Vasily Ivanenko on Vladimir Polyakov's Subharmonic Detector

Our old friend "Vasily" sent in a very insightful comment about the Polyakov receiver.   It was so good that it merits a blog post of its own.  Here it is.  Thanks Vasily! 

Vasily IvanenkoAugust 9, 2022 at 12:49 AM

Thanks Bill. My own experiments at HF with subharmonically pumped Schottky diode mixers show clearly that almost every mixer parameter we measure is worse than our classic balanced mixer topologies. Definitely 2LO-RF isolation was better than other unbalanced mixers without the need for a transformer.

I guess it's appealing for low-complexity receiver builders. For zero IF receivers, I like and run my LO at 1/2 RF frequency and then use a doubler -- that's a great advantage for
a DC/ Zero-IF receiver and a built-in feature for the subharmonic mixer.

The SH mixer becomes quite appealing at SHF to mm-wave lengths where making a quiet, temp stable LO gets rather expensive and tricky.

Subharmonically pumped mixers can also work at odd integers if the mixer LO/RF drive is balanced and designed to produce distortion that for example, triples the LO frequency. Rohde & Schwarz had a 40.1 GHz spectrum analyzer with one --- and if the LO was 13 GHz while the RF was 39.5 GHz, this gave an IF output of 500 MHz in 1 particular circuit. Really amazing design work. Here's an interesting URL:

https://www.eravant.com/products/mixers/subharmonically-pumped-mixers

The SH mixer has been around for > 4 decades. The oldest SH mixer paper I've got in my library is from Schneider and Snell from 1975. I don't think they invented the SH, but this pair helped popularize it for the world and design work continues today.I've seen optical SH mixers with I/Q outputs in research papers.

Here's the abstract and citation:

Harmonically Pumped Stripline Down-Converter

M. V. Schneider, W. W. Snell
Published 1 March 1975
Physics, Engineering
IEEE Transactions on Microwave Theory and Techniques

A novel thin-film down-converter which is pumped at a submultiple of the local-oscillator frequency has given a conversion loss which is comparable to the performance of conventional balanced mixers. The converter consists of two stripline filters and two Schottky-barrier diodes which are shunt mounted in a strip transmission line. The conversion loss measured at a signal frequency of 3.5 GHz is 3.2 dB for a pump frequency of 1.7 GHz and 4.9 dB for a pump frequency of 0.85 GHz. The circuit looks attractive for use at millimeter-wave frequencies where stable pump sources with low FM noise are not readily available.

Best to you!