Browse Prior Art Database

A METHOD OF IMPROVING WIDE BAND RECEIVER DYNAMIC RANGE

IP.com Disclosure Number: IPCOM000008605D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jun-26
Document File: 2 page(s) / 93K

Publishing Venue

Motorola

Related People

David Lovelace: AUTHOR [+3]

Abstract

This circuit method improves the dynamic range of wide band receivers. Dynamic range is determined as the range between the wanted signals to that of the intermodulation signals which are typically well above the noise floor of a receiver.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

Page 1 of 2

0 M

MOrOROLA Technical Developments

A METHOD OF IMPROVING WIDE BAND RECEIVER DYNAMIC RANGE

by David Lovelace, Stephen Dow and Bernie Weir

BACKGROUND

  This circuit method improves the dynamic range of wide band receivers. Dynamic range is determined as the range between the wanted signals to that of the intermodulation signals which are typically well above the noise floor of a receiver.

PROBLEM

  In a receiver, sometimes high level signals are present which cause intermodulation distortion. This problem is especially severe in wide band receivers, Cable television systems are an example of such a wide band, high level carrier environment, These high level signals cause intermodulation distortion due to the inherent non-linear nature of

the low noise amplifier (LNA) and the frequency conversion mixer. Obtaining a high degree of linearity (low levels of intermodulation distortion) is difficult to obtain under low power, low voltage conditions in which these circuits are required to operate. And as a consequence, expensive and high power circuits are utilized to obtain the linearity required for these wide band receivers. Prior art utilizes a method of determining the power level of the signals incident to or output from the first mixer and setting the gain of the LNA so as to reduce the level of the signals incident to the mixer (shown in Figure I). By lowering the level of the mixer input signal, the distortion products are minimized. This is due to the fact the intermodulation distortion increases three times as fast as the required signal and hence dominates the dynamic range.

Fig. 1 Block Diagram of Prior Art

  During this process of changing the LNA's gain, other important characteristics of the LNA such as NF and IP3 (third order intercept, a metric of inter- modulat...