New-Tech Europe Magazine | April 2017

Test & Measurement Special Edition

Reflectionless Filters Improve System IP3 in Up-converter and Down-converter Configurations

Martina Yan, Mini-Circuits

Since the market release of Mini- Circuits’ X-Series reflectionless filters, much testing has been conducted to evaluatethe benefits of these revolutionary products in comparison to conventional filters. While conventional filters are fully reflective in the stopband, reflectionless filters use a novel, patented filter topology to absorb and terminate stopband signals internally, avoiding many known systemic problems caused by reflections in the signal chain. This new capability makes reflectionless filters suitable for a variety of applications beyond those typically incorporating conventional filters. One of the most prevalent and practical of these applications is filtering at mixer inputs and outputs. Previous testing, which Mini-

Circuits has published, established that reflectionless filters virtually eliminate signal reflections between the filter and the mixer output as compared to conventional filters.The expected effect of this reduction is an overall improvement is system linearity and dynamic range, but this was inferred in previous reports. This article will present new test results demonstrating overall improvement in system IP3 when reflectionless filters are used on mixer inputs and outputs in both downconverter and upconverter configurations in comparison to conventional lumped element filters and LTCC filters. The results also expand on previous comparisons by testing numerous mixer-filter combinations and showing consistent

performance improvement when reflectionless filters are used. Up-Conversion Test Setup Two-tone intermodulation tests were performed in up-converter configuration using diode based mixers with a variety of filters on the IF input and RF output ports for comparison. The test was also performed without filters to provide a reference.Third order intermodulation measurements were made withIF input of 150 MHz and two-tone spacing of 1 MHz, and RF outputs of 800 MHz and 2200 MHz. The test setup is illustrated in Figure 1, and the test conditions are summarized in Table 1. Each of the two mixers was tested

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