JPH09153827A - Receiving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a double-signal characteristic and to make a reception signal loss min. by attenuating a noise component through the use of a reception element without using a diode switch. SOLUTION: A reception signal S11 to be a target is inputted to a high frequency amplifier circuit 11 together with a noise signal and frequency- converted into an IF band signal S12 by a local oscillation circuit 13 and a mixer 12 after amplifying. A noise signal, after selecting a frequency which is different from a reception target signal frequency and also where another communication is not executed, amplifying the frequency by the high frequency amplifier circuit 21 and, after that, oscillating it by the local oscillation frequency so as to obtain the same frequency as an IF band frequency in the local oscillation circuit 23, is converted into the IF band signal S13 by the mixer 12. A high frequency transformer 14 synthesizes the IF band signals S12 and S13 by an opposite phase. Therefore, the loss of the target signal is made to be min. so that the noise component is attenuated. The reception target signal where the noise component is attenuated is inputted to a narrow band BPF 15 and inputted to an intermediate frequency amplifier and a detection circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver, and more particularly to a noise elimination system in an SSB / AM receiver.

[0002]

2. Description of the Related Art A conventional noise elimination method in an SSB / AM receiver will be described with reference to the block diagram of FIG. In FIG. 2, the reception signal S1 from the antenna is amplified by the high frequency amplifier circuit 1 and mixed with the local oscillation signal from the local oscillation circuit 3 in the mixer 2 to obtain I
Frequency conversion is performed on the F (intermediate frequency) band signal S2.

This IF signal S2 is input to a diode switch 6 via a wide band BPF (band pass filter) 4. In the diode switch 6, the blanking pulse generated in the noise portion detected by the noise detection circuit 5 turns off the reception signal only during a period when there is noise, and removes the noise component. After that, the target reception signal S3 is obtained via the narrow band BPF 7 for SSB / AM, and the IF amplification circuit and the detection circuit of the next stage (both not shown).
Output to

Further, as disclosed in Japanese Patent Laid-Open No. 59-115628, a receiving signal for receiving only a noise component is separately provided in addition to a receiving device for receiving a desired receiving signal, and these receiving devices are provided. A method of canceling noise in a low frequency stage after detecting the output has also been proposed.

[0005]

In the prior art shown in FIG. 2, the diode switch 6 controls on / off of the IF band received signal in order to blank the noise component. Due to the switching operation of the on / off control, the two-signal characteristic in reception is deteriorated, a short-distance interfering wave appears in the reception band, and there is a drawback that intermodulation is weak.

Therefore, if the band is narrowed so that the near-field interference wave is removed by the wide band BPF 4 after the mixer 2 (for example, if SSB is 3 KHz and AM is 6 KHz, the influence of two signal interference is improved). Since the noise waveform is blunted and delay occurs, the time for blanking the noise becomes long and the time for turning off the target reception signal also becomes long, resulting in a large loss of the target reception signal.

As a result, the degree of intelligibility is lowered. Therefore, the band of the wide band BPF 4 is generally set to 20 to 40 KHz in the case of SSB / AM reception.

Also, as in the technique disclosed in Japanese Patent Laid-Open No. 59-115628, the method of canceling the noise component by mixing the received signal and the noise component in opposite phases in the low frequency portion after detection is 2
A low noise range is possible without deteriorating the signal characteristics.

However, as described above, the received signal is I
When passing through the F filter and the amplifying element, the noise signal has a pulse shape and the rising edge of the waveform is steep, so that the waveform is blunted and a delay occurs, and most of the target signal is lost. Is lowered, which is not preferable.

An object of the present invention is to provide a receiving apparatus which can effectively remove only noise components without lowering the intelligibility of received signals.

[0011]

According to the present invention, there is provided a receiving high frequency circuit for receiving a target signal and a receiving frequency converting circuit for converting an output of the receiving high frequency circuit into an intermediate frequency. An apparatus, comprising: a noise high-frequency circuit that receives only a noise signal; a noise frequency conversion circuit that converts the output of the noise high-frequency circuit to the intermediate frequency; the reception frequency conversion circuit and the noise frequency conversion circuit. And a mixing means for mixing both outputs with the circuit in opposite phase at the intermediate frequency.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention will be described.
RF (high frequency) circuit for the originally intended received signal and I
In addition to the F conversion circuit, an RF circuit and an IF conversion circuit that receive only the noise component are provided, and both IF outputs are mixed in antiphase at the IF stage to cancel the noise component.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. A target reception signal S11 is input to a high frequency amplifier circuit 11 together with a noise signal, and after amplification, an IF band signal is generated by a local oscillator circuit 13 and a mixer 12. The frequency is converted to S12.

Further, the noise signal S21 is a frequency different from the frequency of the signal to be received and a frequency at which other communication is not performed (generally, communication is low in the 40 MHz band and a noise component generated by an automobile or the like is high). Used),
After being amplified by the high frequency amplifier circuit 21, the local oscillator circuit 23
It is oscillated at the local oscillation frequency so as to have the same frequency as the F band frequency S12, and is converted into the IF band signal S13 by the mixer 22.

The high frequency transformer 14 is a circuit for synthesizing these IF band signals S12 and S13 in opposite phases. Since it is a passive element, the two signal characteristics are not deteriorated and the loss of the target signal is minimized. Noise component can be attenuated. The reception target signal S31 in which the noise component is attenuated is input to the narrow band BPF 15 and is input to an intermediate frequency amplifier and a detection circuit (not shown).

[0017]

As described above, according to the present invention, since the noise component is attenuated by using the passive element without using the diode switch, there is an effect that the two-signal characteristic can be improved. In addition, since the reverse phase cancellation of noise is not performed in the low frequency stage and the processing is performed in the IF band where the noise pulse has a steep waveform, there is an effect that the loss of the target reception signal is minimized. .

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a conventional receiving device.

[Explanation of symbols]

 11,21 High frequency amplifier circuit 12,22 Mixer 13,23 Local oscillation circuit 14 High frequency transformer 15 Narrow band BPF

Claims (2)

[Claims] 1. A receiving device having a receiving high-frequency circuit for receiving a target signal and a receiving frequency conversion circuit for converting an output of the receiving high-frequency circuit into an intermediate frequency, which receives only a noise signal. A high frequency circuit for noise, a frequency conversion circuit for noise that converts the output of the high frequency circuit for noise to the intermediate frequency, and both outputs of the frequency conversion circuit for reception and the frequency conversion circuit for noise at an intermediate frequency. A receiving device, comprising: mixing means for mixing in reverse phase. 2. The receiving apparatus according to claim 1, wherein the mixing means is a high frequency transformer which receives the both outputs as inputs.