Paul D. Biernacki

A two-channel optical downconverter for phase detection

Experimental results for a two-channel optical downconverter link operating from 2 to 18 GHz are presented. Using low-noise preamplifiers results in a noise figure (NF) of 8.5-14 dB over the frequency range of 2-18 GHz. For the first time, relative phase measurements between optically downconverted signals have been performed. An in-phase/quadrature phase-measurement technique indicates a phase precision of /spl plusmn/2/spl deg/ with as little as -60 dBm radio frequency (RF) received power. Comparing the optical microwave downconverter to an electrical microwave downconverter in terms of phase detection reveals similar performance between the two systems.

Demonstration of a wide-band image rejection microwave downconverter

A photonic image-rejection downconverter capable of down-converting radio-frequency (RF) signals over a range of 5-18 GHz into an IF band 2.1 GHz wide (3.3-5.4 GHz) is presented. RF signals received by the system are first up-converted into the passband of a 21.3-23.4-GHz filter, and then optically down-converted to 3.3-5.4 GHz. The system exhibited better than 60 dB of image rejection over its entire bandwidth and spurious signals resulting from harmonic mixing products were more than 25 dB below the downconverted signal.

RF phase-noise performance of a two-channel optical downconverting link for microwave phase detection

The phase-noise performance of a low-noise preamplified two-channel optical downconverting link is measured for the first time. The downconverter is capable of operation over a 2-18-GHz bandwidth with a fixed intermediate frequency of 160 MHz. Results show that a two-channel configuration used as a remote microwave phase detector exhibits performance equivalent to a typical microwave mixer.

Photonic signal processing for microwave applications

The use of photonic techniques for microwave signal processing has the potential to bring improved performance and new capabilities to RF and microwave systems. Due to this promise, a large number of organizations are vigorously pursuing the processing of signals using photonics. Several recent demonstrations have illustrated the increasing maturity of the field. Here, we briefly present the motivations behind this growing effort and review the current capabilities of photonics.

Range demonstration of an ultra-wideband, continuous, time steered array using a fiber-optic, cascaded grating prism

We demonstrate an ultra-wideband fiber optic true time-delay receive beamformer using a chirped grating architecture of identical, cascaded gratings provided continuous, time-delay of up to 2.4 ns. The beamformer system was built using commercially available components, and is capable of continuous tuning over /spl plusmn/60/spl deg/, with an instantaneous bandwidth of 14 GHz.

A four channel angle of arrival detector using optical downconversion

A fiber-optic system for microwave angle of arrival measurements is demonstrated in an anechoic chamber for the first time. The system consists of a four-channel optical downconverter capable of processing received signals from 2-18 GHz. Direction resolution is determined by the antenna spacing, and at 10 GHz is spatially better than 0.1.

Microwave phase detection for angle of arrival detection using a 4-channel optical downconverter

Fiber optic links maintain an advantage over traditional microwave transmit and receive systems in terms of multi-octave operation and RF isolation, and the ability to remote microwave signals great distances. For the first time, a 4-channel optical downconverter capable of detecting the relative microwave phase of incoming microwave signals up to 18 GHz is tested. The phase information can be related to angle of arrival detection. We present the first results of a 4-channel remotable optical downconverter used for phase detection of incoming signals up to 18 GHz. The phase information is related to angle of arrival detection.

Noise effects in polarization maintaining optical amplifiers

Excessive noise generation in optically amplified analog fiber optic systems due to different polarization-maintaining EDFA configurations is investigated. Increases in the effective RIN level of more than 20 dB are predicted and experimentally observed for double-pass configurations.

Dynamic range comparison of ultrawide-band photonic downconverters

Dynamic range of alternative configurations for a single-channel cascaded-MZM downconverter are compared for the first time to our knowledge. Increased RIN in an optically amplified setup may outweigh increased RF power gain in ultrawideband systems.

An ultrawideband image rejecting microwave downconverter using WDM

A microwave-photonic frequency shifting system capable of 60 dB image rejection over a DC to 18 GHz bandwidth is described. The final IF band can exist within the original RF frequency range with 60 dB isolation. The system allows antenna remoting via optical fiber, and maintains phase coherence through the use of WDM techniques.