JPH0662066A - Phase setting method for non-linear distortion compensating circuit - Google Patents

Abstract

PURPOSE:To correctly set the phase of an output carrier wave from a local oscillator to an orthogonal demodulator for compensating non-linear distortion even in the case of continuous transmission in which there is no lamp bit in the case of burst transmission. CONSTITUTION:This method is provided with a monitor 1 for monitoring the levels of signals I and Q in two analog systems inputted to an orthogonal modulator 50, and the monitor detects the state of turning the levels of both of analog signals of two systems inputted to the orthogonal modulator 50 to a level higher than a prescribed threshold value Vth. In such a state, phase difference is measured between the phases of outputs I' and Q' of an orthogonal demodulator 70 and the phase of the input of the orthogonal modulator, and the phase of the output of the orthogonal demodulator is set so as to eliminate the phase difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission circuit for power amplification of a quadrature phase modulated QPSK or other quadrature modulated wireless digital modulation signal for continuous transmission, and more particularly to a final stage of the transmission circuit. Non-linear distortion compensation that compensates for the non-linear distortion of the output of the high-output amplifier that performs non-linear amplification in order to improve the power efficiency in the baseband region of its modulation input and demodulation output, and linearizes the input / output characteristics of the high-output amplifier. To a phase setting method for a transmission circuit with a switch.

As a wireless digital modulation communication system, it is indispensable to use a quadrature modulation system such as QPSK from the viewpoint of effective utilization of radio frequency. At that time, linear high output without distortion is generated. However, when the final stage high output amplifier is operated in the linear region, the so-called power efficiency of the transmission power / power consumption ratio deteriorates, and the transmission device including the drive power source is downsized and fixed. It becomes difficult to increase the operating time of the power supply. Therefore, the high-output amplifier of the transmission circuit is operated in a non-linear region where power efficiency is high, and a distortion compensation circuit for compensating the non-linear distortion is provided to linearize the input / output characteristics of the entire transmission circuit. As a transmission circuit with non-linear distortion compensation in the case of continuous transmission, as in the case where the transmitted wave is a burst wave, the phase difference between the modulation input and demodulation output in the baseband region and the measured phase difference are measured. It is necessary that the phase setting circuit for linearization of the transmission circuit based on it be realized with a simple configuration.

[0003]

2. Description of the Related Art FIG. 4 shows a configuration example of a circuit for phase measurement and phase setting in a baseband region for a conventional burst mode Cartesian nonlinear distortion compensating circuit, and FIG. 5 shows the burst mode transmission. The timing of the phase setting in the circuit is shown. FIG. 6 is an explanatory view of the principle of the conventional phase difference measurement. Currently, development of TDMA digital mobile communication is in progress, but in order to suppress the spread of the spectrum when the mobile device sends out radio waves in a burst at a predetermined time, A so-called ramp bit is provided to moderate changes in the amplitude before and after the rise and fall (ramp time). As shown in FIG. 5, the ramp bit has a fixed value that gradually increases the amplitude of the transmission wave at the rising edge. Therefore, the timing at which the transmission wave becomes sufficiently large is set at a certain time of the ramp time. The phase difference is measured and the phase is set for distortion compensation at that timing.

As shown in FIG. 6, the measurement of the phase difference for distortion compensation is performed by using the two series of baseband signals I and Q at the input of the quadrature modulator MOD (50) shown in FIG. θ = tan
^-1 Q / I is calculated, and the phase of demodulated output θ '= tan
^{-1 Find} Q '/ I'. Then, the phase difference Δθ = θ−θ ′ between the modulation input and the demodulation output is obtained. And this phase difference Δθ
Local oscillator LO (9) to the output quadrature demodulator DEM (70).
The phase of the carrier wave of (0) is set by the infinite phase shifter EPS (80) so that the phase difference Δθ becomes zero. And the conventional phase measurement and phase control circuit EPS- in FIG.
CONT (130) is the baseband circuit MODBB (10) shown in the figure.
The two series of baseband signals I and Q to be input to the quadrature modulator MOD (50) through the A converter DAC (20), the low pass filter (30) and the distortion adder (40) are input and Thus, the input side phase θ = tan ^-1 Q / I, which is the reference for the phase difference measurement, is obtained. Next, the quadrature demodulator DEM (70) that demodulates the output Pout of the high-output amplifier HPA (60) that power-amplifies the output of the quadrature modulator MOD (50) in a non-linear region with high power efficiency by using a local carrier of quadrature phase At the output, the baseband signal I ', which returns to the input side of the modulator MOD (50),
Q'is converted by the AD converter ADC (120) and input to the phase measurement and phase control circuit EPS-CONT (130), and the output side phase θ '= tan ^-1 Q' / I 'as well as the input side. Ask for. Then, the phase difference Δθ = θ−θ ′ between the reference input phase θ and the output phase θ ′ is obtained, and the phase difference Δθ is calculated by the amount of the carrier wave of the output of the local oscillator LO (90) to the quadrature demodulator DEM (70). The phase difference Δθ is eliminated by increasing / decreasing the phase, but the phase increase / decrease is measured by the phase difference measurement and phase control circuit EPS-CONT (130) and external (not shown TDMA The phase setting control data generated by the burst signal from the control unit) is converted by the DA converter DAC (140) by the analog control signals X and Y, and the infinite phase shifter EPS ( 80) is controlled to control the phase so that the phase difference Δθ is eliminated.

[0005]

As described above, when the transmission wave output from the transmission circuit for amplifying and transmitting the quadrature-modulated signal with high output is a burst signal, the amplitude of the ramp time at the rising edge of the burst wave. , The phase difference Δθ is measured, and the infinite phase shifter EPS (80) sets the local oscillator LO (90) to the quadrature demodulator DEM (70) so that the phase difference becomes zero. ), The phase of the output carrier can be set, but if the transmitted wave is a continuous signal wave with no ramp time, there is no guarantee that the amplitude of the transmitted wave will be sufficiently large at the time of measuring the phase difference Δθ. There is a problem that the measurement error may increase.

An object of the present invention is to modulate and demodulate the transmission circuit when a transmission wave output from a high-output transmission circuit that non-linearly amplifies a quadrature phase modulation QPSK or other quadrature modulation signal is a continuous signal. The error of measurement of the phase difference in the output baseband does not become large, and the phase of the output carrier of the local oscillator LO (90) can be set to the quadrature demodulator DEM (70) to correctly compensate the generated nonlinear distortion. It is to realize a phase setting method in a non-linear distortion compensation circuit.

[0007]

The basic configuration of the present invention for achieving this object is, as shown in the principle diagram of FIG. 1, two series of analog baseband signals I at the input of the quadrature modulator MOD (50). , A state in which a monitor 1 for constantly monitoring the levels of Q is provided, and the levels of the two series of baseband signals I and Q input to the quadrature modulator MOD (50) are both higher than the threshold Vth by the monitor 1 ( Check the level "H" state together. In that state, control circuit EPS-CONT (130) for infinite phase shifter
, The phase θ of the two series of baseband signals I and Q input to the quadrature modulator MOD (50) and the phase of the two series of baseband signals I ′ and Q ′ output from the quadrature demodulator DEM (70) Phase difference from θ'Δθ
= θ−θ ′ and generate control signals X and Y that eliminate the measured phase difference Δθ, and use the infinite phase shifter EPS (80) to generate a local oscillator ( 90) Output carrier wave phase is set.

[0008]

In the present invention, the monitor 1 is the quadrature modulator MOD (50).
The levels of the two series of analog baseband signals I and Q at the input of are constantly monitored, and the two series of baseband signals I and Q are monitored.
The state in which both levels become larger than the threshold value Vth is detected. In this detection state, that is, in the state where both are at level "H", the phase of two series of baseband signals I and Q at the input of the quadrature modulator MOD (50) θ = tan ^-1 Q / I and the quadrature demodulator DEM Phase of two baseband signals I ', Q'of the output of (70) θ' = tan
^-1 Q '/ I' phase difference Δθ = θ−θ 'is measured by the control circuit EPS-CONT (130) of the infinite phase shifter first, then
The control signals X and Y are generated so as to eliminate the measured phase difference Δθ. Then, by the control signals X and Y, the infinite phase shifter E
The PS (80) is controlled to set the phase of the carrier wave of the output of the local oscillator (90) to the quadrature demodulator DEM (70).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS While keeping the principle diagram of FIG. 1 as it is, a configuration of a phase setting method in a non-linear distortion compensation circuit of an embodiment of the present invention is shown.
FIG. 2 is a time chart showing a process of obtaining a timing pulse for explaining the operation of the embodiment. In the configuration of the embodiment of FIG. 1, the monitor 1 of the present invention has two analog comparators 1-1 _1, 1-1 having a threshold value Vth of a certain level.
₂ and an AND circuit 1-2 that takes the logical product of the two outputs,
It is composed of a timing controller (Timing-cont) 1-3 which generates a timing pulse for phase control by the AND output. The operation will be described with reference to the time chart of FIG. 2. The analog comparators 1-1 _{1 and} 1-1 ₂ are quadrature modulators M.
The levels of (1) Ich and Qch, which are two series of analog baseband signals that are continuously input to OD (50), are constantly monitored.
The state "H" in which the levels of Ich and Qch have become larger than the threshold value Vth is detected, and (2) the detection output "H" is sent to the AND circuit 1-2. The AND circuit 1-2 detects the state "H" in which both the Ich and Qch levels are higher than the threshold value Vth, and outputs the AND output (3) I _AND Q
To the timing controller (Timing-cont) 1-3. Then, the timing controller 1-3 generates the necessary (4) timing pulse and outputs it to the control unit (EPS-CONT) of the infinite phase shifter.

FIG. 3 is a block diagram of a phase setting method in a non-linear distortion compensation circuit of another embodiment (corresponding to claim 2) of the present invention. In the embodiment of FIG. 3, the quadrature modulator MOD of FIG.
(50) input analog 2 series baseband signals I, Q
Instead of, the two series of digital D baseband signals before being converted to analog signal A by D / A converter DAC (20)
Incorporating I _D and Q _D into the digital comparator (Digital Comp) 1-1 _D that composes the monitor 1, compares them with reference data (Ref-Data) given in advance, and determines the matched signal to the timing controller. (Timing-cont) 1-3 is being sent to generate the required timing pulse. Since the comparator circuit constituting the monitor 1 is digitized, the embodiment shown in FIG. 3 is advantageous over the analog circuit shown in FIG. 1 in that the circuit scale can be reduced and no adjustment can be made.

[0011]

As described above, according to the present invention, even in the transmission circuit of the communication system in which the transmission wave is a continuous signal wave that is not a burst wave, the compensation circuit for the non-linear distortion generated by the non-linear operation high output amplifier is provided. It is possible to obtain an effect that the phase measurement in the base band region of 1 is performed with a small error and the phase can be set accurately.

[Brief description of drawings]

FIG. 1 is a principle diagram showing a basic configuration of a phase setting method in a nonlinear distortion compensation circuit of the present invention.

FIG. 2 is a time chart showing a process of obtaining a timing pulse for explaining the operation of the embodiment of the present invention.

FIG. 3 is a configuration diagram of an embodiment corresponding to claim 2 of the present invention.

FIG. 4 is a circuit example of phase measurement and phase setting in a conventional burst mode Cartesian type nonlinear distortion compensation circuit-equipped transmission circuit.

FIG. 5 is a diagram showing a phase setting timing in a conventional burst mode transmission circuit.

FIG. 6 is a diagram for explaining the principle of conventional phase difference measurement.

[Explanation of symbols]

1 is a monitor, 1-1 ₁ and 1-1 ₂ are two analog comparators, 1-2
Is an AND circuit, 1-3 is a timing controller (Timing-cont)
, 1 _D is a digital comparator, (10) is a modulation baseband circuit, (20) is a DA converter, (30) is a low pass filter, (40)
Is a distortion adder, (50) is a quadrature modulator MOD, (60) is a high-power transmission circuit, (70) is a quadrature demodulator DEM, (80) is an infinite phase shifter EPS,
(90) is a local oscillator, (100) is a subtractor, (110) is a loop switch, (120) is an AD converter, (130) is an infinite phase shifter control circuit EPS-CONT, and (140) is a DA converter. is there.

Claims (2)

[Claims] 1. A transmission circuit for amplifying and continuously transmitting a quadrature-modulated signal such as 4-phase PSK modulation, and a baseband circuit (2) for processing and outputting an input 2-series (I, Q) baseband digital signal. 10) and its output digital signal (I _D, Q _D ).
A DA converter (20) for converting the analog signal (A), a low-pass filter (30), a distortion adder (40), and a quadrature modulator (50) for quadrature modulating a local carrier with its output, A high output amplifier (60) that non-linearly amplifies the modulated output, a quadrature demodulator (70) that demodulates the output (Pout) with the local carrier, and an infinite phase shift that arbitrarily shifts the phase of the local carrier. (80), a local oscillator (90) for generating the local carrier, and the output of the quadrature demodulator
(I ', Q') distortion detector (100) to detect the distortion, the loop switch (11) that outputs the distortion compensation signal to the distortion adder (40)
0) the phase of the output (I ', Q') of the quadrature demodulator (70) of the transmission circuit with Cartesian distortion compensation circuit (θ ') and the input of the quadrature modulator (50) (I, Q ) And the phase (θ) of the phase difference (Δ
θ = θ'-θ) is measured and the phase of the output (I ', Q') of the quadrature demodulator (70) is set so that there is no phase difference. ) Input analog two-series signal (I, Q) level monitor (1) for monitoring the level of the input (2) analog signal (I) of the quadrature modulator (50). , Q) the level of both of which is higher than a predetermined threshold value (Vth) (H) is detected, the phase of the output (I ', Q') of the quadrature demodulator (70) and the quadrature Modulator
Measure the phase difference (Δθ) from the phase of the input (I, Q) of (50),
Output of the quadrature demodulator (70) so that there is no phase difference
A phase setting method in a non-linear distortion compensation circuit, characterized by setting the phase of (I ', Q'). 2. A monitor in the phase setting method (1)
But the DA converter (20) by two series of digital signal before being converted to an analog signal (A) (I _D, Q _D) to monitor, as compared to the previously given data (Ref.Data) 2. A phase setting method in a non-linear distortion compensating circuit according to claim 1, wherein the phase setting method is a digital comparator (1 _D ) for outputting a matched signal.