JP4138059B2 - Spectrum analyzer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spectrum analyzer that has a plurality of independent input measurement units and performs synchronous sweeping.
[0002]
[Prior art]
An example of the prior art will be described with reference to FIG.
As shown in FIG. 5, the configuration of the conventional spectrum analyzer includes a mixer 11, a local oscillator 21, an IF filter 31, a detector 41, an A / D converter 51, a ramp generator 61, and a signal. And a processing / display unit 81.
[0003]
The operation of the conventional spectrum analyzer will be described below.
The input signal under measurement is frequency-mixed with the signal from the local oscillator 21 by the mixer 11 and converted to an IF signal. The IF signal filtered to a desired bandwidth by the IF filter 31 is detected by the detector 41 to a DC voltage proportional to the AC level of the IF signal. The DC voltage output from the detector is converted into a digital signal by the A / D converter 51. The converted digital signal is subjected to predetermined data calculation in the signal processing / display unit 81, and the calculation result is displayed on the display.
[0004]
On the other hand, the ramp generator 61 generates a sawtooth voltage, and this output signal controls the A / D converter 51 in response to the ramp sweep. Further, by sweeping the local oscillator 21 with a sawtooth voltage from the ramp generator 61, a frequency span on the horizontal axis in the frequency domain is set. Here, the frequency span refers to a frequency section from the start to the end of the frequency on the horizontal axis on the display screen.
In the case of a so-called zero span where the frequency span is 0, the time domain display of a single frequency signal with the horizontal axis as the time axis can be achieved.
Therefore, measurement in the frequency domain or time domain can be performed.
[0005]
Further, by applying an external trigger signal to the ramp generator 61 from the trigger input end, synchronized ramp sweep control can be performed.
Further, when the input signal is a burst wave, measurement can be performed in synchronization with the burst wave by an external trigger signal.
[0006]
In order to use this conventional spectrum analyzer as a receiver for measuring a signal of a single frequency, a zero frequency span, a so-called zero span, is set, and the center frequency is set to a carrier frequency after frequency tuning.
[0007]
Next, in the TDMA communication system as a specific measurement object, for example, in PHS (Personal Handy Phone System), as shown in FIG. 3A, the reference control channel of the burst wave of frequency f1 is used as the reference time, and the frequency When measuring the time delay t1 with the communication channel information A of f2, since the frequencies f1 and f2 of both channels are different, the receiver for tuning to the frequency f1 to obtain the reference time and the waveform observation tuning to the frequency f2 Receiver is required.
Furthermore, in order to synchronize the receiver for obtaining the reference time and the receiver for waveform observation, a circuit for extracting a trigger signal as a synchronization signal from the receiver for obtaining the reference time is provided, and the trigger signal is used for waveform observation. Need to be supplied to the trigger input terminal of the receiver.
[0008]
Here, TDMA (Time Division Multiple Access) is a time division multiple access method, in which information (A, B, C,...) Of a plurality of users is shifted with respect to time, and one carrier wave is obtained. It is a method to put on.
[0009]
Furthermore, as shown in FIG. 4, in mobile communication, the path of a signal transmitted from the base station 91 passes through the reflection path 500 reflected by the reflector 93 in addition to the direct path 400. There is a multipath propagation environment that reaches
In order to measure the propagation delay time between the same signals by such multipath and ghost, it is necessary to obtain a time difference between signals received using the reference antenna and the measurement antenna. Again, two receivers are required.
[0010]
[Problems to be solved by the invention]
As described above, when measuring the time difference between two signals having different frequencies and the time delay between signals at the same frequency, two receivers are required. Even if a conventional spectrum analyzer is used, it is necessary to add a circuit for extracting a synchronization signal, which is inconvenient in practice.
Therefore, the present invention has been made in view of these problems, and an object of the present invention is to provide a spectrum analyzer capable of measuring a time difference between two signals having different carrier frequencies and a time delay between signals at the same frequency. is there.
[0011]
[Means for solving the problems]
The first aspect of the present invention made to achieve the above object is as follows.
The gist of the present invention is a spectrum analyzer having at least two independent input measurement units and having a demodulator that demodulates an IF signal obtained from an input signal of one input measurement unit and supplies a trigger signal. .
The second aspect of the present invention made to achieve the above object is as follows.
A first mixer that receives the first input signal and converts the frequency with the first local signal;
A first IF filter for extracting an IF signal from the signal frequency-converted by the first mixer;
A demodulator that demodulates the IF signal of the first IF filter to generate a trigger signal;
A first detector for detecting the IF signal of the first IF filter;
A first ramp generator for generating a ramp signal synchronized with an output signal of the demodulator;
A first A / D converter that receives a detection output of the first detector and performs A / D conversion based on a signal from the first ramp generator;
A first local oscillator for generating the first local signal based on a signal from the first ramp generator;
[0012]
A second mixer that receives the second input signal and performs frequency conversion with the second local signal;
A second IF filter for extracting an IF signal from the signal frequency-converted by the second mixer;
A second detector for detecting the IF signal of the second IF filter;
A second ramp generator for generating a ramp signal synchronized with the output signal of the demodulator;
A second A / D converter that receives a detection output of the second detector and performs A / D conversion based on a signal from the second ramp wave generator;
A second local oscillator for generating the second local signal based on a signal from the second ramp generator;
The gist of the present invention is a spectrum analyzer comprising a means for computing the digital signal from the first A / D converter and the digital signal from the second A / D converter and displaying the result. .
[0013]
Furthermore, the third aspect of the present invention made to achieve the above object is as follows.
In the above spectrum analyzer,
In addition to the configuration of the second input measurement unit,
A selection means for selecting and outputting the detection output signal of the first detector or the detection output signal of the second detector is provided in a stage preceding the second A / D converter,
The gist of the spectrum analyzer is that two identical signals under measurement can be measured in parallel.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in the following examples.
[0015]
【Example】
An embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, the configuration is the same as that of the conventional configuration including the mixer 11, the local oscillator 21, the IF filter 31, the detector 41, the A / D converter 51, and the ramp generator 61. A signal processing / display unit 80 that performs data processing for a minute, a mixer 12, a local oscillator 22, an IF filter 32, a detector 42, an A / D converter 52, a ramp generator 62, and a demodulator. 70 and a two-channel input measurement unit.
[0016]
The measurement of the two-channel input signals of CH1 and CH2 is the same as that of the prior art when the independent spectrum analyzer is used, and the description thereof will be omitted. As a spectrum analyzer having a two-channel input measurement unit different from the prior art The operation of will be described below.
[0017]
The spectrum analyzer of the present invention enables synchronous sweeping with a signal of one channel with respect to an input of two channels.
That is, the IF signal 100 output from the IF filter 31 is demodulated by the demodulator 70 to generate the trigger signal 200.
For example, as shown in FIG. 3A, a trigger signal is detected when a burst wave reference control signal is detected.
The trigger signal 200 synchronizes the start of sweeping of the ramp generators 61 and 62.
The demodulator 70 has a function of demodulating the original signal from the carrier wave modulated by the signal wave, and has a general detection function, so that another trigger signal can be generated from the demodulated signal of the IF signal 100.
[0018]
Next, a method for measuring the time delay t1 with respect to the information A of the communication channel with the frequency f2 using the reference control channel with the frequency f1 as a specific measurement object shown in FIG. .
[0019]
A signal of the reference control channel is received at the signal input terminal of CH1, and is frequency tuned to the frequency f1, and then a signal of the communication channel is received at the signal input terminal of CH2, and is frequency tuned to the frequency f2, A desired sweep time is set as a so-called zero span.
[0020]
As a result, as shown in FIG. 3B, information A, B, and C of the reference control channel of frequency f1 and the communication channel of frequency f2 are displayed as respective envelopes in the time domain.
Therefore, the time delay t1 can be measured by simultaneously sweeping and observing CH1 and CH2.
[0021]
Also, as shown in FIG. 4, a method for measuring time delay due to propagation delay due to multipath between signals of the same frequency will be described.
In this case, a reference antenna and a measurement antenna are provided at the point of the mobile station 92, and the signals are connected to the inputs of CH1 and CH2, respectively. Then, tuning is performed according to the signal frequency received at the inputs of CH1 and CH2. Next, by sweeping both channels with the same trigger signal as a zero frequency span, the time delay between the direct signal path 400 and the reflection path 500 can be measured on the time domain display screen.
[0022]
In the above description, the spectrum analyzer of the present invention is capable of synchronous sweeping with a signal of one channel with respect to two channels of input. However, the spectrum analyzer of the present invention is not limited to two channels, A plurality of n channels may be configured.
[0023]
Next, another embodiment is shown.
As another embodiment of the present invention, as shown in FIG. 2, a selection means 75 is provided in the preceding stage of the A / D converter 52 to determine whether the detection signal 300 of the detector 41 or the detection signal 600 of the detector 42 is present. Configure to enable selective output.
As a result, the detection signal 300 of the detector 41 is branched and given to each A / D converter (51, 52), so that the same signal is independently generated by the A / D converter 51 and the A / D converter 52. A / D conversion can be performed in parallel.
Therefore, the measurement of the input signal of CH1 under two different measurement conditions can be performed with a single sweep.
In the case of the conventional spectrum analyzer, when the measurement was performed under two different measurement conditions, it was swept twice. Therefore, in the application example of the present invention, the measurement time is halved, and high-speed measurement with twice the conventional throughput can be performed. become.
[0024]
Also in the above embodiment, the spectrum analyzer of the present invention is not limited to two channels, and may be configured as a plurality of n channels.
In this case, it is possible to perform high-speed measurement with n times the conventional throughput.
[0025]
By the way, in each of the above embodiments, the mixer and IF filter have a single-stage principle configuration for the sake of simplicity, but a general configuration of multi-stage conversion can be similarly implemented.
In addition, although an example of operation in which sweeping is synchronized has been described, by providing a demodulator for each channel, each channel can be operated asynchronously. In this case, the operation is the same as that of the n spectrum analyzers, but the data processing can be performed under the same conditions, so that the relative comparison of data becomes easy.
[0026]
【The invention's effect】
The present invention is implemented in each form as described above, and has the effects described below.
That is, since the IF signal of one channel is demodulated and synchronously swept as a trigger signal common to n channels, the time difference between n signals having different carrier frequencies or the signal frequency in the multipath of the same frequency signal is used. This has the effect of measuring the time delay.
Further, when the same input signal is independently A / D converted in parallel by n A / D converters, the measurement under different measurement conditions can be performed by one sweep, and thus there is an effect that the measurement can be performed at a high speed.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of a spectrum analyzer of the present invention.
FIG. 2 is a block diagram of another embodiment of the spectrum analyzer of the present invention.
FIG. 3A is a signal waveform example of PHS communication.
(B) A measurement waveform in the time domain of PHS communication.
FIG. 4 is an example of occurrence of multipath.
FIG. 5 is a block diagram of a conventional spectrum analyzer.
[Explanation of symbols]
11, 12 Mixer 21, 22 Local oscillator 31, 32 IF filter 41, 42 Detector 51, 52 A / D converter 61, 62 Ramp generator 70 Demodulator 75 Selection means 80, 81 Signal processing / display unit 91 Base Station 92 Mobile station 93 Reflector 100 IF signal 200 Trigger signal 300, 600 Detection signal 400 Direct path 500 Reflection path

Claims (4)

A ramp generator that receives a trigger signal and sweeps synchronously; a local oscillator that generates a local signal based on a signal from the ramp generator; and a mixer that receives an input signal to be measured and converts the frequency using the local signal in a spectrum analyzer having an input measurement unit and a detector for detecting an output signal from the mixer,
Having at least two independent input measuring units;
A demodulator that demodulates an input signal of one input measurement unit and supplies a trigger signal to another input measurement unit;
Means for calculating the detector output of each input measurement unit and displaying the result;
A spectrum analyzer, wherein an input signal of one input measurement unit can be measured by synchronously sweeping an input signal of another input measurement unit. A plurality of n independent input measuring units;
The i-th input measurement unit is
An i-th mixer that receives the i-th input signal and performs frequency conversion with the i-th local signal;
An i-th IF filter for extracting an IF signal from the signal frequency-converted by the i-th mixer;
A demodulator that demodulates the IF signal of the i-th IF filter and generates a trigger signal;
An i-th detector for detecting the IF signal of the i-th IF filter;
An i-th ramp generator that sweeps synchronously with an output signal of the demodulator;
An i-th A / D converter that receives a detection output of the i-th detector and performs A / D conversion based on a signal from the i-th ramp generator;
An i-th local oscillator for generating the i-th local signal based on a signal from the i-th ramp generator ,
The other (n−1) input measurement units are
A jth mixer that receives the jth input signal and performs frequency conversion with the jth local signal;
A jth IF filter for extracting an IF signal from the signal frequency-converted by the jth mixer;
A jth detector for detecting the IF signal of the jth IF filter;
A j-th ramp generator that sweeps synchronously with an output signal of the demodulator;
A jth A / D converter that receives a detection output of the jth detector and performs A / D conversion based on a signal from the jth ramp generator;
A jth local oscillator for generating the jth local signal based on a signal from the jth ramp generator ,
A spectrum analyzer comprising means for calculating each digital signal from the n A / D converters and displaying the result. A first mixer that receives the first input signal and converts the frequency with the first local signal;
A first IF filter for extracting an IF signal from the signal frequency-converted by the first mixer;
A demodulator that demodulates the IF signal of the first IF filter to generate a trigger signal;
A first detector for detecting the IF signal of the first IF filter;
A first ramp generator for generating a ramp signal synchronized with an output signal of the demodulator;
A first A / D converter that receives a detection output of the first detector and performs A / D conversion based on a signal from the first ramp generator;
A first local oscillator for generating the first local signal based on a signal from the first ramp generator;
A second mixer that receives the second input signal and performs frequency conversion with the second local signal;
A second IF filter for extracting an IF signal from the signal frequency-converted by the second mixer;
A second detector for detecting the IF signal of the second IF filter;
A second ramp generator for generating a ramp signal synchronized with the output signal of the demodulator;
A second A / D converter that receives a detection output of the second detector and performs A / D conversion based on a signal from the second ramp wave generator;
A second local oscillator for generating the second local signal based on a signal from the second ramp generator;
Means for computing the digital signal from the first A / D converter and the digital signal from the second A / D converter and displaying the result;
A spectrum analyzer characterized by comprising: The spectrum analyzer according to claim 2 , wherein
The other (n−1) input measurement units are :
In front of the j-th A / D converter comprises a j-th selecting means selectively outputs either the detection output signal of said i th detector of the detection output signal or said j th own detector ,
A spectrum analyzer that can measure n signals to be measured in parallel.

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