Interference mitigation for portable CDMA cellular radios, 1998

Item — Call Number: MU Thesis Fok

Identifier: b2087984

Staff Only

Scope and Contents

From the Collection:

The collection consists of theses written by students enrolled in the Monmouth College and Monmouth University graduate Electronic Engineering programs. The holdings are bound print documents that were submitted in partial fulfillment of requirements for the Master of Science degree.

Dates

Creation: 1998

Creator

Fok, Wilson K. (1954- ) (Author, Person)
Benjamin, Richard (1930-2010) (Thesis advisor, Person)

Conditions Governing Access

All analog collection holdings are limited to library use only.

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Extent

1 Items (print book) : 95 pages ; 8.5 x 11.0 inches (28 cm).

Language of Materials

English

Additional Description

Abstract

Ideally, wireless handset users should be able to use their handsets to communicate anywhere within the designated service areas without fear of dropping call. In reality however, calls do get dropped and are getting increasingly more so from strong radio frequency (RF) interference due to heavy deployment of cellular systems. The ability of the handset receiver to select among many other signals, no matter how minute they are and reject all other unwanted strong signals is what this project is all about.

In receiving systems, the strong signal handling capability is measured using two-tone intermodulation distortion (IMD) as figure of merit. To address the above issue, IS-98-A standard has redefined the IMD test to be much more stringent. This project studies the inferior strong-signal handling capability resulting from using a low output third order intercept point (OIP3) low noise amplifier (LNA) in portable Code Division Multiple Access (CDMA) cellular handsets. The goal is to improve the receiving systems [sic] such that it can handle the strong signals without compromising other design goals, particularly that of low current drain. In this project, the improved receiving system utilizes a high OIP3 LNA device in conjunction with the original low OIP3 LNA. The high OIP3 LNA is used only when there is interference present. The presence of interference is determined by the mitigation logic and the design of the mitigation logic exploits the frame error rate (FER) counter combined with received signal strength indicator (RSSI) resided within the CDMA handset receiving system. The choice of the high OIP3 LNA device which based primarily on the requirement of OIP3, gain (G) and noise figure (NF) is determined through analysis of receive sensitivity and IMD level. In light of the above, receive sensitivity and IMD level, spreadsheets have been developed for the analysis. The analysis is crucial in determining the required OIP3 to meet the IS-98-A redefined IMD specification.

The following contains the results of the analysis and testing of a high OIP3 LNA used in such CDMA handset. The intent is to identify the OIP3 requirement to handle the strong unwanted signals and to demonstrate that when an LNA with such an OIP3 is used, it would satisfy the IS-98-A redefined specification. The analysis did indeed show that the original prototype receiving system could be improved to satisfy the stringent IS-98-A redefined test. This improvement is accomplished by using a LNA with OIP3 of 20 dBm i.e. 20 dB higher than the original LNA OIP3. Actual laboratory testing also substantiated the analysis results.

The study for this project was carried out during September 15 - November 25, 1998.

Partial Contents

Preface -- Introduction -- 1. Near-far effect on power consumption of portable cellular radios -- 2. Interference mitigation -- 3. Non-linearity and third order intermodulation product (IM3): a quick review -- 4. Sensitivity and IMD test base lining with analysis spreadsheets -- 5. Third order intercept point prediction -- 6. Mitigation scheme validation -- 7. Conclusion -- References -- Appendices.