JPH0231523A - Distortion compensating system - Google Patents

Abstract

PURPOSE:To minimize the cross modulation noise of an amplifier by controlling the distortion production of a linearizer in response to the level and frequency of inputted transmitting waves and the number of input signal waves so that the linearizer can always be set to the optimum operating point. CONSTITUTION:Information inputted from an input terminal 6 for inputted transmitting wave information is compared with information previously stored in a control information storing section 4 at a linearizer controller 3 and, as a result, the operating point information of a linearizer 1 corresponding to a coincident combination is obtained. Then, the linearizer 1 is controlled so that the cross-modulated distortion characteristics of the linearizer 1 can go to the optimum. Since the adjustment of the distortion compensation related to the level and frequency is made possible by comparing those information with the information of actually sent waves when input waves can be specified, more optimum distortion compensation can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a distortion compensation method for reducing cross-modulation noise generated during common amplification of multiple waves in a radio transmission amplifier.

(Prior art) When multiple waves are commonly amplified by one amplifier, cross-modulation noise occurs due to the nonlinearity of the amplifier input characteristics, and especially as the saturated transmission output approaches, the cross-modulation noise increases and the signal-to-noise The ratio (S/N) deteriorates. For this reason, as one measure to improve this problem, a distortion type linearizer that compensates for the nonlinearity of the amplifier is often used.

However, if the number of transmitted waves or the transmitted output per wave changes, the total transmitted output will vary greatly. The operating point of the linearizer is not necessarily optimal with respect to changes in , and cross-modulation noise cannot always be minimized.

As a countermeasure to this problem, conventional methods include changing the operating point of the linearizer depending on the overall transmission output level, but the cross-modulation distortion generated in the amplifier is caused by a large power amplifier.

The input/output characteristics of linearizers also differ depending on the frequency, and also change depending on the number of transmitted waves and the frequency of the transmitted waves.

f in the input/output characteristics of the illustrated linearizer in FIG. t
f1# f, indicates each frequency of the input signal wave within the frequency range of the amplifier used, and Fig. 3 shows an example of the input/output characteristics of a high power amplifier, where f, , f + f2 is Same as Figure 2. As can be seen from this figure, in the case of a wireless communication system in which the transmitted wave changes from moment to moment, cross-modulation distortion cannot be adjusted to the optimum level at all times, and the performance of the linearizer cannot be fully utilized.

(Objective of the Invention) The object of the present invention is to control the amount of distortion generated in the linearizer in accordance with the level and frequency of input transmission waves, and the number of input signal waves, so as to always set the linearizer at the optimum operating point. The objective is to minimize the cross-modulation noise of the amplifier.

(Structure of the Invention) (Characteristics of the Invention and Differences from the Prior Art) The present invention detects the level, frequency, and wave number of the input signal to the amplifier, and uses this information to adjust the linearizer to optimal operation. It is characterized by controlling. This method differs from the conventional technology in that the linearizer is controlled not only in response to the level of the input signal to the amplifier, but also in response to the frequency and wave number.

(Embodiment) FIG. 1 is a block diagram of an embodiment of a device for implementing the method of the present invention, in which a linearizer 1, a high power amplifier 2,
It is composed of a linearizer controller 3, a control information storage device 4, and the like.

The amount and phase of distortion of the signal applied to the signal input terminal 5 is controlled by a control signal given via the linearizer controller 3 in the linearizer 1, and the distortion amount and phase are controlled to improve the cross-modulation distortion generated in the high power amplifier 2. This output signal is amplified to the required level by the high power amplifier 2,
The signal is sent from antenna 7 to the satellite.

On the other hand, the input transmission wave information input terminal 6 of the linearizer controller 3 receives information obtained by detecting the level and frequency of the transmission wave input to the large power amplifier 2 using a modulator or the like.

In addition, the control information storage 4 stores in advance information on the level and frequency of all input transmitted waves and possible combinations of these input waves, as well as the input/output characteristics of the high power amplifier as shown in Fig. 3 and the combinations thereof. The amount of cross-modulation distortion and the operating point information of the linearizer that best improves the cross-modulation distortion generated in the high power amplifier at that time, which is determined from the input/output characteristics of the linearizer as shown in FIG. 2, are stored.

With such a configuration, the information input from the input transmission wave information input terminal 6 is compared with the information stored in advance in the control information storage device 4 in the linearizer controller 3, and as a result, a matching combination is matched. The operating point information of the linearizer 1 is obtained, and the linearizer is controlled accordingly so that the intermodulation distortion characteristics are optimized.

As is clear from this result, compared to the conventional technology, it has become possible to adjust the linearizer even depending on the difference in the level and frequency of each transmitted wave.

In the above description of the embodiment, a method used in a high-power amplifier for satellite communication has been described, but similar effects can be obtained when used in other wireless communication amplifiers that perform common amplification.

(Effects of the Invention) As explained above, in the case where the input wave can be specified, the present invention makes it possible to adjust the distortion compensation regarding the level and frequency by comparing that information with the information of the actually transmitted wave. Therefore, there is an advantage that more optimal distortion compensation can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a device for carrying out the method of the present invention, FIG. 2 is an example of input/output characteristics of a linearizer, and FIG. 3 is an example of input/output characteristics of a high power amplifier. 1...Linearizer, 2...High power amplifier,
3... Linearizer controller. 4... Control information storage device, 5... Signal input terminal,
6...Input transmission wave information input terminal, 7...Antenna. Patent applicant: Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] In an amplifier that commonly amplifies multiple signal waves with different carrier frequencies, by detecting the level, frequency, and number of input signal waves and selecting an operation pattern based on pre-stored linearizer and amplifier operation information. A distortion compensation method characterized by controlling the operating point of the linearizer in real time.