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Detectors

Phiar’s diodes couple well with antennas and are optimized for detection. Phiar has validated its detectors at 200 GHz and 1 THz. (Some early work reached into the infrared spectrum at 10 µm / 30 THz, but Phiar is focused on opportunities between DC and 3 THz.)

The simplest possible Phiar detector is essentially a “crystal radio” with the diode serving as the “crystal” as seen in Figure 1.

Phiar’s MIIM diodes can be directly integrated into antennas. The micrograph above is a tiny “crystal radio” where rectified signals can be coupled directly to the load. This early Phiar detector (vintage 200X), was an MIM diode where the antenna lobes were made of the same dissimilar metals used in the diode itself. The antenna and diode were built in three deposition steps: one for each metal layer, and one for the oxide layer between them.

Phiar diodes can be used to rectify high frequency signals directly when connected with appropriately matched antennas of nearly any type. Phiar’s technology is agnostic to modulation technique and is a viable solution for frequencies from DC to 3 THz. Unlike many other THz detectors available today, Phiar’s technology operates at room temperature: No matter the frequency, Phiar’s detectors never require liquid nitrogen cooling.

Phiar’s is currently developing detectors for 60 GHz wireless personal area networks (WPANs) and 77 GHz automotive radar (adaptive cruise control). Demo kits containing Phiar’s detectors are available Summer 2006 from Phiar at 60 GHz and 77 GHz. Contact us, if you are interesting in obtaining a demo kit.

Challenges at high frequencies

As RF technologies continue to push into higher frequency regimes, new challenges face designers. For mm-wave and sub-mm-wave radios a seminal challenge is maintaining sizable antenna gains while preserving RF signal integrity.

Antenna Arrays

At 60 GHz and above, regulatory power limits, atmospheric attenuation and multi-path signal propagation force RF engineers to use antenna arrays to boost gain. To steer RF beams and affect this gain, arrays must alter their properties on the fly. This requires supporting electronics be as close as possible to the antennas themselves so that switching is fast and high frequency signal loss is minimal.

Phiar electronics can help engineers overcome this challenge by integrating beam steering electronics, antennas and detector diodes onto the same low cost substrate.

Geometry as a Filter

When one pushes RF signals to very high carrier frequencies, complications arise that are not present at lower frequencies. In a bowtie detector like the one shown in Figure 1, carrier frequency signals can leak out of the detector prior to being rectified. The higher the carrier frequency, the worse this problem becomes. Any loss of un-rectified signal reduces the detector’s efficiency.

Phiar has overcome this challenge with an elegant solution. An example of a particularly effective high frequency scheme is Phiar’s patented “Edge-Fed Antenna” design seen in Figure 2.

At high frequencies, an integrated Phiar bowtie antenna with detection diode is far more effective when the leads for the supporting electronics are located at the edges of the antenna lobes. As seen in the color coding, this simulation shows the high lower concentration of 200 GHz carrier frequency is localized at the diode at the center of the antenna lobes, with the 20 GHz signal frequency concentrated at the leads at the top of the diagram.

By tapping signal at the edges of an integrated antenna/diode, Phiar’s design passively focuses the incoming high frequency carrier + signal energy at the diode in the center of the detector, where it is rectified. The extracted lower frequency data signal migrates to the detector’s edges where the data signal leads are located. This improves device efficiency because nearly all of the high frequency signals remain at the diode. Thus, Phiar has created an elegant means of focusing high frequency signals for maximal rectification efficiency, simply by moving the detector’s leads to the edges of the device.

What are your needs? Click here to connect with Phiar to learn more about our detectors.