of the present invention. FIG. 16 is a circuit block diagram showing one embodiment of an arm-mounted radio device incorporating the antenna circuit of the present invention. FIG. 17 is a view showing a resonance characteristic of the antenna circuit when the resonant frequency f ₁ of the arm is not mounted. FIG. 18 is a diagram showing the resonance characteristics of the antenna circuit when the resonance frequency is f ₂ and f ₂ + Δf when the arm is worn. FIG. 19 is a timing chart showing a signal change of a circuit in which the antenna circuit of the present invention operates to automatically correct the resonance frequency shift. 101, 102… arm band 103… buckle 104, 106… loop antenna 104 a, 106 a… inductance of loop antenna 105… metal plate 107 a… electrical junction capacitance of the connector part 108 a… another electrical component that constitutes a resonance circuit Coupling capacity. 109a, 109b terminal 110 curve A (Δα) 111 arm band 112 loop antenna 113 hairs 114 radio body 201, 201a, 201b loop antenna 202 connector 203, 209 … Resistance 204 …… Variable resistance 205,207,210 …… Capacitor 206 …… Resonant frequency deviation compensation variable capacitance diode 208 …… Tuning variable capacitance diode 211 …… Earth 212,214 …… DC voltage application terminal 213 …… High frequency signal output terminal 220 Hole 221 Resistor plate 222a, 222b Arm band 223 Projection 224, 225 Metal fitting 226 Shaft 227 Hook 228 Holder 230, 231 Variable capacitance diode for resonance frequency shift compensation 232, 233 … Tuning variable diodes 234,235… High frequency choke coil 236,237… Capacitor 238,239… High frequency signal output terminal 301… Loop antenna 302… Connector 303,307,310… Resistance 304,305,308… Capacitors 306, 309 Variable capacitance diodes 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 …… Intermediate frequency amplification circuit 328 …… Detection circuit 329 …… Regeneration circuit 330 …… Tuning circuit 331 …… AGC circuit 340,342,343 …… Resonance characteristics 341 …… Resonance frequency when arm is not worn There the signal gain 345 ...... arm is installed when the signal gain 344 ...... arm resonance frequency when wearing f ₂ + Delta] f in the case of f _1, the signal gain 346 ...... terminal 315 DC when the resonance frequency f ₂ Voltage 347: Signal for controlling the AGC circuit 331, frequency correction circuit 322, frequency correction data output circuit 323 348: Output signal of the frequency correction data output circuit 323 349: Output voltage of the frequency correction circuit 322 350: Antenna circuit 320 frequencies Signal gain at f ₁ 351 Signal of intermediate frequency amplifier circuit 327 352 Frequency correction data output circuit 323 is a switch circuit
Signals for controlling 321 353… Time interval in which the antenna circuit 320 keeps the indicated resonance frequency

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01Q 1/24 H01Q 1/44 H01Q 7/00

Claims (3)

(57) [Claims] 1. A first metal plate loop antenna provided on a first arm band, a second metal plate loop antenna provided on a second arm band, the first arm band and the first A coupling means for coupling the second metal band to the second metal plate loop antenna when the second metal band loop antenna is attached to the second metal plate loop antenna. An antenna circuit, which is capacitively coupled to an end of the first metal plate loop antenna, wherein an end of the first metal plate loop antenna on a side of the coupling means has a shape in which a tip becomes thin. 2. A first metal plate loop antenna provided on a first arm band, a second metal plate loop antenna provided on a second arm band, the first arm band and the first And a coupling means for coupling the second metal band to the second metal band loop when the first metal plate loop antenna is connected to the second metal plate loop antenna. The first metal plate loop antenna has an end on the coupling means side which is capacitively coupled with an end on the coupling means side of the first metal plate loop antenna. Type radio. 3. A wrist-worn radio having an antenna circuit in which a loop antenna integrated with an arm band and a capacitive element connected to the loop antenna resonate with respect to a specific frequency. A part of the arm band can be cut off together with the loop antenna, and a connector part which can be connected by changing a mounting length of the arm band is provided. It is configured to form an electric coupling capacitance for electrically coupling between the separated portions of the loop antenna, and the electric coupling capacitance changes in accordance with a change in the connection mode of the connector unit with a change in the mounting length. And configured to compensate for a change in the length of the loop antenna due to a change in the mounting length and to maintain a resonance frequency of the loop antenna. Arm-attached type radio apparatus which is characterized and.