JPS624015B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present application relates to a tuner that selects a tuning frequency by varying C and L of a tuning circuit, and particularly relates to a tuner that selects a tuning frequency by varying C and L of a tuning circuit.
The purpose of this system is to use a variable capacitance diode as a variable capacitance diode, and to make it possible to adjust the operating reference voltage of this diode, thereby facilitating tracking adjustment between tuning circuits and improving the performance of the receiver.

2. Description of the Related Art In general, L variable tuners made of variable inductance elements are widely used in car radios and the like. The reason for this is that the strong input characteristics are extremely good, and the reception characteristics do not change or the operation becomes unstable due to external vibrations, large changes in temperature and humidity, or the influence of dust, and the product is uniform. This is because it has an advantage over a C variable tuner in that it can be easily tuned. However, the problem with variable inductance tuners is that it is extremely difficult to accurately adjust the tracking between the tuned circuits, and the gain decreases at higher frequencies, while the gain becomes abnormal at lower frequencies. As a result, the operation of the receiver becomes unstable, and it is impossible to improve the performance of the receiver by increasing the number of tuning circuits.

That is, as is well known, a variable inductance tuner is equipped with a variable inductance element in each tuning circuit of the antenna circuit, RF circuit, and OSC circuit, and each variable inductance element is manually operated by the same sliding member. This method achieves tuning by varying L of the tuning circuit, but due to manufacturing errors, each variable inductance element has a different frequency characteristic curve, and conventionally, this frequency characteristic Tracking adjustments between the tuned circuits have been made to account for the difference in the curves by adjusting the protruding and retracting base positions of the high frequency magnetic cores with respect to the coil body, or by exchanging high frequency magnetic cores with different μ. However, in the former case, even if the position of the protruding and retracting base point is adjusted, the frequency characteristic curve of the variable inductance element is almost always shifted in parallel, so the frequency characteristic curve is shifted in parallel and the frequency characteristic curve of other variable inductance elements is shifted in parallel. Even if the frequency curves are tuned to a certain point in , the frequency characteristic curves are only close to each other, and the variable stroke of the variable inductance element is determined by the mechanical sliding stroke of the sliding member in the tuner. The upper and lower limit positions of the tuning frequency obtained when adjusting the protrusion and retraction reference point position of the magnetic core change together, and therefore it is extremely difficult to perform accurate tracking adjustment only by adjusting the protrusion and retraction reference point position of the magnetic core with respect to the coil body. be.

For example, as shown in Fig. 6, suppose that the frequency characteristic curve of one tuned circuit is A, and the frequency characteristic curve of another tuned circuit is B, and in this relationship, the coil of the variable inductance element has the frequency characteristic curve B. Assuming that the position of the origin of the magnetic core relative to the body is adjusted and both characteristic curves are adjusted to the vicinity of point P,
Frequency characteristic curve B only moves in parallel as shown by the broken line, but the two curves never match, and because the variable strokes are the same, its upper limit position F ₁ becomes F ₁ ' and its lower limit position respectively. F ₂ changes to F ₂ ', and therefore it is extremely difficult to accurately adjust tracking.

In addition, in the latter case, the work of measuring and classifying the μ characteristics of the high frequency magnetic core into numerous ranks and exchanging them is extremely troublesome and greatly lacks workability.
Furthermore, the variable inductance tuner has a drawback in that the gain decreases at higher frequencies, making it impossible to obtain a stable and uniform gain over the entire tuning frequency band.

Therefore, the present application is intended to improve such defects, and examples thereof will be described in detail below with reference to the drawings.

Figure 1 shows the basic tuning circuit of the present application, in which 1 is a variable inductance element that varies L by making a high-frequency magnetic core appear and disappear from the coil body, and a variable capacitance diode 2 is connected in parallel to this element. ing. 3 is a variable voltage circuit consisting of a variable resistor that varies the voltage applied to the variable capacitance diode 2; 4 is connected between the circuit consisting of the variable inductance element 1 and the variable capacitance diode 2 and the variable voltage circuit 3; The variable inductance element 1 and the variable voltage circuit 3 are mechanically connected to each other by a resistance circuit including a variable resistor that sets the operating reference voltage of the variable capacitance diode 2, and are commonly variable.

Now, the lower limit of the bandwidth of the tuning frequency is
If min is the upper limit and max is the upper limit, then the resonant frequency is Since it is expressed as as well as However, Lmin is the minimum value of variable inductance Lmax is the maximum value of variable inductance Cmin is the minimum capacitance of variable capacitance diode 2 Cmax is the maximum capacitance of variable capacitance diode 2, and the relationship between the variable magnification of LC and the tuning frequency is Lmax・Cmax/Lmin・Cmin=(max
x/min) ² ......

In the above formula, the present application calculates the variable magnification Lmax/Lmin of L and the variable magnification C of C.
The purpose is to adjust the band width of the tuning frequency by the product of max/Cmin, and as a specific example, a case where numerical values are substituted and applied to the AM band will be described in detail below.

Now, if the min is 510KHz and the max is 1650KHz, and this AM band width is covered only by the L variable tuning circuit, for example, Lmax/Lmin=(max/min) ² =
(1650/510) ² ... From the formula, the variable magnification of L is approximately 10.47.

By the way, as mentioned earlier, there are variations in the frequency characteristic curve of the variable inductance element due to manufacturing errors, so the following disadvantages arise when only the L variable tuning circuit is used.

That is, when the protrusion and retraction stroke of the high-frequency magnetic core with respect to the coil body is constant, and the variable range of a certain variable inductance element is 500KHz to 1690KHz due to manufacturing errors, the variable magnification is (1690/500) ² = 11.42 ......, and when the variable range of a certain variable inductance element is 520 KHz to 1610 KHz, the variable magnification is (1610/520) ² = 9.56 ......

In the case of the above formula, if the base position of the high-frequency magnetic core relative to the coil body is adjusted to the desired lower limit frequency of 510 KHz, the frequency at the upper limit position is calculated from the formula (max/510) ² = 11.42, max = 1723.8KHz, and in the case of the above formula, if the base point position of the high frequency magnetic core relative to the coil body is adjusted to 510KHz, the frequency at the upper limit position will be max = 1579KHz from the formula (max/510) ² = 9.56. , when trying to adjust tracking by only varying L as in the past, since the variable stroke of the high frequency magnetic core is the same, there is a large difference at the higher tuning frequency, making it difficult to tune the desired band width. This has the disadvantage that it cannot be achieved effectively.

Therefore, in the present application, the above-mentioned variable magnification of L is set to 10.47 or less, and the deficiency in the magnification is supplemented by the variable magnification of C to obtain the required bandwidth.

That is, let us now assume that the magnification of L is set to 7, for example. Then, from the formula (X/510) ² = 7, X or max becomes 1349KHz, and AM
There is a lack of tuning frequency selection in the band width range of 1349KHz to 1650KHz. Therefore, this shortfall in bandwidth is supplemented by the variable magnification of C. (1650/510) ² = 7 x becomes. Therefore, a variable capacitance diode with a variable magnification such that the variable magnification of C is 1.5 is selected. For example, if you select a variable capacitance diode with a variable range in which Cmin is 30PF and Cmax is 45PF, the variable magnification of C will be 1.5 from the formula Cmax/Cmin=45/30. Therefore, by combining the above formulas, (X/ 510) From the equation ² = 7 x 1.5, X, ie, max, becomes 1652 KHz, and a tuning circuit that sufficiently covers the AM band width can be obtained.

By the way, in the above, the variable magnification of L is 7, C
I mentioned the case where the variable magnification of is 1.5,
When changing the variable magnification of L, it is necessary to change the variable magnification of C as well, and even if the variable magnification of C is set to 1.5, the capacitance of variable capacitance diode 2 must be changed.
Since it is not necessary to limit Cmin to 30PF and Cmax to 45PF, it is necessary to configure the variable capacitance diode so that the variable range can be set arbitrarily. In order to solve this problem, the present invention is characterized in that a resistance circuit is provided to set the operating reference voltage of the variable capacitance diode.

Figure 3 shows a typical voltage vs. capacitance characteristic curve of a variable capacitance diode. In Figure 3, the capacitance of the variable capacitance diode 2 when the variable voltage circuit 3 is at the minimum voltage _V1 is _C1 , Variable voltage circuit 3
If the capacitance of the variable capacitance diode 2 when is the maximum voltage V ₂ is C ₂ , if the resistance circuit 4 does not exist, the voltage of the variable voltage circuit 3 changes from V ₁ to V ₂ , and the variable capacitance increases. Diode 2 is
It has a variable range from C ₁ to C ₂ , and the variable magnification of C is fixed. However, in the present application,
Since it has a resistance circuit 4, the resistance value of this variable resistance circuit 4 can be arbitrarily set, and the voltage applied to the variable capacitance diode 2 is determined by the combined resistance of the resistance value and the resistance value of the variable voltage circuit. By arbitrarily setting the variable range of , that is, the variable capacitance range of the variable capacitance diode 2, the variable magnification of C can be changed as desired, and the variable magnification of L and the variable range of the voltage applied to the variable capacitance diode 2 can be changed as desired. This has the advantage that not only can the bandwidth of the tuning frequency be arbitrarily changed by mutually adjusting them, but also variations in the characteristics of the variable capacitance diode and the variable inductance element can be easily corrected.

Note that FIG. 1 shows a case where the variable resistor constituting the resistance circuit 4 and the variable resistor of the variable voltage circuit that is varied in conjunction with the variable inductance element are connected in parallel. that both variable resistors may be connected in series as shown in the figure;
In addition, with this configuration, in addition to adjusting the operating reference voltage of the variable capacitance diode, it is also possible to adjust the variable magnification of its capacitance, so it goes without saying that resistor circuits may be connected in series and parallel. .

Furthermore, FIG. 2 shows a tuning circuit in which a fixed temperature compensation capacitor 5 for the purpose of temperature compensation of the variable capacitance diode 2 is connected in parallel in FIG. The temperature characteristics of the diode 2 are improved. In this case, the variable magnification of C is set by the change ratio of the combined capacitance of the variable capacitance diode 2 and the temperature correction capacitor 5.

Further, FIG. 5 shows each tuning circuit of a variable inductance tuner equipped with a plurality of tuning circuits that are variable with a high-frequency magnetic core, namely, an ANT circuit A, a first stage RF circuit B, a second stage RF circuit C, and an OSC circuit D. 2 shows a manual tuner to which a tuning circuit having the configuration shown in FIG. 2 is applied, and in this configuration, a variable voltage circuit 3 is commonly connected to each tuning circuit.

Moreover, although the above description shows the case where the temperature correction capacitor 5 is connected in parallel to the variable capacitance diode 2, it goes without saying that the capacitor 5 may be connected in series.

As described above, the present application provides a tuner equipped with a plurality of tuning circuits that are varied by a high-frequency magnetic core, in which at least one of the tuning circuits has a variable capacitance diode, and the operating reference voltage of the variable capacitance diode is adjusted. Since it includes a resistance circuit and a variable voltage circuit that varies the voltage applied to the variable capacitance diode in conjunction with the variation of the magnetic core, it has the following advantages.

In other words, as is well known, in a tuned circuit with variable L, the gain Q is high at low frequencies (the state in which the magnetic core is immersed in the coil body), and is high at high frequencies (the state in which the magnetic core has escaped from the coil body). However, the C variable tuning circuit has the opposite gain characteristic to the L variable tuning circuit, and therefore, according to the present application, the L, C
As already mentioned, since it is a variable tuning circuit, the gain can be obtained almost uniformly over the entire tuning frequency band width, and stable gain characteristics can be obtained.
When selecting, for example, the entire width of the AM band using an L variable tuning circuit, the L variable magnification needed to be about 10 times, but in this application, the tuning is done by multiplying it with the C variable magnification. According to the present application, since the frequency is set and the variable magnification of L is obtained smaller than in the above case, the variable stroke of the variable length inductance element can be shortened, which is effective in downsizing the tuner. In addition to the variable voltage circuit that operates in conjunction with the high-frequency magnetic core of the variable inductance element, a resistance circuit is provided to set the operating reference voltage of the variable capacitance diode, and the tuning frequency band width can be arbitrarily determined by the resistance value of the resistance circuit. Since the variable inductance is made variable, mutual tracking adjustment of the tuned circuits can be easily performed by adjusting the protruding and retracting base point position of the high frequency magnetic core with respect to the coil body of the variable inductance element and setting the resistance value of the resistor circuit.
This makes it possible to use a variable inductance element or a variable capacitance diode whose frequency characteristic curve has variations due to manufacturing errors, etc., making it possible to obtain an inexpensive tuner, and as mentioned above, the tuning circuit Since tracking can be performed extremely accurately and easily, it is possible to increase the number of tuning circuits, and therefore improve the selectivity of radio receivers.It can also be used to eliminate interference waves, improve sensitivity, stabilize operation, and even improve various characteristics. Extremely effective.

Further, according to the present invention, since a temperature compensation capacitor of a variable capacitance diode is connected, good temperature characteristics can be obtained, and there is an advantage that a tuner with stable operation as a whole can be provided.

[Brief explanation of the drawing]

The drawings show an embodiment of the present application, and FIGS. 1 and 2 are circuit diagrams showing the basic configuration of a tuning circuit, and FIG.
The figure shows a characteristic curve of voltage vs. capacitance of a variable capacitance diode, Figure 4 is another embodiment diagram showing the connection between a resistance circuit and a variable voltage circuit, Figure 5 is an overall circuit diagram of a manual tuner, FIG. 6 is an explanatory diagram of the frequency characteristic curve. In the figure, 1 is a variable inductance element, 2 is a variable capacitance diode, 3 is a variable voltage circuit, 4 is a resistance circuit, and 5 is a temperature correction capacitor.

Claims (1)

[Scope of Claims] 1. In a tuner equipped with a plurality of tuning circuits that are varied by a high-frequency magnetic core, at least one of the tuning circuits has a variable capacitance diode, and the operating reference voltage of the variable capacitance diode is adjusted. A tuner comprising: a resistance circuit; and a variable voltage circuit that varies the voltage applied to the variable capacitance diode in conjunction with the variation of the magnetic core. 2. The tuner according to claim 1, wherein the variable voltage circuit is constituted by a variable resistor. 3. The tuner according to claim 1 or 2, wherein the resistance circuit is constituted by a variable resistor. 4. A tuner including a plurality of tuning circuits that are varied by a high-frequency magnetic core, at least one of the tuning circuits having a variable capacitance diode, a resistor circuit that adjusts the operating reference voltage of the variable capacitance diode, and the magnetic A tuner comprising a variable voltage circuit that varies the voltage applied to the variable capacitance diode in conjunction with the variable capacitance of the core, and a capacitor for temperature correction of the variable capacitance diode is connected to the one tuning circuit. . 5. The tuner according to claim 4, wherein the variable voltage circuit is constituted by a variable resistor. 6. The tuner according to claim 4 or 5, wherein the resistance circuit is constituted by a variable resistor.