JPH04336815A - Radio telephone system - Google Patents

Abstract

PURPOSE:To realize a discrimination means in which a reception state is discriminated visually, a rough relative distance between a communication opposite party and its own station is discriminated and an alternative communication means is selected in a radio telephone system for a marine mobile job employing a radio wave at a VHF/UHF band. CONSTITUTION:An IF amplifier at the pre-stage of an FM detector of a receiver is constituted of an IF amplifier provided with a successive addition log amplifier and the radio telephone system is provided with a means displaying a reception signal intensity by using the linearity between an input signal level at the input terminal of the IF amplifier and the DC output level of the signal intensity output terminal of the above-mentioned successive addition log amplifier.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a VHF/UHF band radio telephone device for maritime mobile services that is equipped with a superheterodyne receiver and utilizes frequency modulation (hereinafter referred to as FM) radio waves.

0002

2. Description of the Related Art Conventionally, a double superheterodyne system has generally been adopted in the receivers of this type of marine mobile business radio telephone equipment. FIG. 5 shows the configuration of an example of this receiver. Antenna input filter 1, high frequency amplifier (
(hereinafter referred to as amplifier) 2, first mixer 3, first intermediate frequency (
(hereinafter referred to as IF) filter 4, first IF amplifier 5, second
Mixer 6, second IF filter 7, second IF amplifier 8, F
It is composed of an M detector 9, a de-emphasis 10, an audio amplifier 11, a speaker 12, a first local oscillator 13, and a second local oscillator 14.

The received signal applied from the external antenna is band-limited by the antenna input filter 1, and only the received signal in the desired frequency band is amplified by the next high-frequency amplifier 2.
The first mixer 3 converts the signal into a first intermediate frequency by mixing it with a local signal applied from the first local oscillator 13 . The first IF filter 4 passes only the frequency component necessary as the first intermediate frequency among the sum or difference frequency components output from the first mixer 3 and provides a received signal to the next first IF amplifier 5 . With the second mixer 6, the second local oscillator 1
The received signal is frequency-converted again by the local signal applied from 4, and the second intermediate frequency is extracted by the second IF filter 7. Next, the received signal converted to the second intermediate frequency is amplified by the second IF amplifier 8 and then demodulated by the FM detector 9. The demodulated audio signal is subjected to frequency characteristic correction with respect to pre-emphasis on the transmitting side in a de-emphasis 10, amplified in an audio amplifier 11, and finally added to a speaker 12 to be output as audio.

[0004] In FIG. 5, the characteristic feature is that the second IF
A limiter amplifier is used for amplifier 8. The limiter amplifier is used to limit the amplitude of the received signal, remove AM components, and obtain a high gain before the FM signal is demodulated by the FM detector 9 in the next stage. In other words, for the purpose of receiving FM signals, it is sufficient to apply a limiter to the received signal before demodulating it, so an automatic gain control circuit mainly used for receiving AM signals, such as the one provided in shortwave receivers, It's unnecessary.

[0005]

[Problems to be Solved by the Invention] In the conventional receiver of this type of marine mobile business radio telephone equipment, a limiter amplifier is used as an IF amplifier in the front stage of the FM detector. Because the AM component is removed, the input/output amplitude characteristics become non-linear, and it is said that after the IF amplifier, it is not possible to detect the magnitude of the amplitude, that is, the output that is proportional to the strength of the input signal applied to the receiver. There was a problem. That is, because it is not possible to detect an output proportional to the strength of an input signal, conventional marine mobile business radio telephone equipment cannot be equipped with a signal strength indicator (S meter). (1). It is not possible to judge the reception status visually. (2). Because the approximate relative distance between the communication partner and the own station is not known, if a ship is operating in the marginal sea area of the communication range, communication may suddenly be interrupted without a decision to switch to an alternative communication method. . (3). There were problems such as the inability to use directional antennas. The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a marine mobile business radio telephone device equipped with a received signal strength indicator.

[0006]

[Means for Solving the Problems] In the radio telephone device of the present invention, the IF amplifier at the front stage of the FM detector of the receiver is constituted by an IF amplifier equipped with a sequential addition type log amplifier, and the input terminal of the IF amplifier is A received signal strength indicator is provided by utilizing the linearity between the input signal level (in decibels) and the DC output level of the signal strength output terminal of the successive addition type log amplifier.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 5 indicate the same or corresponding parts, and 20 is a successive addition type log amplifier that generates a DC output according to the amplitude of the input signal and removes AM components like a conventional limiter amplifier. A second IF amplifier 30 generates a limiter output suitable for the FM detector 9;
This is a received signal strength indicator that receives the DC output of the F amplifier and displays the received signal strength.

FIG. 2 shows an example of the configuration of the second IF amplifier 20 shown in FIG. In the figure, 21 is the input terminal of the second IF amplifier 20 connected to the output of the second IF filter 7 in FIG.
22 is a unit limiter amplifier, 23 is a unit log amplifier (including a detection circuit), 24 is a current synthesis circuit, 25 is a load resistance of the current synthesis circuit 24, 26 is a signal strength output terminal, and 27 is the FM detector 9 of FIG. This is the limiter output terminal connected to. The current synthesis circuit 24 takes the form of sequentially adding the outputs of the unit log amplifiers 23 connected to the unit limiter amplifiers 22 connected in cascade. Here, the input/output relationship between the input terminal 21 and the limiter output terminal 27 functions similarly to that of the limiter amplifier 8 of FIG. 5. On the other hand, the input/output relationship between the input end 21 and the signal strength output end 26 is expressed as the input signal level on the log scale on the horizontal axis and the DC output level on the linear scale. Linearity is obtained over the range. This IF amplifier 2
0, a commercially available amplifier such as NJM2232A (manufactured by New Japan Radio) can be used as is.

FIG. 3 shows an example of the configuration of the received signal strength indicator 30 of FIG. 1. In the figure, 31 is an input terminal connected to the signal strength output terminal 26 of FIG. 2, 32 is a power input terminal, and 33
is a bypass capacitor, and 34 and 37 are operational amplifiers, which are actually commercially available JM3404A (manufactured by New Japan Radio) or the like. 35 is a sensitivity adjuster for the meter 36, 38, 39
is a fixed resistor, and 40 is a zero point adjuster for the meter 36. Here, if a scale corresponding to the antenna input of the receiver is written on the indicator board of the meter 36 in advance, the user can visually check how the other party is receiving the signal by reading the meter deflection. .

FIG. 4 shows another example of the configuration of the received signal strength indicator 30 of FIG. 1. In the figure, 31 is a signal strength input terminal, 41 is an A/D converter, 42 is a microcomputer, and 43 is a liquid crystal display. Here, the microcomputer 42 receives the output of the A/D converter 41, converts the digital code into the antenna input level of the receiver, and displays the numerical value or bar graph on the liquid crystal display 43, so that the user can see it visually. You can check the admission status.

[0011]

[Effects of the Invention] As explained above, according to the present invention,
Maritime mobile business radio telephone equipment that uses radio waves in the VHF/UHF band can now be equipped with a received signal strength indicator while maintaining high gain performance, making it possible to visually judge the reception status and to communicate with the other party Since the approximate relative distance to the own station can be determined, it is possible to make a decision to switch to an alternative communication method even if the ship is operating in the marginal sea area of the notification range.
Further, there are advantages such as being able to use a directional antenna.

[Brief explanation of drawings]

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

FIG. 2 is a block diagram showing an example of the configuration of a second IF amplifier in FIG. 1;

FIG. 3 is a circuit diagram showing an example of the configuration of the received signal strength indicator of FIG. 1;

FIG. 4 is a block diagram showing another example of the configuration of the received signal strength indicator in FIG. 1;

FIG. 5 is a block diagram showing the configuration of an example of a receiver of a conventional radio telephone device of this type.

[Explanation of symbols]

1 Antenna input filter 2 High frequency amplifier 3 First mixer 4 First IF filter 5 First IF amplifier 6 Second mixer 7 Second IF filter 9 FM detector 10 De-emphasis 11 Audio amplifier 12 Speaker 13 First local oscillator 14 Second local oscillator 20 2nd IF amplifier 30 Received signal strength indicator

Claims (1)

[Claims] 1. A wireless telephone device for maritime mobile business in the VHF/UHF band that is equipped with a superheterodyne receiver and utilizes frequency modulation radio waves, comprising: an intermediate frequency amplifier upstream of an FM detector of the receiver; , consisting of an intermediate frequency amplifier equipped with a successive addition log amplifier, between the input signal level (in decibels) at the input end of the intermediate frequency amplifier and the DC output level at the signal strength output end of the successive addition log amplifier. What is claimed is: 1. A wireless telephone device comprising means for displaying received signal strength using linearity of the signal.