Ali Zahabi

Study on integrated transmission line ΣΔ modulators

The feasibility and design guidelines for implementing integrated transmission-line based Sigma Delta modulators (ITLSDMs) have been studied. By a systematic design methodology for wireless frequency standards, the practical issues of realizing ITLSDMs such as different semiconductor technologies, performance, area and power consumption have been addressed. Having compared the different technologies and types of transmission lines (TLs), a typical 4th order bandpass SDM (BPSDM) as well as a 2nd order lowpass one (LPSDM) for a sampling frequency (fs) of 10GHz and a bandwidth (BW) of 78MHz have been simulated behaviorally to obtain the minimum circuit requirements for each architecture. An area estimation approach and an optimum realization method are finally proposed which lead to reduced chip area while keeping the performance constant.

3.1GHz–3.8GHz integrated transmission line super-regeneration amplifier with degenerative quenching technique for impulse-FM-UWB transceiver

This paper presents an integrated transmission line super-regeneration amplifier (SRA) with degenerative quenching technique for short range impulse-FM-UWB transceiver. In transmitting mode, the SRA generates pulsed-sinusoids centered at two different tuned frequencies within 3.1GHz–3.8GHz to distinguish between data bit ‘1’ and ‘0’. In receiving mode, the SRA switches between filtering and oscillating modes with periodic change in the resonant frequency to detect the impulse-FM-UWB data pattern. The Q-enhanced degenerative quenching technique reduces the sensitivity of the negative transconductance (GM) over a wide range of bias currents. This also reduces the direct coupling of the high frequency quenching pattern to the resonator and the negative GM stage. The capacitively loaded integrated transmission line reduces the phase noise in transmit and receive modes. A test structure of the amplifier has been implemented in 0.25um BiCMOS technology. The SRA consumes 1.2mA and 1.8mA from a 2.5V supply in transmit and receive mode for a data rate of 10Mb/s and a sensitivity of −90dBm.

Inductively coupled super-regeneration amplifier based on integrated transmission line for transcutaneous data transfer

An inductively coupled super-regeneration amplifier (SRA) is presented for near field transcutaneous data transfer. Capacitively-loaded integrated transmission line based resonators are used to build inductively coupled telemetry link. In transmitting mode, the SRA generates digitally controlled on-off keying (OOK) modulated pulsed-sinusoids tuned at 2.4GHz. In receiving mode, the SRA switches in between filtering and oscillation modes in order to detect the inductively coupled data pattern. The degenerative quenching technique is employed in the SRA to improve the linearity, and to reduce the sensitivity of the negative transconductance (GM) over a wide range of bias current. The SRA consumes 1mA from 2.5V supply in a 250nm BiCMOS technology and achieved a data rate of 100Mb/s in transmit mode. In receiving mode, the SRA consumes 1.2mA from 2.5V supply to detect −75dBm signals at data rate of 10Mb/s.

2.4GHz super-regeneration amplifier with degenerative quenching technique for RF-pulse width transceiver

This paper presents a 2.4GHz super-regeneration amplifier with capacitively-loaded integrated transmission line for a short range RF-pulse width transceiver. The degenerative quenching technique is employed in the super-regenerative amplifier to improve the linearity and reduces the sensitivity of negative transconductance (GM) to the bias current. It also reduces the direct coupling of the high frequency quenching pattern to the resonator and the negative GM stage. The capacitively-loaded integrated transmission line reduces the phase noise in transmit and receive modes. A test structure of the amplifier has been implemented in 0.25um BiCMOS technology. The amplifier consumes 1.2mA and 1.5mA from 2.5V supply in transmit and receive mode for a data rate of 20Mb/s and a sensitivity of -95dBm.

Digitally-switched resonators for bandpass integrated transmission line ΣΔ modulators

A digital tuning approach for adjusting the frequency of a resonator in a bandpass integrated transmission-line based SDM (BP-ITLSDM) is presented. The resonators are tuned by switching the length of an integrated transmission line (ITL) instead of the conventional varactor tuning. It makes the compensation process for the finite gain bandwidth (GBW) of transconductances independent from the tuning process of the resonator. Additionally, the same resonator gain is achieved at different tuned frequencies. To reduce the effect of parasitics and digital control patterns, common mode signal switching (CMS) is employed. The simulations are performed for a 2.5GHz resonator using a 16-segmented switchable ITL with unit length of 430um. A frequency tuning range of 1.5GHz and a finite GBW compensating range up to half of the sampling rate 10GHz is achieved in a 0.25um BiCMOS SiGe technology.

A power/area-starved complementary-cross-coupled filter for integrated transmission line ΣΔ modulators

In this paper, an approach for decreasing the area and power consumption of an integrated transmission line sigma delta modulator (ITLSDM) is presented. The architecture is based on complementary-cross-coupled bandpass filter (C-BPF) with an auxiliary negative transconductance (ANG). A closed form formula is derived to specify the characteristics compared to a SDM based on NPN cross-coupled bandpass filters (N-BPFs). The matching requirements for the loop transmission lines are relaxed by using C-BPFs. The simulation results for a 4th order BP-ITLSDM realized in a 0.25um BiCMOS technology show a reduction of 53% in the current consumption and 46% in the die area of a resonator compared to the N-BPF method. The improvement factor is more obvious for higher order BPSDMs.

Near field inductive coupled tuning technique for RF bandpass ΣΔ modulators

A simple and fast wireless technique for accurate tuning of the resonators in high speed bandpass sigma delta modulators (BPSDMs) is presented. A commercially available antenna is employed to detect the radiation of on-chip resonators in the oscillation mode. The antenna is used for the calibration of the resonators at first. After adjusting the tuned frequency of resonators, it is reused as the front-end part of an RF receiver. The proposed architecture accelerates and simplifies the tuning process. Moreover, an extra oscilloscope for storing and post processing of demultiplexed data, which is typically used in GHz applications, is not required. Distinguishing between multi signal tones and disturbing tones in the spectrum is easier compared to conventional approaches.

Integrated transmission lines for complementary cross-coupled bandpass filters in ΣΔ modulators

In this paper, the properties of various types of transmission lines (TLs) intended for an integrated RF TL based sigma delta modulator (ITLSDM) are extracted. The EM simulator is used to achieve accurate models for TLs in a 180nm CMOS technology. The effects of TL parameters are compared and studied in order to achieve the guidelines, which save the area and power consumption of the modulator. The results are verified with an architecture, which is based on complementary cross-coupled bandpass filter (C-BPF) with an auxiliary negative transconductance (ANG). This filter is employed in a 9.6GHz 4th order fs/4 bandpass SDM tuned at a center frequency of 2.4GHz.

A 9.6 GS/s 112 mW 58 dB DR 150 MHz bandwidth RF bandpass transmission line ΣΔ modulator

A 4th order RF bandpass sigma delta modulator (BPSDM) centered at 2.4GHz ISM band based on integrated transmission lines (ITLs) is presented for the first time. The modulator consists of two tunable capacitively-loaded transmission line resonators with active Q-enhancement. As a result, the design of noise transfer function (NTF) is simplified and the degradation in performance due to the jitter noise and excess loop delay (ELD) are reduced. An analytical procedure is presented, which ends up to the TL length reduction without affecting the low jitter sensitivity. The modulator is implemented in a 250nm SiGe BiCMOS technology and occupies an active area of 1.26mm2. The 1-bit modulator output achieves a dynamic range (DR) of 61dB/58dB in a bandwidth (BW) of 75MHz/150MHz, a signal-to-(noise+distortion) ratio (SNDR) of 35dB at 150 MHz BW and consumes 112mW from a 2.5V supply. In the presence of σjitter=1.3psrms, the measured performance is not limited by clock jitter unlike to conventional LC modulators. Moreover, more ELD (~0.7Ts) compared to conventional LC modulators (~0.55Ts) is tolerated, which proves the robustness of the designed ITLSDM. For the prototype, an efficient wireless technique for tuning of the resonators employing a commercial wideband antenna has been used.