Browse Prior Art Database

Frequency generation for wideband radios with direct conversion receiver and direct launch transmitter

IP.com Disclosure Number: IPCOM000019175D
Original Publication Date: 2003-Sep-03
Included in the Prior Art Database: 2003-Sep-03
Document File: 2 page(s) / 35K

Publishing Venue

Motorola

Related People

Martina Zahrt: AUTHOR

Abstract

Frequency generation concept for TDMA wideband systems with direct conversion receiver and direct launch transmitter that reduces remodulation from the transmitter into the main synthesizer.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 57% of the total text.

Frequency generation for wideband radios with direct conversion receiver and direct launch transmitter

by Martina Zahrt

Abstract

Frequency generation concept for TDMA wideband systems with direct conversion receiver and direct launch transmitter that reduces remodulation from the transmitter into the main synthesizer.

Introduction

This paper describes improvements in the field of adjacent channel power suppression for linear modulated TDMA system, where direct launch transmitter combined with direct conversion receiver are incorporated.

Problem(s) To Be Solved

In a direct conversion receiver with IQ demodulation, the main synthesizer is required to generate frequencies that are twice as high as the wanted receive band due to the inherent division by two of the phase shifter [1].
A proven concept for the direct launch transmitter is to use a (Phase Locked Loop) PLL with a very high loop frequency [2] for the TX frequency generation.
This suppresses remodulation from the transmitter into the TX (Voltage Controlled Oscillator) VCO sufficiently. The reference for this loop is normally the main PLL.
To achieve the required frequency channel spacing, the main loop must have a low loop frequency [3]. In radios with superhet receivers the main VCO [4] does not suffer too much from remodulation, since the main PLL frequency has an offset to the TX frequency.
In radios with direct conversion receivers, however, the main VCO [4] oscillates on the second harmonic of the transmit frequen...