JPH05223870A - Automatic measuring device for characteristics of wide band frequency converter - Google Patents

Abstract

PURPOSE:To measure the characteristics of a wide band frequency converter efficiently by automating the measuring processes. CONSTITUTION:An RF signal power level sensor 11 is connected with the RF signal input terminal 1a of a frequency converter to be measured 1 while an LO signal power level sensor 12 is connected with its LO signal input terminal 1b. The output voltages of the two sensors are fed back to an RF and an LO signal generator 2, 3, respectively, and the power levels at the abovementioned two input terminals 1a, 1b are maintained at respective specified values in the specified frequency range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a characteristic measuring device for a wide band frequency converter.

[0002]

2. Description of the Related Art A frequency converter basically has two input terminals (hereinafter, RF and LO signal input terminals) and one output terminal (hereinafter, IF signal output terminal). And LO signal frequency difference component is output as an IF signal. Typical measurement items representing the characteristics of such a frequency converter are: (1) conversion loss at fixed IF frequency (2) conversion loss at fixed LO frequency (3) conversion suppression characteristic (4) spurious characteristics Is mentioned.

The conversion losses (1) and (2) generally mean the difference between the RF signal input power and the IF signal output power when the LO signal power is constant. That is, the RF signal input power is +5 dBm and the IF output signal power is 5 dBm.
In the case of, the conversion loss is 10 dB. There are two frequency dependences of the conversion loss, and (1) is the case where the RF frequency and the LO frequency are swept simultaneously so that the IF frequency becomes constant, and the LO frequency is made constant and the RF frequency is swept.
It is (2) when the F frequency is changed.

The conversion suppression characteristic of (3) means that the relationship between the conversion loss characteristic and the input power cannot maintain the linearity and starts to decrease.

The spurs of (4) are various unnecessary frequency components appearing at the IF signal output terminal, that is, feedthrough (leakage of input signal) of RF and LO signals, 2
The second and third high frequencies, and the sum and difference frequency components of integer multiples of the respective frequencies.

For such a measurement item, in order to accurately measure the characteristics of the frequency converter itself when the measurement frequency is high, the signals connecting the signal generators, signal detectors, and DUT are measured. It is necessary to measure the frequency characteristics of path loss of cables etc. in advance.

FIG. 2 shows a block diagram of a conventional wideband frequency converter characteristic measuring apparatus.

In FIG. 2, 1 is a frequency converter to be measured,
2 is a signal generator for RF, 3 is a signal generator for LO, 4 is I
It is an F signal detector.

In order to measure the characteristics of the frequency converter 1, the RF signal generator 2, the LO signal generator 3 and the IF signal detector 4 are connected to the frequency converter 1 by connecting cables 5, 6 respectively. , 7 to form a measurement system.

The signal generator used in the above measurement system generally has a built-in level detector for automatic level control, and this level detector has a function of converting the power at the output terminal into a voltage. is doing. The signal generator compares this voltage with the voltage corresponding to the set power level and changes the output until they match. As a result, the set power levels can be obtained at the output terminals 2a and 3a of the signal generators 2 and 3, respectively.

The connection cable 5 is the R of the RF signal generator 2.
The F signal output terminal 2a and the RF signal input end 1a of the frequency converter 1 to be measured are connected, and the connection cable 6 is the LO signal output terminal 3a of the LO signal generator 3 and the LO input of the frequency converter 1. Connect between the terminal 1b and the connection cable 7
Connects between the output terminal 1c of the frequency converter 1 and the input terminal 4a of the IF signal detector 4.

When the characteristics of the wideband frequency converter are measured by configuring the measurement system as described above, the signal transmission loss of the connection cable varies depending on the measurement frequency because the measurement frequency range is wide. Influence. Therefore,
The frequency characteristic of the signal path loss of the cable is measured in advance using a transmission loss measuring device to obtain the calibration data of the loss of each connection cable, and the measured value of the frequency converter characteristic is used as the calibration data. Correct by.

Next, the measuring method will be described by taking the frequency characteristic of the conversion loss at the fixed IF frequency (1) as an example.

The frequencies of the RF signal generator 2 and the LO signal generator 3 are set.

The loss in the connection cable is corrected so that desired input powers P _RF and P _LO are applied to the RF input terminal 1 a and the LO input terminal 1 b of the frequency converter 1 to be measured, and the RF signal is corrected. The power levels at the output terminals 2a and 3a of the generator 2 and the LO signal generator 3 are set.

Based on the above settings, the RF and LO signals are applied to the input terminals 1a and 1b of the frequency converter 1 to be measured.

I of the input terminal 4 a of the IF signal detector 4
Measure the power level of the F frequency component.

The path loss of the connection cable 7 is corrected and the power level P _IF at the IF signal output terminal 4b is obtained. The conversion loss is obtained by (P _IF −P _RF ).

Depending on the sweep frequency, is repeated.

[0020]

As described above, in order to obtain the characteristics of the conventional wide band frequency converter, a predetermined signal is input to the RF and LO input terminals of the frequency converter 1 to be measured for each measurement frequency. The output levels of the RF and LO signal generators 2 and 3 are set in consideration of the loss of the connecting cable so that the input power is applied, and the IF power at the output terminal 4b of the IF signal detector is also the loss of the connecting cable. Since it is necessary to carry out the measurement in consideration of the above, there is a drawback that a correction operation is manually performed and the measurement time is increased. In addition, there is a problem that it is difficult to control the power level with high accuracy at the signal input end of the frequency converter under test because the signal application method uses both the power level setting at the output end of the signal generator and the loss correction at the connection cable. ..

An object of the present invention is to set a power level of each input signal by a characteristic measuring system of a conventional frequency converter while correcting a path loss corresponding to two kinds of input frequencies, and to set a power level of an output signal. Also, the operation of compensating for the path loss according to the frequency is performed manually, the measurement time per frequency is long, the measurement efficiency is poor, and the high accuracy at the input end of the measured frequency converter. An object of the present invention is to provide an automatic measuring device for wideband frequency converter characteristics, which solves the drawback that various power level control is difficult.

[0022]

The present invention is directed to a wideband RF signal generating means, a wideband LO signal generating means, an IF signal detecting means, an RF signal input terminal and an LO signal input terminal of a frequency converter under test. Has signal power level detecting means for RF and LO for detecting a signal power level from each signal generating means applied thereto and outputting a voltage corresponding to the power level. The power level applied to the output voltage of each power level detecting means is fed back to the corresponding signal generating means so as to be maintained at a predetermined level set in advance over a predetermined frequency band, A signal level automatic control means for controlling the signal output level of the signal generating means, and a control section for controlling the operation of each means by a computer. Form was.

[0023]

Since the present invention is configured as described above, the path loss of the cable connecting the RF and LO signal generating means and the measured frequency converter, and the measured frequency converter and the IF are measured.
It is possible to automatically measure various characteristics of the wideband frequency converter by instructing the control section using a computer for each measurement item without considering the path loss of the cable connecting the signal detecting means. ..

[0024]

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

In FIG. 1, 1 is a frequency converter to be measured,
2 is a signal generator for RF, 3 is a signal generator for LO, 4 is I
F signal detector, 5, 6 and 7 are signal connection cables, 11 is RF signal power level detector, 12 is LO signal power level detector, 13 is RF feed bar loop,
Reference numeral 14 is an LO feedback loop, 15 is an automatic signal level control unit, 16 is a control unit, 1a and 1b are RF signals of the frequency converter 1 to be measured, LO signal input terminals, and 1c is a converter of the converter 1. IF signal output terminals 2a, 2b
Are RF signal output terminals and output level external control terminals of the RF signal generator, and 3a and 3b are LO of the LO signal generator.
Signal output terminal and output level external control terminal, 4a, 4
b is an input and output terminal of the IF signal detector.

The RF signal power level detector and the LO signal power level detector of the automatic signal level control section 15 detect the power level at the input section of the frequency converter 1, that is, 1a and 1b for each frequency, and convert it into a voltage. It has the function of converting this voltage to a signal generator,
By feeding back the output level external control terminals 2b and 3b of the RF signal generator 2 and the LO signal generator 3, it becomes possible to correct the power level at the input part of the frequency converter 1. The output level external control terminal is a terminal for feeding back an output voltage from an external signal power level detector instead of the wave detector incorporated in the signal generator described in the description of the prior art. Therefore, the signal level automatic control unit can directly control the signal level at the input unit of the frequency converter 1. Further, the signal generators 2 and 3, the IF signal detector, the signal level automatic control unit and the like can be controlled by a computer through a common interface bus.

FIG. 3 is a flow chart of the above measurement.

Since the present invention is configured as described above, it is possible to perform high-precision measurement because direct power level setting is possible without the need for correction based on the path loss calibration data as in the prior art. Furthermore, by sweeping the frequency and power level under computer control, it is not necessary to manually set the power level while making corrections, so the measurement time can be greatly shortened.

FIG. 3 is a characteristic diagram obtained by measuring the characteristics of a commercially available wide band frequency converter using the above-described embodiment of the present invention.

The characteristic diagram shown in FIG. 3 is obtained by measuring the conversion loss at a fixed IF frequency by sweeping the frequency from 2 GHz to 20 GHz. The solid line shows the case of automatic measurement, and the broken line shows the case of manual measurement by the conventional method, and almost the same results are obtained. The measurement time / measurement frequency score was 1 minute / 200 points, which made it possible to reduce the measurement time with high accuracy compared to the conventional method of 10 minutes / 10 points.

[0031]

As described in detail above, according to the wide band frequency converter characteristic automatic measuring apparatus of the present invention, it is possible to perform highly accurate measurement and greatly reduce the measurement time at the same time.
Particularly in a wideband frequency converter, there are many measurement frequency ranges and measurement points, and the larger the number of measurement items and the number of measurement items, the greater the effect of shortening the measurement time, and it is possible to make a great contribution to the improvement of measurement efficiency.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional wideband frequency converter characteristic measuring device.

FIG. 3 is a flowchart of an embodiment of the present invention.

FIG. 4 is a characteristic diagram of a wideband frequency converter measured using an example of the present invention.

[Explanation of symbols]

 1 frequency converter 2 RF signal generator 3 LO signal generator 4 IF signal detector 5 RF signal connection cable 6 LO signal connection cable 7 IF signal connection cable 11 RF signal power level detector 12 LO signal power level detector 13 RF feedback loop 14 LO feedback loop 15 Signal level automatic control unit 16 Control unit

Claims (1)

[Claims] 1. A wideband frequency converter characteristic measuring apparatus comprising: a wideband RF signal generating means, a wideband LO signal generating means, an IF signal detecting means, and an RF of a frequency converter under test.
By detecting the signal power level from each of the signal generating means applied to the signal input terminal and the LO signal input terminal,
It has RF and LO signal power level detecting means for outputting a voltage corresponding to the power level, and the power level applied to each of the input terminals is set to a predetermined level over a predetermined frequency band. So that the output voltage of each power level detecting means is fed back to the corresponding signal generating means,
A wide band frequency converter characteristic automatic measuring apparatus comprising: a signal level automatic control means for controlling a signal output level of the signal generating means; and a control section for controlling the operation of each means by a computer.