Wireless sensor platform for harsh environments

• US 7,562,581 B2
• Filed: 09/29/2006
• Issued: 07/21/2009
• Est. Priority Date: 09/29/2005
• Status: Expired due to Fees

• Current Assignee: Case Western Reserve University
• Original Assignee: Case Western Reserve University
• Inventors: Yu, Xinyu, Toygur, Lemi, He, Yunli, Garverick, Steven L.
• Primary Examiner(s): Caputo; Lisa M
• Assistant Examiner(s): ROY, PUNAM P
• Application Number:
  US11/537,488
• Publication Number:
  US 20070186668A1
• Time in Patent Office: 1,026 Days
• Field of Search: 737/77, 324/160, 330/303
• US Class Current: 73/777
• CPC Class Codes: G01D 3/036 on measuring arrangements themselves
• CPC Class Codes: G01L 19/086 for remote indication

Abstract

Reliable and efficient sensing becomes increasingly difficult in harsher environments. A sensing module for high-temperature conditions utilizes a digital, rather than analog, implementation on a wireless platform to achieve good quality data transmission. The module comprises a sensor, integrated circuit, and antenna. The integrated circuit includes an amplifier, A/D converter, decimation filter, and digital transmitter. To operate, an analog signal is received by the sensor, amplified by the amplifier, converted into a digital signal by the A/D converter, filtered by the decimation filter to address the quantization error, and output in digital format by the digital transmitter and antenna.

Claims

1. A system that facilitates reliable sensing in harsh environments, comprising:

a sensor that receives a signal;

an integrated circuit that processes the signal to provide an output signal, the integrated circuit comprising;

an amplifier that amplifies the signal in analog format to provide an amplified analog signal, the amplifier has a bandwidth that is locked to a clock frequency of a clock signal, the clock frequency is proportional to;

g_m/C

where g_m represents transconductance of biasing transistors in an oscillator that provides the clock signal and C represents capacitance of a load capacitor of the oscillator;

an output circuit portion configured to process the amplified signal to provide the output signal as including at least one of an analog output and a digital output based on the amplified analog signal; and

a biasing circuit configured to provide constant-gm biasing to the amplifier and to the output circuit portion to maintain gain and bandwidth thereof over temperature; and

an antenna that implements wireless transmission of the output signal.

2. A system that facilitates reliable sensing in harsh environments, comprising:

a sensor that receives a signal;

an integrated circuit that processes the signal to provide an output signal, the integrated circuit comprising;

an amplifier that amplifies the signal in analog format to provide an amplified analog signal;

an output circuit portion configured to processes the amplified signal to provide the output signal as including at least one of an analog output and a digital output based on the amplified analog signal; and

a biasing circuit configured to provide constant-gm biasing to the amplifier and to the output circuit portion to maintain gain and bandwidth thereof over temperature;

an antenna that implements wireless transmission of the output signal; and

a digital transmitter that includes a voltage-controlled oscillator and transmits the signal via the antenna based on the digital output, wherein the digital transmitter comprises a digital frequency-shift keying (FSK) transmitter comprising;

a buffer coupled to receive the digital output from the output circuit portion to provide a buffered output signal;

a tank circuit configured to resonate at a carrier frequency and providing an oscillator output signal in response to the buffered output signal, the oscillator output signal driving the antenna to implement wireless transmission of the digital output, wherein the tank circuit further comprises;

a varactor driven by the buffered output signal;

a tunnel diode coupled to an output of the varactor; and

a planar loop antenna coupled to the output of the varactor, the planar loop antenna having an inductance and a resistance that combine with capacitance of the varactor and the tunnel diode to form the tank circuit, the loop antenna providing the wireless transmission of the digital output.

3. A system that facilitates reliable sensing in harsh environments, comprising:

a sensor that receives a signal;

an integrated circuit that processes the signal to provide an output signal, the integrated circuit comprising;

an amplifier that amplifies the signal in analog format to provide an amplified analog signal;

an output circuit portion configured to process the amplified signal to provide the output signal as including at least one of an analog output and a digital output based on the amplified analog signal; and

a biasing circuit configured to provide constant-gm biasing to the amplifier and to the output circuit portion to maintain gain and bandwidth thereof over temperature, wherein the biasing circuit further comprises;

a plurality of transistors configured as a current mirrors to provide the constant-g_m biasing for the integrated circuit, such that transconductance of transistors in the integrated circuit that are biased by the biasing remain substantially constant over temperature

a biasing resistor through which a biasing current is provided, the transconductance of the transistors in the integrated circuit that are biased based on the biasing current is inversely proportional to a resistance of the biasing resistor; and

an antenna that implements wireless transmission of the output signal.

4. The system of claim 3, wherein the biasing resistor comprises a poly 1 biasing resistor having a known temperature coefficient.

5. A system that facilitates reliable sensing and signal processing in harsh environments, comprising:

an integrated circuit that processes an analog signal provided by an external sensor, the integrated circuit comprising;

an amplifier that amplifies the analog signal to provide an amplified analog signal;

an output circuit portion configured to process the amplified signal to provide at least a corresponding digital output based on the amplified analog signal; and

a biasing circuit configured to provide constant-gm biasing to the amplifier and to the output circuit portion to maintain gain and bandwidth over temperature thereof, wherein the biasing circuit further comprises;

a plurality of transistors configured as a current mirrors to provide the constant-g_m biasing for the integrated circuit, such that transconductance of transistors in the integrated circuit biased by the biasing remain substantially constant over temperature; and

a biasing resistor through which a biasing current is provided, the transconductance of the transistors in the integrated circuit that are biased based on the biasing current being inversely proportional to a resistance of the biasing resistor.

6. A system that facilitates reliable sensing and signal processing in harsh environments, comprising:

an integrated circuit that processes an analog signal provided by an external sensor, the integrated circuit comprising;

an amplifier that amplifies the analog signal to provide an amplified analog signal;

an output circuit portion configured to process the amplified signal to provide at least a corresponding digital output based on the amplified analog signal; and

a biasing circuit configured to provide constant-gm biasing to the amplifier and to the output circuit portion to maintain gain and bandwidth over temperature thereof;

a digital transmitter that includes a voltage-controlled oscillator that provides a modulated output signal based on the corresponding digital output provided by the output circuit portion of the integrated circuit, wherein the digital transmitter comprises a digital frequency-shift keying (FSK) transmitter comprising;

a buffer coupled to receive the digital output from the output circuit portion to provide a buffered output signal;

a tank circuit configured to resonate at a carrier frequency and providing an oscillator output signal, corresponding to the modulated output signal, in response to the buffered output signal, the oscillator output signal driving the antenna to implement the wireless transmission of the digital output, wherein the tank circuit further comprises;

a varactor driven by the buffered output signal;

a tunnel diode coupled to an output of the varactor; and

a planar loop antenna coupled to the output of the varactor, the planar loop antenna having an inductance and a resistance that combine with capacitance of the varactor and the tunnel diode to form the tank circuit, the loop antenna providing for the wireless transmission of the digital output; and

an antenna configured to wirelessly transmit the modulated output signal.

7. A system that facilitates reliable sensing and signal processing in harsh environments, comprising:

an integrated circuit that processes an analog signal provided by an external sensor, the integrated circuit comprising;

an amplifier that amplifies the analog signal to provide an amplified analog signal;

an output circuit portion configured to process the amplified signal to provide at least a corresponding digital output based on the amplified analog signal;

a biasing circuit configured to provide constant-gm biasing to the amplifier and to the output circuit portion to maintain gain and bandwidth over temperature thereof, wherein the biasing circuit further comprises a plurality of transistors configured as a current mirrors to provide the constant-g_m biasing for the integrated circuit, such that transconductance of transistors in the integrated circuit biased by the biasing remain substantially constant over temperature; and

an oscillator that provides a clock signal having a frequency, the oscillator being biased by the substantially constant-g_m biasing provided by the biasing circuit so that the frequency of the clock signal is resistant to temperature changes.