JPS596016Y2 - Band switching circuit - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a band switching circuit for a tuning device.

In tuning circuits, various circuits for switching tuning coils according to bands are known.

In these circuits, the diode connected to the tuning coil is opened and closed by the band, so voltage is not constantly connected to the tuning coil through such a diode.

Therefore, bias voltage supply circuits for transistors such as tuned amplifiers coupled to these tuned circuits are provided separately from voltage supply circuits for opening and closing the diodes, and their voltage sources are also provided separately. Therefore, the structure is complicated,
The price was also expensive.

The present invention focuses on this point, and in a tuned amplifier etc., the operating voltage is supplied to the amplification element from one voltage source, and
It is an object of the present invention to provide a band switching device that can also supply an operating voltage to a band switching diode.

Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a high frequency section of a two-band radio showing one embodiment of the present invention.

In the figure, a high-band tuning coil 2 and a cathode of a switching diode 4 are connected to the output terminal of an amplification element 1 of a high-frequency amplification section A, and a low-band tuning coil 3 and a cathode of a switching diode 4 are connected to the other end of the coil 2. The cathode of switching diode 5 is connected.

A tuning diode 7 connected to the output terminal of the amplifying element 1 via a capacitor 6 forms a tuning circuit together with the coils 2 and 3.

The coil 3 has a bypass capacitor 8 and a resistor 9, and
A bypass capacitor 10 is connected to the anode of the diode 5.

Coil 11 is a choke coil.

The power supply 12 supplies voltage to the inverters 13 and 14 and is connected to the input terminal of the inverter 13 via a resistor 15.

Note that a switch 16 is connected between the input terminal of the inverter 13 and the ground.

To explain the operation of the above embodiment, first, when the switch 16 is closed during low band reception, the inverter 1
The input terminal of the inverter 3 is grounded through the switch 16 and has a zero potential, so the output terminal of the inverter 13 has a high potential and the output terminal of the inverter 14 has a low potential.

When the input terminal of the inverter 14 becomes a high potential, the anode of the diode 4 connected to it becomes a high potential, while the cathode is grounded via the coils 2, 3 and the resistor 9, so the diode 4 becomes conductive. do.

Further, when the output terminal of the inverter 14 becomes a low potential, the anode of the diode 5 connected thereto becomes a low potential, so the diode 5 is cut off.

Therefore, in this case, both the coil 2 and the coil 3 function as tuning coils, and the operating voltage is supplied to the output terminal of the amplifying element 1 through the diode 4.

Next, when the switch 16 is opened during high band reception, the input terminal of the inverter 13 becomes a high potential, its output terminal becomes a low potential, and the output terminal of the inverter 14 becomes a high potential.

When the output terminal of the inverter 14 becomes a high potential, the anode of the diode 5 connected thereto becomes a high potential;
Since its cathode is grounded via coil 3 and resistor 9, diode 5 is conductive.

Also, since the input terminal of the inverter 14 is at a low potential, the anode of the diode 4 connected thereto is at a low potential.
Diode 4 is cut off.

Therefore, in this case, the coil 3 is short-circuited at high frequency by the diode 5 and the capacitor 10, so only the coil 2 acts as a tuning coil, and voltage is supplied to the output terminal of the amplifying element 1 through the diode 5 and the coil 2. .

In the embodiment, only an amplifier circuit has been described, but it goes without saying that the present invention can also be implemented in an oscillation circuit or the like.

In addition, a variable capacitor for tracking adjustment is connected in parallel and series to diode 4. Tracking during high band reception is performed by the variable capacitor connected in parallel, and tracking during low band reception is performed by connecting the variable capacitor in series. Since the tracking adjustment circuit can be adjusted using a variable capacitor, the tracking adjustment circuit can also have a simple structure.

As described above, according to the present invention, it is possible to carry out a band switching operation and supply an operating voltage to the active elements with just one power supply, and therefore the practical effects thereof are great.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a high frequency section of a two-band radio showing an embodiment of the present invention. A... High frequency amplification section, 1... Amplifying element, 2, 3... Coil, 4, 5... Diode, 12... Power supply, 14... Inverter, 16... Switch.

Claims (1)

[Scope of utility model registration request] an active element such as an amplification or oscillation circuit, a first coil connected in direct current to an electrode of the active element, a second coil connected in series to the first coil, and the first coil. a first diode connected to a connection between the first coil and the electrode and a variable capacitor for tracking adjustment; and a second diode connected to a connection between the first coil and the second coil. , a power source, an inverter, and a switch, the input terminal of the inverter is connected to the first diode, the output terminal of the inverter is connected to the second diode, or the input terminal of the inverter is connected to the second diode,
By connecting the output terminal of the inverter to the first diode and operating the switch, the input signal of the inverter is inverted to conduct or cut off the first diode and the second diode, and the active element is connected to the first diode. A band switching circuit characterized in that an operating voltage is supplied through a first diode during low band reception and through a second diode during high band reception.