JP3375318B2 - Signal generator with crest factor characteristic measurement function - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal generator that quadrature-modulates a pair of analog baseband signals in a quadrature modulator and outputs the test signal, and more particularly, to a crest factor characteristic of the test signal to be output. The present invention relates to a signal generator having a crest factor characteristic measuring function for measuring.

[0002]

2. Description of the Related Art In a mobile communication system such as a mobile phone, a CDMA (Code Division Multiple Access) that can secure a large number of communication channels is used as a modulation method of a signal wave transmitted and received between a base station and each mobile terminal. ) Method is adopted.

In this CDMA system, a digital data signal of each channel is spectrum-spread by, for example, a PN pattern signal different for each channel, and the spectrum-spread signals of each channel are added by a signal adder to add signals. The generated signal is phase-modulated and frequency-converted to a high frequency, and the high frequency CDMA modulated signal is amplified by an RF amplifier to form one CDMA modulated signal.

When demodulating this CDMA modulated signal,
First, quadrature demodulation is performed, and spectrum despreading is performed on the demodulated demodulated signal with a PN pattern signal that is different for each channel. This one CDMA modulated signal contains digital data signals of many channels. One mobile terminal is assigned to one channel.

Not all mobile terminals using this one CDMA modulated signal are always in use. Therefore, the power of this CDMA modulated signal greatly changes according to the usage status of each mobile terminal. As a result, for example,
If the dynamic range of the circuit for transmitting / receiving each CDMA modulated signal is narrow, the circuit is saturated and adversely affects adjacent channels.

The degree of influence on the adjacent channel caused by the narrowness of this circuit is greatly influenced not only by the instantaneous magnitude (maximum value) of the power of this CDMA modulated signal but also by its frequency of occurrence (occurrence probability). .

For this reason, when an amplifier or the like incorporated in a communication device adopting the CDMA system is evaluated, the distribution of the instantaneous power of the test signal applied from the signal generator to the circuit to be evaluated is evaluated by the circuit to be evaluated. You need to know exactly how the output of changes.

Therefore, the crest factor characteristic of the test signal, that is, the power ratio between the instantaneous power at each time within a predetermined measurement time in the test signal and the average power over the entire measurement time (instantaneous power / average power) It is necessary to measure the relationship with the occurrence probability of.

FIG. 8 shows an example of the crest factor characteristic. As shown in the figure, the horizontal axis of the graph is the power ratio (instantaneous power / average power), and the vertical axis is the probability of occurrence (density) of each power ratio within the measurement time. The scale of each axis is a logarithmic scale. Generally, the probability of occurrence of high instantaneous power is low and the probability of occurrence of low instantaneous power is high.

Conventionally, when displaying such a crest factor characteristic, the following two methods have been adopted.

The first method is a simulation method in which after the generation of multiple baseband data, the crest factor is obtained only by calculation using the generated digital data and the crest factor characteristic is displayed on the display.

In the second method, as shown in FIG. 9, a test signal a, which is, for example, a CDMA modulated signal output from the signal generator 1, is A / D converted by an A / D converter 2, and the arithmetic unit is operated. This A / D converted digital test signal a ₁
Is calculated, and the crest factor characteristic shown in FIG. 8 is graphically displayed on the display 4.

[0013]

However, the simulation method, which is the first method, calculates the crest factor based on the digital data generated by the signal adder in FIG. , For example D /
The ideal simulation result does not include the characteristics of the A converter 2, the analog AMP, etc., and may be slightly different from the characteristics of the actual RF output signal. Furthermore, the crest factor characteristic cannot be displayed at all for the analog I / Q signal input from the outside.

The second method, which is a method of sampling an RF signal by an A / D converter, is the actually output RF signal.
Since the signal is measured, the crest factor characteristic can be displayed most accurately. I / input from the outside
The crest factor characteristic can be displayed for the Q signal.

However, this RF signal has been converted to a high frequency by the frequency conversion section 15 of FIG.
This signal is A / D because it is amplified by the F amplifier 16.
When sampling with a converter, a high-speed A / D converter and a large-scale circuit are required.

The present invention has been made in view of such circumstances, and by using the I / Q signal immediately before being input to the quadrature modulator, the measurement circuit can be a simple low-speed A / D converter. A crest factor characteristic that allows the circuit to be implemented and, unlike the simulation from digital data, realizes the measurement of the actual signal and also the crest factor characteristic that can measure the I / Q signal input from the outside. An object is to provide a signal generator having a function.

[0017]

According to the present invention, a plurality of channels of baseband signals input from the outside are combined, and a pair of analog baseband signals of a synchronization component and a quadrature component are quadrature-modulated by a quadrature modulator. It is applied to a signal generator that outputs a CDMA test signal.

In order to solve the above problems, in the signal generator having the crest factor measuring function of the present invention, a pair of baseband signals are input to the quadrature modulator.
From one end, a pair of A / D converters that sample a pair of baseband signals and convert them into digital values, and each of the baseband signals output from the pair of A / D converters for the measurement period. Instantaneous power calculating means for calculating the instantaneous power for each sampling from a pair of digital values,
An average power calculating means for calculating the average power in the measurement period from each instantaneous power calculated by the instantaneous power calculating means,
At least, the instantaneous power at each sampling exceeds the average power. A power ratio calculating means for calculating a power ratio between the instantaneous power at sampling and the calculated average power, and a power ratio calculation means for calculating each power ratio. An occurrence probability calculating means for calculating an occurrence probability over the measurement period, and an occurrence probability characteristic output means for outputting the occurrence probability of each power ratio calculated by the occurrence probability calculating means in a graphic format as a crest factor characteristic, the crest CDM for factor characteristics
Of the circuit to be evaluated incorporated in the communication equipment that adopted the A method
It is possible to grasp the output.

In the signal generator having the crest factor measuring function configured as described above, the pair of analog baseband signals before being quadrature-modulated by the quadrature modulator are sampled by the A / D converter to obtain the instantaneous power. Is calculated. Further, the average power during the measurement period is obtained. Then, the crest factor characteristic is calculated from the instantaneous power and the average power for each sampling, and is output in a graphic format.

In this way, the crest factor characteristic is calculated using a pair of analog baseband signals before being quadrature-modulated by the quadrature modulator, so that the influence of the actually output signal on the baseband is taken into consideration. It is also possible to measure the crest factor of the external I / Q input signal.

According to another invention, the crest factor characteristic measuring function described above is used to generate a plurality of channels of baseband signals, combine them, and further separate them into an in-phase component and a quadrature component to form a pair of analog baseband signals. Incorporated into a signal generator that has a baseband generator that outputs a pair of analog baseband signals output from the baseband signal generator and outputs the test signal as quadrature-modulated by the quadrature modulator. Is.

Further, in another invention, the crest factor characteristic measuring function described above is also provided, and a signal input terminal provided in a position electrically parallel to the baseband signal generating section, a baseband signal generating section and quadrature modulation. A pair of analog baseband signals input from either the baseband signal generation unit or the signal input terminal and quadrature-modulated by the quadrature modulation unit for testing. It is built into a signal generator that outputs as a signal.

Also in each of the inventions thus configured,
Since the crest factor characteristic is calculated using the analog baseband signal before quadrature modulation, it is possible to obtain substantially the same operational effect as the above-described invention.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a signal generator having a crest factor characteristic measuring function according to the embodiment.

A pair of analog baseband signals I (in-phase component) output from the baseband signal generator 11,
The Q (quadrature component) is input to the quadrature modulator 14 via one end of the switching terminals 12a and 12b. Switching terminal 12a,
At the other end of 12b, signal input terminals 13a and 13b for taking in a pair of analog baseband signals I and Q from the outside and guiding them to the quadrature modulator 14 other than the baseband signal generator 11 as necessary. Are connected.

The quadrature modulator 14 quadrature modulates the carrier signal with the baseband signals I and Q and outputs it as a CDMA modulated signal b. The CDMA modulation signal b output from the quadrature modulation unit 14 is frequency-converted into a high frequency CDMA modulation signal b by the frequency conversion unit 15 and further high frequency amplified by the RF amplifier 16 to output the final test signal b ₁ from the output terminal 17. Is output.

The baseband signal generator 11 is, for example,
It is configured as shown in FIG. The baseband signal generator 11 is assumed to be a base station in a mobile communication system. K pattern signal generators 18 ₁ to 18 ₁ for generating pattern signals as digital test signals of different N channels corresponding to respective mobile terminals of communication destinations.
Pattern signal k ₁ output from the 8 _K to k _K are respectively input to the modulation signal generator 19 ₁ ~ 19 _K.

The modulated signal generators 19 _{1 to} 19 _K spread the spectrum of the pattern signals k _{1 to} k _K input by the separately input PN pattern signals for the respective channels, and the spread spectrum signals m ₁ to The signal addition unit 20 adds the signals m _k to convert them into a pair of baseband signals I and Q. The pair of digital baseband signals I and Q are converted into analog baseband signals I and Q by the D / A converters 21a and 21b, respectively, and sent from the baseband signal generator 11 to the quadrature modulator 14. .

In the baseband signal generator 11 thus constructed, each of the modulated signal generators 19 ₁ ...
By controlling 19 _K , the output can be arbitrarily turned on / off for each of channels 1 to _K. In addition, each pattern generator 1
It is possible to arbitrarily set the test pattern signal to be transmitted by using each channel of ₁ to _K by controlling 8 ₁ to 18 _K.

The quadrature modulator 14 is constructed as shown in FIG. The carrier signal c output from the carrier signal generator 22 is directly input to one of the signal multipliers 23a, and the 90 ° phase shifter 24 shifts the phase to 90 °.
Is converted and input to the other signal multiplier 23b.

The input analog baseband signals I and Q are respectively multiplied by the carrier wave signal c by the signal multipliers 23a and 23b, and then the signals are combined by the signal combiner 25, and then the CDMA modulated signal b is obtained. The signal is output from the quadrature modulator 14 to the frequency converter 15.

Baseband signal generator 11 in FIG.
Each analog baseband signal I, Q output from
Are input to the quadrature modulator 14 and the crest factor characteristic calculator 31.

The crest factor characteristic calculator 31 is composed of a kind of computer, and the input analog baseband signals I and Q are A / D converters 32a,
32b is applied. The A / D converters 32a and 32b sample the input analog baseband signals I and Q, convert them into digital values, and input them to the sampling memory 34 of the storage unit 33.

In the storage unit 33, in addition to the sampling memory 34 described above, an instantaneous power memory 35, an average power memory 36, a power ratio memory 37, and a work memory 38 are provided. FIG. 4 shows each memory 34 provided in the storage unit 33.
It is a detailed block diagram of ~ 38.

In the sampling memory 34, each A / D
Predetermined measurement period T output from the converters 32a and 32b
Each baseband signal I for every N samplings for _S ,
Each sampling value I ₁ ~I _N of Q, Q ₁ ~Q _N is written. In the instantaneous power memory 35, the above-mentioned 1 to N
Instantaneous power P _{1 to} P at each sampling point (point) of
_N (P _n = I _n ² + Q _n ² ) is written. Furthermore, in the average power memory 36, at each sampling of 1 to N (point)
The average power (root mean square) P _{m of the N} instantaneous powers P _{1 to} P _N in is written.

[0036]

[Equation 1]

Furthermore, in the power ratio memory 37, the instantaneous power P at each sampling time (point) of the above 1 to N is set.
₁ to P _N average power (mean square) previously calculated power divided by P _m ratio R ₁ to R _N is written.

R _n = P _n / P _{m In the} work memory 38, the power ratio _dividing memory 38a
An occurrence count cumulative memory 38b and an occurrence probability memory 38
c and are formed.

The power ratio divided memory 38a is in the range A ₁ to A _M value of each block in the case of partitioning into M blocks previously calculated the N power ratio R ₁ to R _N by size Remembered The number of occurrences in the cumulative memory 38b, each block of each of the ranges A ₁ to A _M, the cumulative number B of occurrences of the power ratio R ₁ to R _N belonging to the block are accumulated.

Further, in the probability memory 38c, each block of each of the ranges A ₁ to A _M, the cumulative number B the probability E divided by the total sampling number N of the corresponding block (%) is written.

Furthermore, in the crest factor characteristic calculation unit 31 of FIG. 1, the above-mentioned pair of A / D converters 32a and 3a,
2b, storage unit 33, instantaneous power calculation unit 39, average power calculation unit 40. A power ratio calculation unit 41, an occurrence rate calculation unit 42,
A characteristic output unit 43 and a display unit 44 are provided.

Then, the crest factor characteristic calculating section 31 carries out a crest factor characteristic calculating process in accordance with the flowchart shown in FIG.

The respective A / D converters 32a and 32b are activated and N baseband signals I and Q for a predetermined measurement period T _S are activated.
Each sampling value I ₁ ~I _N of, Q ₁ to Q _N acquired by writing to the sampling memory 34 of the storage unit 33 (S1).

Then, the instantaneous power calculator 36 calculates the instantaneous powers P _{1 to} P _N for each sampling and writes it in the instantaneous power memory 35. At the same time, the average power P _{m of the N} instantaneous powers P _{1 to} P _N is calculated and written in the average power memory 35 (S
2).

Next, the power ratio range A _{1 to} A _M of each block is set for counting the number of times the power ratio R of the work ratio memory 38a of the work memory 38 is generated (S3). Then, the power ratio calculation unit 41 is activated to read out one instantaneous power P stored in the instantaneous power memory 35, and the power ratio R to the average power P _m of the average power memory 35.
(= P / P _m ) is calculated (S4).

[0046] The calculated power ratio corresponding number of occurrences accumulated value B only one count-up of the block corresponding to the range A ₁ to A _M value of the power ratio divided memory 38 of the work memory 38 of the R (B = B + 1) (S5).

When the process for one momentary power P stored in the momentary power memory 35 is completed, the process returns to S3, and the process for the next momentary power P stored in the momentary power memory 35 is started.

Then, when the count-up process for the N instantaneous powers P stored in the instantaneous power memory 35 is completed (S6), the occurrence rate calculation unit 43 is activated and each range A
₁ to A for each block of _M, the cumulative number B the probability E divided by the total sampling number N of the corresponding block (%) (E ₁ ~
E _M ) is calculated and written in the occurrence probability memory 38a. Then, the characteristic output unit 43 is activated to display and output the crest factor characteristic 45 indicating the relationship between the power ratio R and the occurrence probability E (%) in a graphic format on the display screen of the display 44 (S7). .

More specifically, the horizontal axis represents the power ratio R (= P / P _m ) between the instantaneous power P and the average power P _m, which is LOG-converted d.
In B units, the vertical axis represents the occurrence probability E at each power ratio R
(%) Is shown on a logarithmic scale.

In the signal generator having the crest factor characteristic measuring function configured as described above, a pair of analog baseband signals output from the baseband signal generator 11 and not subjected to quadrature modulation by the quadrature modulator 14 are provided. I, Q
The A / D converter 32a, and converts the digital baseband signal I, the Q sampling Mr 32b, the baseband signals I, each sample value of 1~N of Q I ₁ ~I _N, Q ₁
From -Q _N, the instantaneous power P _{1 to} P _N for each sampling is calculated.

Further, the average power P _m during the measurement period T _S
Is required. Then, the instantaneous power P for each sampling
Each occurrence rate E in the average power P _m and the power ratio R ₁ to R _N
The crest factor characteristic 45 is calculated from (%) and is output to the display unit 44 in a graphic format.

FIG. 6A shows the baseband signal generator 11
FIG. 6 is a diagram showing the measurement results of each crest factor characteristic 45 when the number of channels in the on state (in use) is changed in FIG. According to this measurement result, when the number of channels in the ON state (in use state) increases, the probability of the high instantaneous power P increases within the predetermined measurement period T _S ,
The margin of the evaluation target electronic device to which the test signal b ₁ composed of the CDMA modulated signal output from this signal generator is applied becomes small.

FIG. 6B shows a case where the baseband signal generator 11 sets the output timing to the same (no offset) for the same number of channels in the ON state (in use) and the same pattern signal. It is a figure which shows the measurement result of each crest factor characteristic 45 when the output timing is set to a different value (with offset). According to this measurement result, it is shown that the probability of the high instantaneous power P increases within the predetermined measurement period T _{S as the} number of channels with the offset increases.

In the above description of the operation, the crest factor characteristic is calculated using the baseband signals I and Q output from the baseband signal generator 11. However, the crest factor characteristic 45 may be calculated using the baseband signals I and Q input from the outside via the signal input terminals 13a and 13b.

Furthermore, the present invention is not limited to the above embodiment. In embodiments, the baseband signal I, N pieces each Q component sample values I ₁ ~I _N,
After capturing Q _{1 to} Q _N in the sampling memory 34, the average power P _m was calculated, and then the power ratio R between the instantaneous power P and the average power P _m for each sampling was obtained in order.

[0056] However, as shown in the flowchart of FIG. 7, instead of the average power P _m, the reference value expected the average power P _m (reference power) is regarded as the average power P _m,
The power ratio between the instantaneous power and this reference value (reference power) is calculated in sequence. At the same time, the instantaneous power is cumulatively added.
Then, when the N power ratio is obtained, obtaining the correct average power P _m from the accumulated value of instantaneous power. Then, the scale on the horizontal axis of the crest factor characteristic 45 is corrected.

In such a calculation method, since the power ratio is obtained in the process of taking in _N sample values I _{1 to} IN and Q _{1 to} Q _N , the calculation processing speed can be improved and the sampling memory can be used. Since 34 is unnecessary, the configuration of the entire signal generator can be simplified.

[0058]

As described above, in the signal generator having the crest factor characteristic measuring function of the present invention, the crest factor characteristic is calculated using a pair of analog baseband signals before quadrature modulation. There is. Therefore, it is possible to measure the crest factor in which the influence in the baseband of the signal actually output is taken into consideration, and it is also possible to measure the crest factor of the external I / Q input signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a signal generator having a crest factor characteristic measuring function according to an embodiment of the present invention.

FIG. 2 is a diagram showing a detailed configuration of a baseband signal generator of the signal generator.

FIG. 3 is a diagram showing a detailed configuration of a quadrature modulator of the signal generator.

FIG. 4 is a diagram showing stored contents of a storage unit incorporated in a crest factor characteristic calculation unit in the signal generator.

FIG. 5 is a flowchart showing a crest factor characteristic calculation processing operation of a crest factor characteristic calculation unit in the signal generator.

FIG. 6 is a diagram showing a crest factor characteristic calculated by a crest factor characteristic calculation unit in the signal generator.

FIG. 7 is a flowchart showing a crest factor characteristic calculation processing operation of a crest factor characteristic calculation unit in a signal generator according to another embodiment of the present invention.

FIG. 8 is a diagram showing general crest factor characteristics.

FIG. 9 is a diagram showing a conventional method for measuring crest factor characteristics.

[Explanation of symbols]

11 ... Baseband signal generator 13a, 13b ... Signal input terminals 14 ... Quadrature modulator 15 ... Frequency converter 16 ... RF amplifier 31 ... Crest factor characteristic calculation unit 32a, 32b ... A / D converter 33 ... Storage unit 34 ... Sampling memory 35 ... Instantaneous power memory 36 ... Average power memory 37 ... Power ratio memory 39 ... Instantaneous power calculator 40 ... Average power calculator 41 ... Power ratio calculation unit 42 ... Incidence rate calculation unit 43 ... Characteristic output section 44 ... Indicator 45 ... Crest factor characteristics

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-11-252022 (JP, A) JP-A-10-153630 (JP, A) JP-A-2000-31918 (JP, A) JP-A-2001-116790 ( JP, A) JP 2000-230942 (JP, A) Von Klaus-Djeter Tiepermann und And pressure Hecht, Berechn ung des Crest-Fakt ors von, 1988, Signen len, Zeftrich. 52 No. 9-10, pp. 183-186 (58) Fields investigated (Int.Cl. ⁷ , DB name) H04J 13/00-13/06 H04B 1/69-1/713

Claims (3)

(57) [Claims] 1. A quadrature modulator (14) quadrature-modulates a plurality of channels of baseband signals input from the outside and synthesizes a pair of analog baseband signals (I, Q) of a synchronous component and a quadrature component. In the signal generator which outputs as the CDMA test signal, the pair of baseband signals are input to the quadrature modulator.
A pair of A / D converters (3) for sampling the pair of baseband signals and converting the baseband signals into digital values from one end.
2a, 32b), and an instantaneous power calculating means (39) for calculating the instantaneous power for each sampling from each pair of digital values for each measurement period in each baseband signal output from the pair of A / D converters. An average power calculating means (40) for calculating an average power in the measurement period from each instantaneous power calculated by the instantaneous power calculating means, and at least a sampling time at which the instantaneous power at each sampling exceeds the average power. Power ratio calculating means (4) for calculating a power ratio between the instantaneous power and the calculated average power.
1) and an occurrence probability calculation means (42) for calculating the occurrence probability of each power ratio calculated by the power ratio calculation means over the measurement period.
If, e Bei the occurrence probability characteristic output means for outputting an occurrence probability of each power ratio calculated in this occurrence probability calculating means as the crest factor characteristics in graphical form (43), said Kure
For the factor characteristics, the
To grasp the output of the evaluation target circuit built into the communication equipment
Signal generating apparatus having a crest factor characteristic measurement functions. 2. A baseband generator (11) for generating baseband signals of a plurality of channels, synthesizing the baseband signals, and outputting a pair of analog baseband signals separated into an in-phase component and a quadrature component. Then, in the signal generator for orthogonally modulating the pair of analog baseband signals (I, Q) output from the baseband signal generator by the orthogonal modulator (14) and outputting as a test signal, the pair of bases The band signal is input to the quadrature modulator.
A pair of A / D converters (3) for sampling the pair of baseband signals and converting the baseband signals into digital values from one end.
2a, 32b), and an instantaneous power calculating means (39) for calculating the instantaneous power for each sampling from each pair of digital values for each measurement period in each baseband signal output from the pair of A / D converters. An average power calculating means (40) for calculating an average power in the measurement period from each instantaneous power calculated by the instantaneous power calculating means, and a sampling moment at least the instantaneous power at each sampling exceeds the average power Power ratio calculating means (4) for calculating a power ratio between the power and the calculated average power.
1) and an occurrence probability calculation means (42) for calculating the occurrence probability of each power ratio calculated by the power ratio calculation means over the measurement period.
When, the probability characteristic output means for outputting an occurrence probability of each power ratio calculated in this occurrence probability calculating means as the crest factor characteristic (43) Bei example, the crest factor characteristic
In contrast, it was incorporated into a communication device that adopted the CDMA system.
A signal generator having a crest factor characteristic measuring function for grasping the output of a circuit to be evaluated . 3. A signal input terminal (13) provided at a position electrically parallel to the baseband signal generator (11).
a, 13b) and a switching unit (12a, 12b) provided between the baseband signal generation unit and the quadrature modulation unit.
And a quadrature modulation section (14) quadrature-modulates a pair of analog baseband signals (I, Q) input from one of the baseband signal generation section and the signal input terminal to obtain a test signal. The signal generator having the crest factor characteristic measuring function according to claim 2, wherein