1. A method of stabilizing the phase and gain parameters within the operating bandwidth of an amplifier in a power pooling arrangement, comprising the steps of:
generating a pilot signal comprising a suppressed carrier signal with a single audio sideband, the pilot signal set to the approximate center of the operating bandwidth of the amplifier;
applying the pilot signal to a signal input of the amplifier;
coupling off a portion of the amplified pilot signal at a signal output of the amplifier;
extracting the amplified audio signal from the coupled off portion of the amplified pilot signal;
using a first phase detector to receive a first phase-related signal;
receiving a phase-related signal from the first phase detector;
using an adjustable phase shifter configured to receive and control a phase control signal from an integrator;
configuring a second phase detector to receive a second output signal, and to output a gain-related signal;
configuring an adjustable attenuator to receive the gain related signal from a comparatorintegrator to generate an integrated gain control signal and to influence the gain of the gain of an input communication signal in accordance with the gain control signal;
feeding back the phase control signal and the gain control signal to the adjustable phase shifter and the adjustable attenuator, respectively, in order to actively modify the phase and amplitude, respectively, of an input signal to the amplifier, to compensate for phase and gain parameter changes within the amplifier.
2. The method of claim 1 wherein the generating step comprises combining a reference carrier signal with a reference sideband signal.
3. The method of claim 1 wherein the extracting step comprises mixing the coupled off portion of the amplified pilot signal with a reference carrier signal input to extract the amplified audio signal.
4. The method of claim 1 wherein the converting step comprises phase detecting and integrating the first signal to generate the phase control signal.
5. The method of claim 1 wherein the converting step further comprises comparing the second signal to a predetermined reference signal to obtain a difference signal, and integrating the difference signal to generate the gain control signal.
6. The method of claim 1 wherein the feeding back step comprises applying the phase control signal to an adjustable phase shifter at the signal input to the amplifier.
7. The method of claim 1 wherein the feeding back step further comprises applying the gain control signal to an adjustable attenuator at the signal input to the amplifier.
8. A phase and gain stabilization network for a communication system amplifier in a power pooling arrangement, the amplifier configured to receive a communication signal at an input and to generate an amplified communication signal at an output, comprising:
a line length phase compensation device configured to adjust the phase of the input communication signal;
a line length gain compensation device connected in series with the line length phase compensation device, the line length gain compensation device configured to adjust the amplitude of the input communication signal;
a carrier frequency reference source configured to generate a carrier frequency output within the operating bandwidth of the amplifier;
a sideband frequency reference source configured to generate a sideband frequency output within the operating bandwidth of the amplifier;
a single sideband modulator configured to receive input signals from the carrier frequency reference source and from the sideband frequency reference source, the single sideband modulator further configured to generate an output pilot signal comprising the carrier frequency and the sideband frequency;
a first directional coupler configured to receive the pilot signal output from the single sideband modulator and to output a portion of the received pilot signal to the signal input of the amplifier, the first directional coupler further configured to receive the phase and gain line length-compensated communication signal from the series combination of the line length phase compensation device and the line length gain compensation device, and to output the phase and gain line length compensated communication signal to the signal input of the amplifier;
a feedback control circuit configured with a second directional coupler at the signal output of the amplifier to couple off a portion of the amplified pilot signal, the feedback control circuit further configured with a balanced mixer configured to receive a carrier frequency reference input from the carrier frequency reference source and to receive the coupled off portion of the amplified pilot signal from the second directional coupler, and to generate an output signal at the sideband frequency;
an amplifierdivider configured to receive the output signal at the sideband frequency from the output of the balanced mixer, the amplifierdivider further configured to amplify and divide the received output signal at the sideband frequency into a first output signal and a second output signal;
a first phase detector configured to receive the first output signal from the amplifierdivider and to output a phase-related signal;
an integrator configured to receive the phase-related signal from the first phase detector and to generate an integrated phase control signal;
an adjustable phase shifter configured to receive the phase control signal from the integrator and to adjust the phase of the input communication signal in accordance with the phase control signal;
a second phase detector configured to receive the second output signal from the amplifierdivider and to output a gain-related signal;
a comparatorintegrator configured to receive the gain-related signal from the second phase detector and to generate an integrated gain control signal based on the difference between the gain-related signal and a predetermined gain reference signal;
an adjustable attenuator configured to receive the gain control signal from the comparatorintegrator and to influence the gain of the input communication signal in accordance with the gain control signal;
wherein the adjustable phase shifter and the adjustable attenuator are connected in series between the output of the first coupler and the signal input to the amplifier, and wherein the adjustable phase shifter and the adjustable attenuator adjust the phase and amplitude, respectively, of the input communication signal to compensate for changes in the phase and gain parameters of the amplifier.
9. The phase and gain stabilization network of claim 8 wherein the amplifier is a traveling wave type of tube.
10. The phase and gain stabilization network of claim 8 wherein the single sideband modulator comprises two balanced modulators each configured to receive quadrature signals from the carrier frequency reference and the sideband frequency reference, and wherein the outputs of the two balanced modulators are summed to form the pilot signal.
11. The phase and gain stabilization network of claim 8 wherein the coupling factor of the first directional coupler is approximately \u221230 db.
12. The phase and gain stabilization network of claim 8 wherein the coupling factor of the second directional coupler is approximately \u221255 db.
13. The phase and gain stabilization network of claim 8 wherein the amplifierdivider comprises a stabilized audio amplifier.
14. The phase and gain stabilization network of claim 8 wherein the adjustable phase shifter is voltage-controlled.
15. The phase and gain stabilization network of claim 8 wherein the adjustable attenuator is voltage-controlled.
16. The phase and gain stabilization network of claim 8 wherein the adjustable phase shifter has an approximate range of plus or minus 180 degrees.
17. The phase and gain stabilization network of claim 8 wherein the adjustable attenuator has an approximate range of 0 to 4 db.
18. The phase and gain stabilization network of claim 8 wherein the line length phase compensation device is controllable by remote commands.
19. The phase and gain stabilization network of claim 8 wherein the line length gain compensation device is controllable by remote commands.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A neck-worn personal air filtration device comprising:
a blower adapted to provide an airflow;
a plenum comprising an upper surface and a lower surface, at least a portion of the upper surface of the plenum having an air permeable surface, the plenum being adapted to be worn about a neck of a user;
a hose connecting the blower to the plenum; and
a filter for filtering air flowing through the personal air filtration device, the blower being adapted to provide airflow to the plenum via the hose, the airflow being caused to exit the plenum through the air permeable surface, and the filter being disposed within the personal air filtration device to filter the airflow prior to or as the air exits the plenum.
2. The personal air filtration device of claim 1, wherein the filter comprises a point of delivery filter.
3. The personal air filtration device of claim 1, wherein the plenum is generally U-shaped and includes a neck portion and one or more chest portions.
4. The personal air filtration device of claim 3, wherein the neck portion is adapted to be worn behind the neck of the user and the chest portions are worn on a chest of the user.
5. The personal air filtration device of claim 4, wherein the air exiting through the air permeable surface is delivered to an area near a face of the user.
6. The personal air filtration device of claim 1 wherein the plenum comprises a chest portion generally shaped like a bib and adapted to be worn on a chest of the user.
7. The personal air filtration device of claim 6, wherein the plenum further comprises one or more shoulder portions adjoined to a top edge of the chest portion.
8. The personal air filtration device of claim 7, wherein the one or more shoulder portions are designed to extend around a back of a neck of the user to hold the plenum in position.
9. The personal air filtration device of claim 6, wherein one or more connectors extend from a top edge of the chest portion.
10. The personal air filtration device of claim 1, wherein the filter is removably attached to the plenum.
11. The personal air filtration device of claim 1, wherein the plenum comprises a single air chamber.
12. The personal air filtration device of claim 1, wherein the plenum comprises more than one air chamber.
13. The personal air filtration device of claim 1, wherein the lower surface comprises an air impermeable surface.
14. The personal air filtration device of claim 1, further comprising support structures within the plenum.
15. The personal air filtration device of claim 1, further comprising a generally air permeable cover.
16. A method of providing filtered air to an area around a head of a user comprising:
providing a plenum comprising an upper surface and a lower surface, at least a portion of the upper surface being an air permeable surface and including a filter, the plenum being adapted to be worn about a neck of the user;
providing a blower, the blower adapted to deliver air into the plenum; and
delivering air to the plenum, thereby causing the air to pass through the filter and into the area around the head of the user.