Systems and methods for automatic level control (ALC) are provided. In one embodiment, an ALC system for communications signals comprises: a multi-threshold programmable ALC controller; and at least one signal path that includes: a digital step attenuator configured to receive an analog communications signal and attenuate the analog communications signal in response to an attenuation adjustment signal from the ALC controller; and an analog-to-digital converter configured to receive the analog communications signal as attenuated by the digital step attenuator and generate samples of the attenuated analog communications signal, wherein the ALC controller receives the samples. The ALC controller comprises a plurality of clip detectors that function in parallel. Each of the clip detectors are programmed with a respective amplitude and time threshold. Based on which of the plurality of clip detectors determine that the samples exceed their respective amplitude and time threshold, the ALC controller generates the attenuation adjustment signal.

Systems and methods of transmitting direct detection optical signal are provided. A direct detection optical transmitter according to illustrative embodiments includes a Mach Zehnder Modulator (MZM) configured to modulate laser light based on an electrical drive signal to generate a modulated optical signal and a complementary-modulated optical signal. The optical transmitter includes an optical finite impulse response (FIR) filter configured to receive the complementary-modulated optical signal and generate a filtered optical signal. The optical transmitter includes a polarization rotator configured to receive the filtered optical signal and output a rotated optical signal. The optical transmitter includes an optical combiner configured to combine the modulated optical signal and the rotated optical signal. The optical transmitter includes an output port configured to output the combined optical signal.

A waveform shaping device that includes an adaptable surface, a controller, and a receiving device which measures a secondary wave following the reception of a primary wave by a receiver, the primary wave having been transmitted by a transmitter. Based on the measurement of the secondary wave, the controller determines an estimated value for optimization of the adaptable surface, without any connection to the receiver.

An intelligent backhaul radio that has an advanced antenna system for use in PTP or PMP topologies. The antenna system provides a significant diversity benefit. Antenna configurations are disclosed that provide for increased transmitter to receiver isolation, adaptive polarization and MIMO transmission equalization. Adaptive optimization of transmission parameters based upon side information provided in the form of metric feedback from a far end receiver utilizing the antenna system is also disclosed.

An apparatus, comprising: circuitry configured, in response to receipt of input data, to transmit a stream of symbols of a constellation to a modulator for modulation onto a carrier wherein a frequency of occurrence of symbols in the stream is dependent upon a probability-amplitude distribution for symbols of the constellation, wherein the probability-amplitude distribution has a kurtosis less than a target value and a shape of the probability-amplitude distribution causes low-amplitude symbols to occur more frequently on average in the stream than high-amplitude symbols.

A method of compensating electromagnetic emissions of a device for use in a communication bus, the method including: transmitting a test signal over the communication bus; receiving, at the device, the test signal after propagation over the communication bus; performing frequency analysis processing of the test signal received to detect a set of harmonic components of the test signal received having an amplitude exceeding a certain threshold; storing respective values of frequency of harmonic components in the set of harmonic components having an amplitude exceeding the certain threshold; and generating and transmitting over the communication bus a set of compensation signals, each compensation signal in the set of compensation signals being a sinusoidal signal having a respective frequency equal to one of the frequencies stored, and being in anti-phase with respect to the harmonic component of the test signal received having the respective frequency.

A method implementing the same frequency-time transform of size M irrespective of the service. The method adds, during a frame setup, a cyclic extension of L=L.sub.1+L.sub.2 samples in order to obtain a sequence of M+L samples. The method carries out a time-domain filtering according to a function (n) of the samples n of the sequence of M+L samples.

Systems and methods for automatic level control (ALC) are provided. In one embodiment, a system comprises a multi-threshold programmable ALC controller; and at least one signal path that includes: a digital step attenuator to receive an analog communications signal and attenuate the communications signal in response to an attenuation adjustment signal from the ALC controller; and an analog-to-digital converter configured to receive the communications signal as attenuated by the digital step attenuator, wherein the ALC controller receives complex IQ samples of the attenuated communication signal; wherein the ALC controller comprises a plurality of clip detectors that function in parallel, wherein each of the clip detectors are programmed with a respective amplitude and time threshold, wherein based on which of the plurality of clip detectors determine that the complex IQ samples exceed their respective amplitude and time threshold, the ALC controller generates the attenuation adjustment signal to the digital step attenuator.

A communication system in which multiple shaping codes are selectively and iteratively used to encode a data frame such that possible energy inefficiencies associated with the use of constant-probability codes and/or transmission of dummy constellation symbols can be relatively small. In an example embodiment, the used shaping codes have different respective code rates, and a code selector of the shaping encoder operates to select one of the shaping codes by adaptively matching the rate of the code to the effective rate needed to efficiently encode the unprocessed portion of the data frame. The encoding is carried out in a manner that enables the shaping decoder to unequivocally determine the shaping codes that have been used for encoding each particular data frame based on the same rate-matching criteria as those used by the shaping encoder. At least some embodiments advantageously lend themselves to being implemented using circuits of relatively low complexity.

An adaptive frequency equalizer for wide modulation bandwidth envelope tracking (ET) is provided. In this regard, an ET integrated circuit (ETIC) provides an ET power signal for one or more power amplifiers (PAs). A voltage error can occur in the ET power signal due to variable impedance sources, such as a variable load impedance at the PA and a variable trace inductance between the ETIC and the PA. The adaptive frequency equalizer disclosed herein works to adaptively correct for such voltage errors to provide improved overall power signal tracking at the PA, especially where there is a large trace inductance from the ETIC being located several centimeters (cm) away from the PA. Thus, embodiments of the adaptive frequency equalizer enhance ET performance for radio frequency (RF) systems having a modulation bandwidth of 100 megahertz (MHz) or above.