JP3452865B2 - Transmission power amplifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a W-CDMA (wide band or wide band CDMA: Code Division Multiple Access) system which is being put into practical use as a radio access system for a third generation (next generation) mobile communication system. More particularly, the present invention relates to a transmission power amplification device for a base station and a repeater in a mobile communication system, and a transmission power amplification device that combines a linear power amplification system of a single RF channel or a plurality of RF channels to form a high output power amplifier.

[0002]

2. Description of the Related Art TDMA of a narrow band digital modulation system in a currently operating second generation mobile communication system.
The wireless access method such as the one uses the narrow band modulation / demodulation technology, and the basic spectrum of the input modulated wave is maintained as the transmission power amplifying device of the base station and the repeater (or the repeater amplifier) that commonly amplifies the multi-frequency signal. However, a linear amplifier configured to suppress the deterioration of transmission quality and the adjacent channel leakage power below a required value is used.

Various distortion compensation techniques are applied to the transmission power amplifier for amplifying the narrow band multi-frequency signal. For example, a power amplifier using a distortion compensation technique such as a predistortion method or a feedforward method is widely used, and in particular, a PDC is used as a linear amplification method for commonly amplifying multiple frequencies.
(Personal Digital Cellular) (Japan) and ADC (US) Digital cellular base stations and excellent performance as a repeater transmission amplifier.

FIG. 5 is a block diagram showing an example of a predistortion linear amplifier, which is a configuration example in which a predistorter 11 is provided in the preceding stage of the quasi-linear amplifier 12 to cancel the third-order distortion. This system has a simple system, and has been devised so that the non-linear characteristics of the predistorter 11 and the quasi-linear amplifier 12 are matched well. The quasi-linear amplifier is an amplifier that is an input / output linear (linear) amplifier for a small amplitude signal, but has a distortion characteristic due to a non-linear characteristic exceeding a permissible value for a large amplitude signal. For example, an amplifier that performs a class B operation or a class AB operation depending on a bias set point in the input / output characteristics of the amplifier, and has a certain margin (back-off) with respect to the saturation output level, but when amplifying a multi-frequency signal It is necessary to suppress the output distortion below the allowable value.

FIG. 6 is a block diagram showing an example of a feed-forward linear amplifier, which is a directional coupler (D).
C) Distortion (error) is detected in the loop of the main power amplifier 14 and the delay line 15 between 13 and 16, and the directional couplers 16 and 19 are detected.
The error amplifier 17 and the delay line 18 between the loops are configured to remove the error. This method also has a vector adjustment circuit (not shown) and the like added, and although it has a complicated circuit configuration, it can compensate for all distortions other than signals, and achieves optimum operating point adjustment and stabilization. There is.

In the conventional repeater using the distortion compensating amplifier as described above, an IF conversion type repeater for converting a received wave into an intermediate frequency (IF) and selectively amplifying it, or a received wave to another frequency. There is a different frequency conversion type repeater for converting, amplifying and transmitting, or a booster repeater for repeating at the same frequency. These repeaters are installed in blind areas due to terrain and shadows of buildings, underground buildings, buildings, and tunnels, and miniaturization and low power consumption are always issues.

The radio characteristic specifications of the transmitting / receiving section of the base station apparatus arranged in each cell of the wideband CDMA system, which is currently undergoing a system experiment as a third generation mobile communication system, are, for example, a transmitting / receiving frequency of 2 GHz band and a 20 MHz band To 4
The carriers (RF channels) are arranged, and the carrier frequency interval ΔF is 5 MHz. The pass band width (B) of each RF carrier is approximately 4 MHz, and the occupied frequency band width (A) is slightly narrower than that. Then, the transmission output is set corresponding to the service of the system, for example, 20
W / carrier (or RF channel) or the like. And
The number of RF carriers of the transmitter / receiver actually mounted in the base station device is expected to be 3 to 4 carriers in the large scale base station and 1 to 2 carriers in the small scale base station. Also, a repeater arranged in a dead zone such as an underground mall or a tunnel is one carrier.

As described above, the distortion compensating power amplifier used in the base station and repeater of the current narrow band digital cellular is added with various functions for exhibiting stability and distortion suppression characteristics. . Therefore, when the above distortion compensation power amplifier is used as a transmission power amplifier for a relatively large power of the W-CDMA base station and the repeater of the third generation communication system, the scale of hardware expands, and the size increases. ，
There are problems in volume and power consumption.

That is, when a class AB operation quasi-linear amplifier having small third-order distortion, relatively good linearity, and excellent power efficiency is used as the main power amplifier of the W-CDMA system, it is 30 to 50 W or more. In order to obtain a high output, a configuration in which these quasi-linear amplifiers are connected in cascade is considered, and in order to maintain the linearity and obtain the required output, the final stage configuration is a parallel connection or push-pull. A configuration by connection and a configuration by combining them are conceivable.

[0010]

However, a transmission power amplification apparatus in which such quasi-linear amplifiers are cascade-connected and composite-synthesized is generally complicated because the distortion components generated in each stage are output comprehensively. There is a problem that it exhibits non-linear characteristics.
For example, there are drawbacks such that the input / output characteristics of the third-order intermodulation distortion (hereinafter referred to as IM3) component do not show the third-order slope, and the frequency dependence of the non-linear characteristics becomes remarkable.

Further, as a high output transmission power amplifier, a class AB operation quasi-linear power amplifier (hereinafter referred to as LP) having relatively high efficiency is used.
(Also referred to as “A”), an appropriate back-off margin is required from the viewpoint of securing a desired value of the distortion characteristic,
Overall power efficiency, that is, additional efficiency (hereinafter PAE: Power Ad
There is a problem that ded efficiency will decrease and power consumption will increase significantly.

Further, C which is wide band digitally modulated by using the above-mentioned narrow band digital multi-frequency common amplifier is used.
In the case of amplifying a DMA wave, leakage power to adjacent carriers, that is, adjacent channel leakage power (ACP: Adjacent C)
hannel Power (hereinafter referred to as ACP) below the required value,
For example, in order to suppress it to −50 dBc or less, it is necessary to consider the distortion compensation function, that is, the power consumption of the distortion compensation amplifier and the like. Therefore, PAE of LPA synthesis is the main power quasi-LP
There is a problem that the value is further lowered than the value of A, the power consumption is inevitably increased, and the heat dissipation radiator is also increased in size. As an example, the total efficiency of the 800 MHz band PDC system is currently about 10%.

As described above, for the base station facility and the repeater of the W-CDMA system, the LPA using the wideband digital modulation wave as input has high efficiency, low power consumption, small size, and low cost. It is a big issue.

It is an object of the present invention to amplify wideband digitally modulated CDMA waves with high efficiency and high power, reduce power consumption, reduce adjacent channel leakage power to a required value or less, and reduce power consumption. , To provide a compact, low-priced transmission power amplifier.

[0015]

The transmission power amplification device of the present invention has an RF carrier based on a main power amplifier system (a multistage structure of quasi-linear amplifiers) such as class AB or class B which operates with relatively high efficiency. Each RF carrier is connected to a filter that limits the occupied frequency band.

The value of the adjacent channel leakage power (ACP) that drops into the adjacent channel fluctuates greatly in inverse proportion to the power consumption due to the operation class of the amplifier, and the main power amplifier system alone generally satisfies the required standard of the system. Is difficult. Further, in order to reduce the ACP, an amplifier in which the saturation output level is increased and the output backoff margin is sufficient, the power efficiency is significantly reduced and the power consumption is large. Therefore, in the present invention, by using a quasi-linear amplifier such as class AB or class B as the main power amplifier system amplifier, the PAE is dramatically increased and the power consumption is significantly reduced.

Class AB and class B amplifiers have low power consumption and high PAE, but when a wide-range digitally modulated signal such as a spread spectrum modulation signal is input, the adjacent channel leakage power and the next adjacent channel leakage power are Since the distortion characteristics cannot meet the required standard of the system,
The leakage power to adjacent carriers is sufficiently attenuated by the filter of the filter combining unit whose attenuation characteristics are set so that the deterioration of the fundamental spectrum of the modulated wave can be contained within the allowable value, and sufficient band limitation is realized in the radio frequency band. .

Further, an isolator is arranged at the input end of each bandpass filter of the filter synthesizing unit, and residual distortion leakage noise of each RF carrier synthesized by the filter synthesizing unit flows back to the power amplifier of another RF carrier and interferes. Is trying not to occur.

As described above, the transmission power amplifying apparatus of the present invention has a quasi-linear main power amplifier system which operates with high efficiency for each carrier , an isolator and a radio frequency (R
The linear power amplifier is characterized in that a filter for limiting the band is provided in F), and the outputs thereof are used alone or combined to output.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The basic configuration of a transmission power amplifying apparatus for a base station according to the present invention is a modulator for wideband digitally modulating a single RF carrier, and a quasi-linear main power amplifier for amplifying its output with high power. A band-pass filter having a band limiting function for RF carriers is connected in cascade. In the case of a repeater, a single RF carrier is provided with a frequency converter that converts the RF carrier frequency instead of the digital modulator.

The apparatus for the base station will be described below.
A specific configuration of a transmission power amplification apparatus for a base station of the present invention is, for each of a plurality of RF carriers, a wideband digital modulator, a quasi-linear main power amplifier that amplifies a digitally modulated transmission signal, and an isolator. , A band-pass filter having a band limiting function is connected in series and the outputs thereof are combined.

The quasi-linear main power amplifier is a high-efficiency amplifier having the required modulation accuracy of a base station linear amplifier operating at an operating point near class AB or class B. The filter combining unit is configured to combine the outputs of a plurality (n) of band limiting filters, and the transmission characteristic of each filter has a pass band width that allows 99% or more of the energy of the digitally modulated spread modulated wave to pass. is doing. Therefore, the attenuation amount for the adjacent RF carriers has an attenuation characteristic for obtaining an attenuation of about 20 dB with respect to the edge of the pass band width of the adjacent carrier.

The isolator arranged on the input side of the bandpass filter prevents the carrier of the filter combined output from flowing back to another band with respect to the main power amplifier of each of the plurality of carriers. The output of each band-pass filter corresponding to each carrier is combined and output via direct coupling or a transmission line having an appropriate electrical length.

FIG. 1 is a block diagram showing the basic configuration of a base station device for a single RF carrier according to the present invention. In the figure, 1 is a wideband digital modulator, 2 is a quasi-linear power amplifier, and 4 is a bandpass filter that limits the band of an RF signal. This characteristic will be described later.

FIG. 2 is a block diagram showing an embodiment of a multi-carrier base station apparatus of the present invention. In the figure, 1-
1 to 1-n are digital modulators corresponding to the RF channels CH1 to CHn. 2-1 to 2-n are quasi-linear power amplifiers corresponding to each CH. 3-1 to 3-n, 4-1 to 4-
n is an isolator (ISO1 to ISO
n) and filters (F1 to Fn). 5-1-5
n is a direct coupling line for synthesizing the outputs of the filters F1 to Fn or a coupling line having an appropriate electrical length, and the transmitters (1) to (n) and the filter synthesizing unit constitute a wireless transmitter. .

FIG. 3 shows an outline of the filter characteristics of the band filter for limiting the RF band in the case of the two RF carriers of the present invention. B is the pass bandwidth, and A is the occupied frequency bandwidth. Approximately 20 dB at the edge of pass band width B of the adjacent carrier
Shows the attenuation amount of. With this characteristic, for example, 99% or more of the energy of the spread-modulated transmission signal can be passed and the adjacent channel leakage power can be suppressed to a desired value.

FIG. 4 shows an embodiment in which the present invention is applied to a repeater, and 20 is an input carrier (wideband modulated wave) F1.
Is a frequency converter for converting to another carrier, for example, F3. The quasi-linear power amplifier 2 according to the invention, the bandpass filter 4 and the connection 5 are the same as in FIG.

[0028]

As described in detail above, by implementing the present invention, the required modulation accuracy of the transmission power amplifying units of the base station and the repeater in the W-CDMA third generation mobile communication system is satisfied. In addition, the required values of the adjacent channel leakage power and the next adjacent channel leakage power can be satisfied, the overall power efficiency can be increased, and the low power consumption can be realized. The power saving of the base station and the repeater, the radiator (heat radiation) This has an extremely large effect on space saving by reducing the size of the container.

The specific total power efficiency according to the application of the present invention is 800 to 900 M while operating in the 2 GHz band.
Compared with the common amplification method used in the second-generation narrow-band cellular method of the Hz band, it is approximately twice or more, and the practical effect is extremely large. Further, when the W-CDMA system is put to practical use, it is expected that the cell radius will be small and the number of distributed base stations and repeaters will be extremely large. In that case, the effect of miniaturization and cost reduction according to the present invention will be obtained. Is big.

It is expected that the number of RF carriers will often be 1 to 2 in a small-scale local base station, and in this case, the effect of the present invention is particularly great. The effect is also great in the case of a single carrier repeater.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

FIG. 3 is a diagram showing an example of filter characteristics of the filter of the present invention.

FIG. 4 is a block diagram showing an embodiment in which the present invention is used in a repeater.

FIG. 5 is a block diagram of a conventional predistortion linear amplifier.

FIG. 6 is a block diagram of a conventional feedforward linear amplifier.

[Explanation of symbols]

1,1-1 to 1-n Digital modulator 2,2-1 to 2-n Quasi-linear power amplifier 3-1 to 3-n isolator (ISO) 4,4-1 to 4-n band limiting filter 5,5-1 to 5-n bond line 11 predistorter 12 Quasi-linear amplifier 13,16,19 Directional coupler (DC) 14 Main power amplifier 15,18 delay line 17 Error amplifier 20 frequency converter

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Takano Tsurunumadai, Tenno, Tenno-cho, Minami-Akita-gun, Akita Prefecture 43-224 Kokusai Electric Engineering Co., Ltd. (56) Reference JP-A-7-193443 (JP, A) ) Actual Development Sho 52-130634 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H03F 1/00-3/72 H04B 1/04

Claims (5)

(57) [Claims] 1. A transmission power which is provided in a base station in a wideband CDMA mobile communication system, and digitally modulates and high-power-amplifies one of a plurality of RF carriers frequency-allocated at a predetermined frequency interval and sends out the power. An amplifier device comprising a digital modulator for performing wideband digital modulation on any one of the plurality of RF carriers and a class AB or class B power amplifier with low power consumption and slightly low linear characteristics in multiple stages. A quasi-linear power amplifier that is cascade-connected to amplify the output of the digital modulator to a predetermined high power, and a quasi-linear power amplifier that is cascade-connected to the output side of the quasi-linear power amplifier and has an adjacent R
That a band filter F channel digital modulated RF carrier has an effective attenuation of about 20dB at the end of the pass band width is passed through the energy of more than 99% by band limitation to output with al the A characteristic transmission power amplifier. 2. To relay and amplify a plurality of carriers used in a wideband CDMA mobile communication system.
Of a transmission power amplifier provided in a repeater of any of the input RF carriers subjected to wideband digital modulation
A frequency converter that frequency-converts one of the carriers into another carrier and power amplifiers of class AB or class B that have low power consumption and slightly low linear characteristics are cascaded in multiple stages to convert the carrier converted by the frequency converter. A quasi-linear power amplifier that amplifies a predetermined high power, and a quasi-linear power amplifier that is cascade-connected to the output side of the quasi-linear power amplifier and that has an effective attenuation amount of about 20 dB at the end of the pass bandwidth of an adjacent RF channel. transmission power amplifier apparatus characterized by a bandpass filter with al the you are band-limited by passing the energy of more than 99% of carrier and outputs a. 3. A transmission power amplifier provided in a base station in a wideband CDMA mobile communication system, which digitally modulates a plurality of RF carriers, which are frequency-allocated at predetermined frequency intervals, amplifies and outputs the high power. A plurality of digital modulators for respectively performing wideband digital modulation on the plurality of RF carriers, and class AB or class B power amplifiers with low power consumption and slightly low linear characteristics are cascaded in multiple stages, and the plurality of digital modulators. Of a plurality of quasi-linear power amplifiers for amplifying the output of each of them by a predetermined high power , and
A plurality of bands that are cascade-connected to the output side and have an effective attenuation amount of about 20 dB at the end of the pass band width of adjacent RF carriers and limit the band of the digitally modulated RF carrier to pass 99% or more of the energy to output. filter and, said plurality of transmission power amplifier apparatus characterized by synthesizing means for transmitting output forms if the output of the bandpass filter is provided et the of. 4. An isolator is provided between each of the plurality of quasi-linear power amplifiers and each of the plurality of bandpass filters,
According to claim 3, characterized in that to suppress unwanted signals flow back into the quasi-linear power amplifier of one another other RF channel from the output combining means of said band-pass filter remembering isolation characteristics between each RF channel amplification system Transmission power amplifier. 5. The transmission power amplification device according to claim 3, wherein the number of RF carriers to be modulated and amplified is two or more.