Leveraging Harmonic Phase States in E-Band Multipliers to Improve Spectral Purity

As demands for spectral purity rise alongside stricter regulations and more precise measurement equipment, the need to advance frequency conversion techniques rises accordingly. One therein largely neglected aspect is to use information already provided by the input signal, its phase. Opposed/aligned phases lead to destructive/constructive interference depending on either the common or differential mode of the signal. Precise control over the harmonic phases (phase states) after each frequency multiplication may promote frequency selectivity, improving the harmonic rejection ratio. Yet phase control below quadrature (<90°) input signals is seldom applied and insufficiently studied at higher frequencies. To explore prospective performance benefits, two new multiplication approaches with eight equiphasal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \varphi = 45^{\circ } $ </tex-math></inline-formula> signals are demonstrated in the E-band (60–90 GHz). These proof-of-concepts offer configurations for distinct input phase relations and different combining techniques to quadruple the Ku–K-band input frequency. Their novel mathematical and graphical derivation alongside means to generate the input signals polyphase filter (PPF) and mitigate their faults (phase correction buffers) are further presented. An extension toward D-band frequencies (110–170 GHz) is additionally explored with an applied doubler and amplifier. Each quadrupler (and the octupler) is realized in chip dimensions of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1550\times 600~\mu $ </tex-math></inline-formula>m in Infineon’s B12HFC 90 nm technology and draws 90.4/84.4 mA (100 mA as an octupler) from a 3.3 V supply. With 3 dB-bandwidths of 32/12 GHz (39 GHz for the octupler), held back in the latter by internal filtering, a state-of-the-art competitive maximum harmonic rejection up to 33.9/35.5 GHz (38.3 GHz) with output powers of 0.32/−0.97 dBm (1.37 dBm) is achieved.