JPH0310524A - Cw receiver - Google Patents

Abstract

PURPOSE:To eliminate the need for the readjustment of the center frequency of a peak filter by using a switched capacitor filter for a peak filter passing through an AF, mixing a frequency generated from an oscillation circuit forming a BFO and a frequency generated from a constant frequency oscillator and using the mixed frequency signal as a clock for the switched capacitor filter thereby interlocking the BFO and the peak filter. CONSTITUTION:The oscillated frequency signal from an oscillator circuit 20 is mixed with a frequency signal of 10MHz oscillated by a crystal oscillator at a mixer 23 to generate a clock frequency of a peak filter 4 being a switched capacitor filter. When the oscillated frequency of the oscillator circuit 20 is selected to be 9.92MHz, the AF is 800Hz and the clock frequency of the peak filter is 80kHz and the center frequency of the peak filter is coincident with the AF. When the variable resistor 21 is adjusted to make the oscillating frequency of the oscillator circuit 20 9.9MHz, the AF is 1kHz and the clock frequency of the peak filter 4 is 100kHz, then the center frequency of the peak filter is coincident with the AF automatically.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a receiver that receives CW (unmodulated waves), and in particular, the present invention relates to a receiver that receives CW (unmodulated waves), and in particular, the present invention relates to a receiver that receives CW (unmodulated waves). The present invention relates to a CW receiver that works in conjunction with a filter.

[Prior Art] As shown in Fig. 2, a conventional CW receiver uses an intermediate frequency (
BF added to detector (DET) 1 that detects IF)
O2 and the center frequency of the peak filter 4 were adjusted by separate variable resistors 3 and 5.

In such a receiver, when the frequency generated by the BFO 2 is changed by the variable resistor 3 in the same way as changing the frequency of the sound generated by the speaker 6, the audible frequency passing through the peak filter 4 also changes. The center frequency had to be readjusted with variable resistor 5.

In order to save such trouble, a switched capacitor filter is used as the peak filter 4 as shown in FIG.
The center frequency is changed by the oscillation frequency of the clock oscillator 11, and the oscillation frequency of the clock oscillator 11 and the BFOIO
Even if the oscillation frequency of the peak filter is changed using the co-transition variable resistor 12, it is difficult to match the center frequency of the peak filter to the audible frequency that passes through the peak filter because separate oscillators are used for the clock oscillator and the BFO. It was difficult.

[Problems to be Solved by the Invention] This invention was made in order to solve the problems in the above-mentioned prior art, and it is possible to link the BFO and the peak filter and eliminate the need to readjust the center frequency of the peak filter. No CW
The purpose is to provide a receiver.

[Means for Solving the Problems] The CW receiver of the present invention uses a switched capacitor filter as a peak filter for passing AF, and uses a constant frequency oscillator to generate a frequency generated in an oscillation circuit constituting a BFO for CW reception. The generated frequencies are mixed and used as a clock for the switched capacitor filter, and the BFO and peak filter are interlocked.

[Operation] When the received high frequency CW and the local oscillation output are mixed, it becomes an intermediate frequency of a certain frequency, and the BFO is applied to this intermediate frequency.
Mixing the oscillation outputs produces AF (audio frequency), which is the difference in image frequency. AF passes through a peak filter to improve the S/N ratio, but if you change the BPO oscillation frequency to change the frequency of the blindness generated by the speaker, the A
The frequency of F also changes, and the center frequency of the peak filter becomes A.
It is necessary to change it to match the F frequency.

When a switched capacitor filter is used as the peak filter, its center frequency is proportional to the tarok frequency.

Therefore, the clock of the switched capacitor filter is B
The oscillation frequency of the oscillation circuit constituting the FO and the predetermined frequency generated by the constant frequency oscillator are mixed, and the difference in the image frequency is used as a signal, and the frequency generated by the oscillation circuit constituting the BFO is used as a signal of the frequency of the difference in the image frequency generated by the switched capacitor filter. If the BFO frequency is obtained by dividing the frequency by the ratio of the center frequency and the clock frequency and is mixed with the intermediate frequency to obtain the AF, the AF frequency and the center frequency of the switched capacitor filter will automatically change even if the BFO frequency is changed. Match.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention.

In the figure, 1 is a detector, which mixes the BFO frequency with the 100 KHz intermediate frequency to obtain AF.

AF passes through the peak filter 4 and does not sound the speaker 6.

20 is an oscillation circuit that constitutes the BFO, and variable resistor 2
1 adjusts the oscillation frequency.

The oscillation frequency of the oscillation circuit 20 is divided by 1/100 by the frequency divider 22 to become the BFO frequency.

The oscillation frequency of the oscillation circuit 20 is 1, which is oscillated by a crystal oscillator.
It is mixed with the frequency of 0 MHz in a mixer 23 to generate a clock frequency for the peak filter 4, which is a switched capacitor filter.

The center frequency of peak filter 4 is 1/1 of the clock frequency.
It is 100.

As shown in the figure, the oscillation frequency of the oscillation circuit 20 is set to 9°92
MHz, the AF will be 800 Hz, the tarokk frequency of the peak filter will be 80 KHz, and the center frequency of the peak filter will match the AF. (The center frequency of the peak filter is 1/100 of the clock frequency.) If the oscillation frequency of the oscillation circuit 20 is set to 9.9 MHz by adjusting the variable resistor 21, the AF becomes I K Hz, and the clock of the peak filter 4 becomes 9.9 MHz. The frequency is 100 K) [z
Therefore, the center frequency of the peak filter automatically matches the AF.In this way, even if the AF is changed, such as changing the tone of the speaker, the center frequency of the peak filter will always match the AF.

[Effects of the Invention] As explained above, according to the CW receiver of the present invention,
Since the center frequencies of the BFO and the peak filter move in conjunction with each other, only one adjustment volume is required, making adjustment easy.

Further, it is possible to obtain the effect that only one frequency variable oscillation circuit is required and the circuit is simplified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional technique, and FIG. 3 is a block diagram showing another conventional technique. 1... Detector, 2... BFO13... Variable resistor, 4... Peak filter, 5... Variable resistor, 6...
... Speaker, 10 ... BFOll ... Clock oscillator, 12 ... Variable resistor, 20 ... Oscillation circuit,
21... Variable resistor, 22... Frequency divider, 23...
mixer.

Claims (1)

[Claims] A switched capacitor filter is used as a peak filter that passes the AF, and a frequency generated in an oscillation circuit constituting a BFO for CW reception and a frequency generated in a constant frequency oscillator are mixed and used as a clock for the switched capacitor filter, A CW receiver characterized by interlocking a BFO and a peak filter.