JPH0528838Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field This invention relates to a switching circuit for a local oscillation output amplification circuit that switches the local oscillation output signal of communication equipment such as a transceiver, and is particularly suitable for low power consumption such as portable sets. The present invention relates to a local oscillation output amplification circuit with two transmission and reception systems that reduces current and components and enables high isolation.

(b) Problems to be solved by the prior art/device Conventionally, the circuits shown in Figures 2 and 3 have often been provided as two-system local oscillation output amplification circuits for transmitting and receiving communication equipment. .

FIG. 2 is a circuit diagram composed of two systems of output amplification circuits, and FIG. 3 is a circuit diagram using switching diodes.

In the figure, 1 is a local oscillation circuit, 2 is a second load to which a high-level local oscillation output signal is supplied, and 3 is a local oscillation circuit.
is the first one to which a low level local oscillator output signal is supplied.
The load 4 is a switch that switches the power supply.

The local oscillation amplifier circuit shown in FIG. 2 is formed by two systems of output amplifier circuits having the same configuration. A second load 2 is connected to the amplification transistor Q10, and a first load 3 is connected to the amplification transistor Q11. The output signal from local oscillation circuit 1 is supplied to the base of amplification transistor Q11 via coupling capacitor C12 and to the base of amplification transistor Q10 via coupling capacitor C10.

On the other hand, the power supply VCC is supplied to the amplifying transistor Q11 or Q10 via the switch 4, and when the switch 4 is switched to the b contact side, Q11 becomes active and the output signal is applied to the first load, causing the switch to switch. When the switch 4 is switched to the a-contact side, Q10 becomes active and an output signal is applied to the second load.

At this time, for example, if the first load 3 is a receiving mixer circuit of a communication device, the local oscillation output signal may be a relatively low level signal, so the amplification transistor Q
11 operates at a relatively low gain, and the second
When the load 2 is a transmission amplifier circuit, a relatively high level local oscillation output signal is required, and the base bias voltage, collector load impedance, etc. are selected so that the amplification transistor Q10 operates at a relatively high gain. be done.

In this way, the output amplifier circuits Q11 and Q10 supply low-level and high-level local oscillation output signals to the first load 3 and second load 2 of the two systems.
A switch 4 switches between low gain and high gain operation. However, since the local oscillation output amplification circuit of the above-mentioned conventional communication equipment has two systems of output amplification circuits with the same configuration, it has the disadvantage that the number of parts is large and the circuit is complicated.

FIG. 3 shows a local oscillation output amplifier circuit whose circuit configuration is simplified using a switching diode D20.

The second one is supplied with a high level local oscillator output signal.
In the output amplification circuit of the load 2, when the switch 4 is connected to the a contact, the supply power VCC voltage is supplied to the amplification transistor Q20, and the amplification transistor Q20 operates at a high gain with the same configuration as in FIG.

On the other hand, the first load 3 to which a low-level local oscillation output signal is supplied is supplied with the output signal of the local oscillation circuit 1 via a switching diode D20. When the switching device 4 is connected to the B contact, the switching diode D20 is turned ON by applying the supply power VCC voltage in the forward direction, and when the switching device 4 is connected to the A contact, the switching diode D20 is turned ON.
It becomes OFF.

With the power supply switched in this way, low level and high level local oscillation output signals are supplied to the first load 3 and the second load 2.

However, the local oscillation output amplification circuit (Fig. 3) of the conventional communication equipment described above, for example,
is the reception mixer circuit of the receiving section, when an excessive received signal is received, the isolation between the first load 3 and the local oscillation circuit 1 is low, so that the oscillation frequency of the local oscillation circuit 1 increases There was a drawback that errors were caused by the influence.

This idea was made in view of the above points, and its purpose is to eliminate the drawbacks of the conventional example, reduce the number of parts and simplify it, and achieve high isolation with local oscillation circuits etc. The present invention provides a local oscillation output amplification circuit.

(c) Means for solving the problem The local oscillation output amplification circuit for communication equipment of this invention consists of an output amplification circuit that has two output systems, a local oscillation circuit for transmitting and a local oscillation circuit for reception of the communication equipment, and an output amplification circuit for these two systems. In a local oscillation output amplification circuit for communication equipment, which is equipped with a switch for switching the power supply supplied to the output amplification circuit, a first one to which a low-level local oscillation output signal is supplied;
A second load to which a high-level local oscillation output signal is supplied is connected to the collector of the output amplification transistor Q1 via the coupling capacitor C2, and the fixed contact is connected to the power supply circuit. and a switching device in which one movable contact is connected to the coupling capacitor C3 via a resistor R3, and the other movable contact is connected to the collector of the output amplification transistor Q1 and the bias circuit via an inductance L1. This is what I did.

(d) Effect A local oscillation output amplifier circuit having two loads, a first load and a second load, switches the power supply supplied to the output amplifier circuit, and further switches the power supply supplied to the first load and the second load. It is constructed by providing a switching diode between the loads.

The local oscillation output signal is applied to the amplification transistor Q1, but at this time, when the switch 4 is on the a contact side, the supply power VCC is applied to the collector of the amplification transistor Q1 via the inductance L1,
Further, since a reverse bias voltage is applied to the switching diode D, it is turned off and the first load is disconnected.
Here, the bias voltage and output impedance of Q1 are set so that a high-level local oscillation output signal required by the second load can be obtained.

Next, when switching switch 4 is switched to the b contact side, the supply power is
VCC is applied via resistor R3 and diode D to the collector of amplification transistor Q1. At this time, the forward voltage is applied to the diode D, which turns it on and connects the first load to the collector of Q1. Also, the resistance R
3 becomes a load for Q1 and is applied in parallel to the inductance L1 to lower the load impedance of Q1. Furthermore, it becomes a series resistance from the power supply VCC to lower the collector voltage and bias voltage of Q1, lowering the gain of the amplification transistor Q1, and The low level local oscillator output signal required by the load is provided via coupling capacitor C3.

In this way, with one system of local oscillation output amplifier circuit,
An oscillation output signal of an appropriate level can be switched and supplied to the first load and the second load.

(e) Embodiment An embodiment of the local oscillation output amplification circuit for communication equipment according to this invention will be described based on FIG. 1.

FIG. 1 is a circuit diagram of a local oscillation output amplification circuit of a transceiver, in which a local oscillation output signal from a local oscillation circuit 1 is applied to an amplification transistor Q1 via a coupling capacitor C1. A second load 2 is connected to the collector of Q1 via a coupling capacitor C2. Furthermore, the first load 3 is a coupling capacitor C
3 and the second load 2 via a diode D. Further, an inductance L1 is connected as a load impedance of the collector. Resistors R1 and R2 are base bias resistors, R4
and C4 are decoupling circuits for the power supply line.

Power is supplied via a switch 4, the fixed contact of which is connected to the supply voltage VCC, and the movable contact a connected to the bias resistor R1 and the decoupling circuit resistor R.
4, the movable contact b is connected to the anode of the diode D via the resistor R3, and the amplifying transistor Q
Operate 1.

Here, the first load 3 is a receiving mixer circuit of a communication device to which a relatively low level local oscillation output signal is supplied, and the second load 2 is a transmitting mixer circuit to which a relatively high level local oscillation output signal is supplied. It is an amplifier circuit of trust.

The values of base bias resistors R1 and R2 and collector load inductance L1 are determined so that a high level output signal for transmission can be obtained when the amplifying transistor Q1 circuit is on the a-contact side of the switch 4. At this time, the supply power VCC is applied to the collector of Q1 via R4 and L1, and a reverse voltage is applied to the diode D, turning the diode D off and disconnecting the first load. That is, the local oscillation output amplifier circuit supplies a high level output signal to the second load.

Next, when the movable contact of the switch 4 is on the B contact side, the power supply VCC is connected to the resistor R3 and the diode D.
It is added to the amplification transistor Q1 via. At this time, the forward voltage is applied to the diode D, which turns it on, so that the first load 3 is connected to the collector of the amplification transistor Q1. At the same time, resistor R3 is added in parallel to L1 as the collector load of Q1, lowering the collector impedance of Q1, and the series resistance of R3 enters the power supply line to lower the collector supply voltage of Q1, and the base bias voltage also lowers the collector current. Since the direction changes, the gain of the amplification transistor Q1 also decreases. That is, by appropriately selecting the value of resistor R3, and by adjusting the ratio of R1 and R2 while keeping the ratio constant, the output of amplifying transistor Q1 can be adjusted to an appropriate level for the receiving mixer circuit. can be selected. Note that the value of the decoupling resistor R4 may be made sufficiently smaller than that of R3, or the voltage drop may be taken into account in advance.

In this way, by using one system of amplifying transistors Q1, the local oscillation output signal can be switched and supplied to the second load 2 at a high level and to the first load 3 at a low level.

(F) Effect of the invention The local oscillation output amplification circuit for communication equipment according to this invention is a single amplification transistor circuit as described above, and is capable of supplying a local oscillation output signal at an appropriate level to the first load and the second load. Therefore, the local oscillation output amplification circuit can be simply configured and the number of parts can be reduced.

Furthermore, current consumption during reception can be reduced, resulting in power savings. Furthermore, high isolation is provided between the local oscillation circuit and the first and second loads,
Another advantage is that the local oscillation circuit is not adversely affected by the load and stable operation can be obtained.

Furthermore, it has excellent features such as a simple structure, and can be constructed at low cost, making it easy to implement.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a local oscillation output amplification circuit for communication equipment according to this invention. Second
3 and 3 show a conventional example, FIG. 2 is a circuit diagram composed of two systems of output amplifier circuits, and FIG. 3 is a circuit diagram using switching diodes. Explanation of main symbols, 1...Local oscillation circuit, 2...
second load, 3...first load, 4...switcher,
Q1...Amplification transistor, D...Switching diode, L1...Inductance, R3...Resistance.

Claims (1)

[Claims for Utility Model Registration] An output amplifying circuit having two output systems, a local oscillation circuit for transmitting and a receiving local oscillation circuit for communication equipment, and a switch for switching the power supply supplied to these two output amplifying circuits. In the local oscillation output amplification circuit of communication equipment, the first
A second load to which a high-level local oscillation output signal is supplied is connected to the collector of the output amplification transistor Q1 via the coupling capacitor C2, and the fixed contact is connected to the power supply circuit. and a switching device in which one movable contact is connected to the coupling capacitor C3 via a resistor R3, and the other movable contact is connected to the collector of the output amplification transistor Q1 and the bias circuit via an inductance L1. A local oscillation output amplification circuit for communication equipment, characterized in that: