1. A process for making a membrane having curved features, comprising:
vacuum bonding a first surface of a first substrate to a first surface of a first membrane layer, the first surface of the first substrate having a plurality of cavities formed therein, the first membrane layer being an exposed layer of a second substrate, a second surface of the first membrane layer being attached to a handle layer of the second substrate, and the first surface of the first membrane layer seals the plurality of cavities to form a plurality of vacuum chambers at completion of the vacuum bonding;
removing the handle layer of the second substrate to expose the second surface of the first membrane layer;
exposing the second surface of the first membrane layer to a fluid pressure such that the first membrane layer bends in areas above the plurality of cavities and touches respective bottom surfaces of the plurality of cavities at a plurality of respective contact locations; and
annealing the first membrane layer and the first substrate to form permanent bonds between the first membrane layer and the first substrate at the plurality of respective contact locations.
2. The process of claim 1, further comprising:
depositing a second membrane layer over the second surface of the first membrane layer, such that the second membrane layer conforms to the second surface of the first membrane layer and includes a plurality of curved portions in the areas above the plurality of cavities.
3. The process of claim 2, wherein:
the second membrane layer includes multiple sub-layers, and
depositing the second membrane layer comprises sequentially depositing each of the multiple sub-layers over the second surface of the first membrane layer.
4. The process of claim 3, wherein the sub-layers include at least a reference electrode layer, a sputtered piezoelectric layer, and a drive electrode layer.
5. The process of claim 2, wherein the depositing is performed after the annealing.
6. The process of claim 2, further comprising:
after the second membrane layer is deposited, removing the bottom surfaces of the plurality of cavities to open the plurality of vacuum chambers and expose the first surface of the first membrane layer in areas within respective sidewalls of the plurality of cavities.
7. The process of claim 6, wherein removing the bottom surfaces of the plurality of cavities further comprises:
etching a second surface of the first substrate in at least the areas within the respective sidewalls of the plurality of cavities such that the plurality of vacuum chambers are opened and that the first surface of the first membrane layer are exposed in the areas within the respective sidewalls of the plurality of cavities, where exposed first surface of the first membrane layer serves as an etch stop for the etching.
8. The process of claim 6, further comprising:
removing the first membrane layer in the areas within the sidewalls of the plurality of cavities to expose the curved portions of the second membrane layer, while the curved portions of the second membrane layer remain curved during and after the removal of the first membrane layer.
9. The process of claim 8, wherein removing the first membrane layer in the areas within the respective sidewalls of the plurality of cavities further comprises:
etching the first membrane layer in the areas within the respective sidewalls of the plurality of cavities to expose the curved portions of the second membrane layer, where the exposed curved portions of the second membrane layer serves as an etch stop and the first substrate serves as a mask for the etching.
10. The process of claim 1, further comprising:
selectively etching the first surface of the first substrate through a patterned photoresist layer to form the plurality of cavities, the patterned photoresist layer defining respective lateral dimensions and locations of the plurality of cavities; and
removing the patterned photoresist layer from the first surface of the first substrate after the plurality of cavities reach a predetermined depth.
11. The process of claim 10, wherein the selective etching is dry etching.
12. The process of claim 10, wherein the respective bottom surfaces of the plurality of cavities are sufficiently smooth to enable bonding with another substrate.
13. The process of claim 1, wherein vacuum bonding the first surface of the first substrate to the first surface of the first membrane layer further comprises:
forming a oxide or nitride layer on a silicon substrate; and
bonding an exposed surface of the oxide or nitride layer to the first surface of the first substrate in a vacuum environment.
14. The process of claim 1, further comprising:
forming the plurality of cavities in the first surface of the first substrate.
15. The process of claim 1, wherein exposing the second surface of the first membrane layer to a fluid pressure comprises:
exposing the second surface of the first membrane layer to an atmosphere pressure.
16. The process of claim 1, wherein the plurality of cavities have a depth of 5-15 microns.
17. The process of claim 1, wherein the plurality of cavities have respective lateral dimensions of 150-200 microns.
18. The process of claim 1, wherein the first membrane layer has a thickness of 1-2 microns.
19. A process for making a membrane having a curved feature, comprising:
vacuum bonding a first surface of a first substrate to a first surface of a first membrane layer, the first surface of the first substrate having a cavity formed therein, the first membrane layer being an exposed layer of a second substrate, a second surface of the first membrane layer being attached to a handle layer of the second substrate, and the first surface of the first membrane layer seals the cavity to form a vacuum chamber at completion of the vacuum bonding;
removing the handle layer of the second substrate to expose the second surface of the first membrane layer;
exposing the second surface of the first membrane layer to a fluid pressure such that the first membrane layer bends in an area above the cavity and touches a bottom surface of the cavity at a contact location;
annealing the first membrane layer and the first substrate to form a permanent bond between the first membrane layer and the first substrate at the contact location;
depositing a second membrane layer over the second surface of the first membrane layer, such that the second membrane layer conforms to the second surface of the first membrane layer and includes a curved portion in the area above the cavity; and
after the second membrane layer is deposited, removing the bottom surface of the cavity to open the vacuum chamber and expose the first surface of the first membrane layer in an area within sidewalls of the cavity.
20. A process for making a membrane having a curved feature, comprising:
vacuum bonding a first surface of a first substrate to a first surface of a first membrane layer, the first surface of the first substrate including a cavity formed therein; the first membrane layer being an exposed layer of a second substrate, a second surface of the first membrane layer being attached to a handle layer of the second substrate, and the first surface of the first membrane layer seals the cavity to form a vacuum chamber at completion of the vacuum bonding;
removing the handle layer of the second substrate to expose the second surface of the first membrane layer;
exposing the second surface of the first membrane layer to a fluid pressure such that the first membrane layer bends in an area above the cavity;
depositing a second membrane layer over the second surface of the first membrane layer while the second surface of the first membrane layer is exposed to the fluid pressure, such that the second membrane layer conforms to the second surface of the first membrane layer and includes a curved portion in the area above the cavity; and
after the second membrane layer is deposited, removing the bottom surface of the cavity to open the vacuum chamber and expose the first surface of the first membrane layer in an area within sidewalls of the cavity.
21. The process of claim 20, wherein removing the bottom surface of the cavity further comprises:
etching a second surface of the first substrate in at least the area within the sidewalls of the cavity such that the vacuum chamber is opened and that the first surface of the first membrane layer is exposed in the area within the sidewalls of the cavity, where exposed first surface of the first membrane layer serves as an etch stop for the etching.
22. The process of claim 20, further comprising:
removing the first membrane layer in the area within the sidewalls of the cavity to expose the curved portion of the second membrane layer, while the curved portion of the second membrane layer remains curved during and after the removal of the first membrane layer.
23. The process of claim 22, wherein removing the first membrane layer in the area within the sidewalls of the plurality of cavities further comprises:
etching the first membrane layer in the area within the sidewalls of the cavity to expose the curved portion of the second membrane layer, where the exposed curved portion of the second membrane layer serves as an etch stop and the first substrate serves as a mask for the etching.
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 distributed acquisition apparatus, comprising:
a sampler component configured to receive a signal under test;
a plurality of analog-to-digital converters (ADCs) operationally coupled to the sampler component and configured to produce digitized samples of the signal under test;
a time-interleaved acquisition processing network including a plurality of interconnected distributed acquisition components, each distributed acquisition component including:
an acquisition memory configured to store a portion of the digitized samples; and
a first summer configured to de-interleave the digitized samples between the distributed acquisition components; and
a last distributed acquisition component associated with the interleaved processing network of distributed acquisition components, the last distributed acquisition component including an acquisition memory to store a portion of the digitized samples and a second summer configured to de-interleave the digitized samples, wherein the last distributed acquisition component is configured to receive the de-interleaved digitized samples from the plurality of distributed acquisition components and output a recombined coherent waveform.
2. The distributed acquisition apparatus of claim 1, further comprising:
a digital down-converter (DDC) section associated with the last distributed acquisition component, wherein the DDC section includes:
a mixer component configured to receive and multiply the recombined coherent waveform with a complex sinusoidal waveform, and to produce a mixed signal having mathematical real and imaginary parts;
a decimating filter coupled to the mixer component and configured to receive and filter the mixed signal; and
a down-sampler coupled to the decimating filter and configured to down-sample the mixed signal,
wherein the DDC section is configured to produce coherent down-converted complex in-phase and quadrature (IQ) data.
3. The distributed acquisition apparatus of claim 2, wherein the digital down-converter section includes a plurality of down-samplers and a plurality of decimating filters, wherein the plurality of down-samplers are interspersed between the plurality of decimating filters.
4. The distributed acquisition apparatus of claim 2, wherein the DDC section is configured to receive the recombined coherent waveform from the second summer of the last distributed acquisition component.
5. The distributed acquisition apparatus of claim 1, wherein the acquisition memory of the distributed acquisition components is configured to store real data samples.
6. The distributed acquisition apparatus of claim 1, wherein each of the distributed acquisition components includes an up-sampler coupled to the acquisition memory, and configured to up-sample the digitized samples by a factor M, wherein M is the total number of distributed acquisition components including the last acquisition component.
7. The distributed acquisition apparatus of claim 1, wherein each of the distributed acquisition components includes:
a digital down-converter (DDC) section, wherein each DDC section includes:
a mixer component configured to receive and multiply the corresponding portion of the digitized samples with a complex sinusoidal waveform, and to produce a mixed signal having mathematical real and imaginary parts;
a decimating filter coupled to the mixer component and configured to receive and filter the mixed signal; and
a down-sampler coupled to the decimating filter and configured to down-sample the mixed signal,
wherein each DDC section is configured to produce down-converted complex in-phase and quadrature (IQ) data.
8. The distributed acquisition apparatus of claim 7, wherein the digital down-converter section includes a plurality of down-samplers and a plurality of decimating filters, wherein the plurality of down-samplers are interspersed between the plurality of decimating filters.
9. The distributed acquisition apparatus of claim 7, wherein:
the first summer of each of the distributed acquisition components is coupled to an output of each corresponding DDC section, wherein the first summer is configured to de-interleave the down-converted data received from the DDC sections.
10. The distributed acquisition apparatus of claim 1, wherein each of the distributed acquisition components includes:
a mixer component coupled to an input of the corresponding acquisition memory, and configured to receive and multiply the corresponding portion of the digitized samples with a complex sinusoidal waveform, and to produce a mixed signal having mathematical real and imaginary parts;
a polyphase interpolation filter coupled to an output of the acquisition memory and configured to receive and filter the mixed signal; and
a down-sampler coupled to the corresponding polyphase interpolation filter and configured to down-sample the filtered signal.
11. The distributed acquisition apparatus of claim 10, wherein the polyphase interpolation filter includes a filter having the following frequency responses expressed as a z-transform:
H
m
\u2061
(
z
)
=
z
m
M
\xb7
H
\u2061
(
z
M
)
,
\u2062
m
\u2208
0
\u2062
:
\u2062
M
–
1
where H(z) is the desired digital down-conversion filter response for a given bandwidth span and target sample rate, m is the relative polyphase phase selected from 0 to M\u22121 for a given parallel branch of the polyphase filter, and M is the total number of distributed acquisition components in the interleaved processing network of distributed acquisition components including the last acquisition component.
12. The distributed acquisition apparatus of claim 11, further comprising a delay stage to compensate for the relative sampling phase offsets between distributed acquisition components.
13. The distributed acquisition apparatus of claim 11, wherein the filter has the overall frequency response expressed as the z-transform for cases where L is greater than or equal to M, where L is the down-sample factor for a given bandwidth span and associated sample rate.
14. The distributed acquisition apparatus of claim 1, wherein each of the distributed acquisition components includes:
an acquisition DDC section coupled to an input of the acquisition memory, wherein each acquisition DDC section includes:
a mixer component configured to receive and multiply the corresponding portion of the digitized samples with a complex sinusoidal waveform, and to produce a mixed signal having mathematical real and imaginary parts;
a decimating filter coupled to the mixer component and configured to receive and filter the mixed signal; and
a down-sampler coupled to the decimating filter and configured to down-sample the mixed signal by a factor of LM, wherein M is the total number of distributed acquisition components in the interleaved processing network of distributed acquisition components including the last acquisition component, and L is the down-sample factor for a given bandwidth span and associated sample rate; and
a complex finite impulse response (FIR) filter section coupled to an output of the corresponding acquisition memory, wherein each complex FIR filter section includes a fractional time-shift filter.
15. The distributed acquisition apparatus of claim 14, wherein the digital down-converter section includes a plurality of down-samplers and a plurality of decimating filters, wherein the plurality of down-samplers are interspersed between the plurality of decimating filters.
16. The distributed acquisition apparatus of claim 14, further comprising a second complex FIR filter coupled to the second summer of the last distributed acquisition component, wherein the second complex FIR filter is configured to produce filtered complex IQ data samples.
17. The distributed acquisition apparatus of claim 14, wherein the complex FIR filter section comprises a single complex FIR filter that combines a fractional time-shift and an arbitrary complex FIR filter in each section.
18. The distributed acquisition apparatus of claim 14, wherein each of the distributed acquisition components further includes a spin DDC section coupled to an output of the corresponding acquisition memory and to an input of the corresponding complex FIR filter section, wherein the acquisition DDC section is configured to operate in real-time prior to storing acquisition data to the corresponding acquisition memory, and wherein the spin DDC section is configured to process information received from the acquisition memory.
19. The distributed acquisition apparatus of claim 1, further comprising:
a spin DDC section coupled to the second summer of the last distributed acquisition component; and
a frequency transform section coupled to the spin DDC section, wherein the frequency transform section is configured to produce complex spectral samples in the frequency domain.
20. The distributed acquisition apparatus of claim 1, further comprising:
an acquisition buffer coupled to the second summer of the last distributed acquisition component; and
a frequency transform section coupled to the acquisition buffer, wherein the frequency transform is configured to produce complex spectral samples in the frequency domain.
21. The distributed acquisition apparatus of claim 1, wherein each of the distributed acquisition components includes:
an acquisition DDC section coupled to an input of the acquisition memory, wherein the acquisition DDC section includes:
a mixer component configured to receive and multiply the corresponding portion of the digitized samples with a complex sinusoidal waveform, and to produce a mixed signal having mathematical real and imaginary parts;
a decimating filter coupled to the mixer component and configured to receive and filter the mixed signal;
a down-converter coupled to the one or more decimating filters and configured to down-sample the mixed signal by a factor of LM, wherein M is the total number of distributed acquisition components in the interleaved processing network of distributed acquisition components including the last acquisition component, and L is the down-sample factor for a given bandwidth span and associated sample rate; and
a frequency transform section coupled to an output of the corresponding acquisition memory, wherein each frequency transform section is configured to produce complex spectral samples in the frequency domain.
22. The distributed acquisition apparatus of claim 21, wherein the digital down-converter section includes a plurality of down-samplers and a plurality of decimating filters, wherein the plurality of down-samplers are interspersed between the plurality of decimating filters.
23. The distributed acquisition apparatus of claim 21, wherein:
the first summer of each of the distributed acquisition components is coupled to an output of each corresponding frequency transform section, wherein the first summer is configured to de-interleave the complex spectral samples received from the frequency transform sections.
24. The distributed acquisition apparatus of claim 21, further comprising:
a spin DDC section coupled to an output of the acquisition memory and to an input of the frequency transform section.
25. The distributed acquisition apparatus of claim 1, further comprising:
a spin DDC section coupled to the second summer of the last distributed acquisition component; and
a complex FIR filter section coupled to the spin DDC section, wherein the complex FIR filter section includes a complex finite impulse response (FIR) filter to produce filtered complex IQ data samples.