1. Technical Field
The present invention relates to spectrum analyzers, and in particular to a frequency extension module for microwave and millimeter wave spectrum analyzers.
2. Related Art
Spectrum analyzers are well-known tools which can be used, among other functionality, to determine the composition of various input signals and waveforms. These analyzers can be provided in a variety of form factors from large, stand alone lab equipment to relatively compact portable devices. Spectrum analyzers generally offer a limited bandwidth over which they are operable to analyze input signals.
In accordance with an embodiment, an apparatus for analyzing signals, comprises a spectrum analyzer and a frequency extension module coupled to the spectrum analyzer. The spectrum analyzer includes an IF switch which switches between an internal IF signal, generated at the spectrum analyzer, and an external IF signal, and a LO coupler which is configured to output a portion of one or more LO signals generated at the spectrum analyzer. The frequency extension module is configured to receive one or more LO signals from the spectrum analyzer and send an IF signal to the spectrum analyzer. The frequency extension module includes an RF input port operable to receive high band and low band signals, a diplexer band switch which directs the high band signals to the frequency extension module and directs the low band signals to the spectrum analyzer, an IF output port which sends an IF signal to the spectrum analyzer at the IF switch, and a LO input port which receives at least one LO signal from the LO coupler at the spectrum analyzer.
Further details of the present invention are explained with the help of the attached drawings in which:
Embodiments of the present invention relate to circuitry and modules which extend the frequency range of a spectrum analyzer. In accordance with an embodiment, a frequency extension module can be internally added to a spectrum analyzer system. The extension module can extend the RF input operating range of the analyzer from the standard low band frequency range to an extended frequency range. Additionally, a digitally controlled diplexer band switch can be used to enable the spectrum analyzer to function over the low band frequency range and over the extended frequency range during each sweep.
In accordance with an embodiment, an apparatus for analyzing signals, comprises a spectrum analyzer and a frequency extension module coupled to the spectrum analyzer. The spectrum analyzer includes an IF switch which switches between an internal IF signal, generated at the spectrum analyzer, and an external IF signal, and a LO coupler which is configured to output a portion of one or more LO signals generated at the spectrum analyzer. The frequency extension module is configured to receive one or more LO signals from the spectrum analyzer and send an IF signal to the spectrum analyzer. The frequency extension module includes an RF input port operable to receive high band and low band signals, a diplexer band switch which directs the high band signals to the frequency extension module and directs the low band signals to the spectrum analyzer, an IF output port which sends an IF signal to the spectrum analyzer at the IF switch, and a LO input port which receives at least one LO signal from the LO coupler at the spectrum analyzer.
The spectrum analyzer can provide a plurality of LO signals, such as LO1 310 and LO2 312. These LO signals can be passed through frequency multipliers and/or dividers to provide additional signals. For example, in
In accordance with an embodiment, and as shown in
In accordance with an embodiment, the spectrum analyzer can also provide IF path switching using IF switch 336. When processing the non-extended frequency band, the spectrum analyzer can use one of its mixer output IFs, such as the output from mixer 324. The extension module's IF output 346 can be selectively switched-in while the module is down-converting the extended frequency band(s). For example, the spectrum analyzer may be operable over the band 9 KHz up to 20 GHz and the frequency extension module may be configured to extend the operable range of 20 GHz to 43 GHz. Thus, for low band input signals in the unextended band between 9 KHz and 20 GHz, the diplexer band switch will send the low band input signals to the spectrum analyzer front end, where they will be processed and the IF generated at the spectrum analyzer is used. Similarly, for high band input signals the diplexer band switch sends the high band input signals to the frequency extension module and the IF generated at the frequency extension module is used. Although specific frequency bands such as these are described, this is merely for simplicity of explanation, other operable frequency ranges and extensible frequency ranges are similarly possible.
In accordance with an embodiment, the extension module is controlled by the system microcontroller processor (hereafter referred to as the microcontroller). The microcontroller can enable selection of RF receive and LO filters. Additionally, the microcontroller can control diplexer band switching, RF preamplifier switching, and power supplies, as well as allow for temporary disconnection of transmission paths within the module to avoid leakage and spurious signals. The RF preamps can be bypassed for high level operation, or they can be switched in to provide a lower noise figure. Additionally, LO power can be switched to more than one mixer.
In accordance with an embodiment, testability can be improved by switching in test monitor ports. The generation of spurious signals within the extension module can be minimized by temporarily disconnecting LO power from one or more of the mixers, without turning the spectrum analyzer off. Thus, when the frequency extension module is idle, the spectrum analyzer can continue to function without the risk of generating spurious signals.
As shown in
As described above, and in accordance with an embodiment, the frequency extension module extends the operating range of the spectrum analyzer to which it is paired. However, the spectrum analyzer does not need the frequency extension module in place to function over its original low band operating range. The extension module uses high performance circuit construction suitable for higher frequencies including the millimeter range. The module provides a mounting environment for monolithic microwave integrated circuits (MMICs) and thin film circuitry. LO multiplication, LO filtering, multiple mixer channels, RF image rejection filtering, RF preamps, and a diplexer band switch can also be provided inside the module.
In accordance with an embodiment, the diplexer band switch provides low distortion signal routing of high band and low band signals, while limiting signal leakage between the high band and the low band. High band signals can be switched into the extension module for frequency down conversion. The low band can be switched into the main spectrum analyzer's front end for non-extended frequency range processing when the module is not needed for conversion. The low leakage feature of the diplexer keeps the high band signal from leaking out the low band diplexer port, thus avoiding high band amplitude ripple.
In accordance with an embodiment, the diplexer band switch can include a plurality of PIN diodes arranged in a distributed manner along a low band output low pass filter. The PIN diodes parasitic inductance can be made to resonate with the capacitors upon which they mount at several frequencies across the high band. This puts multiple transmission zeros at high band frequencies along the low band path during high band operation (e.g., when the module is not idle). This can reduce high band leakage through the low band port which otherwise would cause amplitude ripple in the high band. Without leakage suppression, a standing wave between the band switch low band output and lowband spectrum analyzer input would exist. This standing wave can cause high band ripple during high band down-conversion.
In accordance with an embodiment, the frequency extension module can be comprised of multiple smaller modules interconnected using blindmate connectors. The result is a small integrated frequency extension module with robust manufacturability using high yield assembly processes. Additionally, the frequency extension module can provide frequency multiplication and LO amplification, which allows for the use of fundamental mixers. This keeps the conversion loss and the noise figures low when compared to the use of harmonic mixers of prior art spectrum analyzers. In accordance with an embodiment, the frequency extension module can take on other forms of construction including one or more sub-modules supporting chip and wire assembly. It could also be comprised of soft board planar assembly or waveguide designs.
In accordance with an embodiment, the frequency extension module's LO input frequency can be multiplied one or more times to achieve the final desired LO frequency to drive the mixers. The frequency extension module can include a plurality of mixers used to support the bandwidth, and the mixers can be fundamental or harmonic. Image reject mixers can also be used if 90 degree hybrids are provided. The electronics of the module can also be provided by an integrated chipset including MMICS and MIMS. If more than one module is used they can be integrated using blindmate RF connections or they could also be connected by other transmission lines such as coaxial cables. Alternatively, multiple carriers containing the electronics can be integrated together into a single housing.
Although the present invention has been described above with particularity, this was merely to teach one of ordinary skill in the art how to make and use the invention. Many additional modifications will fall within the scope of the invention, as that scope is defined by the following claims.
Number | Name | Date | Kind |
---|---|---|---|
3325731 | Headle, Jr. | Jun 1967 | A |
3366877 | Kinkel et al. | Jan 1968 | A |
3581192 | Miura et al. | May 1971 | A |
4054785 | Lehmann | Oct 1977 | A |
4321680 | Bertrand et al. | Mar 1982 | A |
4504785 | Tucker et al. | Mar 1985 | A |
4578638 | Takano et al. | Mar 1986 | A |
4636717 | Sharrit et al. | Jan 1987 | A |
4641085 | Donecker et al. | Feb 1987 | A |
4641086 | Barr et al. | Feb 1987 | A |
4644486 | Cannon et al. | Feb 1987 | A |
4661767 | Sharrit et al. | Apr 1987 | A |
4720673 | Hatfield | Jan 1988 | A |
4816767 | Cannon et al. | Mar 1989 | A |
4896102 | DuBois | Jan 1990 | A |
5038097 | Imanaka | Aug 1991 | A |
5262957 | Hearn | Nov 1993 | A |
6140809 | Doi | Oct 2000 | A |
6233529 | Nonaka | May 2001 | B1 |
7002335 | Shoulders | Feb 2006 | B2 |
7061222 | Shank et al. | Jun 2006 | B2 |
7746052 | Noujeim | Jun 2010 | B2 |
8159208 | Brown et al. | Apr 2012 | B2 |
8179118 | Bernard | May 2012 | B2 |
8514919 | Estrada et al. | Aug 2013 | B2 |
20020097036 | Bradley | Jul 2002 | A1 |
20030080724 | Mar | May 2003 | A1 |
20050258815 | Shoulders | Nov 2005 | A1 |
20060206550 | Uchino | Sep 2006 | A1 |
20070052406 | Payne | Mar 2007 | A1 |
20070286269 | Hill et al. | Dec 2007 | A1 |
20080238405 | Marshall et al. | Oct 2008 | A1 |
20080258706 | Bernard | Oct 2008 | A1 |
20080258707 | Dunsmore et al. | Oct 2008 | A1 |
20090045798 | Heah et al. | Feb 2009 | A1 |
20090160430 | Brown et al. | Jun 2009 | A1 |
20100052652 | Mitchell et al. | Mar 2010 | A1 |
20100094577 | Nose et al. | Apr 2010 | A1 |
20100156438 | Gorin et al. | Jun 2010 | A1 |
20100272166 | Nara | Oct 2010 | A1 |
20110117869 | Woodings | May 2011 | A1 |
20110202316 | Crooks | Aug 2011 | A1 |
20110304318 | Noujeim et al. | Dec 2011 | A1 |
20120256616 | Brown et al. | Oct 2012 | A1 |
20120269252 | Ward | Oct 2012 | A1 |
Entry |
---|
Dvorak et al. “Extension of an absolute vector error correction technique to wideband, high-frequency measurements”, IET Sci. Meas. Technol., 2009, vol. 3, No. 1, pp. 59-71. |