Patent Application
20080068074
The invention will be understood more fully from the detailed description given below and from the accompanying drawings of embodiments of the invention which, however, should not be taken to limit the invention to the specific embodiments described, but are for explanation and understanding only.
In either embodiment, the system controls the amplitude of its supply with a Class G amplifier, which switches its output device between more than one power supply rail in order to increase power efficiency. Class G amplifiers are easier to make work at high frequencies than are the Class D amplifiers used in the prior art, and they don't produce significant amounts of out of band energy. While a Class D amplifier would require a large LC filter to remove out of band energy, the Class G amplifier can use a significantly smaller LC filter or even no LC filter. Having a smaller—or omitted—LC filter allows for better alignment of the envelope to the RF output signal. Since Class G amplifiers are efficient and the power supply of the linear amplifier is close to the envelope, the overall system is very power efficient.
In
A fixed signal splitter receives the input signal VINBE which provides phase information to be imposed on the output signal, and splits it into a positive signal path input signal VINP and a negative signal path input signal VINN. (“P” and “N” may be understood to suggest “positive” and “negative” as a simplistic shorthand for distinguishing the two halves of the circuit.) A first Class G Amplifier P in the positive signal path receives an input signal EVINP which defines the envelope of the input signal VINBE except the gain. A second Class G Amplifier N in the negative signal path receives an input signal EVINN which defines the envelope of the input signal VINBE except the gain. The envelope signals EVINP and EVINP include amplitude information which is to be imposed on the output signal.
A first Phase Amplifier P receives the VINP signal, and its VCC is modulated by the Class G Amplifier P (after passing through an optional LC Filter P), to produce a positive signal path output signal VOUTP. A second Phase Amplifier N receives the VINN signal, and its VCC is modulated by the Class G Amplifier N (after passing through an optional LC Filter N), to produce a negative signal path output signal VOUTN.
A balun and matching network combines the VOUTP and VOUTN signals to produce the final output signal VOUT which is driven onto the antenna.
EVINP and EVINN are determined by the envelope of VINBE but then adjusted based on the target envelope amplitude in order to pass the RF signal envelope through more rail combinations, to increase power efficiency. Digital lookahead to give advance notice to the Class G circuitry may be used to control the transitioning of the Class G amplifiers in order to more cleanly and easily provide lookahead transitioning for the Class G amplifier rails.
An input signal VINBE is received by an adjustable signal splitter, and contains both the phase information and the amplitude information to be imposed on the output signal. The signal splitter splits VINBE according to a split control signal, to generate a positive signal path input signal VINP and a negative signal path input signal VINN. There are many ways to make adjustable splitters. In integrated circuit design, the adjustable splitter can be two separate gain stages where the gain to each linear amplifier is independently controllable. The adjustable signal splitter is adjusted based on the envelope amplitude in order to pass the RF signal envelope through more rail combinations to increase power efficiency.
The positive signal path input signal VINP is received by a first Linear Amplifier P which amplifies it to generate a positive path output signal VOUTP. The negative signal path input signal VINN is received by a second Linear Amplifier N which amplifies it to generate a negative path output signal VOUTN. A balun and matching network (which may be combined for both signal paths, as shown, or may be separately implemented in the two signal paths) combines these two output signals to produce the final output signal VOUT which it drives onto the antenna.
A first Class G Amplifier P receives a signal EVOUTPDC which gives the desired envelope of the VOUTP signal plus a DC shift, and produces a VCC reference for the Linear Amplifier P. Optionally, this VCC may first be passed through an LC Filter P. A second Class G Amplifier N receives a signal EVOUTNDC which gives the desired envelope of the VOUTN signal plus a DC shift, and produces a VCC reference for the Linear Amplifier N. Optionally, this VCC may first be passed through an LC Filter N.
Optionally, digital lookahead is used, by using the split control signal or one substantially similar to it, to control the transitioning of the Class G amplifiers. In digital RF modulation, it is common that the RF signal amplitude and envelope are digitally predictable. This can be used to more cleanly and easily provide lookahead transitioning for the Class G amplifier rails.
In the context of
The first Class G Amplifier P may be powered by rail combination 61 (power rail 1 to ground), rail combination 62 (power rail 2 to ground), or rail combination 63 (power rail 3 to ground), and the second Class G Amplifier N may be powered by rail combination 64 (power rail 1 to ground), rail combination 65 (power rail 2 to ground), or rail combination 65 (power rail 3 to ground). Corresponding power rails at the two amplifiers may, but are not necessarily, at the same voltage level. In this example, the RF amplifier always used a GND bottom rail. That helps with RF amplifier design but it is not absolutely necessary; using a non-GND reference is possible within the scope of this invention, for example a combination of power rail 3 to power rail 1.
In one embodiment, for the smallest envelope (of VOUTP/N in
In other embodiments, other orderings are possible. For example, after zone 61 is exhausted, signal growth could be accommodated by using zone 64 (before zones 62 or 63). Then, it could use zone 62 with zone 64, then zone 62 with zone 65, followed by zone 63 with zone 65, then zone 63 with zone 66, and so forth.
In some embodiments, zones 61 and 62 may be used as subsets of zone 63, and zone 61 may be used as a subset of zone 62, and similarly for zones 64-66. Using the subset zones helps with efficiency, but is not required.
Note that
In some embodiments, the power rails are linearly spaced, such that power rails 1 and 2 are respectively 33.3% and 66.7% of the voltage of power rail 3. This yields six possible configurations: (1) zone 61 (33.3%), (2) zone 62 (66.7%), (3) zone 63 (100%), (4) zone 63 plus zone 64 (133.3%), (5) zone 63 plus zone 65 (166.7%), and (6) zone 63 plus zone 66 (200%).
In other embodiments, the zones are non-linearly spaced, in order to produce more rail combinations. For example, if power rails 1 and 2 are respectively 20% and 60% of the voltage of power rail 3, there are eight rail combinations: (1) zone 61 or zone 64 (20%), (2) zone 61 plus zone 64 (40%), (3) zone 62 or zone 65 (60%), (4) zone 62 plus zone 64 or zone 61 plus zone 65 (80%), (5) zone 63 or zone 66 (100%), (6) zone 63 plus zone 64 or zone 66 plus zone 61 or zone 62 plus zone 65 (120%), (7) zone 63 plus zone 65 or zone 66 plus zone 62 (160%), and (8) zone 63 plus zone 66 (200%). This can be advantageous, because the more power rails there are, and the more intelligently they are used, the higher the ultimate theoretical efficiency of the system becomes. Non-linearly spaced power rails can also be used to match the probability density function for the RF power transmission to better optimize average power dissipation. Matching the rails to the probability density function is useful in all cases such as in
In another embodiment, the rails are adjusted based on signal level, such as by using digital lookahead or by inspecting the input signal. This allows the rails to be optimized to provide the highest efficiency for the current signal level.
The number of zones, and the voltage levels of the rails, given above are for illustration only, and are not intended to be an exhaustive listing. The invention may be practiced with a wide variety of Class G Type amplifier configurations.
In some embodiments, the signal can be broken into more than two paths with various phases, and can be recombined with a more complicated matching network. This will tend to further increase theoretical efficiency, but may add to cost and complexity of the matching network. For example, there may be four signal paths and three baluns; such a system would look like a double set of the circuitry of
The principles of this invention may also be applied to a sort of inverted system in which the linear amplifier or phase amplifier is on the supply side using P-type devices (e.g. PLDMOS, PMOS, etc.) and the amplitude modulation portion of the circuitry uses Class G Type amplifiers switching to lower rails. The principles of this invention may also be employed in power control of phase amplifiers, in which case the amplitude modulation in the power supply is simply a DC level to control the output power.
When one component is said to be “adjacent” another component, it should not be interpreted to mean that there is absolutely nothing between the two components, only that they are in the order indicated.
The various features illustrated in the figures may be combined in many ways, and should not be interpreted as though limited to the specific embodiments in which they were explained and shown.
Those skilled in the art, having the benefit of this disclosure, will appreciate that many other variations from the foregoing description and drawings may be made within the scope of the present invention. Indeed, the invention is not limited to the details described above. Rather, it is the following claims including any amendments thereto that define the scope of the invention.
This application is a continuation-in-part of U.S. Provisional Patent Application 60/844,885 entitled “Method and Apparatus for Efficient Narrow Band Amplification” filed Aug. 14, 2006 by Cary L. Delano, and claims benefit of that filing date to the maximum extent permissible. That application is incorporated herein by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 60844885 | Sep 2006 | US |
