JP3541345B2 - Amplitude / phase measurement system and amplitude / phase measurement method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an amplitude / phase measurement system and an amplitude / phase measurement method, and more particularly to an amplitude / phase measurement system and an amplitude / phase measurement method for performing quadrature adjustment of a quadrature modulator.
[0002]
[Prior art]
In general, in a digital modulation method such as QPSK (Quadrature Phase Shift Keying) modulation (four-phase shift keying), a quadrature modulator that modulates mutually orthogonal local signals with a baseband signal is used. In this QPSK modulation, for example, as shown in FIG. 2, two columns of baseband signals of an I channel and a Q channel are input to mixers 1a and 1b, and the baseband signals are cos (2πft) and sin. The mutually orthogonal local frequencies of (2πft) are modulated. Then, the modulated signals are combined by the combiner 2, and the combined signal is output as a QPSK modulated signal. Here, f is a local frequency, and t is time. A similar quadrature modulator is described in Japanese Patent Application Laid-Open No. 6-350658.
[0003]
As shown in FIG. 3, this QPSK modulated wave has four signal points A, B, C, and D having the same amplitude at intervals of 90 [deg] on the phase plane. That is, the distance from the origin O to each signal point in FIG. 3 is the same, and the line segment AO and the line segment BO, the line segment BO and the line segment DO, the line segment DO and the line segment CO, and the line segment CO and the line segment Each angle of AO is 90 [deg].
[0004]
However, in practice, the phase angle between signal points and the amplitude value vary due to the quadrature deviation of the local signal and the amplitude deviation of the baseband signal. For this reason, it is necessary to measure and adjust the modulation amplitude and phase amount at the time of manufacturing the modulator so that the variation falls within the tolerance required for the performance of the device. Usually, the measurement of the amplitude and phase amount of QPSK modulation is performed by measuring the relative amplitude value and phase amount between four signal points output from the modulator using the amplitude and phase of the local signal as reference values. Is For this measurement, an amplitude and phase measurement device such as a network analyzer is used.
[0005]
Here, a description will be given of an amplitude value and phase amount measurement system for a conventional double conversion type modulator with reference to FIG.
[0006]
FIG. 1 shows a modulation circuit board 5 on which modulators 5-1, changeover switches 5-2, mixers 5-3, and synthesizers (SYNTH) 10 and 11 are mounted. The modulator 5-1 on the substrate 5 modulates a local signal from the synthesizer 10 with the input baseband signals BB-I and BB-Q. The mixer 5-3 uses the local signal from the synthesizer 11 to perform frequency conversion on the output of the modulator 5-1. The output of the mixer 5-3 is derived from an output terminal 9. The output terminals 8 and 12 are measurement terminals used for adjusting amplitude and phase, which will be described later.
[0007]
The adjustment of the amplitude and phase of the PSK modulation wave for the modulation circuit board 5 is performed as follows. That is, the switch 5-2 is switched to derive the modulation output of the modulator 5-1 from the output terminal 8. Further, a local signal from the synthesizer 10 is derived from an output terminal 12. Then, the network analyzer 7 measures the phase and amplitude of the modulation output of the modulator 5-1 at each signal point of the signal derived from the original output terminal 9 with reference to the local signal derived from the output terminal 12. I do. Based on this measurement result, each signal point is adjusted so as to have the relationship shown in FIG.
[0008]
[Problems to be solved by the invention]
When measuring and adjusting the amplitude and phase of the above-described conventional PSK modulated wave, it is necessary to prepare a changeover switch 5-2 that is not necessary except for the measurement and adjustment on the substrate in advance. There is a disadvantage that the cost is increased and the circuit size is increased.
[0009]
In addition, in a double conversion type modulation circuit board in which the output of the modulator is frequency-converted by a mixer, only the output of the modulator is measured, and the output from the original output terminal cannot be measured. There is a disadvantage that the orthogonal state of the waves cannot be confirmed.
[0010]
The present invention has been made to solve the above-mentioned drawbacks of the prior art, and its object is to make it possible to easily measure and adjust a quadrature modulated wave and to minimize extra circuits mounted on a substrate. It is an object of the present invention to provide an amplitude and phase measurement system and an amplitude and phase measurement method that can be reduced.
[0011]
[Means for Solving the Problems]
An amplitude and phase measurement system according to the present invention includes quadrature modulation means for modulating a first local signal with a baseband signal, and converts the frequency of the modulation output of the modulation means using a second local signal and sends the result as a modulation output. An amplitude and phase measurement system for measuring an amplitude and a phase of a modulation device that performs the conversion, wherein a frequency converter that converts the frequency of the first local signal using the second local signal, A measuring device for measuring an amplitude and a phase of a modulation output of the modulation device.
[0012]
An amplitude and phase measurement method according to the present invention includes quadrature modulation means for modulating a first local signal with a baseband signal, and converts the frequency of the modulation output of the modulation means using a second local signal, and sends the result as a modulation output. An amplitude and phase measurement method for measuring an amplitude and a phase of a modulation device, wherein the frequency of the first local signal is converted using the second local signal, and the modulation is performed based on the converted output. Measuring the amplitude and phase of the modulated output of the device.
[0013]
In short, in this system, in a double conversion type quadrature modulation circuit, the monitor output of each local signal generator is frequency-converted by an external mixer, and the amplitude and phase measurement device uses the output of the external mixer as the reference signal to modulate the modulation output of the modulator. And the modulation phase. Further, in the double conversion type quadrature modulation circuit, after the monitor output of the synthesizer is frequency-converted by an external mixer, filtering is performed by a filter circuit for removing unnecessary waves, and the modulation amplitude and The modulation phase is being measured.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings referred to in the following description, the same parts as those in the other drawings are denoted by the same reference numerals.
[0015]
FIG. 1 is a block diagram showing an embodiment of an amplitude / phase measurement system and an amplitude / phase measurement method according to the present invention. 4, the same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description of those parts will be omitted.
[0016]
As shown in the figure, in the present system, a local signal from the synthesizer 10 is derived from a monitor terminal 12, and a local signal from the synthesizer 11 is derived from a monitor terminal 13. Then, the mixer 6-1 mounted on the jig substrate 6 prepared separately from the substrate 5 converts the frequency of the local signal derived from the monitor terminal 12 using the local signal derived from the monitor terminal 13. I do. Using this converted output as a reference signal, the network analyzer 7 measures the phase and amplitude of the modulated output of the modulator 5-1 at each signal point of the signal under measurement derived from the original output terminal 9. Based on this measurement result, each signal point is adjusted so as to have the relationship shown in FIG.
[0017]
Here, in the present system, an unnecessary wave is removed from the output of the mixer 6-1 by a band-pass filter (BPF) 6-2, and then input to the network analyzer 7 as a reference signal.
[0018]
The frequency of the local signal derived from the monitor terminal 12 is f1 = 813 [MHz], and the frequency of the local signal derived from the monitor terminal 13 is f2 = 953 [MHz]. Then, the signal output from the mixer 6-1 and input to the bandpass filter 6-2 is f2-f1 = 140 [MHz], 2 * f1-f2 = 673 [MHz], and 2 * f2-f1 = 11093. Many frequency components such as [MHz] are included.
[0019]
Therefore, since the frequency of the signal output from the output terminal 9 of the substrate 5 is 140 [MHz], the center frequency of the pass band is 140 [MHz] to extract a local signal of 140 [MHz], and other spurious components are generated. A band pass filter 6-2 having a pass band width that does not enter the pass band is used. The local signal of 140 [MHz] which is the output of the external mixer passing through the band-pass filter 6-2 has the same frequency as the output frequency of the modulator. Therefore, the local signal of 140 [MHz] is input to the network analyzer 7 as a reference signal, and the reference signal is compared with the PSK modulation wave output from the output terminal 9 of the modulation circuit board 5 to obtain the phase and the phase. The amplitude value can be measured and adjusted.
[0020]
As described above, since the local signal is derived from the monitor terminal and used as the reference signal, the phase and amplitude values of the quadrature modulation output can be measured and adjusted using the final output of the modulator. In addition, the circuit size can be minimized by removing extra circuits such as a changeover switch dedicated to orthogonal adjustment on the substrate 5.
[0021]
Further, the system includes quadrature modulation means for modulating the first local signal with a baseband signal, and modulates the frequency of the modulation output of the modulation means using the second local signal and sends the modulated output as a modulation output. I am performing an amplitude and phase measurement method to measure the amplitude and phase of the device, and in that method,
The frequency of the first local signal is converted using the second local signal, and the amplitude and phase of the modulation output of the modulation device are measured based on the converted output.
[0022]
The present invention may take the following aspects in connection with the description of the claims.
[0023]
(1) The amplitude and phase measurement system according to any one of claims 1 to 3, wherein the modulator and the measurement device are provided outside the modulation device.
[0024]
(2) The amplitude and phase measurement method according to any one of claims 4 to 6, wherein the modulator and the measuring device are provided outside the modulation device.
[0025]
【The invention's effect】
As described above, the present invention measures and adjusts the phase and amplitude values of the quadrature modulation output using the final output of the modulator by deriving the local signal from the monitor terminal and using the reference signal as the reference signal. Has the effect that the orthogonal state can be confirmed. In addition, there is also an effect that an extra circuit such as a changeover switch dedicated to orthogonality adjustment can be eliminated to minimize the circuit scale.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an amplitude and phase measurement system according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a general QPSK modulator.
FIG. 3 is a diagram illustrating a phase relationship between QPSK modulated waves.
FIG. 4 is a block diagram showing a configuration of a conventional amplitude / phase measurement system.
[Explanation of symbols]
5 Modulation circuit board 5-1 Modulator 5-2 Switch 5-3, 6-1 Mixer 6 Jig board 6-2 Bandpass filter 7 Network analyzer 9 Output terminal 10, 11 Synthesizer 12, 13 Monitor terminal

Claims (6)

An orthogonal modulation means for modulating a first local signal with a baseband signal, and using a second local signal to convert the frequency of the modulation output of the modulation means and transmitting the amplitude and phase of the modulation device as a modulation output. An amplitude and phase measurement system for measuring, comprising: a frequency converter that converts a frequency of the first local signal using the second local signal; and an amplitude of a modulation output of the modulation device based on the converted output. And a measuring device for measuring the phase. The modulation device includes first and second monitor terminals for respectively outputting the first and second local signals to the outside of the device, and the frequency converter uses the second local signal to generate the first local signal. 2. The amplitude / phase measurement system according to claim 1, wherein the frequency of the signal is converted. The apparatus further includes a band-pass filter that receives an output of the frequency converter as an input and removes a signal in a frequency band other than a predetermined frequency band, and the measuring device measures an amplitude and a phase of a modulation output of the modulation device based on the removed output. 3. The amplitude / phase measurement system according to claim 1, wherein the amplitude / phase measurement system performs the measurement. An orthogonal modulation means for modulating a first local signal with a baseband signal, and using a second local signal to convert the frequency of the modulation output of the modulation means and transmitting the amplitude and phase of the modulation device as a modulation output. A method for measuring an amplitude and phase, comprising: converting a frequency of the first local signal using the second local signal; and an amplitude and a phase of a modulation output of the modulation device based on the converted output. And measuring the amplitude and phase. The modulation device includes first and second monitor terminals for respectively outputting the first and second local signals to the outside of the device, and the frequency converter uses the second local signal to generate the first local signal. The method according to claim 4, wherein the frequency of the signal is converted. The apparatus further includes a band-pass filter that receives an output of the frequency converter as an input and removes a signal in a frequency band other than a predetermined frequency band, and the measuring device measures an amplitude and a phase of a modulation output of the modulation device based on the removed output. 6. The method according to claim 4, wherein the amplitude and phase are measured.

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