JPH09135274A - Fading simulator for digital communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain miniaturization and low cost by adding a noise for fading to a base band modulation signal for balanced modulation so as to use only one standard orthogonal modulator enough from modulation of carrier till addition of the fading. SOLUTION: An IQ signal generating circuit 2 generates signals I, Q based on a prescribed bit pattern of a digital signal generated by a pattern generator 1. The signals I, Q are base band modulation signals to apply balance modulation to carriers with phase of 0, 90 deg. of the orthogonal modulation system and added to outputs of 1st and 2nd noise generating circuits 41, 42 at 1st and 2nd adders 43, 44 and the result is given to a standard orthogonal modulator 45. A signal generator 3 gives a carrier signal with an intermediate frequency corresponding to an input frequency of a device 5 to be evaluated being an object of evaluation, in which the modulation signals are modulated by the carrier with balanced modulation and the result is given to the device 9 to be evaluated. Thus, only one standard orthogonal modulator conducts from modulation of a carrier till addition of fading, then miniaturization and low cost are attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simulator for evaluating the performance of a digital communication device, and more particularly to a fading for digital communication for evaluating the fading resistance performance of a digital communication device using a quadrature modulation method. It is about simulators.

[0002]

2. Description of the Related Art Fading refers to a change over time in a radio frequency voltage induced in a receiving antenna of a communication device.
In this type of simulator, it is easier to generate a temporal change in the signal-to-noise ratio (hereinafter referred to as S / N ratio) than to generate a temporal change in the radio frequency voltage.
It is configured to generate equivalent fading by using the temporal change of the / N ratio. That is, the receiver of the wireless communication device is equipped with an AGC (automatic gain control) in the intermediate frequency amplifier, which increases the amplification degree for weak inputs and decreases the amplification degree for strong inputs. At the input point of the vessel, the amplitude is controlled to be almost constant. Therefore, if the amplification level increases, the noise increases, and if the amplification level decreases, the noise decreases.Conversely, adding large noise to the signal is equivalent to reducing the input signal due to fading. , Add little noise to a signal (or add no noise at all) to reduce fading or be equivalent to a lost input signal.

FIG. 2 is a block diagram showing an example of the structure of a conventional simulator of this type. Reference numeral 1 is a pattern generator for generating a predetermined bit pattern of a digital signal, and 2 is a bit pattern for the pattern generator 1. Based on the above, the IQ signal generating circuit 3 for generating the signals I and Q is a signal generator for generating a carrier wave signal of a radio frequency or an intermediate frequency corresponding to the input frequency of the device to be evaluated 5 to be evaluated. Here, the angular frequency of the signal generated by the signal generator 3 is ω. The signal I is 0 generated by the signal generator 3.
Is a baseband signal for generating a signal of Isin ωt by balance-modulating a carrier having a phase of 90 degrees. 6 is a standard quadrature modulator for performing such modulation. That is, in terms of S / N ratio, the output of the standard quadrature modulator 6 becomes the signal S.

In the conventional apparatus shown in FIG. 2, noise N is added in the same form as the signal S which is the output of the standard quadrature modulator 6. That is, 41 is a first noise (digital) generation circuit, 42 is a second noise (digital) generation circuit, 7 is a standard quadrature modulator similar to the standard quadrature modulator 6, and the output of the signal generator 3 The 0 ° phase carrier wave is balanced-modulated by the output of the noise generation circuit 41, and the 90 ° phase carrier wave output of the signal generator 3 is balanced-modulated by the noise generation circuit 42 output. The output of the standard quadrature modulator 7 is N (noise),
The signal of the S / N ratio thus obtained is input to the device under evaluation 5. Since the bit pattern generated by the pattern generator 1 is predetermined, the bit error rate can be measured from the output of the device under evaluation 5, and the output of the noise generating circuits 41, 42 is gradually increased to It is possible to measure what kind of bit error rate the S / N ratio has (that is, what kind of fading). In addition, the noise generation circuits 41 and 4 generate output changes that simulate temporal changes in fading that actually occur.
It is easy to give to the output of 2.

[0005]

Since the conventional fading simulator for digital communication is constructed as described above, two standard quadrature modulators are required, which hinders downsizing and cost reduction of the device. There was a problem.

The present invention has been made to solve the above problems, and an object of the present invention is to construct a fading simulator for digital communication having a function equivalent to that of a conventional device by a circuit of one standard quadrature modulator. There is.

[0007]

A fading simulator for digital communication according to the present invention has a structure in which noise for fading is added to a baseband signal and this is input as a modulation signal of a standard quadrature modulator.

Specifically, a baseband modulation signal I for balance-modulating a carrier of a 0 ° phase of a quadrature modulation system
And a first adder for adding the output of the first noise generating circuit, a baseband modulation signal Q for balance-modulating the carrier of 90 ° phase of a quadrature modulation method, and a second noise generating circuit And a carrier of 0 degree phase of the output of the signal generator is balanced-modulated by the output of the first adder, and a carrier of 90 degree phase of the output of the signal generator is added. A standard quadrature modulator that performs balanced modulation with the output of the second adder is provided.

The modulated signal I and the modulated signal Q are input to the output of a pattern generator that generates a predetermined bit pattern, and the input is converted into the signal I and the signal Q and output. It is characterized by the configuration input from.
Further, the noise output generated by the first noise generating circuit and the second noise generating circuit is characterized by changing with time according to a predetermined program.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining one embodiment of the present invention, in which 1 is a pattern generator for generating a predetermined bit pattern of a digital signal, and 2 is a bit pattern generated by the pattern generator 1. Based on
The IQ signal generating circuit 3 for generating the signals I and Q is a signal generator for generating a carrier signal of a radio frequency or an intermediate frequency corresponding to the input frequency of the device to be evaluated 5 to be evaluated. Here, the angular frequency of the signal generated by the signal generator 3 is ω. The signal I is a baseband signal for balanced-modulating the carrier of 0 degree phase generated by the signal generator 3 to generate a signal of Isin ωt, and the signal Q is generated by the signal generator 3. It is a baseband signal for generating a Qcos ωt signal by balance-modulating a 90 ° phase carrier.

Reference numeral 4 is a fading simulator in the present embodiment, 41 is a first noise generating circuit, 42 is a second noise generating circuit, 43 is a first adder, 44 is a second adder, and 45 is Standard quadrature modulator, 46 is a high frequency input terminal, 47 is a high frequency output terminal, and 48 and 49 are baseband signal output terminals. Reference numeral 5 is a device to be evaluated.

As shown in FIG. 1, the fading simulator according to the present embodiment has a configuration in which noise for fading is added to a baseband signal so that a standard quadrature modulator can be used for everything from modulation of a carrier to addition of fading. It can be configured with a circuit. Although not shown, the first noise generation circuit 41 and the second noise generation circuit 42 are more appropriately configured by a configuration in which noise generated according to a predetermined program changes with time. It is possible to have a configuration that can simulate a fading state.

[0013]

As described above, the fading simulator for digital communication according to the present invention has a configuration in which noise for fading is added to the baseband signal, so that the standard quadrature modulator performs from the modulation of the carrier wave to the addition of fading. Since it can be configured with one circuit, there is an effect that the device can be downsized and the cost can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a conventional fading simulator of this type.

[Explanation of symbols]

 1 Pattern Generator 2 IQ Signal Generation Circuit 3 Signal Generator 4 Fading Simulator 5 Evaluator 41 First Noise Generation Circuit 42 Second Noise Generation Circuit 43 First Adder 44 Second Adder 45 Standard Quadrature Modulation Instrument 46 High frequency input terminal 47 High frequency output terminal 48,49 Baseband signal output terminal

Claims (3)

[Claims] 1. A first adder for adding a baseband modulation signal I for balanced modulation of a 0 ° phase carrier of a quadrature modulation system and an output of a first noise generation circuit, and a quadrature modulation system A second adder for adding the baseband modulation signal Q for the balanced modulation of the 90 ° phase carrier and the output of the second noise generation circuit, and the 0 ° phase carrier of the output of the signal generator. A standard quadrature modulator that balance-modulates with the output of the first adder and balance-modulates a 90-degree phase carrier of the output of the signal generator with the output of the second adder is provided. Fading simulator for digital communication. 2. The modulated signal I and the modulated signal Q are input to the output of a pattern generator that generates a predetermined bit pattern, and the input is converted into the signal I and the signal Q to output the IQ signal. The fading simulator for digital communication according to claim 1, wherein the fading simulator is configured to be inputted from a circuit. 3. The noise output generated by the first noise generating circuit and the second noise generating circuit is temporally changed according to a predetermined program, according to claim 1 or 2. A fading simulator for digital communication according to the item.