Ultra-wideband 3-20 GHz mixer integrates LO buffer for 23.9 dBm IIP3
The device offers linearity of 23.9 dBm IIP3 at 14 GHz, and 21.5 dBm at 17 GHz: it integrates an LO (local oscillator) buffer requiring only 0 dBm input drive, effectively eliminating an external high power LO amplifier circuit. LTC5553 also integrates wideband balun transformers on chip, enabling all ports to operate single-ended, 50Ω matched over their respective specified frequency range. The mixer has excellent port-to-port isolation, offering –32 dBm LO to RF leakage at 17 GHz, easing external filtering requirements. All of these features result in minimum external components, simplified design and a very small solution size.
The LTC5553’s extremely wide bandwidth and performance suits it for applications including 5G microwave backhaul, broadband wireless services, satellite broadband radios, radar systems, active antenna arrays, X and Ku band transceivers, test equipment, spectrum analysis and satellite communications.
The LTC5553 comes in a tiny 12-lead, 3 x 2 mm plastic QFN package, rated for operation from -40°C to 105°C case temperature to support extended environmental operating temperature. The mixer is powered from a single 3.3V supply, drawing a quiescent supply current of 132 mA. It can be shut down via an enable pin. When deactivated, the device draws 100 μA maximum standby current. The enable pin can be driven directly to turn the device on and off rapidly in less than 200 nsec, supporting time-division duplex (TDD) or burst mode type transmitters and receivers. The LTC5553 is priced starting at $22.00 (1,000).
Analog Devices/Lineat Technology; www.linear.com/product/LTC5553
next page; specification listing, and background on the chip design…
Summary of Features: LTC5553
Matched RF frequency 3 GHz to 20 GHz
Matched LO frequency 1 GHz to 20 GHz
Matched IF frequency 500 MHz to 9 GHz
Up- or downconversion
High input IP3: 23.9 dBm at 14 GHz
21.5 dBm at 17 GHz
Low LO drive level: 0 dBm
Low LO-RF leakage: –32 dBm at 17 GHz
Low conversion loss: 11 dB at 17 GHz
Improving microwave mixer technology
Linear adds; Most microwave mixers are built using GaAs FETs or diodes in hybrid modules. While this technology provides very high frequency capability, however, integration is more difficult to attain. In contrast, the LTC5553 is constructed using a very high frequency advanced SiGe BiCMOS process. Therefore high level of integration is a huge advantage by packing an on-chip LO buffer amplifier and ultra-wideband microwave balun transformers. The monolithic die is flipped and soldered onto a 3 x 2 mm lead-framed, plastic surface mount package. Bond wires are eliminated, greatly enhancing the device’s microwave frequency performance without introducing bond wire inductances. Its inherently small package, along with minimum external circuitry, makes for a significantly smaller solution size. The small footprint enables the possibility of packing in massively parallel active antenna arrays implementation of beam-steering phased-array architecture.
Integrating the wideband LO buffer amplifier simplifies the task for the designers. Since the LO input requires only a 0 dBm drive, it effectively eliminates having an external high power LO amplifier. Not only does it save costs, it also eliminates having a +10 dBm to +17 dBm power signal in the system. At frequencies 10’s of GHz, such high power signal is potentially a major source of LO radiation that can couple to the RF or the IF ports, as well as other sensitive radio circuits. Thus more filters may be required to keep signal corruptions under control, as well as extra shielding hardware may be necessary to contain the radiation.
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