Pulse or digital communications – Transmitters – Angle modulation
Reexamination Certificate
2001-12-18
2003-12-16
Le, Amanda T. (Department: 2634)
Pulse or digital communications
Transmitters
Angle modulation
C332S144000, C327S234000, C327S235000, C327S238000
Reexamination Certificate
active
06665353
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and/or architecture for implementing phase shifters generally and, more particularly, to a method and/or architecture for implementing a phase shifter with 180 degrees of phase adjustment from one of four fixed phase positions which may be selectable by a user.
BACKGROUND OF THE INVENTION
Referring to
FIG. 1
, a phase tuning representation
10
of a conventional 180 degree phase shifter is shown. Phase shifters are frequently used in RF signal processing (e.g., power amplifier correction, antenna beam forming, diversity signal combining, etc.). A typical phase shifter provides a phase shift adjustment range of 180 degrees for a given range of electronic control input. An input signal VPHS is varied to control the phase shift (i.e., VPHS varies from 0V to +5V). For example, the phase shifter continuously adjusts transfer phase from −90 degrees at VPHS=0V to +90 degrees at VPHS=+5V. When a particular desired transfer phase lies outside the range (i.e., +120 degrees), additional fixed or variable phase shift must be added at additional cost, space and complexity. Adding fixed phase shift limits flexibility, since the fixed phase shift chosen will still only provide 180 degrees to be tuned electronically.
Conventional approaches can add a variable mechanical phase shift. However, such mechanical phase shifters are expensive, bulky and delicate. Conventional approaches can also cascade two 180 degree phase shifters. However, such a configuration doubles the value of the phase tuning constant, which can cause unacceptable tuning noise, loop dynamic issues, and/or noise figure degradation.
Referring to
FIG. 2
, a conventional 180 degree phase shifter
20
is shown. The RF input signal RF_IN is split in a quadrature network
22
. The outputs COS(R) and SIN(R) are equal in magnitude and 90 degrees apart in phase. The RF signals SIN(R) and COS(R) are applied to two four-quadrant analog multipliers
24
and
26
. The multipliers
24
and
26
are controlled by two baseband signals A and B. The RF outputs from the multipliers
24
and
26
are summed by the summing amplifier
28
to produce a composite RF output signal RF_OUT. The signals A and B are derived from the VPHS input using the weighting network
30
. The weighting functions A=f
1
(VPHS) and B=f
2
(VPHS) are designed such that the magnitude of the RF transfer function remains constant as VPHS is tuned, while the phase of the RF transfer function of the circuit
20
varies linearly with VPHS. The circuit
20
has an RF transfer function as shown in FIG.
1
.
It is generally desirable to have a phase shifter that may (i) provide a variable phase shift adjustment from a selected fixed starting point (e.g., a variable phase shift of ±90 degrees from +90 degrees which is from 0 to 180 degrees), (ii) be implemented using a minimum of die area, (iii) provide low cost implementation, and/or (iv) provide robust operation.
SUMMARY OF THE INVENTION
The present invention concerns an apparatus comprising a quadrature network, an RF combining circuit and a weighting network. The quadrature network may be configured to generate a first and a second signal in response to an input signal. The RF combining circuit may be configured to generate an output signal comprising the input signal variably phase shifted from a selectable fixed phase starting point in response to the first signal, the second signal and one or more weighting signals. The weighting network may be configured to generate the weighting signals in response to a voltage control signal and one of four possible output selections. The voltage control signal may be configured to control the variable phase shift.
The objects, features and advantages of the present invention include providing a method and/or architecture for implementing a phase shifter with 180 degrees of phase adjustment from one of four fixed phase positions that may (i) provide user selectability, (ii) provide a variable phase shift adjustment from a selectable, fixed starting point, (iii) be implemented in minimal die area, (iv) be implemented with a lower cost and have a more robust operation than mechanical designs, and/or (v) reduce or eliminate tuning noise, loop dynamic issues and noise figure degradations.
REFERENCES:
patent: 4977382 (1990-12-01), Podell et al.
patent: 5019793 (1991-05-01), McNab
patent: 5541961 (1996-07-01), Farrow
patent: 6144704 (2000-11-01), Startup et al.
patent: 2002/0018534 (2002-02-01), Sevenhans et al.
“A Monolithic Microsystem for Analog Synthesis of Trigonometric Functions and Their Inverses”, By Barrie Gilbert, IEEE Journal of Solid-State Circuits, vol. SC-17, No. 6, Dec. 1982, pp. 1179-1191.
Christopher P. Maiorana P.C.
Le Amanda T.
Sirenza Microdevices, Inc.
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