JP2578381Y2 - Signal output switching circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output switching circuit of a signal power supply having a wide frequency band and a wide output level range for measuring characteristics of a transmission network.

[0002]

2. Description of the Related Art Measurement of a transmission network requires a signal power supply circuit capable of supplying signal power for measurement while continuously changing an output level over a wide frequency range.
One example of a conventional signal power supply circuit is shown in FIG.
A wide-frequency, high-output signal source 1 capable of generating signal power by continuously changing the amplitude in a frequency range of 1 Hz to 1 GHz and an output level range of -10 dBm to +20 dBm.
0, an output buffer 20, a load resistance 3 of about 50 ohms, changeover switches 4 and 5 comprising high-frequency relays,
It comprises a direct circuit 6 having an attenuation of 0 dBm, an attenuator 7 having an attenuation of mdBm, and an output terminal 13.
The signal power of the signal source 10 does not attenuate the output of the signal source 10 through the direct circuit 6 when a high level output is required, and the attenuator 7 when a low level output is required. In general, the output of the signal source 10 is attenuated by mdBm via the output terminal 13 and output from the output terminal 13.

[0003]

The conventional signal power supply circuit switches between high-level output and low-level output by one.
Although the attenuator is inserted and removed over a wide range of 1 Hz to 1 GHz by a set of changeover switches, the output level cannot be frequently and continuously changed because the life of the high-frequency relay constituting the changeover switch is short. Disadvantages.

There are various types of semiconductor switches having a longer service life than high-frequency switches as the changeover switches. All of the semiconductor switches have a high output of +20 dBm or more and can cope with high accuracy in a wide frequency range of 1 Hz to 1 GHz. Therefore, when measuring, it was necessary to replace the signal power supply created for each of several frequency bands.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a long-life signal output switching circuit capable of continuously changing the amplitude of signal power in a high output level and a wide frequency band with high accuracy.

[0006]

SUMMARY OF THE INVENTION A signal output switching circuit according to the present invention comprises a first direct circuit which can output power of a signal source in a high frequency band to an output terminal without attenuating the power, and a signal source in the high frequency band. To provide a predetermined amount of attenuation to the power of
And a high-frequency switch for switching the connection between the signal source and the first through circuit or the first attenuator.
, A second direct circuit that can output the power of the signal source in the low frequency band to the output terminal without attenuating the power, and a second circuit that applies a predetermined amount of attenuation to the power of the signal source in the low frequency band. An attenuator, a signal source and a second direct circuit or second
And a second attenuator comprising an FET switch for switching connection with the attenuator.

[0007]

When the frequency band of the signal source is a high frequency band, the first direct circuit and the first attenuator are switched by the high frequency switch according to the required high and low output levels,
In the case where the frequency band of the signal source is a low frequency band, the second frequency is set by the FET switch according to the required high / low output level.
And the second attenuator is switched.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a main part of an embodiment of a signal output switching circuit according to the present invention. In this embodiment, the output level is -10 dBm to +20 dBm, and the frequency is 1 Hz to 1 GH.
a signal source 10 capable of generating a signal power in the range of z, a first output buffer 20, a first attenuator 11 for a high frequency band of about 1 MHz to about 1 GHz, and a low frequency of about 1 Hz to about 1 MHz. It comprises a second attenuation section 12 for the band and an output terminal 13. The first damping unit 11
A load resistor 30 of 50 ohms, capacitors 80 and 81 for high frequency passage, a direct circuit 60 with 0 dBm attenuation,
An attenuator 70 having a selected fixed attenuation amount mdBm;
The high-frequency switches 40 and 41 are composed of diodes, and the second attenuator 12 has a load resistance 31 of 50 ohms.
A first resistor 71 having a resistance value of R1 ohm and a resistance value of R2
Ohm second resistor 72 and second output buffer 21
And three J-FET switches 42, 43, 44.

The two resistors 71 and 72 are connected in series to the first
Connected between the output side of the output buffer 20 and the ground to form an attenuator of mdBm in a low frequency band. The two resistance values R1 and R2 have an effect on a load whose sum is 50 ohms. As small as possible, it is 1 kΩ or more and 5 kΩ or less, and m = −20 log (R1 /
(R1 + R2)).

Next, the operation of this embodiment will be described.

When outputting signal power in a high frequency band of 1 MHz or more, the J-FET 4 of the second attenuator 12
2, 43 and 44 are all turned off, and the high frequency switch 4
If 0 and 41 are turned on to the direct circuit 60 side, the signal source 10
Is output from the output terminal 13 as it is, and the high-frequency switches 40 and 41 are connected to the attenuator 70.
When turned on, the output terminal 13 outputs an output signal of (−10−m) dBm to (+ 20−m) dBm in which the output of the signal source 10 is attenuated by mdBm.

When outputting signal power in a low frequency band of 1 MHz or less, one of the high-frequency switches 40 and 41, for example, the switch 40 is placed on the direct circuit 60 side, and the other switch, for example, is placed on the attenuator 70 side. After turning on the first attenuator 11 and turning on the J-FET switch 44 on the output side of the second attenuator 12, the first attenuator 11 is turned off.
J-FET switch 4 connected to the input side of the resistor 71
2 is turned on and the J-FET switch 43 connected between the two resistors 71 and 72 is turned off, the output -10 to +20 dBm of the signal source 10 is output from the output terminal 13 as it is, and the J-FET switch Turn off 42 and J-FE
When the T switch 43 is turned on, the output of the signal source 10 becomes md
Bm is attenuated and the output terminal 13 outputs (−10−m) to (+
20-m) The signal power of dBm is output.

In this way, in the high frequency band of 1 MHz or more and the low frequency band of less than 1 MHz, the output terminal 13 outputs a signal whose level is mdBm lower than the lowest output level of the signal source 10 to the highest output level of the signal source 10, ie, , Can output signal power whose output range is wider than the signal source 10 by mdBm.

Further, as shown in FIG. 2, in the present invention, each of the first and second attenuating sections is constituted by connecting n of the respective attenuating sections of the embodiment of FIG. 1 in series. It is also possible.

[0016]

According to the signal output switching circuit of the present invention, the attenuator includes a first attenuator in a high frequency band and a second attenuator in a low frequency band.
The first attenuator is divided into an attenuator and a high-frequency switch, and the second attenuator is an FET switch.
By switching the insertion / removal of the attenuator, the useful life of the changeover switch is extended, and there is an effect that the signal power in a wide frequency range can be continuously and accurately supplied from a low output level to a maximum output level and supplied.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a main part of an embodiment of a signal output switching circuit of the present invention.

FIG. 2 is a circuit diagram of a modification of the embodiment of FIG. 1 according to the present invention;

FIG. 3 is a circuit diagram of a conventional signal output switching circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Signal source 11 1st attenuation part 12 2nd attenuation part 13 Output terminal 20,21 Output buffer 4,5,40,41 High frequency changeover switch 42,43,44 J-FET changeover switch 6,60,60 'Direct circuit 7, 70, 70 ', 71, 71', 72, 72 'Attenuator 80, 80', 81, 81 'Capacitor

Claims (1)

(57) [Scope of request for utility model registration] A signal output switching circuit capable of supplying signal power in a wide frequency range from a low frequency band to a UHF band while continuously changing the amplitude from a low level to a high level. A first attenuator having a first attenuator, a first direct circuit having no attenuation, and a high-frequency switch capable of switching connection between the signal power supply and the first attenuator or the direct circuit. A second attenuator having a fixed amount of attenuation at a low frequency, a second direct circuit having no attenuation, and an F that can switch the connection between the signal power supply and the second attenuator or the direct circuit.
And a second attenuator comprising an ET switch.