JP2001033499A - Network analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a network analyzer which switches an attenuator and preamplifier corresponding to an output power to easily and automatically measure while setting an optimum resolution bandwidth when measuring by changing power of a signal applying to a measured device in a wide range. SOLUTION: A network analyzer measuring by changing power of a signal applying to a measured device, obtains a maximum input power level from error compensation data in a through-characteristic, a switching point between an attenuator and preamplifier in an output level is determined from relation between a maximum input power level of the error compensation data in the through-characteristic and an input power. Resolution bandwidth is determined so that requested S/N ratio and sweeping time corresponding to the switching point between the attenuator and preamplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a network analyzer for measuring characteristics by changing the power of a signal applied to a device under test.

[0002]

2. Description of the Related Art First, the configuration and operation of a conventional network analyzer will be described with reference to FIGS. As shown in FIG. 5, a conventional network analyzer includes a synthesizer 10, an amplifier 11, a divider 12
, Attenuators 31, 32, and preamplifiers 41, 42
Mixers 51 and 52, A / D converters 61 and 62,
It comprises a DSP 80, a CPU 81, and a display unit 82.

[0003] The synthesizer 10 generates a sweep signal in a test frequency range.

[0004] The amplifier 11 amplifies the test frequency of the synthesizer 10 to a power level of a signal necessary for the test and outputs the signal.

The divider 12 divides the power of one signal into an output 1 and an output 2 and outputs a signal having uniform level characteristics and phase characteristics.

The attenuators 31 and 32 attenuate a desired amount of attenuation when the level of the R-input and A-input reception signals is high. However, the attenuators 31 and 32 are through when the attenuation amount is 0 dB.

The preamplifiers 41 and 42 amplify the signals with desired gains when the received signal levels of the R input and the A input are low. However, the preamplifiers 41 and 42 have a gain of 0d
In the case of B, it is through.

The mixers 51 and 52 mix an input frequency with a local signal synchronized with a test frequency of the synthesizer 10 and output an IF frequency signal.

A / D converters 61 and 62 convert an IF frequency signal into digital data.

The DSP 80 calculates data such as amplitude and phase based on a desired resolution bandwidth (RBW) from digital data of the A / D converters 61 and 62.

The CPU 81 is a processor that controls each block and stores data.

The display unit 82 displays characteristics such as amplitude and phase with respect to frequency from the obtained data.

Next, the setup of the network analyzer will be described. As shown in FIG. 5, when measuring the characteristics of the crystal unit 91, a π circuit jig 90 is used. As shown in FIG. 6, the π circuit jig 90 includes, for example,
Matching circuits for converting the impedance of the measurement system from 50Ω to the impedance of the crystal oscillator side of 12.5Ω are constituted by resistors R1, R2, R3 and resistors R4, R5, R6, respectively.

As shown in FIG. 5, the signal of output 1 is connected to the R input of the comparison input by a cable 110. However, the output 1 and the R input may be measured by inserting an attenuator having the same amount of attenuation in order to match the dynamic range between the output 2 and the A input. on the other hand,
The signal of output 2 connects the π circuit jig 90 to the A input via cables 120 and 130. The characteristics of the crystal unit 91 of the device under test inserted into the π circuit jig 90 are measured by taking the ratio A / R between the A input and the R input.

For example, as a test of the crystal unit 91, in order to test a change in the resonance frequency when the power supply voltage decreases, the drive level is measured by changing the applied power in a wide range and measuring the change in the resonance frequency. There is a dependency item.

Next, an operation example of the network analyzer in the case where measurement is performed while changing the power applied to the device under test will be described with reference to FIGS. 6 and 7. FIG. In the network analyzer shown in FIG.
The dynamic range is limited by two linear regions, the maximum input level, S / N, and the like. Therefore, at the R input and the A input of the network analyzer, when the input power is small, the gain is increased by the preamplifiers 41 and 42, and when the input power is large, the signals are attenuated by the attenuators 31 and 32 to expand the dynamic range. ing.

Next, regarding the relationship between the input power of the network analyzer and the S / N, the resolution bandwidth (RBW)
Is described with reference to the example of FIG. 7 when is set to 1 kHz (wide) or 100 Hz (narrow). For example, depending on the magnitude of the input power, the attenuators 31 and 32 and the preamplifier 4
It is assumed that the settings are switched between 1 and 42 as follows. n1 ≦ input power ≦ n3: attenuators 31 and 32 have 0 dB (through) preamplifiers 41 and 42 have 20 dB amplification n3 <input power <n5: attenuators 31 and 32 have 0 dB (through) preamplifiers 41 and 42 have 0 dB (through) n5 ≤ input power ≤ n7: attenuators 31 and 32 are 20 dB attenuation preamplifiers 41 and 42 are 0 dB (through)

In general, when measuring with a network analyzer, there is a trade-off relationship between the resolution bandwidth and the sweep time. That is, when the resolution bandwidth is narrowed and the resolution is increased, the sweep time is increased, and when the resolution bandwidth is increased and the resolution is reduced, the sweep time is shortened. Also, if the settings of the attenuator and the preamplifier are constant, the S / N is better when the input power is larger, and when the input power is the same, the S / N is smaller when the resolution bandwidth is wider than when the resolution bandwidth is wider.
N is good.

For example, in FIG. 7, the measurement conditions of the device under test in the range of input powers n1 to n7 by the network analyzer are measured with a resolution bandwidth narrower than 1 kHz and a S / N better than b. You want to. When the resolution bandwidth is 100 Hz, the S / N is equal to or more than b in the range of the input power n1 to n7, which satisfies the measurement condition, but the sweep time is long. On the other hand, with a resolution bandwidth of 1 kHz, the sweep time can be shortened, but only in the range of the input powers n2 to n3, n4 to n5, and n6 to n7 satisfies the measurement condition where the S / N is b or more.

Therefore, in order to make the sweep time as short as possible in order to shorten the measurement time of the network analyzer, it is necessary to change the setting of the resolution bandwidth to an optimum value each time according to the input power. There is. However, in order to switch between the network analyzer's attenuator and preamplifier and to set the measurement conditions such as the resolution bandwidth to the optimum conditions each time, the characteristics of the network analyzer and the attenuation of the device under test and the measurement jig are required. It was necessary to measure and understand the characteristics of the quantity in advance, and thus a lot of measurement time was required.

[0021]

As described above, when measuring the drive level dependency,
It is necessary to perform measurement while changing the output power of the network analyzer over a wide range.However, it takes time to switch between attenuators and preamplifiers and set the measurement conditions such as the resolution bandwidth optimally each time. It is necessary to measure and grasp the characteristics of the device under test and the characteristics of the attenuation amount of the device under test and the measuring jig in advance. Accordingly, the present invention has been made in view of such a problem. The purpose of the present invention is to automatically switch between an attenuator and a preamplifier when performing measurement while changing the power over a wide range, and obtain a resolution that provides an optimum sweep time. It is an object of the present invention to provide a network analyzer which can easily set a bandwidth and measure easily.

[0022]

That is, a first aspect of the present invention, which has been made to achieve the above object, is to provide a network analyzer for measuring by changing the power of a signal applied to a device under test. The maximum input power level is obtained from the correction data, and the switching point between the attenuator and the preamplifier at the output power level is determined from the relationship between the maximum input power level and the input power of the error correction data of the through characteristic. The gist is a network analyzer.

In order to achieve the above object, a second aspect of the present invention is to provide a network analyzer for measuring the power of a signal applied to a device under test by changing the power of the signal applied to the device under test. Level, and the switching point between the attenuator and the preamplifier at the output power level is determined from the relationship between the maximum input power level and the input power of the error correction data of the through characteristic, and the desired switching point is determined according to the switching point between the attenuator and the preamplifier. The resolution is determined so that the S / N and the sweep time are equal to each other, and a network analyzer is characterized.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in the following examples.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. Since the block configuration itself of the network analyzer of the present invention can be realized by the same configuration as the conventional one shown in FIG. 5, the description of the operation common to the conventional one is omitted.

Next, a setup for measurement using the network analyzer of the present invention will be described. As shown in FIG. 6, a π circuit jig 90 is used to measure the crystal unit 91 as in the related art. The circuit of the π-circuit jig 90 is also the same as the conventional one, and the description is omitted.

First, the outline of the operation of performing automatic measurement by changing the power range applied to the device under test by the network analyzer of the present invention will be described. The outline of the operation is performed in the following steps as shown in the flowchart of FIG. (1) The maximum input power level is obtained from the error correction data of the through characteristic (step 100). (2) The switching point between the attenuator and the preamplifier is determined from the relationship between the maximum input power level of the error correction data of the through characteristic and the applied power (step 200). (3) A resolution bandwidth is determined according to the switching point between the attenuator and the preamplifier so as to obtain a desired S / N and a sweep time (step 300).

Next, the details of the above steps will be described below. In the network analyzer, in order to automatically switch between the attenuators 31 and 32 and the preamplifiers 41 and 42, it is necessary to determine at which power level when the output power is changed. However, since a cable, an attenuator, a measuring jig, and the like are inserted between the output 1 and the R input and between the output 2 and the A input, how much attenuation is connected is determined. I don't know unless I measure it.

On the other hand, the network analyzer measures the device under test after normalizing or calibrating it in the measurement frequency range in order to eliminate errors between the network analyzer itself and the measurement system.

Then, in normalization or calibration, a through standard for calibration is inserted into a portion of the π circuit jig 90 where the device to be measured is inserted to acquire characteristics, and errors in the frequency characteristics of amplitude and phase are removed. There are items to do. Therefore, in the network analyzer of the present invention, correction data of the R input power characteristic of normalization or calibration and the power characteristic of the A input including the through standard are used.

As shown in FIG. 1, when it is assumed that power is directly input from the output 1 to the R input of the network analyzer and from the output 2 to the A input, ideal power characteristics are as follows:
Since there is no attenuation, the output power and the input power are in proportion to each other.

However, a connection cable 110 is provided between the output 1 and the R input, and a connection cable 120, a π circuit jig 90, and a connection cable 130 are provided between the output 2 and the A input. Therefore, the maximum value of the acquired data is used as a reference. Here, the reference to the maximum value is that the input power when the device under test is inserted should be lower than the through reference, and if the signal with the input power larger than the maximum value is input, the measurement This is because a large error may occur in the data or measurement may not be possible.

In FIG. 5, a signal of, for example, 0 dBm is measured from the output 1 and the output 2 in the frequency range from f1 to f2 by replacing the crystal unit 91 of the π circuit jig 90 with a through standard. FIG. 3 shows the results of the data characteristics of the above. However, the characteristic diagram shown in FIG. 3 is a model characteristic simplified for the sake of explanation.

For example, for 0 dBm of the output signal, the maximum value of the signal power level at the R input and the A input is obtained. As shown in the example of FIG. 3, it is assumed that the maximum values of the signal power levels at the R input and the A input according to the through standard are -0.01 dBm and -30.1 dBm, respectively.

Next, as shown in FIG. 1, from the ideal power characteristics when there is no attenuation, -0.01 dBm and -3
An R input power characteristic and an A input power characteristic at which the 0.1 dBm input power is at a low level are determined.

The attenuators 31 and 32 and the preamplifiers 41 and 42 have R input power characteristics and A input power in order to set a switching point under the following input power range conditions.
The corresponding output power range is determined from the input power characteristics. Input power ≦ n3: 0 dB for attenuators 31 and 32
(Through) Preamplifiers 41 and 42 have 20 dB amplification n3 <input power <n5: attenuators 31 and 32 have 0 dB (through) preamplifiers 41 and 42 have 0 dB (through) n5 ≦ input power: attenuators 31 and 32 have 20 dB attenuation preamplifier 41 and 42 are 0 dB (through)

In the case of (input power ≦ n3), from the R input power characteristics, when (output power ≦ p2), the attenuator 31 is 0 dB (through) and the preamplifier 41 is 20 dB.
From the A input power characteristic, (output power ≦ p
In the case of 3), the attenuator 32 performs amplification of 0 dB (through), and the preamplifier 42 performs amplification of 20 dB.

In the case of (n3 <input power <n5), from the R input power characteristic, when (p2 <output power <p4), the attenuator 31 is set to 0 dB (through), and the preamplifiers 41 and 42 are set to 0 dB (through). From the A input power characteristic, when (p3 <output power <p5), the attenuator 32 is 0 dB (through) and the preamplifier 42 is 0 dB.
(Through).

In the case of (n5 ≦ input power), from the R input power characteristic, when (p4 ≦ output power), the attenuator 31 is 20 dB and the preamplifier 41 is 0 dB (through).
From the A input power characteristic, when (p5 ≦ output power), the attenuator 32 is set to 20 dB (through) and the preamplifier 42 is set to 0 dB (through).

According to the above relationship, when the output power is changed from p1 to p6, the attenuators 31 and 32 and the preamplifiers 41 and 42 are switched and set automatically.

Next, a method of setting the resolution bandwidth from the input power ranges n1 to n7 will be described with reference to FIG. However, as shown in FIG. 1, the input power ranges n1 to n7 are converted into output power using the A input power characteristic data having the larger attenuation, and the resolution bandwidth is automatically set based on the converted output power. For example, n input powers n3 and n5 correspond to output powers p3 and p5, respectively.

As described in the prior art, when measuring with a network analyzer, there is a trade-off relationship between the resolution bandwidth and the sweep time. That is, when the resolution bandwidth is narrowed and the resolution is increased, the sweep time is increased, and when the resolution bandwidth is increased and the resolution is reduced, the sweep time is shortened. Also, if the settings of the attenuator and the preamplifier are constant, the larger the input power, the better the S / N than when the input power is small, and if the input power is the same,
S / N is better when the resolution bandwidth is narrower than when it is wide.

Hereinafter, the input power shown in FIG. 4 is converted from the A input power characteristic data to the output power and set based on the output power. In the range of input powers n3 to n1, at n3 where the input power is large, the widest resolution at which the desired resolution can be obtained is set to 1 kHz, for example, and the desired S / S is reduced when the input power is lowered.
Before N becomes lower than b, the resolution bandwidth is switched to 700 Hz, which is narrower than 1 kHz, to improve the S / N, and the resolution bandwidth is switched in the same manner. / N is the resolution bandwidth that can be obtained. Further, the resolution bandwidth is similarly obtained in the input power ranges n5 to n3 and the input power ranges n7 to n5.

According to the above-described method, an error including a jig of a measurement system can be removed from the characteristics based on the reference of the through of the network analyzer, and the attenuator, the preamplifier, and the resolution bandwidth can be automatically set based on the output power.

[0045]

The present invention is embodied in the form described above and has the following effects. That is,
Normally, the error of the measurement system is corrected using the through reference, which is performed before the measurement of the network analyzer.However, the data is diverted to obtain the measurement conditions, so it is necessary to separately acquire the data for determining the measurement conditions. The attenuator and the preamplifier can be automatically switched from the output power, and the automatic measurement can be easily performed with the optimum resolution bandwidth.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for determining a relationship between input power and output power from input power characteristics of the present invention.

FIG. 2 is a flowchart of an outline operation of the network analyzer of the present invention.

FIG. 3 is a diagram of a through characteristic.

FIG. 4 is an explanatory diagram of a resolution bandwidth of the network analyzer of the present invention.

FIG. 5 is a block diagram of a network analyzer.

FIG. 6 is a circuit diagram of a π circuit jig.

FIG. 7 is a characteristic diagram of input power and S / N.

[Explanation of symbols]

 Reference Signs List 10 synthesizer 11 amplifier 12 divider 31, 32 attenuator 41, 42 preamplifier 51, 52 mixer 61, 62 A / D converter 80 DSP 81 CPU 82 display unit 90 π circuit jig 91 crystal oscillator

Claims (2)

[Claims] 1. A network analyzer for measuring by changing the power of a signal applied to a device under test, obtaining a maximum input power level from error correction data of a through characteristic, and obtaining a maximum input power level of the error correction data of the through characteristic. A network analyzer characterized in that the switching point between the attenuator and the preamplifier at the output power level is determined from the relationship between the level and the input power. 2. A network analyzer for measuring by changing the power of a signal applied to a device under test, obtaining a maximum input power level from error correction data of a through characteristic, and obtaining a maximum input power level of the error correction data of the through characteristic. The switching point between the attenuator and the preamplifier at the output power level is determined from the relationship between the level and the input power, and the resolution bandwidth is determined according to the switching point between the attenuator and the preamplifier so that the desired S / N and sweep time are obtained. And a network analyzer.