SDARS Receiver Front-End

Transcription

1 SDARS Receiver Front-End Project Proposal Keven Lockwood Dr. Prasad Shastry December 9, 2010

2 Project Summary This project focuses on the front-end receiver design for the Satellite Digital Audio Radio Service (SDARS). The SDARS is used primarily for entertainment broadcasting from orbital satellites and received by modules commonly found on modern automobiles. In particular, this project will focus primarily on the antenna design and its paired low noise amplifier (LNA), which largely affects the signal-to-noise ratio (SNR) and hence the sensitivity of the receiver. The SNR determines the quality of the signal received to produce quality audio, which largely depends on the noise figure of the LNA. The active antenna (passive antenna + LNA) will be designed to produce the best quality of signal. In short, the main goal of this project is to design an active antenna that will receive SDARS wireless transmissions. Project Goals Design and perform CAD simulations on a linearly polarized, proximity coupled patch antenna which meets SDARS specifications Design and perform CAD simulations on a proximity coupled patch antenna configured for Left-Hand Circular Polarization (LHCP), which meets SDARS specifications Fabricate the Antenna in-house Research and purchase a low-noise amplifier in a prefabricated surface mount package to integrate with the antenna Fabricate a test board and measure the gain and noise figure characteristics of a purchased LNA to ensure it meets SDARS specifications Test the antenna experimentally to determine that it meets performance specifications Construct the active antenna (antenna plus LNA) and test its performance. Replace the manufacturer s provided active antenna system with the fabricated version and test overall system. High-level System Block Diagram The high-level over-all system block diagram is shown below in figure 1-1. The active antenna components will be connected using a microstrip line, and the connection to the receiver will be accomplished through a coaxial cable. Active Antenna Antenna Low-Noise Amplifier Sirius Radio Receiver Figure 1-1: Overall System Block Diagram

3 Antenna The Antenna is the passive portion of the paired antenna and LNA, which is considered to be the active antenna. The antenna receives the audio modulated, LHCP signal from the SDARS orbiting satellite. It then feeds the signal via microstrip line into an integrated LNA for amplification. Simulations shall be done using in-house software, fabricated, and tested to determine actual performance. The Antenna must meet several requirements to successfully receive the satellite signal: It shall receive in the frequency band from 2320 MHz to MHz (a bandwidth of 12.5 MHz) The VSWR of the antenna output module shall be a maximum of 2:1 It shall be Left-Hand Circularly Polarized (LHCP) (25 o 90 o elevation angle) It shall have a passive gain of 3 dbic. It shall be designed as a rectangular-shaped patch antenna Microstrip line shall connect the antenna to the LNA. Low-Noise Amplifier (LNA) The LNA is responsible for amplifying the low power signal received by the antenna while introducing minimal noise to the system. Minimal noise is necessary to achieve an acceptable Signal-to-Noise Ratio (SNR) for quality sound, which is contributed primarily by this component. The LNA must meet the following requirements: The output of the LNA shall be fed via microstrip line to the coaxial cable connector. It shall then be sent via coaxial cable to the Sirius Radio Receiver. The LNA shall have a gain between 25.5 and 29.5 db, with a total antenna active gain between 28.5 and 32.5 db. The LNA shall have a noise figure less than or equal to 0.9 db when a 24 db attenuator is connected on its output. It shall operate in the frequency range 2320 MHz to MHz. The LNA shall be integrated using a prefabricated surface mount package from an outside source. If time permits, a LNA may be fabricated in-house and integrated with the antenna. The output impedance Z o of the active antenna module shall be matched to 50 Ohms. Sirius Radio Receiver This device handles the mixer, band-pass filter, and IF amplifier components needed to produce a signal which can be received and played as audible sound. This is all accomplished through a purchased radio receiver on the market since 2000, so

4 specifications for this device need not be listed since they are out of the scope of this project. Patent Search The following listed patents are related to the SDARS, which may or may not apply to my project. Searching was accomplished through Integrated GPS and SDARS antenna Interoperable satellite digital audio radio service (SDARS) receiver architecture Single path front end with digital AGC in SDARS system Portable SDARS-receiving device with integrated audio wire and antenna Low cost interoperable satellite digital audio radio service (SDARS) receiver architecture Receiver architecture for SDARS full band signal reception having an analog conversion to baseband stage Automatic gain control for satellite digital audio radio service receiver, method of automatically controlling gain and SDARS receiver incorporating the same Low cost interoperable satellite digital audio radio service (SDARS) receiver adapted to receive signals in accordance with advantageous frequency plan Equipment List The following lists the lab equipment needed to complete the project. This equipment will be used during the fabrication and testing stage. Not included in the list are general laboratory equipment and materials used to construct the antenna. Anechoic chamber workstation, RF COMM lab RF fabrication room and housed equipment for fabrication Network Analyzer, RF COMM lab Agilent E3634A Power supply Momentum software and workstation Preliminary Analysis This section describes the completion of preliminary design work minus lab equipment familiarization, which took up a majority of the time up to this point. Using a series of derived equations from [3] and [4], the center frequency of MHz, and the thickness and dielectric constants of the substrates, the width of the rectangular patch is calculated to be 2257 Mils and the length 1919 Mils. The effects of feed line

5 offset from the center of the patch, feed line length, and matching the antenna to 50 Ohms characteristic impedance remain to be investigated. The substrate selections for the top patch layer and the bottom feed layer have been chosen. The top layer is to have a thickness of 125 Mils and a dielectric constant of The bottom layer is to have a thickness of 31 Mils and an identical dielectric constant of These selections were based in part by previous work by Greg Zomcheck and Erik Zeliasz and materials that are on-hand at Bradley University. Matching of the antenna to 50 Ohms has been suggested through variation of the feed line inset to the patch, the width of the line, and its length. The next step is to investigate these parameters and implement them in the CAD software Momentum. The LNA remains to be bought from an external source. Since a new commercial receiver will be purchased, performance specifications on the noise figure and gain of the LNA may need adjusting before its purchase. Preliminary Schedule The following table describes the weekly workflow for the spring semester. A significant amount of time will be spent running software simulations before actual fabrication and testing. Fabrication should take only a short time. Week Activity 1/23 1/26 Design linearly polarized, proximity coupled patch antenna 1/27 2/2 Continue with design and begin simulating 2/3 2/9 Continue with simulations, start design for circular polarization, modifying the linearly polarized design 2/10 2/16 Continue with simulations of the linear or circularly polarized design 2/17 2/23 Continue with simulations on antenna design. Begin fabrication of the antenna and testing. 2/24 3/1 Continue with simulations on antenna design. Begin fabrication of LNA board and testing. Continue antenna testing 3/2 3/8 Wrap up antenna simulations. Continue with fabrication and testing 3/9 3/15 Wrap up antenna testing. Continue with LNA testing. Begin incorporation of both antenna and LNA 3/16 3/22 Continue with active antenna testing 3/23 3/29 Continue with active antenna testing 3/30 4/5 Wrap up antenna measurements, begin integration with commercial receiver

6 4/6 4/12 Test fabricated antenna with commercial receiver 4/13 4/19 Continue with integration, start presentation preparation / Final Project Report 4/20 4/26 Presentation preparation / Final Project Report 4/27 5/3 Presentation preparation / Final Project Report Conclusion This project will ultimately culminate in the design of a proximity coupled, singly fed, rectangular patch antenna with an adjoined LNA. The main difficulty of this project will be the computer aided simulations and analysis of measurements. Nevertheless, this project shall provide insight to the operation of patch antennas. Bibliography [1] Zomchek, Greg and Zeliasz, Eric. SDARS Front-End Receiver: Senior Capstone Project Report. Bradley University, May 13, [2] Haller, Nick. S-Band Antenna Element Requirements. Version RX Bradley University, August 18, [3] Vajha, Sasidhar. A Proximity Coupled Active Integrated Antenna. Bradley University. Summer, [4] Balanis, Constantine A. Antenna Theory: Analysis and Design, 2 nd ED. John Wiley & Sons, Inc [5] Iwasaki, Sawada, Kawabata. A Circularly Polarized Microstrip Antenna Using Singly- Fed Proximity Coupled Feed.