Browse Prior Art Database

Radio with One Oscillator and Short Turn-Around Time

IP.com Disclosure Number: IPCOM000117589D
Original Publication Date: 1996-Apr-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 92K

Publishing Venue

IBM

Related People

Camp, WO: AUTHOR [+2]

Abstract

All of the current cellular radios with a receiver section and a transmitter section either have elaborate schemes with multiple oscillators to permit short transition times between receive and transmit functions, or share a single oscillator and take a longer time to shift between those two functions. One would like to have both a short transition time between receive and transmit functions and an architecture that only requires one oscillator.

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This is the abbreviated version, containing approximately 52% of the total text.

Radio with One Oscillator and Short Turn-Around Time

      All of the current cellular radios with a receiver section and
a transmitter section either have elaborate schemes with multiple
oscillators to permit short transition times between receive and
transmit functions, or share a single oscillator and take a longer
time to shift between those two functions.  One would like to have
both a short transition time between receive and transmit functions
and an architecture that only requires one oscillator.

      One well-known solution using only one oscillator is to use
what is commonly referred to as a baseband receiver, also known as a
receiver with a DC Intermediate Frequency (IF).  However, problems
with excessive flicker noise (I/F noise) at low frequencies and noise
from external noise sources makes this architecture unsuited for
sensitive receivers in the usual noisy environments associated with
computers.

      A solution to the problem of achieving short transition times
between receive and transmit functions with an architecture with one
oscillator is based on the multiple use of the function called a
vector modulator often used in the transmit function of a radio.

      A vector modulator function is one that controls the amplitude
and phase of an RF signal based on the analog inputs (I and Q).  If I
and Q are, respectively, the X and Y axes of a plot, and I and Q both
range from -1 to 1, the amplitude of the RF signal is the magnitude
of the vector from the origin to the point determined by I and Q
voltages, and the phase is the angle of that vector relative to the
positive X axis.  The vector modulator is sued in a transmitter
function to create the modulated RF waveform to convey data to a
receiver function.  For instance, if DATA and DATA BAR are the signal
and complement for a data signal, then connection DATA to I and DATA
BAR to Q will create biphase modulated RF signal with 90 degrees
phase shift between levels.  One can create QPSK, shaped QPSK, GMSK,
etc. by controlling the analog signals to t...