JPH06104650A - Frequency converter - Google Patents

Abstract

PURPOSE:To eliminate spurious radiation due to a pulse modulated local signal by distributing an RF signal into two signals whose polarity is opposite to each other, distributing a local signal into two in-phase signals, implementing frequency conversion with two mixers, inverting one IF signal and synthesizing the powers. CONSTITUTION:Suppose that two signals whose frequency difference is equal to a frequency of an IF signal 3 are generated from a local oscillator 4, then the two signals are distributed respectively into two at a power distributer 10, inputted to 1st and 2nd mixers 6, 7, in which the signals are mixed, then a pseudo IF signal having a frequency component being a difference of the frequency of the two signals is outputted from the two mixers 6, 7. The pseudo IF signals are in phase and inputted to a 2nd 180 deg. hybrid 9, in which the power is synthesized after the one signal is inverted. Thus, the pseudo IF signals caused when no RF signal is inputted are subject to power synthesis at the same amplitude in an opposite phase and cancelled together.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency converter used in a pulse radar receiver.

[0002]

2. Description of the Related Art Generally, a pulse radar receiver has an RF
(Radio Frequency) signal to IF (In
The operation of frequency conversion into a terminating frequency signal is required. FIG. 3 shows a conventional device that performs the operation. In FIG. 3, 1 is an RF signal, 2 is a local signal, 3 is an IF signal, 4 is a local oscillator, and 5 is a mixer.

Next, the operation of the conventional device will be described.
To the mixer 5, the RF signal 1 and the local signal 2 generated from the local oscillator 4 are output. The mixer 5 produces an IF signal 3 having a frequency component that is the difference between the frequency of the RF signal 1 and the frequency of the local signal 2.

[0004]

In the radar receiver, the frequency conversion is performed as described above, but the local signal may be pulse-modulated for transmission blanking. Therefore, the spectrum distribution of the local signal is spread. Depending on the pulse modulation repetition frequency, the local signal includes two signals having a frequency difference corresponding to the frequency of the IF signal. This is shown in FIG. Even if the RF signal is not input, the pseudo IF signal is output from the mixer due to the mixing of these two signals included in the local signal, resulting in spurious.

The present invention has been made to solve the above problems, and an object thereof is to eliminate spurious due to a pulse-modulated local signal.

[0006]

A frequency converter according to the present invention distributes an RF signal into two signals having opposite phases and a local signal into two signals having the same phase, and performs frequency conversion by two mixers respectively. The power of one of the IF signals is reversed and then the power is combined.

The frequency converter according to the present invention is
The RF signal is divided into two signals having the same phase, and the local signal is divided into two signals having opposite phases, frequency conversion is performed by two mixers, respectively, and one IF signal is made opposite phase, and then power combining is performed.

[0008]

In the frequency converter according to the present invention, the RF signal is distributed by the 180-degree hybrid into two signals having mutually opposite phases, and the local signal is distributed by the power distributor into two signals having the same phase. Then, frequency conversion is performed using two mixers, respectively, and one of the IF signals is inverted in phase, and then power synthesis is performed. As a result, the output signals of the two mixers are
When RF signals are input, power synthesis is performed with the same amplitude and phase, and when RF signals are not input, power synthesis is performed with the same amplitude and opposite phase. Therefore, eliminate pseudo IF signals generated when RF signals are not input. You can

The frequency converter according to the present invention is
The RF signal is divided into two signals in phase by the power divider, and the local signal is divided into two signals in opposite phase by the 180-degree hybrid. Then, frequency conversion is performed using two mixers, respectively, and one of the IF signals is inverted in phase, and then power synthesis is performed. As a result, the output signals of the two mixers are power-synthesized with the same amplitude and the same phase when the RF signal is input, and with the same amplitude and the opposite phase when the RF signal is not input, so that the RF signal is not input. It is possible to eliminate the pseudo IF signal that occurs in some cases.

[0010]

【Example】

Example 1. An embodiment of the present invention will be described below. Figure 1
In the above, 1 to 4 are exactly the same as the above-mentioned conventional device. 6 is a first mixer, 7 is a second mixer, 8 is a first 180-degree hybrid, 9 is a second 180-degree hybrid, and 10 is a power distributor.

Next, the operation of the frequency converter will be described. First, FIG. 5 shows the operation when the RF signal is input. In FIG. 5, the amplitude (effective value) of the RF signal 1 and the angular frequency are R and ω _R , the amplitude (effective value) of the local signal 2 and the angular frequency are L and ω _L , and the IF signal 3 is shown.
The amplitude (effective value) and angular frequency of are set as I and ω _I , respectively. RF signal _{1 (√2Rexp (jω R t)} ) reversed-phase two signals to each other by a first 180 degree hybrid _{8 (Rexp (jω R t)} , Rexp {j (ω R t-18
0 °)}), and the first mixer 6 and the second mixer 6, respectively.
Is input to the mixer 7. The local oscillator 4 from the resulting local signal _{2 (√2Lexp (jω L t)} ) , the phase of the two signals by the power divider 10 (Lexp (jω _L
t)) and input to the first mixer 6 and the second mixer 7, respectively. First mixer 6 and second mixer 7
Then, each is subjected to frequency conversion, and an IF signal 3 having a frequency component of a difference between the frequency of the RF signal 1 and the frequency of the local signal 2 is generated. At this time, since the RF signals input to the first mixer 6 and the second mixer 7 have opposite phases to each other, the outputs of the first mixer 6 and the second mixer 7 also have opposite phases to each other. 2 signal (Iexp (jω _I t),
_{Iexp {j (ω I t-} 180 °)}) is the second 180
Is input to the hybrid 9 once. Second hybrid 9
Then, since power synthesis is performed after one of the signals is reversed in phase, the output signals of the first mixer 6 and the second mixer 7 are
Eventually, power is combined with the same amplitude and phase, and the IF signal (√2Ie) is output from the second 180-degree hybrid 9.
xp (jω _I t)) is output. Normally, the above-mentioned operation is performed. Next, a case where the RF signal 1 is not input and only the pulse-modulated local signal 2 is input will be described with reference to FIG. In FIG. 6, the angular frequencies of the RF signal 1, the local signal 2, and the IF signal 3 are ω _R , ω _L , and ω _I , respectively, and the angular frequencies ω _R and ω _L components included in the pulse-modulated local signal 2 are set. The amplitude (effective value) of the signal is set to L ₁ and L ₂ , and the amplitude of the angular frequency ω _I component of the two mixer outputs is set to L ₃ . In this case, the spectrum distribution of the local signal 2 is spread as shown in FIG. 4 as described above. Therefore, the frequency difference from the local oscillator 4 is now equal to the frequency of the IF signal 3 2
Signal (√2L ₁ exp (jω _R t), √2L ₂ exp
It is considered that (jω _L t)) has occurred. After these two signals are divided into two by the power divider 10, respectively,
Mixer 6, is input result to be mixed in the second mixer 7, these two signals pseudo IF signal having a frequency component of the difference between the frequency of the _{(L 3 exp (jω I t} )) are two mixers Is output. These pseudo IF signals are input to the second 180 degree hybrid 9 in phase,
There, one signal is reversed in phase and then power combining is performed.
Eventually, these pseudo IF signals are power-combined with the same amplitude and opposite phase, and cancel each other out.

Example 2. Another embodiment of the present invention will be described below. In FIG. 2, 1 to 4, 6 to 10 are exactly the same as those of the device of the first embodiment.

Next, the operation of the frequency converter will be described. First, FIG. 7 shows the operation when the RF signal is input. In FIG. 7, the amplitude (effective value) of the RF signal 1 and the angular frequency are R and ω _R , the amplitude (effective value) of the local signal 2 and the angular frequency are L and ω _L , respectively, and the IF signal 3 is shown.
The amplitude (effective value) and angular frequency of are set as I and ω _I , respectively. The RF signal 1 (√2Rexp (jω _R t)) is
The power distributor 10 causes two signals in phase (Rexp (jω _R
t) and are input to the first mixer 6 and the second mixer 7, respectively. Further, the local signal 2 (√2Lexp (jω _L t)) generated from the local oscillator 4 is the first 18
The 0 degree hybrid 8 allows two signals (Le
xp (jω _L t), Lexp {j (ω _L t−180
)))) And input to the first mixer 6 and the second mixer 7, respectively. In the first mixer 6 and the second mixer 7, frequency conversion is performed, and a signal having a frequency component of a difference between the frequency of the RF signal 1 and the frequency of the local signal 2 is generated. At this time, since the local signals input to the first mixer 6 and the second mixer 7 have opposite phases to each other, the outputs of the first mixer 6 and the second mixer 7 also have opposite phases to each other. 2 signal _{(Iexp (jω I t),} I
_{exp {j (ω I t +} 180 °)}) is input to the second 180 ° hybrid 9. In the second 180-degree hybrid 9, power synthesis is performed after one of the signals is reversed in phase, so that the output signals of the first mixer 6 and the second mixer 7 are eventually power synthesis with the same amplitude and the same phase. Therefore, the IF signal (√
2Iexp (jω _I t)) is output. Normally, the above-mentioned operation is performed. Next, a case where the RF signal 1 is not input and only the pulse-modulated local signal 2 is input will be described with reference to FIG. In FIG. 8, RF
The angular frequencies of the signal 1, the local signal 2, and the IF signal 3 are set to ω _R , ω _L , and ω _I , respectively, and the amplitudes of the signals of the angular frequencies ω _R component and ω _L component included in the pulse-modulated local signal 2 ( The effective values are L ₁ and L ₂ , respectively, and the amplitude of the angular frequency ω _I component of the two mixer outputs is L ₃ . In this case, the spectrum distribution of the local signal 2 is spread as shown in FIG. 4 as described above. Therefore, two signals a frequency difference from now the local oscillator 4 is equal to the frequency of the IF signal _{3 (√2L 1 exp (jω R} t), √2L 2 e
xp (jω _L t)) is generated. These two signals are respectively divided into two by the first 180-degree hybrid 8 and then input to the first mixer 6 and the second mixer 7 to be mixed. As a result, the frequency component of the frequency difference between these two signals is obtained. Pseudo IF signal (L ₃ exp with
(Jω _I t)) is output from the two mixers. These pseudo IF signals are input to the second 180-degree hybrid 9 in the same phase, where one of the signals is made to be in the opposite phase and then power combining is performed. After all, these pseudo IF signals are
The power is combined with the same amplitude and opposite phase, and they cancel each other out.

[0014]

As described above, the frequency converter according to the present invention divides the RF signal and the local signal into two,
The frequency is converted by two mixers, and then the power is combined by a 180-degree hybrid bridge to generate an IF signal. One of the RF signal and the local signal is two opposite-phase signals and the other is the same-phase signal. It is distributed to two signals.
With such a configuration, when an RF signal is input, 2
It is possible to combine the outputs of the two mixers with the same amplitude and the same phase, and when the RF signal is not input, combine the outputs of the two mixers with the same amplitude and the opposite phase. As a result, the effect of canceling out the pseudo IF signals generated when the RF signals are not input can be expected.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a frequency converter according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a frequency converter according to another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional frequency converter.

FIG. 4 is a diagram showing a spectrum distribution of a pulse-modulated local signal.

FIG. 5 is a diagram showing an operation of the frequency converter according to the embodiment of the present invention. (When RF signal is input)

FIG. 6 is a diagram showing an operation of the frequency converter according to the embodiment of the present invention. (Without RF signal input)

FIG. 7 is a diagram showing an operation of a frequency converter according to another embodiment of the present invention. (When RF signal is input)

FIG. 8 is a diagram showing an operation of a frequency converter according to another embodiment of the present invention. (Without RF signal input)

[Explanation of symbols]

 1 RF Signal 2 Local Signal 3 IF Signal 4 Local Oscillator 5 Mixer 6 First Mixer 7 Second Mixer 8 First 180 Degree Hybrid 9 Second 180 Degree Hybrid 10 Power Divider

Claims (2)

[Claims] 1. An RF which is an input signal to a frequency converter.
A first 180-degree hybrid that distributes a (Radio Frequency) signal into two signals having opposite phases, a local oscillator that generates a local signal, a power distributor that distributes the local signal to two signals having the same phase, and a first A 180-degree hybrid and a first mixer and a second mixer that perform frequency conversion by using the output of the power divider as an input signal, and the outputs of the first mixer and the second mixer are input to input one of the signals. After phase conversion of 180 degrees, power synthesis and IF
A frequency converter configured with a second 180-degree hybrid that outputs an (Intermediate Frequency) signal. 2. A power distributor that distributes an RF signal, which is an input signal to the frequency converter, into two signals in phase, a local oscillator that generates a local signal, and a local signal into two signals that are opposite in phase to each other. A first 180-degree hybrid, a power divider, and a first mixer that performs frequency conversion using the output of the first 180-degree hybrid as an input signal, a second mixer, the first mixer, and the second mixer. A frequency converter configured with a second 180-degree hybrid that outputs the IF signal by inputting the output of the mixer of FIG.