Rasmus Schandorph Michaelsen

A Modified Marchand Balun Configuration With Tunable Phase Balance

In this letter, a novel modified Marchand balun configuration with tunable phase balance is analyzed and verified experimentally. It is proposed to add a shunt susceptance in between the two couplers of the Marchand balun. This allows for a change in the phase balance which, to first order, is linear with the susceptance, while the magnitude balance is kept constant. To verify the proposed configuration, a lumped element Marchand balun has been fabricated using a SiGe BiCMOS technology. The balun design is centered around 9.4 GHz, with an insertion loss of 6.0 dB. The phase difference between the output ports can be changed from 175.8° to 183 ° whereas the magnitude imbalance is kept almost constant at 0.3 dB. The balun performs well in the range from 7 to 11 GHz, where it is possible to tune the phase to exactly 180°.

Analysis and design of complex impedance transforming marchand baluns

A new type of Marchand balun is presented in this paper, which has the property of complex impedance transformation. To allow the Marchand balun to transform between arbitrary complex impedances, three reactances should be added to the circuit. A detailed analysis of the circuit gives the governing equations. To verify the theory, a design and electromagnetic simulation of a lumped element Marchand balun is made in a SiGe BiCMOS technology. The lumped element impementation is favorable because capacitors are placed where the additional reactances should be added. Thus it is possible to absorb a positive reactance by reducing a capacitor. At the design frequency of 10.5 GHz it matches 50Ω to 50 - j66Ω. It has an insertion loss of 5.1 dB, an input reflection of -20.8 dB, as well as phase and magnitude imbalance better than 0.2° and 0.12 dB, respectively.

A SiGe BiCMOS double-balanced mixer with active balun for X-band Doppler radar

In this paper, we present an X-band double-balanced mixer in SiGe BiCMOS technology. The mixer core consists of a LO Matched quad diode ring using diode-connected Heterojunction Bipolar Transistors (HBTs). The mixer is integrated with a low-noise, high-linearity active balun on the RF port and a miniaturized Marchand balun on the LO port. Experimental results shows a conversion gain of +4 dB at 10.5 GHz with an LO drive level of 15 dBm. The LO-IF and RF-IF isolation is better than 36 dB and 26 dB, respectively, in the entire band of operation. The input referred 1 dB compression point is better than -11 dBm. The IIP2 is +13 dBm at a supply voltage of 3 V and +16.5 dBm at a supply voltage of 6 V. The measured noise figure is found to be ~6.5 dB at 10.5 GHz.

Physical based Schottky barrier diode modeling for THz applications

In this work, a physical Schottky barrier diode model is presented. The model is based on physical parameters such as anode area, Ohmic contact area, doping profile from epitaxial (EPI) and substrate (SUB) layers, layer thicknesses, barrier height, specific contact resistance, and device temperature. The effects of barrier height lowering, nonlinear resistance from the EPI layer, and hot electron noise are all included for accurate characterization of the Schottky diode. To verify the diode model, measured I-V and C-V characteristics are compared with the simulation results. Due to the lack of measurement data for noise behaviors, simulated noise temperature is compared with the experimental data found from the open literature.

Flicker noise comparison of direct conversion mixers using Schottky and HBT dioderings in SiGe:C BiCMOS technology

In this paper, we present flicker noise measurements of two X-band direct conversion mixers implemented in a SiGe:C BiCMOS technology. Both mixers use a ring structure with either Schottky diodes or diode-connected HBTs for double balanced operation. The mixers are packaged in a metal casing on an Arlon 25N substrate to shield the sensitive noise measurement. Conversion loss measurements of both mixers is performed both for on-wafer and packaged versions. The experimental results shows that the Schottky diode mixer exhibits a 1/f noise corner frequency of 250 kHz, while the diode connected HBT circuit demonstrates a 1/f noise corner frequency around 10 kHz.

Design of a SiGe BiCMOS canceller for low frequency noise reduction in direct conversion receivers

Direct-conversion receivers are increasingly employed in many applications, such as wireless communications and radars. Indeed, they represent an effective alternative to heterodyne receivers, as they allow a higher level of integration. However, performance limitations are imposed by the leakage of the local oscillator (LO) toward the RF port of the mixer (Figure 1(a)). This causes the LO self-mixing phenomenon, which is responsible of a significant DC offset at the output of the receiver (Figure 1(b)). In turn, this DC offset gives rise to a high level of low frequency noise affecting the signal recovery at baseband (R. S. Michaelsen et al., IEEE Microwave and Wireless Components Letters, Vol. 23 No. 2, 2013, pp. 66–68).

X-band active balun MMIC in SiGe technology

Baluns are used to transform an unbalanced input signal into a balanced output signal. Baluns are essential components in many microwave circuits, e.g., balanced mixers, or other differential architectures. When the signal is received by the antenna, it is single ended, and thus need to be converted to a balanced signal to benefit from a differential system architecture. Being first in the receiver chain, having a passive balun, will degrade the noise figure significant, thus it is beneficial to have low noise amplifier, which behaves as a balun. For the receiver to have a large dynamic range this balun must also have good linearity, and a high compression point (D. Manstretta, IEEE JOURNAL OF SOLID-STATE CIRCUITS, 47, 2012, pp. 407–420).

Design of a ×4 subharmonic sub-millimeter wave diode mixer, based on an analytic expression for small-signal conversion admittance parameters

Instead of using frequency multipliers before a fundamental mixer, subharmonic mixers can be used. In order to develop novel subharmonic mixer architectures it is necessary to know the exact signal phase at the nonlinear element. The purpose of this paper is to generalize the description of the small-signal admittance in a Schottky-diode mixer where the phase can be set arbitrarily. It is shown that only for the case of a fundamental frequency mixer this admittance becomes a purely real valued conductance. To test the theory a ×4 subharmonic sub-millimeter wave mixer is designed and simulated. With an RF frequency of 640 GHz, this design achieves a conversion gain of -13.5 dB with a LO-power of only -2.5 dBm.