Nonlinear interference suppressor for varying-envelope local interference in multimode transceivers

In multimode transceivers, a local transmitter may induce a large interference in a local receiver, often several orders of magnitude stronger than the desired received signal. To suppress this interference by linear filtering, the receiver would need a very large dynamic range, resulting in excessive power consumption. A potentially much more power-efficient approach uses an adaptive memoryless nonlinearity that can strongly suppress the interference when adapted proportional to the envelope of the received interference. This approach has so far been limited to constant-envelope interferences owing to the difficulty of extracting accurate interference envelope information from the received signal. In this paper, we observe that in multimode transceivers the locally available baseband interference enables accurate adaptation for varying-envelope interferences. We identify and analyze nonlinear distortion products which are negligible for constant-envelope interferences. We show that adequate interference suppression can be achieved along with a negligible distortion to the desired signal

Nonlinear interference suppressor for varying-envelope local interference in multimode transceivers

In multimode transceivers, a local transmitter may induce a large interference in a local receiver, often several orders of magnitude stronger than the desired received signal. To suppress this interference by linear filtering, the receiver would need a very large dynamic range, resulting in excessive power consumption. A potentially much more power-efficient approach uses an adaptive memoryless nonlinearity that can strongly suppress the interference when adapted proportional to the envelope of the received interference. This approach has so far been limited to constant-envelope interferences owing to the difficulty of extracting accurate interference envelope information from the received signal. In this paper, we observe that in multimode transceivers the locally available baseband interference enables accurate adaptation for varying-envelope interferences. We identify and analyze nonlinear distortion products which are negligible for constant-envelope interferences. We show that adequate interference suppression can be achieved along with a negligible distortion to the desired signal

Adaptive nonlinear interference suppressor for cognitive radio applications

To utilize the radio frequency spectrum efficiently a Cognitive Radio (CR) can operate as a secondary user in a frequency band which is licensed to a primary user. To this end, the CR must sense the spectrum continuously to find empty frequency channels for its transmission. The transmitted signal by the local transmitter of the CR, however, induces a strong local interference in the local receiver of the CR. Hence a half-duplex transceiver is used where the transmit and sense operations are done in separate time slots. The time-slotted operation though, reduces the throughput of the CR. This paper proposes application of an adaptive Nonlinear Interference Suppressor (NIS) to suppress this strong local interference to enable simultaneous transmit and sense. We present experimental results of a transceiver testbed that uses an implementation of the NIS, fabricated in 140 nm CMOS technology. These experiments show that the NIS can substantially suppress the local interference with low complexity and power consumption

Monolithic transformers for high frequency bulk CMOS circuits

This paper presents two monolithic transformer structures exhibiting high self resonance frequencies(fSR). Effect of positive and negative coupling factor on self resonance frequency is investigated. The transformer turn ratio and structure is selected to improve design and ease layout of a high frequency LNA and VCO. Measurement results of a transformer show good agreement with simulated values and demonstrate a coupling factor of 0.7 at 20 GHz

Look-Ahead Based Sigma-Delta Modulation

High resolution analog-to-digital conversion and digital-to-analog conversion is often realized with the use of a Sigma-Delta Modulator (SDM). The sigma-delta modulation process, although very non-linear when a 1-bit quantizer is used, is nowadays well understood and can be made to deliver a very high signal conversion quality. An example system that pushes the traditional sigma-delta modulation algorithm to its performance limit is the Super Audio CD (SA-CD) standard, in which a 64 times oversampled 1-bit signal is used to represent audio content with an SNR of up to 120~dB over 20~kHz bandwidth. Look-Ahead Based Sigma-Delta Modulation presents a number of alternative digital sigma-delta modulation techniques that make use of look-ahead, a process that takes into account the effect of decisions on the future, to realize an even higher conversion quality than possible with traditional sigma-delta modulation. This book provides the reader with a clear overview of various encoding techniques and demonstrates the improvements in signal conversion quality that can be obtained from their use. Starting from the basic full look-ahead approach that requires several orders of magnitude more computational power than a normal SDM, more efficient structures are derived that are able to realize a far higher signal conversion performance at a fraction of the computational cost. In addition to this, a modulator is derived that is able to generate bitstreams that are optimized for SA-CD usage, i.e. a high signal conversion quality combined with minimal signal entropy. All the look-ahead algorithms presented in this book are described in pseudocode and ample simulation results are provided to judge the effects on the signal conversion performance

Measuring RF circuits exhibiting nonlinear responses combined with short and long term memory effects

All RF circuits that incorporate active devices exhibit nonlinear behavior. Nonlinearities result in signal distortion, and therefore state the upper limit of the dynamic range of the circuits. A measure for linearity used quite commonly in RF is the P1dB and/or IP3 point. These quantities are usually measured using a signal generator and a spectrum analyzer. Depending on the quantity of interest (1 P1dB or IP3), a single or two-tone signal is passed through the system. A shortcoming of this type of measurement is that it only quantifies the magnitude of the distortion, and gives no information about the phase. New measurement methodologies using X-parameters circumvent this shortcoming by including phase information as well. This enables more detailed nonlinear measurements, providing the RF designer with more information leading to a higher predictability of the total RF system. For many RF applications this methodology provides sufficient information. In real-life RF systems, the distortion components (harmonics and intermodulation products) can in principle have any phase due to memory effects. The memory effects can sub-divided into two categories, namely short and long term effects. Short term memory exhibits time constants smaller than the symbol time of the modulated signals of interest, and long term memory has time constants which are spread over multiple symbols. The aforementioned X-parameters include only short term memory effects, leading to a certain phase of the distortion products. This limitation of the approach based on X-parameters is due to the fact that only unmodulated constant envelope signals are used (pure sinusoidal signals) as an excitation. In this paper a measurement setup is proposed that captures both the input and output signals, fully in the time domain. Realistic (and in fact any arbitrary) waveforms can be used as excitation, enabling the extraction of both the short and the long term memory effects that are of increasing importance for future wireless systems with complex wideband modulation techniques. To achieve a high accuracy, a noise minimization technique is applied

A 1.8GHz amplifier with 39dB frequency-independent smart self-interference blocker suppression

This paper presents a 1.8GHz RF amplifier implemented in 140nm CMOS with frequency-independent blocker suppression. The functionality is obtained by adaptation of a nonlinear current transfer according to the blocker amplitude. In the presence of a 0-11dBm RF blocker a voltage gain of 7.6 to 9.4dB and IIP3 >;4dBm are measured, while the blocker is suppressed by more than 39dB. In case of no blocker the circuit is set to amplifier mode providing 17dB of voltage gain, 8.4dB noise figure and IIP3 of 6.6dBm while consuming 3mW. Application areas are coexistence in multi-radio devices and dealing with TX leakage in FDD systems

Measuring RF circuits exhibiting nonlinear responses combined with short and long term memory effects

All RF circuits that incorporate active devices exhibit nonlinear behavior. Nonlinearities result in signal distortion, and therefore state the upper limit of the dynamic range of the circuits. A measure for linearity used quite commonly in RF is the P1dB and/or IP3 point. These quantities are usually measured using a signal generator and a spectrum analyzer. Depending on the quantity of interest (1 P1dB or IP3), a single or two-tone signal is passed through the system. A shortcoming of this type of measurement is that it only quantifies the magnitude of the distortion, and gives no information about the phase. New measurement methodologies using X-parameters circumvent this shortcoming by including phase information as well. This enables more detailed nonlinear measurements, providing the RF designer with more information leading to a higher predictability of the total RF system. For many RF applications this methodology provides sufficient information. In real-life RF systems, the distortion components (harmonics and intermodulation products) can in principle have any phase due to memory effects. The memory effects can sub-divided into two categories, namely short and long term effects. Short term memory exhibits time constants smaller than the symbol time of the modulated signals of interest, and long term memory has time constants which are spread over multiple symbols. The aforementioned X-parameters include only short term memory effects, leading to a certain phase of the distortion products. This limitation of the approach based on X-parameters is due to the fact that only unmodulated constant envelope signals are used (pure sinusoidal signals) as an excitation. In this paper a measurement setup is proposed that captures both the input and output signals, fully in the time domain. Realistic (and in fact any arbitrary) waveforms can be used as excitation, enabling the extraction of both the short and the long term memory effects that are of increasing importance for future wireless systems with complex wideband modulation techniques. To achieve a high accuracy, a noise minimization technique is applied

Antenna coupling reduction between co-located radios

No abstract