JPH1010167A - Spectrum analyzer for measuring s parameter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the reflection factor and the transmission factor with high accuracy using a spectrum analyzer provided with a TG (tracking generator). SOLUTION: An RF front end 51 comprising a directional coupler 52 and an input switch 53 is provided at the I/O section of a conventional spectrum analyzer provided with a TG. Output frequency from the TG section 40 is introduced through the directional coupler to the output terminal 57 of a measuring unit and a reflection signal is introduced from the output terminal 57 to the input switch 53. The input switch 53 switches the input signal to the spectrum analyzer between a signal from the input terminal 58 of the measuring unit and a signal from the directional coupler 52. An operating means is provided for the analytical data processing of the spectrum analyzer and an analytical data is processed while taking account of a correction data at the RF front end 51. The processed data is delivered to a display section so that S (scattering matrix) parameters can also be displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrum analyzer with a tracking generator (hereinafter referred to as "TG") for measuring S-parameters (hereinafter referred to as "S-parameters"). About the analyzer.

[0002]

2. Description of the Related Art An S-matrix focuses on amplitude, and is mainly used to display the transfer characteristics of components in the microwave field.
The S parameter refers to each element of the [S] matrix.
The physical meaning of the S parameter is as follows.
For example, in a waveguide or the like having an N aperture, it is assumed that a wave having an amplitude value of 1 enters from the i-th aperture and all other apertures are non-reflection terminated. At this time, the reflection coefficient at the i-th opening is S
_ii , and the transmission (output) coefficient of the j-th aperture represents _Sji .

In a component such as an attenuator having two openings, a wave having an amplitude value of 1 is input from a first opening and the other second
If the aperture is a non-reflective end, S ₁₁ means the reflection coefficient,
S ₂₁ denotes a transfer coefficient to the second opening. When the second opening in the opposite to the reflection-free termination of the first opening to enter the wave amplitude values 1, S ₂₂ is the reflection coefficient at the second opening, S ₁₂ means the transfer coefficient to the first opening. Therefore, for example, when the input and output are matched, the value of S ₁₁ = S ₂₂ = 0.

A network analyzer has been conventionally used to measure these S parameters. The network analyzer is a dedicated measuring device for analyzing the transfer characteristics and the reflection characteristics of the high-frequency analog network. FIG. 2 is an explanatory diagram of measurement using a network analyzer. FIG.
2A shows a conceptual diagram of the measurement, FIG. 2B shows a method for measuring a transfer characteristic, and FIG. 2C shows a method for measuring a reflection characteristic. The concept of measurement is to analyze how a sine wave signal input to the DUT (device under test) 15 changes and appears in the DUT output.

FIG. 2A will be described. The network analyzer is a swept signal source 10 that outputs a swept sine wave.
And an analysis unit 11 for comparing a reference signal input and a response signal input
It is composed of The swept sine wave is output from the output terminal 12 and branched, one of which is input as a reference signal to a reference signal input terminal 13 of the analyzer 11, and the other is a response signal input to a response signal input terminal 14 via a DUT (DUT). Is entered as The analysis unit 11 compares and analyzes the reference signal and the response signal, and calculates and displays various transfer characteristics and reflection characteristics.

A method of measuring the transfer characteristics will be described with reference to FIG. The output signal from the output terminal 12 of the sweep signal source 10 is divided into two by the power splitter 16, one of which is supplied to the reference signal input terminal 13 of the analysis unit, the other is supplied to the DUT 15, and the output signal of the DUT 15 is supplied to the response signal input terminal 14. Give to. The analysis unit 11 compares and analyzes the input reference signal and response signal, and can obtain amplitude characteristics, phase characteristics, group delay time characteristics, and the like, in addition to S parameters S ₂₁ and S ₁₂ .

A method for measuring the reflection characteristics will be described with reference to FIG. The output signal from the output terminal 12 of the sweep signal source 10 is divided into two by the power splitter 16, and one of the two is supplied to the reference signal input terminal 13 of the analysis unit. The other is supplied to the DUT 15 via a directional coupler (reflection bridge) 17. The input signal from terminal a is b
The signal is transmitted to the terminal, and the input signal from the terminal b is transmitted to the terminal c. The other openings of the DUT 15 are non-reflectively terminated. Then, the other of the two divided measurement signals is transmitted from the terminal a to the terminal b of the directional coupler 17 and the DUT 1
5, the reflected wave from the DUT 15 is transmitted from the b terminal to the c terminal of the directional coupler 17, and is supplied to the response signal input terminal 14 of the analysis unit 11. The analysis unit 11 compares and analyzes the input reference signal and response signal, and obtains return loss, mismatch attenuation, standing wave ratio, and the like in addition to S parameters S ₁₁ and S ₂₂ .

[0008] In contrast to a network analyzer which is a dedicated measuring device for high-frequency components, there is a spectrum analyzer as a measuring device for analyzing a spectrum of a radio wave radiated from a high-frequency device. There is also a spectrum analyzer with TG (tracking generator) to which a TG is added. The TG-equipped spectrum analyzer can analyze the spectrum and also measure the amplitude characteristics of the high-frequency component.

FIG. 3 shows the configuration of a conventional spectrum analyzer with TG. First, the configuration of the spectrum analyzer will be briefly described. The external signal f7 is input terminal 21
, The signal is attenuated by an ATT (attenuator) 22 to a signal f70 of an appropriate level, and input to the first mixer 23.
A sweep signal f71 from a sweep oscillator 33 composed of a YTO (YIG oscillator) is input to the other input terminal of the first mixer 23, and the difference signal f72 is used as a first intermediate frequency as B1.
It is extracted from a PF (bandpass filter) 24.

The first intermediate frequency f72 is transmitted to the second mixer 2
5, the signal is converted to the second intermediate frequency f74, further converted to a third intermediate frequency f76 of about 3 MHz, which is easy to perform signal processing, extracted from the BPF 27, logarithmically converted by the log amplifier 28, amplified, and detected by the detector 29. Then, after being converted into a digital value by the A / D converter 30, the digital value is given to the display 31 as a Y-axis signal. The ramp voltage generator 32 generates a saw-tooth waveform voltage and supplies it to the sweep oscillator 33 and the display 31. The sweep oscillator 33 oscillates a micro frequency corresponding to the ramp voltage, and the display 31 generates an X-axis sweep signal. Used.

The output terminal 46 of the TG section 40 outputs the frequency to be analyzed by the spectrum analyzer, that is, the same frequency as the effective frequency input to the input terminal 21. The TG output frequency is generated by using the oscillation frequency of the local oscillator of the spectrum analyzer so as to match even if there is a frequency drift. The oscillator 41 oscillates the same frequency f76 as the frequency input to the log amplifier 28 and supplies the same to the fourth mixer 42. The fourth mixer 42 outputs the frequency f75 from the third local oscillator 35.
And the sum frequency f74 is given to the fifth mixer 43. The fifth mixer 43 receives the frequency f73 from the second local oscillator 34 and outputs the sum frequency f72 to the sixth mixer 4
4

The sixth mixer 44 receives and mixes the sweep frequency f71 from the sweep oscillator 33, and sums the sum frequency f70.
Is output. The output signal f70 is set to an appropriate level by the ATT 45, and outputs the same frequency f7 as the analysis frequency of the spectrum analyzer from the output terminal 46. Therefore, as shown in FIG.
6 and the input terminal 21 of the spectrum analyzer
By connecting T15, the display 31 of FIG.
The amplitude characteristics of the UT 15 are displayed.

[0013]

The TG-equipped spectrum analyzer is widely used for adjusting the frequency of a high-frequency device at an adjustment site. A network analyzer is a dedicated measuring device for high-frequency components, and originally has a different purpose of use from a spectrum analyzer. Therefore, an adjuster of a high-frequency device sometimes uses a spectrum analyzer with a TG to view not only the amplitude characteristics of the high-frequency component but also the S parameter, particularly the reflection characteristic, in order to check various characteristics of the high-frequency component to be used. In this case, the measurement had to be performed with an external directional coupler.

However, in order to improve the measurement accuracy, it is necessary to calibrate the high-frequency components used for the measurement, and since it is an external device, it is necessary to change the connection of TGout / input for each measurement, and the accuracy is improved. It was inconvenient. The present invention provides a spectrum analyzer for S-parameter measurement that can measure not only ordinary spectrum analysis but also amplitude characteristics, reflection characteristics, and transfer characteristics of high-frequency components using a spectrum analyzer with TG.

[0015]

In order to achieve the above-mentioned object, the present invention provides an RF front-end section by providing a broadband directional coupler and an input selector switch at the input / output portion of a spectrum analyzer with TG. The processing section is provided with arithmetic means and a memory for storing high-frequency characteristics of the RF front-end section measured in advance, and various characteristics are measured with high accuracy by one input switch. Here, a directional coupler refers to an input signal, for example, from terminal a to terminal b,
It leads from the terminal b to the terminal c and includes a bridge such as a reflection bridge.

For this purpose, the output signal of the TG section is connected to the terminal a of the directional coupler, and the terminal b is connected to the output terminal. The reflected wave of the DUT is guided from the terminal b to the terminal c, and the terminal c is connected to the terminal y of the input switch. The z terminal of the input switch is connected to the input terminal, and is guided from the x terminal of the common terminal to the input side of the spectrum analyzer.

In the signal processing section, a known RF signal measured in advance is used.
The high-frequency characteristics of the front-end unit are stored in a memory as correction data, and the A / D conversion of the signal under measurement is performed by adding the correction data to the analysis data, and the S parameter and other measurement result values are calculated. Display on the display.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with examples. The input / output part of the spectrum analyzer with TG, that is, the RF front end part is composed of a directional coupler and an input changeover switch. The directional coupler guides the output signal from the TG part to the output terminal of the measuring instrument, and the output terminal The reflected wave from is guided to the input changeover switch. That is,
All the output signals from the TG unit are output to the outside from the output terminals of the measuring instrument. When there is a reflected wave from the outside and the reflection coefficient is measured, the reflected wave is guided to an input changeover switch to be used as an input signal to be measured. Therefore, in order to perform the measurement with high accuracy, it is necessary to measure in advance the high-frequency characteristics of the directional coupler and the input changeover switch, that is, the RF front-end section, and use the measured data as correction data.

The input changeover switch switches the input to the spectrum analyzer from the input terminal of the measuring instrument and from the directional coupler. Input from the input terminal of the instrument, S ₂₁ foreign frequency or transmission coefficient of a normal spectrum analysis and S ₁₂
It is used at the time of measurement. Input signal from the directional coupler is used at S ₁₁ measured or S ₂₂ measurements of the reflection coefficient.

The input analyzed frequency is converted into a frequency of about 3 MHz, which is easy for signal processing by several stages of downconverters, and is converted into analysis digital data via a log amplifier, a detector, and an A / D converter. I do. The analysis data is corrected by the calculation means in consideration of the correction data stored in the memory, that is, the high-frequency characteristics of the RF front end unit,
Calculate the spectrum for spectrum analysis, and S ₁₁ , S ₂₁ ,
S ₁₂ , S ₂₂ , etc. are displayed on the display. Therefore, it is desirable that the arithmetic means is constituted by a μCPU (microcomputer). Hereinafter, embodiments will be described.

[0021]

FIG. 1 is a block diagram showing an embodiment of the present invention.
Parts corresponding to those in FIG. 3 are denoted by the same reference numerals. Figure 1 shows the DUT
It is a configuration example in the case of measuring the reflection coefficients S ₁₁ and S ₂₂ of 15. Therefore, the second opening of the DUT 15 is terminated by the non-reflection terminator, and the first opening receives the output signal from the output terminal 57 of the measuring instrument and sends the reflection signal to the output terminal 57. The case where the transfer coefficients S ₂₁ and S ₂₁ are measured will be described later.

The TG section 40 transmits the same signal as the signal to be analyzed by the spectrum analyzer, similarly to the conventional TG section. The output signal from the ATT 45 is connected to the terminal a of the directional coupler 52 of the RF front end unit 51 and sends the signal to the terminal b. The signal is guided to the output terminal 57 of the measuring instrument, and the output signal of the amplitude value 1 is sent. I do. The reflected signal from the DUT 15 is guided from the b terminal to the c terminal of the directional coupler 52, and is input to the ATT 22 of the spectrum analyzer via the y terminal and the x terminal of the input switch 53.

In the spectrum analyzer, the signal is down-converted by the first, second, and third mixers and the BP
It is extracted from F27 at a frequency of about 3 MHz. The analyzed signal is log-converted by the log amplifier 28, amplified, detected, converted to analyzed data by the A / D converter 30, and sent to the arithmetic unit 54. The arithmetic means 54 includes an RF front-end unit 51 stored in the memory 55 in advance.
Of in consideration of the correction data of the high-frequency characteristics and calculating a reflection coefficient S ₁₁ or S _22, and displays the sent to storage or display 31.

Transmission coefficient S_{twenty one}And S_{twenty one}When measuring
Although not shown, the output signal of the second aperture of the DUT 15 is
Signal to the input terminal 58, and the input switch 53
Switching to the z terminal side, that is, the input terminal 58 side of the measuring instrument
Measure. Then, the RF front-end is calculated by
Transfer coefficient S taking into account the data of the high frequency characteristics of the
_{twenty one}And S_{twenty one}Is calculated and sent to the memory or the display 31.
To display.

When measuring the amplitude characteristics of the DUT 15,
The DUT 1 is connected between the output terminal 57 and the input terminal 58 as in the prior art.
5 should be inserted and measured. The spectrum of the external frequency may also be analyzed by connecting to the input terminal 58 as in the related art.

[0026]

As described above in detail, according to the present invention, the RF front end unit 51 including the directional coupler 52 and the input changeover switch 53 is provided, and the high frequency characteristics of the RF front end unit 51 are measured in advance. The calculation means 54 stores the analysis data of the reflection coefficients S ₁₁ and S ₂₂ and the transmission coefficients S ₂₁ and S ₂₁ in the RF front-end section 51.
The calculation is performed in consideration of the high-frequency characteristics described above, and the calculation result is displayed on the display device, so that the S parameter can be measured together with the spectrum analysis.

Therefore, at the adjustment site of the high-frequency equipment, the adjuster can adjust the frequency and at the same time measure and adjust the characteristics of the high-frequency components used in the high-frequency equipment with the same measuring instrument. Is big.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a measurement example using a network analyzer. (A) is a conceptual diagram of measurement, (B) is an explanatory diagram of measurement of transfer characteristics, and (C) is an explanatory diagram of measurement of reflection characteristics.

FIG. 3 is a configuration diagram of a spectrum analyzer with TG.

[Explanation of symbols]

 Reference Signs List 10 Sweep signal source 11 Analysis unit 12 Output terminal 13 Reference signal input terminal 14 Response signal input terminal 15 DUT (DUT) 16 Power splitter 17 Directional coupler (reflection bridge) 20 Spectrum analyzer with TG 21 Input terminal 22 ATT ( Attenuator) 23 first mixer 24 BPF (bandpass filter) 25 second mixer 26 third mixer 27 BPF (bandpass filter) 28 log amplifier 29 detector 30 A / D (analog-to-digital converter) 31 display 32 lamp Voltage generator 33 Sweep oscillator (YTO) 34, 35 Local oscillator 40 TG (tracking generator) unit 41 Oscillator 42 Fourth mixer 43 Fifth mixer 44 Sixth mixer 45 ATT 46 Output terminal 50 S-parameter spectrum analyzer 5 RF front end unit 52 directional coupler (Reflection bridge) 53 input switches 54 computing means (MyuCPU) 55 memory 57 output terminal 58 input terminal

Claims (1)

[Claims] A TG unit (4) which oscillates and outputs the same frequency as the analyzed frequency for analyzing the spectrum of an external frequency.
0), the output frequency of the TG section (40) is measured by the output terminal (5
7) A directional coupler (52) that outputs the signal from the output terminal (57) to the input switch (53).
An input switch (53) for switching between an input signal from an input terminal (58) and an input signal from the directional coupler (52) and inputting the input signal to the spectrum analyzer; and the directional coupler (52). And the input switch (5)
3) The memory (55) storing the high-frequency characteristics of the RF front-end unit (51) composed of: and the analysis data of the A / D converter (30) that A / D-converts the level of the analyzed frequency. RF front end (5
A spectrum analyzer for measuring S-parameters, comprising: a computing means (54) for compensating and computing with the high-frequency characteristic compensation data of (1), calculating S-parameters and outputting them to the display (31).