In this paper, the patch concept is applied to the design of millimeter-wave band-pass filters in BiCMOS 55 nm technology. The operation frequencies are 120 GHz and 200 GHz, respectively. A via- and slot-based approach makes filters very compact, albeit patch-based, through a multi-mode approach. At 200 GHz, the side of the patch is only 194 μm long, or about a quarter wavelength, compared to half a wavelength for a conventional patch. The dependence of performance on the thickness of the Back-End-Of-Line is studied, and the design method is detailed. The performance is very good, with for example a filter operating at 200 GHz with a relative bandwidth of 23% and insertion loss of 3 dB. Finally, the prospect of using a thicker Back-End-Of-Line, offered as an option in 55-nm BiCMOS technology, makes it possible to show that even better performance can be achieved, with insertion loss below 3 dB.

In this paper, a 2-bit digital reflection-type phase shifter working at 120 GHz is presented. It uses a compact coupled-lines coupler with low insertion loss and high isolation over a wide bandwidth. The loads are made by a microstrip-line loaded by three PIN diodes whose states are tuned ON/OFF to obtain 90°, 180° and 270° phase shift relative to the reference (0°). Measurement results show RMS phase and amplitude error equal to 10.3° and 1.2 dB, respectively. The maximum insertion loss is equal to 8.6 dB, leading to a figure of merit of 31°/dB. As shown by simulation, by flipping PIN diodes and use negative voltage for biasing, the maximum insertion loss could be reduced to 3.6 dB (figure of merit of 75°/dB) along with a great improvement in RMS phase and amplitude errors, thus showing the potential of the proposed architecture.