RF Channel Selection Research Articles

Tunable optical-microwave filters optimized for 100 MHz resolution.

New continuously tunable RF-spectrum analyzers, RF receivers, and RF signal generators are proposed and analyzed for the silicon-on-insulator integrated-photonic platform at the ~1550 nm wavelength. These RF system-on-a-chip applications are enabled by a new narrowband 2x2 Mach-Zehnder interferometer (MZI) tuned filters for reconfigurable multiplexing, demultiplexing and RF channel selection. The filter can be optimized for ~100 MHz 3-dB bandwidth (BW) by utilizing N closely coupled Bragg-grating resonators to form one effective waveguide resonator in the single-mode silicon nanowire used for each MZI arm. The number of periods M within each individual resonator is selected to engineer BW in the 0.1 to 1 GHz range. Butterworth design is employed. Continuous tuning of the 100 MHz-BW devices over 18.6 GHz has been simulated by using local micron-scale thermo-optical heater stripes on the MZI arms with a temperature rise from 0 to 48K. For the case of N = 3 and 100-nm silicon side teeth, some representative performance predictions are: insertion loss (IL) = -10.7 dB, BW = 80.5 MHz and L = 113 μm for M = 58; while IL = -0.74 dB, BW = 1210 MHz and L = 86 μm for M = 44.

A Low-Power Interference-Tolerance Wideband Receiver for 802.11af/ah Long-Range Wi-Fi With Post-LNA Active <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math> </inline-formula>-Path Filter

A low-power interference-tolerance wideband receiver with post-LNA active N-path filter for RF channel selection is proposed for 802.1af/ah long-range Wi-Fi standards. By leveraging gain, noise, and filtering characteristics among the wideband LNA, high-Q active N-path filter, and reconfigurable analog baseband circuits, the proposed receiver achieves high gain, low noise, and high linearity with low power dissipation. The receiver provides narrow-bandwidth RF filtering with a small chip area. Implemented in a 40-nm CMOS process with the chip size of 1.1 mm $\times2.25$ mm, the full receiver shows a conversion gain of 84 ± 1 dB and achieves noise figure from 3.4 to 3.9 dB in subgigahertz frequency bands. The measured in-band IIP3, out-of-band IIP3, and out-of-band IIP2 are −5.9, −0.5, and +62.5 dBm, respectively. The proposed receiver dissipates an average power of 41 mW.

5/60 GHz $0.18~\mu m$ CMOS Dual-Mode Dual- Conversion Receiver Using a Tunable Active Filter for 5-GHz Channel Selection

A dual-mode dual-conversion receiver with two far-apart carrier frequencies, 5 and 60 GHz, and two very different channel bandwidths, tens-MHz and GHz, is demonstrated in a standard $0.18~\mu \text {m}$ CMOS technology. The dual conversion architecture receives 60-GHz mode using Schottky diodes at the first conversion stage and merges 5-GHz mode at the second conversion stage. The 5-GHz RF channel selection is achieved by inserting a 20-MHz bandwidth tunable active filter after a 5-GHz low-noise amplifier for the noise concern and before the second down-conversion mixer to relax the linearity requirement of subsequent stages. A tunable active filter with improved linearity using a transformer-coupled scheme is employed. As a result, the narrow 20 MHz channel bandwidth selection at 5-GHz mode shows a 500 MHz tuning range with noise figure of 9 dB and conversion gain of 28 dB. For 60-GHz operation, the 3-dB IF bandwidth is 1 GHz with noise figure of about 20 dB and conversion gain of −3 dB.

Linearly Polarized Microstrip Planar Filtenna for X and Ku Band Communication Systems

Objective: Design and analysis of a Planar filtenna to operate in X and Ku band communication systems. Methods/Analysis: The design of the filter consisting of planar metallic structure on the top side and a defected ground type structure on another side of the substrate. A substrate material is integrated with vias at the bottom part of the designed structure. The simulation results of the designed filtenna are carried with commercial electromagnetic tool HFSS and all the filtenna radiation characteristics are presented in this work. Findings: A substrate integrated waveguide filter is used in this model for RF channel selection as well as a balun. The proposed filtenna occupies a compact dimension of 12x35.5x1.6 mm. Novelty/Improvement: Planar structures with substrate integrated vias are acting as electromagnetic band gap structures in the current design. The surface wave related losses will be suppressed with this novel structure. Microstrip line feeding with 50 ohm impedance and easy integration are making this model suitable for multiband communication applications.

MEMS-based RF channel selection for true software-defined cognitive radio and low-power sensor communications

An evaluation of the potential for MEMS technologies to realize the RF front-end frequency gating spectrum analyzer function needed by true software-defined cognitive radios and ultra-low-power autonomous sensor network radios is presented. Here, RF channel selection, as opposed to band selection that removes all interferers, even those in band, and passes only the desired channel, is key to substantial potential increases in call volume with simultaneous reductions in power consumption. The relevant MEMS technologies most conducive to RF channel- selecting front-ends include vibrating micromechanical resonators that exhibit record on-chip Qs at gigahertz frequencies; resonant switches that provide extremely efficient switched-mode power gain for both transmit and receive paths; medium-scale integrated micromechanical circuits that implement on/off switchable filter-amplifier banks; and fabrication technologies that integrate MEMS together with foundry CMOS transistors in a fully monolithic low-capacitance single-chip process. The many issues that make realization of RF channel selection a truly challenging proposition include resonator drift stability, mechanical circuit complexity, repeatability and fabrication tolerances, and the need for resonators at gigahertz frequencies with simultaneous high Ω (>30,000) and low impedance (e.g., 50 W for conventional systems). Some perspective on which resonator technologies might best achieve these simultaneous attributes is provided.

Active Feedback Technique for RF Channel Selection in Front-End Receivers

Co-existence problems in a mobile terminal environment pose strict requirements on the linearity of a front-end receiver. In this paper, active feedback is explored as a means to relax such requirements by providing channel selectivity as early as possible in the receiver chain. The proposed receiver architecture addresses some of the most common problems of integrated RF filters, while maintaining their inherent tunability. Through a simplified and intuitive analysis, the operation of the receiver is examined and the design parameters affecting the filter characteristics, such as bandwidth and stopband rejection, are determined. A systematic procedure for analyzing the linearity of the receiver reveals the possibility of LNA distortion canceling, which decouples the trade-off between noise, linearity and harmonic radiation. A prototype designed in a standard 65 nm CMOS process occupies ; +12 dBm.

Ku-Band Linearly Polarized Omnidirectional Planar Filtenna

A linearly polarized omnidirectional planar filtenna at Ku-band is presented in this letter. It is a seamless and incorporate design of an inductive window bandpass filter and a planar coaxial collinear (COCO) radiation element. The radiation element has a linearly polarized omnidirectional radiation characteristic. The substrate integrated waveguide filter is used for RF channel selection as well as a balun. The proposed filtenna has merits of light weight, compact size, low cost, and easy integration with other planar circuits. Simulation and measurement results show that the radiation characteristics of the filtenna keep nearly no change within the working band, while unwanted signals at out-band can be effectively filtered.

A broadband RF 65 nm CMOS front-end for cable TV reception

A novel broadband RF front-end in 65nm CMOS technology is presented. The front-end serves to precondition the incoming RF spectrum for further processing in a cable TV receiver architecture where RF channel selection and down conversion are done in digital domain. The analog front-end consists of a broadband highly linear low-noise amplifier followed by a variable gain RF amplifier. An original broadband circuit topology for the amplifiers is adopted.The fabricated front-end exhibits a bandwidth of 50–1050MHz, a variable gain, which spans from 12 to 37dB with a 0.2dB step, an OIP3 of 28.4dBm (77.5dBmV), an OIP2 of 65dBm (114dBmV), and a noise figure of 5.8dB, dissipating 125mW at 1.2V supply, and a core silicon area of 0.4mm2.