JP2723607B2 - Transmission device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission device for performing narrowband transmission in mobile communication such as a car telephone.

2. Description of the Related Art FIG. 2 shows a configuration of a conventional transmitting apparatus for performing narrowband transmission by amplitude / phase modulation.

In FIG. 2, when digital data is input from a terminal 16, a baseband (BB) generator 17 generates an appropriately band-limited baseband signal by weighting the basic pulse with the input data sequence. Then, an amplitude and phase modulator (MOD) 18 modulates a carrier with the baseband signal to generate a modulated wave. This operation is equivalent to translating the spectrum of the baseband signal on the frequency axis.

The modulated wave generated by the amplitude / phase modulator 18 is amplified by the linear amplifier 19 without distortion and transmitted.

Therefore, according to the above conventional example, the amplitude / phase modulator 18
By amplifying the modulated wave generated by the above with the linear amplifier 19, narrow band transmission can be performed.

SUMMARY OF THE INVENTION However, in the above-described conventional transmitting apparatus, since the modulated wave is amplified by the linear amplifier 19, the linear amplifier 19 generally has low power efficiency and shortens the life of the mobile station battery. There is a problem.

The present invention has been made in consideration of the above-described conventional problems, and has as its object to provide a transmission device capable of performing narrowband transmission even with an amplifier having high power efficiency and nonlinear distortion.

Means for Solving the Problems In order to achieve the above object, the present invention considers that an output signal of an amplifier having nonlinear distortion is represented by an n-th order polynomial of an input signal, and therefore, an input signal of the amplifier having nonlinear distortion is Distortion is performed in advance according to the n-th order polynomial to obtain a linear characteristic as a whole.

According to the present invention, each coefficient of the n-th order polynomial is adaptively controlled so that a result of demodulating an output signal of an amplifier having nonlinear distortion coincides with a baseband signal.

According to the present invention, an input signal of an amplifier having high power efficiency and having nonlinear distortion is obtained by previously distorting an input signal of an amplifier having non-linear distortion, so that narrow-band transmission can be performed.

According to the present invention, since the coefficients of the polynomial are updated, there is an effect that the characteristics do not deteriorate due to variations of each circuit element, temperature change, and aging.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of a transmission device according to the present invention.

In Figure 1, 1 is an input terminal of the digital data, 2, by weighting the basic pulse in data string input from the terminal 1, suitably bandlimited baseband signals x _j baseband for generating ( B · B) generator, 3, the baseband signal x _j from the baseband generator 2, a plurality (= n) pieces of exponential value x _j, x _j ^2, ... x
A power signal generator 4 for generating _j ⁿ by a multiplier or a DSP (digital signal processor) is a shift register for loading a plurality of power values from the power signal generator 3.

Reference numeral 5 denotes a shift register in which coefficients c ₁ ^(j) , c ₂ ^(j) ,..., C _n ^(j) are stored in advance, and 6 denotes the power value loaded in the shift register 4 and stored in the shift register 5. has been subjected to product sum calculation of the coefficients, sum-of-products arithmetic unit for outputting a signal y _j which is added distortion, 7 converts the output y _j of the sum-of-products arithmetic unit 6 to an analog signal (baseband signal) D / A converter, 8
Is an amplitude / phase modulator (MOD) for converting an output signal of the D / A converter 7 into a modulated signal, and 9 amplifies the modulated signal from the amplitude / phase modulator 8 and outputs the amplified signal via a terminal 10. The amplifier 9 has high power efficiency but has nonlinear distortion.

11 is an attenuator for attenuating the modulated signal amplified by the amplifier 10, 12 is a demodulator (DEM) for demodulating the modulated signal attenuated by the attenuator 11 to a baseband signal, 13 is
A / D converter for converting the baseband signal into a digital signal _j which is demodulated by the demodulator 12, 14, a baseband signal x _j input via a delay unit 16 from the baseband generator 2, A / D A correction amount calculator 15 for calculating the correction amount of the coefficient stored in the shift register 5 based on the digital signal _j from the converter 13, and a correction amount calculator 15 for calculating the correction amount and the coefficient stored in the shift register 5. update the coefficients by adding the correction amount, an adder for storing the shift register 5, the delay device 16, the base from the baseband generator 2 band signals x _j and a / D converter 13 Digital signal _{j from}
Is corrected.

 Next, the operation of the above embodiment will be described.

In Figure 1, the baseband signal generator 2 generates a baseband signal _j, exponential value x _j is a power signal generator 3, x _j ^2, ... when loaded into the shift register 4 to generate the x _j ^n, The power value loaded into the shift register 4 and the coefficients c ₁ ^(j) , c ₂ ^(j) ,
.., C _n ^(j) are read out, and the product-sum operation unit 6 executes the following equation (1).

Where C _j = (c ₁ ^(j) , c ₂ ^(j) ,..., C _n ^(j) ) ^T , c ₁ ^(j) = 1 X _j = (x _j , x _j ² , ..., x _j ⁿ ) ^T Therefore, when this value is converted into an analog signal by the D / A converter 7, modulated by the amplitude / phase modulator 8 and amplified by the amplifier 9, the inverse characteristic of the distortion applied by the amplifier 9 is represented by a coefficient c _1. Since it is generated by the n-th order polynomial of ^(j) , c ₂ ^(j) ,..., c _n ^(j) , it is equivalent to the output signal of the conventional linear amplifier 19.

The output signal of the non-linear amplifier 9 includes an attenuator 11, a demodulator 12,
The original baseband signal _j is returned by the A / D converter 13 and the correction amount calculator 14 calculates the following equation (2). However, the second term on the right side of 0 <α <2, c ₁ ^(j) = c ₁ ^{(j + 1)} = 1 is calculated, and the coefficient C _j stored in the shift register 5 is added by the adder 15. , Is updated to the coefficient C _{j + 1} .

Therefore, since the coefficient _Cj stored in the shift register 5 is updated as needed, there is an effect that the characteristics do not deteriorate due to variations of each circuit element, temperature change, and aging.

In the above-described embodiment, the case where the amplitude and phase modulation is performed has been described. However, the present invention can be applied to the case where quadrature modulation is performed using two circuits.

As described above, in view of the fact that the output signal of the amplifier having the nonlinear distortion is expressed by the n-th order polynomial of the input signal, the present invention converts the input signal of the amplifier having the nonlinear distortion into the n-th order polynomial in advance. , And a linear characteristic as a whole is obtained, so that narrowband transmission can be performed at high speed using an amplifier having high power efficiency and nonlinear distortion.

The present invention also adaptively controls each coefficient of the n-th order polynomial so that the result of demodulating the output signal of the amplifier having the non-linear distortion coincides with the baseband signal. There is an effect that the characteristics do not deteriorate due to temperature change and aging.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a transmission device according to the present invention, and FIG. 2 is a block diagram showing a conventional transmission device. 2... Baseband signal (BB) generator, 3... Exponentiation signal generator, 4, 5... Shift register, 6... Product-sum operation unit, 7... D / A converter, 8. Amplitude and phase modulator, 9 ...
... amplifier, 11 attenuator, 12 demodulator, 13 A / D converter, 14 correction amount calculator, 15 adder.

Claims (2)

(57) [Claims] A baseband generating means for generating a baseband signal based on input data; a power signal generating means for generating a plurality of power values for the baseband signal output from the baseband signal; A correction amount calculation for calculating a correction amount of a coefficient stored in a shift register based on a baseband signal input from a generation unit via a delay unit and a digital signal obtained by demodulating and A / D converting the amplified modulated signal. Means for calculating the product sum of a plurality of power values output by the power signal generating means and the coefficient output by the correction amount calculating means, and outputting a distorted signal; D /
A transmitting apparatus comprising: a modulator for modulating an A-converted analog signal; and an amplifier for amplifying a modulated signal output from the modulator. 2. The method according to claim 1, wherein the difference between the baseband signal output from the baseband generator and the baseband signal obtained by demodulating the modulated signal amplified by the amplifier is zero. 2. The transmission device according to claim 1, wherein the coefficient is corrected.