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MDHL: bridging the design and communication gap.

MHDL: Bridging the Design and Communication Gap (*)


The DARPA/Tri-Service microwave/mm-wave monolithic integrated circuit program addresses the need for advanced electronic design automation (EDA) tools as part of its overall objective of establishing a MMIC industrial base. The result has been an increase in variety and capabilities of tools available, including improved user/graphical interfaces. Using these tools, a MMIC designer can capture a design, simulate performance and produce layout artwork with the aid of design rule checking, in a single integrated computer-aided environment. These tools contribute significantly towards making MMICs available and affordable. However, a major barrier to this objective is inefficient and incomplete communication of many aspects of microwave design.


for Enhanced Productivity

Microwave designers must achieve first-pass design success. Accurate, integrated CAD tools are an aid to reduce risk and cost. Accurate modeling and simulation techniques make it possible for a designer to experiment with trade-offs in the design cycle, predict and optimize performance, and avoid pitfalls before the costly manufacturing process.

While the capabilities and features of microwave computer-aided design tools have increased greatly in the past few years, today's tools focus on supporting only pieces of the design process with little coupling to the manufacturing process. Most of the capability lies in the area of circuit design, where dedicated CAD tools exist. While several tools complementary of microwaves simulation are available, that is, packaging, mechanical, eletromagnetic and system simulators, links between these tools are weak. The result is a CAD system that has limited functionally with respect to the overall design, production and life cycle.

System level simulation tools are emerging to complement the design process. A critical challenge is communicating the information of designers working at the system and component levels. System specification and documentation are now captured on paper and are often incomplete and ambiguous; often there is difficulty maintaining the required information. A standardized mechanism or bidirectional communication between the component and system engineer does not exist. This makes system maintenance or upgrades difficult to achieve. Such communication would provide a cross-check to correlate design insertions. This correlation provides a level of confidence that the components are properly specified before they are designed or procured. Insertion of new technology into systems would be facilitated if technology independent descriptions, including statistical variations, could be used. Productivity enhancement would be achieved by the development of means to facilitate the entire system life cycle.

Communication of specifications and requirements between the system and component levels, and between designers, testers and manufacturers needs to be facilitated, as shown in Figure 1. Capturing description of the interaction with non-microwave portions of the system, that is digital control functions, will be necessary. Emerging CAD tools encompass some of these capabilities, but are typically oriented towards the circuit level designer.

Sharing of electronically generated descriptions and models is needed to facilitate technology insertion. Simulation of microwave circuits built from element models is available in today's CAD tools. However, there are often differences between the models as well as which models are supported, which leads to a difficulty in exchanging designs. These microwave component models exist in a form which is built into a particular simulator. Sharing models among CAD tools is desirable, but is not yet possible.

Increasing microwave circuit functionality and complexity requires that testability be considered before the part is built. Testability must be considered by test and manufacturing engineers, and by designers. Including design for test features into the design is becoming mandatory. Testin is the highest single cost of an MMIC chip. Also, each company or organization handles the testing of components in an individual manner. Testing procedures must be standardized so that test results can be duplicated.

Challenges for MHDL

A solution to most these challenges is MHDL. What is a hardware description language? In general, it is a computerized means to provide communication of the behavior, structure and other aspects of the microwave hardware being described. To be successful, an HDL must be widely accepted and standadized.

MHDL will allow description of input and output behavior and specification, interfaces with external components and test information. By capturing such a complete, unambiguous description of a system in a form that is communicable, MHDL will greatly improve the design process and improve system maintainability.

MHDL will provide various abstractions or views for a piece of microwave hardware. The budget office may view the microwave system in terms of financial information, while the program management office seems it in terms of project milestones, and the system designer view it in terms of functional blocks to be assembled. Although all of these people may be viewing the same information, each sees it in his own terms, as shown in Figure 2. MHDL will provide both a variety of abstractions as well as allow organization of information into hierarchical form. Although abstractions related to budget and project issues have been discussed, the major focus of MHDL, of course, is to describe the hardware of a microwave system and, ultimately, complete systems incorporating digital, low frequency analog and microwave components.

A typical design scenario breaks the total system to be built into several interconnected subsystem, a hierarchy, each with its own specifications and schedules, as shown in Figure 3 applied to a simplified radar system. The design task for each subsystem or level of the hierarchy then possibly may be passed to different internal organizations and/or outside vendors. Of course, if any of the subsystem goals can not be met, changes then must be reflected to the original system specification. Not only are electrical performance specifications being considered, but also other aspects, including size, weight, schedule and reliability. Aspects to be included are defined in the requirements phase of the MHDL program. At any point in this communication, not all information may be available. For example, only design specifications for a particular block may be set, prior to hardware design. This shows the need that MHDL allow particular information.

It should be emphasize that the boundary between what is called a system or a subsystem is not relevant to MHDL. These distinctions are made by the user. The example in Figure 3 illustrates a top-down design approach, but MHDL will also embody a bottom-up design procedure. MHDL will not force a design procedure upon the user, but will encourage a more complete and unambiguous description of microwave hardware.

MHDL also will enhance microwave and analog simulation capabilities. By allowing description of microwave hardware in a common language, users will be able to compare and utilize components easily from several sources. For example, component houses will be able to disseminate their technology and system houses will be able to incorporate newer technology. MHDL will be a catalyst in enabling CAD tools from various vendors to interoperate. It is very difficult to utilize system level tools from one vendor and to use circuit level analysis results from another.

The MHDL Program

The MIMIC program's primary goal is to facilitate the insertion of MMICs into systems. In accomplishing this goal, however, a set of secondary requirements has resulted. It has been recognized that a standardized mechanism to transfer information between system houses and component designers was required. This information exchange is required for analog and digital circuit fabrication. [1]

The DARPA-sponsored MHDL program, which is part of the MIMIC Phase 3 program, formally began on November 15, 1990. The program is organized into four phases, including language requirements, language definition, demonstration, and standardization and support. Phase 0, the nine-month requirements phase, establishes microwave requirements for the language developer. Some requirements for MHDL are supporting the complete design and documentation of microwave hardware in a standardized format; allowing circuit and system descriptions, including statistical information; in addition to hardware description, allowing performance specification and features related to project budgeting and scheduling; enhancing communication among designers working at different levels of abstraction; including measurement and test data for performance verification and validation; communicating design data between vendors for second sourcing and design specifications between users and vendors to aid the acquisition process; and allowing the description of electrical behavior, independent of circuit realizations, in order to enhance the ability to second source, increase reusability and improve system maintainability.

The language definition phase, Phase 1, will begin in July ,1991. In this phase, the requirements established by the users in Phase 0 will be captured in a software language. The resulting document will be a language reference manual (LRM), which will be reviewed by the users to make certain that the requirements defined in Phase 0 are met.

In order to show the utility of MHDL and demonstrate its capabilities, CAD tools will be developed in Phase 2. The tools will be used to realize the scenarios provided in the Phase 0 effort.

Support for standardization and language validation efforts will be accomplished in Phase 3. The effort under this phase is to support the transfer of MHDL to a standardization body and the associated procedures to make MHDL a industry standard.


The MIMIC hardware description language is a reality and has already had some successes, such as the full cooperation of industry and the diversity of participants in the MHDL Working Group. The success of this effort is proportional to industry involvement. It is important to establish an industrial base for exchange of information. Participation by the microwave community is encourage to help establish MHDL requirements.

Companies and their engineers interested in participating in the MHDL Working Group should contact the MHDL Progra Office via electronic mail, or at MHDL Program Office, US Army LABCOM ETDL, SLCET-MP, Ft. Monmouth, NJ.


[1] Electronic Engineering Times, "Components-Data Gap Hampers EDA Activity," February 4, 1991.

(*) Invited paper
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Title Annotation:microwave circuit hardware description language
Author:Carmichael, L.; Perlman, B.; Rhodes, D.
Publication:Microwave Journal
Date:Apr 1, 1991
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