Engineering Commons^™

Wideband Voltage Variable Attenuator With Fewer Components, Chin-Leong Lim

Chin-Leong Lim

RF/microwave amplifying devices have unit-to-unit gain variability. So, in some critical applications such as the low noise amplifier (LNA) in cellular basestations, the gain has to be adjusted in production using a voltage-variable attenuators (VVA). Constant impedance VVAs such as the PI and the bridged-TEE topologies require between 14 to 18 components, including 2 to 4 active devices, but their large dynamic (attenuation) range is wasted in this amplifier gain adjustment application. To create a more economical and smaller VVA for amplifier gain adjustment, we investigated a new circuit configuration comprising one active and four passive components. This paper describes …

Vva Extends Bw And Dynamic Range, Chin-Leong Lim

Chin-Leong Lim

Voltage-variable attenuators (VVAs) enable gain adjustment in a wide range of applications, including in cable-television (CATV), satellite-television (SATV) systems, and even test equipment and measurement systems. The PI VVA configuration using PIN diodes is ubiquitous in CATV and SATV systems owing to its low part count, small size, constant impedance, high linearity, and multi-decade bandwidth. Presently, this class of VVAs have been under severe miniaturization pressure in order to shrink end-product size. To create the industry's smallest CATV/SATV-suitable VVA, we integrated all necessary components into a multi-chip-on-board (MCOB) package measuring 3.8 x 3.8 x 1.0 mm (14 mm square footprint). …

Lna Lowers Noise, Raises Oip3 At 3.5 Ghz, Chin-Leong Lim

Chin-Leong Lim

A 3.5 GHz LNA with good noise figure, gain and linearity performances has been designed around a low-cost, QFN2x2-packaged monolithic integrated circuit (MMIC). Incorporation of bias regulator, ESD protection and stability network at chip-level reduces the external component count to 12. The proprietary 0.25 um EPHEMT process achieves +15-dB gain in single stage and less than 1 dB noise figure at 3.5 GHz.

Automating The Screening Of Microphonic Defects In Automotive Radio Receivers, Chin-Leong Lim

Chin-Leong Lim

Microphonics are unwanted electro-acoustic effects in electronic equipment caused by mechanical vibration. Vehicular radio receivers are particularly susceptible due to their traveling over uneven roads, e.g. potholes and bumps. As microphonics influence customers’ perception of product quality, manufacturers actively seek to sieve out receivers exhibiting the worst manifestation of this defect. The IEC 315-4 standard for FM broadcast receivers mandates screening for "unwanted acoustic feedback" by tapping on the receiver housing and then listening for the tell-tale ringing noises at the audio output, i.e. speakers or headphone. However, this subjective method requires trained workers and even then, the repeatability can …

Setting New Noise Performance Benchmarks Using Wideband Low-Noise High-Linearity Lnas, Chin-Leong Lim

Chin-Leong Lim

Objective: to design a 900 MHz Low-Noise Amplifier (LNA) using a MMIC fabricated on a new ultra low noise GaAs ePHEMT process. To demonstrate a new noise performance bench mark (F = 0.3 dB at IRL ≤ - 15 dB) for the plastic-packaged device class.

Material: The LNA consists of a Microwave Monolithic Integrated Circuit (MMIC) and 9 passive components mounted on a 21.5x18 mm2 Rogers RO4350 micro-strip PCB. The MMIC, which comprises a common-source amplifier and temperature-tracking active bias, is fabricated on a new GaAs ePHEMT process optimized for noise. As loss in the input matching network is proportional …