Design of Low Noise Amplifier at 8.72 GHZ

Transcription

1 MIT International Journal of Electronics and Communication Engineering, Vol. 3, No. 2, August 2013, pp Design of Low Noise Amplifier at 8.72 GHZ Dwijendra Parashar M.Tech (Communication Engg.) Scholar Deptt. of Electronics and Communication Shobhit University, Meerut, UP, INDIA Nisha Chugh M.Tech (VLSI Design) Assistant Professor Deptt. of Electronics and Communication Shobhit University, Meerut, UP, INDIA ABSTRACT LNA design presents a considerable challenge because of its simultaneous requirement for high gain, low noise amplifier, good input and output matching and unconditional stability at the lowest possible draw from an amplifier. Although gain, noise figure, stability, linearity, input and output matching are equally important; they are independent and do not always work in each other s favor. We can say that a Low Noise Amplifier is a key component in the RF front end receiver. This poses challenges in terms of meeting high gain, low noise figure, good linearity and lower power consumption requirement. In this paper we are designing Low Noise Amplifier at supply Voltage is 1.8V, Supply Current is 2.66 ma and frequency is 8.7GHz. In the communication market the demand of LNA is increasing with increasing the market of Cell Phones, GPS, and Bluetooth etc, which is used in day to day life. A Low Noise Amplifier is the basic building block of any communication system. It is placed at the front end of a radio receiver and works as an electronic amplifier to amplify the received signals to acceptable levels with minimum self generated additional noise while radio receiver composed of amplifier, mixer and filter. Keywords: Cadence virtuoso (R) schematic editor XL tool, Low-noise amplifier (LNA), Radio Frequency (RF) and CMOS, Single stage amplifier, 8.72 GHz frequency. I. INTRODUCTION In the communication market the demand of LNA is increasing with increasing the market of Cell Phones, GPS, and Bluetooth etc, which is used in day to day life. A Low Noise Amplifier is the basic building block of any communication system. It is placed at the front end of a radio receiver and works as an electronic amplifier to amplify the received signals to acceptable levels with minimum self generated additional noise while radio receiver composed of amplifier, mixer and filter. The first part is an LNA which is the most important part of the receiver. The main function of LNA is to amplify extremely low signals without adding noise thus preserving required signal to noise ratio at extremely low power level and large signal levels and provides first level of the amplification that can be received by the receiver is the receiver s sensitivity also. It amplifies the received signal without introducing any distortions hence eliminating channel interference. The dynamic range of the receiver which is the difference between the largest possible received signal and the small possible received signal is defining the quality of receiver chain. The largest signal that can be received by the receiver establishes an upper power level limit that can be handled by the system while preserving voice or data quality. The reasons behind using LNA are signal coming from the antenna is very small, amplification of the signal is needed, reasonable or minimum power consuming gain, noise figure, non linearity and impedance matching are the most important parameters in LNA design. An LNA is a design that minimizes the noise figure of the system by matching the device to its noise matching impedance. As we see the role of LNA in Radio receiver that LNA amplify received signal, boost the desired signal power, reduced noise in the receiver, increased gain in the receiver. An amplifier which uses is the single stage amplifier. This paper indicates the background information of radio receiver. In this configuration first we design a low noise amplifier, second mixer and third filter. The first stage of a receiver is typically a low-noise amplifier (LNA), whose main function is to provide enough gain to overcome the noise of subsequent stages (for example, in the mixer or IF amplifier). Aside from providing enough gain while adding as little noise as possible, an LNA should accommodate large signals without distortion, offer a large dynamic range, and present good matching to its input and output, which is extremely important if a passive band select filter and imagereject filter precedes and succeeds the LNA, since the transfer characteristics of many filters are quite sensitive to the quality of the termination. LNA Schematic is a basic circuit design to represent the elements of the system. LNA Schematic combines both of the Common and Cascade LNA. This is used to find out the results of LNA.

2 MIT International Journal of Electronics and Communication Engineering, Vol. 3, No. 2, August 2013, pp II. BACKGROUND INFORMATION OF RADIO RECEIVER In radio communications, a radio receiver is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. The antenna intercepts radio waves (electromagnetic waves) and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information. The receiver uses electronic filters to separate the wanted radio frequency signal from all other signals, an electronic amplifier to increase the power of the signal for further processing, and finally recovers the desired information through demodulation. The information produced by the receiver may be in the form of sound (an audio signal), images (a video signal) or data (a digital signal) [2]. A radio receiver may be a separate piece of electronic equipment, or an electronic circuit within another device. Devices that contain radio receivers include television sets, radar equipment, two way radio, cell phone, wireless computer networks, GPS navigation devices, satellite dishes, radio telescope, Bluetooth enabled device, garage door openers, and baby monitors. Alexander Stepanovich Popov designed and implemented the first radio receiver in It was based on electromagnetic waves, which were proven to exist by James Clerk Maxwell only a few years earlier in It took only a few more years until the first radio system was able to transmit communications across the Atlantic in In the time between then and the present day, the radio receiver has seen a great many technological advances. One of the most significant advances was the invention of the super heterodyne, or superhet, receiver. The receiver demodulates and decodes the channel output to recover the original information to the source. Once demodulated, the channel decoder, which is typically a filter matched to the channel encoder, is used to recover one sample estimate per symbol of the channel code word. The channel encoder estimate the digital source code word, which is then converted to an estimate the original data from the source decoder. Heterodyne architecture is probably the most commonly used receiver in current commercial receiver implementation. The low noise amplifier plays a key role in this architecture. The main objective of the super heterodyne receiver is to produce an intermediate frequency (IF) by the process of heterodyning or beating. This can be accomplished when two frequencies are mixed to produce the beat frequency. Figure 1: Architecture of a heterodyne receiver using LNA The first stage of a receiver is typically a low-noise amplifier (LNA), whose main function is to provide enough gain to overcome the noise of subsequent stages (for example, in the mixer or IF amplifier). Aside from providing enough gain while adding as little noise as possible, an LNA should accommodate large signals without distortion, offer a large dynamic range, and present good matching to its input and output, which is extremely important if a passive band select filter and image-reject filter precedes and succeeds the LNA, since the transfer characteristics of many filters are quite sensitive to the quality of the termination. Figure1 shows the architecture of heterodyne receiver using LNA. The band-select filter before the LNA rejects the out-of-band interference. The image reject filter (preselected) after the LNA attenuates the image which is 2ωIF away from the desired band [12]. III. LOW NOISE AMPLIFIER The low noise amplifier is an electronic amplifier used to amplify possibly very weak signals (for example, captured by an antenna). It is usually located very close to the detection device to reduce losses in the feedline of any an amplifier. This active antenna arrangement is frequently used in microwave systems like GPS, because coaxial cable feed line is very lossy at microwave frequencies, e.g. a loss of 10% coming from a few meters of cable would cause a 10% degradation of the signal-to-noise ratio (SNR). An LNA is a key component which is placed at the front-end of a radio receiver circuit. Using an LNA, the effect of noise from subsequent stages of the receive chain is reduced by the gain of the LNA, while the noise of the LNA itself is injected directly into the received signal. Thus, it is necessary for an LNA to boost the desired signal power while adding as little noise and distortion as possible, so that the retrieval of this signal is possible in the later stages in the system. Low noise amplifiers represent one of the basic building blocks of the communication system. The purpose of the LNA is to amplify the received signal to acceptable levels while minimizing the noise it adds. A good LNA has a low NF (like 1 db), a large enough gain (like 20 db) and should have large enough inter modulation and compression point (IP3 and P1dB). Further criteria are operating bandwidth, gain flatness, stability and input and output voltage standing wave ratio (VSWR). In the design of LNA another consideration is to choose the single ended or differential architecture. The single ended configuration provides a lower noise figure whereas both the branches contribute to the noise at the output in differential configuration. Additionally, the current in each transistor in the differential circuit is half that of the single-ended topology. The transit frequency of the device would be smaller for the differential circuit, which degrades the noise figure of the circuit. But the differential topology can provide an increased output dynamic range and also a better tolerance to commonmode interferences in the circuit. Due to the differential

3 MIT International Journal of Electronics and Communication Engineering, Vol. 3, No. 2, August 2013, pp nature of the circuit the effect of the parasitic inductance of the ground pin is reduced. There are several advantages in using a differential design. Firstly, the virtual ground formed at the tail removes the sensitivity to parasitic ground inductances, which makes the real part of the input impedance purely controlled by the source degeneration inductance (Ls). Secondly the differential amplification of the signal ensures an attenuation of the common mode signal, in most of the system this common mode signal will be noise. Thirdly, the use of Gilbert mixers and image rejection schemes require to be fed from a differential source [10]. Figure 2: Resistive terminated LNA LNA is the first stage after antenna in radio receiver. The LNA is accountable for providing enough gain to the signal with the bare minimum distortion. Cadence Virtuoso (R) Schematic Editor tool has been used to simulate the designed LNA and is proved to have better noise figure as well as input matching. The designed LNA provides the low S 11, S 22 and noise figure. The high gain achieved and the response over the band of interest is almost flat. Where Г in = (b 1 /a 1 ) = S 11 + (S 12 S 21 Г L /(1 S 22 Г L )) (1) Г out = (b 2 /a 2 ) = S 22 + (S 12 S 21 Г L /(l S 11 Г S )) (2) Г L = (Z S Z 0 )/(Zs + Z 0 ) (3) Г S = (Z L Z 0 )/(Z S + Z 0 ) (4) If the input and output are simultaneously complex conjugate matched, i.e. Г in = Г* S and Г out = Г* L, the amplifier has maximum power transfer. Achieving the simultaneous complex conjugate matching condition is not easy. A special case is when a unilateral device where S 12 is practically zero, then Г in = S 11 and Г out = S 22. If the input and output are decoupled from each other, matching can be done at the input and output separately. The main challenge of LNA design lies in the design of the input/output matching network to render Γ in and Γ out close to zero so that the LNA is matched to the source and load ports. With the knowledge of a generic LNA model, Figure 3 shows the test bench for a single ended LNA. The capacitors are DC decoupling capacitors that eliminate the effect of the port resistor on the LNA s DC bias. They are added when necessary. IV. TEST BENCH FOR SINGLE ENDED AND DOUBLE ENDED LNAS The scattering parameters or S-parameters are widely used in microwave and RF circuit analysis. S parameters are used to model and characterize a n port linear network. The linear equations describing the behavior of the two-port network using S parameters. There are two criteria that affect the performance gain of any RF amplifier: the RF transistor itself and the input output matching network. A simplified block diagram is shown in Figure 5.2. The amplifier is characterized by its S-parameters and terminated by the source and load impedance Zs and Z L, respectively. S 11 and S 22 are the input and output reflection coefficients. The load of the next stage follows the output matching network. The input and output reflection coefficients Г in and Г out for a two-port network are Figure 3: Test bench for a Single-Ended LNA Figure 4 shows the test bench for a differential LNA. The baluns used in the test bench are three-port devices. The baluns convert the input signal-ended signals to the differential signals. They also perform the resistance transformation. V. LNA DESIGN AND SPECIFICATION The Low Noise Amplifier (LNA) always operates in Class A, typically at 15-20% of its maximum useful current. Class A

4 MIT International Journal of Electronics and Communication Engineering, Vol. 3, No. 2, August 2013, pp G A = (7) G A = (8) Figure 4: Test bench for a Double-Ended LNA is characterized by a bias point more or less at the center of maximum current and voltage capability of the device used, and by RF current and voltage that are sufficiently small relative to the bias point that the bias point does not shift. The smallest signal that can be received by a receiver defines the receiver sensitivity. The largest signal can be received by a receiver establishes the upper power level limit of what can be handled by the system while preserving voice or data quality [11]. The dynamic range of the receiver, the difference between the largest possible received signal and the smallest possible received signal, defines the quality of the receiver Chain. (a) Power consumption and supply voltage Most of the LNAs are operating in Class-A mode, power consumption is easily available by multiplying the DC supply voltage with the DC operating point current. Total power dissipation for an operating LNA circuit should be within its design budget. Selecting the operating point is a critical stage of LNA design which affects the power consumption, noise performance, IP3, and dynamic range. (b) Gain There are three types of power gain that commonly used in LNA design. G T, transducer power gain G P, operating power gain G A, available power gain Transducer power gain G T is defined as the ratio between the power delivered to the load and the power available from the source [12]. G T = (5) G T = (6) Operating power gain G P is defined as the ratio between the power delivered to the load and the power input to the network. G P = G P = Available power gain G A is defined as the ratio between the power available from the network and the power available from the source. Several gain definitions exist for an amplifier. Power gain (G) characterizes the actual power amplification of an amplifier, and it is defined by: Power Gain = (9) Available power gain (G A ) shows the maximum possible power amplification of the amplifier. For IC implementations, the LNA input is interfaced offchip and is usually matched to the specific impedance (50 Ω or 75 Ω). An LNA s output is not necessarily matched when it directly drives on-chip blocks such as mixers. This situation is usually characterized by LNA s voltage gain or transducer power gain [13]. (c) Noise Performance- The noise performance of the RF amplifier is represented by its noise factor or noise figure. The noise factor accounts for the degradation of the signal s SNR due to the amplifier [16]. It is defined as the SNR at the input of the network divided by the SNR at the output of the network: F = (SNR in /SNR out ) (10) Where SNR in and SNR out are the SNRs at the input and output of the amplifier, respectively. The noise factor represents the signal s quality in terms of noise before and after the network. The noise figure is same as the noise factor expressed in db. NF (db) = 101ogF (11) Noise figure shows the degradation of signal s SNR due to the circuits from that the signal passes. The LNA should not bring too much noise to the following part of the receiver in order to select and amplify the weak signals, so keeping a low NF is a crucial process when designing the LNA. According to the n-stage network Friis equation: NF Total = 1+ (NF 1-1) + + L + VI. LNA SCHEMATIC AND SIMULATION (12) The cascade of CS stage and a CG stage is called cascode. This combination may have one or more of the following characteristics: higher input-output isolation, higher input impedance, high output impedance, higher gain or higher bandwidth.

5 MIT International Journal of Electronics and Communication Engineering, Vol. 3, No. 2, August 2013, pp Figure 5: Cascode LNA schematic A. Transient and DC Response The curve of Transient Analysis and Transient Response, DC Response. Transient Response in the form of input and output produces waveforms [16]. For Low Noise Amplifier supply Voltage is 1.8V, Supply Current is 2.66 ma, Frequency is 8.72 GHz, where total output power is multiplication of Current and Voltage and calculated is 4.7mW. There are three Types of Analysis First is DC Analysis Second is Transient Analysis third is AC Analysis. DC Analysis defines the Operating Point of the system. Transient Analysis is in reference to the circuit and AC Analysis is directed for Frequency and gain. Figure 7: Power Gain As in graph shown power gain 16.39dB at frequency 8.72 GHz.For amplification we know the parameter that if the gain is greater than 0dB means amplification exists in the circuit. Usually amplification is very high as we required in the circuit. The graph is obtained between frequency and gain. Also Current gain, voltage gain and power gain can be measured. In the Cadence Tool We Find the Gain by the Calculator. C. S Parameter The scattering parameters or S-parameters are widely used in microwave and RF circuit analysis. S-parameters are used to model and characterize a n-port linear network. Figure 6: Transient and DC Response B. Power Gain Power gain shows the maximum possible power amplification of the amplifier. For IC implementations, the LNA input is interfaced off-chip and is usually matched to the specific impedance (50 Ω or 75 Ω). An LNA s output is not necessarily matched when it directly drives on-chip blocks such as mixers. This situation is usually characterized by LNA s voltage gain or transducer power gain [13]. Power Gain = Figure 8: S 11 and S 22 Parameter

6 MIT International Journal of Electronics and Communication Engineering, Vol. 3, No. 2, August 2013, pp in cadence tool, the design technique we used is 0.18 µm UMC Technology. UMC is the United Microelectronics Corporation is Taiwan s First semiconductor company. We design the LNA at frequency 8.72 GHz. The reason of using this range of frequency is the more availability of this range in the cadence tool and benefits to work with this frequency range are lower noise, lower power dissipation, higher gain, reasonable output power and gain. REFERENCES VII. LNA RESULT Figure 9: S 12 and S 21 Parameter In the Simulation Results we have found the different parameters for Low Noise Amplifier. These parameters Supply voltages, Current, Power Dissipation, Frequency, Temperature, AC Gain, Noise Figure given details in the Table 1 shown below: Table 1: Design Specs and calculated parameter. S.N. Parameter LNA final result 1 Supply Voltage 1.8V 2 Current 2.66 ma 3 Power Dissipation 4.7 mw 4 Frequency 8.72GHz 5 Temperature 27 C 6 Power Gain 16.39dB 7 S dB 8 S dB 9 S dB 10 S dB VIII. CONCLUSION The Low Noise Amplifier is the essential part of any RF Receiver. From the experiences of the operation that performed [1] Communications Receivers, Third Edition, Ulrich L. Rohde, Jerry Whitaker, McGraw Hill, New York, 2001, ISBN [2] Superhet Receiver.pdf... Crystal Radio and Superheterodyne Receiver by Ben Godfrey. [3] MOS Inverter, Digital Electronics INEL 4207 by Prof. Manuel Jimenez with contribution by Rafael A. Arce Nazario. [4] Buscar copias de Dr. Jimenez en Reproducciones ($1-$2) Digital circuits using MOS transistors. [5] H.C. Lin and L.W. Linholm, An optimized output stage for MOS integrated circuits, IEEE Journal of Solid-State Circuits, Vol. 10, pp , April [6] R.C. Jaeger, Comments on An optimized output stage for MOS integrated circuits, IEEE Journal of Solid-State Circuits, Vol. 10, pp , June [7] LNA Design Using Spectra RF Application Note Product Version 5.0 December 2003 September by Cadence Design Systems. [8] R. Ramazan, Tutorial simulation of LNA, Linkoeping University, Sweden, [9] The Design of CMOS Radio Frequency Integrated Circuits, Thomas H. Lee. Cambridge University Press, [10] B. Razavi, Design of Analog CMOS Integrated Circuits, McGraw-Hill, [11] T.H. Lee, the Design of Cmos Radio Frequency Integrated Circuits, Cambridge University, [12] Sungkyung Park and Wonchan Kim, Design of a 1.8 GHz low-noise amplifier for RF front-end in a 0.8, Consumer Electronics, IEEE Transactions on, Vol. 47, No. 0098, [13] D.K. Shaeffer, T. Lee, A 1.5V, 1.5GHz CMOS Low Noise Amplifier, IEEE Journal of Solid-State Circuits, Vol. 32, No. 5, May [14] Worcester Polytechnic Institute. Cadence Design Tools Tutorial. [15] ECE531 Cadence Simulation Tutorial by Haibo Wang Southern Illinois University Carbondale. [16] B. Razavi, CMOS Technology Characterization for Analog and RF Design, IEEE Journal of Solid-State Circuits, Vol. 34, No. 3, March

7 MIT International Journal of Electronics and Communication Engineering, Vol. 3, No. 2, August 2013, pp [17] Adel S. Sedra and Kenneth C. Smith, Microelectronic Circuits, 1987, Holt, Rinehart and Winston, Inc. [18] Zhang H.; Chen Gui; (2008): Design of a fully differential CMOS LNA for GHz UWB communication systems. [19] Pablo M.G.; Mohammad H. (2006): Design of a CMOS Low- Noise Amplifier,Stanford University [20] J.P. Silver: MOS Differential LNA design Tutorial. [21] Reza Molavi (2005): On the design of Wideband CMOS Low- Noise Amplifiers. [22] Reinhold Ludvig, Pavel Bretchko: RF Circuit Design Theory and Applications, Prentice Hall 2000, ISBN [23] Microwave Transistor Amplifiers, Guillermo Gonzalez, Prentice Hall, [24] P.R. Gray, P.J. Hurst, S.H. Lewis, R.G. Meyer, Analysis and Design of Analog Integrated Circuits, 4th edition, John Wiley and Sons, [25] Ahmad Saghafi; Abdolreza Nabavi (2006): An Ultra-Wideband Low-Noise Amplifier for 3 5-GHz Wireless Systems The 18 th International Conference on Microelectronics (ICM) 2006.