CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of and priority to U.S. patent application Ser. No. 16/198,287, filed on Nov. 11, 2018, now U.S. Pat. No. 10,630,391, issued on Apr. 21, 2020, the entire disclosure of which is incorporated by reference as if set forth in its entirety herein.

TECHNICAL FIELD

Embodiments described herein generally relate to RF signal processing and, more particularly but not exclusively, to systems and methods for improving the dynamic range of RF receivers or digitizers.

BACKGROUND

Radio Frequency (RF) receivers have finite instantaneous dynamic range (IDR), which limits their ability to receive weak signals in the presence of strong signals. The weakest link in RF communications is typically the analog-to-digital converter (ADC). However, analog components such as amplifiers can limit performance as well. While automatic gain control (AGC) allows a system to operate at different input power levels, it does not improve the IDR.

Unchecked interference from strong signals may either de-sense the receiver or saturate it in ways that cannot be filtered or counteracted in digital post-processing. Beyond the blunt force AGC and front-end attenuation approach, more focused existing techniques for protecting RF receivers involve analog filtering at the front end. These analog filters are often configured as band-reject or notch filters. In addition active cancelers may also be used in cases in which a tap or a sample of the interference is available.

The modern electromagnetic (EM) environment is both dense and dynamic. This is particularly true for mobile platforms. In some applications, some form of EM spectral monitoring is paired with tunable or switched filters or blanking strategies. However, these existing techniques do not provide the optimal combination of fast tuning speed, low loss, linearity, spectral precision, and wide tuning range that is required in certain environments.

A need exists, therefore, for systems and methods for reducing interference in RF communications that overcome the shortcomings of existing techniques.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description section. This summary is not intended to identify or exclude key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

According to one aspect, embodiments relate to an RF processing system. The system includes an optical storage module configured to receive, delay, and release a first signal; a processing module configured to receive a second signal and create a modulation signal based on the received second signal; and an electro-optical modulation module in operable communication with the optical storage module and the processing module, wherein the electro-optical modulation module is configured to receive the first signal from the optical storage module, receive the modulation signal from the processing module, and electro-optically modulate the first signal based on the modulation signal.

In some embodiments, the system further includes a control subsystem configured to automatically control at least one of the optical storage module, the processing module, and the electro-optical modulation module.

In some embodiments, the processing module includes a first analog-to-digital converter and a first digital-to-analog converter, and the first analog-to-digital converter is configured to generate a coarse digital estimate that is provided as input to the first digital-to-analog converter to provide an analog output to the electro-optical modulation module for removal from the first signal resulting in a residue signal. In some embodiments, the system further includes a second analog-to-digital converter receiving said residue signal and a digital signal processing module in operable communication with the first analog-to-digital converter and the first digital-to-analog converter, wherein the digital signal processing module is configured to receive a feedback signal of a digital residual estimate from the second analog-to-digital converter and perform at least one operation to modify the coarse digital estimate of the second signal to alter the modulation of the first signal. In some embodiments, the at least one operation includes at least one of a linear operation, a non-linear operation, a linear filter operation, a nonlinear filter operation, a linearization operation, an adaptive filter operation, a nonlinear adaptive filter operation, an equalization operation, an adaptive equalization operation, a scaling operation, a delaying operation, a phase shifting operation, a dispersion compensation operation, a complex value function-based operation, and an amplitude/phase transformation. In some embodiments, the feedback signal is selected from the group consisting of an open loop signal, a closed loop signal, a dither-based signal, and a cross-correlation based signal.

In some embodiments, the first signal is an analog RF signal.

In some embodiments, the second signal is selected from the group consisting of an analog signal, a digital signal, and a combination of an analog and digital signal.

In some embodiments, the second signal is received from a source selected from the group consisting of a sensor device, a timer, a geo-location device, and an external receiver.

In some embodiments, the electro-optical modulation module is configured to modulate the first signal by at least one of removing a feature from the first signal, adding a feature to the first signal, linearly modifying the first signal, and nonlinearly modifying the first signal.

In some embodiments, the second signal is derived from the first signal. In some embodiments, the system further includes a splitter to create at least a portion of the second signal from the first signal.

In some embodiments, the second signal is received in a baseband or intermediate frequency form.

In some embodiments, the second signal is received from one or more separate antennas or antenna beams of a phased array antenna.

According to another aspect, embodiments relate to an RF processing system. The system includes a tap device configured to receive an input signal and split the input signal into a first signal and a second signal; a delay module configured to receive and delay the first signal to create a delayed first signal; a processing module configured to receive the second signal and create a modulation signal based on the received second signal thereby producing a latency in the modulation signal that matches the delay of the delayed first signal, wherein the modulation signal contains estimates of undesired components; and an electro-optical modulation module in operable communication with the delay module and the processing module, wherein the electro-optical modulation module is configured to receive the delayed first signal, receive the modulation signal containing estimates of undesired components from the processing module, and subtract the estimated undesired components from the delayed first signal to produce a low amplitude signal.

In some embodiments, the system further includes a digital signal processor output module configured to digitally combine digitized copies of the low amplitude signal and the modulation signal estimating the high amplitude components to create a high dynamic range version of the input signal.

In some embodiments, the delay module includes an electrical-to-optical converter configured to convert the first signal to a modulated optical signal and hold the modulated optical signal in an optical delay to produce the delayed first signal. In some embodiments, the electro-optical modulation module includes an optical modulator and an optical-to-electrical converter, wherein the optical modulator receives the delayed first signal and the modulation signal and is further configured to modulate the delayed first signal to remove a filtered reference signal to produce a twice-modulated optical signal that is converted to a residual electrical signal output with regulated dynamic range by the optical-to-electrical converter.

In some embodiments, the delay module is optically implemented by at least one of a fiber optic transmitter, a fiber optic delay, and a fiber optic receiver.

In some embodiments, the system further includes at least one signal modifier in the delay module for modifying the delayed first signal.

According to yet another aspect, embodiments relate to an interference cancellation system. The system includes a first high dynamic range receiver configured to receive a first signal; at least one second high dynamic range receiver configured to receive at least one reference signal including interference; and a digital signal post processing module configured to receive the first signal, receive the at least one reference signal including interference, and remove the interference from the first signal.

