> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract—A compact, broadband, high gain, second-order active down-converter subharmonic mixer is demonstrated using a 130-nm SiGe BiCMOS technology. The mixer adopts a bottom- LO Gilbert topology, on-chip RF and LO baluns and two emitter-follower buffers to realize a high gain wideband operation in both RF and IF frequencies. The measured performance exhibits a flat conversion gain (CG) of about 11 dB from 90 to 130 GHz with an average LO power of +3 dBm and high 2LO-RF isolation better than 60 dB. The mixer shows an input 1-dB compression point of -16 dBm consuming a dc power of only 40 mW. The chip dimension is 0.4 mm 2 , including probing pads. It demonstrates also up to 12 GHz 3-dB IF bandwidth, which to the authors’ knowledge, is the highest obtained among active mixers operating above 100 GHz Index Terms—SiGe MMICs, millimeter-wave, subharmonic mixer (SHM), conversion gain. I. INTRODUCTION UBHARMONIC mixer (SHM) is an attractive candidate for frequency conversion in micro-wave and millimeter-wave transceivers. It requires only a fraction of the local oscillator (LO) frequency compared to a fundamental mixer and increases the LO-to-RF isolation significantly. Unfortunately, most of the high frequency SHMs above 100 GHz have conversion loss which imposes rigorous noise figure and gain requirements on low noise amplifier and following building blocks of receiver chain [1, 2, 4]. On the other hand, to realize a high gain amplifier at the RF or IF side, usually three to five stages are utilized, where it burdens the power budget of a low power system. Therefore, implementing a millimeter-wave down-converter SHM is challenging with respect to conversion gain, bandwidth, noise figure and linearity requirements. Recently, several efforts have been done in literature to design high gain SHMs. In [3], a transformer-based gm- boosting Top-LO Gilbert SHM is presented operating at 79 GHz, where a conversion gain of 1.6 dB with a LO power of - 5 dBm is achieved. This technique boosts the RF transconductance without additional power consumption. However, it is difficult to achieve a large gain for input frequencies higher than 90 GHz due to the additional loss of transformer network. In [4, 5], a two-stage subharmonically pumped transconducance mixer is introduced that reaches to maximum 6 dB and -1 dB conversion gain at V-band and D- band using a 5 dBm and -1 dBm LO power, respectively. This type of mixer features broadband operation. Nonetheless, it suffers from conversion loss and requires an optimal base bias along with a large driving LO power. Therefore, both mixers employ a power hungry IF buffer which correspondingly leads to 120 mW and 262 mW total power consumption. Another SHM topology is a modified Gilbert cell based on two stacked switching quads, which is used in [6] for 122 GHz. This topology shows better conversion gain compared to a Gilbert cell configuration with parallel transistor stacks. However, as the frequency goes up, the maximum conversion gain of the mixer occurs by non-quadrature LO signals. Hence, a novel hybrid with an arbitrary phase shift is needed in order to provide an optimum LO phase distribution. Furthermore, due to the several stacked transistors, a larger supply voltage is required to avoid the compression of the output voltage amplitude, which inevitably influences the power consumption of whole circuit. This letter reports a high gain wideband bottom-LO Gilbert SHM that is designed to operate at F-band frequency. The mixer is implemented in a single balanced arrangement, driven by a differential LO- and RF- scheme. It also generate anti- phase IF signals which are broadly matched at the output to 50 Ω through the emitter followers. II. CIRCUIT ANALYSIS AND DESIGN The subhramonically pumped bottom-LO Gilbert mixer was first demonstrated at 930 MHz [7] and is well described in [8]. Unlike a conventional topology which implements the mixer function by a transconductor followed by current commutating switching; this scheme achieves the same functionality by the switched transconductors. One of the main advantages of bottom-LO topology is the high LO-to-RF and high LO-to-IF isolation. This is because the LO signal appears in common- mode at both RF and IF ports. Furthermore, any LO leakage to the RF port is mixed with the second harmonic of LO frequency due to subharmonic operation, which is back to the same LO frequency and is well filtered out at the next stage. Therefore, this topology is utilized here to design a full F- Band SHM for the first time. Fig. 1 depicts the simplified schematic of the proposed wideband single-balanced SHM along with a fabricated chip photo. The circuit consists of a push-push frequency doubler LO-stage (Q1s/Q2s), a differential RF transconductance stage (Q1/Q2), two emitter-follower buffer-stage (Q1b/Q2b), and two on-chip Marchand baluns at RF and LO ports. The LO- stage acts as a frequency doubler to convert input differential A SiGe High Gain and Highly Linear F-Band Single-Balanced Subharmonic Mixer Neda Seyedhosseinzadeh, Abdolreza Nabavi, Sona Carpenter, Zhongxia Simon He, Mingquan Bao and Herbert Zirath S