Radio Solutions Reach 66 GHz

March 14, 2012
A company associated with cellular frequencies is now creating a wide range of single- and multifunction solutions for radio communications applications at millimeter-wave frequencies.

Wireless broadband networks and services are expanding, requiring transmitter and receiver components at ever-increasing frequencies through the millimeter-wave range. To meet these growing demands, Hittite Microwave Corp. has developed an extensive line of surface-mount-packaged integrated-circuit (IC) components for microwave and millimeter-wave radio applications, including for local oscillator (LO) generation within the radio. Additional function blocks include a variety of frequency-conversion components, such as double-balanced mixers, and variable-gain amplifiers (VGAs) for amplitude control.

As an example of how these single- and multifunction components can provide effective radio solutions, Fig. 1 shows a function diagram for a microwave radio transceiver solution for the 23-GHz licensed point-to-point radio band. The model HMC819LC5 in the transmit chain is a subharmonically pumped in-phase/quadrature (I/Q) transmitter IC which incorporates a frequency doubler in the LO path, a pair of double-balanced mixer cells, and a single-ended driver amplifier to boost output signals. It is designed to deliver signals from 17.7 to 23.6 GHz and provides 15-dB conversion gain and 35-dB sideband rejection.

It is followed by a model HMC997LP4E VGA which is used between the upconverter and the power amplifier to set the gain of the transmit chain. It boasts continuously variable gain of 5 to 20 dB from 17 to 27 GHz with high linearity. The use of a VGA or voltage variable attenuator (VVA) in this section of the radio allows it to dynamically adjust output power depending upon environmental conditions. After the VGA, a model HMC756 power amplifier serves as the final output stage, with 23-dB gain, +31-dBm output power at 1-dB compression, and +41-dBm third-order intercept point. It is one of the firm's expansive line of power amplifiers, with output levels as high as 4 W across the microwave radio bands.

In the receiver section of Fig. 1, the model HMC967LP4E is a subharmonically pumped I/Q downconverter designed for inputs from 21 to 24 GHz. It incorporates a frequency doubler in the LO path, with a pair of double-balanced mixer cells or frequency translation. The unit accepts a subharmonic LO input between 8.8 and 13.5 GHz and delivers output signals with 25-dB image rejection and only 2.5-dB noise figure. It occupies only 4 x 4 mm of printed-circuit-board (PCB) area and requires only minimal external bias decoupling components. The firm offers a wide selection of transmit and receive chip sets for all licensed radio bands from 6 to 42 GHz.

A critical part of any microwave radio design is the LO section, since the spectral purity of the LO can determine the modulation capabilities and data throughput of the radio. Hittite ultra low phase noise PLL with integrated VCO solutions support up to 1024 QAM.

A low-noise synthesizer generates the LO signals in the Fig. 1 transceiver block diagram. The company offers a family of seven fractional-N phase-lock-loop (PLL) ICs with integrated voltage-controlled oscillators (VCOs) for frequency generation from 7.3 to 13.4 GHz. The latest additions, models HMC767LP6CE, HMC769LP6CE, and HMC778LP6CE, provide frequency coverage from 8.45 to 10.8 GHz in 6 x 6 mm QFN packages. These VCO/PLL ICs feature low open-loop phase noise of -140 dBc/Hz offset 1 MHz from the carrier, a 350-MHz reference path input, and 14-b reference divider. These fractional-N frequency synthesizer ICs incorporate an advanced delta-sigma modulator design that enables fine fractional frequency step sizes with low phase noise and minimal spurious content. They can deliver as much as +12 dBm output power and include a variety of useful features, including double buffering, external triggering, frequency modulation (FM), phase modulation, and exact frequency generation (with near-0-Hz error).

In addition to single-function components, integrated multifunction monolithic-microwave integrated circuits (MMICs), multichip modules (MCMs), and system-on-chip (SoC) solutions, the firm also supplies a complete multicarrier, multiple-communications-standard Zero IF radio receiver design platform (Fig. 2), the model EKIT01-HMC6383 direct-conversion receiver (DCR). It features a 3-dB bandwidth that can be programmed from 3.5 to 50.0 MHz baseband (7 to 100 MHz RF) with 2.5% bandwidth accuracy. The radio design platform offers coverage of input frequencies from 700 to 3000 MHz with 90-dB programmable gain and outstanding linearity, with input second-order-intercept (IIP2) point of better than +60 dBm. A seamless, integrated, image-rejection-calibration algorithm achieves over 90-dB image rejection.

The DCR features an HMCAD1520 dual-channel 12/14-bit ADC that interfaces to a standard FPGA evaluation platform and to a PC via a USB connection. The DCR can also be connected via coaxial cable to Hittite evaluation boards, such as the HMC977LP4E integrated I/Q downconverter, to form a complete microwave radio receiver evaluation board. This robust, modular, fully configurable receiver design is an invaluable tool for engineers developing radios for any number of different multicarrier wireless communications standards. In addition to this modular approach, the company can also combine multiple functions, such as those required for a frequency synthesizer, on a single chip to achieve significant reductions in size.

For applications in the 57-to-66-GHz Industrial-Scientific-Medical (ISM) band, the firm offers a highly integrated silicon transceiver chipset targeting 60-GHz applications such as picocell backhaul and short-range multi-Gbps-data-rate indoor communication links (WiGig). The 60-GHz chipset provides all the necessary functionality to translate an I and Q baseband analog signal to a selected channel in the 60-GHz ISM band, using only an external low-frequency reference clock oscillator. For ease of use, the chips are also offered in packages with connectors and as antenna-in-package solutions.

For example, an antenna-in-package solution combines a 60-GHz antenna with 60-GHz transmitter/receiver chips in a low-cost, plastic QFN package. The device can be mounted on a low-cost PCB, since the highest-frequency (baseband electrical connection is below 1 GHz). For test purposes, the company offers the model HMC6450 Antenna-in-Package Transceiver Evaluation Kit (Fig. 3), and provides everything needed for the user to quickly set up a bi-directional link at 60 GHz with a universal analog baseband I and Q interface.

Hittite Microwave Corp.
2 Elizabeth Dr.
Chelmsford, MA 10824
(978) 250-3343
FAX: (978) 250-3373

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