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Fast Tuned Active High-Q MMIC Filters for AESA Radar Applications

Fast Tuned Active High-Q MMIC Filters for AESA Radar Applications. Why Do It?. Fast Tuned Notch Filter (FTNF) Concept originally developed for Electronic Surveillance (ES) systems, to counter on-board Frequency Agile, High Duty Cycle emitters

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Fast Tuned Active High-Q MMIC Filters for AESA Radar Applications

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  1. Fast Tuned Active High-Q MMIC Filters for AESA Radar Applications

  2. Why Do It? • Fast Tuned Notch Filter (FTNF) Concept originally developed for Electronic Surveillance (ES) systems, to counter on-board Frequency Agile, High Duty Cycle emitters • However, Radars also experience a wide variety of in-band interferers: • Naval – Consort ship emitters, intentional Interferers, unintentional interferers • Air – Wing-man emitters, intentional Interferers, unintentional interferers • Other Functions (eg ES) are desirable: • Requires mitigation of own Tx break-through • All the above applications require highly agile filtering, and extremely low SWaP to embed in Radar Transmit Receive Modules (TRMs)

  3. X-Band MMIC FTNF Advantages • Enables dynamic management of AESA Radar in-band interferers • Extremely Compact Design • Chip dimensions 2.5mm x 2.5mm • Suitable to integrate into Radar TRMs • Low RF & support component count • Minimal board footprint • High MTBF • Simple control scheme • Only two analogue inputs required to control the notch frequency and depth. • One enable / disable line Freq Control Notch On/Off MMIC Notch Filter RF I/P RF O/P Gain Control Bias -V Bias +V

  4. X-Band MMIC FTNF Initial Test Jig Test Results • High Q Stable notch response • 2GHz tuning range (previous hybrid design was 1GHz) • Notch depths >-30dB (can be dynamically varied) • Low insertion loss • VDD = 4V, IDD = 40mA, 160mW • Note: gap in middle due to design error – now resolved

  5. IMD3 Measurements – 9.38GHz • Third order product measured with one i/p signal in the notch and one out of the notch • I/P powers -10dBm and 0dBm single tones 0dBm Input Power -10 dBm Input Power

  6. MMIC FTNF With bandpass tap • The FTNF can include a port to monitor the attenuated interference signal • Enables truly dynamic interferer management • Optimises spectrum visibility

  7. Control Aspects – Fast Tuning • Fast Tune Speed typ 250ns • Requires: • High Speed DAC and Switch Ctrl • High Speed Memory Function • Programmable Logic (FPGA) / NVRAM • High Speed Interface • Parallel – Practicalities of routing across TR array • High Speed Serial – Power Dissipation • Size and Power Penalty • Control can be shared across sub-arrays

  8. Control Aspects (Continued) • Slow Tune Speed typ 30us • Use single system on chip (microcontroller with peripherals, inc DAC and Op-Amps) • e.g. MAXQ8913, PIC16F1778 • Low Power • Typically 5x5mm Package • Possibly in Bare Die • Serial SPI Interface @1Mbps • 10 bit Freq in 10us, DAC settle in 20us = 30us

  9. Outline Specification All-pass frequency range 6-18GHz Notch Tuning Range 8.5 – 9.5GHz V1 8.5 – 10.5GHz V2 Notch width (-15dB) 30MHz typ Notch width (-5dB) 150MHz typ Allpass insertion loss <1dB (full band) <0.4dB typ 8-10GHz Return loss outside notch 20dB typ allpass 20dB typ Input IP3 -10dBm i/p pwr 22dBm typ (one signal in notch) 0dBm i/p pwr 12dBm typ Max input power +20dBm abs max Tuned ‘tap’ output tbd Notch control allpass/notch 0V / -5V Frequency control -4V to -20V Notch depth control 0V to +2.5V (5mA) Supply voltage +4V / 40mA -3V max (gate bias)

  10. MIC/MMIC Hybrid S-band FTNF • The passive circuits used in the X-band FTNF MMIC become too large to be feasible for full MMIC implementation. • Solution is Hybrid MIC/MMIC layout where the Passive parts are implemented on alumina MIC substrate and the active parts, the amplifiers ans attenuator are implemented on MMIC. • The Hybrid design can be implemented in a 12 x 6 mm MIC tile.

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