Use of a preselection filter bank and switched local oscillator counter in an instrumentation receiver

Abstract

An instrumentation receiver architecture for processing an RF signal has a dual-IF channel architecture, a low-band IF channel and a high-band IF channel, and a tunable oscillator, such as a yttrium-iron-garnet (YIG) tunable oscillator (YTO), a voltage controlled oscillator (VCO), a bank of VCOs and the like, providing a different mixing frequency range to each channel, generally a higher frequency range to the high-band IF channel than to the low-band IF channel. At the input to the high-band IF channel is a bank of preselection filters for selecting a frequency band from the RF signal for processing by the high-band IF channel. A switch selects the output from one of the low-band and high-band IF channels for further processing.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to spectrum analysis, and more particularly to an instrumentation receiver using a preselection filter bank and a switched local oscillator counter. [0002] A known instrumentation receiver described in U.S. Pat. No. 6,316,928 incorporates a yttrium-iron-garnet (YIG) tuned oscillator (YTO) as a sweep frequency local oscillator and a YIG tuned filter (YTF) as a frequency preselector for an incoming RF signal. The YTF is used to remove image products in a high frequency band before a first conversion stage. However the YTF has the disadvantages of high cost and limited bandwidth. The architecture disclosed in the '928 patent is a dual-IF architecture having a baseband IF channel and a high-band IF channel both using the same YTO. The baseband IF channel upconverts the RF signal to a first IF frequency, bandpass filters the first IF frequency and downconverts to a second IF frequency. The high-band IF channel preselects a ...

AI Technical Summary

Benefits of technology

[0004] Accordingly the present invention provides an instrumentation receiver architecture for processing an RF signal that has a dual-IF channel architecture, a low-band IF channel and a high-band IF channel, that includes a bank of preselection filters at the input of the high-band IF channel to select a frequency band from the RF signal for processing by the high-band IF channel. A common tunable oscillator, such as an yttrium-iron-garnet (YIG) tunable oscillator (YTO), a voltage controlled oscillator (VCO), a bank of VCOs, or the like, is used to provide a different first stage mixing frequency range to both IF channels, the frequency range applied to the high-band IF channel generally being higher than that applied to the low-band channel. In a first implementation the low-band IF channel up-converts a lowpass filtered RF signal to an first IF signal and then down-converts the first IF signal to a second IF signal, while the high-band IF channel down converts the selected frequency band of the RF signal to the second IF signal. The output from the selected one of the IF channels is digitized for processing by a digital signal processor (DSP). In a second implementation the outputs from the first stage conversion in each IF channel, having different IF frequencies, are selectively input to a configurable down conversion stage which converts the outputs from the respective first stages to a common IF frequency for further processing. In a third implementation the low-band IF channel also contains a bank of preselection filters so that the input to the first stage is either the lowpass filtered RF signal or a selected frequency band from the RF signal, with the first stage acting as an up-converter when the input is the lowpass filtered RF signal and as a down-converter when the input is the selected frequency band. The output from the first stages are input to the configurable down conversion stage as in the second implementation.

Problems solved by technology

However the YTF has the disadvantages of high cost and limited bandwidth.

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