# US 9,435,838 B1 · Dynamic multi-mode radiometer system with quantized noise injection for automated calibration and method of automated calibration

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- Number: US 9,435,838 B1
- Document ID: US9435838B1
- Status: Granted
- Kind: B1
- Application number: 14/623,581
- Filed: 2015-02-17
- Granted: 2016-09-06
- Earliest claimed: 2015-02-17
- Assignees: Lockheed Martin Corporation
- Applicants: Lockheed Martin Corporation
- Inventors: William Scott McKinley; Eugene Fischer
- Web page: https://patentgrep.com/patent/US9435838B1

## CPC

- G01K 11/006: {using measurement of the effect of a material on microwaves or longer electromagnetic waves, e.g. measuring temperature via microwaves emitted by the object (G01K17/003, G01J5/00 take precedence; measuring the effect of a material on X-, gamma- or particle radiation G01K11/30)}
- G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00)

## Abstract

Embodiments are directed to a dynamic multi-mode radiometer system and method for automated calibration of the system. In an embodiment, the system comprises a radiometer channel including an input selective low noise amplifier (LNA) and radiometer receiver. The LNA comprises a first input and second input and an output coupled to the radiometer receiver. The system includes an antenna coupled to the first input and a reference load selectively connected to the second input, the reference load configured to produce a first signal representative of a reference temperature. The system includes an internal calibrated noise generator selectively connected to the second input of the LNA and includes an internal noise source for producing a second signal representative of an injected noise temperature. The generator is configured to calibrate the radiometer receiver as a function of the injected noise temperature equalized to the reference temperature.

## Claims

### Claim 1

A system comprising:
a radiometer channel including an input selective low noise amplifier (LNA) and a radiometer receiver, the LNA comprising a first input and a second input and an output coupled to the radiometer receiver;
an antenna coupled to the first input of the LNA;
a reference load coupled to the second input of the LNA and configured to produce a first signal representative of a reference temperature; and
an internal calibrated noise (ICN) generator selectively connected to the second input of the LNA and having an internal noise source for producing a second signal representative of an injected noise temperature, the ICN generator being configured to calibrate the radiometer receiver as a function of the injected noise temperature equalized to the reference temperature.

### Claim 2 (depends on 1)

The system of claim 1, wherein the ICN generator comprises:
an analog attenuator controlled to equalize the injected noise temperature to the reference temperature to produce an equalized noise temperature signal; and
a digital attenuator configured to produce a plurality of quantized attenuated representations of the equalized noise temperature signal.

### Claim 3 (depends on 1)

The system of claim 1, wherein the radiometer channel comprises another radiometer receiver; and the LNA comprises a second output coupled to said another radiometer receiver.

### Claim 4 (depends on 1)

The system of claim 1, further comprising a switch comprising:
a first input node coupled to the reference load;
a second input node coupled to the ICN generator; and
an output coupled to the second input of the LNA.

### Claim 5 (depends on 1)

The system of claim 1, further comprising a computing device operable to control the radiometer channel to output only scene data from the antenna at the output of the LNA when in a total power radiometer mode; and to output synchronized signals of the scene data from the antenna and the first signal from the reference load during a Dicke mode.

### Claim 6 (depends on 5)

The method of claim 5, wherein the LNA is a balanced switchless LNA with parallel amplifier channels with at least one amplifier channel controlled to generate the first signal and the second signal at the second output of the LNA at different phases.

### Claim 7 (depends on 1)

The system of claim 1, further comprising an array, wherein the array comprises:
a plurality of radiometer channels, each radiometer channel having coupled thereto an associated antenna and an associated reference load wherein the internal calibrated noise generator is shared by the array.

### Claim 8

A method comprising:
providing a radiometer channel including an input selective low noise amplifier (LNA) and a radiometer receiver, the LNA comprising a first input and a second input and an output coupled to the radiometer receiver;
coupling an antenna to the first input of the LNA;
coupling selectively a reference load to the second input of the LNA to produce a first signal representative of a reference temperature; and
coupling selectively an internal calibrated noise (ICN) generator to the second input of the LNA, the ICN generator having an internal noise source for producing a second signal representative of an injected noise temperature; and
calibrating the radiometer receiver as a function of the injected noise temperature equalized to the reference temperature.

### Claim 9 (depends on 8)

The method of claim 8, wherein the calibrating comprises:
controlling an analog attenuator to equalize the injected noise temperature to the reference temperature to produce an equalized noise temperature signal; and
quantizing at different attenuation levels the equalized noise temperature signal to produce a plurality of quantized attenuated representations of the equalized noise temperature signal.

### Claim 10 (depends on 9)

The method of claim 9, further comprising:
coupling to the radiometer channel another radiometer receiver wherein the LNA comprises a second output coupled to said another radiometer receiver;
continuously receiving scene data at said radiometer receiver via the LNA; and
selectively receiving the first signal and the second signal at said another radiometer receiver via the LNA.

### Claim 11 (depends on 10)

The method of claim 10, wherein the LNA is a balanced switchless LNA with parallel amplifier channels and further comprising:
controlling at least one amplifier channel of the parallel amplifier channels to generate the first signal and the second signal at the second output of the LNA at different phases.

### Claim 12 (depends on 8)

The method of claim 8, further comprising controlling, by a computing device, the radiometer channel to output only scene data from the antenna at the output of the LNA when in a total power radiometer mode and to output synchronized signals of the scene data from the antenna and the first signal from the reference load during a Dicke mode.

### Claim 13

A system comprising:
a plurality of radiometer channels, each radiometer channel including an input selective low noise amplifier (LNA) and a radiometer receiver, the LNA comprising a first input and a second input and an output coupled to the radiometer receiver;
a plurality of antennas, a respective one antenna coupled to the first input of the LNA of a corresponding radiometer channel;
a plurality of reference loads, a respective one reference load coupled to the second input of the LNA of the corresponding radiometer channel, the respective one reference load configured to produce a first signal representative of a reference temperature; and
an internal calibrated noise (ICN) generator selectively connected to the second input of the LNA of each radiometer channel of the plurality of radiometer channels, the ICN generator having an internal noise source for producing a second signal representative of an injected noise temperature and being configured to calibrate the radiometer receiver of each radiometer channel as a function of the injected noise temperature equalized to the reference temperature.

### Claim 14 (depends on 13)

The system of claim 13, wherein the ICN generator comprises:
an analog attenuator controlled to equalize the injected noise temperature to the reference temperature of said each radiometer channel to produce an equalized noise temperature signal for said each radiometer channel; and
a digital attenuator configured to produce a plurality of quantized attenuated representations of the equalized noise temperature signal for said each radiometer channel.

### Claim 15 (depends on 13)

The system of claim 13, wherein said each radiometer channel comprises another radiometer receiver; and each LNA comprises a second output coupled to said another radiometer receiver of the corresponding radiometer channel.

### Claim 16 (depends on 13)

The system of claim 13, further comprising a plurality of switches, each switch of the plurality of switches being coupled to an associated radiometer channel comprising:
a first input node coupled to the reference load of the associated radiometer channel;
a second input node coupled to the ICN generator; and
an output coupled to the second input of the LNA of the associated radiometer channel.

### Claim 17 (depends on 13)

The system of claim 13, further comprising a computing device operable to control the plurality of radiometer channels to output only scene data from the plurality of antennas at the output of the LNA of said each corresponding radiometer channel when in a total power radiometer mode; and to output synchronized signals of the scene data from the plurality of antennas and the first signal from the reference load associated with said each corresponding radiometer channel during a Dicke mode.

### Claim 18 (depends on 17)

The system of claim 17, wherein the LNA is a balanced switchless LNA with parallel amplifier channels with at least one amplifier channel controlled to generate the first signal and the second signal at the second output of the LNA at different phases.

### Claim 19 (depends on 13)

The system of claim 13, further comprising a plurality of arrays, each array comprising:
the plurality of radiometer channels, the plurality of antennas, a plurality of reference loads and the ICN generator.

### Claim 20 (depends on 19)

The system of claim 19, wherein the plurality of radiometer channel comprises four radiometer channels wherein the ICN generator is shared by the plurality of radiometer channels of an array.