JPH0683101B2 - Side tone circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sidetone circuit for monitoring CW transmission in a wireless communication device, and more particularly to a sidetone circuit which has a simple circuit and does not cause internal beat disturbance. .

[Prior Art] Second conventional example of a side tone circuit of a type in which a reception pitch (a frequency of a reception sound) and a frequency of a side tone are interlocked with each other
Shown in the figure.

The signal received from the antenna (ANT) is mixed with the oscillation frequency of the variable frequency oscillator 2 in the mixer 1 and the 1st IF of 455 KHz.
Is obtained.

The tuning of the received radio wave is performed by adjusting the oscillation frequency of the variable frequency oscillator 2.

The frequency of 355 KHz generated by the receiver is mixed with the 11th F of 455 KHz by the mixer 3 to obtain the second IF of 100 KHz.

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

The second IF is mixed with the oscillating frequency of the variable frequency oscillator 8 in the detector 7 and product-detected, and the obtained audio frequency passes through the changeover switch 11 interlocked with the electronic key and sounds the speaker 12.

The frequency generated by the variable frequency oscillator 8 is controlled by the variable resistor 9.
Adjusted in the range of 99.2KHz + 500Hz, audio frequency is 800Hz + 5
It changes in the range of 00Hz. That is, the reception pitch can be adjusted.

The frequency generated by the variable frequency oscillator 8 is simultaneously mixed with the oscillation frequency of the oscillator 4 by the mixer 10 to obtain a side tone of 800 Hz + 500 Hz.

The side tone passes through the changeover switch 11 and sounds the speaker 12.

Since the changeover switch 11 is connected to the Tx side while pressing the electric key, the intermittent state of the electric key can be heard through the speaker.

The frequency of the side tone is a variable resistor 9 for adjusting the reception pitch.
Changes with the frequency of the received sound, and the side tone and the received pitch are linked.

[Problems to be Solved by the Invention] In the above-mentioned conventional side tone circuit, 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, an audio frequency is generated, and the audio frequency is changed. The speaker is rung through the wave detector 7. That is, there is a problem that the internal beat disturbance occurs and the speaker sounds even when there is no received sound.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a side tone circuit that does not cause internal beat interference.

Another object of the present invention is to provide a simple side tone circuit having a small number of oscillators.

[Means for Solving the Problems] In the side tone circuit of the present invention, the frequency for product detection of the intermediate frequency is obtained by dividing the frequency from the variable frequency oscillator by the frequency divider, and the center frequency of the filter is set to the clock frequency. A switched capacitor filter that changes proportionally is provided, the frequency of the variable frequency oscillator and the basic clock are mixed, the frequency obtained by the mixing is used as the clock of the switched capacitor filter, and the mixed clock is obtained. The frequency of the switched capacitor filter is input to the switched capacitor filter, and the output of the switched capacitor filter is used as a side tone.

[Operation] The frequency obtained by mixing the frequency of the variable frequency oscillator for product detection and the basic clock is linked with the reception pitch. When the frequency linked with the reception pitch is divided, higher harmonics will be included, but a side tone can be obtained as a sine wave by passing through a switched capacitor filter.

The center frequency of the switched capacitor filter is proportional to the clock. By equalizing the proportional constant and the frequency division ratio, the center frequency and the pass frequency of the switched capacitor filter can be matched.

In this way, by matching the center frequency of the switched capacitor filter with the frequency of the fundamental wave of the input signal to narrow the pass band, a side tone containing almost no harmonics can be obtained. Also, the local oscillation signal for product detection is divided by the frequency divider and added to the detector, so the frequency and the basic clock signal obtained by mixing the frequency of the variable frequency oscillator and the basic clock are Even if it leaks to the input side and is added to the frequency divider, it is not divided because the level is small. Therefore, no audible frequency is generated and no internal beat interference is generated.

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

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

The tuning of the received radio wave is performed by adjusting the oscillation frequency of the variable frequency oscillator 2.

The frequency of 355 KHz generated by the oscillator 13 is mixed with the first IF of 455 KHz by the mixer 3, and the second IF of 100 KHz is obtained.

The second IF is product-detected by the detector 7, and the obtained audio frequency passes through the change-over switch 11 that works in conjunction with the electric key and the speaker.
Ring twelve.

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

The local oscillation signal for product detection is frequency-divided by the frequency divider 16 and added to the wave detector 7. Therefore, the frequency and the basic clock signal obtained by mixing the frequency of the variable frequency oscillator 14 and the basic clock are mixed in the mixer. Frequency divider 16 leaks to the input side of 17
However, since the level is small, it will not be divided. Therefore, no audible frequency is generated and no internal beat interference is generated.

The frequency generated by the variable frequency oscillator 14 is controlled by the variable resistor 15.
Adjusted in the range of 9.92MHz + 50KHz, audio frequency is 800Hz ± 5
It changes in the range of 00Hz. That is, the reception pitch can be adjusted.

The frequency generated by the variable frequency oscillator 14 is 10
It is mixed with the basic clock of MHz and has a frequency of 80 KHz ± 50 KHz, which is divided into 1/100 by the frequency divider 18, passes through the switched capacitor filter 19, and becomes a sine wave to obtain a side tone.

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

An example of such a switched capacitor filter is MF-10 (model number) manufactured by National Semiconductor.

In this example, the ratio of the clock frequency to the center frequency is 100.
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 sounds the speaker 12.

Since the changeover switch 11 is connected to the Tx side while pressing the electric key, the intermittent state of the electric key can be heard through the speaker.

Side tone frequency is variable resistor for receiving pitch adjustment 15
Changes in the same manner as the frequency of the received sound, and the side tone and the received pitch are interlocked, and a side tone 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 the clock frequency of the switched capacitor filter may be other than 100, and in that case, the frequency divider 16 and 18 divides. The frequency ratio may be the ratio of the center frequency of the switched capacitor filter to the clock frequency.

[Effects of the Invention] As described above, the side tone circuit according to the present invention uses the basic clock as the high frequency mixed for synthesizing the side tones, so that the number of oscillators is small and the circuit is simple.

Further, it is possible to obtain an effect that an audio frequency is not synthesized by an oscillator for obtaining a side tone and leaks into a detector, and an internal beat failure is prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a side tone circuit according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional side tone 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 ... Changeover switch, 12 ... Speaker, 13 ... Oscillator, 14 ... Variable frequency oscillator, 15 ... Variable resistor, 16 ...
… Divider, 17 …… Mixer, 18 …… Divider, 19 …… Switched capacitor filter.

Claims (1)

[Claims] 1. A switched capacitor filter in which a frequency for product detection of an intermediate frequency is obtained by dividing a frequency from a variable frequency oscillator by a frequency divider, and a center frequency of the filter changes in proportion to a clock frequency, The frequency of the variable frequency oscillator and the basic clock are mixed, the frequency obtained by the mixing is used as the clock of the switched capacitor filter, and the input of the switched capacitor filter is obtained by dividing the frequency obtained by the mixing. The side tone circuit is characterized in that the output of the switched capacitor filter is used as a side tone.