In-band Group Delay Variation Research Articles

RF Multi-Functional Input-Reflectionless Dispersive-Delay Structure With Sharp-Rejection Filtering Using Channelization Techniques

A class of RF multi-functional input-reflectionless dispersive-delay structure (DDS) with linear-type in-band group-delay variation and sharp-rejection bandpass-filtering capability is reported. It exploits a two-branch-channelized/balanced-type circuit with similar low-order reflective DDS units inside its channels, which are connected through input/output 3-dB quadrature wideband couplers. The adopted DDS unit is based on a coupled-resonator network with a frequency-dependent cross-coupling. It introduces a pair of complex transmission zeros (TZs) to shape the intended in-band group-delay profile. Unequal transmission-line-based phase-shifting sections are also inserted at the outputs of both channels. In this manner, an input-absorptive behavior and selectivity enhancement with TZ generation are attained by means of transversal signal-interference techniques at the overall input and output nodes, respectively. Moreover, as the transfer-function phase term of the interference action in transmission is linear with frequency, the total group-delay pattern is defined by the DDS unit of the channels. As practical validation, a 1.5-GHz proof-of-concept microstrip prototype is constructed and tested.

A 120 MHz fast automatic tuning CMOS active-RC lowpass filter

In this paper, a fast automatic cutoff frequency calibrating, CMOS lowpass filter with linear-in-dB tunable gain and constant in-band group delay is presented. The automatic frequency tuning (AFT) circuit can successfully tune the cutoff frequency to 120 MHz with less than 4.7% error. In-band group delay variation is handled using a capacitor process variation detection circuit (CPVD), and the overall tuning time is less than 700 ns. The design is done using STM PD-SOI 130 nm CMOS process, and the supply voltage is 1.2 V with a total power consumption of 21.7 mW. The overall filter provides a programmable linear-in-dB gain of 0.5 dB to 17.6 dB range with a cutoff tuning range of 80 to 180 MHz. The in-band group delay variation is below 500 ps with an adjacent channel ratio (ACR) of 85 dB. The spurious free dynamic range (SFDR) is over 66.6 dBc. The active area of the filter with tuning is 0.171 mm2.

Widely bandwidth-tunable silicon filter with an unlimited free-spectral range.

Next-generation high-capacity optical networks require flexible allocation of spectrum resources, for which low-cost optical filters with an ultra-wide bandwidth tunability beyond 100 GHz are desired. We demonstrate an integrated band-pass filter with the bandwidth continuously tuned across 670 GHz (117-788 GHz) which, to the best of our knowledge, is the widest tuning span ever demonstrated on a silicon chip. The filter also features simultaneous wavelength tuning and an unlimited free spectral range. We measured an out-of-band contrast of up to 55 dB, low in-band ripples of less than 0.3 dB, and in-band group delay variation of less than 8 ps. This result was achieved using cascaded Bragg-grating-assisted contra-directional couplers and micro-heaters on the 220 nm silicon-on-insulator platform with a very compact footprint of less than 7000 μm2. Another design with the bandwidth continuously tunable from 50 GHz to 1 THz is also presented.

A 4 GHz 60 dB Variable Gain Amplifier With Tunable DC Offset Cancellation in 65 nm CMOS

This letter presents a compact CMOS based variable gain amplifier with 60 dB gain control range and a feedback reconfigurable dc offset cancellation. The design is a four-stage fully differential cascaded amplifier implemented using a 65 nm CMOS process. The amplifier achieves a current controllable gain range from ${-}39.4$ dB to ${+}20.2$ dB, a voltage tunable lower cutoff frequency from dc to 200 kHz, a consistent 3 dB bandwidth better than 4 GHz, a maximum dc power consumption of 26 mW, a measured in-band group delay variation of 20 ps, and a noise figure from 10 to 27 dB. The proposed VGA design occupies a compact die area of only 75 $\mu$ m $\,\times\,$ 80 $\mu$ m (excluding pads for measurement).

A 35-mW 30-dB Gain Control Range Current Mode Linear-in-Decibel Programmable Gain Amplifier With Bandwidth Enhancement

This paper presents the design of a programmable gain amplifier (PGA) that serves as an interface between the receiver front-end and the baseband processor. The proposed PGA design is fabricated in a commercial 0.18- μm SiGe BiCMOS process with a topology consisting of two digitally variable gain amplifiers cascaded by a post amplifier and interconnected by differential wideband matching networks that presents an overall enhanced gain bandwidth product. By using the current mode exponential gain control technique, the proposed design achieves a broad 30-dB linear-in-decibel gain range, a gain-independent output 1-dB compression point better than -10 dBm, input/output return loss better than 13 dB, a ±0.75-dB gain flatness over a multi-decade frequency range from 2.5 MHz to 1.17 GHz, a measured in-band group-delay variation of 30 ps, a 35-mW power consumption, and a 0.25- mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> core die area.

Self-equalised pseudo-elliptical filter made of substrate integrated waveguide

A self-equalised pseudo-elliptical filter on the basis of substrate integrated waveguide technology is proposed and demonstrated over the Ka-band range. The extracted-pole technique is used to synthesise a sixth-order filter with non-resonating nodes. Measured results of the filter exhibit a high selectivity and a minimum in-band insertion loss of about 2.0 dB and small inband group delay variation.

Effect of Group Delay in RF BPF on Impulse Radio Systems

This paper presents an analysis of the effects of RF filter characteristics on the system performance of an impulse radio. The impulse radio system transmits modulated pulses having very short time duration. Information can be extracted in the receiver side based on the cross-correlation between received and reference pulses. Accordingly, the pulse distortion due to in-band group delay variation can cause serious degradation in system performance. In general, RF band pass filters inevitably cause non-uniform group delays to the signal passing through the filter that are proportional to its skirt characteristic due to its resonance phenomenon. In this work, a small signal scattering parameter, S 21 , which is a frequency domain parameter, and its Fourier transform are utilized to characterize the output pulse waveform under the condition that the input and output ports are matched. The output pulse waveform of the filter is predicted based on the convolution integral between the input pulse and filter transfer function, and the analysis result is compared with previously reported experimental result. The resulting bit error rate performances in a bi-phase modulation and a pulse position modulation based impulse radio system are also calculated. Moreover, improvement of system performance by the pulse shaping method, a potential solution for pulse waveform distortion, is analyzed.

An 11-Band 3–10 GHz Receiver in SiGe BiCMOS for Multiband OFDM UWB Communication

This work presents a receiver implementation for MB-OFDM UWB communication that enables 11 bands of operation covering 78% of the spectrum licensed by the FCC. First, important system-level considerations are discussed with basis on the specifications from the MB-OFDM standard. Next, the different circuit techniques employed in the implementation of the receiver are described. For the LNA design, a wideband impedance match network that takes into account the package components is introduced. A notch filter embedded in the LNA and its tuning mechanism are proposed to attenuate the interference from devices operating in the U-NII band from 5.15 to 5.35GHz. Based on the results of a recent investigation on frequency planning for MB-OFDM radios, a compact 11-band fast-hopping synthesizer implementation is proposed for the receiver. The 264-MHz baseband section consists of a linear phase low pass filter and a programmable gain amplifier; it presents an in-band group delay variation of less than 0.6 ns and 42 dB of gain in steps of 2 dB. The IC is fabricated in a 0.25-mum SiGe BiCMOS process, placed in a QFN package and mounted on FR-4 substrate for its characterization. Measurement results show a receiver gain of 78-67 dB and NF of 5-10 dB across the 11 bands from 3-10 GHz, while consuming 114 mA from a 2.5-V supply

A low-distortion BiCMOS seventh-order Bessel filter operating at 2.5 V supply

This paper presents the design of a seventh-order continuous-time Bessel filter using a new low-voltage and highly linear BiCMOS transconductor. A high-gain and parasitic-insensitive integrator is obtained by using an active capacitor scheme. The filter has been designed to operate at a 2.5 V supply with a nominal -3 dB cutoff frequency of 600 kHz. It has been fabricated in 1 /spl mu/m, double-poly 6-GHz BiCMOS process. The inband group delay variation is less than 10 ns. The total harmonic distortion (THD) measured with a 100 kHz input signal is less than -49 dB for a 2 V/sub pp/ amplitude and the dynamic range is 77 dB. The filter can be frequency tuned over almost one decade with a gain variation less than 0.2 dB in the passband. A common-mode rejection ratio (CMRR) of 53 dB in the passband is observed, thanks to a careful common-mode control strategy.