JP2002340947A - Mixer distortion measurement method and mixer distortion analysis method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform analysis as to at which part of a mixer mutual modulation distortion occurs by isolating and measuring the mutual modulation distortion for every element which constitutes the mixer. SOLUTION: By simultaneously inputting both an RF signal of a frequency RF1 (=LO+IF-Df) larger than the frequency of an LO signal and an RF signal of a frequency RF3 (=LO-IF-Df=RF1-2IF) smaller than the frequency of the LO signal to an RF terminal, the mutual modulation distortion ((frequencies IM31 (=2×IF1-IF2=IF1-2Df) and IM3u (=2×IF2-IF1=IF2+2Df)) are measured which occurs to IF signals (frequencies IF1 (=RF1-LO=IF-Df) and IF2 (=LO-RF3=IF+Df=IF1+2Df)) outputted from an IF terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency circuit and an IC.
Alternatively, the present invention relates to a method for measuring and analyzing intermodulation distortion for evaluating a mixer circuit provided in a module.

[0002]

2. Description of the Related Art In recent years, with the spread of portable telephones, the importance of mobile communication and radio frequency (Radio Frequency: hereinafter referred to as RF) circuits used for the same has been increasing.
Since the mixer used in the RF circuit plays an important role of frequency conversion, it is no exaggeration to say that the basic characteristics of the mixer affect the performance of the RF circuit and, consequently, the performance of the radio. One of the most important RF characteristics of this mixer is Inter Modulation D (Inter Modulation D).
istortion), especially third-order intermodulation distortion (hereinafter referred to as IM3), but the measurement and analysis of IM3 is very complicated.

Hereinafter, a conventional IM3 measuring method performed for a down mixer will be described with reference to the drawings.

FIG. 1 shows a circuit structure of a general down mixer divided into basic components.

[0005] As shown in FIG.
Is a terminal RFin to which an RF signal is input, and a local oscillation (L
ocal Oscillation (hereinafter referred to as LO), a terminal LOin to which a signal is input, an RF amplifier 101 that amplifies an RF signal, and a frequency of each signal, which is obtained by nonlinearizing the RF signal and the LO signal amplified by the RF amplifier 101. Frequency (Intermediate Frequency)
: Hereinafter, referred to as IF)
And an IF amplifier 103 for amplifying the IF signal, and a terminal IFout from which the IF signal amplified by the IF amplifier 103 is output.

FIG. 2 is a spectrum showing the operation of the down mixer in the conventional IM3 measuring method. In addition, in this specification, the spectrum means a graph in which the horizontal axis indicates frequency and the vertical axis indicates power.

As shown in FIG. 2, in the conventional IM3 measuring method, first, terminals RFin and RF2 (RF2> RF1 and RF2-RF1) are placed close to each other.
1 = 2Df) are input. In addition, the terminals LOin are connected to the frequencies RF1 and RF2.
An LO signal having a lower frequency LO is input.
As a result, the frequency I1
An IF signal of F1 (= RF1-LO) is output from a terminal IFout, and an I signal of frequency IF2 (= RF2-LO = IF1 + 2Df) is output from an RF signal of frequency RF2.
The F signal is output from the terminal IFout. At this time, due to the non-linearity of each element (RF amplifier section 101, mixer section 102, IF amplifier section 103), IM
As a result of the three signal components, I at the frequencies IF1 and IF2
For the F signal, the frequency IM31 (= 2 × IF1-IF2)
= IF1-2Df) and IM3u (= 2 × IF2-IF)
1 = IF2 + 2Df) IM3 signal is generated. Since Df is smaller than IF1 or IF2, frequencies IM31 and IM3u can be measured in the same IF band as frequencies IF1 and IF2.

[0008]

By the way, in the RF amplifier section 101, as shown in FIG.
And the frequency RFIM31 (=
2 × RF1-RF2 = RF1-2Df) and RFIM3
IM3 of u (= 2 × RF2-RF1 = RF2 + 2Df)
A signal component is generated. Then, in the mixer section 102, the IM3 signal component of the frequency RFIM31 has a frequency (R
FIM31-LO), and the IM3 signal component of the frequency RFIM3u is converted to the frequency (RF
IM3u-LO). Here, RFIM31-LO = (RF1-LO) -2Df =
IF1-2Df = IM31, RFIM3u-LO
= (RF2-LO) + 2Df = IF2 + 2Df = IM3
u. Therefore, the IM3 of the IF signal finally output from the terminal IFout, that is, the frequencies IM31 and IM31
3u IM3 signal is generated by the RF amplifier 101
It is the sum of the M3 signal component, the IM3 signal component generated by the mixer unit 102, and the IM3 signal component generated by the IF amplifier unit 103.

[0009] On the other hand, with the recent miniaturization of electronic devices, the downmixer 100 includes various elements (the RF amplifier unit 10).
1, a mixer unit 102 and an IF amplifier unit 103) often have a module configuration integrally formed. In this case, a test terminal is provided in the module to provide an IM3 signal of each element. It is difficult to measure the components.

That is, in the conventional IM3 measuring method, since the IM3 cannot be separately measured for each element constituting the mixer, it is not possible to analyze in which part of the mixer the IM3 is generated. is there. This problem causes a new problem that the mixer cannot be inspected to identify the source of IM3 or the mixer cannot be adjusted to reduce IM3.

In view of the above, the present invention makes it possible to separate and measure intermodulation distortion for each element constituting a mixer, thereby analyzing which part of the mixer is causing intermodulation distortion. The purpose is to be able to.

[0012]

In order to achieve the above object, a method for measuring distortion of a mixer according to the present invention comprises a first terminal to which a high-frequency signal is input and a second terminal to which a local oscillation signal is input. , A first amplifying unit for amplifying the high-frequency signal, and a mixer unit for converting the high-frequency signal and the local oscillation signal amplified by the first amplifying unit into an intermediate frequency signal having a frequency difference between the signals as a frequency. And a second amplifier for amplifying the intermediate frequency signal, and a third terminal for outputting the intermediate frequency signal amplified by the second amplifier, for measuring an intermodulation distortion generated in a down mixer. And a first high-frequency signal having a frequency higher than the frequency of the local oscillation signal and a second high-frequency signal having a frequency lower than the frequency of the local oscillation signal are connected to a first terminal. Same as By entering into, and a step of measuring the intermodulation distortion occurring to the intermediate frequency signal output from the third terminal.

According to the mixer distortion measuring method of the present invention,
A first having a frequency greater than the frequency of the local signal
And a second high-frequency signal having a frequency lower than the frequency of the local oscillation signal are simultaneously input to the first terminal to measure the intermodulation distortion, so that the measurement is performed in the frequency band of the intermediate frequency signal. The intermodulation distortion is only the intermodulation distortion generated in the second amplifier. That is, the intermodulation distortion generated in the second amplification unit can be measured separately from the intermodulation distortion generated in the first amplification unit and the mixer unit. For this reason, it is possible to easily analyze in which part of the mixer the intermodulation distortion is occurring.
Inspection of the amplifying unit, that is, the IF amplifier unit, is defective, or adjustment of the IF amplifier unit for reducing intermodulation distortion can be easily performed.

[0014] A distortion analysis method for a mixer according to the present invention includes a first terminal to which a high-frequency signal is input, a second terminal to which a local oscillation signal is input, and a first amplifying unit for amplifying the high-frequency signal. A mixer for converting the high-frequency signal and the local transmission signal amplified by the first amplifier to an intermediate frequency signal having a frequency difference between the signals as a frequency, a second amplifier for amplifying the intermediate frequency signal, The method is based on a mixer distortion analysis method for analyzing intermodulation distortion generated in a down-mixer having a third terminal to which an intermediate frequency signal amplified by the second amplifying unit is output. By simultaneously inputting two high-frequency signals having different frequencies from each other to the first terminal,
Of the intermediate frequency signal output from the terminal
Measuring a first high frequency signal having a frequency higher than the frequency of the local oscillation signal and a second high frequency signal having a frequency lower than the frequency of the local oscillation signal at a first terminal. Measuring the second intermodulation distortion generated for the intermediate frequency signal output from the third terminal by simultaneously inputting the first intermodulation distortion and the first intermodulation distortion. And a step of performing

According to the distortion analysis method for a mixer of the present invention,
Since two high-frequency signals having frequencies higher than the frequency of the local oscillation signal and different from each other are simultaneously input to the first terminal and the first intermodulation distortion is measured, the entire downmixer is used as the first intermodulation distortion. Can be measured. A first high-frequency signal having a frequency higher than the frequency of the local oscillation signal;
A second signal having a frequency lower than the frequency of the local oscillation signal;
The second intermodulation distortion is measured by simultaneously inputting the high frequency signal to the first terminal and measuring the second intermodulation distortion. Therefore, it is necessary to measure only the intermodulation distortion generated in the second amplifier as the second intermodulation distortion. it can. For this reason, the first intermodulation distortion and the second
By comparing the intermodulation distortion component with the intermodulation distortion component generated by the second amplification unit and the intermodulation distortion component generated by the first amplification unit and the mixer unit, the intermodulation distortion component can be separately confirmed. It is possible to reliably analyze which part of the mixer is causing the intermodulation distortion.

In the method for analyzing distortion of a mixer according to the present invention,
It is preferable that the method further includes a step of inspecting or adjusting the second amplifying unit based on a comparison result between the first intermodulation distortion and the second intermodulation distortion.

In this way, the degree of the intermodulation distortion generated in the second amplifying section, that is, the IF amplifier section with respect to the intermodulation distortion generated in the entire down mixer can be determined.
For example, it is possible to reliably test whether the IF amplifier unit is defective or to adjust the IF amplifier unit to reduce intermodulation distortion.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a method for measuring distortion of a mixer according to a first embodiment of the present invention will be described with reference to an example in which IM3 generated in a down mixer shown in FIG. 1 is measured. This will be described with reference to FIG.

In the first embodiment, the down-mixer 100 includes each element (the RF amplifier 101, the mixer 1
02, IF amplifier section 103) has a module configuration integrally formed.

FIG. 3 is a spectrum showing an operation of the down mixer in the mixer distortion measuring method according to the first embodiment.

As shown in FIG. 3, in the mixer distortion measuring method according to the first embodiment, first, a frequency RF1 (= LO + IF-D) higher than the frequency LO of the LO signal.
f) When the RF signal is input to the terminal RFin,
The frequency RF3 (= LO−) smaller than the frequency LO of the signal
IF-Df = RF1-2IF) RF signal to terminal RFi
Enter n. Further, an LO signal having a frequency LO is input to a terminal LOin. Thereby, R of frequency RF1 is obtained.
The frequency IF1 (= RF1-LO = IF-
Df) is output from the terminal IFout, and the frequency IF2 (=
An IF signal of LO-RF3 = IF + Df = IF1 + 2Df) is output from the terminal IFout. At this time, the frequency IF
1 and the IF signal of IF2, the frequency IM31 (= 2
× IF1-IF2 = IF1-2Df) and IM3u (=
An IM3 signal component of 2 × IF2-IF1 = IF2 + 2Df) is generated. Since Df (predetermined frequency difference) is smaller than IF1 or IF2, the frequency IM31
And IM3u can be measured in the same IF band as the frequencies IF1 and IF2.

Next, IM generated by the RF amplifier 101
The three signal components will be described.

FIG. 4 shows IM3 signal components generated by the RF amplifier unit 101 with respect to the RF signals of the frequencies RF1 and RF3.

As shown in FIG. 4, in the first embodiment, the frequency RFIM31 (= 2RF3-RF1 = RF3-2I) is applied to the RF signals of the frequencies RF1 and RF3.
F) and RFIM3u (= 2RF1-RF3 = RF1 +
2IF) IM3 signal component is generated in the RF amplifier unit 101. Then, in the mixer section 102, the frequency RFI
The M3 IM3 signal component has a frequency (RFIM31-L
O) into the IM3 signal component and the frequency RFI
The IM3 signal component of M3u has a frequency (RFIM3u-L
O) is converted to an IM3 signal component. Where RFIM
31-LO = LO-IF-Df-2IF-LO = -3I
F-Df, RFIM3u-LO = LO + IF-D
f + 2IF-LO = 3IF-Df. Therefore, IM3 of the IF signal finally output from the terminal IFout,
That is, the IM3 signals of the frequencies IM31 and IM3u include:
The frequencies ((RFIM31-LO) and (RFIM3u-L) generated by the RF amplifier 101 and the mixer 102
O)) does not include the IM3 signal component. In other words, the IM3 signals of the frequencies IM31 and IM3u output from the terminal IFout are only the IM3 signal components generated by the IF amplifier 103.

That is, according to the first embodiment, the IF
The IM3 signal component generated by the amplifier 103 can be measured separately from the IM3 signal component generated by the RF amplifier 101 and the mixer 102. For this reason, since it is possible to easily analyze in which part of the down mixer 100 the IM3 is generated, for example, it is possible to check whether the IF amplifier unit 103 is defective or to use the IF amplifier unit 103 for reducing the intermodulation distortion. Adjustment can be easily performed.

In the first embodiment, IM3 (third-order intermodulation distortion) was measured as intermodulation distortion, but the intermodulation distortion to be measured is not particularly limited.
For example, measurement of other odd-order intermodulation distortion such as fifth-order intermodulation distortion or seventh-order intermodulation distortion can be similarly performed.

Although the first embodiment is directed to the down mixer 100 having a module configuration in which each element is integrally formed, the configuration of the down mixer 100 is not particularly limited.

(Second Embodiment) A mixer distortion analysis method according to a second embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 shows a configuration of a mixer distortion measuring apparatus for performing the mixer distortion analysis method according to the second embodiment on the down mixer (down mixer 100) shown in FIG.

As shown in FIG. 5, in order to input two kinds of RF signals of different frequencies to the terminal RFin, the terminal RFin
In the first RF signal source 501 and the second RF signal source 5
02 is connected. Also, the LO signal is supplied to the terminal LOi
n, the LO signal source 50 is connected to the terminal LOin.
3 are connected. Further, a spectrum analyzer 504 is connected to the terminal IFout in order to measure an IF signal output from the terminal IFout.

Note that, in the second embodiment, the down mixer 100 includes each element (the RF amplifier section 101, the mixer section 1).
02, IF amplifier section 103) has a module configuration integrally formed.

FIG. 6 is a flowchart of a mixer distortion analysis method according to the second embodiment.

First, in step 1, the down mixer 1 is used by using a conventional IM3 measuring method as shown in FIG.
The IM3 generated in the entire 00 is measured. Specifically, the frequency RF1 is supplied from the first RF signal source 501 to the terminal RFin.
Of the second RF signal source 50
From terminal 2 to terminal RFin, frequency R close to frequency RF1
R of F2 (RF2> RF1 and RF2-RF1 = 2Df)
Input the F signal. Further, the terminal L is supplied from the LO signal source 503 to the terminal L.
An LO signal having a frequency LO lower than the frequency RF1 is input to Oin. The frequency IF1 output from the terminal IFout with respect to the RF signal of the frequency RF1
(= RF1−LO) IF signal and frequency RF2 RF signal
Frequency IF output from terminal IFout for signal
2 (= RF2-LO) IF signal is measured by the spectrum analyzer 504, and the frequency IM31 (=
2IF1-IF2 = IF1-2Df) and IM3u (=
The IM3 signal of 2IF2-IF1 = IF2 + 2Df) is measured by the spectrum analyzer 504. Here, since Df (predetermined frequency difference) is smaller than IF1 or IF2, the frequencies IM31 and IM3u are set to the frequency I
It can be measured by the spectrum analyzer 504 in the same IF band as F1 and IF2. Further, as described above (see “Problems to be Solved by the Invention”), the IM3 signals of the frequencies IM31 and IM3u are composed of the IM3 signal component generated by the RF amplifier unit 101 and the IM3 signal component generated by the mixer unit 102. , And the IM3 signal component generated by the IF amplifier 103. That is, in step 1, IM generated in the entire down mixer 100
3 (hereinafter referred to as first intermodulation distortion) as frequencies IM31 and IM3u (hereinafter IM3al and IM3al).
au) is obtained.

Next, in step 2, using the IM3 measuring method according to the first embodiment as shown in FIG.
The IM3 generated by the IF amplifier unit 103 is measured. Specifically, L from the first RF signal source 501 to the terminal RFin
The frequency RF1 (RF1) that is higher than the frequency LO of the O signal
= LO + IF-Df)
A frequency RF3 (= LO−IF−) smaller than the frequency LO of the LO signal is supplied from the second RF signal source 502 to the terminal RFin.
Df = RF1-2IF). Also,
An LO signal having a frequency LO is input from a LO signal source 503 to a terminal LOin. The frequency IF1 output from the terminal IFout with respect to the RF signal of the frequency RF1
(= RF1-LO = IF-Df) and a frequency IF2 output from the terminal IFout with respect to the RF signal of the frequency RF3 (= LO-RF3 = IF + Df = IF1)
+ 2Df) IF signal with a spectrum analyzer 50
4 and the I of the frequencies IF1 and IF2.
The frequency IM31 (= 2IF1-
IF2 = IF1-2Df) and IM3u (= 2IF2-
The IM3 signal of IF1 = IF2 + 2Df) is measured by the spectrum analyzer 504. Since Df is smaller than IF1 or IF2, the frequency IM31
And IM3u can be measured by spectrum analyzer 504 in the same IF band as frequencies IF1 and IF2. On the other hand, as described in the first embodiment, when the RF signals of the frequencies RF1 and RF3 are input to the terminal RFin, the IM3 signals of the frequencies IM31 and IM3u include only the IM3 signal component generated by the IF amplifier 103. Become. In other words, the RF amplifier unit 101 and the mixer unit 10 provide the IM3 signals of the frequencies IM31 and IM3u.
2 does not include the IM3 signal component generated. Therefore, in step 2, IM3 signals of frequencies IM31 and IM3u (hereinafter, referred to as IM3bl and IM3bu) are obtained as IM3 (hereinafter, referred to as second intermodulation distortion) generated in the IF amplifier unit 103.

Next, in step 3, the first intermodulation distortion obtained in step 1 is compared with the second intermodulation distortion obtained in step 2.

As described above, according to the second embodiment, the IM3 generated in the entire downmixer 100 is measured as the first intermodulation distortion, and the IF amplifier 1
After measuring IM3 generated in 03 as the second intermodulation distortion, the first intermodulation distortion is compared with the second intermodulation distortion. For this reason, the I
Since M3 and IM3 generated in the RF amplifier unit 101 and the mixer unit 102 can be separately confirmed, it is possible to reliably analyze in which part of the down mixer 100 the IM3 is generated.

In the second embodiment, the IF amplifier 103 may be inspected or adjusted based on the result of comparison between the first intermodulation distortion and the second intermodulation distortion.
By doing so, the IM3 generated in the IF amplifier unit 103 with respect to the IM3 generated in the entire down mixer 100
Therefore, for example, it is possible to reliably test whether the IF amplifier unit 103 is defective or to adjust the IF amplifier unit 103 to reduce IM3.

In the second embodiment, IM3 (third-order intermodulation distortion) was measured as intermodulation distortion.
The intermodulation distortion to be measured is not particularly limited. For example, measurement of other odd-order intermodulation distortion such as fifth-order intermodulation distortion or seventh-order intermodulation distortion can be similarly performed.

Although the second embodiment is directed to the down mixer 100 having a module configuration in which each element is integrally formed, the configuration of the down mixer 100 is not particularly limited.

In the second embodiment, after measuring IM3 generated in the entire down mixer 100 (step 1), IM3 generated in the IF amplifier 103 is measured (step 2). , IF amplifier section 10
After measuring IM3 generated in the downmixer 3, the downmixer 100
The IM3 generated as a whole may be measured.

In the second embodiment, the RF of the frequency RF1 is applied to the terminal RFin in steps 1 and 2.
Although the signal is input, the frequency of the RF signal does not necessarily have to be the same in step 1 and step 2. However,
It is preferable that the frequency LO of the LO signal and the predetermined frequency difference Df be the same in Step 1 and Step 2.

[0042]

According to the present invention, since the intermodulation distortion measured in the frequency band of the intermediate frequency signal is only the intermodulation distortion generated in the second amplifier, the intermodulation distortion generated in the second amplifier is generated. The distortion can be measured separately from the intermodulation distortion generated in the first amplifier and the mixer. For this reason, it is possible to easily analyze in which part of the mixer the intermodulation distortion is occurring, so that, for example, the second amplifying unit, that is, the IF amplifier unit is inspected for defects or the IF for reducing the intermodulation distortion. The adjustment of the amplifier section can be easily performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit structure of a general down mixer divided into basic components.

FIG. 2 is a spectrum showing an operation of a down mixer in a conventional IM3 measurement method.

FIG. 3 is a spectrum showing an operation of the down mixer in the mixer distortion measuring method according to the first embodiment of the present invention.

FIG. 4 is a diagram showing IM3 signal components generated in an RF amplifier for RF signals of frequencies RF1 and RF3 in the mixer distortion measuring method according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a mixer distortion measuring device for performing a mixer distortion analysis method according to a second embodiment of the present invention.

FIG. 6 is a flowchart of a mixer distortion analysis method according to a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Down mixer 101 RF amplifier unit 102 Mixer unit 103 IF amplifier unit 501 First RF signal source 502 Second RF signal source 503 LO signal source 504 Spectrum analyzer RFin terminal LOin terminal IFout terminal

Claims (3)

[Claims] A first terminal to which a high-frequency signal is input;
A second terminal to which a local oscillation signal is input; a first amplification unit that amplifies the high-frequency signal; and a high-frequency signal amplified by the first amplification unit and the local oscillation signal, the frequency of each of the signals. A mixer for converting the intermediate frequency signal into an intermediate frequency signal having a frequency difference, a second amplifier for amplifying the intermediate frequency signal, and a third for outputting the intermediate frequency signal amplified by the second amplifier. And a terminal for measuring intermodulation distortion generated in a down-mixer, comprising: a first high-frequency signal having a frequency higher than a frequency of the local oscillation signal; and a local oscillation signal. And a second high-frequency signal having a frequency lower than that of the first terminal is simultaneously input to the first terminal, whereby a phase generated for the intermediate frequency signal output from the third terminal A method for measuring distortion of a mixer, comprising a step of measuring intermodulation distortion. 2. A first terminal to which a high-frequency signal is input,
A second terminal to which a local oscillation signal is input; a first amplification unit that amplifies the high-frequency signal; and a high-frequency signal amplified by the first amplification unit and the local oscillation signal, the frequency of each of the signals. A mixer for converting the intermediate frequency signal into an intermediate frequency signal having a frequency difference, a second amplifier for amplifying the intermediate frequency signal, and a third for outputting the intermediate frequency signal amplified by the second amplifier. And a method for analyzing intermodulation distortion generated in a down mixer having the following terminals: a first high frequency signal having a frequency higher than a frequency of the local oscillation signal and different from each other, Measuring a first intermodulation distortion caused on the intermediate frequency signal output from the third terminal by simultaneously inputting the signals to the terminals; By simultaneously inputting a first high-frequency signal having a frequency greater than a number and a second high-frequency signal having a frequency lower than the frequency of the local oscillation signal to the first terminal, the third terminal Measuring a second intermodulation distortion generated with respect to the intermediate frequency signal output from the first and second intermodulation distortions; and comparing the first intermodulation distortion with the second intermodulation distortion. A distortion analysis method for a mixer. 3. The method according to claim 2, further comprising a step of inspecting or adjusting the second amplifying unit based on a comparison result between the first intermodulation distortion and the second intermodulation distortion. A method for analyzing distortion of a mixer according to claim 2.