JPH0551212B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a PLL synthesizer circuit equipped with two voltage-controlled oscillator circuits for transmission and reception in a simplex system (press talk system) radio device. It is.

“Prior Art” Conventionally, this type of circuit has been known as a voltage controlled oscillation circuit for transmitting local oscillation (hereinafter referred to as a transmitting local oscillation circuit), as shown in Figure 2.
VCO) 1 and a voltage controlled oscillation circuit for receiving local oscillation (hereinafter referred to as receiving VCO) 2 are coupled to isolators 5 and 6 via buffer amplifiers 3 and 4, respectively, and the outputs of these isolators 5 and 6 are The side is branched by couplers 7 and 8, and the transmitting side is connected to the transmitting PLL synthesizer output terminal 9.
is coupled to the prescaler 10, and the receiving side receives
is coupled to the PLL synthesizer output terminal 11 and the prescaler 10;
0 is for PLL including phase comparator and variable frequency divider
A reference oscillation circuit 14 is connected to the input side of this PLL IC 12 via a frequency dividing circuit 13, and a transmitting loop filter 16 and a receiving loop filter are connected to the output side via a switching circuit 15. 1
The transmitting loop filter 16 was coupled to the transmitting VCO 1, and the receiving loop filter 17 was coupled to the receiving VCO 2.

``Problems to be solved by the invention'' In the conventional circuit shown in Figure 2, the transmission
There was a problem in that the VCO and the receiving VCO each required special parts such as isolators and couplers to prevent reflected waves, making them expensive.

"Means for Solving the Problems" The present invention has been made to solve the above-mentioned problems, and is a press talk type radio device in which one PLL IC is connected via a switching circuit. In a PLL synthesizer circuit that is switchably coupled to two VCOs, a transmitting VCO and a receiving VCO, to control the transmitting and receiving frequencies, the output of the transmitting VCO is connected to a hybrid circuit via a buffer amplifier. coupling the output of the receiving VCO to the other input terminal of the hybrid circuit via a buffer amplifier;
One output terminal of the hybrid circuit is coupled to the PLL synthesizer output terminal via a switching circuit interlocking with the switching circuit, and the other output terminal of the hybrid circuit is coupled to the PLL synthesizer output terminal via a prescaler.
It is combined with a PLL IC.

``Operation'' Assuming that all ports (input/output terminals) of a hybrid circuit are matched with the circuits connected to it, the output of the buffer amplifier is attenuated by a predetermined value due to the nature of the hybrid circuit, and the two ports are attenuated. It is branched into. The signal reflected at the input terminal of the branched subsequent circuit is absorbed by the receiving buffer amplifier when transmitting, and by the transmitting buffer amplifier when receiving, and is not reflected to the other buffer amplifier, causing no adverse effect on the voltage controlled oscillator circuit. Not affected.

“Example” An example of the present invention will be described below based on the drawings.

In the present invention, as shown in FIG. 1, two isolators 5, 6 and two couplers 7, 8 in the conventional circuit of FIG. 2 are omitted, and a branch line type 3 dB
This uses an attenuation hybrid circuit 18. That is, the transmission VCO 1 is coupled to one input terminal 19 of the hybrid circuit 18 via the transmission buffer amplifier 3, and similarly, the reception VCO 1 is connected to one input terminal 19 of the hybrid circuit 18.
The VCO 2 is coupled to the other input terminal 20 of the hybrid circuit 18 via the receiving buffer amplifier 4, one output terminal 21 of this hybrid circuit 18 is coupled to the common terminal 24 of the switching circuit 23, and the other output terminal 22 is coupled to prescaler 10. The switching circuit 23 is switched in conjunction with the switching circuit 15. Other configurations are the same as the conventional circuit shown in FIG.

In the above configuration, during transmission, the switching circuits 23 and 15 are switched to the transmitting side.

Here, if all the input/output terminals 19, 20, 21, 22 of the hybrid circuit 18 are matched with the circuits 3, 4, 23, 10 connected to these, the hybrid circuit 18 with 3 dB attenuation Due to its nature, the output of the transmitting buffer amplifier 3 is branched into two output terminals 21 and 22 with 3 dB attenuation. The signals reflected at the input terminals of the circuits 23 and 10 after being branched are absorbed by the output matching circuit of the receiving buffer amplifier 4, so there is no reflection to the transmitting buffer amplifier 3, and two signals, one for transmitting and one for receiving, are absorbed by the output matching circuit of the receiving buffer amplifier 4.
No adverse effect on VCO1 and 2.

During reception, switching circuits 23 and 15 are switched to the receiving side, thereby performing substantially the same operation as during transmission.

In addition, when transmitting, the transmitting VCO1 operates,
The reception VCO 2 stops oscillation, and during reception, the reception VCO 2 operates and the transmission VCO 1 stops oscillation. In addition, two buffer amplifiers 3,
4 is always in operation.

[Effects of the Invention] Since the present invention is configured as described above, the functions of an isolator and a coupler can be substituted by a hybrid circuit, and it can be provided at an extremely low cost.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a PLL synthesizer circuit according to the present invention, and FIG. 2 is a conventional circuit diagram. 1... Voltage controlled oscillation circuit for transmitting local oscillation (VCO for transmitting), 2... Voltage controlled oscillating circuit for receiving local oscillation (VCO for receiving), 3... Buffer amplifier for transmitting, 4... Buffer amplifier for receiving, 9... ... Output terminal for transmission, 10 ... Prescaler, 11 ... Output terminal for reception, 12 ... PLL IC, 13 ... Frequency division circuit, 14 ... Reference oscillation circuit, 15 ... Switching circuit, 16 ... Transmission Reliable loop filter, 17... Loop filter for reception, 18... Hybrid circuit, 19, 20... Input terminal, 21, 22... Output terminal, 23... Switching circuit, 24... Common terminal.

Claims (1)

[Claims] 1. A press-talk type radio device, which has one
A PLL synthesizer circuit in which a PLL IC 12 is switchably coupled to two voltage controlled oscillation circuits 1 and 2 for transmitting local oscillation and receiving local oscillation via a switching circuit 15 to control the transmitting and receiving frequencies. The output of the voltage controlled oscillation circuit 1 for transmitting local oscillation is coupled to one input terminal 19 of the hybrid circuit 18 via the buffer amplifier 3, and the output of the voltage controlled oscillating circuit 2 for receiving local oscillation is coupled to the buffer amplifier 4. to the other input terminal 20 of the hybrid circuit 18 via one output terminal 2 of the hybrid circuit 18 .
1 to the PLL synthesizer output terminals 9 and 11 via a switching circuit 23 interlocking with the switching circuit 15, and the other output terminal 2 of the hybrid circuit 18.
2 to the PLL IC 1 via the prescaler 10.
2. A PLL synthesizer circuit characterized in that the PLL synthesizer circuit is formed by combining two. 2. The hybrid circuit is a PLL according to claim 1 consisting of a branch line type with 3db attenuation.
synthesizer circuit.