Ku band Low Noise Amplifier (LNA) Design

Abstract

With rapid technological advancement in the communication network system, there is equivalent increased demand for the high signal to noise ratio (SNR) in communication systems. However the challenge for having an effective SNR in communication systems has been attributed to the low Q inductors, high bandwidth frequencies, high gloss, and high noise figures in the receiver systems. To overcome this challenge, we took upon ourselves as group two members to analyze low loss transmission lines and high Q with their respective characteristics. The outcome of the analysis was to develop a design of an improved Low Noise Amplifier with an on-chip inductor to replace the commonly used series and regeneration inductors in the communication systems. The developed design incorporated the use of source inductor feedback technique with high Q low loss transmission line matching network systems with a frequency range of 12-16 GHz, signal gain of over 25 dB and noise figure of over 8 dB.

Project motivation

Low Noise Amplifier LNA serves a crucial purpose in the receiving end of every transmission and communication systems. In communication systems, the main purpose of the Low Noise Amplifier is t0o boost the received or incoming signals and at the same time adjusting the noise to a favorable level to enhance clarity in communication systems. The basis of any active receiver is a properly functioning Low Noise amplifier and the general performance of RF is determined by the Low Noise Amplifier. Therefore for effective signal transmittance and receiving in communication systems requires an effective low noise amplifier. The schematic structure of the signal received by an antenna through to the AF amplifier and then output is as shown in figure 1.

The flow of signal from the receiver to output

The design of a Low Noise Amplifier is justifiable as it provides a replacement for the use of GaAs Bipolar design systems, these components cannot easily be integrated and the quite costly too. With the emergence of new technology, this project aims at designing a more feasible LNA that incorporates RF circuit designs with CMOS technology.

This design uses the latest MOS device that is capable to translate into a low noise figure with increased gain and higher performance efficiency. The aim and scope of this design are to provide a more efficient Low Noise Amplifier for the use of Ku Band to ensure a fine-tuned communication network.

Design specification and design parameters

Summary of design

Ku-Band LNA and Its Application

Ku-band LNA is the 12-16 GHz is the range of microwave frequencies, the expression Ku signifies K-under originally derived from German word Kurz-unter this means that the band directly below the K-band. The design specification of the frequency for the design range between 12-16 GHz. The design needs to be to the formal definition of radar frequency band nomenclature as outlined in the 521-2002 IEEE Standards. The advantage of the Ku band unlike C-band is that it has no restrictions in power hence perfect in avoiding any form of interference to the terrestrial microwave systems. With Ku-band in the design of LNA, it is quite easy to downlink and uplink power in the system. The outstanding application of the Ku-band Low Noise amplifier is in satellite communication systems that are fixed to the broadcast services. They are used in the international space communication stations and a space shuttle for NASA’s Tracking Data Relay Satellites.

The initial phase of LNA design is the receiver front-end, as it is the section that increases the signal power from antenna while allowing less noise in by the same LNA. Generally, the structure of the low noise amplifier is made of impedance matching blocks for both input and output (IMN & OMN) sections, and the amplifying block (AMP). Input/output matching networks are for performing part of filters, noise performance optimization, and provision of input/output stability. In the design, the matching elements are passive elements consisting of inductors, resistors, strip lines, and load impedances.

Low Noise Amplifier Block Diagram

On-Chip Inductor

The Low Noise Amplifier design incorporates the use of an on-chip inductor technique to enhance the process of spectral noise reduction. The inductor series resistance contributes to the spectral noise current thus the inductor provides a perfect matching at the low noise amplifier input and output. The use of an on-chip inductor in the design reduces the effects of parasitic capacitance at the input of the low noise amplifier since it incorporates the MOSFET in its design. The design deference in this design is the series inductor and degeneration inductors are replaced by the use of a compact on-chip inductor thus improving the LNA’s performance efficiency.

Compliance matrix

(can only be generated from the actual design)

Competitors product analysis

Amplifier architecture

Low Noise Amplifier is typically an electric device that comprises of passive and active components. The passive elements of LNA are basically used for input/output matching processes and biasing of the system, while active elements perform the primary functions of input signal amplification with the addition of minimum noise for clarity in communication. LNA’s design consists of 0of a wide range of Radio Frequency transmission that facilitates the amplification and improved performance of the low noise amplifier. The design comprises short channel devices that provide high mobility thus assuring the best possible gain and enhanced noise performance.

Based on other LNA design philosophies, the design also included a single stage common low source noise amplifier that applies GaAs MOSFET and the performance optimization facilitated by a combination of input/output matching networks.

Detailed circuit schematic

The designed LNA incorporated circuit systems with matching networks designed by mean s of a hybrid lumped-distributed topology. The topology uses transmission lines, MIM type capacitors, and short-circuited stubs. The circuit also had two bigger stand-by capacitors that could be used whenever needed to obtain a low-value capacitance for minimizing any harmful effects of the eventual variation process. The used matching networks in the circuit are designed from ideal components with the aim of using the least number of elements as possible. All other network systems were designed through an L-shunt and C-series topology to allow the use of DC-lock on the radio frequency RF path and higher impedance for both source impedance inductor and the matching networks.

Schematic diagram of the designed LNA

Equivalent  model diagram

Model Applied

The Low Noise Amplifier was designed and developed using CADENCE 0.13um CMOS model technology.

EM Analysis Approach

S-Parameters

Since the design is based on a two-port network, there are various ways to represent the system’s behavior. For instance in this design. At Low frequency, Y, Z, H, and ABC parameters are applied. S-parameters play a critical role in the radio frequency RF system and provide the most effective parametric approach in RF systems as compared to either H-parameters or Z-parameters.

In our design we opt to use s-parameters since they provide the best way to measure reflected and incident wave power in a two-port network system for the radiofrequency block. The low noise amplifier design designated S₁₁ and S₂₂ for input and output impedance matching respectively. Then S₁₂ and S₂₂ designate the measure isolation between input/output ports and measure of the amplification gain of the amplifier respectively.

Two-port Network

The S-parameter of SDC low noise amplifier

OIP3 and PSAT curves

(can only be generated from the actual design)

Final Layout

(can only be generated from the actual design)

Improvements for future revision suggestions

For future consideration, the design of low noise amplifiers should incorporate the use of D01GH technology. This technology will facilitate the extraction of higher strength frequency signals from DC-40 GHz through a common noise temperature model. The temperature model provides equivalent thermal noise sources that are assigned to drain gate terminals hence providing improved performance efficiency.

For the improved performance and for future e designs four-stage topology needs to be incorporated in the design of the layout. This would help in compensating the losses during transmission and ensures a satisfactorily high gain request. And double polarization scheme also needs to be considered in the design to enable the designed Ku-LNA amplifier to have complete independence bias and drain for every device involved.

Conclusion

The designed low noise amplifier was achieved through a consultative discussion among group two members and reached a consensus that the design is based on Ku-band with a frequency range of between 12-16 GHz, gain of greater than 25 dB and a noise figure of 2 dB. The idea of developing this Low Noise amplifier was motivated by the fact that most communication systems, for a long time had noise regulation challenges hence affecting communication between substations. Therefore the design of an improved low noise amplifier was timely and crucial in the communication line as it provided enhanced clarity and performance efficiency in communication networks. The objective of the group to design an n improved LNA was meet based on the design specifications of the LNA and all were achieved after testing the design.

References