Near-field terahertz imager
The present disclosure concerns a high frequency imager including a pixel matrix, each pixel including a high frequency oscillator, a transmission line positioned at a distance from an active surface of the imager smaller than the operating wavelength of the oscillator, a first end of the line being coupled to the oscillator, and a read circuit coupled to a second end of the line.
1. A high frequency imager, comprising:
a pixel matrix, each pixel comprising:
a high frequency oscillator;
a transmission line positioned at a distance from an active surface of the imager smaller than the operating wavelength of the oscillator, a first end of the line being coupled to the oscillator; and
a read circuit coupled to a second end of the line.
2. The imager of claim 1 , wherein the read circuit of each pixel provides a signal representative of an impedance of the transmission line.
3. The imager of claim 1 , wherein the oscillator of each pixel comprises second transmission lines.
4. The imager of claim 3 , wherein a layer adapted to block the propagation of the high frequency waves covers at least the second lines.
5. The imager of claim 3 , wherein the read circuit of a pixel provides a signal representative of a frequency of the oscillator of the pixel.
6. The imager of claim 1 , wherein the transmission lines are of the microstrip type.
7. The imager of claim 1 , adapted to operate at a frequency selected in a range of 0.3 to 3 THz.
8. An imaging circuit, comprising:
a semiconductor support;
an insulating layer formed on the semiconductor support, the insulating layer having an active surface;
a pixel matrix formed in the semiconductor support and the insulating layer, the pixel matrix including a plurality of pixels each including,
an oscillator circuit having an operating wavelength;
a read circuit; and
a first transmission line coupled between the oscillator circuit and the read circuit, the first transmission line being formed in the insulating layer at a distance from the active surface that is less than the operating wavelength of the oscillator circuit.
9. The imaging circuit of claim 8 wherein the first transmission line of each pixel comprises a coplanar transmission line.
10. The imaging circuit of claim 8 , wherein the first transmission line of each pixel comprises a microstrip transmission line including a microstrip portion and a conductive band portion, the microstrip portion being formed in the insulating layer at the distance from the active surface and the conductive band portion being formed on a surface of the semiconductor support.
11. The imaging circuit of claim 10 , wherein the oscillator circuit of each pixel includes a plurality of second transmission lines.
12. The imaging circuit of claim 11 , wherein each of the plurality of second transmission lines comprises a microstrip transmission formed in the insulating layer.
13. The imaging circuit of claim 12 , wherein each of the plurality second transmission lines further comprises a shielding layer formed on the active surface of the insulating layer.
14. The imaging circuit of claim 13 , wherein the shielding layer is formed on the active surface over the oscillator circuits and over the read circuits but not covering the first transmission lines.
15. The imaging circuit of claim 14 , wherein each of the second transmission lines forms an inductive component of the oscillator circuit.
16. The imaging circuit of claim 15 , wherein each oscillator circuit comprises a ring oscillator circuit including N inverters, N being an odd integer, and wherein the second transmission lines interconnect the N inverters.
17. The imaging circuit of claim 8 , wherein the semiconductor support comprises one of a bulk silicon substrate and a silicon-on-insulator substrate.