JPS61141225A - Am receiver - Google Patents

Abstract

PURPOSE:To reduce fading effect in one set of receiver by constituting a local oscillator with a PLL oscillator setting two independent frequencies. CONSTITUTION:A signal of an RF amplifier 1 and a local oscillation signal from PLL oscillators 6, 7 obtained by the switching of a switch 5 are mixed (2), an AM signal selected and amplified by an IF amplifier 3 being its output is demodulated by a detector 4 and amplified by an AF amplifier 10 and outputted from a speaker 11. A control signal for the switch 5 is formed by detecting a level of a reception signal or a fluctuating speed of a reception signal obtained from the detector 4. The frequency code of oscillators 6, 7 is controlled independently respectively by a controller 8 having >=2 frequency code storage sections and the frequency code required for the oscillators 6, 7 is set from the two difference reception frequencies and the intermediate frequency. The reference signal is fed to both the PLL oscillators from a reference oscillator 9. Thus, the international broadcast using two frequencies is received while decreasing the effect of fading.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an AM receiver with improved performance in shortwave reception.

Conventional technology In recent years, the number of AM receivers capable of SW reception has been increasing.Referring to the drawings below, we will explain how to receive international broadcasting using a conventional AM receiver simultaneously using two or more frequencies in the SW band. An example of the method will be described.

FIG. 2 shows an example of reception using two conventional AM receivers. In FIG. 2, 12.13 is an AM receiver.

International broadcasts using two or more frequencies at the same time are usually placed on different meter bands, so AM receivers 12 and 13 are used to receive international broadcasts with the same content on different meter bands. Set as desired.

By receiving international broadcasts in this manner, it is possible to reduce the effect of fading phenomenon peculiar to the SW band. In other words, since the AM receivers 12 and 13 receive different frequency bands, they exhibit different fading phenomena, and the audio outputs of the two AM receivers cancel each other out, resulting in reception due to fading phenomena. It is possible to reduce the deterioration of the condition.

Problems to be Solved by the Invention However, in order to improve the characteristics of broadcast reception by such means, two AM receivers are required, which increases the cost and causes problems in that the operation is complicated. Was.

In view of the above-mentioned problems, the present invention provides an AM receiver configured so that one receiver provides the same effect as using two receivers.

Means for Solving the Problems In order to solve the above problems, the AM receiver of the present invention has two
Equipped with a PLL oscillator, mixer, IF amplifier, and detector that can set two independent frequencies, it receives two broadcast waves by switching the local oscillation frequency, and depending on the reception condition, sends a better detection output to the speaker via the AF amplifier. It is configured so that it can supply and receive broadcasts.

Function: The present invention uses the superheterodyne receiving circuit configured as described above to receive international broadcasting using two frequencies, and outputs the AF multiplied signal from the speaker through the AF amplifier. This made it possible to prevent deterioration of reception characteristics due to fading, which could only be achieved by using two receivers.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an AM receiver showing an embodiment of the present invention. In FIG. 1, 1 is an untuned wideband RF amplifier;
2 is a mixer, 3 is an intermediate frequency amplifier, and 4 is a detector.

6 is a switch, and 6 and 7 are local oscillation circuits using PLL oscillators. The signal of the RF amplifier 1 and the local oscillation signal obtained by switching the outputs of the PLL oscillators 6 and 7 by the switch 6) are supplied to the mixer 2, and from the output thereof, the I
The intermediate frequency is selectively amplified by the F amplifier 3 and the detector 4
A superheterodyne AM receiving circuit is constructed in which the AM signal is demodulated and an AF multiplied signal is obtained. The control signal for the switch 6 is generated by detecting the level or fluctuation speed of the received signal obtained by the detector 4, and the output of the detector 4 is amplified by an AF multiplied signal by an AF amplifier 10 and supplied to the speaker 11. I am getting audio output.

The local oscillation circuit will now be described in detail. Local oscillation signals are supplied as outputs of PLL oscillators 6 and 7. The frequency codes of this PLL oscillator can be independently controlled by a control device 8 having two or more frequency code storage units, and each PLL oscillator can be controlled from two different reception frequencies and two different intermediate frequencies. The required frequency code is set. The reference signal at this time is supplied from the reference oscillator 9 to both PLL oscillators. When receiving international broadcasts using two frequencies, you can assign each frequency code to the PLL oscillator 6.7 and save it in the memory at the same time to simplify the next operation. Become.

Effects of the Invention As described above, the present invention makes it possible to realize the means for reducing fading effects that was obtained by using two receivers with a single receiver, and that it is possible to achieve the fading effect reduction that was obtained by using two receivers. 2 by switching the oscillation frequency.
This ensures the characteristics of international broadcast reception carried out on high frequencies. Furthermore, reception stability is ensured by using the same reference frequency, and operability is further improved by control by a control device having a frequency code storage section.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an AM receiver in an embodiment of the present invention,
FIG. 2 shows a conventional example. 1...RF amplifier, 2...Mixer, 3
...IF amplifier, 4...Detector, 6,
7...PLL oscillator, 8...Control device, 9...Reference oscillator, 1o...AF amplifier, 11...Speaker.

Claims (1)

[Claims] The AM receiver is configured using a superheterodyne method, and the local oscillator is configured by a PLL oscillator that can set two independent frequencies, and a switch that operates the two oscillation signals generated by this by changes in the received signal. The resulting local oscillation signal is supplied to a mixer, the resulting intermediate frequency signal is amplified and detected, and the resulting AF signal is sent to the AF.
The frequency code of the PLL oscillator, which is configured to be supplied to a speaker through an amplifier to receive broadcasting, and can set two independent frequencies, is controlled by the same control device having two or more frequency code storage units. An AM receiver characterized by simultaneously using reference frequencies from the same oscillator.