Methods and apparatus for in-pixel filtering in focal plane arrays

An apparatus for counting pulses in a series of pulses representing an analog signal, the apparatus comprising:

• an integrated circuit comprising a plurality of unit cells, wherein at least one unit cell in the plurality of unit cells comprises:
• a plurality of counters operably configured to count at least one pulse in the series of pulses representing the analog signal, the plurality of counters comprising a first counter configured to be switched from a first operating mode to a second operating mode independently of an operating mode of a second counter in the plurality of counters;
• and
• a clock, operably coupled to the first counter and to the second counter, to supply an in-phase clock signal to the first counter and a quadrature clock signal to the second counter,
• wherein the first and second counters are configured to switch between count-up and count-down modes in response to the in-phase and quadrature clock signals, respectively.

An apparatus for counting pulses in a series of pulses representing an analog signal, the apparatus comprising:

• an integrated circuit comprising a plurality of unit cells, wherein at least one unit cell in the plurality of unit cells comprises:
• a plurality of counters operably configured to count at least one pulse in the series of pulses representing the analog signal, wherein at least one counter in the plurality of counters is configured to be switched from a first operating mode to a second operating mode independently of operating modes of the other counters in the plurality of counters;
• a converter to generate the series of pulses representing the analog signal;
• and
• a variable capacitance operably coupled to the converter and configured to integrate the analog signal when the at least one counter transitions from the first operating mode to the second operating mode.

A method of counting pulses in a series of pulses representing an analog signal in at least one unit cell in an array of unit cells, wherein the at least one unit cell comprises a plurality of counters, the method comprising:

• switching at least one counter in the plurality of counters from a first operating mode to a second operating mode independent of operating modes of other counters in the plurality of counters;
• changing a count in the at least one counter in response to at least one pulse in the series of pulses;
• and
• changing a magnitude of the analog signal represented by a least significant bit of the at least one counter.

A method of counting pulses in a series of pulses representing an analog signal in at least one unit cell in an array of unit cells, wherein the at least one unit cell comprises a plurality of counters, the method comprising:

• detecting a modulated signal and a local oscillator signal;
• generating the analog signal at an intermediate frequency in response to detection of the modulated signal and the local oscillator signal;
• switching at least one counter in the plurality of counters from a first operating mode to a second operating mode independent of operating modes of other counters in the plurality of counters;
• and
• changing a count in the at least one counter in response to at least one pulse in the series of pulses.

A method of counting pulses in a series of pulses representing an analog signal in at least one unit cell in an array of unit cells, wherein the at least one unit cell includes a first counter and a second counter, the method comprising:

• generating in-phase and quadrature control signals;
• switching the first counter between a count-up mode and a count-down mode in response to the in-phase control signal;
• switching the second counter between the count-up mode and the count-down mode in response to the quadrature control signal;
• and
• changing a count in at least one of the first counter and the second counter in response to at least one pulse in the series of pulses.