KR20030018985A - IMD eliminating equipment of the terminal system - Google Patents

Abstract

PURPOSE: A device for removing IMD(InterModulation Distortion) of a terminal system is provided to distribute a plurality of RF(Radio Frequency) output signals, remove an original RF output from the distributed RF output signals in one side, and perform phase inversion for integration with RF output signals in the other side, so as to appropriately remove IMD included in outputted RF signals. CONSTITUTION: A distributor(1) distributes a plurality of digital RF signals. The first and second output amplifiers(2,3) perform power amplification for each RF signal distributed from the distributor(1). The first isolator(4) transmits RF signals including IMD signals amplified by the output amplifiers(2,3) in a single direction. A variable band limit filter(5) removes only normal main carrier signals among the RF signals including IMD signals distributed from the distributor(1). A phase transition unit(6) performs phase transition to 180 degrees for output signals inputted from the variable band limit filter(5). The second isolator(7) transmits IMD signals outputted from the phase transition unit(6) in a single direction. A coupler(8) combines signals respectively inputted from the first and second isolators(4,7) to offset IMD, and outputs only pure output frequency signals. And an MSM(Mobile Station Modem)(9) adjusts gains of the output amplifiers(2,3) according to PIN(Positive Intrinsic Negative).

Description

IMD eliminating device of terminal system

The present invention relates to an IMD removal apparatus of a terminal system, and in particular, an original high frequency output is removed from a signal of one side among a plurality of high frequency output signals, and then phase inverted and integrated with the high frequency output signal of the other side to include an eye included in the output high frequency signal. The present invention relates to an IMD removal apparatus of a terminal system for removing an MD.

In general, mobile communication systems have been rapidly developed as the industrial society has spread rapidly. Especially in the early 1980s, in North America, the service area was divided into hexagonal cells of several km to several ten kilometers in diameter, and then in the geographically separated cells. The mobile communication system has grown rapidly by using a cellular mobile communication system that uses the same frequency channel repeatedly and implements a radio channel switching function between cells as the subscriber moves.

However, these mobile communication systems typically use FDMA, TDMA, and CDMA as their access methods. Among them, the CDMA method modulates a transmission signal by assigning different codes with low correlation to each subscriber, Demodulation is performed with the same code. A terminal system using such a CDMA system usually includes an RF device unit to transmit a high frequency call signal to form a call with another CDMA terminal.

Then, referring to the conventional terminal system as described above with reference to FIG. 1, the codec unit 71 for digital signal processing of the audio signal input and output through the handset 70, and the digital voice input through the codec unit 71 A channel vocoder 72 for compressing and outputting a signal at a predetermined ratio, and a digital modulator for modulating and outputting a digital voice signal input from the channel vocoder 72 into a plurality of digital modulated signals, for example, I and Q digital modulated signals. 73, a frequency synthesizer 74 for frequency synthesizing the digital modulated signal output from the digital modulator 73 into an RF signal, and a linear power amplifier 75 for power amplifying the RF signal output from the frequency synthesizer 74. And a band pass filter 77 for band-filtering the RF signal power-amplified by the linear power amplifier 75 to the outside through the antenna 76.

On the other hand, referring to the operation of the conventional terminal system as described above, first, the phone number is transmitted through the base station (not shown), when the call is formed, the sender to transmit the necessary voice through the handset 70 of his terminal system 78 In this case, the voice of the sender is input to the codec unit 71 of the corresponding terminal system 78. Then, the codec unit 71 converts a voice signal of the user input through the handset 70 into a voice signal processing, for example, an analog voice signal into a digital signal and inputs it to the channel vocoder 72. The channel vocoder 72 compresses the digital audio signal input through the codec unit 71 at a predetermined ratio and outputs the digital voice signal to the digital modulator 73. In addition, the digital modulator 73 modulates the digital voice signal input from the channel vocoder 72 into a plurality of digital RF signals, for example, I and Q digital RF modulated signals, and outputs them to the distribution unit 74.

Then, the frequency synthesizer 74 synthesizes the I and Q digital modulated signals output from the digital modulator 73 to the RF signal and outputs them to the linear power amplifier 75. At this time, the linear power amplifier 75 amplifies the RF signal output from the frequency synthesizer 74 and outputs the band filter 77, respectively. Accordingly, each of the band filters 77 performs band pass filtering on the RF signal power amplified by the linear power amplifier 75 and emits them to the outside through the antenna 76 to perform a normal RF call processing operation.

Herein, when the input signal [x (t)] is expressed by Equation [1],

The output signal y (t) is expressed by equation [2].

However, in the conventional terminal system as described above, in addition to the RF signal, an intermodulation distortion frequency signal (IMD) other than the RF signal, as shown in Equation [2] in the process of power amplifying the RF signal by the linear amplifier 75.

For example, {omega} _ {1}, {omega} _ {2}, 2 {omega} _ {1}, 2 {omega} _ {2}, 2 {omega} _ {1}-{omega} _ { Harmonic components such as 2}, 2 {omega} _ {2}-{omega} _ {1} are also amplified and output, so that the IMD signal causes an error in signal transmission. Even if the gain control circuit of the linear amplifier is separately provided, the gain control circuit has a problem of increasing the manufacturing cost of the terminal system because the gain control circuit is composed of complicated and expensive components.

Accordingly, the present invention has been invented to solve the conventional problems as described above, by distributing a plurality of high frequency output signals, removing the original high frequency output signal from one of the divided high frequency output signals, and then inverting the phase to invert the high frequency output signal of the other side. By integrating, it eliminates the IMD included in the output high frequency signal, and thus has an object to provide an IMD removal device of the terminal system to improve the call quality of the terminal system accordingly.

Another object of the present invention is to adjust the gain of the low-noise amplifier that can adjust the gain according to the gain characteristics database of the MSM, there is no need for a separate gain control circuit, thereby eliminating the IMD of the terminal system, which significantly reduces the manufacturing cost of the terminal system. Relates to a device.

The present invention for achieving the above object is a communication terminal system for processing a call signal through the RF signal, a distribution unit for distributing the plurality of digital RF signals, and each of the RF frequency signal distributed from the distribution unit A first isolator for transmitting power amplifying the first and second output amplifiers, the RF frequency signal including the IMD signal amplified by the first output amplifier in a single direction, and the IMD signal distributed from the distribution unit. A variable band limiting filter for removing only a normal main carrier signal from the received RF frequency signal, a phase shifter for inverting the phase of the output signal inputted from the variable band limiting filter by 180 degrees, and an IMD signal output from the phase shifter The second isolator transmitting in the direction and the signals inputted from the first and second isolators respectively are synthesized to cancel the IMD. Provided is an IMD removal device of a terminal system including a combiner for outputting only a pure output frequency signal.

1 is an explanatory diagram illustrating an IMD removal apparatus of a conventional terminal system.

2 is an explanatory diagram illustrating an apparatus of the present invention.

3 (a) to 3 (c) are waveform explanatory diagrams illustrating a state in which an IMD is removed by the apparatus of the present invention.

<Detailed Description of Codes>

1: Distribution Unit 2: First Output Amplifier

3: second output amplifier 4: first isolator

5 variable band limiting filter 6 phase shifter

7: second isolator 8: combiner

9: MSM 10: Digital Modulator

11: channel vocoder 12: handset

13: codec

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 2, the present invention provides a distribution unit 1 for distributing a plurality of digital RF signals input thereto, and first and second power amplifiers for each of the RF frequency signals distributed from the distribution unit 1. A first isolator (4) for transmitting in one direction a second frequency amplifier (2, 3), an RF frequency signal including the IMD signals amplified by the first and second output amplifiers (2, 3), and A variable band limiting filter (5) for removing only a normal main carrier signal from an RF frequency signal including an IMD signal distributed from the distribution unit (1), and a phase of an output signal input from the variable band limiting filter (5) 180 A phase shifter 6 for inverting the road, a second isolator 7 for transmitting the IMD signal output from the phase shifter 6 in a single direction, and input from the first and second isolators 7, respectively. The synthesized signals to cancel the IMD and then the pure output frequency And only the coupler (8) to output call, the gain PIN (Positive intrinsic negative) of the output amplifiers (2, 3) In other words, MSM for controlling the gain in accordance with the signature database; include (Mobile station modem 9).

One end of the distribution unit 1 is connected to a digital modulator 10 for modulating and outputting a digital voice signal into a plurality of digital RF signals, for example, I and Q digital RF modulated signals, and the digital modulator 10. One end of the channel vocoder 11 is compressed to output the input digital voice signal at a predetermined ratio, and one end of the channel vocoder 11 receives a digital signal processing input and output through the handset 12. The codec unit 13 is connected.

In addition, one end of the combiner 8 is connected to the band filter 15 which band-filters the RF signal amplified by the combiner 8 and emits it to the outside through the antenna 14.

Here, another end of the digital modulator 10 is connected to a frequency synthesizer 16 for frequency synthesizing the digital modulated signal output from the digital modulator 10 into an RF signal.

Next, the operation and effects of the present invention as described above will be described.

In the present invention, when a phone number is transmitted and a call is made, the sender transmits necessary voice through the handset 12 of his terminal system 17, wherein the voice of the sender is a codec of the corresponding terminal system 17. It is input to the unit 13. Then, the codec unit 13 converts a voice signal of the user input through the handset 12 into a voice signal processing, for example, an analog voice signal into a digital signal and inputs it to the channel vocoder 11. The channel vocoder 11 compresses the digital audio signal input through the codec unit 13 at a predetermined ratio and outputs it to the digital modulator 10. In addition, the digital modulator 10 modulates the digital voice signal input from the channel vocoder 11 and outputs the digital modulated signal to the frequency synthesizer 16 as a digital modulated signal. The frequency synthesizer 16 synthesizes the digital modulated signal output from the digital modulator 10 into an RF signal and then outputs the frequency to the distribution unit 1.

Then, the distribution unit 1 distributes the RF signal output from the frequency synthesizer 16 to the first and second output amplifiers 3, respectively. Here, the RF signal input to the first output amplifier 2 is amplified by the first output amplifier 2 and output to the first isolator 4, the output signal of the first output amplifier 2 Among them, as shown in (a) of FIG. 3, the main carrier signals f1 and f2 and the IMD signal, that is, the harmonic signals 2f1-f2, 2f2-f1, f1-f2, and f1 + f2, are also included. Is output. Then, the first isolator 4 inputs the main carrier signal, that is, the RF signal including the IMD signals input from the first output amplifier 2, into the combiner 8.

At this time, the RF signal inputted to the second output amplifier 3 is also amplified by the second output amplifier 3 and outputted to the variable band limiting filter 5, the output of the second output amplifier 3 Among the output signals, as shown in (a) of FIG. 3, the main carrier signals f1 and f2 and the IMD signals, that is, the harmonic signals 2f1 to f2 and 2f2, are the same as the output signals of the first output amplifier 2. -f1, f1-f2, f1 + f2) are output together.

However, the variable band limiting filter 5 removes the main carrier signals f1 and f2 by band filtering the main carrier signals including the IMD signals input from the second output amplifier 3 and then removes the remaining IMD signals 2f1. Only -f2, 2f2-f1, f1-f2, f1 + f2) are output to the phase shifter 6 as shown in FIG. The phase shifter 6 then inverts the IMD signal input from the variable band limiting filter 5 by 180 degrees and outputs it to the second isolator 7. Then, the second isolator 7 inputs the inverted phase IMD signals from the phase shifter 6 to the combiner 8.

In this case, the combiner 8 synthesizes the RF signal including the IMD signal input from the first isolator 4 and the IMD signal in which the phase input from the second isolator 7 is inverted by 180 degrees. IMD signals 2f1-f2, 2f2-f1, f1-f2, f1 + f2 input from the first isolator 4 and IMD signals 2f1-f2, 2f2-f1, input from the second isolator 7; Since f1-f2 and f1 + f2 are 180 degrees out of phase, they are canceled with each other and only the main carrier signal, that is, the RF signal, remains and is output to the band pass filter 15 as shown in (c) of FIG. 3. The band pass filter 15 performs band pass filtering on the RF signal input from the combiner 8 and radiates the RF signal to the outside through the antenna 14 to perform a normal RF call processing operation.

In this process, the MSM 9 controls the gain of the first and second output amplifiers 3 through a PIN, that is, a gain characteristic database, wherein the MSM 9 is an amplifier (2, 3). The current gain is detected, the detected value is compared with the data of the gain characteristic database, and the optimum gain control signal is calculated. Since the MSM 9 adjusts the gains of the first and second output amplifiers 3 according to the calculated gain control signal, it is possible to perform optimum gain adjustment without the need for a separate gain control circuit. have.

As described above, the present invention distributes a plurality of high frequency output signals, removes the original high frequency output from the divided high frequency output signal, and then inverts the phase to integrate the high frequency output signal of the other side, thereby being included in the output high frequency signal. Eliminating the IMD has the advantage of improving the call quality of the terminal system accordingly.

In addition, according to the present invention, the gain of the low-noise amplifier that can adjust the gain is adjusted according to the gain characteristic database of the MSM, so that a separate gain control circuit is not required, thereby reducing the manufacturing cost of the terminal system.

Claims (2)

In the communication terminal system for processing a call signal through the RF signal, A distribution unit for distributing the plurality of digital RF signals, first and second output amplifiers for amplifying each of the RF frequency signals distributed from the distribution unit, and an IMD signal amplified by the first output amplifier; A first isolator for transmitting a single RF frequency signal in a single direction, a variable band limiting filter for removing only a normal main carrier signal from an RF frequency signal including an IMD signal distributed from the distribution unit, and an input from the variable band limiting filter A phase shifter for inverting the phase of the output signal by 180 degrees, a second isolator for transmitting the IMD signal output from the phase shifter in a single direction, and a signal input from the first and second isolators, respectively, to synthesize IMD; IMD of the terminal system, characterized in that it comprises a coupler for canceling and outputting only the pure output frequency signal Device. 2. The apparatus of claim 1, wherein an MSM for controlling the gain of the output amplifiers is connected to one end of the output amplifier according to a gain characteristic database.