DESC:FIELD
The present disclosure relates to the field of wireless communication.
DEFINITIONS OF TERMS USED IN THE SPECIFICATION
The expression ‘cellular network’ used hereinafter in this specification refers to a communications/mobile network which is distributed over land areas called cells. Each of the cells use a different set of frequencies from neighboring cells to avoid interference and to provide guaranteed bandwidth within each cell. Every cell from the cellular network is served by at least one base station.
The expression ‘pico base station/picocell’ used hereinafter in this specification refers to a small cellular base station which covers small areas. These base stations are typically used to extend coverage to indoor areas where outdoor signals do not reach well, or to add network capacity in areas with very dense phone usage. The pico base stations provide coverage to substantially inaccessible areas where traditional macro cell approach cannot be used.
The expression ‘ultra-dense small cell network’ used hereinafter in this specification refers to a network which consists of multiple small cells deployed in higher frequency bands. The ultra-dense small scale networks increase use of spectrum and network efficiently.
The expression ‘Long-Term Evolution (LTE)’ used hereinafter in this specification refers to a standard for wireless communication of high-speed data for mobile phones and data terminals. LTE is based on the GSM/EDGE and UMTS/HSPA network technologies and it is used for increasing the capacity and speed of the cellular networks.
The expression ‘LDMOS’ used hereinafter in this specification refers to laterally diffused metal oxide semiconductor transistors which are used in RF power amplifiers. Silicon-based LDMOS FETs are widely used in RF power amplifiers for base-stations as they provide high output power with a corresponding drain to source breakdown voltage. LDMOS transistors fulfill the requirements for a wide range of class AB and pulsed applications.
The expression ‘data offloading’ used hereinafter in this specification refers to mobile data/Wi-Fi offloading which includes using network technologies for delivering data targeted for cellular networks. Data offloading frees bandwidth for other users by reducing amount of data being carried on the cellular bands. It is also allows users to connect via wired services with better connectivity in situations where local cell reception is poor.
The expression ‘baseband module’ used hereinafter in this specification refers to a unit that processes baseband signals in telecommunication systems. The baseband module is responsible for communication through the physical interface.
The expression ‘RF module’ used hereinafter in this specification refers to an electronic device used to transmit and/or receive radio signals between two devices.
The expression ‘cavity filter’ used hereinafter in this specification refers to a sharply tuned resonant circuit that allows only certain frequencies to pass. Generically, these filters are known as notch filters. Physically a cavity filter is a resonator inside a conducting box with coupling loops at the input and output.
The expression ‘hybrid coupler’ used hereinafter in this specification refers to a passive device used in radio and telecommunications. It is a type of directional coupler where the input power is divided between two output ports.
The expression ‘single stage power amplifier’ used hereinafter in this specification refers to a power amplifier having only one power amplifying component, a bias circuit and other auxiliary components.
The expression ‘Continuous Wave (CW) operation’ used hereinafter in this specification refers to a narrower bandwidth mode of operation obtained by providing an input signal having continuous sinusoidal oscillation, with amplitude varying between zero and full carrier strength.
The expression ‘heat-spreader’ used hereinafter in this specification refers to a heat exchanger that moves heat between a heat source and a secondary heat exchanger whose surface area and geometry are more favorable than the source. Such a spreader is most often simply a plate made of copper, which has a high thermal conductivity. By definition, heat is "spread out" over this geometry, so that the secondary heat exchanger may be more fully utilized.
The expression ‘Time Division Duplex (TDD) Switch’ used hereinafter in this specification refers to a switch used for changing mode of a communication system between a transmission mode and a reception mode. This enables a transmission path to be separated from a reception path. The TDD switch operates in response to a TDD control signal of the communication system.
The expression ‘Circulator’ used hereinafter in this specification refers to a passive non-reciprocal three or four-port device, in which a microwave or radio frequency signal entering any port is only transmitted to the next port in rotation. Here, a port is a point where an external waveguide or transmission line (such as a micro-strip line or a coaxial cable), connects to the device.
The expression ‘matched impedance’ used hereinafter in this specification refers to a situation where maximum power transfer is achieved by designing input impedance of an electrical load or the output impedance of its corresponding signal source. Maximum possible power is delivered to the electrical load when the impedance of the load (input impedance) is equal to the complex conjugate of the impedance of the source.
The expression ‘Wilkinson couplers (Wilkinson power dividers/combiners)’ used hereinafter in this specification refers to a specific class of power divider circuits that can achieve isolation between the output ports while maintaining a matched condition on all ports. The WilkinsonTM design can also be used as a power combiner because it is made up of passive components and hence reciprocal.
The expression ‘Adjacent Channel Power Ratio (ACPR)’ used hereinafter in this specification refers to a ratio of the average power in the adjacent frequency channel to the average power in the transmitted frequency channel. It describes the amount of power generated in the adjacent channel due to nonlinearities in RF components.
The expression ‘micro-strip transmission line’ used hereinafter in this specification refers to an electrical transmission line which can be fabricated using printed circuit board technology and can be used to convey microwave-frequency signals. It consists of a conducting strip separated from a ground plane by a dielectric layer known as the substrate. Microwave components such as antennas, couplers, filters, power dividers etc. can be formed from micro-strip, with the entire device existing as the pattern of metallization on the substrate.
The expression ‘back-off’ used hereinafter in this specification refers to a reduction of the output power when reducing the input power. It is a ratio between the input power that delivers maximum power to the input power that delivers the desired linearity.
The expression ‘electrical termination’ used hereinafter in this specification refers to a termination of a signal by providing a terminator at the end of a wire or cable to prevent an RF signal from being reflected back from the end, causing interference.
The expression ‘insertion loss’ used hereinafter in this specification refers to the loss of signal power resulting from the insertion of a device in a transmission line or optical fiber.
The expression ‘saturation region’ used hereinafter in this specification refers to a region of operation where an amplifier output does not increase even after increasing its input. The amplifier enters its saturation region if its input voltage is raised above a certain limit. If an amplifier saturates, even momentarily, the resulting output is distorted. The fact that an output voltage of a practical amplifier cannot exceed certain threshold value is called saturation.
The expression ‘distortion’ used hereinafter in this specification refers to an occurrence where an output of a power amplifier is distorted i.e. it is not a complete reproduction of the original input signal.
These definitions are in addition to those expressed in the art.
BACKGROUND
For the last few years, growth in smartphones has caused increasing usage of mobile data via the cellular networks. A cellular network having high data capacity is therefore a critical requirement. In order to meet the requirements of high data capacity in cellular networks, small cell base stations are being typically used. However, a base station in which transit signals are received for onward communication consume most energy of the overall energy requirement of a mobile network.
Different internal components of a base station include a power amplifier, a signal processing module, a mains supply, a DC-DC supply, a cooling apparatus and a Radio Frequency (RF) module. The power amplifier consumes a significant amount of power required by the base station. The power amplifier energy consumption is a key problem for small cell base stations including outdoor Pico Base Stations. LTE outdoor Pico Base Stations are available in 0.5 W (27 decibel-milliwatts (dBm)) to 2 W (33 dBm) range of transmit power. Conventional outdoor pico base station manufacturers use high power LDMOS transistors in back-off to get the desired transmitting power in the above mentioned range. This in turn reduces the efficiency of a power amplifier as it is operated in the back-off and not near its saturation region. An LDMOS transistor operates usually with +28 V DC power supply along with an additional supply at the gate bias. Therefore, existing outdoor pico base station solutions use -48 V DC supply and -48 V DC to +28 V DC to DC converters. Such convertors introduce additional power losses. Both the components also contribute considerably to the cost of conventional outdoor pico base stations.
In mobile telecommunication, the current trend is to have ultra-dense small cell networks which provide for data offloading as well as coverage expansion particularly in rural and interior areas. In such a situation, it is of utmost importance to address the problem of power consumption and the high cost of installation and maintenance of an outdoor pico base station. This disclosure tackles this need by addressing alternations in the power amplifying module in an attempt to reduce power consumption and cost of a pico base station.
OBJECTS
Some of the objects of the present disclosure aimed to ameliorate one or more problems of the prior art or to at least provide a useful alternative are described herein below:
An object of the present disclosure is to provide a system of outdoor pico base station.
Another object of the present disclosure is to provide a system of outdoor pico base station which does not require a cooling arrangement.
Yet another object of the present disclosure is to provide a system of outdoor pico base station which is power efficient.
Still another object of the present disclosure is to provide a low cost system.
An additional object of the present disclosure is to provide a system of outdoor pico base station with reduced size.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure envisages a power amplifier module for a pico base station. The pico base station includes a DC to DC converter for supplying power to the pico base station, a baseband module coupled to an RF module through a plurality of pre-determined interfaces for obtaining RF signals, the power amplifier module coupled to the RF module for receiving and amplifying RF input power and obtaining amplified RF output, and a plurality of cavity filters coupled to the power amplifier module for receiving and filtering the RF output to obtain suitable RF signals for onward transmission via at least one antenna. To amplify RF input power, the power amplifier module comprises a plurality of Wilkinson couplers and a plurality of balanced power amplifying circuits. The Wilkinson couplers are configured to divide the RF input power and supply the divided power to the power amplifying circuits, and further configured to receive amplified outputs from the power amplifying circuits, combine the received amplified outputs and supply the combined outputs to the cavity filters for onward transmission.
In one embodiment, the Wilkinson couplers present in the power amplifier module of the present disclosure equally divide the RF input power. In another embodiment, these Wilkinson couplers are configured as power dividers adapted to split and/or combine power. Further, the balanced power amplifying circuits present in the power amplifiers include at least two power amplifying components connected in parallel. In an embodiment, these power amplifying components are integrated circuits.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
A power amplifier module for a pico base station and a power amplifying method envisaged in the present disclosure will now be described with the help of accompanying drawing, in which:
FIGURE 1 illustrates a schematic block diagram of one embodiment of a pico base station;
FIGURE 2 illustrates a schematic representation of a power amplifier module of a pico base station in accordance with one embodiment of the present disclosure;
FIGURE 3 illustrates graphical representation of output power for a single stage power amplifier and the power amplifier module in accordance with the present disclosure;
FIGURE 4 illustrates the graphical representation of obtained gain for output power in a single stage power amplifier and the power amplifier module in accordance with the present disclosure;
FIGURE 5a illustrates a schematic representation of an Outdoor Pico Base Station system in accordance with one embodiment of the present disclosure;
FIGURE 5b and 5c illustrates the mounting mechanism of supply and backhaul connectors;
FIGURE 5d illustrates the IP 65 complied Cavity filter with RF connectors; and
FIGURE 6a illustrates the ABS plastic top cover of a Pico Base Station and FIGURE 6b illustrates the bottom cover with heat sink of Pico Base Station in one embodiment of the present disclosure.
DETAILED DESCRIPTION
A system of outdoor pico base station of the present disclosure will now be described with reference to the embodiments shown in the accompanying drawing. The embodiments do not limit the scope and ambit of the disclosure. The description relates purely to the examples and preferred embodiments of the disclosed system and its suggested applications.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known parameters and processing techniques are omitted so as to not unnecessarily obscure the embodiment herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiment herein may be practiced and to further enable those of skill in the art to practice the embodiment herein. Accordingly, the examples should not be construed as limiting the scope of the embodiment herein.
The following description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
In a power amplifier maximum average output power, operating bandwidths, high linearity, and Peak-to-average Ratio of the signal are criteria that need to be taken into account. Energy consumption is also another important criterion as it increases the overall operating expense of a cellular network. It is therefore desirable to construct a power amplifier module which consumes less power during its operation. Power amplifiers of base stations are required to operate near saturation region to get the best efficiency with negligible distortion. Solutions applicable to power amplifiers of macro base stations are not transposable to pico base stations. LDMOS transistors used typically in a power amplifier of a pico base station require range of 1 Watt to 20 Watt Continuous Wave (CW) operation for an average power output of 0.5 watt to 2 watt at the antenna port per chain. Efficient LDMOS transistors are available for high power applications of typically more than 50 watt CW, but, not in the 1 - 20 watt range. Additionally, as stated earlier LDMOS transistors require 28 V DC power supply and hence the available –48 V DC supply needs to be converted to +28V DC with the help of DC-DC converters which again increases the power consumption of the base station.
Moreover, LDMOS transistors have either a ceramic package or plastic package which has one heat spreader in the operative lower end of the transistor through which heat dissipates in either a heat sink or any other metal body of the base station. The heat-spreader needs to be in direct contact with either a copper plate or a heat sink body of the base station. This increases the complexity of the power amplifiers. The gate bias of LDMOS transistors vary from transistor to transistor and this further adds to the power consumption in the process of mass manufacturing of power amplifier modules for the pico base stations.
Referring to the accompanying drawing, FIGURE 1 illustrates a schematic block diagram of one embodiment of a pico base station 100. A +12 V external supply voltage (not shown in the figure) is provided to the pico base station 100. This voltage is converted to a 5.5/5V DC supply by a DC to DC converter 106. The DC to DC converter 106 is configured to supply required voltages to different components of the pico base station 100. A baseband module 110 is present in the pico base station 100 and is coupled to an RF module 104 through a plurality of pre-determined interfaces to obtain RF signals. A power amplifier module 108 is coupled to the RF module 104 to receive and amplify RF input power and obtain amplified RF output. This RF output is provided to a plurality of cavity filters 102 which filter the RF output to obtain filtered RF signals for onward transmission via at least one antenna. The power amplifier module 108 of the present disclosure does not use typical LDMOS transistors, instead it used Wilkinson couplers and power amplifying circuits to reduce overall power consumption in a pico base station.
FIGURE 2 of the accompanying drawing illustrates a schematic representation of the power amplifier module 108 of a pico base station in accordance with one embodiment of the present disclosure. The power amplifier module 108 envisaged in one embodiment of the present disclosure includes a plurality of Wilkinson couplers 200a, 200b …200f and a plurality of power amplifying circuits 204 and 206. The Wilkinson coupler 200a receives RF input power from the RF module 104 and divides the RF input power. In one embodiment, the power to be provided to the power amplifying circuits 204a and 204b is divided equally. In this embodiment, the divided power is further provided to Wilkinson coupler 200b and 200c. Here, Wilkinson couplers 200a, 200b and 200c act as power dividers for splitting power. The divided power output of Wilkinson coupler 200b is provided to power amplifying components 202a and 202b present in one power amplifying circuit 204a. Similarly, the divided power output of the Wilkinson coupler 200c is provided to power amplifying components 202c and 202d present in another power amplifying circuit 204b. In one embodiment, the power amplifying components 202a and 202b, and 202c and 202d are connected in a balanced amplifier configuration. The power amplifying components 202a, 202b, 202c and 202d amplify the received RF input power. The amplified outputs of the power amplifying components 202a and 202b are provided to the Wilkinson coupler 200d which combine the amplified outputs to obtain an amplified output. Similarly, the amplified outputs of the power amplifying components 202c and 202d are provided to the Wilkinson coupler 200e which combine these outputs to obtain another amplified output. These outputs of the Wilkinson couplers 200d and 200e are then provided to another Wilkinson coupler 200f to obtain a single amplified RF output. In one embodiment, the Wilkinson couplers 200d, 200e and 200f act as power combiners for combining the amplified power. The output obtained by the Wilkinson coupler 200f is then provided to the cavity filters 102 for onward transmission.
In one practical embodiment, the power amplifier 108 includes four power amplifying circuits in the form of integrated circuits (ICs) with double stage balanced configuration architecture i.e. the ICs are connected parallely in the balanced configuration. Each power amplifying circuit IC is able to provide +27 dBm average output power for 20 MHz LTE signal. The double stage balanced configuration increases the average output power by 5.5 to 5.6 dB and hence the overall output power increases from +27 dBm to +32.5 dBm which is required at the power amplifier 108 output to achieve +30 dBm at Outdoor Pico BS antenna port. There is a 2.5 dB loss between the power amplifier 108 and the antenna port due to TDD Switch, Circulator, Cavity Filter and RF cables required to design a front end module.
The double balanced configuration of power amplifier is an extension of balanced configuration architecture. It is a nested loop of balanced configuration design as illustrated in FIGURE 2. Conventionally, hybrid couplers are used in balanced configuration of Power Amplifiers.
The hybrid coupler at splitter splits the power equally with 90º phase offset and provides it to both power amplifiers, their outputs are re-combined at other hybrid coupler with swapped 90º phase offset. Reflections due to mismatch from the input and output ports of the power amplifiers are shunted to the unused port of each coupler, giving the entire arrangement a matched impedance. This improves RF stability since the power amplifiers are isolated from outside terminations. Two identical lower-power devices can be used to achieve 3 dB more power than the output power from individual device except insertion losses of hybrid couplers.
In an embodiment hybrid couplers can be replaced by low cost Wilkinson power splitters/combiners which give comparatively very low insertion loss. Further, it is feasible to design them by using micro-strip transmission line concept. The Wilkinson dividers/combiners provide a high degree of isolation between both output ports, and thus can be used for internally matched power amplifier chipsets without any stability or load mismatch concern.
In one embodiment, the pico base station using the power amplifier of the present disclosure provides ~ 6 dB more power than the single design without considering Wilkinson splitter/combiner losses. The double balanced configuration also increases the 3rd order Output Intercept Point (OIP3) by 6 dB. Hence the overall linear output power increases by the same amount except the losses incurred by the Wilkinson combiner and splitter which is approximately 0.4 dB. This is explained in detail with mathematical derivation provided below.
Based on FIGURE 2 of the accompanying drawing, each power splitter /divider reduces the input power by 3 dB. If Pin is the RF input received by the Wilkinson coupler 200a from the RF module, as shown in Figure 2 Input power of second stage splitters, Pin12 is the obtained output of the Wilkinson coupler 200a and Pin34 the output of the Wilkinson coupler 200a which is received by the Wilkinson coupler 200c. Based on this Pin12 and Pin34 are given by:
Therefore, power input to the power amplifying components 202a, 202b, 202c and 202d are Pin1, Pin2, Pin3, Pin4 respectively and are reduced by 6 dB.


(1)
Similarly, output powers of the power amplifying components 202a, 202b, 202c and 202d are Pout1, Pout2, Pout3, Pout4 respectively and are given as below:


Output power at first stage combiner i.e. outputs Pout12, Pout34 are derived as below:


Total power obtained at the output is,
(2)
Above equation shows that output power is same for the given configuration as for the single-stage power amplifier module considering no loss in the Wilkinson splitters/combiners in ideal case. Moreover, equation (1) shows each amplifier can take 6dB more input. That means overall P1 dB point will get increased by 6 dB and we can operate this configuration to get 6 dB more output power.
The power level of 3rd order intermodulation products (IM3) is represented as below equation:

OIP3 is the 3rd order output intercept point in the above formula. For double stage balanced configuration, these products at individual power amplifying circuits 202a, 202b, 202c and 202d are amplifiers (IM31, IM32, IM33, and IM34) and can be derived by below equations.



These products get summed at first stage combiner output and given by IM312 and IM334.


Similarly,

Total 3rd order intermodulation products obtained at the output can be expressed by,

(3)
The relationship between OIP3 and IM3 products are given by

Now putting values of Pout and IM3out from (1) and (2),


(4)
Equation (3) shows that 3rd order intermodulation products which is a major cause of non-linearity are reduced by 12dB and (4) shows OIP3 point is enhanced by 6dB compared to single-stage power amplifier.
For the technologies like LTE which deals with large number of subcarriers, the relationship between Adjacent Channel Power Ratio (ACPR) and 3rd ordered intermodulation ratio (IMR2) for two tone test is given by as below.

As per the formula provided for n-tone ACPR related to IMR2,

With N = (2n3-3n2-2n)/24 and M = n2/24, where n is integer multiple of 2.
For 20 MHz LTE signal, 1200 subcarriers are there in the composite waveform. ACPR gets closer to IMR2 [23] for the signal with larger number of subcarriers.

Calculating ACPR for single-stage power amplifier,

Now, from equation (1) and (3), we can get 6dB more output than single-stage amplifier. It means,



(5)
Above equation (5) illustrates the same ACPR is obtained from double stage balanced configuration at 6 dB higher output power.
This provides a feasible solution to use low cost, lower power devices driven at 5-V supply in double stage balanced configuration rather than using a single higher power device like LDMOS or GaN which needs 28-V supply with more sophisticated heat sink design. This drastically reduces energy consumption as well as makes the complete outdoor pico base station system a viable solution with 12 V power supply instead of a conventional –48 V power supply.
In a working embodiment, Avago’s MGA-43040 Power amplifier is used as a basic unit of the power amplifying components. MGA-43040 is fully matched amplifier based on 0.25µm GaAs enhancement mode pHEMT process technology for band-40 (2.3-2.4 GHz band). It is operated at 5 V supply with 35 dBm P1-dB compression point and works linearly at 27 dBm average output power for 20 MHz LTE signal with 9.8 dB PAPR. This power amplifier integrated circuit (IC) provides –48 dBc ACPR which fulfills 3GPP requirement of minimum -45 dBc for Base station transmitter. An average transmit power requirement of the Outdoor Pico Base Station of the present disclosure is 30 dBm per antenna port. Considering 2.5 dB losses between power amplifier and antenna port, it is necessary to achieve 32.5 dBm average output power at power amplifier module. Use of single MGA-43040 device will not suffice the output power and linearity requirement in terms of ACPR. As described in above mathematical calculations, similar performance at 32.5dBm output power from the same device can be retrieved by using double stage balanced configuration. Output of this working example helps in deciding the expected results of the proposed design with 20 MHz LTE signal.
Referring to Figure 3, illustrates the graphical representation of obtained gain for output power in a single stage power for output 1 dB compression points for single stage power amplifier and double balanced power amplifier in a single graph. Referring to Figure 4 illustrates graphical representation of obtained gain for output power in a single power amplifier and the power amplifier module in accordance with the present disclosure. From the graphical representation it is observed that the double balanced configuration provides 40.5 dBm whereas the single power amplifier provides 35 dBm which is 5.5 dB more than the double balanced configuration in comparison with single stage configuration. Figure 3 and Figure 4, it have thus confirmed the theory of 6 dB increase in compression point for double balanced configuration compared to single stage power amplifier. Considering ~ 0.4 dB combiner /splitter losses, above simulation results are in match with the theory.
In an embodiment, the present disclosure envisages a power amplifying method for pico base station. The method includes steps of receiving RF input power from an RF module, dividing the RF input power and supply the divided power to a plurality of amplifying circuits, amplifying the divided RF input power to obtain amplified outputs, and combining the amplified outputs and supplying the combined outputs to a plurality of cavity filters for onward transmission via at least one antenna.
Referring to the accompanying drawing, Figure 5a illustrates a schematic representation of the Outdoor Pico Base Station system in accordance with one embodiment. In this embodiment, Base band module 110 (base band card) is designed with 12 layers PCB having low cost FR4 material. RF module 104 (RF interface card) is designed with 8 layers PCB having the same material. Power amplifier modules 108 (Double stage balanced PA modules) for primary and secondary transmit chains of 2 x 2 MIMO configuration are fabricated with 4 layers, a bit costlier Roger’s RO4350 PCB as it has low insertion loss at 2.4 GHz frequency range. High speed digital interface between RF module 104 and Baseband module 110 are provided by high speed connector. All board to board RF interfaces are provided by RF cables. Figure 5d illustrates the IP-65 complied two RF connectors 504 of cavity filter 102. These connectors 504 are N-type Female flanged RF connectors. These connectors pass through the holes of the metallic body of heat sink. N-type Female flanged RF connectors 504 passing through metallic base plate at upper side and supply and backhaul connectors passing through mounting plate 502 and gland box with rubber O-rings 500 at lower side make the outdoor pico base station design of the present disclosure, IP-65 compliant without using the IP-65 connectors. Figure 5a and 5c illustrate the mounting mechanism of supply and backhaul connectors 502 by using mounting plate and gland box with rubber O-rings 500. The complete Pico Base Station unit is enclosed with top cover of ABS plastic 600 as shown in Figure 6a and bottom cover with aluminum based heat sink 602 as shown in Figure 6b. Figures 5 and 6 explain the IP-65 complied design of Pico Base Station without using costly IP-65 complied Ethernet and power supply connectors. This feature reduces the design cost further. Further in an embodiment, the Pico Base Station for a 2T2R MIMO configuration with 1 W output power per antenna port offers a cost and energy optimized solution for small cell networks.
TECHNICAL ADVANCEMENTS

The technical advancements of the system of a pico base station and a power amplifying method envisaged by the present disclosure include the realization of:
• a pico base station having reduced power consumption;
• a pico base station that does not require a cooling arrangement; and
• a low cost pico base station.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. ,CLAIMS:1. A power amplifier module for a pico base station, said pico base station having a DC to DC convertor adapted to supply power to the pico base station, a baseband module coupled to an RF module through a plurality of pre-determined interfaces to obtain RF signals, the power amplifier module coupled to the RF module to receive and amplify RF input power and obtain amplified RF output, and a plurality of cavity filters coupled to the power amplifier module to receive and filter said RF output to obtain suitable RF signals for onward transmission via at least one antenna, characterized in that said power amplifier module comprises:
a plurality of Wilkinson couplers and a plurality of balanced low power amplifying circuits, wherein, said Wilkinson couplers are configured to divide the RF input power and supply the divided power to said circuits, and further configured to receive amplified outputs from said circuits, combine said received amplified outputs and supply the combined outputs to said cavity filters.

2. The power amplifier module as claimed in claim 1, wherein said Wilkinson couplers equally divide the RF input power.

3. The power amplifier module as claimed in claim 1, wherein said Wilkinson couplers are configured as power dividers adapted to split and/or combine power.

4. The power amplifier module as claimed in claim 1, wherein each of said balanced power amplifying circuits include at least two power amplifying components connected in parallel.

5. The power amplifier module as claimed in claim 4, wherein said power amplifying components are low power integrated circuits.

6. The power amplifier module as claimed in claim 1, which operates with 5 V and does not require 28 V DC supply.

7. The power amplifier module as claimed in claim 6, which does not require a -48 V to +28 V brick converter module like conventional Pico Base Station systems thereby reducing extra heat dissipation caused by brick-converter thus reducing overall power consumption.

8. The power amplifier module as claimed in claim 7, which does not require additional cooling arrangement.

9. The power amplifier module as claimed in claim 1, wherein said pico base station includes N-type Female flanged RF connectors passing through metallic base plate at upper side and supply and backhaul connectors passing through mounting plate and gland box with rubber O-rings at lower side, and does not use IP-65 connectors.

10. A power amplifying method for pico base station, said method comprising the following:
receiving RF input power from an RF module;
dividing the RF input power and supply the divided power to a plurality of amplifying circuits;
amplifying the divided RF input power to obtain amplified outputs; and
combining the amplified outputs and supplying the combined outputs to a plurality of cavity filters for onward transmission via at least one antenna.

11. The method as claimed in claim 10, wherein said step of dividing the RF input power includes a step of equally dividing the RF input power.