Wide-Band Low Noise Amplifier for LTE Applications

Transcription

1 Journal of Science Technology Engineering and Management-Advanced Research & Innovation Vol. 1, Issue 1, January 2018 Wide-Band Low Noise Amplifier for LTE Applications Veeraiyah Thangasamy Asia Pacific University, Technology Park Malaysia, Bukit Jalil 5700, Kuala Lumpur, Malaysia Abstract: This research is to overcome the problems that are faced in the telecommunication field. LTE or 4G networking is vastly growing, hence this feature requires devices to cover a wide range of frequencies to have a consistent connection to the internet, and therefore it is mandatory to design devices that can fulfil this requirement of being consistently connected to LTE. This research on designing a wide bandwidth LNA so that it can cover frequency range from GHz. While designing this LNA, the focus is also to keep the noise figure NF as minimum as possible. The LNA is designed using L-L type matching network followed by a common emitter topology. Moreover, the simulations were conducted for the Input, Output, Gain, NF and stability. The results obtained were acceptable for the function of LTE network. Researchers conducting this experiment in the future ought to decide the software in which simulations will be conducted and lastly, implement this research on hardware for better evaluations. Keywords: Low Noise Amplifier (LNA), Long term Evolution (LTE), Noise figure (NF), Stability Factor (StabFact), Gain (S21), Bandwidth. 1. Introduction Long-Term Evolution (LTE), is a promptly emerging collective global technology that s constantly developing to offer extraordinary data rates, advanced capacity, and new levels of user experience. LTE is the succeeding step for technology in smartphones. It is quantified by 3G organization hence, the combination of the current cellular or technology for 2G and 3G principles. Meanwhile, this attains complete connectivity with former standards. LTE operates in a range of GHz, supports the Time Division Duplexing (TDD), Frequency Division Duplexing (FDD), lastly, range of a wide bandwidth. [2]. For the LTE to operate at its full potential, it requires a minimal distortion wide band coverage of signals to operate. To achieve a strong undistorted signal, a low noise wide band amplifier is required for this outcome. An amplifier is defined as an electronic device that is responsible for boosting or increasing the amplitude of an electric signal. Thus, this project s objective would be to design a wide band low noise amplifier that would improve the technology of LTE in the telecommunication division. There are five sections in this journal paper, where research problem is section two where the aim and objectives have been described. Followed by proposed methodology being the third section in which the overall constructional detail is explained. Moreover, simulations and results will be illustrated and explained in section four and lastly, conclusion in section five. 23

2 Wide-Band Low Noise Amplifier for LTE Applications Veeriayah Thangasamy 2. Research Problem One of the most puzzling receiver design, features in the application of LTE networks. The first block of the receiver is the LNA that covers the complete band of LTE. Furthermore, it is supposed to offer, low NF, high linearity and flat gain practically for bandwidth to be completed [2]. Nevertheless, absolute constancy and good linearity are significant parameters. Some suggested solutions and circuits for each parameter are available. However, some parameters would need reconstruction by refining the others [1]. After an ideal amount of research done, the most suitable topology that would be needed is the Common Emitter topology. This methodology of Common Emitter has a moderate input impedance followed by a moderate output impedance. It also has a power gain up to 37dB, which is considerably high, followed by a phase inversion. When it comes to design the wide bandwidth LNA, it is important that the gain should be above 10dB, having minimum noise figure. Thus, the research on these topologies were done and concluded to proceed the simulation using common emitter topology. 2.1 Aim & Objectives The Aim of this work is to design the LNA with wide bandwidth coverage from frequencies 400MHz to 2800MHz The Objectives of this work is listed below: - i. To propose a wide bandwidth low noise amplifier for LTE applications. ii. To design a wide bandwidth LNA by simulation using Advance Design System ADS. iii. To evaluate the performance of the LNA so that its Gain, noise figure NF and stability is acceptable for LTE applications. 3. Proposed Methodology 3.1 Overall Block Diagram Figure1 demonstrates the overall block diagram of the wide bandwidth LNA design. The block diagram illustrates in a simple manner, the different parts of the low noise amplifier. Figure 1: Overall Block Diagram

3 Journal of Science Technology Engineering and Management-Advanced Research & Innovation Vol. 1, Issue 1, January 2018 Firstly, the initial stage which is the input stage, has been designed by using the L type matching. This L type matching represents the connection of the components placed in the schematic. Secondly, the block diagram shows the amplifying stage, in which a Common Emitter Topology is being used. This is the positioning of the BJT that is connected to the source which will be shown in fig.3. Lastly, the third block shown in the block diagram represents the output stage of the amplifier, where L type matching is also being used. These three stages will be explained in detail in the next section. 3.2 Working Principle Fig.2 Flow Chart Fig.2 shows the first stage that is needed to be designed, which is the Input Matching network stage. In LNA, the intension of using a matching network is to transform the input and output impedance to 50ohm impedance. Term1 and Term2 are set to be 50ohm (Fig.3). One of the objectives set in this work is to have a low noise figure and hence, to attain a low noise figure for the proposed LNA, an input matching network is designed. Next, the power is being supplied to the BJT from the initial input stage and reaching the DC-biasing network section. Every BJT has its own characteristics and stability. To allow the BJT to operate from its operating point and to keep the overall system stable, the DC-biasing network is introduced in the circuit of the proposed LNA [8]. This is the second stage of the LNA, where the amplification of the incoming signal occurs. Once the signal is amplified, few parameters are taken into consideration like, the temperature and unwanted noise from the input stage [8]. Then comes the output matching network and the load. To attain maximum power, the output matching network is normally designed. Input and output matching network is designed to match the source impedance with the varying load impedance. For varying loads, the output network, matches the load impedance. This impedance matching is carried out as to a means to overcome stretching wave s phenomena at the output, which is caused by internal or external interference (noise). 25

4 Wide-Band Low Noise Amplifier for LTE Applications Veeriayah Thangasamy 3.3 Overall Schematic Diagram Figure 3: Overall Schematic Circuit Figure 3 demonstrates the overall circuit schematic that is designed by using the software Advance Design System ADS. The circuit is backed up with four parameters linking together for various simulations that will be carried out in the section of Simulation & Results. Term 1 and Term 2 in the circuit defines the S-parameter model that is placed in the schematic. Term 1 acts as the source resistance RS of the circuit and term 2 acts as the load resistance RL of the circuit. There is an I-Probe component connected at the top of the circuit having one positive and one negative connection. The negative part of the I-Probe is connected to the collector of the BJT and the positive part of the I-Probe is connected to the DC-biasing network. The purpose of this I-Probe is to measure the current throughout the circuit. As it can be observed from figure3, the capacitor C1 is connected to the inductor L1. The connection of these two components are known are the L-type matching since the capacitor and inductor make a L shape. Capacitor C1 is set to be 1pF and the inductor L1 is set to be 2.1 nh, where it is responsible for determining the input reflection coefficient. The topology used in this wide bandwidth design is the Common emitter design. Common emitter topology is ideal to build the wide bandwidth LNA, this is determined by observing the emitter section of the BJT is connected the voltage source, thus this is known as common emitter topology.

5 Journal of Science Technology Engineering and Management-Advanced Research & Innovation Vol. 1, Issue 1, January 2018 Common emitter is ideal due to its ability to deliver the highest power gain when it is combined with moderate voltage and moderate current gain. Hence, it is widely used in amplifiers on communication receivers [5]. Inductor L5 is connected to the capacitor C7 in a L shape manner. Inductor L5 is set to be 3nH and the capacitor C7 is set to be 4.8 pf. Since the initial input stage is L-type matching and the output stage is L- type matching hence it can be deduce that the overall circuit is L-L type matching circuit.one of the key factors of designing a wide bandwidth LNA is the biasing network design. Network biasing is essential for the operating point of the transistor (BJT). For the low noise amplifier s stability to be maintained, transistor s characteristics need to be taken under consideration. BJT is used in controlling the switch of the current in the proposed wide bandwidth LNA [8]. 4. Simulation and Results This section will demonstrate and explain the results that are obtained for the proposed wide bandwidth LNA. There are five simulations that are carried out in this work which are: - S11 (Input stage) S21 (Gain) S22 (Output stage) Stability Noise Figure NFmin 4.1 S11 Input Stage Figure 4: S11 Input Stage Firstly, the simulation of the input stage S11 is shown in figure 4. S11 determines the input reflection coefficient. From the graph of fig.5, considering the maximum frequency to be 2.15GHz, the input reflection coefficient is dB. 4.2 S21 Gain 27

6 Wide-Band Low Noise Amplifier for LTE Applications Veeriayah Thangasamy Figure 5: S21 Gain (bandwidth) Secondly, Figure 5 shows the gain that is attained at the amplification stage. In this graph of S21, it can be observed that the bandwidth of the low noise amplifier can be determine by neglecting 3dB from the peak on the overall graph. In this case, the highest peak of the gain attained is the M7 indicator stating that the gain is dB. Removing 3dB from this peak value, gives the minimum draw line so that the overall bandwidth can be calculated. From the graph the bandwidth deduced is 0.75GHz-2.15 GHz. Thus, fulfilling the requirement of the wide bandwidth characteristic. 4.3 S22 Output Stage Figure 6: S22 Output Stage Thirdly, figure 6 illustrates the simulation of the S22. S22 is defined as the output reflection coefficient, hence, from the graph it can be deduced that the output reflection coefficient at 2.15GHz is dB. 4.4 Stability Factor

7 Journal of Science Technology Engineering and Management-Advanced Research & Innovation Vol. 1, Issue 1, January 2018 Figure 7: S22 Stability Factor Next, Figure 7 demonstrates the simulation graph of stability. Even though the proposed wide bandwidth LNA has no feedback and stability per say, the stability simulation needs to be carried out to determine if the LNA is stable or not at the set parameters. From figure.7, it can be determined that the value of the frequency set is 2.15GHz and the stability factor attained is Anything above unity is considered as unconditionally stable. 4.5 Noise Figure Lastly, figure 8 determines the simulation carried out for noise figure NF. Noise figure is one of the most vital parameter that is needed for an LNA to be acceptable. Since this proposed amplifier is a low noise amplifier hence, the one of the key parameter is to keep monitoring the noise that the overall system produced. In this case, the frequency set is at 2.15GHz, and from there the noise figure can be determined that the noise attained is 2.114, which is considered as low noise in the system. The gain attained by the L-L type matching without stability and feedback is 1.4GHz, which clearly determines that the system is wide bandwidth. The stability and noise figure attained was and respectively. It can be deduced that this circuit is conditionally stable as well as has a lower NF than the one with feedback and stability. 4.6 Testing the Proposed Circuit Figure 8: Noise Figure NF 29

8 Wide-Band Low Noise Amplifier for LTE Applications Veeriayah Thangasamy Table 1. Testing circuit with different matching Test Input Output Bandwidth Stability NF 1 L (RLC) L (RLC) 1.1 GHz dB 2 Π (RLC) Π (RLC) 1 GHz dB 3 Π Match Π Match 0.97GHz dB 5. Conclusion Radio frequencies technology have been advancing ever since telecommunication sector have been demanded. These days communication via radio frequency is vital, from smart phones to major army communications. The fundamental to Low noise amplifiers is the consistency and the minimum distortion that occurs while the signal is being amplified. Furthermore, L-L type matching for input and output without RLC circuit for stability and feedback was used. The bandwidth was calculated from the graph attained for gain (see fig.5), which is 1.4GHz. This clearly determines that the system is wide bandwidth thus, one of the objective has been fulfilled. Next is the stability of the circuit which was attained to be hence, the system is unconditionally stable. Lastly, the noise figure obtained was 2.114dB which is very applicable in this system References [1] ESLAMIFAR, O. AND SHIRAZI, R. (2014) Design an Ultra-Wide Band Low Noise Amplifier for Use in WLAN Applications. The 22nd Iranian Conference on Electrical Engineering. p [2] HIDAYOV, O., LEE, S., HAN, S., YOON, G. AND NAM, N. (2013) GHz wideband CMOS low-noise amplifier for LTE application. Electronics Letters. 49 (23). p [3] KUMAR, R. (2012). Design and Noise Optimization of RF Low Noise Amplifier for IEEE Standard A WLAN. International Journal of VLSI Design & Communication Systems. 3(2). p [4] LU, Y., YANG, S. AND CHEN, Y. (2010). The Design of LNA Based on BJT Working on GHz. In 2nd International Conference on Signal Processing Systems. Beijing. [5] MURTY, N. AND RAO, M. (2013). Analytical study of substrate parasitic effects in common-base and common-emitter SiGe BHT amplifiers. Journal of Microwaves, Optoelectronics and Electromagnetic Applications. 12(1). p [6] STATISTA.COM. (2017). Statista - The Statistics Portal for Market Data, Market Research and Market Studies. [online] Available from: [Accessed 5 Mar. 2017]. [7] VAN HOI, T., XUAN TRUONG, N. AND GIA DUONG, B. (2015). Design and Fabrication of High Gain Low Noise Amplifier at 4 GHz. International Journal of Engineering and Innovative Technology. 4(7). p [8] VIMAL, S. AND MAHESHWARI, D. (2016). Design and performance improvement of a low noise amplifier with different matching techniques and stability network. International Journal of Engineering Research & Science. 2(3). p. 1-9.