JP2009010907A - Active coil, active coil antenna element, lc resonance circuit, and broadcast receiver employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for enlarging inductance of a coil, inductance of a coil antenna element and antenna induced voltage, and to provide a method for electronically varying the induction voltage. <P>SOLUTION: A current amplifier whose current gain is 0 to <1, input impedance is sufficiently low and output impedance is sufficiently high and a coil or a coil antenna element are connected in parallel with each other. Furthermore, the current gain of the amplifier is electronically controlled to electronically vary inductance of the coil or the coil antenna element and antenna induced voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for increasing the inductance of a coil without using a magnetic material, a method for continuously changing the inductance, and an LC resonance circuit using the method.

  The present invention also relates to a method for increasing the inductance and antenna induced voltage of a coil antenna element without using a magnetic material, a method for continuously varying the same, and an LC resonance circuit using the method.

  Furthermore, the present invention relates to a broadcast receiver using them.

  Conventionally, the inductance of the coil is increased by winding a wire around a magnetic material having a high permeability, and the inductance is changed by mechanically inserting and removing the magnetic material.

  However, this conventional method cannot electronically vary the coil inductance.

  The problem to be solved by the present invention is to solve these problems of conventional coils and coil antennas by electronically processing them.

  The invention according to claim 1 discloses the principle of electronically expanding the inductance of the coil.

  The invention according to claim 2 provides means for realizing the active coil according to claim 1.

  A third aspect of the present invention provides means for continuously varying the inductance of the active coil according to the first and second aspects.

  According to a fourth aspect of the present invention, there is provided an active coil antenna element in which the coil according to the first, second and third aspects is replaced with a coil antenna element to increase its inductance and induced voltage.

  The invention according to claim 5 provides means for realizing an LC resonance circuit by the active coil according to claims 1, 2, and 3, or the active coil antenna element according to claim 4 and a capacitor.

  The invention described in claim 6 provides means for realizing a broadcast receiver using the active coil or active coil antenna element described in claims 1 to 5 and an LC resonance circuit.

  FIG. 1 is a diagram disclosing the principle of increasing the inductance of a coil according to claim 1, wherein 1 is a coil having an inductance L, 2 is a current source that generates a current G times the current flowing through the coil, and 3 is a coil. This is the connection terminal of the current source. Here, G is a value in the range of 0 to less than 1.

In FIG. 1, if the voltage at the terminal 3 is v, and the current flowing through the coil 1 is i.
It is.

If the current value of the current source 2 is G · i, the current flowing from the terminal 3 is
It is.

Therefore, the impedance when looking at the coil and current source side from 3 terminals is
It is.

Substituting Equation 1 into Equation 3
It becomes.

Thus the coil of Figure 1 according to the invention will coil equivalent inductance L _E which is grounded at one end as shown in FIG. here
It is.

  FIG. 2 is a diagram showing means for realizing an active coil having a large inductance of the coil according to claim 2. 1 is a coil having an inductance L, 2 is a current source output of a current amplifier, and 3 is a connection between the coil and the current source. The terminal 4 is a current amplifier having a sufficiently low input impedance, a sufficiently high output impedance, and a current gain G of 0 or more and less than +1.

  Further, in FIG. 2, if the gain G of the current amplifier 4 can be varied within a range of 0 or more and less than +1, the inductance can be varied as shown in Formula 4, and the variable inductance active coil according to claim 3 become.

  FIG. 4 is a diagram showing means for realizing the active coil antenna element according to claim 4 in which the coil antenna element is used instead of the coil in the active coil according to claims 1 and 2, and in this case, the inductance and the antenna induced voltage are shown. Can also be increased.

  In FIG. 4, 1 is a coil antenna element having an inductance L, 2 is a current source output of a current amplifier, 3 is a connection terminal between a coil and a current source, 4 is a sufficiently low input impedance, and a sufficiently high output impedance. A current amplifier with a gain of G, 5 is an antenna induced voltage of a coil antenna element of 1.

If the current induced per unit inductance of a coil antenna element placed in an electromagnetic field space of constant strength is i _A , the induced voltage of the voltage source of the coil antenna element is
It becomes.

When the voltage v of terminal 3 is obtained by the superposition theorem
It becomes.

Substituting Equation 1 into this
Become
It becomes. This is the virtual induced voltage of the active coil antenna.

  Therefore, an equivalent circuit of the active coil antenna element according to claim 4 is as shown in FIG.

  FIG. 6 shows an LC resonance circuit according to claim 5, wherein the active coil according to claims 1, 2, and 3, or an LC resonance circuit composed of the active coil antenna element and capacitor according to claim 4. It is.

The resonance angular frequency in this case is
It is represented by

  Although FIG. 6 shows a parallel resonant circuit, it is also possible to construct a series resonant circuit using the active coil or active coil antenna element of the present invention.

  The active coil or active coil antenna element of the present invention and the LC resonance circuit using the active coil constitute a feedback circuit including an amplifier. The feedback circuit does not operate stably if the phase-to-amplitude characteristic of the loop gain is inappropriate.

  However, the active coil or active coil antenna element of the present invention and the LC resonance circuit using the active coil are proved to operate stably by the Nyquist determination method.

  FIG. 7 is a diagram showing feedback paths of the active coil according to claim 2, the variable inductance active coil according to claim 3, and the active coil antenna element according to claim 4.

In FIG. 7, the transfer function β of 1 return path is
It is.

Therefore, the loop gain including the two amplifiers is
It becomes. If this is represented by a Nyquist trajectory, the black spot in FIG. 8 is obtained.

  From FIG. 8, the Nyquist trajectory does not include the point (1, j0) inside. Therefore, this feedback loop is stable from the Nyquist criterion.

FIG. 9 is a diagram showing a feedback path of the LC resonance circuit according to the fifth aspect. If the resonance impedance of the resonance circuit is R, the transfer function β of one feedback path is
It is. Here, the index Q indicating the goodness of the resonance angular frequency and the resonance circuit is
It is.

Therefore, the loop gain is
It becomes. This is represented by a Nyquist locus as shown in FIG.

  From FIG. 10, the Nyquist locus does not include the point (1, j0) inside. Therefore, this feedback loop is stable from the Nyquist criterion.

  If the present invention is used, a small coil can be converted into a coil having a large inductance, so that the degree of freedom in design and mounting can be increased, and the product can be downsized. However, the present invention makes it possible to vary the gain of the current amplifier according to the present invention.

  Furthermore, LC resonance circuits that combine electronically variable inductance coils and capacitors can be applied to a wide variety of electronic devices such as broadcast receivers.

  If a coil antenna element is used instead of a coil, it is possible to obtain an inductance and an antenna induced voltage equivalent to those of a large coil antenna element even if it is small. If this is used for radio-controlled watches, etc., industrial contributions are immeasurable.

  FIG. 11 is a diagram showing an embodiment of the variable inductance type active coil according to the third aspect, wherein 1 is a coil.

  2 is a variable gain type current amplifier, 20 is a variable gain control terminal of the current amplifier, 21 is a reference voltage, 22 is a feedback amplifier combined with 23 transistors, 24 is a constant current source, 25 is a differential circuit, and 26 and 27 are This is a current mirror circuit.

  3 is a bias current control circuit, 32 is a feedback amplifier combined with 33 transistors, 34 is a constant current source, 35 is a differential circuit, and 36 is a current mirror circuit.

  In the present embodiment, the gain of the current amplifier is changed by the control voltage applied to the terminal 20, and the equivalent inductance of the coil is changed accordingly.

  The bias current and signal current of each part are as shown in FIG. 11. Even if the gain of the current amplifier is changed, the terminal voltage of the coil is always kept at the reference voltage, and only the signal current flows through the coil.

  Therefore, the consistency of each element such as 25 and 35 differential circuits is strongly required.

  Further, if one coil is changed to a coil antenna element, an embodiment of the active coil antenna element according to claim 4 is obtained.

  FIG. 12 is a diagram showing an embodiment of the LC resonance circuit according to claim 5, wherein 1 is a coil, 2 is a variable gain current amplifier, 3 is a bias current control circuit, and 4 is a capacitor.

  In this case, the resonance frequency can be changed by the control voltage applied to the terminal 20.

  The active coil according to claims 1 and 2 can be realized in a small size and with a large inductance. These coils can be used for downsizing of the equipment and contribute to industrial development.

  The variable inductance type active coil according to claim 3 can be formed into a variable inductance type chip coil by combining a chip coil and an amplifier, and further changing the gain of the amplifier, and the possibility of developing a new component is expected. Is.

  The active coil antenna element according to the fourth aspect has very high industrial applicability for small portable devices such as radio wave watches.

  The variable inductance LC resonance circuit according to the invention of claim 5 can be used for an RF tuning circuit, an IF tuning circuit, a local oscillation circuit and the like of a broadcast receiver.

  FIG. 13 is a diagram showing an embodiment of a radio wave watch receiver according to claim 6, wherein 1 is an active coil antenna resonance circuit according to claim 5, and 2 is a receiver. An accessory drive signal is issued based on the received signal, and the second, minute, hour, day, and month display motors are driven.

  The figure which shows the principle of the active coil of Claim 1.   The figure which shows the active coil of Claim 2.   The equivalent circuit diagram of the active coil of Claim 1 and 2.   The figure which shows the active coil antenna element of Claim 4.   The equivalent circuit diagram of the active coil antenna element of Claim 4.   The figure which shows LC resonance circuit diagram of Claim 5.   The figure which shows the return path of the active coil of Claim 2, 3 and 4.   The figure which shows a Nyquist locus | trajectory.   The figure which shows the feedback path of LC resonance circuit of Claim 5   The figure which shows a Nyquist locus | trajectory.   The figure which shows the Example of LC resonance circuit of Claim 1, 2, 3 and 4.   The figure which shows the Example of LC resonance circuit of Claim 5.   The figure which shows the Example of the radio wave watch of Claim 6.

Claims (6)

  An active coil, wherein a coil and a current source are connected in parallel, and a current value of the current source is set to a value in a range of 0 to less than 1 times a current value flowing through the coil.   An active coil comprising a current amplifier and a coil connected in parallel with a current gain of 0 or more and less than +1, a sufficiently low input impedance, and a sufficiently high output impedance.   3. An active coil according to claim 1, wherein the current of the current source is variable.   4. The active coil antenna element according to claim 1, wherein a coil antenna element is used.   4. An LC resonance circuit comprising the active coil according to claim 1, 2, or 3, or the active coil antenna element according to claim 4 and a capacitor.   A broadcasting receiver using the invention according to any one of claims 1 to 5.