Microwave Engineering Europe - December 2007 - (Page 13) COVER FEATURE: DC - 86 GHz MMICs 13 and the die mounting surfaces of the HMC-ALH509 LNA and the HMC-APH633 MPA are Ti/Au metallized, and feature fully passivated HEMT devices to ensure rugged and reliable operation. All of these die are compatible with conventional die attach methods, as well as thermocompression and thermosonic wire bonding, making them ideal for MCM and hybrid microcircuit applications. One of the more popular millimeterwave bands spans 57 to 64 GHz, where there is 7 GHz of available bandwidth which straddles a peak in the atmospheric absorption of the electromagnetic waves. This portion of the spectrum is particularly attractive for secure communications in military applications, where the high atmospheric attenuation makes electronic eavesdropping very difficult. This high absorption property also affords dense frequency reuse in a wireless network situation, since adjacent radio links are less Figure 4: Gain and output P1dB versus frequency for the likely to interfere with each HMC-APH633, 71 to 76 GHz GaAs MMIC HEMT MPA. other. As a result of the high absorption rate, the FCC allows a generous amount of maximum output power three stage MMIC LNA which is fabricated to users in this band to enable sufficient in a GaAs HEMT process, and is specified transmission distances. for operation from 71 to 86 GHz. The HMCIn contrast, the 71- 76 GHz and 81 ALH509 features 14 dB of small signal – 86 GHz bands, which are designated as gain, 4.5 dB of noise figure and an output unlicensed FCC bands, are characterized by power of +7 dBm at 1dB compression. The a relative null in the atmospheric absorption. HMC-ALH509 consumes only 50 mA from This property allows longer distance radio a +2 V supply and incorporates a balanced links, and reduces the required emission topology which enhances stability margin levels. This same feature is also useful for and provides excellent I/O return losses. The other applications such as military and satellite HMC-ALH509 requires only two off-chip communications, radio astronomy, radio bias decoupling capacitors, and no external navigation, and of course terrestrial point matching components. to point millimeterwave radios. While it can The HMC-APH633 is a two-stage GaAs be less expensive to build communications MMIC Medium Power Amplifier which is also systems at lower frequencies, the shorter ideal for E-Band radio applications (Figure wavelengths associated with the millimeter 3 and 4). The HMC-APH633 is fabricated in wave bands offers several system level a GaAs HEMT process, and is specified for advantages such as smaller antennas for a operation from 71 to 76 GHz. The HMCgiven beam width, and higher data capacity in APH633 delivers 13 dB of gain at midband, a given percentage bandwidth. and a consistent +20 dBm output P1dB across While Millimeterwave Point-to-Point Radio the band. The HMC-APH633 requires no architectures can vary widely depending external matching components, and consumes on the application and the associated cost only 240 mA from a +4 V supply. goals, the block diagram shown in Figure As with all of the MMIC products in the 5 is an example of how Hittite chip and Hittite – Velocium product line, all bond pads Figure 3: Photomicrograph of the HMC-APH633, 71 to 76 GHz GaAs MMIC HEMT MPA. SMT packaged components can be used to assemble 71 – 76 and 81 – 86 GHz transceivers. The example transceiver features QPSK modulation, double up conversion, double down conversion, one crystal reference, and only two standard VCOs. As shown in the frequency generation section, the HMC583LP5E Voltage Controlled Oscillator (VCO) with RF/2 and divideby-4 outputs, the HMC440QS16G Phase/ Frequency Detector, and the HMC432E Divide-by-2 Prescaler can be combined to quickly fabricate an LO source with +11 dBm output power, and very low SSB phase noise. The HMC440QS16GE Phase/Frequency Detector incorporates a 5 bit counter which can provide any divide ratio from 2 to 32. In the example shown, the counter is set to divide by 25, and the reference oscillator is cut for 63 MHz, such that the fundamental LO output frequency is locked at 12.6 GHz. Note that the RF/2 and the divide-by-4 outputs of the HMC583LP5E VCO help to reduce the number of parts needed to generate the LO signal at 12.6 GHz. The RF/2 output of the HMC583LP5E is divided by 2 in the HMC432E divider, and then amplified in the HMC313E HBT Gain Block. The LO signal at +15 dBm is used to drive the LO port of the HMC620LC4 I/Q Mixer IRM in the transmit path. This mixer is ideal for use as a QPSK modulator, accepting baseband data at its I and Q ports, and upconverting to 3.15 GHz. A cascade of multiplication is used to generate the E-Band LO frequency which is required for the final upconversion. The fundamental output of the HMC583LP5E VCO is multiplied in the HMC576LC3B X2 Active Multiplier, and further multiplied in the HMC-XTB106 X3 Passive Multiplier for a total multiplication factor 6. The HMC-AUH318 Medium Power Amplifier is used to boost the 75.6 GHz LO signal. The HMC-MDB277 Double Balanced Mixer is used as the final upconverter in the transmit section while a cascade of amplifiers is used to generate the Tx output with approximately +20 dBm output P1dB. The HMC625LP5E Digital Variable Gain Amplifier, and the HMCVVD104 Voltage Variable Attenuator are used in the transmit chain to provide IF and RF gain control, respectively. The HMC-MDB277 is also used as the first downconverter in the Rx chain, and is preceded by the HMC-ALH509 Low Noise Amplifier. In the example shown, the Rx chain operates at 83.16 GHz, where the HMC-ALH509 exhibits 4.5 dB noise figure and 14 dB gain, and makes an ideal low noise stage. After downconversion in the HMC- Microwave Engineering ● December 2007 ● www.mwee.com www.mwee.com http://www.mwee.com
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