A.H. Aghvami

A Novel Wideband MMIC Active Balun

A new technique for realising active baluns has been demonstrated in MMIC form. The circuit uses distributed matching techniques and is capable of covering an extremely wide frequency range. An MMIC prototype has been designed and tested, and balun operation over 1 to 12 GHz has been achieved. This paper describes the circuit operation, design and measured results.

A Novel 1 to 14 GHz Monolithic Matrix Distributed FET Mixer

The concept of the matrix distributed amplifier has been extended to the distributed mixer, giving an exceptionally convenient method of isolating the RF, LO, and IF signals. The matrix distributed mixer incorporates RF amplification, mixing, and IF amplification, in a series of tiers of gate and drain-lnes. A monolithic matrix distributed mixer has been realised, and its design and performance is described. This first matrix distributed mixer chip has achieved 1dB conversion gain over 1 to 15 GHz, with only two sections and no IF amplification.

S-Band Monolithic Active Filter using Actively-Coupled Resonator Technique

A highly-selective bandpass active filter design technique is presented which uses a monolithic actively-coupled resonator cell combined with additional transmission zeros implemented with off-chip microstrip line resonators. The technique gives the advantages of light-weight and small-size, inherent in active filters, but achieves greatly improved selectivity and high tolerance to GaAs process variations. A prototype filter consisting of one MMIC actively coupled resonator chip has been designed and tested. The filter operates at 3 GHz, with a 3-dB bandwidth of 200 MHz and 10dB of gain. 40dB of rejection is achieved at 400 Mhz from the center frequency. The gain can be controlled by the bias voltage, while the Q factor and the center frequency remain unaffected by these changes.

A novel reflectometer using a wideband monolithic active unilateral 4-port junction

The concept of using an active unilateral circuit to separate incident and reflected signals for the measurement of reflection coefficient has been demonstrated. The monolithic active unilateral circuit uses distributed amplification techniques, and operates over 1 to 20 GHz. The circuit can be used to replace conventional directional couplers and bridges in a wideband reflectometer, and this has been successfully achieved with good performance over the 1 to 10 GHz range. The circuit has been integrated with an HP8410 network analyser using full errorcorrection. The active technique has the advantage of very small size and is intended for fully active wafer probe heads. The technique promises extremely wide bandwidth and high directivity

Ku-band serrodyne frequency translator using wideband MMIC analogue phase shifters

A novel Ku-band serrodyne frequency translator is presented which employs wideband MMIC analogue phase shifters. The MMICs have a simple topology and are fabricated using low cost foundry processing techniques. The resulting highly nonlinear tuning behaviour of the complete 360° phase shifter is overcome with two different types of modulating signal: the first having a predistorted sawtooth function (using DSP techniques) and the second having a linear sawtooth function (resulting in 20% under-modulation). With an input carrier frequency of 14GHz, the measured results demonstrate high levels of carrier suppression and unwanted sideband suppression, with both functions. This performance was maintained at all carrier frequencies in the 13 to 15GHz frequency range - without having to modify the functions. In addition, 0dB conversion loss was achieved and almost no control power was required.

Microstrip Quadruplexer using -3 dB Hybrids

A periodic branching microstrip filter using -3 dB directional couplers and short lengths of microstriplines with improved frequency characteristics is described in this paper. The designed filter separates the 2-18 GHz input signal into four 4 GHz contiguous channels. The design of the periodic branching filter and experimental results are presented.

Monolithic Analogue Phase Shifter and Cascode FET Amplifier using Uniplanar Techniques

A precision millimetre-wave analogue phase shifter and a miniature Ku-band cascode FET amplifier are presented. Both MMICs are realised using uniplanar technology. The phase shifter employs a blend of coplanar waveguide and multilayer techniques. It has a worst-case rms phase error of only ± 1.0°, for all levels of relative phase shift up to 120°, across the 31 to 32 GHz frequency range. The amplifier is realised using a combination of coplanar waveguide, meandered thin-film microstrip, and lumped elements. The amplifier has an active area of only 0.9 mm2 and a measured gain of over 12 dB at 15 GHz.