Wireless Systems Design

60-GHz Transceiver Flaunts Low Cost And Compact Size

This GaAs-Based, Full-Band Transceiver Chip Set Offers Flexibility And High Capacity For Wireless-Communication Applications.

Frequency spectrum is be-coming a valuable resource in today's wireless systems. As a result, many equipment developers are targeting the unlicensed 60-GHz frequency band for low-cost, high-data-channel communication applications. These applications might include, for example, picocell cellular-backhaul links, campus networks, and communication links for disaster restoration. Velocium has positioned itself well to take advantage of the growing interest in 60-GHz wireless systems. The company, which was recently acquired by TRW, Inc., developed and introduced a monolithic-microwave integrated-circuit (MMIC) transceiver chip set.

This full-band chip set is intended for high-capacity, short-haul designs in the V-band or 55-to-64-GHz frequency range. Among its key technical characteristics are flexibility and compact size. To make up a complete set of RF-transceiver electronics, it only requires eight chips consisting of five different chip types (see figure). These basic chips can be used to design a simplex, half-duplex, or full-duplex mode transceiver.

To create a full-duplex transceiver configuration, for instance, a power divider must be substituted for the local-oscillator (LO) switch. In addition, the transmit/receive (T/R) switch must be removed. This architecture has been used in the production of a low-cost, 60-GHz module that supported a data rate greater than 155 Mbps.

Variations of the complete chip-set architecture can be used to support a wide range of constant envelope modulation formats. These formats include frequency shift keying (FSK), tamed frequency modulation (TFM), and FM. More bandwidth-efficient modulation schemes, like multi-level phase shift keying (MPSK), can be designed as well. They require the implementation of frequency conversion, rather than frequency multiplication, in the transmit LO chain.

The chip set consists of the XDH158 X4 multiplier; the MDB207 image-reject mixer; and the ALH382 low-noise amplifier (LNA). This LNA also acts as a driver amplifier in the transmit chain. The image-reject mixer boasts an IF frequency range of DC to 3 GHz. A sub-harmonic mixer also is available. In addition, the chip set features two radio-frequency switches and a power amplifier that's capable of 18-dBm-output saturated RF power.

The chip set's LNA noise figure is less than 4 dB across the frequency band. It is characterized as a single-ended MMIC with four stages. It is packed into an area that's just 1.3 mm2.

The MDB207 acts as an in-phase/quadrature (I/Q) downconverter. If an off-chip IF hybrid is added to it, the MDB207 also can be configured as an intermediate-frequency (IF) downconverter. With the LO signal at 15 to 17 dBm, image rejection is less than 30 dB.

The SDM126 MMIC is a single-pole, double-throw (SPDT) switch that is used for both transmit and receive selection. It boasts an insertion loss of less than 1.5 dB from 55 to 63 GHz, while the output-port isolation is about 30 dB. To minimize die area without degrading the coupling between the output ports, this chip has a die size of 2.4 mm2.

As for the XDH158 multiplier chip, its function is to multiply a 14-to-16.5-GHz signal at a 4-dBm level to the desired range of 56 to 66 GHz. At the same time, it must maintain a conversion loss of only 8 dB. The XDH158 draws about 14 mA at 1.5 V on the transistor drain channel. In comparison, the integrated amplifier uses 114 mA at 4 V. All harmonics, except for the third, are rejected at greater than 20 dB.

Lastly, the ABH209 power-amplifier chip uses a balanced two-stage design. It therefore achieves a linear gain of 13 dB from 55 to 65 GHz. The linear power is less than 16 dBm over this entire range, while the saturated power is less than 18 dBm. It draws around 110 mA at 5 V for maximum power. The ABH209 has been used as both a LO driver and a power amplifier.

Flaunting a very compact package, Velocium's complete chip set takes up a total die area of only 17 mm2. The MMICs are standard off-the-shelf products fabricated in a high-volume, 0.1-µm and 0.15-µm GaAs PHEMT production process. This low-cost, high-volume, high-reliability process is essential for supporting 60-GHz equipment vendors.

Velocium's 60-GHz transceiver chip set is available now in high production volume. It is priced in quantities of 100,000 units.

Velocium, Inc.
2221 Park Pl., El Segundo, CA 90245; (310) 814-5000, FAX: (310) 812-7011, www.velocium.com.

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