Broadband or full waveguide devices are always desirable and required for many system integrations, such as fiber optics, EW and instrumentation applications. Many broadband devices operating from tens of MHz to 50 GHz were developed and have become available in the industry in recent years. However, the broadband devices in high millimeter-wave bands are still under development and their availability is limited. Among these devices, the full waveguide band frequency sources with +13 dBm or higher power output that are required to drive the standard balanced mixers in V-, E-, and W-Bands are still very expensive and difficult to manufacture.
SAGE Millimeter has introduced a series of full waveguide band externally biased mixers in V- (50 to 75 GHz), E- (60 to 90 GHz), and W-Bands (75 to 110 GHz). These mixers implement high performance GaAs Schottky diodes, a balanced structure and proprietary circuit design to yield full waveguide operation with extreme broadband IF bandwidth. The mixers only require nominal 0 to +5 dBm local oscillator (LO) power and +5 V DC bias. Due to its balanced configuration, these mixers offer low conversion loss and noise figure, less harmonic products and high port-to-port isolations. The IF bandwidth coverage of the mixers is DC to 25 GHz for V-Band and up to DC to 40 GHz for W-Band. The typical input P1dB of these mixers is -5 to 0 dBm. The required 0 to +5 dBm LO driving power for these mixers is readily available from SAGE Millimeter’s low cost SFP series passive multipliers.
While these mixers are designed and manufactured for double sideband operation, they can be reconfigured as single sided mixers by adding proper SAGE Millimeter SWF series high performance waveguide filters to form either upper sideband (USB) or lower sideband (LSB) mixers. In the meantime, they can also be used as up-converters for various transmitting or up-converting system applications. Figure 1 shows the circuit schematic of the mixers.
The conversion loss of the mixer in a given bandwidth of operation is the key specification for any mixer product. Figure 2 shows the conversion losses of the W-Band mixer with local oscillator frequency at 75, 90 and 110 GHz while the RF sweeps from 75 to 110 GHz. When LO is set at 75 GHz, the mixer operates as an upper sideband (USB) mixer. When the LO is at 94 GHz, the mixer operates as both an upper and a lower sideband (LSB) mixer. Finally, when the LO is at 110 GHz, the mixer operates as a lower sideband (LSB) mixer. The external bias of the mixer is +5 V DC/0.8 mA while the LO power is +3 dBm. The plot shows that the mixer exhibits good conversion losses across DC to 35 GHz IF bandwidth while RF swept is from 75 to 110 GHz.
Figure 3 shows the RF port to LO port isolation. Due to the waveguide cut off nature, the IF to LO and IF to RF port isolation is infinite, while the RF and LO leakage at IF port is relatively high- which can be improved by adding an external lowpass filter (LPF). Table 1 shows the main electrical and interface specifications of the featured full waveguide band externally biased mixers.
Although the mixers’ RF and LO ports are equipped with standard waveguides, SAGE Millimeter’s SWC series waveguide to coax adapters can be used to convert the interface to 1.85 or 1 mm coaxial interface. In addition, SAGE Millimeter also offers non-biased full waveguide bandwidth balanced mixers to cover the 18 to 140 GHz frequency range.