| EPSRC Reference: |
GR/H78535/01 |
| Title: |
A NEW CLASS OF ACTIVE FILTER FOR MONOLITHIC MICROWAVE INTEGRATED CIRCUITS |
| Principal Investigator: |
Robertson, Professor I |
| Other Investigators: |
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| Department: |
Electronic Engineering |
| Organisation: |
Kings College London |
| Scheme: |
Standard Research (Pre-FEC) |
| Starts: |
01 May 1993 |
Ends: |
30 April 1995 |
Value (£): |
74,921
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| EPSRC Research Topic Classifications: |
| RF & Microwave Technology |
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Summary on Grant Application Form |
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The aim of this program is to establish the theory and design techniques for new classes of monolithic active microwave filter, with very high selectivity for communications applications. The proposed programme is to investigate new active inductor and resonator cells, and their application to band-pass microwave filters. The techniques are being investigated using theoretical analyses, computer simulations, and prototype resonator and filter measurements. Progress:This project has investigated three key techniques for the realisation of MMIC active filters for microwave applications. The measured performance of two of these MMIC active filters has led to results of the highest standards at the international level. Active Inductor Based FilterWe have employed a modified cascode active inductor topology which has been found to achieve negative resistance. This has been achieved by employing an active load and a FET as the feedback element. The Q-factor is over 15000. The active inductor has been used to design a bandpass filter. In practice, series resistance values of approximately -6W were used to overcome the overall losses in the MMIC filter. The measured response shows extremely high selectivity, with 0 dB insertion loss in the 100 MHz passband centred at2 GHz. The out-of-band response is exceptionally good, with no major transmission bands all the way up to 30 GHz. Filter Using A Novel Negative Resistance CircuitThe drawback of the active inductor filter is that the large number of FETs leads to high DC power consumption and demands the application of many bias voltages. The use of a simple single-FET negative resistance circuit has been extended to the realisation of active lossless resonators for use in fully monolithic filters with high selectivity. A three resonator filter was chosen to demonstrate the new technique. The measured response shows it operates at 2.3 GHz centre frequency with 120 MHz 3 dB bandwidth, with 0 dB insertion loss and less than 0.1 dB ripple in the passband. The out-of-band rejection is as high as 100 dB at low frequencies and is over 50 dB up to6 GHz. Furthermore, even up to 20 GHz there are no significant spurious transmission bands. ConclusionsThe advantages and disadvantages of active filters for MMIC transceivers have been investigated and two state-of-the-art designs have been realised using the GEC-Marconi GaAs foundry. The next phase is to investigate the practical application of these filters: Can they be made sufficiently stable and resilient to environmental changes (e.g. temperature)? This is a major task in its own right. The European Space Agency and Matra Marconi Space UK have expressed an interest in supporting this next phase with provision of test fixtures and facilities. Publications so far:1 IEEE Transactions (MTT); 6 papers at major international conferences; 4 papers at UK conferences/colloquia; 2 further journal papers submitted.
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Key Findings |
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Potential use in non-academic contexts |
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Impacts |
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| Description |
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk |
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Sectors submitted by the Researcher |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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