JP2001111388A - Multiple-tuned transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple-turned transformer for uniformly suppressing image frequencies with a wide reception band by a small number of parts and simple circuit constitution. SOLUTION: An antenna turned transformer T1 is arranged at the input side, and a negative load turned transformer T2 is arranged at the output side. In the antenna tuned transformer T1, a primary input coil N1 for impedance matching and a primary tuned coil N2 with a tap (a) for turning are transformer-connected, and a variable capacitative element C and an additional capacitative element C1 are connected in parallel with the primary tuned coil N2 so that a primary resonance circuit can be formed. In the negative load tuned transformer T2, a connected coil N3 with a tap (b) and a secondary tuned coil N4 with a tap (c) are coiled so as to be shared, and the tap (b) is directly connected with the starting part of the winding of the secondary tuned coil N4, and the tap (c) is connected through an additional capacitative element C2 with the starting part of the winding of the connected coil N3. Then, a variable capacitative element C is connected with them so that a secondary resonance circuit can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tuning circuit for selecting a received wave and a trap circuit for suppressing an image interference wave while improving the matching between the antenna impedance and the input impedance of the high-frequency amplifier. The present invention relates to a high-frequency double-tuned transformer of a superheterodyne receiver having a function.

[0002]

The image frequency generated by the frequency conversion is an interference wave unique to the superheterodyne system. This image frequency fim is a frequency which is twice the intermediate frequency fi from the reception wave f1, and is fim = f1 + 2fi in the upper heterodyne system, and fim = f1-2fi in the lower heterodyne system. For example, 28
When receiving the LW band wave of 8 kHz, the intermediate frequency is set to 45.
Assuming that the frequency is 0 kHz, in the case of the upper heterodyne method, a frequency of 288 kHz + 450 kHz × 2 = 1188 kHz becomes the image frequency. Therefore, usually 52
The image frequency enters the MW band wave of 2 kHz to 1710 kHz, which may cause interference.

In order to suppress the image frequency, it is necessary to take measures such as increasing the number of stages of the high-frequency tuning coil and separately providing a trap circuit for the image frequency. However, if the number of stages of the high-frequency tuning coil is increased, the number of variable capacitors and variable capacitance diodes, which are variable capacitance elements constituting the circuit, is increased, thereby increasing the price and complicating the adjustment of the circuit. In addition, when a trap circuit for an image frequency using a fixed capacitance element is separately provided in order to suppress a rise in price, even if a specific image frequency can be removed, an image frequency of a wide reception band that changes according to the reception frequency is used. Cannot be removed by a fixed trap circuit.

Accordingly, an object of the present invention is to provide a double-tuned transformer capable of uniformly suppressing an image frequency in a wide receiving band with as few components as possible and a simple circuit configuration.

[0005]

In order to achieve the above object, the present invention is configured as follows.

That is, the first aspect of the present invention is an antenna tuning transformer having a variable capacitance element connected in parallel with a primary tuning winding having a tap a, a coupling winding having a tap b and a secondary tuning winding having a tap c. In addition to the common winding of the wire, the tap b is connected directly to the beginning of the secondary tuning winding, and the tap c is connected to the beginning of the coupling winding via an additional capacitance element for impedance correction. A load tuning transformer comprising a variable capacitance element connected to each of an input side and an output side; a tap a of a primary tuning winding is connected to the beginning of the winding of the coupling winding; A double-tuned transformer for a superheterodyne receiver, wherein a tap c is connected to an amplifier via a DC blocking additional capacitance element. According to a second aspect of the present invention, the coupling winding and the secondary tuning winding of the load tuning transformer are wound around a plurality of brim drum type ferrite cores having two or more winding grooves while arranging the number of turns and the coupling coefficient. The double-tuned transformer according to claim 1, wherein: The invention according to claim 3 is characterized in that the coupling coefficient between the winding on the winding start side and the secondary tuning winding connected in series via the tap b of the coupling winding is set to 0.1 to 0.7. 2. The double-tuned transformer according to claim 1, wherein: According to a fourth aspect of the present invention, the coupling coefficient of the winding connected in series via the tap c of the secondary tuning winding is set to 0.85 to 1.
2. The double-tuned transformer according to claim 1, wherein the transformer is set to zero. According to a fifth aspect of the present invention, the winding on the winding start side and the secondary tuning winding, which are connected in series via the tap b of the coupling winding, are connected in such a manner that the respective winding starts have the same polarity and the magnetic flux is applied. 2. The double-tuned transformer according to claim 1, wherein an induction circuit is formed.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a double tuning circuit of a superheterodyne receiver embodying the present invention. The double tuning circuit has an antenna tuning transformer T1 on the input side and a load tuning transformer T2 on the output side. Antenna tuning transformer T
Reference numeral 1 denotes a transformer coupling between a primary input winding N1 for impedance matching and a primary tuning winding N2 with a tap a for tuning, and
The variable capacitance element C and the additional capacitance element C1 are connected in parallel with the next tuning winding N2 to form a primary resonance circuit. The load tuning transformer T2 shares a coupling winding N3 with a tap b and a secondary tuning winding N4 with a tap c, and the tap b is directly connected to the beginning of the winding of the secondary tuning winding N4, and the tap c is an additional capacitor. Element C
2 at the beginning of the coupling winding N3. Then, a variable capacitance element C is connected in parallel with these to form a secondary resonance circuit.

The primary input winding N1 has one end connected to a terminal 1 connected to an antenna (not shown) and the other end grounded. The primary input winding N1 may receive the high impedance of the rod antenna and the FET.

The primary tuning winding N2 has windings N21 and N22 connected in series via a tap a, the N22 side is connected to the variable capacitance element C and the additional capacitance element C1, and the N21 side is grounded.

The coupling winding N3 is connected to the winding N through a tap b.
31 and N32 are connected in series, and the start of winding of N32 is set to 2 through the tap a of the primary tuning winding N2 and the additional capacitive element C2.
Connect to the tap c of the next tuning winding N4, and ground the N31 side.

The secondary tuning winding N4 is formed by connecting windings N41 and N42 in series via a tap c, and starting the winding with a coupling winding N
3 and the end of the winding is connected to the variable capacitance element C. The windings N32, N41, and N42 form a mutual induction circuit in which the magnetic fluxes of the windings N32, N41, and N42 are added with the respective winding starts having the same polarity. In order to clarify the polarity of each winding, the starting position of the winding is indicated by a dot in the figure.

The tap c is pulled out from the vicinity of the maximum available power level of the secondary tuning winding N4 while also performing impedance matching with the load circuit, and is connected to an IC amplifier (shown in FIG. No) is connected to terminal 2. Further, it is also connected to the winding start of the coupling winding N3 and the tap a of the primary tuning winding N2 via the additional capacitance element C2. Thereby, the windings N31, N32, N4
1, N42, the additional capacitance element C2, and the variable capacitance element C form a trap circuit for an image frequency. In the figure, the additional capacitance element C2 has one end connected to the tap a (or the beginning of the winding of the coupling winding N3) and the other end connected to the tap c. May be connected to any one point in the secondary tuning winding N4. Also,
In the figure, the winding start of the winding N41 is connected to the tap b, but it may be directly dropped to ground.

The windings N31, N32, N41 and N42 are
As shown in FIG. 2, it is wound around the first groove D1 and the second groove D2 of the three-flange drum core D having the cap core CA. At this time, the number of turns and the degree of interference of the windings N31, N32, N41, and N42 are arranged, and the coupling coefficient between the windings N32 and N4 is set to 0.1.
1 to 0.7, and the coupling coefficient between the windings N41 and N42 is set to 0.85 to 1.0.

The double-tuned circuit embodying the present invention has the above-described configuration, and the input signal applied to the terminal 1 is led to the primary resonance circuit and the secondary resonance circuit, and the specific capacitance is changed by changing the variable capacitance element C. Tune to frequency. At the same time, the image interference wave mixed in the input signal is transmitted to the windings N31, N32, N41, N41.
42, attenuated by a trap circuit including the additional capacitance element C2 and the variable capacitance element C.

When the capacitance of the variable capacitance element C is changed, as shown in FIG. 3, the entire frequency characteristic moves substantially in parallel according to the reception frequency, and the resonance frequency of the trap circuit also moves in parallel within the band. Suppress frequency.

Hereinafter, the reason why the resonance frequency of the trap circuit moves according to the reception frequency will be specifically described. FIG.
In order to make it easy to think of the secondary resonance circuit of the load tuning transformer T2, the circuit is simplified as follows. First, FIG.
As shown in (1), taps b and c are used as a common input and output to make tap c, and the winding N32 of the coupling winding N3 is omitted. As a result, the windings N31 and N41 are replaced with the winding N43, and the windings N43 and N42 are connected in series via the tap c. The impedance of the AC bypass capacitor C 'in the band is almost zero and can be ignored, and the winding N21 is omitted on the assumption that the inductance is infinite. Further, the additional capacitive element C2 is considered for the time being excluded.

When a current flows through the windings N43 and N42, the self-inductances L43 and L42 of the windings N43 and N42 change to L43 'and L42', and the mutual inductance of the windings N43 and N42 becomes M (M > 0)
Then, L43 '= L43 + M L42' = L42 + M. Here, since L43 = L43'-M L42 = L42'-M, the windings N43 and N42 are equivalent to L4
A circuit for connecting -M in series with 3 'and L42' is formed.

As described above, when the circuit of FIG. 4 is replaced with an equivalent circuit and the capacitance of the variable capacitance element C is C,
As shown in FIG. 5, L43 'and L42' +
A parallel circuit of C is connected to form a trap circuit between -M, L43 ', L42', and C between the input signal and the ground circuit.

When the impedance Z of this equivalent circuit is calculated,

(Equation 1) Becomes The frequency at which the impedance Z of this equivalent circuit is maximized (denominator = 0) is the reception frequency f0, and the frequency at which it is minimum (numerator = 0) is the trap resonance frequency f0 '. Therefore, the reception frequency f0 is

(Equation 2) And the resonance frequency f0 'of the trap is

(Equation 3) Becomes

As described above, the double-tuned circuit of the present invention tunes at the receiving frequency f0 where the impedance changes according to the frequency and the reactance of the variable capacitance element C and the windings N31, N41 and N42 becomes equal. Attenuation is given at the resonance frequency f0 'of the trap where the reactance of C becomes equal to the reactance of C or the coupling coefficient K or the number of turns of N42. Therefore, when the variable capacitance element C is changed, as shown in FIG. 3, the entire frequency characteristic moves substantially in parallel according to the reception frequency f0, and at this time, the resonance frequency f0 ′ of the trap also changes in accordance with the change in the variable capacitance element C. To translate. This makes it possible to suppress the image frequency that changes according to the reception frequency f0.

From the calculation formula, since the reactance of the trap circuit is smaller than the reactance of the tuning circuit, the moving width of the resonance frequency f0 'of the trap is small in a low frequency region where the capacitance of the variable capacitance element C is large. In the high frequency region where the capacitance of C is small, the antenna tuning transformer T1
Greatly affects the impedance, and the impedance changes, and the trapping of the image frequency with respect to the reception frequency f0 becomes weak.

Therefore, as shown in FIG. 1, an additional capacitance element C2 for impedance correction is connected in parallel with the windings N32 and N41. Thereby, the impedance of the tuning circuit can be corrected to make the attenuation band of the trap close to the image frequency.

When the additional capacitance element C2 is added, the reception frequency f0 of the load tuning transformer T2 moves to a slightly lower frequency, and accordingly, the reception frequency f0 of the antenna tuning transformer T1 is also lowered accordingly. to add. When the capacitance of the additional capacitance element C2 is small, the reception frequency f0 hardly changes.
May not be added. Further, depending on the degree of influence of the coupling of the antenna tuning transformer T1, the additional capacitance element C2 may not be added. In this case, the additional capacitance element C1 is not required.

Also, the resonance frequency f0 'of the trap moves to a higher frequency because the denominator of the calculation formula decreases when the coupling coefficient K increases, and moves to a lower frequency because the denominator increases when the coupling coefficient K decreases. I understand. Alternatively, when the number of turns of the winding N42 is increased while the coupling coefficient K is fixed, the denominator of the calculation formula becomes large, so that the denominator becomes smaller when the number of turns of the winding N42 is reduced. I understand. As described above, by giving a certain width to the coupling coefficient K or the number of turns of the winding N42, the resonance frequency f0 'of the trap can be adjusted to the image frequency band.

When the characteristics of the double-tuned circuit embodying the present invention are compared with those of the conventional circuit shown in FIG. 6, as shown in FIG. 7, the characteristics are attenuated near the image frequency and are measured in the MW band. An improvement of ~ 45 dB was seen. Also, the receiving sensitivity is at the same level as that of the conventional circuit, and the image frequency is suppressed without deteriorating other electric characteristics. Furthermore, the load tuning transformer, one of the double-tuned transformers, uses a common winding, so the number of turns is greatly reduced compared to the conventional type, realizing a compact and lightweight double-tuned transformer.

8 to 10 show modified examples of the double tuning circuit of the present invention. The double tuning circuit of FIG. 8 has two taps b and b '.
The next tuning winding N5 and the output tuning winding N41 are transformer-coupled,
The primary tuning winding N2 and the secondary tuning winding N5 are connected via taps a and b '. The tap b 'is connected to one end of the output tuning winding N41 via the additional capacitance element C2, and the tap b is connected to the other end of the output tuning winding N41.
A secondary resonance circuit is formed by connecting a variable capacitance element C in parallel with the next tuning winding N5.

The double-tuned circuit shown in FIG. 9 is obtained by connecting a capacitance element C0 for tracking correction in parallel with the variable capacitance element C of the circuit shown in FIG.

The double-tuned circuit shown in FIG. 10 is a circuit in which the winding N21 of the circuit shown in FIG. 1 is independently wound, and the tap a is omitted, and the winding is directly connected to the coupling winding N3.

[0030]

As described above, the double-tuned transformer according to the present invention comprises an antenna-tuned transformer having a variable capacitance element connected in parallel with a primary tuning winding having a tap a, and a tap b.
And a secondary tuning winding with a tap c is used as a common winding, and a tap b is directly provided at the beginning of the secondary tuning winding.
The tap c is connected to the beginning of the winding of the coupling winding via an additional capacitance element for impedance correction, and a load tuning transformer formed by connecting a variable capacitance element in parallel with this is arranged on the input side and the output side, respectively. Then, the tap a of the primary tuning winding is connected to the beginning of winding of the coupling winding, and the tap c of the secondary tuning winding is connected to the amplifier via an additional capacitive element for blocking DC current. Therefore, according to the present invention, the mutual inductances M and L due to the mutual induction of the common winding of the load tuning transformer.
Since the trap circuit is formed by C, when the variable capacitance element is changed, the resonance frequency of the trap circuit also changes in conjunction with the reception frequency, and the image frequency that changes according to the reception frequency can be suppressed. Further, since the additional capacitance element corrects the impedance of the tuning circuit, the attenuation band of the trap can be made closer to the image frequency. Further, since the load tuning transformer is commonly wound and the mutual inductance M is drawn out, no new components for trapping are required, and the economy and reliability are improved.

Further, the double-tuned transformer according to the present invention comprises a plurality of brim drum types having two or more winding grooves, while arranging the number of turns and the coupling coefficient of the coupling winding and the secondary tuning winding of the load tuning transformer. Wrap around a ferrite core. Further, the winding on the winding start side and the secondary tuning winding, which are connected in series via the tap b of the coupling winding, form a mutual induction circuit in which the magnetic fluxes are applied with the respective winding starts having the same polarity. Therefore, according to the present invention, the resonance frequency of the trap changes depending on the number of windings and the coupling coefficient of the common winding of the load tuning transformer, and the number of windings and the coupling coefficient are arranged together with the additional capacitance element for impedance correction to adjust the resonance frequency of the trap. Can be appropriately adjusted to the vicinity of the image frequency.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a double tuning circuit embodying the present invention.

FIG. 2 is a winding diagram of a tuning coil embodying the present invention.

FIG. 3 is a frequency characteristic diagram of a double tuning circuit embodying the present invention.

FIG. 4 is a simplified circuit diagram of FIG.

FIG. 5 is an equivalent circuit diagram of FIG.

FIG. 6 is a circuit diagram of a conventional double tuning circuit.

FIG. 7 is a diagram comparing characteristics of a double-tuned circuit embodying the present invention and a conventional circuit.

FIG. 8 is a modified example of the double tuning circuit embodying the present invention.

FIG. 9 is another modified example of the double tuning circuit embodying the present invention.

FIG. 10 is another modified example of the double-tuned circuit embodying the present invention.

[Explanation of symbols]

 1-2 terminals C Variable capacitance elements C ', C1, C2 Additional capacitance elements C0 Tracking correction capacitance elements D Drum core D1 First groove D2 Second groove CA Cap core L Self-inductance M Mutual inductance N1 Primary input winding N2 1 Secondary tuning winding N3 Coupling winding N4 Secondary tuning winding N41 Output tuning winding N5 Secondary tuning winding a, b, b ', c Tap T1 Antenna tuning transformer T2 Load tuning transformer

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[Procedure amendment]

[Submission date] October 6, 2000 (2000.10.
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

The primary input winding N1 has one end connected to a terminal 1 connected to an antenna (not shown) and the other end grounded.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

The output c is drawn from the tap c of the secondary tuning winding N4, and is output through the additional capacitive element C 'for blocking DC current.
Connect to terminal 2 which connects to a C amplifier (not shown).
Further, it is also connected to the winding start of the coupling winding N3 and the tap a of the primary tuning winding N2 via the additional capacitance element C2. Thereby, a trap circuit for the image frequency by the windings N31, N32, N41, N42, the additional capacitance element C2, and the variable capacitance element C is formed. In the figure, the additional capacitance element C2 has a tap a at one end (or the start of winding of the coupling winding N3).
And the other end are connected to the tap c, but one end is connected to the coupling winding N.
3 and the other end may be connected to an arbitrary point in the secondary tuning winding N4. Further, although the winding start of the winding N41 is connected to the tap b in the drawing, it may be directly grounded.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

8 to 10 show modified examples of the double tuning circuit of the present invention. The double tuning circuit of FIG. 8 has two taps b and b '.
The transformer winding is coupled between the secondary tuning winding N5 and the output winding N41, and the primary tuning winding N2 and the secondary tuning winding N are connected via taps a and b '.
5 is connected. The tap b 'is connected to the additional capacitance element C2.
, And a tap b is connected to the other end of the output winding N41, and the secondary tuning winding N
5 and a variable capacitance element C is connected in parallel to form a secondary resonance circuit.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] Explanation of sign

[Correction method] Change

[Correction contents]

[Description of Signs] 1-2 terminals C Variable capacitance elements C ', C1, C2 Additional capacitance elements C0 Tracking correction capacitance elements D Drum core D1 First groove D2 Second groove CA Cap cores L42, L43 Self inductance -M Mutual inductance N1 primary input winding N2 primary tuning winding N3 coupling winding N4 secondary tuning winding N41 output winding N5 secondary tuning winding a, b, b ', c tap T1 antenna tuning transformer T2 load tuning transformer

[Procedure amendment]

[Date of submission] October 16, 2000 (2000.10.
16)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

The output is drawn from the tap c of the secondary tuning winding N4, and is supplied to the IC via an additional capacitive element C 'for blocking DC current.
Connect to terminal 2 which connects to an amplifier (not shown). Further, it is also connected to the winding start of the coupling winding N3 and the tap a of the primary tuning winding N2 via the additional capacitance element C2. Thereby, a trap circuit for the image frequency by the windings N31, N32, N41, N42, the additional capacitance element C2, and the variable capacitance element C is formed. In the figure, the additional capacitance element C2 has one end connected to the tap a (or the start of winding of the coupling winding N3) and the other end connected to the tap c.
And the other end may be connected to an arbitrary point in the secondary tuning winding N4. Further, although the winding start of the winding N41 is connected to the tap b in the drawing, it may be directly grounded.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K020 DD02 DD11 EE01 EE14 HH06 LL05 MM12 MM13 5K058 AA20 BA01 CA01 CA02 DA02 DA13 EA07

Claims (5)

[Claims] 1. An antenna tuning transformer having a variable capacitance element connected in parallel with a primary tuning winding having a tap a, a coupling winding having a tap b and a secondary tuning winding having a tap c are commonly used. The tap b is directly connected to the beginning of the winding of the secondary tuning winding, the tap c is connected to the beginning of the winding of the coupling winding via an additional capacitance element for impedance correction, and a variable capacitance element is connected in parallel with this. And a load tuning transformer comprising: a tap a of the primary tuning winding connected to the beginning of the coupling winding; and a tap c of the secondary tuning winding for direct current cutoff. A double-tuned transformer for a superheterodyne receiver, wherein the transformer is connected to an amplifier via an additional capacitance element. 2. The method according to claim 1, wherein the coupling winding and the secondary tuning winding of the load tuning transformer are arranged by changing the number of windings and the coupling coefficient.
2. The double-tuned transformer according to claim 1, wherein said double-tuned transformer is wound around a plurality of brim drum type ferrite cores having said winding grooves. 3. A coupling coefficient between a winding on a winding start side and a secondary tuning winding connected in series via a tap b of the coupling winding is set to 0.1 to 0.7. Item 1
Double tuning transformer as described. 4. The double-tuned transformer according to claim 1, wherein a coupling coefficient of a winding connected in series via a tap c of the secondary tuning winding is set to 0.85 to 1.0. 5. A mutual induction circuit in which the winding on the winding start side and the secondary tuning winding connected in series via the tap b of the coupling winding have the same polarity at the winding start and are applied with a magnetic flux. 2. The double-tuned transformer according to claim 1, wherein the transformer is formed.