JPS641792Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a Yarman wave transducer that ensures guaranteed attenuation within the attenuation passband.

As is well known, in this Yarmann type wave device, an input signal is first applied to the primary side of the transformer, and voltages having inverse phases and the same value are extracted with respect to the middle point of the secondary side. Then, the above voltage is supplied to the reactance elements of the two arms that have reactances of opposite signs in the desired passband and reactances of the same sign outside the desired passband, and the connection point of the reactance elements of those arms is This circuit outputs the voltage generated between the transformer and the midpoint of the secondary side of the transformer.

Traditionally, the means to ensure guaranteed attenuation are as follows:
The number of stages of reactance elements in the wave circuit was increased to two or more stages. However, this increase in the number of stages means an increase in the number of piezoelectric resonator elements in piezoelectric Yarmann type wave transmitters such as crystals, and is especially important for carrier communication wave devices used in the frequency band of 60kHz to 4MHz (e.g., pilot signal extraction). In wave equipment),
Since the external dimensions of the piezoelectric resonator are large and the piezoelectric resonator is expensive, it has the drawback of increasing the size and cost.

On the other hand, as a means of ensuring guaranteed attenuation without increasing the number of stages so much, there is a method in which an LC series tuned circuit 1 is connected to the input side of a crystal Yurmann type wave circuit 2 as shown in FIG. Regarding the symbols in the same figure,
The Yarman wave circuit 2 is constructed by T ₁ and T ₂ being an input transformer and an output transformer, respectively, A and B being crystal resonators, and either one of them may be a capacitive element. These crystal resonators A and B are
As shown in the reactance characteristics in Figure 2, each series resonance point (frequency) f _A1 = 84.06kHz, f _B1 = 84.08kHz and each parallel resonance point (frequency) f _A2 = 84.08kHz, f _B2 =
84.10kHz, reactance of the same sign between both f A1 in the frequency range lower than f _A1 , reactance of opposite sign between both f _B1 in the desired passband (f _A1 ~ f _B2 ), and reactance of both in the frequency range higher than f _B2 . The attenuation characteristics shown in FIG. 3 are obtained in the vicinity of the center frequency because the reactances of the same sign appear as shown in FIG.

However, in this circuit, a new parallel resonance point occurs on the low-frequency side of the reactance characteristic shown in Figure 2.
Since f _A3 = 59.8kHz and f _B3 = 60.0kHz appear,
On the low frequency side (near 60 kHz), the attenuation decreases (40 dB) as shown in Figure 3, resulting in an unnecessary pass band.

The purpose of the present invention is to ensure a guaranteed attenuation amount without increasing the number of wave circuit stages and to prevent the generation of unnecessary passbands as described above.

FIG. 4 is a circuit diagram of a crystal Yarmann type wave device which is an embodiment of the present invention. As for the symbols 1 and 2 in the same figure, as in FIG. 1, they are an LC series tuned circuit and a crystal Yurmann type wave circuit, respectively. 3 is a resistive attenuation circuit inserted and connected between the series tuned circuit 1 and the Yarman wave circuit.

The coil L and capacitance C of the series tuned circuit 1 satisfy the tuning condition at the center frequency of 84.08 kHz of the desired pass band in this example, and are set to 1.49 mH and 2400 pF, respectively. A resistor R ₁ that constitutes the resistance attenuation circuit 3,
The resistance values of R ₂ and R ₃ are 5.6Ω, 5.6Ω, and 510Ω, respectively. In addition, crystal resonators A and B, which are reactance elements of the Yarman wave circuit 2,
is similar to that shown in FIG. 1, but parallel capacitors C _A and C _B are connected for frequency adjustment.

In the circuit of this example as well, the attenuation characteristics are as shown in Figure 5 in the unnecessary pass band on the low frequency side.
Since attenuation of 57dB or more has been obtained, effectively,
The generation of unnecessary pass bands can be prevented. Note that an attenuation amount of 60 dB or more is obtained in the attenuation region centered on the desired passband (f _A1 - f _B2 ).

This damping effect on the low frequency side is shown in Figures 1 and 2.
Comparison with Fig. 3 and Fig. 3 reveals that the resistance attenuation circuit 3
It is clear that this is due to the insertion of .

Examples of the resistance attenuation circuit 3 include T-type, O-type, and O-type as shown in FIG.
There are three types: H type, H type, and π type. In the same figure, a is the same as the resistance attenuation circuit 3 shown in Fig. 4, and for each terminal, A is the series tuned circuit side, B is the Yarman wave circuit side, and C and D are the connections on the ground side. It is a point.

Thus, according to the Yarman type wave device of the present invention,
It has great economic value because it ensures a sufficient guaranteed attenuation amount without increasing the number of stages of reactance elements in the wave circuit, and prevents the generation of unnecessary passbands.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional Yarman type wave generator, Figure 2 is a reactance characteristic diagram of the circuit in Figure 1,
3 is an attenuation characteristic diagram of the circuit shown in FIG. 1, FIG. 4 is a circuit diagram of a crystal Yarmann type wave device which is an embodiment of the present invention, and FIG. FIG. 6 is a diagram showing an embodiment of the resistance attenuation circuit. Explanation of symbols of embodiments, 1...Series tuned circuit, 2
...Yarman type wave circuit, 3...Resistance attenuation circuit.

Claims (1)

[Scope of utility model registration request] A Yarman type wave device characterized in that a resistive attenuation circuit is inserted and connected between the Yarman type wave circuit, the series tuning circuit, and the ground.