JPH03219711A - Image cancel mixer - Google Patents

Abstract

PURPOSE:To improve the image suppressing ratio by connecting a variable attenuator to one output of a couple of mixers mixing two signals whose phases differ by 90 deg. and each input signal to obtain an intermediate frequency signal and connecting a variable attenuator and a variable phase shifter to other output. CONSTITUTION:A local oscillation signal is inputted to a local frequency signal terminal 1 and distributed into two signals with different phase by 90 deg. with a high frequency band 90 deg. phase difference two-distributer 7. The signals are inputted mixers 5, 6 respectively and a high frequency signal is inputted to a terminal 2 and the local oscillation signal and the high frequency signal are mixed in the mixers 5, 6, and intermediate frequency signals with different phase of 90 deg. are outputted from IF output terminals 3, 4. The output from the terminal 3 is fed to an IF 90 deg. phase difference input synthesizer 8 via a variable attenuator 10 and the output of the terminal 4 is fed thereto via a variable attenuator 11 and a variable phase shifter. The amplitude and the phase difference of both the IF signals are always kept constant by adjusting the attenuators 10, 11 and the variable phase shifter 12. Thus, an image signal is ideally cancelled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mixer used in a microwave band, and particularly to a mixer that cancels images.

[Conventional technology]

Conventionally, this type of image canceling mixer used in the microwave band has two mixers 5 and 6 as shown in FIG.
, high frequency band 90° phase difference 2 splitter 7, and intermediate frequency band 9
It is composed of a two-input synthesizer 8 with a 0° phase difference. That is,
A local oscillation frequency signal inputted from the local oscillation frequency signal terminal 1 is divided by a high frequency band 90° phase difference two divider 7, and each is inputted to a mixer 5.6. Further, the high frequency signal inputted from the high frequency signal terminal 2 is inputted to the mixers 5 and 6, respectively. Then, by mixing these signals in mixers 5 and 6, intermediate frequency signals are taken out to intermediate frequency signal terminals 3 and 4, respectively. Furthermore, this intermediate frequency signal is transferred to an intermediate frequency band 90'.
After inputting each to the pass port or isolation port of the phase difference 2-input synthesizer 8 and combining them,
Either the -90° output terminal 13 or the 0° output terminal 14 is terminated, and the image-cancelled signal is output from the other.

Note that the reference numeral 9 indicates a terminator.

[Problem to be solved by the invention]

In the conventional image canceling mixer described above, as the frequency of the high frequency signal input to the high frequency signal terminal 2 increases, the difference in amplitude between the intermediate frequency output signals output from the two mixers 5 and 6 increases. This tends to occur, and the phase difference between the two tends to be deviated from 90°. Therefore, there is a problem that the image side signal is not completely canceled in the intermediate frequency band 90° phase difference two-input synthesizer 8, and the image suppression ratio deteriorates. In order to improve this, it is necessary to adjust each mixer 5.6 according to the frequency of the input high-frequency signal, resulting in a problem that a large amount of adjustment time is required.

An object of the present invention is to provide an image cancellation mixer that can reliably suppress images.

[Means to solve the problem]

The image canceling mixer of the present invention includes a 90' phase difference two-way divider that divides an input signal into two signals with a 90° phase difference, and a signal output from the 90° phase difference two-way divider and other signals. a pair of mixers that obtain intermediate frequency signals by mixing input signals, a two-input synthesizer with a 90° phase difference that synthesizes and outputs the intermediate frequency signals from these mixers, and the output side of one of the mixers. a variable attenuator connected to the
It includes a variable attenuator and a variable phase shifter connected to the output side of the other mixer.

[Effect]

According to the present invention, by adjusting the variable attenuator and the variable phase shifter, the intermediate frequency signals output from both mixers can be adjusted to the same amplitude level and a predetermined phase difference. By passing the signal through a two-input synthesizer with a 90° phase difference, images can be effectively canceled.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention. In the figure, a local oscillation signal is input to the local oscillation frequency signal terminal 1, and a high frequency band 90° phase difference 2 splitter 7 generates 2 signals with a 90° phase difference.
divided into two signals. These two signals are each input to a mixer 5.6. 9 is a terminator. Further, a high frequency signal is input to the high frequency signal terminal 2, and the mixer 5,
6 are input in phase with each other. and mixer 5.6
By mixing these local frequency signals and high frequency signals, intermediate frequency signals having a phase difference of 90° are outputted to intermediate frequency output terminals 3.4, respectively.

A variable attenuator 10 is connected to one of the intermediate frequency output terminals 3 and 4, here output terminal 3, and a variable attenuator 11 and a variable phase shifter 12 are connected to the other output terminal 4. By adjusting these variable attenuators 10°11, the amplitude levels of each intermediate frequency signal can be made equal.

Further, by adjusting the variable phase shifter 12, the phase of the other intermediate frequency signal can be adjusted to make the phase difference with the one intermediate frequency signal 90''.

These variable attenuators 10 and 11 and variable phase shifter 1
2, the intermediate frequency signals having the same amplitude level and a 90° phase shift are input to the intermediate frequency band 90° phase difference 2-input synthesizer 8.
is input to the passage port or isolation boat, and is synthesized here and then output to the 90'' output terminal 13 or O0 output terminal 14 of the intermediate frequency band 90° phase difference 2-input synthesizer 8.
output from either one. At this time, intermediate frequency band 9
In the 0° phase difference 2-input synthesizer 8, the −90° output terminal 13
, 0° output terminal 14 is terminated.

Therefore, in this mixer, by adjusting the variable attenuator 10°11 and the variable phase shifter 12, it is possible to always keep the amplitude level and phase difference of the rain intermediate frequency signal constant. Even when the frequency is varied, it is possible to ideally cancel the signal on the opposite side of the high-frequency signal that is separated by an intermediate frequency from the local frequency signal, that is, the image signal, improving the image suppression ratio and suppressing the image even at high frequencies. A ratio of 20 dB or more can be achieved.

Furthermore, since the adjustment of the image ratio can be controlled by the variable attenuator 10.degree. 11 and the variable phase shifter 12, adjustment of each mixer 5.6 itself is not necessary, making it possible to shorten the adjustment time.

Note that the local oscillator signal and the high frequency signal may be configured to be input from mutually opposite terminals.

〔Effect of the invention〕

As explained above, the present invention connects a variable attenuator to one output side of a pair of mixers that mix one signal with a phase difference of 90° and another input signal to obtain an intermediate frequency signal. Since a variable attenuator and a variable phase shifter are connected to the other output side, by adjusting these variable attenuators and variable phase shifters, the intermediate frequency signals output from both mixers can be made to have the same amplitude level. and can be adjusted to a predetermined phase difference.

This makes it possible to reliably remove images in the 90° phase difference two-input combiner and improve the image suppression ratio. Moreover, this eliminates the need to adjust each individual mixer, thereby shortening the adjustment time.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional image cancellation mixer. 1...Local frequency signal terminal, 2...High frequency signal terminal,
3.4...Intermediate frequency signal terminal, 5,6...Mixer,
7... High frequency band 90° phase difference 2 distributor, 8... Intermediate frequency band 90° phase difference input combiner, 9... Terminator, 10
．． 11... Variable attenuator, 12... Variable phase shifter, 13
...-90° output terminal, 14...0° output terminal.

Claims (1)

[Claims] 1. A 90° phase difference two-way splitter that divides one input signal into two signals with a 90° phase difference, and mixes the signals output from this 90° phase difference two-way splitter with other input signals, respectively. a pair of mixers for obtaining an intermediate frequency signal; and 90 for synthesizing and outputting the intermediate frequency signals from these mixers.
° In an image canceling mixer equipped with a phase difference two-input synthesizer, a variable attenuator is connected to the output side of one of the mixers, and a variable attenuator and a variable phase shifter are connected to the output side of the other mixer. An image canceling mixer characterized in that the intermediate frequency signals from both mixers can be adjusted to the same amplitude level and a predetermined phase difference.