JPH05152847A - Elastic wave oscillator - Google Patents

Abstract

PURPOSE:To realize the elastic wave oscillator in which a frequency change at oscillation stop/start is reduced. CONSTITUTION:In the elastic wave oscillator comprising a crystal or lithium tantalate elastic wave element 2, a transistor(TR) 3 combined with the elastic wave element 2, a resistor 4 or an IC 5 or the like, a shield 10 shielding radiation of an infrared ray 9 is arranged between the elastic wave element 2 and the TR 3 or the resistor 4 or the IC5 or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elastic wave oscillator.
Specifically, a transistor, a resistor, an I
The present invention relates to an elastic wave oscillator that prevents heat from a heat-generating part such as C and reduces frequency changes when oscillation is stopped / started.

With the spread of digital mobile communication and the like in recent years, there has been used a method for stabilizing the frequency by using a PLL control circuit as an internal oscillation circuit for wireless communication. Further, in digital mobile communication and the like, a time division multiplex system is adopted in order to effectively use the frequency, and accordingly, a circuit for ending the synchronization in a short time is required.

Further, as the personal use of mobile communication devices has increased, the demand for lower power consumption has increased, and intermittent operation of oscillation circuits has been used. In order to meet such a demand, it is necessary to minimize the change in frequency at the time of stopping / starting the oscillation of the oscillator.

[0004]

2. Description of the Related Art Conventionally, as an oscillator, an elastic wave oscillator having a simple structure and high stability is used. FIG. 3 is a diagram showing a conventional acoustic wave oscillator. This is an acoustic wave device 2 using a crystal such as quartz or a piezoelectric crystal such as lithium tantalate, a transistor 3, a resistor 4 or I on a substrate 1.
A drive circuit including a C5, a capacitor 6, a varactor diode 7, etc. is mounted, and these are further sealed with a cap 8.

[0005]

In the above-described conventional acoustic wave oscillator, since the acoustic wave element 2 and the transistor 3, which is a heating element, the resistor 4, the IC 5, etc., are arranged in close proximity to each other, the Radiant heat is applied as infrared rays 9 from the heating element to the surface or side surface of the acoustic wave element 2 in accordance with the energization / stoppage, or is stopped. As a result, the acoustic wave element 2 is heated or cooled by heat from the surroundings, and there is a problem that the oscillation frequency is changed due to the temperature characteristic of the resonance frequency of the acoustic wave element.

FIG. 4 shows an example of temperature characteristics of the resonance frequency of the acoustic wave device. In this example, the resonance frequency increases as the temperature rises. For example, when the temperature rises by 1 ℃
There is a fluctuation of 200Hz at 0MHz). Therefore, when the acoustic wave element 2 is heated by radiant heat or the like, the oscillation frequency changes according to this temperature characteristic.

Therefore, when the oscillation frequency is controlled intermittently, especially when the oscillation frequency is controlled by the PLL control, the processing time required for the control is long and short in order to correct the frequency shift occurring at the time of steady oscillation and at the time of startup. There was a problem that time control became impossible. In the case of a gradual temperature change, it is controlled by the time constant in the PLL circuit.

The present invention intends to realize an acoustic wave oscillator in which the frequency change at the time of oscillation stop / start is reduced.

[0009]

In the elastic wave oscillator of the present invention, an elastic wave element 2 such as quartz or lithium tantalate, and a transistor 3, a resistor 4, an IC 5 or the like combined with the elastic wave element 2 are provided. In the elastic wave oscillator configured as described above, a shield 10 that blocks radiation of infrared rays 9 is arranged between the elastic wave element 2 and the transistor 3, the resistor 4, the IC 5, or the like.

In addition, the shield 10 for blocking the radiation of the infrared rays 9 is a plate-like object installed between the acoustic wave device 2 and the transistor 3, the resistor 4 or the IC 5 which is a heating element. Is characterized in that In addition to that, a shield 10 for blocking the radiation of the infrared rays 9 is attached to a part of a package 11 of the acoustic wave oscillator.

In addition to the above, a passive element such as a capacitor 6 or a varactor diode 7 which does not generate heat is used as a shield 10 for blocking the radiation of the infrared rays 9. By adopting this configuration, oscillation stop /
It is possible to obtain an elastic wave oscillator with less frequency change at startup.

[0012]

[Function] A transistor 3, a resistor 4, and
By providing the shield 10 for blocking the infrared radiation from the heating element between the heating element such as the IC 5 and the acoustic wave element 2, the acoustic wave element 2 is less affected by the radiant heat from the heating element. Therefore, the frequency change due to the temperature characteristic is reduced. As a result, the processing time for correcting the frequency shift that occurs at startup can be shortened.

[0013]

1 is a sectional view showing an embodiment of the present invention.
In the figure, reference numeral 2 denotes an elastic wave element in which a comb-shaped electrode for resonance is formed on a piezoelectric crystal such as quartz or lithium tantalate, which is for oscillating at a predetermined frequency in combination with a peripheral drive circuit. .. Reference numeral 3 is a transistor, 4 is a resistor, 5 is an IC, 6 is a capacitor, and 7 is a varactor diode, and these constitute an oscillation circuit. Each of these components is mounted on the substrate 1 of the package 11. And transistor 3, resistor 4, and I
It is sealed with a cap 8 having a shielding plate 10 provided so as to partition the heating element such as C5 from the acoustic wave element 2.

In this embodiment having such a configuration, even if the oscillation circuit is energized and stopped, the transistor 3, resistor 4,
Infrared rays 9 radiated from a heating element such as the IC 5 are shield plates 1
It is blocked by 0 and does not reach the acoustic wave device 2. Therefore, the temperature rise of the acoustic wave device 2 immediately after energization is remarkably reduced. As a result, when the oscillation stop period is short, the frequency at the time of restart can be made almost equal to that before stop. Further, as a result, even when the PLL control is performed, the deviation is small, so that the synchronization ends in a short time.

FIG. 2 is a sectional view showing another embodiment of the present invention. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals. This embodiment is basically the same as the previous embodiment described in FIG. 1, except that the shield plate 1 in the previous embodiment is different.
0 is provided on the cap 8 in this embodiment.
Is provided on the substrate 1. In this embodiment having such a configuration, the acoustic wave device 2, the transistor 3, the resistor 4, the IC
Since the shielding plate 10 is provided between the heating element 5 and the like, the infrared rays 9 from the heating element are blocked by the shielding plate 10 and do not reach the acoustic wave element 2. Therefore, the same effect as in the previous embodiment is obtained. Have. Instead of the shield plate 10 of this embodiment, a passive element such as a capacitor or a varactor diode which does not generate heat may be used.

[0016]

According to the present invention, the frequency change at the time of stopping / starting the oscillation can be suppressed. This action is particularly effective in the case of repeated start and stop in a short time, and is extremely effective, for example, in the case of stopping / starting oscillation in a short time of about 1 second in digital mobile communication.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is a sectional view showing an oscillator using a conventional acoustic wave device.

FIG. 4 is a diagram showing an example of a temperature characteristic of a resonance frequency of an acoustic wave device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Acoustic wave element 3 ... Transistor 4 ... Resistor 5 ... IC 6 ... Capacitor 7 ... Varactor diode 8 ... Cap 9 ... Infrared 10 ... Shield plate (shield) 11 ... Package

Claims (4)

[Claims] 1. An acoustic wave device (2) such as quartz or lithium tantalate, and a transistor (3), a resistor (4), or an IC combined with the acoustic wave device (2).
In an elastic wave oscillator composed of (5) and the like, infrared radiation (9) is radiated between the elastic wave element (2) and the transistor (3), the resistor (4), the IC (5) and the like. An elastic wave oscillator having a shield (10) for blocking. 2. The shield (10) for blocking the radiation of the infrared rays (9) is composed of the elastic wave element (2) and a transistor (3), a resistor (4), an IC (5) or the like which is a heating element. The elastic wave oscillator according to claim 1, wherein the elastic wave oscillator is a plate-shaped member provided between the two. 3. The elastic wave oscillator according to claim 1, wherein a shield (10) for blocking the radiation of the infrared rays (9) is attached to a part of a package (11) of the elastic wave oscillator. 4. A passive element such as a capacitor (6) or a varactor diode (7) that does not generate heat is used as the shield (10) for blocking the radiation of the infrared rays (9). Item 1. The elastic wave oscillator of item 1.