JPH0310525A - Side tone circuit - Google Patents

Abstract

PURPOSE:To prevent internal beat interference by utilizing a basic clock as a high frequency signal mixed to synthesize a side tone. CONSTITUTION:The oscillated frequency signal from a variable frequency oscillator 14 is mixed with a basic clock of 10MHz at a mixer 17 to be a frequency of 80kHz+ or -50kHz and frequency-divided into 1/100 by a frequency divider 8, becomes a sinusoidal wave through a switched capacitor filter 19 to obtain a side tone. The input to the frequency divider 18 is used as the clock to make the frequency through the switched capacitor filter 19 coincident with the center frequency. Thus, the side tone not causing internal beat interference is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a sidetone circuit for monitoring CW transmission in a wireless communication device, and particularly relates to a sidetone circuit that has a simple circuit and does not cause internal beat interference. .

[Conventional technique fr1 A conventional example of a sidetone circuit in which the receiving pitch (frequency of received sound) and sidetone frequency are linked is shown in the second example.
As shown in the figure.

The signal received from the antenna (ANT) is mixed with the oscillation frequency of variable frequency oscillator 2 by mixer 1 to 455KHz.
The first IF is obtained.

Tuning of received radio waves is performed by adjusting the oscillation frequency of the variable frequency oscillator 2.

35 generated by the receiver on the first IP of 455KHz above.
The 5 KHz frequency is mixed by mixer 3 to obtain the 21st F of 100 KHz.

The 355 KHz frequency is obtained by mixing the 100 KHz oscillation frequency of the oscillator 4 and the 455 KHz oscillation frequency of the oscillator 5, which is also used for transmission, in the mixer 6.

The second IP is mixed with the oscillation frequency of the variable frequency oscillator 8 in the detector 7 and subjected to product detection, and the resulting audio frequency passes through the changeover switch 11 that is linked to the telephone key and makes the speaker 12 sound.

The frequency generated by the variable frequency oscillator 8 is adjusted in the range of 99.2 KHz±500 Hz by the variable resistor 9, and the audio frequency changes in the range of 800 Hz±500 Hz. That is, the reception pitch can be adjusted.

The generated frequency of the variable frequency oscillator 8 is simultaneously mixed with the oscillation frequency of the oscillator 4 by a mixer 10 to 800Hz±500H.
z sidetone is obtained.

The side tone passes through the changeover switch 11 and causes the speaker 12 to sound.

Since the changeover switch 11 is connected to the TX side when the telephone key is pressed, the on/off state of the telephone key can be heard through the speaker.

The frequency of the side tone is determined by variable resistor 9 for adjusting the reception pitch.
The sidetone and received pitch change in the same way as the frequency of the received sound, and the sidetone and received pitch are linked.

[Problems to be Solved by the Invention] In the conventional sidetone circuit described above, the oscillation frequency of the oscillator 4 is transmitted through the input system of the mixer 10 and mixed with the oscillation frequency of the variable frequency oscillator 8 to generate an audio frequency. There was a problem in that the signal passed through the detector 7 and sounded the speaker, that is, internal beat interference occurred, causing the speaker to sound even when there was no received sound.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a sidetone circuit in which internal beat disturbance does not occur.

Another object of the invention is to provide a simple sidetone circuit with fewer oscillators.

[Means for Solving the Problems] The sidetone circuit of the present invention obtains a frequency for product detection of an intermediate frequency by dividing it from a variable frequency oscillator, and also mixes the frequency of the variable frequency oscillator and a basic clock. , the frequency obtained by the mixing is used as a clock of the switched capacitor filter, the frequency obtained by the mixing is divided and used as the input of the switched capacitor filter, and the output of the switched capacitor filter is used as a sidetone. It is something to do.

[Operation] The frequency obtained by mixing the frequency of the variable frequency oscillator for product detection and the basic clock is linked to the reception pitch. If the frequency associated with this reception pitch is divided, it will contain harmonics, but by passing it through a switched capacitor filter, it will be converted into a sine wave and a sidetone can be obtained.

The center frequency of the switched capacitor filter is proportional to the clock. By making the proportionality constant and the frequency division ratio equal, the center frequency and passing frequency of the switched capacitor filter can be matched.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a sidetone circuit according to an embodiment of the present invention.

The signal received from the antenna (ANT) is mixed with the oscillation frequency of variable frequency oscillator 2 by mixer 1 to 455KHz.
The first IF is obtained.

Tuning of received radio waves is performed by adjusting the oscillation frequency of the variable frequency oscillator 2.

The 355KHz frequency generated by the oscillator 13 is mixed with the 455KHz 11th frequency by the mixer 3, and the 100K
A second IP in Hz is obtained.

The second TF is subjected to product detection by a detector 7, and the resulting audio frequency passes through a changeover switch 11 that is linked to a telephone key, and causes a speaker 12 to sound.

The local oscillation voltage applied to the detector 7 is obtained by dividing the oscillation frequency of the variable frequency oscillator 14 to 1/100 by the frequency divider 16.

The frequency generated by the variable frequency oscillator 14 is adjusted by the variable resistor 15 in the range of 9.92 MHz±50 KHz, and the audio frequency changes in the range of 800 Hz±500 Hz. That is, the reception pitch can be adjusted.

The generated frequency of the variable frequency oscillator 14 is simultaneously controlled by the mixer 17.
mixed with 10MHz basic clock, 80KHz±
The frequency becomes 50KHz, and the frequency is divided by 1/10 by the frequency divider 18.
The signal is frequency-divided to 0, passes through a switched capacitor filter 19, becomes a sine wave, and obtains a sidetone.

When a switched capacitor filter is used as a bandpass filter, the clock frequency and center frequency are proportional, and the center frequency can be changed by changing the clock frequency.

In this example, the ratio of the clock frequency to the center frequency is 10
0, and by using the input of the frequency divider 18 as a clock, the frequency passing through the switched capacitor filter 19 matches the center frequency.

The side tone passes through the changeover switch 11 and causes the speaker 12 to sound.

The selector switch 11 is set to Txll when the telephone key is pressed.
Since it is connected to , you can hear the intermittent state of the telephone key through the speaker.

The frequency of the sidetone is determined by variable resistor 1 for adjusting the reception pitch.
5, the frequency changes in the same way as the frequency of the received sound, the sidetone and the received pitch are linked, and a sidetone that matches the received sound is obtained.

Although the embodiment is configured as described above, the invention is not limited to this. For example, the center frequency and tallock frequency of the switched capacitor filter may be other than 100, and in that case, the frequency dividers 16 and 18 The frequency ratio may be the ratio between the center frequency of the switched capacitor filter and the clock frequency.

[Effects of the Invention] As explained above, the sidetone circuit according to the present invention uses the basic clock as a high frequency signal mixed to synthesize sidetones, so the number of oscillators is small and the circuit is simple.

Further, the audio frequency is not synthesized by the oscillator for obtaining the sidetone and leaks into the detector, and it is possible to obtain the effect that internal beat disturbance is prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a sidetone circuit according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional sidetone circuit. 1...Mixer, 2...Variable frequency oscillator, 3...
Mixer, 4, 5... Oscillator, 6... Mixer, 7...
・Detector, 8... Variable frequency oscillator, 9... Variable resistor, 10... Mixer, 11... Selector switch, 1
2... Speaker, 13... Oscillator, 14... Variable frequency oscillator, 15... Variable resistor, 16... Frequency divider, 17... Mixer, 18... Frequency divider, 19...
Switched capacitor filter. Figure 1

Claims (1)

[Claims] A frequency for product detection of the intermediate frequency is obtained by dividing a variable frequency oscillator, and the frequency of the variable frequency oscillator is mixed with a basic clock, and the frequency obtained by the mixing is used as a clock of a switched capacitor filter, Further, a sidetone circuit characterized in that the frequency obtained by the mixing is divided and inputted to the switched capacitor filter, and the output of the switched capacitor filter is used as a sidetone.