Power combiner, amplifier, and transmitter

This power combiner includes a first balun and a second balun. The first balun includes: a first line having a grounded end and an end connected to a positive input of a first differential input signal; a second line having a grounded end and an end connected to a negative input of the first differential input signal; a third line formed in parallel with the first line, the third line having an opened end corresponding to the grounded end of the first line and an end being different from the opened end; and a fourth line formed in parallel with the second line, the fourth line having a single-ended output end corresponding to the grounded end of the second line and an end connected to the end being different from the opened end of the third line. The second balun includes: a fifth line having a grounded end and an end connected to a positive input of a second differential input signal; a sixth line having a grounded end and an end connected to a negative input of the second differential input signal; a seventh line formed in parallel with the fifth line, the seventh line having an opened end corresponding to the grounded end of the fifth line and an end different from the opened end of the seventh line; and an eighth line formed in parallel with the sixth line, the eighth line having a single-ended output end corresponding to the grounded end of the sixth line and an end connected to the end different from the opened end of the seventh line.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2008-104097, filed on Apr. 11, 2008; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power combiner, an amplifier and a transmitter which are applicable to, for example, the power combining.

2. Description of the Related Art

In general, a radio transmitter has a Power Amplifier (PA) to send a signal with a predetermined power to antenna. In case that the large power is particularly necessary, a plurality of amplifier connected in parallel may be provided and each amplified output is combined to obtain the prescribed power, because there is a limitation in voltage amplitude in accordance with a characteristic of a amplifying device such as a transistor (for example, see the reference, “I. Aoki, et., al., “Fully Integrated CMOS Power Amplifier Design Using the Distributed Active-Transformer Architecture”, IEEE JSSC, Vol. 37, No. 3, March 2002, pp. 371-383.”; the entire contents of which are incorporated herein). The reference describes an example of the power amplifier having four differential amplifiers and four transformers for power combining.

In the power amplifier described in the reference, since all of the secondary terminals (the output terminals) of the transformers to combine the amplified outputs are connected in series, the series line length at the secondary terminals side is long. Therefore, a loss caused by the series resistance and the substrate resistance is large and the available frequency bandwidth is narrow. Namely, the loss at the power combiner is large, and as a result, there is a problem that the output power, the efficiency and the available frequency bandwidth of the power amplifier using the power combiner are degraded.

As stated above, in the conventional power combiner, amplifier and transmitter, there is a problem that the output power, the efficiency and the available frequency bandwidth of the power combiner, amplifier and transmitter are deteriorated. The present invention is made to solve the problem as stated above, and an object thereof is to realize a power combiner having low loss and wide available bandwidth characteristics as well as provide an amplifier and a transmitter having large power output, high efficiency and wide available bandwidth characteristics.

BRIEF SUMMARY OF THE INVENTION

To attain the above-stated object, a power combiner, an amplifier and a transmitter according to an aspect of the present invention includes a first balun and a second balun. The first balun includes: a first line having a grounded end and an end connected to a positive input of a first differential input signal; a second line having a grounded end and an end connected to a negative input of the first differential input signal; a third line formed in parallel with the first line, the third line having an opened end corresponding to the grounded end of the first line and an end being different from the opened end; and a fourth line formed in parallel with the second line, the fourth line having a single-ended output end corresponding to the grounded end of the second line and an end connected to the end being different from the opened end of the third line. The second balun includes: a fifth line having a grounded end and an end connected to a positive input of a second differential input signal; a sixth line having a grounded end and an end connected to a negative input of the second differential input signal; a seventh line formed in parallel with the fifth line, the seventh line having an opened end corresponding to the grounded end of the fifth line and an end different from the opened end of the seventh line; and an eighth line formed in parallel with the sixth line, the eighth line having a single-ended output end corresponding to the grounded end of the sixth line and an end connected to the end different from the opened end of the seventh line.

DETAILED DESCRIPTION OF THE INVENTION

The present invention realizes a power combiner by use of Marchand Baluns in order to shorten the series line length of the power combiner and improve the frequency characteristics thereof. The Marchand Balun is a balun, which is composed of the distributed element model circuit, capable of converting the differential input (balanced input) to the single-ended output (unbalanced output). An embodiment of the present invention realizes a power combiner by having a plurality of the Marchand Baluns and connecting their unbalanced outputs having the same phase each other to provide combined output.

First Embodiment

Hereinafter, one embodiment of the present invention is described in detail with reference to the drawings.FIG. 1is a block diagram showing a configuration of a transmitter of the embodiment of the present invention. As shown inFIG. 1, the transmitter1of the embodiment includes filters50and51, a PLL60, a phase shifter61, mixers70and71, a power divider80, amplifiers AMP1and AMP2, and a power combiner90.

The filters50and51cut high frequency components respectively from the baseband signals of I,Q channels being sent from a signal processor not shown in the drawing. The PLL60is a local oscillator to generate a local signal for converting the baseband signal to an RF signal. The phase shifter61performs a π/2 phase-shifting for a part of the local signal generated by the PLL60, and sends the original local signal and the phase-shifted local signal to the mixers70and71respectively.

The mixer70multiplies the original local signal received from the phase shifter61and the baseband signal of I channel passed through the filter50to perform the frequency conversion to the RF signal. Similarly, the mixer71multiplies the phase-shifted local signal received from the phase shifter61and the baseband signal of Q channel passed through the filter51to perform the frequency conversion to the RF signal. These two RF signals frequency-converted by the mixers70and71are combined and sent to the power divider80.

The configuration from the filters50and51to the mixers70and71is an example by use of the direct conversion system. The RF signals may be generated by any other systems.

The power divider80divides the received RF signal. The amplifiers AMP1and AMP2amplify the two RF signals divided by the power divider80up to the prescribed power respectively. The operations of the amplifiers AMP1and AMP2can be done in the classes A-C and D-F, depending on the modulation types of the RF signals. In this embodiment, the amplifiers AMP1and AMP2output the differential signals (balanced signals).

The power combiner90combines the amplified signals of the amplifiers AMP1and AMP2(the first differential input signal/the second differential input signal). The power combiner90includes a first balun10and a second balun20. The power combiner90outputs the combined RF signal as the single-ended signal (unbalanced signal).

The first and the second baluns10and20are the Marchand Balun composed of the distributed element model circuit. The first balun10includes: a first line11with λ/4 length in which one end thereof (“a” in the drawing; hereinafter described in the same manner) is grounded and another end (b) thereof is connected to a positive output (the positive side of the amplified output) of the amplifier AMP1; a second line12with λ/4 length in which one end (c) thereof is grounded and another end (d) thereof is connected to a negative output (the negative side of the amplified output) of the amplifier AMP1; a third line13with λ/4 length formed in parallel with the first line11in which one end (e) thereof corresponding to the grounded end (a) of the first line11is opened; and a forth line14with λ/4 length formed in parallel with the second line12in which one end (g) thereof corresponding to the grounded end (c) of the second line12is connected to the RF output (RFout) and another end (h) thereof is connected to another end (f) of the third line13. The first line11and the third line13are coupled electromagnetically, and the second line12and the forth line14are coupled electromagnetically. The end (f) of the third line13and the end (h) of the forth line14may be formed integrally, or may be connected via a line. Here, λ denotes a wavelength of the signal to be combined substantially.

Similarly, the second balun20includes: a fifth line21with λ/4 length in which one end (i) thereof is grounded and another end (j) thereof is connected to a positive output of the amplifier AMP2; a sixth line22with λ/4 length in which one end (k) thereof is grounded and another end (l) thereof is connected to a negative output of the amplifier AMP2; a seventh line23with λ/4 length formed in parallel with the fifth line21in which one end (m) thereof corresponding side to the grounded end (i) of the fifth line21is opened; and an eighth line24with λ/4 length formed in parallel with the sixth line22in which an end (o) thereof corresponding to the grounded end (k) of the sixth line22is connected to the RF output and another end (p) thereof is connected to another end (n) of the seventh line23. As similar as the first balun10, the fifth line21and the seventh line23are coupled electromagnetically, and the sixth line22and the eighth line24are coupled electromagnetically. The end (n) of the seventh line23and the end (p) of the eighth line24may be formed integrally, or may be connected via a line.

The first balun10and the second balun20are composed of, for example, a conductive layer as a strip line formed on a dielectric substrate (not shown in the drawing). The electromagnetic couplings between the lines are realized by providing the lines in close positions with a prescribed distance. The lines to be coupled each other may be formed on the different substrates respectively to form a layer structure in order to couple in a vertical direction with respect to the substrates.

As shown inFIG. 1, in the first balun10and the second balun20, a pair of the end (b) of the first line11and the end (d) of the second line12, and a pair of the end (j) of the fifth line21and the end (l) of the sixth line22function as differential terminals. On the other hand, the RF output used with ground functions the single-ended terminal.

In the transmitter1of this embodiment, the RF signal from the mixers70and71is divided in two to input to two amplifiers AMP1and AMP2. The amplifiers AMP1and AMP2amplify each of the divided RF signals up to the prescribed power respectively and input each of the outputs thereof to the differential terminals of the first balun10and the second balun20respectively as the differential outputs. In the first balun10and the second balun20, since the single-ended output terminals outputting the same phase signals each other are connected each other, the RF signals amplified by the amplifiers AMP1and AMP2respectively are combined to output at the RF output (RFout).

According to the power combiner, the amplifier and the transmitter of this embodiment, it is possible to shorten the line length of the line connected from the output terminals in series, compared to the example in which the single-ended terminals are connected from the output in series. Namely, it is possible to reduce the loss of the power combiner caused by the series resistance and the substrate resistance, and widen the available frequency bandwidth. As the result, it enables the amplifier and the transmitter to enhance the output power, efficiency and available frequency bandwidth.

Here, the principle of operation of the power combiner90in this embodiment will be described in detail with reference toFIG. 2.FIG. 2AtoFIG. 2Dare the conceptual diagram explaining the principle of operation of the power combiner90of this embodiment.

First, in the first balun10with reference toFIG. 2A, it is assumed that the phase at the positive output of the amplifier AMP1is zero-phase. When a phase at the side of the end (b) of the first line11connected to the positive output of the amplifier AMP1is zero degree, the phase lead of 90 degrees is given at the grounded end (a) because the end (a) is grounded. Since the first line11and the third line13are electromagnetically coupled each other, the phase lead of 90 degrees is also given at the opened end (e) of the third line13at the corresponding side of the end (a) of the first line11. The phase at the other end (f) is still zero degree. Then, the phase lag of 90 degrees (forwarded−90 degrees or 270 degrees) is given at the end (g) of the forth line14in which the other end (h) thereof is connected to the end (f) of the third line13. Namely, the phase at the RF output is −90 degrees when the phase at the positive output of the amplifier AMP1is zero degree.

Next, it is assumed that the phase at the negative output of the amplifier AMP1is 180 degrees with reference toFIG. 2B. When a phase at the side of the end (d) of the second line12connected to the negative output of the amplifier AMP1is 180 degrees, the phase lead of 90 degrees is given at the grounded end (c) so that the phase is forwarded to the phase of 270 degrees because the end (c) of the second line12is grounded. Since the second line12and the forth line14are electromagnetically coupled each other, the phase at the end (g) of the forth line14at the corresponding side of the end (c) of the second line12is also 270 degrees, and the phase at the other end (h) is 180 degrees. Then, the phase lag of 90 degrees is given at the end (e) of the third line13in which the end (f) thereof is connected to the end (h) of the forth line14, and the phase lag of 90 degrees is further given at the ends (f) and (h), i.e. in total the phase lag of 180 degrees is given at the ends (f) and (h), because the signal is reflected at the opened end (e) of the third line13. Namely, the phase of the reflected signal is zero-degrees (=180−180). Further, the phase of the reflected signal is −90 degrees at the end (g) connected to the RF output since the forth line14gives the additional phase lag of 90 degrees.

The second balun20is the similar as above. It is assumed that the phase at the negative output of the amplifier AMP2is 180 degrees with reference toFIG. 2C. When a phase at the side of the end (l) of the sixth line22connected to the negative output of the amplifier AMP2is 180 degrees, the phase lead of 90 degrees is given at the grounded end (k) so that the phase is forwarded to the phase of 270 degrees because the end (k) of the sixth line22is grounded. Since the sixth line22and the eighth line24are electromagnetically coupled each other, the phase at the end (o) of the eighth line24at the corresponding side of the end (k) of the sixth line22is also 270 degrees, and the phase at the other end (p) is 180 degrees. Then the phase lag of 90 degrees is given at the end (m) of the seventh line17in which the end (n) thereof is connected to the end (p) of the eighth line24, and the phase lag of 90 degrees is further given at the ends (n) and (p), i.e. in total the phase lag of 180 degrees is given at the ends (n) and (p), because the signal is reflected at the opened end (m) of the third line13. Namely, the phase of the reflected signal is zero-degrees (=180−180). Further, the phase of the reflected signal is −90 degrees at the end (o) connected to the RF output since the eighth line24gives the additional phase lag of 90 degrees.

Next, it is assumed that the phase at the positive output of the amplifier AMP2is zero-degree with reference toFIG. 2D. When a phase at the side of the end (j) of the fifth line21connected to the positive output of the amplifier AMP2is zero degree, the phase lead of 90 degrees is given at the grounded end (i) because the end (i) of the fifth line21is grounded. Since the fifth line21and the seventh line23are electromagnetically coupled each other, the phase at the opened end (m) of the seventh line23at the corresponding side of the end (i) of the fifth line21is also 90 degrees, and the phase of the other end (n) is zero degree. Then, the phase lag of 90 degrees (forwarded −90 degrees or 270 degrees) is given at the end (o) of the eighth line24in which the end (p) thereof is connected to the end (n) of the seventh line23. Namely, the phase at the RF output is −90 degrees when the phase at the positive output of the amplifier AMP2is zero degree.

As a result, when each of the phases of the positive outputs of the amplifiers AMP1and AMP2is zero-degree, the phase at the RF output is always −90 degrees. This means that all of the positive and negative outputs of the amplifiers AMP1and AMP2are combined in same phase and the power combining is realized.

As above, the power combiner, the amplifier and the transmitter of this embodiment include the parallel power combiner using the Marchand Balun, and this enables the series line length to shorten compared to the series connection. And it is possible to reduce the loss at the power combiner caused by the series resistance of the transmission line and the substrate resistance. The frequency characteristics are also improved because the series line length is shortened. And the output power, available bandwidth and efficiency of the power amplifier using this power combiner are improved because the loss is reduced and the frequency bandwidth is widened.

Second Embodiment

Next, a transmitter of the other embodiment of the present invention will be described with reference toFIG. 3.FIG. 3is a block diagram showing a configuration of the power combiner91and the amplifier among that of the transmitter of the other embodiment of the present invention. The transmitter of this embodiment includes an RF positive output (RFout+) instead of the RF output (RFout) among the elements of the transmitter shown inFIG. 1, and further includes an RF negative output (RFout−) at the end (m) of the seventh line. So the common elements are shown with the same symbols, and the redundant description and the redundant showings in the drawings are omitted.

The power combiner91of this embodiment includes a second balun120being modified based on the second balun20shown inFIG. 1. Specifically, the second balun120includes: the fifth line21with λ/4 length in which one end (i) thereof is grounded and another and (j) thereof is connected to the positive output of the amplifier AMP2; the sixth line22with λ/4 length in which one end (k) thereof is grounded and another end (l) thereof is connected to the negative output of the amplifier AMP2; the seventh line123with λ/4 length formed in parallel with the fifth line21in which one end (m) thereof corresponding to the grounded end (i) of the fifth line21is connected to the RF negative output (RFout−); and the eighth line24with λ/4 length formed in parallel with the sixth line22in which the end (o) thereof corresponding to the grounded end (k) of the sixth line22is connected to the RF positive output (RFout+) and another end (p) thereof is connected to another end (n) of the seventh line123.

As shown inFIG. 2CandFIG. 2D, a phase difference between at the end (o) of the eighth line24and at the end (m) of the seventh line23(123) is given 180 degrees. According to this embodiment, it is configured that the RF positive output (RFout+) and the RF negative output (RFout−) give a differential output by use of the above characteristic.

According to the power combiner, the amplifier and the transmitter of this embodiment, it is possible to reduce the loss at the power combiner caused by the series resistance and the substrate resistance, and further widen the available frequency bandwidth. As a result, it is possible to improve output power, efficiency, and bandwidth for the amplifier and the transmitter in total.

Third Embodiment

Next, a transmitter of the other embodiment of the present invention will be further described with reference toFIG. 4.FIG. 4is a block diagram showing a configuration of the power combiner92and the amplifier among the elements of the transmitter of the still other embodiment of the present invention. The transmitter of this embodiment further includes a third balun130and an amplifier AMP3in addition to the configuration of the transmitter shown inFIG. 3. So the common elements are shown with the same symbols, and the redundant description and the redundant showings in the drawings are omitted.

The power combiner92of this embodiment further includes a third balun130. The third balun130includes: a ninth line31with λ/4 length in which one end (q) thereof is grounded and another end (r) thereof is connected to the positive output of the amplifier AMP3; a tenth line32with λ/4 length in which one end (s) thereof is grounded and another end (t) thereof is connected to the negative output of the amplifier AMP3; an eleventh line33with λ/4 length formed in parallel with the ninth line31in which one end (u) thereof corresponding side to the grounded end (q) of the ninth line31is connected to the negative output (RFout−); and a twelfth line34with λ/4 length formed in parallel with the tenth line32in which one end (w) thereof corresponding side to the grounded end (s) of the tenth line32is opened and another end (x) thereof is connected to another end (v) of the eleventh line33.

As shown inFIG. 2AtoFIG. 2D, a phase difference between the end (u) of the eleventh line33and the end (w) of the twelfth line34is given 180 degrees. This embodiment is also configured to obtain the differential output as similar as the embodiment shown inFIG. 3.

According to the power combiner, the amplifier and the transmitter of this embodiment, it is possible to reduce the loss at the power combiner caused by the series resistance and the substrate resistance, and further widen the available frequency bandwidth. As a result, it is possible to improve output power, efficiency, and bandwidth for the amplifier and the transmitter in total.

Forth Embodiment

Next, a transmitter of the still other embodiment of the present invention will be described with reference toFIG. 5AandFIG. 5B.FIG. 5Ais a block diagram showing a configuration of the power combiner93aand the amplifier among the elements of the transmitter of the still other embodiment of the present invention,FIG. 5Bis a block diagram showing a modified example of the transmitter shown inFIG. 5A. The transmitter of this embodiment further includes a forth balun140and an amplifier AMP4in addition to the configuration of the transmission shown inFIG. 4, and includes the RF output (RFout) having the modified connection point. So the common elements are shown with the same symbols, and the redundant description and the redundant showings in the drawings are omitted.

The power combiner93aof this embodiment further includes a fourth balun140. The fourth balun140includes: a thirteenth line41with λ/4 length in which one end (A) thereof is grounded and another end (B) thereof is connected to the positive output of the amplifier AMP4; a fourteenth line42with λ/4 length in which one end (C) thereof is grounded and another end (D) thereof is connected to the negative output of the amplifier AMP4; a fifteenth line43with λ/4 length formed in parallel with the thirteenth line41in which one end (E) thereof corresponding side to the grounded end (A) of the thirteenth line41is opened; and a sixteenth line44with λ/4 length formed in parallel with the fourteenth line42in which one end (G) thereof corresponding side to the grounded end (C) of the fourteenth line42is connected to the end (w) of the twelfth line34and another end (H) thereof is connected to another end (F) of the fifteenth line43. Further, the RF positive output (RFout+) is removed and the RF negative output (RFout−) is used as the single-ended output, RF output (RFout). As a result, it is configured that the additional Marchand Balun is added to each of the opened ends of the first balun10and the second balun20of the power combiner90of the transmitter shown inFIG. 1.

As shown inFIG. 2AtoFIG. 2D, a phase difference between the end (E) of the fifteenth line43and the end (G) of the sixteenth line44is given 180 degrees. In this embodiment, as similar as the power combiner90shown inFIG. 1, the RF output (RFout) is provided at the end (m) of the seventh line123of the second balun120, i.e. at the center of the line.

According to the power combiner, the amplifier and the transmitter of this embodiment, it is possible to reduce the loss at the power combiner caused by the series resistance and the substrate resistance, and further widen the available frequency bandwidth. As a result, it is possible to realize high output power, high efficiency, and wide bandwidth for the amplifier and the transmitter in total. Especially in this embodiment, since the RF output signal is obtained from the center of the line, the power combiner having balanced and wide bandwidth characteristics can be obtained.

The power combiner93bshown inFIG. 5Bis configured to change the connection point of the RF output of the power combiner93ashown inFIG. 5A. Specifically, the RF output (RFout) is connected to the end (g) of the fourth line14of the first balun10and the end (w) of the twelfth line34of the third balun130. According to the power combiner93bof this embodiment, as compared to the power combiner93ashown inFIG. 5A, the combined output is obtained at the plural ends in parallel. Therefore it is possible to reduce the loss caused by the series resistance and the substrate resistance further.

Fifth Embodiment

Next, a transmitter of the still other embodiment of the present invention will be described with reference toFIG. 6.FIG. 6is a block diagram showing a configuration of the power combiner94and amplifier among the elements of the transmitter of the still other embodiment of the present invention. The transmitter of this embodiment is configured to change the configuration of the first balun10and the second balun20shown inFIG. 1. So the common elements are shown with the same symbols, and the redundant description and the redundant showings in the drawings are omitted.

As shown inFIG. 6, the first balun210of this embodiment includes: a seventeenth line215with λ/4 length formed in parallel with the third line13in which one end (I) thereof is grounded and another end (J) thereof is connected to the positive output of the amplifier AMP5; and a eighteenth line216with λ/4 length formed in parallel with the fourth line14in which one end (K) thereof is grounded and another end (L) thereof is connected to the negative output of the amplifier AMP5in addition to the configuration of the first balun10. Similarly, the second balun220of this embodiment includes: a nineteenth line225with λ/4 length formed in parallel with the seventh line23in which one end (M) thereof is grounded and another end (N) thereof is connected to the positive output of the amplifier AMP6; and a twentieth line226with λ/4 length formed in parallel with the eighth line24in which one end (O) thereof is grounded and another end (P) thereof is connected to the negative output of the amplifier AMP6in addition to the configuration of the second balun20.

The seventeenth line215is electromagnetically coupled to the third line13as similar as the first line11. Similarly, the eighteenth line216is coupled to the fourth line14as similar as the second line12, the nineteenth line225is coupled to the seventh line23as similar as the fifth line21, and the twentieth line226is coupled to the eighth line24as similar as sixth line22, electromagnetically respectively.

In the power combiner94of this embodiment, the coupling to the line being connected to the RF output is in common. Therefore, the number of baluns being capable of connecting in parallel can be increased, and this enables to reduce the required area and volume. Moreover, it is expected that the loss caused by the series resistance and the substrate resistance can be further reduced.

Application Example

Next, the application example of the power combiner of the embodiments of the present invention will be described with reference toFIG. 7.FIG. 7is a diagram describing the application example of the power combiner of the embodiments of the present invention.

In general, it is known that the passive balun can be used with the similar characteristics even though the input and the output thereof are replaced each other. In the application example shown inFIG. 7, the power divider95having an RF output1(RFout1) and an RF output2(RFout2) which are the amplified inputs of the power combiner90of the embodiments of the present invention, and having an RF input (RFin7) which is the RF output of the power combiner90is realized. According to the configuration, the power divider providing similar benefits as the power combiner90can be obtained. Certainly, the power divider can be obtained if the input and the output of the other power combiners91to94of the embodiments of the present invention are replaced each other. According to the above embodiments, it is possible to suppress the degradation of the output power, the efficiency and the available frequency bandwidth.

The present invention is not limited to the above embodiments as it is, and any of the elements may be modified to realize without departing from the gist of the present invention. For example, according to the description of the above embodiment, it is explained that the transmission lines in which the lines are formed on the prescribed dielectric substrate are placed closely in a plain surface, but it is not limited thereto. For example of the power combiner90shown inFIG. 1, the first line11and the second line12may be formed on a first substrate, and the third line13and the fourth line14may be formed on a second substrate to form a layer structure having the first and the second substrates, in order to realize the electromagnetic couplings between the lines. Such structure enables to reduce the required area on the substrate. Especially in the power combiner94of the embodiment shown inFIG. 6, it is expected to obtain the merit of reducing the noise mixed from outside because of the steric structure.

Further, several types of the invention may be made by appropriate combination of the plural elements disclosed in the above embodiments. For example, some element may be removed from all of the elements of the configurations shown in the embodiments, and the elements belonging to the different embodiments respectively may be combined appropriately.

The present invention may be applied to the telecommunication manufacturing industry.