JP3116389B2 - Frequency converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency converter for converting a radio frequency to an intermediate frequency or an intermediate frequency to a radio frequency for use in a microwave communication device or the like.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional frequency converter. The frequency converter converts the frequency of the input signal input to the input terminal 1 by the frequency mixer 2 and outputs the converted signal from the output terminal 3. A switch 4 is connected to the frequency mixer 2 so that an external local signal input from a local signal input terminal 5 and a local signal from a local signal oscillator 7 are switched and input. Part of the local signal from the local signal oscillator 7 can be output from the local signal output terminal 6 to the outside. Further, the level of a part of the local signal from the local signal oscillator 7 is detected by a detector 8, and the detector output is identified by an identifier 9 to determine whether or not the level is equal to or higher than a threshold value. Then, the state of the output of the discriminator 9 and
The control circuit 1 is controlled by a control signal input to the control terminal 12.
0 controls the switch 4 and at the same time, the discriminator 9
The output state is output from the control terminal 11 to the outside.

Conventionally, this type of frequency converter has been used for cross-polarization interference cancellation (XPIC) of co-channel transmission for performing microwave communication using two orthogonal polarization planes.
In order to synchronize the frequency and the phase between the two polarized waves, the local oscillation signal is shared between the two polarized waves. Assuming that two orthogonal polarizations are V polarization and H polarization respectively, for example, the frequency converter on the V polarization side inputs the internal local oscillator output to the frequency mixer, and the frequency converter on the other H polarization side. Is used by connecting a local signal output terminal of the V-side frequency converter and a local signal input terminal of the H-side frequency converter with a cable or the like. At the same time, the control signal output of the V-side frequency converter is connected to the H-side frequency converter. By connecting to the external control signal input of
Used to input the local oscillator output. The control signal is a signal for controlling the switch to automatically use the output of the H-side local signal oscillator in both the V and H frequency converters when an abnormality occurs in the V-side local signal oscillator output. is there.

[0004]

In this conventional frequency converter, a maintenance person mistakenly disconnects a local signal input cable of a frequency converter operating on an external local signal during line operation. When the input is cut off, the local signal from the internal local signal oscillator 7 is still input to the detector 8 and the discriminator 9, and the control circuit 10 controls the switch 4 as it is. In addition, the frequency mixer 2 has a problem that the frequency conversion operation is stopped at the same time when the external local signal is cut off, and as a result, the system is disconnected. SUMMARY OF THE INVENTION It is an object of the present invention to provide a frequency converter that secures the operation of a frequency converter and prevents a line disconnection even when the input of a local signal is interrupted.

[0005]

SUMMARY OF THE INVENTION A frequency converter according to the present invention mixes an input signal with a local signal and converts the frequency, a local signal oscillator for generating a local signal, and a signal from the local signal oscillator. A switch for selecting one of a local signal and a local signal input from the outside and inputting the signal to the frequency mixer, a detector for detecting the level of the local signal input to the frequency mixer, and an output from the detector A discriminator for performing discrimination by comparing the level of a signal to be inputted with a threshold value, and switching control of a switch based on the discrimination result of the discriminator and a control signal inputted from the outside, and at the same time discriminating the discriminator A control circuit for outputting the result to the outside is provided. Moreover,
The two frequency converters when cross connected, by inputting a local signal generated by one of the local signal oscillator as other external local signal, so as to enter one of the identification result as the other control signals To the two frequency converters
Either of the local signal oscillators provided
Switching is selected simultaneously by two frequency converters .

[0006]

According to the present invention, since the switch is controlled based on the local signal input to the frequency mixer, even when the external local signal is interrupted, the switch is switched so that the local signal is constantly output. Input to the frequency mixer to ensure the operation of the frequency converter.

[0007]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a block circuit diagram of an embodiment of the frequency converter of the present invention. In the figure, an input signal input to an input terminal 1 is frequency-converted by a frequency mixer 2 and output from an output terminal 3. A switch 4 is connected to the frequency mixer 2 so that an external local signal input from a local signal input terminal 5 and a local signal from the local signal oscillator 7 are switched and input. . Part of the local signal from the local signal oscillator 7 can be output from the local signal output terminal 6 to the outside. The switch 4 is provided with a detector 8 for detecting the level of the local signal supplied to the frequency mixer 2 and discriminating from the output of the detector 8 whether or not the level of the local signal is higher than a threshold value. Connected to the discriminator 9 to be connected to the control terminal 1.
And a control circuit 10 for controlling the switch 4 in accordance with a control signal input to the control signal 2 and simultaneously outputting the state of the output of the discriminator 9 from a control terminal 11 to the outside.

According to this configuration, the control circuit 10 controls the switch 4 by identifying the level of the local signal currently selected and input to the frequency mixer 2 by the switch 4. . Therefore, when an external local signal is input to the local signal input terminal 5 and the input of the external local signal is interrupted when the frequency mixer 2 is operated with the external local signal, the detector 8 and the detector 8 are immediately turned off. The discriminator 9 detects this state, switches the switch 4 to the local signal oscillator 7 side by the control circuit 10, and the frequency conversion operation is continued by its own local signal. This makes it possible to ensure the operation of the frequency converter.

FIG. 2 is a circuit diagram showing a specific example of a case where a local oscillation signal is shared by using two frequency converters shown in FIG. The control circuit 110 of the frequency converter 100 includes:
The switch 104 is controlled so that the local oscillator 107 is selected. At this time, the output of the discriminator 109 is at the digital logic level H, and the signal level for controlling the switch 104 is also at logic H. When the frequency converter 200 of identical configuration as the frequency converter 100 connected as shown in the figure, variable frequency
Switch the output of the control signal 23, 25 and discriminator 209 are output from the exchanger 100 to the frequency converter 200 20
When the signal level for controlling the control signal L becomes L
4 is controlled to select an external local signal, that is, the local signal oscillator 107 of the frequency converter 100, and the two frequency converters 100 and 200 share a common local signal oscillator 107.
It works by. Similarly, the frequency converter 200
The control signals 24 and 26 output to the number converter 100 and the
The switch 104 is controlled by the output of the separate unit 109.

[0010] Here, for example, when the connection cable 21 is disconnected, in the conventional frequency converter, the signal corresponding to the frequency converter 200 is locally disconnected, and the main line is also disconnected due to the influence. In the present invention, in this case, the output of the
Is level H, but the output of the discriminator 209 is level L and
Thus, the control signal 26 becomes L and the control signal 24 becomes H. Ma
Since the control signal 25 is H, the control signal 23 is L and
The output for controlling the switch 104 is L, and the switch 204
Is switched to H, each of the switching units 104 and 204 is switched to a different side from the current side, and both frequency converters 100 and 2 are switched.
00 operates with the local signal oscillator 207 of the frequency converter 200 and does not affect the main line. Also, when the output level of the local oscillator 107 is lowered due to a failure when the cable is not disconnected, the control signals 25 and 26 are set to L and the control signal 24
Are H and the control signal 23 is L , so that the switches 104 and 20
4 is switched, the local signal oscillator 2 of the frequency converter 200
07 performs a common operation.

[0011]

As described above, according to the present invention, two frequency converters are connected crosswise to control a switch based on a local signal input to a frequency mixer.
The local signal of the local signal oscillator of the frequency converter
If the input cable for external local signals is disconnected or the local signal input is disconnected due to failure of the local signal oscillator, etc. The operation of the frequency converter can be secured by switching to the appropriate side, and the communication system can be maintained without affecting the main line.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of one embodiment of the present invention.

FIG. 2 is a circuit diagram of a specific configuration of the present invention.

FIG. 3 is a block circuit diagram of a conventional frequency converter.

[Explanation of symbols]

 2, 102, 202 Frequency mixer 4, 104, 204 Switcher 5, 105, 205 Local signal input terminal 6, 106, 206 Local signal output terminal 7, 107, 207 Local signal oscillator 8, 108, 208 Detector 9, 109,209 Classifier 100,200 Frequency converter

Claims (2)

(57) [Claims] 1. A frequency converter used for microwave communication, comprising: a frequency mixer for mixing an input signal with a local signal to perform frequency conversion; a local signal oscillator for generating a local signal; A switch for selecting one of a local signal and a local signal input from the outside and inputting the selected signal to the frequency mixer; a detector for detecting the level of the local signal input to the frequency mixer; A discriminator that performs discrimination by comparing the level of a signal output from a threshold with a threshold, and controls switching of the switch based on a discrimination result of the discriminator and a control signal input from the outside, and at the same time, Equipped with a control circuit that outputs the identification result of the classifier to the outside, when two frequency converters are cross-connected
The local signal generated by one local signal oscillator is
Input as an external local signal of
Input as a control signal input from outside
And a local unit provided in each of the two frequency converters.
Simultaneously use one of the signal oscillators with the two frequency converters
A frequency converter characterized in that the frequency converter is switched and selected . 2. The frequency converter according to claim 1, wherein the two frequency converters are orthogonal.
In a microwave communication system using two polarization planes
Frequency converter on one polarization side and the other
2. A frequency converter according to claim 1, wherein
Of the frequency converter.