1. A method comprising:
receiving an external RF magnetic field with a h-vector detector;
measuring voltages across terminals of the h-vector detector when the detector receives a microwave;
varying the angle between an external applied magnetic field and the RF current;
determining the angular dependence of the measured voltages; and
calculating at least one magnetic-field vector (h-vector) component of the microwave based, at least in part, upon the angular dependence.
2. The method of claim 1, further comprising varying the intensity of the external magnetic field.
3. The method of claim 2, where determining the angular dependence of the measured voltages further comprises calculating, for each angle between the external applied static magnetic field and the RF current, Lorenz (L) and dispersive (D) amplitudes of the measured voltages (U) given by:
U
=
L
\u2062
\u2062
\u0394
\u2062
\u2062
H
2
(
H
–
H
0
)
2
+
\u0394
\u2062
\u2062
H
2
+
D
\u2062
\u2062
\u0394
\u2062
\u2062
H
\u2062
(
H
–
H
0
)
(
H
–
H
0
)
2
+
\u0394
\u2062
\u2062
H
2
,
where H is the applied magnetic field, H0 is the resonant magnetic field, and \u0394H is the half width at half maximum (HWHM).
4. The method of claim 3, where calculating the Lorenz (L) and dispersive (D) amplitudes comprises performing at least one curve fitting operation.
5. The method of claim 3, where calculating the at least one h-vector component further comprises numerically fitting at least one of equations:
L=\u2212RARS0M0jz sin(2\u03b8)(\u2212Axxhxi cos(\u03b8)+Axxhzi sin(\u03b8)\u2212Axyhyr)2 and
D=\u2212RARS0M0jz sin(2\u03b8)(Axxhxr cos(\u03b8)\u2212Axxhzr sin(\u03b8)\u2212Axyhyi)2,
where hx,y,zr,i are h-vector components indicating real (r) and imaginary (i) parts of the complex number hx,y,z, \u03b8 is the angle between the external applied static magnetic field and the RF current, and amplitudes of effective permeability tensor components Axx and Axy are given by:
A
xx
=
\u03b3
\u2061
(
H
0
\u2062
M
0
+
M
0
2
)
\u03b1
G
\u2062
\u03c9
\u2061
(
2
\u2062
H
0
+
M
0
)
and
A
xy
=
M
0
\u03b1
G
\u2061
(
2
\u2062
H
0
+
M
0
)
for
\uf603
H
–
H
0
\uf604
\u2062
\u2062
<<
H
0
,
where \u03b3 is a gyromagnetic ratio, M0 is the saturation magnetization, \u03b1G is the Gilbert damping constant, and \u03c9 is the frequency of the microwave.
6. The method of claim 1, the magnetic field detector comprising a microstrip having dimensions such that d<<w<<l<<\u03bb, where w is the width of the microstrip, d is the thickness of the microstrip, l is the length of the microstrip, and \u03bb is the wavelength of the microwave.
7. The method of claim 1, further comprising calculating an RF current j in response to measured values of the static magnetic field H, angle \u03b8, and RF magnetic field h.
8. The method of claim 1, further comprising calculating a static field H in response to measured values of the RF current j, angle \u03b8, and RF magnetic field h.
9. A method comprising:
providing an array of RF magnetic field detectors, each element of the array being positioned at a different angle with respect to each other;
subjecting the array to an external applied swept magnetic field;
measuring voltages across terminals of each element of the array when the array receives a microwave;
associating each measured voltage with a respective angle; and
calculating at least one magnetic-field vector (h-vector) component of the microwave based, at least in part, upon the association.
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 method of controlling ripple in an output voltage of a switching regulator, comprising:
providing a ramp circuit to selectively charge and discharge a ramp capacitor, the ramp capacitor providing a ramp voltage;
selectively adding the ramp voltage to the output voltage to generate a summation voltage;
comparing the summation voltage to a reference voltage to generate a control signal; and
coupling an input voltage to an LC circuit based on the control signal, the LC circuit providing the output voltage, wherein the input voltage is selectively coupled to the LC circuit, when the ramp capacitor is selectively charged.
2. The method of claim 1, further including selectively decoupling the input voltage from the LC circuit, when the ramp capacitor is selectively discharged.
3. The method of claim 2, wherein the switching regulator operates in a continuous mode, when the switching regulator is supplying a load current greater than a mode switching load current.
4. The method of claim 3, wherein the LC circuit comprises an inductor and a capacitor coupled in series, the voltage across the capacitor providing the output voltage, an inductor current flowing through the inductor, wherein the inductor current is greater than zero when the switching regulator operates in the continuous mode.
5. The method of claim 4, wherein a delta inductor current flowing through the inductor is substantially the same when the switching regulator operates in the continuous mode and when the switching regulator operates in a discontinuous mode.
6. The method of claim 4, wherein based on the control signal,
either a first switch selectively couples the input voltage to the inductor, when a second switch is coupled to the inductor is turned off; or
the first switch selectively decouples the input voltage to the inductor, when the second switch is selectively turned on to couple the inductor to a ground potential.
7. The method of claim 2, wherein based on the control signal, a ramp switch selectively couples and decouples the ramp capacitor to a discharge resistor.
8. The method of claim 1, wherein a first comparator circuit compares the summation voltage and the reference voltage, the ripple in the output voltage is less than a hysteresis voltage of the first comparator circuit.
9. A switching regulator, comprising:
a ramp circuit configured to selectively charge and discharge a ramp capacitor, the ramp capacitor providing a ramp voltage;
a summation circuit to add the ramp voltage to an output voltage of the switching regulator to generate a summation voltage;
a comparator circuit to compare the summation voltage to a reference voltage to generate a control signal; and
a first control circuit configured to couple an input voltage to an LC circuit based on the control signal, the LC circuit providing the output voltage, and
wherein the input voltage is selectively coupled to the LC circuit, when the ramp capacitor is charged.
10. The switching regulator of claim 9, wherein the input voltage is selectively decoupled from the LC circuit, when the ramp capacitor is discharged.
11. The switching regulator of claim 9, wherein, when the switching regulator is supplying a load current greater than a mode switching load current, the switching regulator operates in a continuous mode.
12. The switching regulator of claim 11, wherein the LC circuit comprises an inductor and a capacitor coupled in series, the voltage across the capacitor providing the output voltage, an inductor current flowing through the inductor, and wherein the inductor current is greater than zero, when the switching regulator operates in the continuous mode.
13. The switching regulator of claim 12, wherein a delta inductor current flowing through the inductor is substantially same when the switching regulator operates in the continuous mode and when the switching regulator operates in a discontinuous mode.
14. The switching regulator of claim 11, wherein based on the control signal,
a first switch selectively couples the input voltage to the inductor, when a second switch coupled to the inductor is turned off; and
the first switch selectively decouples the input voltage to the inductor, when the second switch selectively turned on to couple the inductor to a ground potential.
15. The switching regulator of claim 12, wherein based on the control signal, a ramp switch selectively couples and decouples the ramp capacitor to a discharge resistor.
16. The switching regulator of claim 9, wherein the ripple in the output voltage is less than a hysteresis voltage of the comparator circuit.
17. The switching regulator of claim 9, wherein at least a portion of the regulator is fabricated as an integrated circuit.