Using conventional 0.25pm HEMT (VLN02 process) and pseudomorphic 0.15pm HEMT (MM015 process), a highly integrated and low power consumption receiver has been developed for a W-band radiometer. All the millimeterwave functions and even the first stage of IF amplifier are fully integrated on MMIC technology according to a multifunction approach. A compact housing has been developed for chip integration. A high performance oscillator at LO sub-harmonic provides less than -93dBc/Hz at lOOliHz from carrier at 46.6GHz. The complete frontsnd assembly exhibits more than 20dB conversion gain and less than 6.5dB noise figure around 93.5GHz RF frequency and 100 to 600MHz associated IF frequency. To our knowledge this realization is the first report of a fully monolithic W-band complete front-end based on industrial HEMT technologies and dedicated to space applications.
-INTRODUCTIONIn the next future the development of mobile broadband communication systems will include circuits working at millimeter-waves around 60 GHz.Most of these systems will require frequency synthezisers where frequency-dividers will be among the key circuits. At those frequencies only analog frequency dividers are available.The aim of this paper is to propose an HEM" MMIC analog frequency divider by two working with input frequencies around 60 GHz, to demonstrate the ability to design state of the art non linear circuits at millimeterwaves using available CAD software and foundry models.
FREQUENCY DIVIDER CONCEPTIONThe working principle of the analog frequency divider [l], [2] is that of a closed loop oscillator in which the output signal at the divided frequency is fed back and mixed with the external signal to produce a lower sideband at the output frequency, which will be filtered and amplified. A phase relation must exist between the injection signal and the output signal in order to get a synchronous (phase sensitive) stable regime which is the regime of interest. In the absence of an input signal the oscillation is quenched by reducing the feed-back loop gain.The bifurcation detection is a powerful method to determine the steady state and operating bandwidth of synchronised circuits such as frequency dividers. However this method requires a specific algorithm [3], [4] which is not available in commercial CAD software. To simulate such non-linear unstable circuits we have developed a new method based on the open loop concept which has been widely used for the design of linear feedback amplifiers [5], [6]. As a matter of fact, in this method, the frequency divider is considered as a non-linear closed loop circuit. To analyze it in a simple manner as a stable forced amplifier, the loop is opened following the procedure given by figures 1 t o 5 : Figure 1 shows a simplified closed loop diagram of a frequency divider, where FO is the input frequency. The output filter eliminates the injection signal FO at the divider output and a feedback circuit allows to perform the regeneration at -. Most of the time the mixing and ampllfying functions are performed by a single FET transistor biased near pinch-off. For simulation purposes, the non-linear model of the HEMT shown in figure 2 has to be used. When considering the whole circuit of figure 1, we can redraw it in the form represented in figure 3 where we have separated the non linear part of the circuit, the load and the input injection generator. The linear part of the circuit is fully included in the linear block Q. The key of the new analysis method may be now summarized in the two following steps : i) : we open electrically the closed loop of figure 3 by replacing the controlling voltage Vgs of the drain source by a voltage Vext as shown in figure 4.ii) : we duplicate this cell and cascade N of them (N = 4 or 5 ) as shown in figure 5 . In these cells the drain current source is now controlled by the gate voltage of the preceding cell. Clearly the drain c...
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