JPH0125336Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a transmission output detection circuit in a radio device.

Conventionally, in radio equipment, in order to detect transmission output, as shown in FIG. In addition, as shown in FIG. 2, a minute capacitor 7 was directly connected to the signal line 6. Note that 8 is a receiver. In the method using the directional coupler 5 shown in FIG.
Since these devices are made by attaching elements such as capacitors and coils to a wiring board, they require a large amount of installation space and have the disadvantage of increasing costs. The method using the minute capacitor 7 shown in FIG. 2 has the disadvantage that it adversely affects the impedance of the transmission output signal line 6.

The present invention was made to improve these conventional drawbacks, and includes a means for detecting the transmission output in the tuning circuit of the high-frequency input stage of the receiver to detect leakage between the transmitter and the receiver. . With such a configuration, the transmission output can be controlled depending on the magnitude of the leakage detection signal.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. Note that the same parts as in FIGS. 1 and 2 are given the same reference numerals.

In FIG. 3, 9 is an antenna, and this antenna 9 is connected to an antenna changeover switch 10.
One contact 11 of this changeover switch 10 is LPF
(low pass filter) 2 is connected to the transmitter 1. The other contact 12 of the changeover switch 10 is coupled to an input tuning circuit 15 mainly composed of a tuning coil 13 and a variable capacitor 14, and this input tuning circuit 15 is connected to a high frequency amplifier circuit, an intermediate frequency circuit, etc. via a coupling capacitor 16. , a detection circuit, an output circuit, and the like.

A leakage signal detection line 17 is coupled to the tuning coil 13 at a point where the input impedance is lower than 50Ω tap, and this detection line 17 is connected to the transmitter 1 via a detection circuit 18 and a voltage control circuit 19. combined.

A concrete circuit of the detection circuit 18 and voltage control circuit 19 is shown in FIG. In FIG. 4, the detection circuit 18 includes transistors 20 and 21 as an amplification section, a variable resistor 22 as a gain adjustment section, a temperature compensation diode 23, a transistor 24 as a detection section, as well as resistors and capacitors. It is composed of Further, the voltage control circuit 19 is composed of two transistors 25 and 26 connected in Darlington.

Next, the operation of the circuit according to the present invention will be explained.

The antenna changeover switch 10 is connected to the contact 11 on the transmitter 1 side, and transmission is started. This transmitter 1
A part of the power inevitably leaks to the receiver 8 side. This leakage signal is received by the input tuning circuit 15 and sent to the detection circuit 18 via the detection line 17. In the detection circuit 18, transistors 20 and 21
After being amplified by the transistor 24 , the signal is detected by the transistor 24 , and its output is applied to the voltage control circuit 19 . Then,
This voltage control circuit 19 obtains an output signal corresponding to the received power, and variably controls the power supply voltage of the transmitter 1 depending on whether the received power is large or small. That is, when the received power is large, a part of the power supply voltage within the transmitter 1 is lowered to obtain a predetermined transmission output. Conversely, when the received power is small, the voltage is increased.

Note that the detection circuit 18 and the voltage control circuit 19 are connected to the fourth
It goes without saying that the circuit is not limited to the one shown in the figure and can be modified in various ways.

As mentioned above, the present invention detects the transmission output from the low impedance point of the input tuning circuit of the receiver, and controls the transmission output with this detection output. This allows the transmission output to be detected without affecting the output.

[Brief explanation of the drawing]

Figures 1 and 2 are block diagrams of conventional transmission output detection circuits, Figure 3 is a block diagram showing an embodiment of the transmission output detection circuit according to the present invention, and Figure 4 is a detection circuit and voltage control circuit. FIG. 2 is a specific electrical circuit diagram. 1... Transmitter, 2... LPF (low pass filter), 3... Reflected wave detection, 4... Traveling wave detection, 5
... Directional coupler, 6 ... Signal line, 7 ... Microcapacitance, 8 ... Receiver, 9 ... Antenna, 10 ...
...Antenna selection switch, 11, 12...Contact,
13... Tuning coil, 14... Variable capacitor, 15...
...Input tuning circuit, 16...Coupling capacitor, 17
...Detection line, 18...Detection circuit, 19...Voltage control circuit, 20, 21, 24, 25, 26...
Transistor, 22... variable resistor for gain adjustment.

Claims (1)

[Claims for Utility Model Registration] (1) In a radio device in which a transmitter and a receiver are selectively connected to an antenna using an antenna switching switch, A transmission output detection circuit comprising: a detection line; and a voltage control circuit coupled to the detection line and controlling a power supply voltage of the transmitter according to reception output power. (2) A transmission output detection circuit as set forth in claim 1 of the utility model registration claim, wherein the low input impedance point of the input tuning circuit to which the detection line is coupled is set to a point where the input impedance is 50Ω or less. (3) In the claims 1 or 2 of the utility model registration claim, the detection line is coupled to a tuning coil of an input tuning circuit, and this detection line is coupled to a voltage control circuit via a detection circuit. Output detection circuit. (4) In claim 3 of the utility model registration, the detection circuit is a transmission output detection circuit comprising an amplifier section, a gain adjustment section, and a detection section.