JPH0642640B2 - Transmitter / receiver self-interference prevention method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a self-interference prevention method for a transceiver that prevents internal interference in a half-duplex FM transceiver, and more particularly to a method for preventing self-interference in a transceiver during reception. The present invention relates to a method for preventing self-interference in a transceiver that can prevent interference from a transmitting circuit to a receiving circuit.

(Prior Art) Half-duplex F that can communicate in both directions at the same time as interactive communication such as transceiver
A transceiver using the M method is used. The half-duplex method is suitable for relatively low-speed communication in which the switching time can be ignored because the data transmission direction is switched alternately.
In particular, it is often used for conversational communication and has the advantage that both sides can use the transmission line of the same frequency band.

The configuration of a conventional half-duplex FM transceiver will be described with reference to the configuration diagram of FIG.

In the half-duplex FM system, a switch 15 is provided in a portion connected to the antenna in order to use the transmission line only for one of transmission and reception for a specific time, and the transmission line is transmitted by the switch 15 or It is the one selected for reception.

The transmitter side of the transceiver will be described. A low frequency amplifier 1 for amplifying a low frequency of a transmission input signal, a voltage controlled oscillator (VCO) 2 for performing FM modulation by changing an oscillation frequency by a control voltage, and a local portion. Due to the mixer 3 for performing frequency conversion by mixing the frequency from the oscillator 6 and the frequency modulated by the voltage controlled oscillator 2, the frequency conversion function of the mixer 3, parasitic oscillation of the high frequency power amplifier 5, etc. It is composed of a band limiting filter 4 that removes spurious emission of radio waves from the transmitter at a frequency outside the specified transmission band, and a high-frequency power amplifier 5 that amplifies power for transmission. The output signal is output to the antenna via the switch 15.

To describe the receiving side of the transceiver, the switch 15 is configured to connect the antenna to the receiving circuit on the receiving side at the time of reception, and the band limiting filter 7 for removing unnecessary waves of the input signal input from the antenna, and the band limiting filter. A high-frequency amplifier 8 which passes through the filter 7 and amplifies high-frequency waves, and a local oscillator 6
A mixer 9 for performing frequency conversion by mixing the frequency from the above and the frequency amplified by the high frequency amplifier 8, and a filter 10 for extracting an intermediate frequency of the frequencies subjected to the frequency conversion.
A frequency discriminator 11 for extracting a modulation signal proportional to the frequency deviation of the input signal in a frequency modulation type radio receiver; and a low frequency amplifier 12 for amplifying the low frequency of the modulation signal.
And the low-frequency amplifier 12 outputs a reception output signal on the reception side.

In the configuration of the above-mentioned conventional half-duplex FM transceiver, if the transmitting circuit on the transmitting side is operating at the time of reception, the output of the transmitting side may interfere with the receiving side. At this time, the output from the local oscillator 6 is cut off from being input to the mixer 3 on the transmission side, and the power of the high-frequency power amplifier 5 is further cut off so that the output from the transmission side is not transmitted. There are things that prevent interference to the side.

(Problems to be Solved by the Invention) However, in the method of preventing interference from the transmission circuit to the reception circuit at the time of reception in the configuration of the conventional half-duplex FM transceiver, for example, radio frequency is time-divided, Time division multiple access (TDMA), in which a specific time period is assigned to a correspondent and communication is performed in the assigned time period
Like the system, the transmission speed of the wireless line is several to several thousand times faster than the original information transmission speed, so it is necessary to switch between transmission and reception frequently, and the start-up of transmission is quick. Therefore, there is a problem that the power supply of the high frequency power amplifier 5 on the transmission side cannot be turned off and the TDMA system cannot be supported.

Also in the general half-duplex FM system, even when the output from the local oscillator 6 at the time of reception is cut off from the mixer 3 on the transmission side or the power supply of the high frequency power amplifier 5 is cut off, Since there is no switch (15) with excellent isolation (insulation), there is a problem that the output of the transmitting side may leak to the receiving side via the switch (15) and cause interference. there were.

The present invention has been made in view of the above circumstances, and by offsetting the frequency on the transmitting side during reception, it is possible to prevent interference from the transmitting circuit on the transmitting side to the receiving circuit on the receiving side. The purpose is to provide a prevention method.

(Means for Solving the Problems) The present invention for solving the problems of the above-mentioned conventional example is directed to a transmitter / receiver self-preventing output interference from a transmitting side to a receiving side in a half-duplex FM type transceiver. In the interference prevention method, a DC voltage that causes a frequency larger than the frequency band of reception at the time of reception is added to the modulation input of the voltage controlled oscillator that performs FM modulation on the transmission side, and the frequency on the transmission side is out of the reception band. It is characterized in that it is offset as described above and removed by the band limiting filter on the receiving side.

(Operation) According to the present invention, the switch between the low-frequency amplifier and the voltage-controlled oscillator is switched at the time of reception, the voltage generator and the voltage-controlled oscillator are connected, and the output frequency from the voltage generator to the reception band is set. Since a constant DC voltage that can be offset to the outside is given, even if the output leaks from the transmitter circuit on the transmitter side to the receiver circuit on the receiver side, it is removed by a band-limiting filter in the receiver circuit. In addition, the TDMA system of high-speed processing can be supported by the quick switching of the switch connected to the voltage generator, and the interference can be prevented even in the TDMA system.

(Example) An example of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a half-duplex FM system transceiver according to an embodiment of the present invention. The same reference numerals are given to parts having the same configurations as those in FIG.

The half-duplex FM system transceiver of this embodiment is composed of a transmission circuit on the transmission side (upper half portion of FIG. 1) and a reception circuit on the reception side (lower half portion of FIG. 1). A switch 15 for selecting a transmission path for transmission or reception is provided at a portion where each circuit is connected to the antenna.

The transmission circuit on the transmission side will be described. A low frequency amplifier 1 for amplifying a low frequency of a transmission input signal, a voltage controlled oscillator (VCO) 2 for performing FM modulation by changing a generation frequency by a control voltage, and a local portion. Due to the mixer 3 for performing frequency conversion by mixing the frequency from the oscillator 6 and the frequency modulated by the voltage controlled oscillator 2, the frequency conversion function of the mixer 3, parasitic oscillation of the high frequency power amplifier 5, etc. It is composed of a band limiting filter 4 that removes spurious emission from the transmitter at a frequency outside the specified transmission band, and a high frequency power amplifier 5 that amplifies power for transmission. The signal is output to the antenna via the switch 15.

In this embodiment, a switch 13 for connecting the low frequency amplifier 1 and the voltage controlled oscillator 2 is provided between the low frequency amplifier 1 and the voltage controlled oscillator (VCO) 2 when not receiving, When receiving, the switch 13
Is configured to connect the voltage generator 14 for generating a constant DC voltage and the voltage controlled oscillator 2. That is, the switch 13 switches the connection to the voltage controlled oscillator 2 from the low frequency amplifier 1 to the voltage generator 14 in conjunction with the reception operation.

Further, the voltage generator 14 provides a constant DC voltage capable of offsetting the output frequency on the transmission side so as to be out of the reception band on the reception side.

Next, the receiving circuit on the receiving side will be described. A band limiting filter 7 that removes an unwanted wave of an input signal that is input from an antenna via a switch 15, and a high frequency amplifier that passes the band limiting filter 7 and amplifies a high frequency. 8, a mixer 9 for performing frequency conversion by mixing a frequency from the local oscillator 6 and a frequency high-frequency amplified by the high-frequency amplifier 8, a filter 10 for extracting an intermediate frequency of the frequency-converted frequency, and a frequency modulation method. In the wireless receiver of, the frequency discriminator 11 extracts a modulation signal proportional to the frequency shift amount of the input signal, and the low frequency amplifier 12 that amplifies the low frequency of the modulation signal. The reception output signal is output.

Next, a method of preventing self-interference of a transceiver according to this embodiment will be described with reference to FIG. 1 and FIG. 2 which is a partially enlarged view of FIG.

First, at the time of transmission, the switch 13 connects the low frequency amplifier 1 and the voltage controlled oscillator 2, the transmission input signal is input to the low frequency amplifier 1, the low frequency is amplified, and the voltage controlled oscillator 2 is transmitted. Then, the FM modulation is carried out, the data is transmitted to the mixer 3, and then the normal transmission operation is carried out.

Then, at the time of reception, the switch 13 is switched,
The voltage generator 14 for generating a constant DC voltage is connected to the voltage controlled oscillator 2. Voltage generator 1
Reference numeral 4 gives a constant DC voltage that can offset the output frequency on the transmission side so as to be out of the reception band. For example, when the bias voltage is 2 V, the reception band becomes 10.7 MHz ± 20 MHz. , To generate a frequency outside this reception band, a constant DC voltage is about 4
It means that more than V is required.

According to the interference prevention method of the present embodiment, the switch 13 between the low frequency amplifier 1 and the voltage controlled oscillator 2 is switched at the time of reception to connect the voltage generator 14 and the voltage controlled oscillator 2,
Since a constant DC voltage that can offset the output frequency of the transmission side from the voltage generator 14 to be out of the reception band is provided, the output circuit does not leak from the transmission circuit of the transmission side to the reception circuit of the reception side. Even if there is, there is an effect that the reception output signal on the receiving side can be accurately output without being interfered by being removed by the band limiting filter 7 in the receiving circuit.

Further, according to the present embodiment, the transmission speed of the wireless circuit is several to several thousand times higher than the original information transmission speed like the TDMA system, and therefore it is necessary to frequently switch between transmission and reception. Even in some cases, since it is not necessary to start up the voltage controlled oscillator 2, the switching can be performed quickly with the switch 13, so the TD
Even in the MA method, there is an effect that interference prevention is effective.

(Effect of the Invention) According to the present invention, the switch between the low-frequency amplifier and the voltage-controlled oscillator is switched at the time of reception, the voltage generator and the voltage-controlled oscillator are connected, and the output frequency from the voltage generator to the transmission side is changed. Since it provides a constant DC voltage that can be offset so that it is out of the reception band, even if there is an output leak from the transmission circuit on the transmission side to the reception circuit on the reception side, a band limiting filter in the reception circuit can be used. There is no effect of being removed and causing interference, and by the rapid switching of the switch connected to the voltage generator, it becomes possible to support a high-speed processing TDMA system, and there is an effect that interference can be prevented even in the TDMA system.

[Brief description of drawings]

FIG. 1 is a block diagram of a half-duplex transceiver according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG.
It is a block diagram of a dual transceiver. 1 ... Low-frequency amplifier 2 ... Voltage-controlled oscillator 3 ... Mixer 4 ... Band limiting filter 5 ... High-frequency power amplifier 6 ... Local oscillator 7 ... Band limiting filter 8 ... High-frequency amplifier 9 ... Mixer 10 ... … Intermediate frequency filter 11 …… Frequency discriminator 12 …… Low frequency amplifier 13 …… Switch 14 …… Voltage generator 15 …… Switch

Claims (1)

[Claims] 1. A method of preventing self-interference of a transmitter / receiver for preventing output interference from a transmitter side to a receiver side in a half-duplex FM transceiver, wherein a frequency larger than a frequency bandwidth of reception occurs at the time of reception. A direct current voltage is applied to a modulation input of a voltage controlled oscillator that performs FM modulation on the transmission side, the frequency on the transmission side is offset so as to be out of a reception band, and is removed by a band limiting filter on the reception side. Self-interference prevention method for transceivers.