Ian Gresham

A compact manufacturable 76-77-GHz radar module for commercial ACC applications

The design and measured results of a single-substrate transceiver module suitable for 76-77-GHz pulsed-Doppler radar applications are presented. Emphasis on ease of manufacture and cost reduction of commercial millimeter-wave systems is employed throughout as a design parameter. The importance of using predictive modeling techniques in understanding the robustness of the circuit design is stressed. Manufacturing techniques that conform to standard high-volume assembly constraints have been used. The packaged transceiver module, including three waveguide ports and intermediate-frequency output, measures 20 mm/spl times/22 mm/spl times/8 mm. The circuit is implemented using discrete GaAs/AlGaAs pseudomorphic high electron mobility transistors (pHEMTs), GaAs Schottky diodes, and varactor diodes, as well as GaAs p-i-n and pHEMT monolithic microwave integrated circuits mounted on a low-cost 127-/spl mu/m-thick glass substrate. A novel microstrip-to-waveguide transition is described to transform the planar microstrip signal into the waveguide launch. The module is integrated with a quasi-optical antenna. The measured performance of both the component parts and the complete radar transceiver module is described.

Ultra wide band 24 GHz automotive radar front-end

The recent approval granted by the FCC for the use of Ultra Wide Band (UWB) signals for vehicular radar applications has provided a gateway for production of these sensors as early as in 2004. However, the rules governing the allowable spectral occupancy create significant constraints on the sensors operation. The implications for waveform design and the consequent limitation on system architecture, including antenna design and receiver architecture are discussed. Other practical considerations such as available semiconductor technology with low-cost plastic packaging are reviewed. This is developed into a methodology for developing a single board sensor with integrated antenna. Results are presented for a specification compliant antenna, and a low-cost plastic package for 24 GHz ICs. Finally, the required IC architecture for a transceiver is presented, along with measured results of a single-chip homodyne I/Q down-conversion receiver fabricated in SiGe.The recent approval granted by the FCC for the use of Ultra Wide Band (UWB) signals for vehicular radar applications has provided a gateway for production of these sensors as early as in 2004. However, the rules governing the allowable spectral occupancy create significant constraints on the operation of the sensors. The implications for waveform design and the consequent limitation on system architecture, including antenna design and receiver architecture are discussed. Other practical considerations such as available semiconductor technology with low-cost plastic packaging are reviewed. This is developed into a methodology for developing a single board sensor with integrated antenna. Results are presented for a specification compliant antenna, and a low-cost plastic package for 24GHz ICs. Finally, the required IC architecture for a Transceiver is presented, along with measured results of a single-chip homodyne I/Q down-conversion receiver fabricated in SiGe.

A fully integrated 24 GHz SiGe receiver chip in a low-cost QFN plastic package

A fully integrated, plastic packaged, 24 GHz SiGe receiver chip is presented. The chip has been manufactured using a commercially available SiGe foundry process. It can be used in a variety of applications including automotive radar sensors and phased-array receivers. The receiver supports two channels which can be used to support sum and delta antenna pattern inputs. The receiver comprises of two LNAs, a DPST switch, an I/Q downconverter, baseband variable gain amplifiers, and integrate-and-dump filters. The receiver has 45 dB of conversion gain with 7.8 dB noise figure (with plastic package) at 24 GHz

A fast switching, high isolation absorptive SPST SiGe switch for 24 GHz automotive applications

Measured results for a high isolation, extremely fast switching SPST SiGe switch are presented. The switch provides ~35dB of isolation between input and output over 15GHz-26GHz, yet is only 500¿m × 250¿m in size. A novel load circuit ensures that there is almost no perceptible change in the input reflection coefficient of the switch between the transmission and the absorptive state. In the transmit state the switch provides gain for the input signal between 14.2GHz and 25.5GHz, and has a 1dB loss bandwidth of over 12GHz. Lastly, the use of a constant current biasing scheme allows extremely fast switching between states allowing the switch to be used to generate RF pulses of 200pS in length at a carrier frequency of 24GHz, with rise and fall times of approximately 60pS. The entire switch, including biasing circuitry, requires only 12mA from a +5V supply.

Design of 24 GHz SiGe HBT balanced power amplifier for system-on-a-chip ultra-wideband applications

The design of a balanced, three-stage, common-emitter, 24 GHz SiGe HBT power amplifier for ultra-wideband applications is described. The unique features of the amplifier are very flat gain response in the frequency band of interest and sharp gain drop outside of the band, which are important considerations for a system-on-a-chip UWB application. The amplifier has 18 dB nominal gain in the frequency band of 24/spl plusmn/2 GHz. The gain variation is /spl plusmn/0.5 dB in the same frequency band. Saturated output power is 12 dBm at 24 GHz.

A 76-77 GHz pulsed-Doppler radar module for autonomous cruise control applications

A single-substrate radar transceiver module suitable for 76-77 GHz pulsed-Doppler applications has been developed. The packaged transceiver, including three waveguide ports and IF output, measures 20/spl times/22/spl times/8 mm. The circuit is realized using discrete GaAs-AlGaAs PHEMTs, GaAs Schottky diodes and varactor diodes, as well as GaAs PIN and PHEMT MMICs mounted on a low-cost 127 /spl mu/m thick glass substrate.

A differential sub-nanosecond high-isolation absorptive active SiGe 24 GHz switch for UWB applications

This paper presents the design and measurement of a SiGe sub-nanosecond, high isolation, single-pole double-throw (SPDT) and single-pole single-throw (SPST) differential absorptive active switch at 24 GHz for ultrawideband (UWB) applications. The switch and digital driver consume 24 mA from a 5 V supply. The active area of the SPDT and SPST is 1000 /spl mu/m /spl times/ 550 /spl mu/m and 670 /spl mu/m /spl times/ 340 /spl mu/m respectively. The novel circuit topology implements a SPDT that inherently maintains the port impedances regardless of the state of the switch. The insertion loss is less than 3 dB over the 20-26 GHz range and the isolation is >42 dB at 10-30 GHz with a switching time of 100 ps.

A low-noise broadband SiGe mixer for 24GHz ultra-wideband automotive applications

The design and measured results for a broadband, miniature active mixer for use in a direct-down conversion I/Q receiver is presented. The high instantaneous bandwidth of a short-pulse radar system requires a broadband frequency domain response. In addition, the cost constraints and thermal demands require the RF front-end of the automotive radar system to be highly integrated, and energy efficient. The mixer displays a conversion gain of over 20 dB - including the contribution of the base band output stage - over the 3 GHz-35 GHz frequency range for an IF frequency of 500 MHz and an LO drive of 0 dBm. The double-side band (DSB) noise figure of the mixer is less than 8 dB at 24 GHz. The circuit occupies less than 0.075 mm/sup 2/. The entire mixer, including biasing circuitry, requires only 22 mA from a +5 V supply.

Multimode TRL and LRL calibrated measurements of differential devices

A multimode TRL (MTRL) calibration technique is discussed to characterize broadband differential devices. This algorithm has the advantage of using ground-signal-signal-ground (G-S-S-G) probes in the measurements without the frequency limitations of some other 4-port algorithms due to the coupling between the signal lines. Calibration standards and the issues associated with them are described. Practical issues of the underlying theory, such as assigning the calculated eigenvalues to the correct mode and to the propagation direction, have also been addressed and one case-specific solution is suggested. Also an MTRL algorithm has been adopted to avoid some of the difficulties of calibration structures with MTRL. Odd mode test results of differential active circuits with MTRL using G-S-S-G probes are shown to be consistent with the two port test results of the same devices using S-G probes.

Si Based UWB Radar Sensors

Automotive short-range sensor networks at 24 GHz represent the first truly high volume commercial system at mm-wave, with first year production quantities already eclipsing previous products such as autonomous cruise control (ACC), and the various microwave radio networks (e.g. LMDS). The emphasis on product quality, reliability, cost, and performance demanded by automotive OEMs has meant that an innovative approach to product development, packaging, and test has had to be introduced to mm-wave products. This paper will highlight some of the key technical hurdles and their solutions in the development and introduction to production of a 24 GHz UWB radar sensor based on custom-designed SiGe ICs.