In this paper, a millimeter-wave (MMW) dual-mode and dual-band switchable Gilbert up-conversion mixer in a commercial 65-nm complementary metal oxide semiconductor (CMOS) process is presented. By simply changing the bias, the proposed CMOS Gilbert up-conversion mixer can be switched between subharmonic and fundamental operation modes for MMW dual-band applications. With a low local oscillator pumping power of 3 dBm and low dc power consumption of 6 mW, the proposed CMOS Gilbert up-conversion mixer exhibits a measured conversion gain of −0.5 ± 1.5 dB from 37 to 50 GHz and 2.5 ± 1.5 dB from 17.5 to 32 GHz for the subharmonic and fundamental modes, respectively.

A compact dual-band bandpass filter using stub-loaded stepped impedance resonator (SLSIR) with cross-slots is presented. The symmetric SLSIR is analyzed using even- and odd-mode techniques. Design equations are derived and they are used to guide the design of the circuits. Two passbands can be easily tuned by cross-slots and open stubs. Transmission zeros among each passbands are created, resulting in high isolation and frequency selectivity. An experimental circuit is fabricated and evaluated to validate the design concept. The fabricated filter is compact with 19.76 × 12.7 mm2. The measurement results are in good agreement with the full-wave simulation results.

Ultra-compact band-pass filters with Nth-order pseudoelliptic response are presented allowing dramatic volume and mass savings (up to about 90%) compared to conventional filters at the price of a modest Q-factor reduction. TM dual-mode cavities loaded with high-permittivity (εr > 30) ceramic cylinders are employed, while non-resonating modes are used to create N transmission zeros symmetrically or non-symmetrically located in the pass-band. A single cavity behaves as a generalized doublet generating two transmission poles and two transmission zeros and is used as a basic building block for N-pole and N-zero filters with symmetric or asymmetric response. To prove the effectiveness of the approach, a very compact fourth-order filter with 4.35 GHz center frequency, four transmission zeros has been designed, fabricated, and tested showing an unloaded Q close to 2000. It is finally shown that the filter response can be shifted in frequency by simply replacing the dielectric material with another having different εr, so that the same metal enclosure can be used to realize various filters operating at different frequency bands.