JPH0441647Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a waveform conversion circuit for a radio control (hereinafter abbreviated as radio control) transmitter for remotely controlling models of automobiles, airplanes, etc.

(Prior Technology) Conventionally, radio-controlled transmitters used to remotely control models of automobiles, airplanes, ships, etc., as well as industrial equipment such as cranes and pruning machines, have been equipped with waveform conversion to narrow the transmission signal band. circuit is used.

FIG. 3 shows a schematic block diagram of a general radio-controlled transmitter. In FIG. 3, an output section of an analog signal generation circuit 301 that outputs analog signals related to the operation of a plurality of stakes (not shown) is
It is connected to the input section of the signal conversion section 302. The signal converter 302 includes a multiplexer, an analog
It is composed of a digital conversion circuit and the like, and its output section is connected to the input section of the encoder 303. The output section of encoder 303 is connected to the input section of waveform conversion circuit 304. The output section of the waveform conversion circuit 304 is connected to the input section of the modulation section 305. The output section of the modulation section 305 is the high frequency section 30
6 input section. The operation of the radio-controlled transmitter configured as shown in FIG. 3 will be briefly explained.

Multiple channels of parallel analog signals related to the operation of each stake are generated by the analog signal generation circuit 30.
1, the signal converter 302 divides the parallel analog signal into each channel and converts it into a serial digital signal.
Enter. The encoder 303 converts the serial digital signal into a pulse position modulation (PPM) signal or pulse code modulation (PCM) for each channel.
The waveform conversion circuit 30 converts the rectangular wave signal into a signal, etc.
Enter 4. The waveform conversion circuit 304 performs waveform conversion to reduce harmonic components in order to narrow the transmission signal band, as will be described later. Modulation section 30
5 performs amplitude modulation (AM) or frequency modulation (FM) on the waveform-converted signal, and further modulates the high frequency part 3.
After the power is amplified in step 06, the signal is transmitted as radio waves from the antenna 307.

FIG. 4 is a circuit diagram of the waveform conversion circuit 304.
The same parts as in FIG. 3 are given the same reference numerals. FIG. 5 is a timing diagram of the circuit shown in FIG.

4 and 5, a rectangular wave signal V _A from an encoder 303 is integrated by an integrating circuit 407 composed of a resistor 401, a capacitor 403, and an operational amplifier 404. Integrating circuit 407
Since a limiter circuit 402 is connected in parallel with the capacitor 403 in order to suppress fluctuations in the output signal level, the waveform of the output signal V _C of the integrating circuit 407 becomes as shown in FIG.

The signal V _C has an angular edge E, and in order to round the edge E, it is passed through an integrating circuit 408 consisting of a resistor 405 and a capacitor 406. The obtained signal V _D is sent to modulation section 305.

(Problems with the Prior Art) As described above, the edges of the rectangular wave are rounded by the two-stage integrating circuit to reduce harmonic components. However, the signal V _D still has a steep edge E as shown in FIG. If the change over time is large like this, the signal V _D will contain harmonic components.

For example, when outputting FM modulated signal _VD ,
If the carrier signal frequency is _p and the modulation signal frequency is _e , then the sideband components are _p ± _e and _p ±
2 _e , ... sideband waves are generated. Originally, in the case of FM modulation, the bandwidth changes depending on the modulation index and modulation signal frequency, but under the same conditions, if the signal V _D contains many harmonics, the amplitude of high-order sidebands will increase. The frequency band becomes wider.

Furthermore, in the case of AM modulation, the frequency band of the signal V _D is overlapped before and after the carrier signal frequency, so if the signal V _D includes many harmonics, the frequency band will expand.

Therefore, there was a problem in that the transmission frequency bandwidth could not be made very narrow, and interference etc. occurred.

The present invention has been developed in view of the above drawbacks, and an object of the present invention is to provide a wave conversion circuit for a radio control transmitter that eliminates steep edges so as to narrow the transmission bandwidth.

(Means for Solving the Problems) The present invention provides a waveform conversion circuit for a radio control transmitter that converts a signal from an encoder related to a stake operation into a waveform and sends the signal to a modulation section, which integrates the signal from the encoder. a level detection circuit that detects the output level of the integration circuit and outputs a detection signal; a switch circuit that changes an integration time constant of the integration circuit in response to the detection signal; and a limiter circuit that limits the peak value of the waveform of the output signal.

(Operation) Steep edges are removed by switching the integration time constant of the integration circuit using a switch circuit depending on the output signal level of the integration circuit.

(Embodiment) FIG. 1 is a circuit diagram showing an embodiment of the present invention. The same parts as in FIG. 3 are given the same reference numerals.

In FIG. 1, a rectangular wave signal V _A from an encoder 303 is input to an integrating circuit 110 composed of resistors 101 and 102, a capacitor 105, and an operational amplifier 106. A limiter circuit 104 is connected to both ends of the capacitor 105.
The output signal V _C of the integrating circuit 110 is output from the integrating circuit 11 composed of a resistor 108 and a capacitor 109.
1 to the subsequent modulation section 305 as a signal _VD . Further, the signal V _C is input to a level detection circuit 107 that functions as a window comparator. The level detection circuit 107 outputs the signal V _C
A detection signal _VB corresponding to the voltage level of the switch 103 is output, and the switch 103 is controlled to open and close accordingly.

FIG. 2 is a timing diagram of the waveform conversion circuit of FIG. 1. A detailed explanation will be given below using FIGS. 1 and 2.

First, it is assumed that in the initial state, the signal V _A from the encoder 303 is at a low level and the switch 103 is in an open state. When a high-level rectangular wave signal V _A is input to the integrating circuit 110 from the encoder 303 at time To, the integrating circuit 110 integrates the signal V _A with an integration time constant determined by the resistors 101 and 102 and the capacitor 105. When the output signal V _C of the integrating circuit 110 becomes V ₁ , the level detection circuit 107 detects this and outputs a high level detection signal V _B. The switch 103 is the detection signal V _B
It becomes closed state in response to. This allows resistor 10
2 are short-circuited, the integration time constant of the integration circuit 110 changes, and the signal V _C changes sharply.
When the signal V _C becomes V ₂ , the level detection circuit 107 detects this and detects a low level detection signal V _B. As a result, the switch 103 is opened again, so that the integration time constant returns to its initial value, and the signal V _C changes gradually. When the signal V _C becomes V _L , the limiter circuit 104 operates to maintain the signal V _C at a constant voltage V _L.

When signal V _A changes to a low level at time T ₁ , signal V _C changes with an integral time constant determined by resistors 101 and 102 and capacitor 105 . When the signal V _C becomes V ₂ , the level detection circuit 10
7 detects this and outputs a high level detection signal _VB . Since the switch 103 is closed in response to this, the integration time constant changes and the signal V _C changes sharply.

When the signal V _C becomes V ₁ , the level detection circuit 107
detects this and outputs a low-level detection signal _VB . The switch 103 responds to this and becomes open, so the integral time constant returns to its initial value and the signal
V _C changes slowly.

When the signal V _C becomes Vo, the limiter circuit 104 operates to maintain the signal V _C at a constant voltage Vo. Thereafter, the same process as described above is repeated to convert the rectangular wave signal V _A into a signal V _C that changes in multiple stages. Since the signal V _C does not have sharp edges, its frequency bandwidth is narrow. The signal V _C is further rounded by the integrating circuit 111 and is input to the modulation section 305 as the signal V _D.

As described above, in this embodiment, the integration time constant is changed every time the signal V _C reaches a predetermined value.
Instead of a waveform with a steep change like the point E in the signal V _C in FIG. 5, it is possible to convert it into a waveform that changes in multiple stages and has a gradual change with few changes per time. Therefore, a signal with few harmonic components and a narrow frequency bandwidth can be obtained.

Therefore, if the signal obtained from the waveform conversion circuit 304 is subjected to AM modulation or FM modulation in the modulation section 305 and then sent from the antenna 307 via the high frequency section 306, the transmission frequency band is narrow and interference etc. It can output strong transmission radio waves.

Furthermore, if you want to further narrow the frequency bandwidth of the output signal from the waveform conversion circuit, you can obtain a rounded signal, that is, a signal with an extremely narrow frequency bandwidth, by providing the above-mentioned integrating circuit at the subsequent stage. I can do it.

(Effect of the invention) In the waveform conversion circuit of the present invention, the integration time constant is changed according to the output signal level of the integration circuit, so the output signal obtained by the waveform conversion circuit is a signal with a narrow frequency band. , the transmission radio waves output from the transmitter can also narrow the transmission bandwidth,
It is possible to output transmission radio waves that are resistant to interference.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an embodiment of the present invention, Figure 2 is a timing diagram of the circuit in Figure 1, Figure 3 is a block diagram of a general radio control transmitter, and Figure 4 is a block diagram of a general radio control transmitter.
The figure is a circuit diagram of a conventional waveform conversion circuit, and Figure 5 is a circuit diagram of a conventional waveform conversion circuit.
3 is a timing diagram of the circuit shown in FIG. 110, 111, 407, 408...Integrator circuit, 104,402...Limiter circuit, 103...
...Switch, 107...Level detection circuit, 301
... Analog signal generation circuit, 302 ... Signal conversion section, 303 ... Encoder, 304 ... Waveform conversion circuit, 305 ... Modulation section, 306 ... High frequency section.

Claims (1)

[Scope of utility model registration request] A waveform conversion circuit for a radio control transmitter that converts a signal from an encoder related to a stake operation into a waveform and sends it to a modulation section includes an integrating circuit that integrates the signal from the encoder and an output level of the integrating circuit that detects the output level of the integrating circuit. , a level detection circuit that outputs a detection signal, a switch circuit that changes an integration time constant of the integration circuit in response to the detection signal, and a limiter circuit that limits the peak value of the waveform of the output signal from the integration circuit. A waveform conversion circuit for radio control transmitters.