JPH029438Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a telemeter transmitter.

[Prior art and its problems]

In general, telemetry is a widely used and useful method for transmitting signals obtained at remote or difficult-to-reach locations or where connections such as cables are inappropriate.

For example, in medical applications, it is also effective when transmitting a physical information signal to a distant monitoring device or the like.
For such uses, miniaturization is often required as a specification required for telemeters.

Conventional telemeter transmitters had separate circuit configurations for a detector for detecting information and an oscillator, so the transmitter had to be large. In particular, when frequency modulating the output of the oscillator using the signal from the detector, a frequency modulator is required, which has the drawback of complicating the entire circuit.

However, when using a transistor self-exciting oscillator in VHF or UHF as an oscillation circuit, a signal is applied to the base superimposed on the DC bias,
It is well known that frequency modulation can be applied relatively easily, and it has been used in wireless microphones and the like. For example, if the signal obtained from a sensor is appropriately amplified and pre-processed, such as bandpass processing, and then applied to the base of an oscillating transistor, it is possible to easily obtain a carrier frequency-modulated by the desired signal. .

However, even when such a self-excited oscillator method is adopted, the conventional technology is insufficient for manufacturing an extremely small telemeter, and a simpler circuit has been desired.

[Problem that the invention attempts to solve]

The present invention has been devised to solve the problems of the prior art described above, and its purpose is to provide a telemeter transmitter with an extremely simple configuration, and in particular, to provide a telemeter transmitter that uses only a few parts. By reducing this, it is possible to provide a more compact telemeter transmitter.

[Means for solving problems]

In short, the present invention consists of an oscillator circuit formed by a transistor whose collector and emitter are coupled to a resonant circuit and whose base is grounded in an alternating current manner; A strain element (electrostrictive vibrator), an antenna that propagates the oscillation output in space,
The carrier signal oscillated by the oscillation circuit is frequency-modulated with an electric signal corresponding to the vibration applied to the electrostrictive element and sent from the antenna, and the base of the transistor is grounded in an alternating current manner. It is characterized in that it is performed by the electrostrictive element.

〔Example〕

Hereinafter, the present invention will be explained based on embodiments shown in the drawings. FIG. 1 is a circuit diagram of a telemeter transmitter according to an embodiment of the present invention. In the figure, a capacitor 13 is connected between the collector and emitter of a transistor 11, and the collector is connected to a coil 15.
The emitter is connected to the +V power supply with a pass capacitor 16 through the capacitor 1.
7 and a resistor 19 in a parallel circuit. Also, the base of transistor 11 is connected to resistor 2.
1 to a +V power source, and is grounded at high frequency via a ceramic electrostrictive vibrator (electrostrictive element) 23. In addition, "electrostrictive element" is written as
It has been commonly used to refer to the same thing as a piezoelectric element, and the term electrostrictive element used in this specification has this meaning and is not used with the intention of distinguishing it from a piezoelectric element. do not have. The tap of coil 15 is connected to antenna 25.

The embodiment of the present invention is constructed as described above, and its operation will be described below. Transistor 11, coil 15 and both capacitors 13, 17
The carrier signal is generated by a well-known Colpitts oscillator circuit formed in . A DC current is supplied to the base of the transistor 11 via a resistor 21, and an electric signal converted from vibrations detected by a ceramic electrostrictive vibrator 23 is supplied to the base of the transistor 11, although the high frequency is in a bypassed state. Since they are supplied in a superimposed manner, the bias state of the base changes.
Therefore, the collector output capacitance of the transistor 11 changes, and the coil 15 and both capacitors 13 and 1
As a result of the change in the resonance point of the tank circuit formed by 7, the carrier signal is frequency modulated by the detection signal. This FM wave is then sent out into free space from the antenna 25 and propagated to a remote monitoring device (not shown) or the like.

In general, a junction transistor has the property that its collector output capacitance changes depending on its bias state, that is, the average collector (or emitter) current. To obtain a simple oscillator, a method has been widely used in which the collector output capacitance is changed by changing the oscillation frequency by the target signal, and the oscillation frequency is FM-modulated by the target signal.

However, in the present invention, in order to configure such an FM oscillation circuit, we were inspired by the fact that the base should be bypassed to ground at high frequencies, especially in Colpitts type circuits, and the bypass capacitor itself is used to convert the base to obtain the target signal. It is constructed so that it can be used also as a device, and the circuit is simplified, smaller and lighter. Furthermore, since the elements of the resonant circuit, which are the frequency determining factors, are not related to the sensor, it is possible to use ones that are excellent in terms of aging, temperature changes, mechanical stability, etc., so the circuit operation is stable and reliable. It is possible to obtain an oscillation signal with high frequency, especially high frequency, and excellent stability.

The electrostrictive vibrator 23 uses, for example, disc-shaped barium zirconium titanate with a diameter of several centimeters, and has a diameter of several thousand centimeters.
pF, it can be used as a bypass capacitor in the VHF or UHF bands.

When the signal object of the vibration detected and converted by the electrostrictive vibrator 23 is a heart sound of an adult, the electrostrictive vibrator 23 may be attached to the chest wall of the adult. Then, by receiving FM waves modulated by the detected heart sounds with an FM receiver, the heart sounds can be heard in a remote location. It goes without saying that what is detected by the electrostrictive element is not limited to heart sounds, but can also be applied to various vibrations and sounds.

In addition, in the above embodiment, a Colpitts type circuit is used as an example of an oscillation circuit in which the base is bypassed in terms of high frequency, but the present invention is not limited to this, and any oscillation circuit in which the base is bypassed in terms of high frequency It goes without saying that any type of oscillation circuit can be implemented by using a capacitive converter as its base bypass capacitor.

〔effect〕

Since the present invention is constructed and operates as described above, it is possible to realize a telemeter oscillator in which the detection part and the oscillator are integrally formed, the circuit is extremely simple, and the telemeter oscillator is small and lightweight, and is suitable for practical medical and industrial applications. It has a remarkable effect. This invention is especially useful for applications that require a small telemeter, such as medical telemeters for newborns and children, telemeters for experiments that are implanted inside animals, and industrial telemeters that must be installed in extremely narrow spaces. is exhibited extremely well.

[Brief explanation of drawings]

The drawing is a circuit diagram of an embodiment of the present invention. 11 is a transistor, and 23 is an electrostrictive element.

Claims (1)

[Scope of utility model registration request] A transistor whose collector and emitter are coupled to a resonant circuit and whose base is grounded in an alternating current manner to form an oscillation circuit; an electrostrictive element which also serves as a means for grounding the base of the transistor in an alternating current manner; and an oscillation output. and an antenna for propagating in space, the telemeter transmitter characterized in that the carrier signal oscillated by the oscillation circuit is frequency-modulated with an electric signal corresponding to the vibration applied to the electrostrictive element and sent from the antenna. vessel.